Iowa State University
Self-Guided Wheelchair
MAY07-15
Design Report
Version 2.0
Client: Andrew Dove
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Faculty Advisors: Dr. Nicola Elia
Team Members: Tara Spoden
Brian Yauk
Margaret Shangle
Vee Shinatrakool
John Volkens
DISCLAIMER: This document was developed as a part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. This document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator.
Submitted: Wednesday, December 6, 2006
Table of Contents
1 List of Figures iii
2 List of Tables iv
3 List of Definitions vi
4 Executive Summary 1
5 Introductory Materials 2
5.1 Acknowledgement 2
5.2 Problem Statement 2
5.2.1 General Problem Statement 2
5.2.2 General Solution Approach 2
5.3 Operating Environment 3
5.4 Intended Users and Uses 3
5.4.1 Users 3
5.4.2 Uses 4
5.5 Assumptions and Limitations 4
5.5.1 Assumptions 4
5.5.2 Limitations 5
5.6 Expected End Product and Other Deliverables 6
6 Proposed Approach 8
6.1 Design Objectives 8
6.2 Functional Requirements 9
6.3 Constraint Considerations 9
6.4 Technology Considerations 9
6.4.1 Selection Criteria 11
6.4.2 Microprocessor Hardware 11
6.4.2.1 Technology Considerations 12
6.4.2.2 Selected Approach 16
6.4.3 Microprocessor Software 16
6.4.4 Ranging Modules 16
6.4.4.1 Technology Considerations 16
6.4.4.2 Selected Approach 20
6.4.5 Orientation Sensors 21
6.4.5.1 Technology Considerations 21
6.4.5.2 Selected Approach 22
6.4.6 Distance Tracking Sensors 22
6.4.6.1 Technology Considerations 23
6.4.6.2 Selected Approach 23
6.4.7 Localization 23
6.4.7.1 Technology Considerations 24
6.4.7.2 Selected Approach 28
6.4.8 Motor Control 28
6.4.8.1 Technology Considerations 29
6.4.8.2 Selected Approach 31
6.4.9 Power Management 32
6.4.9.1 Technology Considerations 32
6.4.9.2 Selected Approach 33
6.4.10 User Interface 33
6.4.10.1 Technology Considerations 33
6.4.10.2 Selected Approach 37
6.5 Testing Requirements 38
6.5.1 Microprocessor 38
6.5.1.1 Hardware 38
6.5.1.2 Software 38
6.5.2 Sensors 38
6.5.2.1 Ranging Module 39
6.5.2.2 Orientation 39
6.5.3 Localization 39
6.5.4 Motor Control 40
6.5.5 Power Management 40
6.5.6 User Interface 41
6.5.7 System Integration 41
6.6 Project Continuation 42
6.7 Detailed Design 42
6.7.1 General Overview 42
6.7.2 Microprocessor 44
6.7.2.1 Hardware 44
6.7.2.2 Software 45
6.7.3 Sensors 48
6.7.3.1 Ranging Module 48
6.7.3.2 Orientation 51
6.7.4 Localization 53
6.7.5 Motor Control 56
6.7.6 Power Management 58
6.7.7 User Interface 60
6.7.8 Design Summary 61
7 Estimated Resource Requirement 62
7.1 Personnel Requirements 62
7.2 Other Resources 64
7.3 Financial Requirements 64
8 Schedules 66
9 Project Team Information 69
10 Closing Summary 70
11 Appendix A 71
12 Appendix B 73
13 Appendix C 74
14 Appendix D 76
15 References 78
List of Figures
List of Figures
Figure 5.1 – Basic System Block Diagram 3
Figure 6.1 – Technology Selection Process 10
Figure 6.2 – System Flow Diagram 43
Figure 6.3 – Wheelchair System Diagram 43
Figure 6.4 – System Mounting Diagram 44
Figure 6.5 – Controller Connection Block Diagram 44
Figure 6.6 – General Program Flow 46
Figure 6.7 – SRF04 Timing Diagram 49
Figure 6.8 – SRF04 Beam Pattern 49
Figure 6.9 – Ranging Module Mounting Arrangement 50
Figure 6.10 – Ranging Module Mapping in a Hallway 51
Figure 6.11 – R117 Compass Timing Diagram 52
Figure 6.12 – RFID Tag Placement 53
Figure 6.13 – APSX RW-310 RFID Reader/Writer Module and Transponders 54
Figure 6.14 – Computer to RFID Reader 55
Figure 6.15 – Invacare Arrow Joystick Schematic 56
Figure 6.16 – Controller to Joystick Connection Diagram 57
Figure 6.17 – 5VDC System 58
Figure 6.18 – 9VDC System 58
Figure 6.19 – 6VDC to 5VDC 59
Figure 6.20 – LCD Character Displays 61
Figure 8.1 – Fall 2006 Task Schedule (Original) 66
Figure 8.2 – Fall 2006 Task Schedule (Revised) 66
Figure 8.3 – Spring 2007 Task Schedule (Original) 67
Figure 8.4 – Spring 2007 Task Schedule (Revised) 67
Figure 8.5 – Full Project Reporting and Deliverables Schedule (Original) 67
Figure 8.6 – Full Project Reporting and Deliverables Schedule (Revised) 68
List of Tables
List of Tables
Table 5.1 – Project Assumptions 4
Table 5.2 – Prototype Assumptions 5
Table 5.3 – Project Limitations 6
Table 6.1 – CMD565 Evaluation Board 12
Table 6.2 – Handy Board 13
Table 6.3 – EPIC AMD Gode GX2 14
Table 6.4 – VIA EPIA-EN12000EG Mini-ITX 15
Table 6.5 – Controller Technology Comparison 16
Table 6.6 – SRF04 Sonar Sensor 17
Table 6.7 – SRF235 Sonar Sensor 17
Table 6.8 – SensComp 6500 Sonar Sensor 18
Table 6.9 – Sharp GP2D05 IR Ranger 18
Table 6.10 – Sharp GP2Y0A02YK IR Sensor 19
Table 6.11 – R283-HOKUYO Laser Sensor 20
Table 6.12 – Ranging Module Technology Comparison 20
Table 6.13 – Devantech R117 Magnetic Compass 21
Table 6.14 – ADXRS150 Angular Rate Sensor 22
Table 6.15 – Orientation Technology Comparison 22
Table 6.16 – MA2 Miniature Absolute Magnetic Shaft Encoder 23
Table 6.17 – Distance Tracking Technology Comparison 23
Table 6.18 – Off-board Track Localization 24
Table 6.19 – Dead Reckoning Localization 26
Table 6.20 – Tactile Detection Localization 26
Table 6.21 – RFID Localizatoin 27
Table 6.22 – Sonar Imaging Localization 27
Table 6.23 – Localization Technology Comparison 28
Table 6.24 – ADAC0808 8-Bit D/A Converter 30
Table 6.25 – Custom D/A Converters 30
Table 6.26 – Control Box Connection 31
Table 6.27 – Joystick Connection 31
Table 6.28 – Motor Control Technology Comparison 32
Table 6.29 – Trident GPA 400 PIN Keypad 34
Table 6.30 – Targus USB Numeric 19-Key Mini Kepad 34
Table 6.31 – Kensington Pocket Keypad 35
Table 6.32 – Phidget Text LCD 36
Table 6.33 – Mini-Box picoLCD 36
Table 6.34 – Optrex TM1B5BW Touchscreen 37
Table 6.35 – User Interface Technology Comparison 37
Table 6.36 – Wheelchair Testing Form 40
Table 6.37 – EPIA-EN12000EG Mini-ITX Features 45
Table 6.38 – SRF04 Technical Specifications 48
Table 6.39 – SRF04 Pin Connections 48
Table 6.40 – R117 Compass Technical Specifications 51
Table 6.41 – R117 Compass Pin Connections 52
Table 6.42 – ADXRS150 Gyroscope Technical Specifications 53
Table 6.43 – RW-310 RFID Reader/Write Module Features 55
Table 6.44 – Digital Output Mapping to Motor Control (Forward/Reverse) 57
Table 6.45 – Digital Output Mapping to Motor Control (Left/Right) 58
Table 6.46 – 9V Energizer Battery Specifications 59
Table 6.47 – AA Energizer Battery Specifications 60
Table 6.48 – Evaluation of Design Functionality 61
Table 7.1 – Estimated Person Hours (Original) 62
Table 7.2 – Estimated Person Hours (Revised) 63
Table 7.3 – Other Resource Requirements 64
Table 7.4 – Material and Labor Costs (Original) 64
Table 7.5 – Material and Labor Costs (Revised) 65
List of Definitions
List of Definitions
CPU (central processing unit) programmable logic device that performs all the instruction, logic, and mathematical processing in a computer
DAC or D/A (digital to analog converter) electronic device that is used to convert digital signals into analog signals
DC (direct current) unlike alternating current (AC), the flow of current is constant in one direction
EEPROM (electrically erasable programmable read only memory) rewriteable form of memory that is non-volatile, meaning that the device does not need a supply of power in order to retain the memory
Infrared electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum, from 760 nanometers to 1000 microns
LabVIEW Embedded graphical programming language developed by National Instruments for implementation on OEM hardware
LCD (liquid crystal display) display that consists of two polarizing transparent panels and a liquid crystal surface sandwiched in between
Microprocessor silicon chip with thousands of electronic components that serves as the CPU in microcomputers
OEM (original equipment manufacturer) original manufacturer of a hardware component or sub-component
PWM (pulse width modulator) type of circuit that holds the frequency constant while the width of power pulse is varied, and controls both line and load changes without major dissipation
RF (radio frequency) frequency that lies in the range within which radio waves may be transmitted, from about 10 kilohertz per second to about 300,000 megahertz.
Sonar (sound navigation and ranging) distances to objects are determined by bouncing sound waves off them and measuring the time it takes for the echo to return
Transponder radio transmitter-receiver activated for transmission by reception of a predetermined signal. An RF reader/transmitter sends a signal via radio waves in order to detect transponders designed to read that reader’s particular frequency signal.
USB (universal serial bus) external peripheral interface standard for communication between a computer and external peripherals over a cable using bi-serial transmission
VI (virtual instrument) file containing subroutines or subfunctions created in LabVIEW
Executive Summary
Executive Summary
The system designed in this project is a wheelchair that has the ability to navigate autonomously through a hospital environment while avoiding obstacles incurred along the desired route. Certain limitations, constraints outside of the control of the team, and assumptions, constraints defined by the team, have been identified in order to ensure a manageable project. These considerations include constraints on the operating environment such as floor surface, the physical and mental capabilities of the user, budget, physical dimensions, power requirements, and overall scope of the project. Functional requirements further define the autonomous navigation and obstacle avoidance in terms of navigation from and to predefined locations, recalculating routes in instances of impassible obstacles, continuing navigation on reasonably shallow ramps.
A floorplan map modeled after the actual environment will be programmed into the Mini-itx controller prior to operation. Within this map, several predetermined coordinates will be selected as the possible waypoints to be used as the start and destination points. Also included in this map, will the location of waypoints intended for localization purposes. The MPC565 will be programmed using LabVIEW Embedded 8.2 as requested by the client, National Instruments.
Operation will begin with user input of the wheelchair’s current location as the starting point and the desired destination as the ending point. Using a keypad with unique keys for each of the possible waypoints and an LCD display, the user will select the start and end point of the wheelchair navigation. A keypad and LCD were chosen as the best options for user interface because they are inexpensive and easily interfaced with the evaluation board.
An algorithm for path calculation will begin upon receipt of the starting and ending point of navigation. The path will be generated from the initial floorplan, assuming only preprogrammed obstacles. During travel, additional obstacles may be added into the map when detected. Using multiple ultrasonic sensors positioned around the perimeter of the wheelchair, the distance from the wheelchair to physical objects in the environment will be calculated from the sensor feedback. The distances will be used in the microprocessor to decide which directions are safe for travel and free of obstructions. This method for object detection was chosen because the ultrasonic sensors offer the necessary range of obstacle detection for a reasonable price.
In addition to the information from the ultrasonic sensors, the microprocessor will receive data from a compass and gyroscope in order to track the trajectory of the wheelchair. As data from the ultrasonic sensors arrive and the initial path is determined to be obstructed, the additional sensors will allow for calculating the deviation from the original path. An educated estimate of the current location can then be constructed for use during path recalculation. This collection of sensors was decided upon based on their ability to provide the necessary accuracy for this project and due to the fact that a gyroscope was incompatible with the operation of system, specifically wheel slippage.
The localization technology to be implemented in the system is a fixed beacon method based on RFID. A reader will be connected into the system which will identify RFID tags that have been strategically placed through the operating environment. This method of localization was chosen because of its cost-effectiveness compared to other localization technologies.
The motor control of the wheelchair will be realized by converting the digital output of the controller into an analog signal which can be sent into the existing joystick. This method for was deemed acceptable for the prototype design as technical information on the motor control box was unavailable from the manufacturer.
The end-product of this project will be a physical prototype which will demonstrate basic navigational capabilities. Due to the complexity and scale of this project, the tasks have been divided into smaller, manageable sections of planning, development, testing and documentation. A schedule has been constructed with milestones signifying the conclusion of each section to ensure successful completion within the two semester timeframe of senior design. The resource requirements and expected team member hourly contributions were included in the development of this schedule.
Introduction
Introductory Materials
The following material gives an overall summary of current problematic situation, as well as an overview of the proposed system solution, complete with expected deliverables of the project.
1 Acknowledgement
The May07-15 Design Team would like to thank several resources for information and materials in relation to this project: National Instruments for their donation of LabVIEW Embedded 8.2 software, the CMD565 evaluation board and microprocessor, as well as, advanced technical support; Invacare for their donation of a joystick and wheelchair control box; and Iowa State University for the use of a motorized wheelchair for the duration of the project.
2 Problem Statement
The section addresses and outlines the general solution approach.
1 General Problem Statement
Many people encounter an instance in their life where a disability causes them to be confined to a wheelchair. When transport is required, the wheelchair is often physically manned, either by the person in the wheelchair or someone behind it. When someone is needed to push the wheelchair, the independence of the person confined to the wheelchair is limited to the schedule and convenience of an outside source.
Especially in hospital environments, these persons confined to wheelchairs need to move frequently, for appointments in multiple departments and general relocation from room to room. In the absence of family and friends, the assistance required for persons in wheelchairs creates a burden on the already confined schedules of the staff. As a result, patients are subject to waiting until aid is of convenience.
2 General Solution Approach
The system proposed for this project is a wheelchair that has the ability to navigate autonomously through a hospital while avoiding obstacles. Using a microprocessor programmed with LabVIEW Embedded 8.2 and interfaced with user input devices, the wheelchair user will be able to select, from one of several locations, their starting and ending point.
Travel of a motorized wheelchair will be initiated and controlled by the microprocessor. Positioning sensors will interface with the microprocessor to indicate location and distance traveled. During travel, additional sensors mounted on the wheelchair will transmit environmental data such as distance to surround objects to the microprocessor. Incurred obstacles will prompt an obstacle avoidance algorithm to attempt to navigate around the obstacle and recalculate paths.
The block diagram in Figure 5.1 demonstrates the basic system solution interface.
[pic]
Figure 5.1 – Basic System Block Diagram
3 Operating Environment
The system will be designed for use in an indoor medical hospital setting. The prototype to be designed during the project will be designed only for operation on a single floor level, free of stairs or similar large drop-offs. The floor surface should be a common hospital floor type, such as tile, hardwood, or short carpet. The environment should be typically for motorized wheelchair operation and yield itself to a mobile wheelchair system.
4 Intended Users and Uses
The system is designed to accommodate the users and uses outlined in the following sections.
1 Users
There are two possible classes of users for this wheelchair: a primary user (operator), and a secondary user (passenger).
Primary User
The primary user must be able to interact with the system to provide the appropriate location information for the system input. At a minimum, the primary user must have the mental and physical capability to provide the current location and desired destination of the wheelchair via a simple keypad, which will require shape recognition and basic literacy. In instances where the passenger lacks this mental or physical capacity, they become the secondary user, and the primary user is regarded as the medical staff or guardian providing the input.
Secondary User
The secondary user, as mentioned, is regarded as the passenger that will be transported via the wheelchair to the specified destination. At a minimum, this user must be able to maintain a seated position within the confines of the chair dimensions, but no further physical or mental functions are specifically required. It is assumed that the secondary user will primarily be a patient who is unable to maintain proper control of a wheelchair due to mental of physical disabilities.
(Note: There may be one person who qualifies as both the primary and secondary user if the wheelchair passenger is capable of providing the location input.)
2 Uses
The system is designed for use in an indoor medical hospital or nursing home setting on one floor level. Other locations similar to an indoor medical hospital may provide an adequate for system operation, such as a residential home or office building, but are not explicitly covered by the system.
The system will navigate from one of any number of pre-selected locations to one of any number of pre-selected destinations, as specified by the primary user, if a reasonable path exists. The wheelchair will attempt to traverse an initial path calculated by the system while avoiding any incurred obstacles (both moving and stationary). If the current path is deemed impassable due to obstacles, the system shall attempt to navigate alternate. If all reasonable paths are judged impassable, the system will discontinue movement and signal that it is unable to proceed.
The system will be able to traverse reasonably shallow ramps or other such gradual changes in plain elevation, in the absence of large drop-offs. In order to obtain operation on another floor level, an outside user shall be required manually relocate the system.
5 Assumptions and Limitations
The operation of the system is constrained by the assumptions and limitations described in the following sections.
1 Assumptions
Certain elements were defined by members of the design team which attempt to further quantify the scope of the project. The list contained in Table 5.1 summarizes the general assumptions used during the system conceptualization and the justification for each.
Table 5.1 – Project Assumptions
|Assumption |Justification |
|The floor shall be a common floor type, typical |Operational Requirement |
|to electronic wheelchair navigation. | |
|The navigation shall be applicable to hospital |Design Requirement |
|environments. | |
|The primary user shall have the physical and |Design Requirement |
|mental capabilities to interact with the input | |
|system. | |
|The team shall have administrative access to |Testing Requirement |
|load software/hardware on senior design | |
|workstations. | |
The complexity of this project warrants assumptions for the prototype as well as the overall design. In order to ensure a manageable prototype to be implemented within the timeframe of senior design, the additional assumptions in Table 5.2 have been specified by the team.
Table 5.2 – Prototype Assumptions
|Assumption |Justification |
|The environment shall consist of a single floor |Design Requirement |
|level and no open drop-offs, such as stairs. | |
|The navigation shall be applicable to hallway |Design Requirement |
|environments, such as those on third floor Town | |
|Engineering. | |
|The team shall be provided with a motorized |Design Requirement |
|wheelchair in working condition. | |
|The system shall travel and detect obstacles, at|Design Requirement |
|least, in the forward direction during | |
|autonomous navigation. | |
|The system shall travel to one and only one |Design Requirement |
|destination at a time without intermediate | |
|waypoints. | |
|The localization technology of the wheelchair |Design Requirement |
|shall be attainable within the existing project | |
|budget. | |
2 Limitations
Additional elements of the project were identified as design restrictions which are beyond the control of the team members. The list contained in Table 5.3 summarizes the limitations acknowledged during the system conceptualization and the justification for each.
Table 5.3 – Project Limitations
|Limitation |Justification |
|The budget for the development the project shall|Design Requirement |
|not exceed $1150. | |
|The placement of the components shall not |Operational Requirement |
|interfere with the mobility or passenger | |
|accommodation of the wheelchair. | |
|All hardware shall be secured to the existing |Design Requirement |
|wheelchair frame or remain stationary within the| |
|operational environment. | |
|The hardware shall interface to the |Client Requirement |
|microprocessor through the use of LabVIEW | |
|Embedded 8.2. | |
|The system shall only be required to navigate |Design Requirement |
|between predefined locations. | |
|The localization technology of the wheelchair |Design Requirement |
|shall be attainable within the existing project | |
|budget. | |
6 Expected End Product and Other Deliverables
There are two expected end products of this project. The first is a complete design report, and the second is a prototype of this design implementing the most pertinent components. In addition to the end products, there are two additionally required deliverables, the project plan and final report.
Project Plan
The project plan is a document that defines that project and the plan for the completion of the project. It describes how design decisions were made for the project and defines the overall problem domain. This document was delivered in October of 2006.
Design Report
The design report is a document describing the full design of the system. As this project will not require outside funding, it will specify the details of the complete system: the schematic designs, component layouts, software design, and hardware specifications. It is intended to provide all the details necessary for replication of the project by an independent team. This document will be delivered in November of 2006.
Prototype
The prototype of the self-guided wheelchair system specified by the design documentation will be assembled and presented to the client. Since a complete system would require extensive funding, the prototype will be limited to the components of the design which demonstrate the basic, required navigational capabilities in a controlled environment and suggest further capabilities with the additional improvements and hardware. The team will assemble and test the equipment to verify proper autonomous navigation. This system will be delivered in May of 2007.
Final Report
The final report will be a document that provides the most complete description of the project along with a detailed record of its development. All aspects of the project, including the background development, testing, and end product description, will be covered in this document. This document will also provide suggestions for future work on the project. This document will be delivered in May of 2007.
Proposed Approach
Proposed Approach
The following material reiterates the requirements of the project and discusses the considerations included in the design of the system. This will include the functional requirements, constraints, technical considerations, testing and overall objectives. The purpose of this material is to clearly describe the components which will lead to a successful end product.
1 Design Objectives
The objective of this design is to solve transportation issues of a person confined to a wheelchair within a hospital environment. In order to successfully address the issues of concern with this problem, the project will be designed such that it meets the design objectives described in this section.
Autonomous navigation
The navigation of the wheelchair should be independent of user input, other than the starting and destination point. Turning corners, traversing straight and diagonal paths should all be controlled by the onboard processing unit with the aid of distance sensors, a compass, and a gyroscope.
Obstacle avoidance
The navigation of the wheelchair shall attempt to avoid any obstacle incurred in the intended path. In situations where it is easily possible to navigate around the obstacle, the wheelchair should attempt to continue towards its destination. In situations where continuation is not easily possible, the wheelchair should terminate navigation and signal an alarm to notify the user that path is blocked.
User interface
The user interface should be a visual, intuitive design which allows the selection of a starting point and destination point. The interface should also offer options for commencing and terminating operation. If time permits, visual indicators for direction of travel or detected obstacles may be implemented.
Reliable operation
The system should be designed to operate reliably for a few hours of operation in order to insure project feasibility. The navigation must be able to traverse a fairly smooth path free of sudden changes in direction or erratic movements. Smooth navigation will help ensure the safety and comfort of the passenger.
Ease of use
Simplicity of the system is an important factor in the marketability of the end product. The system must be easy to use with a small learning curve to ensure that hospital staff is not overwhelmed by implementation of the system, especially as the solution is meant to reduce their workload.
Low cost
Comparable autonomous navigations systems can be implemented for thousands, to tens and hundreds of thousands, of dollars. The system designed in this project should be attainable with components whose total purchase price is less than $1150, the project budget.
2 Functional Requirements
The complete system has the following functional requirements:
Basic function
The system shall autonomously traverse from one of several predetermined locations to one of several predetermined destinations, indicated by the primary user, if a reasonable path exists.
Navigation
The following list quantifies the requirements for the traversal of the system:
• The system shall calculate a path from the specified starting point to the specified ending point which is considered to be a direct route, although not constrained to be the absolute shortest route.
• The system shall attempt to travel on this predetermined path while avoiding both moving and stationary obstacles presiding in the path.
• If the current path is deemed impassable, due to an obstacle or closed door, etc, the system shall attempt to calculate alternate routes.
• If all reasonable paths seem impassable, the system shall indicate that it is unable to continue navigation.
• The system shall not attempt to traverse any stairwell, escalator, or other surface or area that is seemingly non-adjoining surface to the plain that the system is currently on.
• The system will be able to traverse reasonably shallow ramps or other such gradual changes in plain elevation.
3 Constraint Considerations
The following list specifies the restrictions on the complete system as deemed appropriate by team consensus or the laws of physics:
• The floor shall be a common floor type, typical to electronic wheelchair navigation.
• The environment shall consist of a single floor level and no large drop-offs.
• The primary user shall have the physical and mental capabilities to interact with the input system.
• The secondary user shall be of physical dimensions accommodated by wheelchair and be capable of maintaining a seated position during travel.
• The team shall be provided with a motorized wheelchair in working condition.
• The system shall only be required to navigate between predefined locations.
• The system shall travel to one and only one destination at a time without intermediate waypoints.
• The budget for the development the project shall not exceed $1150.
• The placement of the components shall not interfere with the mobility or passenger accommodation of the wheelchair.
• All hardware shall be secured to the existing wheelchair frame or remain stationary within the environment.
• The hardware shall interface to the microprocessor through the use of LabVIEW Embedded 8.2.
• The prototype design shall be limited to that which is accomplishable based on budget and time.
4 Technology Considerations
This section contains a very detailed description of the methods used to identify, evaluate and select the technology used for the design of this system. The scope of this project demands that the technical details be divided into manageable parts; therefore, this section, as well as the remaining sections of this document, will describe details as they pertain to the following categories: processing, obstacle detection, localization, power management, and user interface. Using the process outlined in Figure 6.1, the solution alternatives addressed in this section were identified, evaluated and selected. While the testing phase has begun, final verification is still in progress.
[pic]
Figure 6.1 – Technology Selection Process
1 Selection Criteria
The selection of each component was based on the following criterion:
Capability
This takes into account how well the system can handle the tasks demanded of it according to its functional requirements. This will also take into account physical dimensions as space is limited for mounting on the wheelchair. This category has the most weight as the technology must be capable of handling the necessary tasks.
Ease of implementation
This takes into account how much effort would be needed to coordinate interfacing with the other components in the system and the ease of running all required tasks. This category has the second highest amount of weight as the technology must be able to be implemented in the given time frame, with readily available knowledge.
Cost
This takes into account how much the component will actually cost to purchase, set up, and the associated labor. This category has the third highest amount of weight as the technology must be able to be implemented within the cost constraints of the project.
Durability
This takes into account how well the component will withstand vibrations on the wheelchair or possible abuses from the operator.
Ease of use
This takes into account how feasibly the component can be implemented into a commercial product where a learning curve may be associated with the programming and/or maintenance.
3 Microprocessor Hardware
The functionality requirements for the microprocessor include the ability to:
• Receive data from the selected sensors and localization technology
• Interpret data from sensors into an area mapping
• Receive input from the user interface
• Transmit commands to the motor control
• Transmit status indicators to the user interface
• Perform path calculation and obstacle detection
• Operate on LabVIEW Embedded 8.2
Since a solitary microprocessor would not be sufficient, considerations of microprocessors were done in the form of a microcontroller starter kit. The client offered two alternatives for consideration, both of which were suitable for LabVIEW Embedded 8.2 environment:
1. Motorola MPC565 microprocessor with Axiom CMD565 evaluation board
2. Motorola 68HC11 microprocessor with Handy Board
However, in order to do the complex calculations and mapping required for an onboard map and obstacle avoidance, significant memory must be available. Neither of the microcontroller kit alternatives offers a large memory option, therefore the capability of the prototype is severely limited. The suggestion of this team for commercialization of this project is to design a custom board with sufficient external memory interfaced to the microprocessor, as well as, serial connection, digital, and ADC ports. Therefore, two further possibilities were considered for solving issues with the proposed microprocessors:
3. PC104 form factor EPIC AMD™ Geode GX2 Low Power Single Board Computer
4. VIA EPIA-EN12000EG Mini-ITX Motherboard
1 Technology Considerations
The functionality requirements of the microprocessor dictate that technology considerations include the types and number of available I/O ports, available memory types and size, software usage, as well as power specifications for power management considerations.
Table 6.1 highlights the important features of the CMD565 evaluation board. A full list of the CMD565 specifications can be found in Appendix A.
Table 6.1 – CMD565 Evaluation Board [[i]]
|Axiom CMD565 Evaluation Board |[pic] |
|Pros |On board memory in additional to internal memory |
| |Ports for external LCD and Keypad |
| |Multiple I/Os for ADC, digital inputs, etc |
| |Low cost (provided by NI) |
| |32-bit microprocessor |
| |Compatibility with LabVIEW Embedded 8.2 |
|Cons |Large size (8 x 9.5 in) |
| |Non-expandable, limited memory |
| |4MB (onboard) + 1032KB (internal) Flash |
| |2MB (onboard) + 36KB (internal) RAM |
| |Micro attached via springs/compression |
|Cost |$0 (Donated by NI) |
Table 6.2 highlights the important features of the Handy Board. A full list of the Handy Board specifications can be found in Appendix B.
Table 6.2 – Handy Board [[ii]]
|Handy Board |[pic] |
|Pros |On board memory in additional to internal memory |
| |Built in 2-line LCD display |
| |Analog, digital and DC motor I/Os |
| |Compatibility with LabVIEW Embedded 8.2 |
| |Many support sites and examples of use available |
| |Soldered-on micro |
| |Compact size |
|Cons |Limited memory |
| |512 KB (internal) Flash |
| |32 KB (onboard) + 512 KB (internal) RAM |
| |8-bit microprocessor |
| |Higher cost |
|Cost |$299 [[iii]] |
Table 6.3 highlights the important features of the EPIC AMD Gode GX2. A full list of the EPIC AMD Gode GX2 specifications can be found in Appendix C.
Table 6.3 – EPIC AMD Gode GX2 [[iv]]
|EPIC AMD Gode GX2 |[pic] |
|Pros |On board memory in additional to internal memory |
| |Ports for external LCD and Keypad |
| |Multiple I/Os for ADC, digital inputs, etc |
| |32-bit microprocessor |
| |Compatibility with LabVIEW Embedded 8.2 |
| |Compact size (90 mm by 96 mm) |
| |Component architecture is adaptable |
|Cons |Highest cost |
| |No software backbone |
| |Higher level of integration using the PC104 form factor |
|Cost |$675 |
Table 6.4 highlights the important features of the VIA EPIA-EN12000EG Mini-ITX. A full list of the VIA EPIA-EN12000EG Mini-ITX specifications can be found in Appendix D.
Table 6.4 – VIA EPIA-EN12000EG Mini-ITX [[v]]
|VIA EPIA-EN12000EG Mini-ITX |[pic] |
|Pros |Multiple Peripheral I/O |
| |Large amount of memory and computing power |
| |Small power usage (12W to 15W max) |
| |Fully supports PC software |
| |Small size (170mm by 170mm) |
| |Compatibility with LabVIEW Embedded 8.2 |
| |Low cost for a Single Board Computer |
| |Efficient and stable |
| |Expandable |
| |Runs on ATX power supply which integrates into system design well |
|Cons |Not as many general I/O ports for sensor interface |
|Cost |$226.95 |
2 Selected Approach
Based on the criterion described in the previous section, Table 6.5 summarizes the controller evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..
Table 6.5 – Controller Technology Comparison
| |Capability |
|Pros |Low cost compared to other models |
| |Widely available |
| |Signal scatters diffusely off of most objects |
| |Unit available for testing from ISU Robotics Club |
|Cons |Wide beam width angle of 55˚ (can only detect doorways within ~4.8 |
| |ft.) |
|Cost |$ 27.72 |
Ultimately, this ranging module has been selected for use in the project because it is the cheapest module that meets the needs of the project.
Table 6.7 – SRF235 Sonar Sensor [[vii]]
|SRF235 Sonar Sensor |[pic] |
|Pros |15˚ beam-width (high resolution) |
| |100 measurements per second |
| |Detects hard, round objects well |
|Cons |Expensive |
| |Short maximum range (120 cm or 3.94 ft) |
| |Singe transducer (minimum range 10 cm) |
| |Must be less than 9˚ angle to surface of object or beam will |
| |reflect away |
|Cost |$141 |
This ranging module would be nice to use in the project but its cost is simply too high to be seriously considered.
Table 6.8 – SensComp 6500 Sonar Sensor [[viii]]
|SensComp 6500 Sonar Sensor |[pic] |
|Pros |Widely available |
| |Easy to use a variety of transducers |
| |Possible to read multiple echoes |
| |Angle of 30˚ to 34˚ |
|Cons |Transducer sold separately from module |
| |Expensive compared to other types |
| |High Power Requirements |
| |Min Range too far (6 in) |
|Cost |$49 |
This ranging module was not selected for use in the project because its power requirements were higher than necessary and power conservation is an important consideration since there are only two batteries to power the entire system.
Infrared sensors
Infrared (IR) proximity sensors work by sending out a beam of IR light, and then computing the distance to any nearby objects from characteristics of the returned, or reflected, signal. The infrared sensors considered for this project are summarized in Table 6.9 and Table 6.10.
Table 6.9 – Sharp GP2D05 IR Ranger [[ix]]
|Sharp GP2D05 IR Ranger |[pic] |
|Pros |Cheaper than sonar sensors |
| |Low current consumption (25mA) |
| |Fires on clock cycle to save power (0.3µA off current) |
|Cons |Only tells if obstacle is detected — does not give distance to |
| |obstacle |
|Cost |$19 |
This ranging module is not useful for the project because it does not indicate how far away a detected obstacle is from the sensor, and distance information is critical to the project.
Table 6.10 – Sharp GP2Y0A02YK IR Sensor [[x]]
|Sharp GP2Y0A02YK IR Sensor |[pic] |
|Pros |Low cost |
| |38ms between readings |
| |Max range 60” |
|Cons |Outputs analog signal (0-3V) to give distance to obstacle (A/D |
| |needed) |
| |Continuous reading — always on (33mA) |
| |Erroneous readings for obstacles closer than min. range (8”) |
|Cost |$12.50 |
Although this ranging module has a very low cost, an analog-to-digital converter would be needed for each sensor used, which will greatly complicate the design. Using this sensor would also result in a blind spot of 8 inches around the wheelchair.
Laser sensors
Laser sensors work similarly to IR sensors by sending out a laser signal, and then computing the distance to any nearby objects from characteristics of the returned, or reflected, signal. Laser sensors will have a higher resolution and are faster than ultrasonic sensors, but the price is not within the budget for the project. The laser sensor considered for this project is summarized in Table 6.11.
Table 6.11 – R283-HOKUYO Laser Sensor [[xi]]
|R283-HOKUYO Laser Sensor |[pic] |
|Pros |High resolution (0.36 degrees) |
| |10 readings per second |
| |Max range 4 meters |
| |Low power consumption (500mA and 5V) |
|Cons |Very expensive |
| |Requires serial or USB connection |
|Cost |$2695 |
A laser sensor would provide much more detailed information than a sonar sensor because of the high resolution, but the cost of the sensor is not within the budget of the project.
3 Selected Approach
Based on the criterion described in the previous section, Table 6.12 summarizes the ranging module evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..
Table 6.12 – Ranging Module Technology Comparison
| |Capability |
|Pros |Only needs to be calibrated once (stored in EEPROM) |
| |Low power consumption |
| |Affordable |
|Cons |Must be mounted parallel to ground for accurate readings |
| |Affected by flux in surrounding environment |
| |Proximity to metal can affect accuracy of readings |
|Cost |$52 |
This compass was chosen for use in the project because it meets the project requirements while still having a low cost.
Gyroscope
A gyroscope is needed to know the rate at which the wheelchair is turning so that the location of the wheelchair can be determined while making a turn. Unfortunately the wheels of the wheelchair do occasionally slip, which will result in a slight amount of inaccuracy in determining the present location. Table 6.14 summarizes the gyroscope considered for this project.
Table 6.14 – ADXRS150 Angular Rate Sensor [[xiii]]
|ADXRS150 Angular Rate Sensor |[pic] |
|Pros |Affordable |
| |Measures up to 150˚/sec |
|Cons |Can be easily damaged if dropped (2000 g) |
|Cost |$64.95 [[xiv]] |
This gyroscope will be used for the project because it meets the needs of the project and is fairly inexpensive.
4 Selected Approach
Based on the criterion described in the previous section, Table 6.15 summarizes the orientation sensor evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..
Table 6.15 – Orientation Technology Comparison
| |Capability |
|Pros |Affordable |
| |Accurate to 0.5˚ |
|Cons |Inaccuracy from wheel slip |
|Cost |$29 |
Using an odometer is not necessary for the project, and because of the wheel slip issue, an odometer will not be very useful in the case that it is implemented. Therefore an odometer will not be used for the project.
5 Selected Approach
Based on the criterion described in the previous section, Table 6.17 summarizes the distance tracking evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..
Table 6.17 – Distance Tracking Technology Comparison
| |Capability |
|Pros |Simple. This idea has been used elsewhere with success. |
| |Localization and navigation is greatly simplified. |
| |No need for obstacle avoidance. With a track, it would simply be |
| |marked and designated as an area that needs to remain |
| |obstacle-free. |
|Cons |Not innovative. Basically a glorified train, this option leaves |
| |little up to creative development. |
| |Obstacles. Since obstacle avoidance will be disregarded, in the |
| |event of a blockage in the path, the wheelchair will have to cease|
| |traversing until the obstacle is cleared. |
|Cost |Unavailable |
Dead reckoning
This option will implement an odometer. At a designated beginning location, the primary user will input the desired final location into the on-board computer via a keypad. With the computer’s on-board map it will command the wheelchair to travel a certain distance and at certain points turn a specific number of degrees. The odometer and computer together will record the remaining distance until the destination is reached. The Dead Reckoning method does not allow a means of zeroing out cumulative errors.
Table 6.19 discusses the pros and cons to this type of technology. It also contains a picture and price of the main element in this technique, an odometer.
Table 6.19 – Dead Reckoning Localization
|MA2 Miniature Absolute Magnetic |[pic] |
|Shaft Encoder | |
|Pros |Low Cost. Very few parts are necessary. |
| |Simple. The computer algorithms are simple. No off-board |
| |preparation is necessary. |
|Cons |Accumulated errors. Even traveling a short distance can accumulate|
| |direction and distance errors. Slippage may be an issue. Also, as |
| |little as 1-2 degrees in directional error could be problematic. |
| |Initial position. This method of localization and navigation |
| |requires the wheelchair to be initially positioned in a specific |
| |location. |
|Cost |$29 |
Tactile detection
This option implies physical contact with obstacles. When the wheelchair met a wall or obstacle it would bump into it to determine it impassable. It would then turn and try again. This option does not have any specific destination in mind but records all places it’s been and then uploads a map of possible routes. Table 6.20 summarizes considerations for this option of localization.
Table 6.20 – Tactile Detection Localization
|Pros |Simple operation |
| |Low Cost |
| |Technique already in use with other mapping robots such as vacuums|
|Cons |Dangerous when the device carries a person. |
| |Impractical for traversing a path. |
| |Not easy to implement. In a constantly changing environment, this |
| |device is not accurate enough. |
Fixed beacons
These beacons are fixed at appropriate locations in the environment. The precise locations of these beacons are known to the wheelchair’s onboard computer. As it moves, it uses the on-board device to measure its exact distance and direction from any one beacon. Hence the wheelchair can calculate its own precise position in the environment.
Radio Frequency Technology – The RFID technology uses readers and transponders in close range. The reader would be mounted to the wheelchair and its antenna can read small transponders it passes (within foot). These transponders, each with a unique ID number, would be neatly attached across the ceiling or floor width wise. As the wheel chair’s antenna crosses these transponders it will register the closest one and return the corresponding ID number to the computer. The computer which contains an on-board map with a record of all transponders and their precise location will update the wheelchairs current position and alter course as necessary.
Table 6.21 – RFID Localization
|APSX RW-310 RFID Reader/Writer |[pic] |
|Module and Transponders | |
|Pros |Low cost. Transponders have already been donated and the RFID device is |
| |reasonably priced. |
| |Simple. The concept is easy to understand. |
| |Innovative. Using RFID sensors as localization is not very common. This will |
| |provide the group with a well-rounded project. |
| |Compatible. Easy to apply to environment with little interference on previous |
| |activities. It is also easy to physically set up a course. |
| |Accurate within inches |
|Cons |Performance. The tags are not completely reliable. They will only work under |
| |specific conditions. |
| |Initial position. The wheelchair will need to be initially positioned so that |
| |it will eventually encounter a transponder to being its navigation. |
| |Needs to be in close range of transponders. |
|Cost |$173.92 |
Optical/ultrasonic imaging
This method involves using ultrasonic sensors mounted on the wheelchair. The sensors send out a pulse that is then reflected off nearby surfaces. The reflection is picked up by the sensors and recorded in the on-board computer. The pulse can “view” objects within a certain range of the chair. By recording the position of walls, doors, obstacles, etc. an image of the surroundings can be developed. A clear path can then be navigated.
Table 6.22 – Sonar Imaging Localization
|SRF04 Sonar Sensor |[pic] |
|Pros |Precise within inches. The reflected pulse will give the exact |
| |distance of an obstacle from the wheelchair. |
| |Low cost. Several would be needed but they are low price compared |
| |to other methods. |
| |Durable. These devices are not fragile. |
| |Commercializable. Sensors are widely available and this technique |
| |is already in use. |
|Cons |Incompatible. Sonar sensors are already being used for obstacle |
| |avoidance. Using this for mapping would interfere. |
| |Difficult implementation. The algorithms involved in using |
| |ultrasonic mapping are difficult and waypoints would still be |
| |required. |
|Cost |$ 27.72 |
6 Selected Approach
Based on the criterion described in the previous section, Table 6.23 summarizes localization technology evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..
Table 6.23 – Localization Technology Comparison
| |Compatibility |
|Pros |Simple to integrate |
| |“stand alone” converter |
| |Fairly inexpensive |
| |Precise and preconfigured/tested |
|Cons |Requires time for delivery, so testing will be stalled until it |
| |arrives |
|Cost |$1.74 |
Table 6.25 – Custom D/A Converters
|Custom D/A Converters |[pic] |
|Pros |Ready to use |
| |Easily modified |
|Cons |Components will still need to be ordered |
Control box connection – The most desired way to connect the controller and A/D converter is to connect it to the controller directly. There are two pins that control the motor control: pin 4 and pin 6. The signal provided by the joystick through these pins is a varying 200mV Peak-Peak AC signal that provides 5.9V ± 900mV DC offset. Table 6.26 summarizes the considerations for a control box connection.
Table 6.26 – Control Box Connection
|Control Box Connection |[pic] |
|Pros |Direct route to the controller |
| |Ideal connection for commercial production |
|Cons |Damaging the control box would be costly |
| |Control box is nearly impossible to replace due to its very old |
| |design |
Joystick connection – Directly tapping into the joystick to manipulate the voltages allows for the ability to let the joystick handle all of the output and the interface with the controller but does not worry about the more complex issues in dealing with the controller. Table 6.27 summarizes the considerations for a joystick connection.
Table 6.27 – Joystick Connection
|Joystick Connection |[pic] |
|Pros |Simple, DC voltage inputs required |
| |The joystick will produce the same AC signal as the control box |
| |was originally designed to handle |
|Cons |Not an ideal design for commercial production |
| |Technical documentation on the joystick is unavailable |
7 Selected Approach
Based on the criterion described in the previous section, Table 6.28 summarizes motor control technology evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..
Table 6.28 – Motor Control Technology Comparison
| |Compatibility |
|Pros |4x4 keypad with 3 function keys |
| |2x16 character display |
| |Backlight |
| |8 General Purpose Output Pins |
|Cons |Cable sold separately |
| |More power consumption w/ backlight |
|Cost |$ N/A |
Table 6.30 – Targus USB Numeric 19-Key Mini Keypad [[xviii]]
|Targus USB Numeric 19-Key Mini Keypad |[pic] |
|Pros |19 keypad |
| |Inexpensive |
| |USB interface |
| |Inexpensive |
|Cons |Less functionality |
| |Limited, 90 day warranty |
|Cost |$ 9.99 |
Table 6.31 – Kensington Pocket Keypad [[xix]]
|Kensington Pocket Keypad w/2-Port USB |[pic] |
|Hub | |
|Pros |17-key pad |
| |2-Port USB Hub |
| |More functionality |
| |Cable included |
| |5-year warranty |
|Cons |Expensive |
| |Fewer keys |
|Cost |$ 24.99 |
LCD
An LCD will allow the microprocessor to display what inputs are received and display information about the current position or operational indicators. Table 6.32 and Table 6.33 summarize the LCDs considered for this project.
Table 6.32 – Phidget Text LCD [[xx]]
|Phidget - PhidgetTextLCD 20x2 |[pic] |
|Character LCD | |
|Pros |Compatible design with the Mini-ITX |
| |2x20 character display |
| |8 Digital Inputs |
| |8 Analog Inputs |
| |8 Digital Outputs |
| |USB cable included |
| |Backlight |
|Cons |2-line display |
| |Expensive |
| |More power consumption w/ backlight |
|Cost |$109.13 |
Table 6.33 – Mini-Box picoLCD [[xxi]]
|Mini-Box - picoLCD 20x2 Character |[pic] |
|LCD | |
|Pros |Compatible design with the Mini-ITX |
| |2x20 character display |
| |Inexpensive |
| |Backlight |
| |8 General Purpose Output Pins |
|Cons |2-line display |
| |Cable sold separately |
| |More power consumption w/ backlight |
|Cost |$ 39.95 |
Touchscreen
A touchscreen will allow the user to input data with a customizable interface. The touchscreen will operate both as an input device and display. Table 6.32 summarizes the touchscreen considered for this project.
Table 6.34 – Optrex TM1B5BW Touchscreen [[xxii]]
|Optrex TM1B5BW Touchscreen |[pic] |
|Pros |Large 2.8" diagonal active area |
| |Selectable serial or 8-bit parallel interface |
| |5V supply voltage |
|Cons |More complex integration with eval board |
| |High price |
|Cost |$137 [[xxiii]] |
12 Selected Approach
Based on the criterion described in the previous section, Table 6.35 summarizes the distance tracking evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..
Table 6.35 – User Interface Technology Comparison
| |Capability |Ease of |
| | |Implementation |
|5V to digital input pin D0 |forward movement at about 1/16 max speed | |
|5V to digital input pin D1 |forward movement at about 1/8 max speed | |
|5V to digital input pin D2 |forward movement at about 1/4 max speed | |
|5V to digital input pin D3 |forward movement at about 1/2 max speed | |
|5V to all forward digital input pins |forward movement at max speed | |
|D0-D3 | | |
| |
|Forward / Backward Test |Result |Pass or Fail |
|5V to digital input pin D4 |backward movement at about 1/16 max speed | |
|5V to digital input pin D5 |backward movement at about 1/8 max speed | |
|5V to digital input pin D6 |backward movement at about 1/4 max speed | |
|5V to digital input pin D7 |backward movement at about 1/2 max speed | |
|5V to all backward digital input pins |backward movement at max speed | |
|D4-D7 | | |
As the speed of the wheelchair may be too fast for the system to handle appropriately and safely, the speed of the wheelchair may need to be toned down to resolve this concern.
4 Power Management
The following will cover the testing requirements for the power systems being used. Several systems have different options to consider if the initial testing fails. This section will first discuss testing for the simple power systems of the wheelchair, RFID reader, and computer then move on to the testing of the designed circuits.
Wheelchair
Testing plan –
• Team will test the dual 12V batteries by checking the drop across the two leads for each battery separate from the wheel chair.
• Team will test the wheelchair with batteries in place by running the wheelchair along a course and during time duration similar to the final demonstration.
Pass criteria – The wheelchair does not quit operation before trial is completed. The drop across the two leads each read a 12V drop.
Computer
Testing plan –
• Team will test the computer’s fully charged battery with the RFID software and a few other applications running. This will be done for the expected duration of the final demonstration.
Pass criteria – The battery lasts for the duration of the demonstration without needing to be recharged.
RFID reader
Testing plan –
• Team will test the reader’s fully charged battery running for the expected duration of the final demonstration.
Pass criteria – The battery lasts for the duration of the demonstration without needing to be recharged.
9VDC Power System
Testing plan –
• System will be built with wire that will be used in final prototype. All leads will be connected properly and tested with 9VDC battery.
• If first test fails, battery does not have enough power to supply device, two 9V batteries will be tested in series with a proper resistor to drop the voltage accordingly. This may provide more current to work with.
Pass criteria – Devices in 9VDC system operate correctly and for the amount of time necessary to finish a demonstration.
5VDC Power System
Testing plan –
• System will be built with wire that will be used in final prototype. All leads will be connected properly and tested with four 1.5VDC batteries and resistor/s that are equivalent to 1.83 ohms.
• If first test fails, battery does not have enough power to supply device, different battery types will be tested (AAA, C, D, etc.)
Pass criteria – Devices in 5VDC system operate correctly and for the amount of time necessary to finish a demonstration.
5 User Interface
This section describes how the team will conduct the testing on the keypad and the LCD as part of the user interface for the system. In order to be able to test the functionality and accuracy of the keypad and the LCD, the team will need to configure the setting of both the keypad and the LCD so they are compatible with the microcontroller.
Keypad
The team will provide different inputs where each number represents different locations for either the starting or destination area. The microcontroller will be pre-programmed to receive and understand the number from the keypad and associate it with a specified location to perform different actions depending on the location.
The testing will be to validate the user input and see if it sent the same number as what the microcontroller received. In addition, the testing will verify that a series of keystrokes provides the input in the correct mode, either the starting or destination mode. The test will be considered successful if the microprocessor receives the expected character as associated with the pressed key.
LCD
The team will provide different messages as the outputs from the microcontroller and see if the LCD received and displayed the message on the screen correctly. Also, the team will be testing other functionality on the LCD such as deleting the message, clearing the screen, and inserting a new line to print the message. The test will be considered successful if the display shows the expected characters.
6 System Integration
The integration testing is divided into phases. Similar to the concept of unit testing, the integration will be tested in modules concentrated on examining a specific group of components.
Phase I: Wheelchair control
The first phase of modular testing will test the microcontroller’s ability to predictably control the movement of the wheelchair. Basic movements such as forward, reverse, a 45 degree turn, a 90 degree turn, and varying speeds will be tested and verified.
Phase II: Wheelchair control with mapping
The second phase will be a continuation of the first where a map will be programmed into the microcontroller with a specific, short path of travel. The path will be constructed of the basic movements tested in the first phase. The compass and gyroscope data will be used to track the movements of the chair and determine the current and expected orientations. The objective will be to verify that the wheelchair follows the intended path and satisfactorily executes the basic movements.
Phase III: Wheelchair control with interactive mapping
The third phase will add a component of interactive mapping to the preprogrammed map. The microcontroller will use the data received from the range modules to add obstacles into the map. This will cause the intended path to be altered and recalculated around obstacles. The objective is to verify that the wheelchair avoids the obstacles while still traveling to the intended destination.
Phase IV: Wheelchair control with interactive mapping and localization
The fourth phase will add a component of localization to the mapping algorithm. Using waypoints strategically positioned about the environment, the microcontroller will receive data from the RFID reader indicating the nearest waypoint. The path will be extended for a longer duration where errors in tracking movements and orientation could occur. At each waypoint, the errors will be zeroed out and position within the onboard map verified. The objective is to verify that the wheelchair continues to avoid obstacles while still arriving at the intended destination.
Phase V: Wheelchair control with interactive mapping and localization and user interface
The fifth and final phase will add a user interface component. The same testing as described in phase four will be performed with the addition of customizable starting and ending points. This phase will also include adding informative messages to an LCD display while in route. The objective is to verify that the system will convert user input into a workable map/path and maintain performance.
5 Project Continuation
At this point in the development process, the project shall continue on as it was originally envisioned. This recommendation is made by the team as the design requirements have be specified, a practical approach to a working solution has been developed, and the design team consists of competent members who are committed to accomplishing the project goal.
However, the team suggests that additional phases of the project could further refine the design into a commercializable product. These phases could focus in more detail on a) the indoor localization system to be used for positioning, b) the obstacle avoidance algorithm, and c) a more sophisticated system of Simultaneous Localization and Mapping (SLAM). Additional improvements could also be made to the user interface and visual appeal of the complete system.
6 Detailed Design
The follow material will detail the design aspect of the autonomous wheelchair system. A general overview section describing the basic system integration will be followed by additional sections describing the main functional units.
1 General Overview
The overall design of the wheelchair system is an intricate interfacing of multiple inputs and outputs. Inputs from the environment are interpreted and used to calculate the path and location of the wheelchair. Figure 6.2 summarizes the inputs, processing and outputs of the system.
[pic]
Figure 6.2 – System Flow Diagram
The entire wheelchair system is connected via serial, USB, and other standard ports in addition to custom-designed analog and digital interfacing. Figure 6.3 depicts the system connections and power distribution.
[pic]
Figure 6.3 – Wheelchair System Diagram
Each of the components in the wheelchair system will be mounted directly on the chair, with the exception of RFID tags to be placed through the environment. The diagram in Figure 6.4 identifies the mounting position of each component. These positions have been chosen to accommodate the operation of the components, to allow for easy access, and to avoid interference with the wheelchair control.
[pic]
Figure 6.4 – System Mounting Diagram
2 Microprocessor
The controller and board are the center of the overall design. All external sensors and controls will connect directly to the controller as indicated in Figure 6.5, and all mapping and calculations will be performed with the controller using LabVIEW Embedded 8.2.
[pic]
Figure 6.5 – Controller Connection Block Diagram
1 Hardware
The controller used in this project is an EPIA-EN12000EG Mini-ITX from VIA. The main features are summarized in Table 6.37.
Table 6.37 – EPIA-EN12000EG Mini-ITX Features [5]
|Main Features | |
| Processor |1.2GHz VIA Eden nanoBGA2 Fanless |
| Cable/Connection |(x2) |RS232 |
| Power Consumption |12W – 15W (12-13W typical) |
|Memory | |
|On Board | |
| DDR2 533 SDRAM |1 DDR2 400/533 DIMM socket (Up to 1 GB) |
|Internal | |
| Flash |1024 KByte |
| RAM |36 KByte |
|Ports | |
| IDE |(x2) |UltraDMA 133/100/66 40-pin ATA133 |
| Serial ATA |(x2) |SATA |
| USB |(x6) |(x4) Back Panel USB v2.0 |
| | |(x2) Onboard USB 2.0 (via 1 pin header) |
| Firewire |(x1) |Onboard IEEE 1394 |
| Video |(x2) |(x1) VT1625M HDTV Encoder |
| | |(x1) S-Video Out |
| LAN |(x1) |VT6122 GLAN Controller (Gigabit) |
| PS/2 |(x2) |PS/2 keyboard/mouse |
| Serial |(x2) |(x1) Back Panel COM |
| | |(x1) Onboard COM |
| PCI |(x1) |PCI Slot |
|Dimensions |170mm x 170mm |
The output of the controller to each of the onboard sensors – compass, gyroscope, and ultrasonic sensors – and the wheelchair control box will be transmitted through the serial ports. The input received from these sensors will be received through the Analog to Digital Converter (ADC). Communication with the RFID reader will be made through the second RS232 serial port. The evaluation board is equipped to handle a KEYPAD and LCD through either a USB or a video port. Operation of the board requires up to 15W.
2 Software
The basic program flow of the software to be developed in LabVIEW for operation on the controller is summarized on the left side of Figure 6.6. The flow has been further modulated on the right side of this figure to indicate six main states of operation. These main states are idle, setup navigation, calibrate sensors, scan environment, obstacle avoidance, and navigation.
[pic]
Figure 6.6 – General Program Flow
Idle state
The idle state is the first state entered upon program execution. In this state the controller polls the keypad waiting for user input. No wheelchair movement is performed in this state.
checkKeypad – this function/VI polls the keypad port in a continuous loop and exit when a response is received indicating that a key has been pressed.
Setup navigation
The setup state is entered as soon as a key has been pressed on the keypad. The LCD display then presents the user will simple instructions for entering the starting and destination points. Once these inputs are received the controller calculates a path from the starting to destination point within the preprogrammed map. No wheelchair movement is performed in this state.
getInputs – this function/VI prompts the user for the starting point, wait for confirmation, prompt the user for the destination point, wait for confirmation, then output the coordinates of the two points.
calPath – this function/VI receives the starting and ending point and calculates a path from the starting point to the destination from within a preprogrammed map. The path consists of blocks containing distances and maneuvers to be executed in order to reach the destination.
Calibrate sensors
The calibration state is entered as soon as the path has been calculated. The controller then sends stimulus signals to the ranging modules and orientation sensors for calibration. No wheelchair movement is performed in this state.
calSensors – this function/VI sends a stimulus signal to the ranging modules preparing them for operation.
calOrient – this function/V sends a stimulus signal to the compass and gyroscope preparing them for operation. It also stores the current values in memory for reference.
Scan environment
The scan environment state is entered either directly after calibration of sensors or after a movement has been performed. In this state, the controller sends stimulus signals all of the sensors and RFID reader then stores the returned data. The data is recalled and used to determine if an obstacle is within critical distance and to determine the orientation of the wheelchair and position within the map. The wheelchair may be in motion during this state.
scanEnviro – this function/VI sends a stimulus signal to all of the sensors and RFID reader then stores the returned data.
checkPos – this function/VI recalls the gyroscope, compass, and RFID data to determine the orientation of the wheelchair and the location relative to waypoints programmed into the map. This information is then stored.
checkObs – this function/VI recalls the ranging module data to determine if an obstacle is detected within a critical distance relative to current operation.
recalcPath – this function/VI recalls the position and obstacle data. If the position is not within tolerance of the expected position, the remainder of the path is recalculated with the current position as the new starting point. If an obstacle is detected as an upcoming, but not immediate threat, the path is recalculated around the expected perimeter of the obstacle.
Obstacle avoidance
The obstacle avoidance state is entered if an obstacle is detected within a critical distance relative to the current operation. In this state, the controller issues a command to halt navigation, recalls the ranging module data, determines an unobstructed direction, and issues a command to turn right or left in the clear direction.
stopChair – this function/VI sends a stimulus signal to the wheelchair control box that discontinues movement.
avoidObs – this function/VI recalls the ranging module data and determines whether or not an unobstructed direction exists. In the instance where a clear direction can be determined, a stimulus signal is sent to the wheelchair control box to rotate in that direction. However, if it cannot be determined that there is a clear alternate route, a warning is issued to the user.
General navigation
The general navigation state is entered when the current path is free of obstacles. In this state, the controller issues navigational commands to the wheelchair control box based on the position determined in the scan environment state.
moveFwdRvs – this function/VI sends a stimulus signal to the wheelchair control box that rotates both chair wheels, simultaneously, at the same speed.
rotLeftRight – this function/VI recalls the ranging module data and determines whether or not the intended direction of travel is unobstructed. In the instance where the direction is clear, a stimulus signal is sent to the wheelchair control box to rotate the appropriate amount in that direction. However, if it cannot be determined that the intended direction is clear, a warning is issued to the user, and the obstruction will be treated as an obstacle.
adjSpeed – this function/VI recalls the position and obstacle data and sends a stimulus signal to the wheelchair control box either increasing speed, if the path is clear, or decreasing speed, if the path is beginning to detect obstacles or will change direction shortly.
3 Sensors
The following sensors will be used in the design for the project. Included are the technical sepcifications for each sensor, how they are interfaced with the controller, and how they are used.
1 Ranging Module
The technical specifications for the SRF04 ultrasonic sonar sensor are shown below. Also shown are the pin connections and how they are used.
Ranging Module: SRF04 Ultrasonic Sonar Sensor
Table 6.38 – SRF04 Technical Specifications [[xxiv]]
|Beam Width |~55˚ |
|Power | |
| Voltage |5 Volts |
| Current |30 mA Typical, 50 mA max |
|Frequency |40 kHz |
|Clock |625 kHz (1.6 µs) |
|Range | |
| Maximum |3 m |
| Minimum |3 cm |
|Sensitivity |Detect 3 cm diameter stick at > 2 m |
|Weight |0.4 oz |
|Size |1.75” w x 0.625” h x 0.5” d |
Table 6.39 – SRF04 Pin Connections [[xxv]]
|5V Supply |Needs 5 volts DC to power the device |[pic] |
|Echo Pulse Output |This pin creates a pulse proportional in width to| |
| |the distance of the nearest object detected. | |
|Trigger Pulse Input |A 10µs pulse is used in this pin to trigger the | |
| |device and send the echo pulse. | |
|Do Not Connect |This pin is not used. | |
|0V Ground |This is the pin for the connection to ground. | |
The timing diagram in Figure 6.7 shows that to trigger the sensor, a 10µs pulse must be sent on the trigger input pin. There must be at least 10ms between the end of the echo pulse and the beginning of a new trigger pulse. The sonic burst sent out by the sensor is a set of 8 bursts at 40 kHz. Once the return of the sound wave is detected, an echo pulse will be sent on the echo output pin that is proportional in width to the distance of the nearest detected object. The width of that pulse ranges from 100µs to 18ms, or is 36ms if the pulse does not return (nothing detected). The maximum range of the sensor is 118 inches (9m), or 236 inches round trip. With sound traveling 1 inch every 73.746µs, it will take at most 17.4 ms for the pulse to return. Therefore, the maximum time between triggers of the device is about 64ms (18ms + 36ms + 10ms).
[pic]
Figure 6.7 – SRF04 Timing Diagram [25]
The beam pattern pictured in Figure 6.8 gives the effective detection range for the sensor. The angular beam width is about 55˚, which will detect a 30” doorway at a distance of about 2.4 feet or less. (Calculation: 15 / tan(27.5˚))
[pic]
Figure 6.8 – SRF04 Beam Pattern [24]
Mounting
An arrangement of 13 sonar sensors will be used as pictured in Figure 6.9. The two sensors mounted on each side of the wheelchair facing the walls can be used to measure the distance to the walls. This will make it easier to travel in a direction parallel to them. The sensors on each side mounted at a 60˚ angle will help for the detection of doorways. In order to detect a 30” doorway, the wheelchair will need to be less than 19.6” away from the wall (Calculation: 30tan(2.5˚)/[(tan57.5˚-tan2.5˚)*tan2.5˚]). The remaining sensors mounted on the front will be used primarily for obstacle detection and avoidance. A mounting diagram is shown in Figure 6.9.
[pic]
Figure 6.9 – Ranging Module Mounting Arrangement
The image in Figure 6.10 shows what the sensors, mounted as described, might see in a typical hallway. Red is an area free from obstacles as detected by the sensors, dark blue shows blind-spots, and light blue is halls and rooms. The wheelchair is depicted by the grey square. The picture shows that the resolution of the sensors will be fairly low and that it will not be easy to distinguish walls from obstacles.
[pic]
Figure 6.10 – Ranging Module Mapping in a Hallway
2 Orientation
Shown below are the technical specifications for the R117 magnetic compass. Also shown are the pin connections and their uses.
Compass: Devantech R117 Magnetic Compass
Table 6.40 – R117 Compass Technical Specifications [12]
|Power | |
| Voltage |5 Volts |
| Current |20 mA |
|Resolution |0.1˚ |
|Accuracy |~3-4˚ after calibration |
|Outputs | |
| Primary |Timing Pulse 1-37 ms (0.1 ms increments) |
| Secondary |I2C Interface, 0-255 and 0-3599 |
|SCL Speed |Up to 1 MHz |
|Weight |0.03 oz |
|Size |32 mm x 35 mm |
Table 6.41 – R117 Compass Pin Connections [[xxvi]]
|1 |Needs supply voltage of 5 volts to power the |[pic] |
| |device. | |
|2 |Used for I2C interface | |
|3 |Used for I2C interface. | |
|4 |Pulse width modulator. | |
|5 |No connect. | |
|6 |Used for initial calibration. The pin has a | |
| |pull-up resistor and can therefore be left | |
| |unconnected after the calibration. The | |
| |calibration only needs to be done once | |
| |because the data is stored to EEPROM. By | |
| |default, the calibration is set for use at | |
| |67˚ latitude. | |
|7 |Used to select 50Hz (low) or 60Hz (high) | |
| |operation. | |
|8 |No connect. | |
|9 |Connection to ground. | |
The heading of the compass can be given as a pulse width modulated signal that varies from 1ms to 36.99 ms, where each 100µs represents 1˚. The time between pulses is 65ms, where the signal will have a negative voltage. In order to use the PMW mode of operation, the I2C pins (2 & 3) must be connected to the 5V power supply using 47 kΩ resistors.
The timing diagram in Figure 6.11 shows how the alternative I2C interface can be used to obtain compass measurements. However, this method will not be used for the project since the PMW method will be better suited to the needs of the project.
[pic]
Figure 6.11 – R117 Compass Timing Diagram [26]
Mounting
The device must be mounted parallel to the ground to function properly and cannot be used near magnetic fields, such as the ones created by some motors. Proximity to metal can also interfere with the accuracy of the device. The best place to mount it will be behind the chair, out of sight and near the controller and batteries.
Gyroscope: ADXRS150 Angular Rate Sensor ADXRS150
Shown below are the technical specifications for the ADXRS150 angular rate sensor.
Table 6.42 – ADXRS150 Gyroscope Technical Specifications [[xxvii]]
|Power | |
| Voltage |4.75 to 5.25 V |
| Current |6 mA |
|Range |+/- 150˚/s |
|Sensitivity |12.5 mV/˚/s |
|Typical Bandwidth |0.04 kHz |
|Noise Density |0.05 ˚/s/rtHz |
|Nonlinearity |0.1% of FS |
|Temp Sensor |Yes |
|Voltage Reference |Yes |
|Temp Range |-40 to 85˚ C |
|Package |32-BGA |
Mounting
The gyroscope can also be mounted on the back of the wheelchair, just above the compass. This will keep it out of sight and safe from damage if the wheelchair collides with anything.
4 Localization
Following is the detailed plan for localization design. How the technology will operate and the research will be covered. Next, this section will describe the specifications of the chosen device as well as connections and other devices needed for this technology to be implemented.
Operation
To traverse from one point to another using this technology, the wheelchair will need to initially be placed by the primary user in a location facing towards the final destination along a clean route to the first row of RFID tags as shown in Figure 6.12. The wheelchair will begin its motion in a straight forward path. As it passes over the row of transponders the onboard computer will recognize the relayed ID number of the closest one and update it’s location into the computer’s on-board map. The wheelchair will then adjust its direction accordingly. When the antenna passes over any of the transponders in the last row before the intended destination the chair will be programmed to stop.
[pic]
Figure 6.12 – RFID Tag Placement
Each path will be programmed into the computer. For example, if the chair starts at point B and is commanded to travel to point D the computer will have a preprogrammed sequence of transponder rows to follow. From point A to point B, the computer has a different sequence.
Research
The team researched the use of two different types of RFID readers, low frequency which reads solid plastic and glass transponders at 134.2 kHz and high frequency which reads solid transponders as well as convenient, thin, tags at 13.56 MHz. The team was initially provided with a low frequency reader kit as well as high frequency tags. Although the team had the option of using the provided reader, the team would prefer to use a high-frequency reader with an antenna that has a larger reading area. The RFID sensor device the team has considered implementing is an APSX RW-310 Reader/Writer Module found via the internet. Following are the specifications of this device.
Images of the transponders provided in the kit are shown in Figure 6.13 . On the left is an image of the reader itself equipped with a serial port. The device below the RF reader is shown a C-100 converter that can be purchased as well. This device boosts the signal levels to the RS232 so that it can communicate with the computer. If this device passes the initial tests the team will choose to purchase the C-100.
[pic]
Figure 6.13 – APSX RW-310 RFID Reader/Writer Module and Transponders
Table 6.43 describes the main features and specifications of the selected RFID reader/writer module.
Table 6.43 – RW-310 RFID Reader/Write Module Features
|Read/Write Frequency |13.56MHz |
|Data Rate |19200 bps |
|Range | |
| Credit card size tags |11” |
| CD/DVD size labels |5” |
| 24mm circular labels |4” |
| Mini tags |6” |
|Read Area |9" x 8" |
|Other Features |On-board antenna |
| |Built-in TTL. Need to use level converter to connect directly to PC (max232)|
| |or use APSX C-100 converter board. |
| |DC or Battery power for mobile operations. Power consumption 20mA at stand |
| |by, 80mA in fast mode (20 reads per sec.) |
| |Powerful firmware enables read and write any type of 13.56 MHz RFID tag |
| |(ISO15693) |
| |Shorter transaction time than 125 kHz systems |
| |Two programmable LEDs are available for visual feedback |
|Power |standard 6VDC wall adaptor or 6-9 VDC |
|Dimensions |9" x 6” x 0.25” |
This RF device the team will use operates at 13.56 MHz and will pick up reflected signals from 1in2 flat, sticky back, read/write transponders. The reader and antenna will be attached to the wheelchair to the base near the ground. The transponders will be laid in a straight line the width of the hallway or room. These transponders have been provided by senior design, will not need to be purchased, and will not hinder the project budget. They are 13.56/914 MHz tags.
Power
This device is equipped with DC or battery power option. It needs 6-9V at 80mA to run. The team will rely on the battery power option for this device and mention, but not discuss, the power requirements for this device in the on-board power section of this design report.
Connections
The RFID reader has a male serial cable port to communicate with the computer. Included with the reader is software to be loaded onto a computer that will then send read or write commands to the reader. The design team would have preferred to connect the RFID reader directly to the microprocessor but are still waiting for a reply from the manufacturer. Currently, it is unknown whether the software will be able to be loaded onto the provided microprocessor. Due to the difficulty with integrating the RFID reader and controller the reader will be directly connected into the computer through a serial port as shown in Figure 6.14 . This will meet out needs and is the current plan. Specific software considerations will need to be reviewed concerning this after the device is purchased.
[pic]
Figure 6.14 – Computer to RFID Reader
5 Motor Control
The motor control design is created to mimic or simulate the signals created in the joystick. This circuit is based of a 5.9V signal that is used within the joystick to provide the necessary mapped output to the wheelchair motor control box. The joystick itself is a two-dimensional potentiometer that manipulates the voltage level of the forward and backward, as well as right and left movements when the user moves the joystick in one direction or another. A signal level of 5.9V on both the forward and back, and right and left signals is interpreted by the joystick control as centered, and thus not moving. The voltage level of both signals is than raised or lowered by a value up to +/- 900 mV. The joystick circuit then translates the 5.9V +/- 900 mV analog signal to a complex signal which is sent to the wheelchair motor control box. The important operation of the joystick is shown in Figure 6.15.
[pic]
Figure 6.15 – Invacare Arrow Joystick Schematic
As the voltage level rises for the forward and backward direction from 5.9V, the wheel chair moves forward, virtually similarly proportional to the rise in voltage. When the voltage reaches 6.8V (5.9V + 900mV), the wheelchair will be moving forward at top speed. As the voltage level decreases from 5.9V, the wheel chair starts moving backward until the voltage level reaches 5.0V, which is fully backward. A connection diagram which will output these desired signals is shown in Figure 6.16.
[pic]
Figure 6.16 – Controller to Joystick Connection Diagram
There are two sets of op-amps that convert the digital signal into an analog signal. The top-left four op-amps are used to create the forward move signal. The bottom-left four op-amps then convert the backward move signal. These two signals are then summed together, and converted to a +/- 900 mV signal, which is then summed with the 5.9V stationary signal. This output will be fed into pin 4 of the DB15 connector to the motor control box. Table 6.44 summarizes the digital output mapping necessary for forward and reverse motor control.
Table 6.44 – Digital Output Mapping to Motor Control (Forward/Reverse)
|Digital Output From Controller |Wheelchair Movement Direction |D/A Output Voltage |
|00000000 |Stationary |5.9V |
|00001111 |Full Forward |6.8V |
|11110000 |Full Reverse |5.0V |
The signal for the right and left control is the same signal and circuit that is used as the forward and backward control; with the right turn signal being the same as the forward movement signal, and the left turn signal being the same as the backward movement signal. This output will be fed into pin 6 of the DB15 connector to the motor control box. Table 6.45 summarizes the digital output mapping necessary for left and right motor control.
Table 6.45 – Digital Output Mapping to Motor Control (Left/Right)
|Digital Output From Controller |Wheelchair Movement Direction |D/A Output Voltage |
|00000000 |Stationary |5.9V |
|00001111 |Full Right |6.8V |
|11110000 |Full Left |5.0V |
6 Power Management
Following is a description of the power design that will be implemented. This will include configurations as well as specifications for the circuitry required.
The systems will be combined as follows:
5VDC Battery 9VDC Battery Portable Power Already Supplied
Compass Controller Wheelchair
Gyroscope Computer
Ultrasonic Sensors RFID Reader*
*The RFID reader could also be supplied by the 9VDC battery system and therefore be combined with the Controller.
This grouping would require 5 or 4* separate power sources. Figure 6.17 and Figure 6.18 are diagrams of the circuits for the 5VDC and 9VDC systems. The 9VDC circuit includes the reader.
[pic]
Figure 6.17 – 5VDC System
[pic]
Figure 6.18 – 9VDC System
The 9VDC system in Figure 6.17 should work well with a regular 9VDC battery. The specifications in Table 6.46 are of the battery that should serve the purpose.
Table 6.46 – 9V Energizer Battery Specifications
|Classification |Alkaline |
|Chemical System |Zinc-Manganese Dioxide (Zn/MnO 2) |
|Designation |ANSI-1604A, IEC-6LR61 |
|Nominal Voltage |9.0 volts |
|Operating Temp |-18°C to 55°C (0°F to 130°F) |
|Typical Weight |45.6 grams (1.6 oz.) |
|Typical Volume |21.1 cubic centimeters (1.3 cubic inch) |
|Jacket |Metal |
|Shelf Life |5 years at 21°C (80% of initial capacity) |
|Terminal |Miniature Snap |
|Capacity |625 mAh |
With this capacity, 625 mAh, this circuit should be able to run the 9VDC circuit (as shown with RFID reader attached) for at least an hour and a half non-stop. This will satisfy the time requirement
The 5VDC system in Figure 6.18 will need to be constructed differently. It is unnecessary to find a 5VDC battery. Instead, four 1.5VDC batteries can be used and a resistor in line with the battery will drop the voltage so about 5V will be delivered to the devices.
A major factor to take into consideration with this set up is that when the ultrasonic sensors are not sending a pulse the current they draw would be 20mA. Therefore the current range this circuit will run at is 416 mA (when all 13 sensors are 20mA) to 676 mA (when all 13 sensors are 50mA). Accordingly, the voltage drop across the resistor will increase or decrease. Since all devices can operate between 4.5V to 5.5V (optimum at 5V) this should not cause a problem as long as a proper resistor value is found. Figure 6.19 shows how this circuit would be constructed.
[pic]
Figure 6.19 – 6VDC to 5VDC
After figuring a median current draw of 546 mA the resistance with the extreme values furthest from the voltage limit was found. A resistance of 1.83 mA gives a voltage range of 4.76V – 5.24V to the devices. This will not put any of the devices at great risk.
There are several 1.5V batteries that can be used for this circuit. Regular AA, AAA, C, and D can all be used. For the team’s purpose four AA batteries will work. The specifications in Table 6.47 are for an Energizer AA battery.
Table 6.47 – AA Energizer Battery Specifications
|Classification |Alkaline |
|Chemical System |Zinc-Manganese Dioxide (Zn/MnO 2) |
|Designation |ANSI-15A, IEC-LR6 |
|Nominal Voltage |1.5 volts |
|Nominal IR |150 to 300 milliohms (fresh)* |
|Operating Temp |-18°C to 55°C (0°F to 130°F) |
|Typical Weight |23.0 grams (0.8 oz.) |
|Typical Volume |8.1 cubic centimeters (0.5 cubic inch) |
|Jacket |Plastic Label |
|Shelf Life |7 years at 21°C (80% of initial capacity) |
|Terminal |Flat Contact |
|Capacity |2850 mAh |
The capacity rating for this battery will allow the system to run long enough to serve its purpose. This system should last at least 4 hours of non-stop operation.
All-in-all the time-limit for portable, non-stop operation will be approximately 1 ½ hrs. This will be plenty of time for demonstration and testing of the team’s prototype. After that amount of time (limited by the 9V battery) this element can be cheaply replaced.
7 User Interface
This section provides more in-depth detail about the keypad and the LCD. It includes information regarding the schematics, basic operations, the connection, and the pin assignment. Neither the keypad nor the LCD will need an individual power supply as power will be supplied via the connector.
Keypad
The keypad will be connected directly to the controller through a USB port. The controller will continuously poll the keypad during idle operation and while obtaining the starting/ending positions.
LCD
The LCD will be connected directly to the controller through a USB port, similar to the keypad. Control Codes are used for LCD panel setup and control of character or cursor position. All control codes are contained in a software library provided with the LCD hardware (PHIDGET.msi). The characters displayed on the LCD will resemble the characters shown in Figure 6.20.
[pic]
Figure 6.20 – LCD Character Displays [[xxviii]]
Mounting
The LCD and keypad will be mounted behind the seat of the wheelchair at approximately waist height. Mounted at this position allows the user interface to be at easy access for a standing user, such a member of the hospital staff, and also keeps the components from interfering with the wheelchair operation.
8 Design Summary
The design described attempts to address the main functionality requirements as shown in Table 6.48. Each functionality is ranked according to its relative importance to the overall design. The design presented in this document is then given an evaluation score which measures how well the design meets the functionality requirement. The resultant score for this design is 91.75%.
Table 6.48 – Evaluation of Design Functionality
|Functionality |Relative Importance |Evaluation Score |Resultant Score |
|LabVIEW Embedded controlled operation |35% |100% |35% |
|User-selectable starting and ending points |5% |95% |4.75% |
|Path calculation |10% |90% |9% |
|Obstacle detection |10% |90% |9% |
|Obstacle avoidance |5% |80% |4% |
|Location recognition |10% |50% |5% |
|Speed control (forward, reverse, stop) |15% |100% |15% |
|Turn control with 5% accuracy |10% |100% |10% |
|Total |100% | |91.75% |
Estimated Resources
Estimated Resource Requirement
The following material specifies the estimated hourly, financial, and other resource requirements for the project.
1 Personnel Requirements
The information in Table 7.1 reiterates the initial estimates of hours per task for each team member as stated in the Project Plan.
Table 7.1 – Estimated Person Hours (Original)
|Name |Task 1 |
| |Definition |
| Devantech R117 Magnetic Compass |(x1) |$52.00 |
| ADXRS150 Angular Rate Sensor |(x1) |$64.95 |
| SRF04 Sonar Sensor |(x13) |$360.36 |
| RFID Reader & Eval Kit |(x1) |$200.00 |
| RFID Tags * |~(x250) |-- |
| EPIA-EN12000EG Mini-ITX |(x1) |$226.95 |
| LabVIEW Embedded 8.2 ** |(x1) |-- |
| |Total |$904.26 |
|* Previously donated to Senior Design by MetalCraft |
|** Provided by National Instruments |
2 Financial Requirements
The financial requirements are a breakdown of the cost of the project. This will represent the total cost associated with other resources, project deliverables, and labor at $10.50 per hour. The original financial requirements estimates in Table 7.4 have been updated as shown in Table 7.5, reflecting the changes mentioned in the Other Resources section and revised labor estimates.
Table 7.4 – Material and Labor Costs (Original)
|Materials |Cost Estimate |
| Poster |$50.00 |
| Sensors |$500.00 |
| Wheel Chair * |-- |
| RFID equipment * |-- |
| CMD500 series board ** |-- |
| EPIA-EN12000EG Mini-ITX |$226.95 |
| Mounting Equipment |$100.00 |
| Wiring and Misc. Equipment |$50.00 |
|Subtotal |$926.95 |
| | | |
|Labor |Hours |Labor ($10.50 per hour) |
| Tara Spoden |240 |$2,520.00 |
| Brian Yauk |235 |$2,467.50 |
| Margaret Shangle |220 |$2,310.00 |
| Vee Shinatrakool |205 |$2,152.50 |
| John Volkens |250 |$2,625.00 |
|Subtotal |$12,075.00 |
|Total |$13,001.95 |
|* Provided by Senior Design |
|** Provided by National Instruments |
Table 7.5 – Material and Labor Costs (Revised)
|Materials |Cost Estimate |
| Poster |$50.00 |
| Other Resources |$904.26 |
| Mounting Equipment |$100.00 |
| Wiring and Misc. Equipment |$50.00 |
|Subtotal |$1104.26 |
|Labor |Hours |Labor ($10.50 per hour) |
| Tara Spoden |291 |$3,055.50 |
| Brian Yauk |283.25 |$2.974.16 |
| Margaret Shangle |281.75 |$2,958.38 |
| Vee Shinatrakool |267.25 |$2,806.16 |
| John Volkens |289.75 |$3,042.38 |
|Subtotal |$14,836.58 |
|Total |$15,940.84 |
|* Previously donated to Senior Design by Invacare |
Schedules
Schedules
The figures in this section illustrate the project task schedules and deliverable timelines in the form of Gantt charts. A comparison of the original and updated schedules for the fall semester of 2006, shown in Figure 8.1 and Figure 8.2 respectively, indicates that the group has had to deviate from the original projections under certain phases of the project.
[pic]
Figure 8.1 – Fall 2006 Task Schedule (Original)
[pic]
Figure 8.2 – Fall 2006 Task Schedule (Revised)
Furthermore, the original task schedule for the spring semester of 2007 in Figure 8.6 has been updated and revised as shown in Figure 8.4.
[pic]
Figure 8.3 – Spring 2007 Task Schedule (Original)
[pic]
Figure 8.4 – Spring 2007 Task Schedule (Revised)
Additionally, the original timetables for the deliverables schedule shown in Figure 8.5, have been updated to reflect an extension in the Design Report submission date in Figure 8.6.
[pic]
Figure 8.5 – Full Project Reporting and Deliverables Schedule (Original)
[pic]
Figure 8.6 – Full Project Reporting and Deliverables Schedule (Revised)
Project Team Information
Project Team Information
This section contains contact information about the client, faculty advisor, and team members involved in the project.
Client:
Company: National Instruments
Contact: Andrew Dove
Email: andrew.dove@
Phone (office): (512) 683-8409
Phone (fax): (512) 683-6837
Mailing Address:
National Instruments
11500 N Mopac Expwy
Austin, TX 78759-3504
Faculty Advisor:
Name: Dr. Nicola Elia
Email: nelia@iastate.edu
Office: 3131 Coover
Phone (office): (515) 294-3579
Phone (fax): (515) 294-8432
Mailing Address:
Iowa State University
3131 Coover
Ames, IA 50011-3060
Team Members:
Name: Margaret Shangle
Major: Electrical Engineering
Email: mgs12@iastate.edu
Phone (cell): (515) 450-4812
Phone (home): (515) 292-4872
Mailing Address:
2239 Knapp St.
Ames, IA 50014
Name: Vee Shinatrakool
Major: Computer Engineering
Email: vees@iastate.edu
Phone (cell): (515) 708-0720
Mailing Address:
4212 Westbrook Dr #22
Ames, IA 50014
Name: Tara Spoden
Major: Electrical Engineering
Email: tspoden@iastate.edu
Phone (cell): (563) 581-7454
Mailing Address:
4532 Steinbeck St #110
Ames, IA 50010
Name: John Volkens
Majors: Computer Engineering
Email: jvolkens@iastate.edu
Phone (cell): (515) 290-6204
Phone (home): (515) 572-5324
Mailing Address:
Iowa State University
1265 Friley Dodds
Ames, IA 50012
Name: Brian Yauk
Major: Electrical Engineering
Email: byauk@iastate.edu
Phone (home): (515) 572-0499
Mailing Address:
Iowa State University
4225 Willow Lancaster
Ames, IA 50013
Closing Summary
Closing Summary
The design proposed for this project is a complex integration of several major components. Since multiple inputs must be analyzed and used to perform detailed calculations, a central processing unit in the form of a Mini-Itx board will be used. This device will receive input from the ultrasonic ranging modules which will indicate distances to obstacles in the environment. The controller will also receive input from the gyroscope and compass indicating the orientation of the wheelchair. The importance of localization and the ability to determine the wheelchair’s present location at any given time during travel requires the use of a technology such as RFID to identify the environment. The controller will receive identification information about RFID tags in the area of its current location.
Processing the inputs will require a complex obstacle avoidance and path calculation algorithm to be programmed and computed within the controller using LabVIEW Embedded. There will also be an onboard map stored in memory which the controller will use for reference incoming data. The calculations indicating direction of travel of the wheelchair will be output from the controller and converted into an analog signal recognizable by the motor control box.
This system has been designed to meet the functionality requirements of the project and demonstrate the ability of LabVIEW Embedded to communicate through target VIs with multiple forms of hardware. The implications of this project in the medical world which should be sufficient to resolve staffing issues that arise from transport of wheelchair-confined patients.
Appendix A
Appendix A
Axiom CMD565 Evaluation Board Specifications
The CMD-565 system provides the CMD-5xx Motherboard and the PM-565 Personality Module to provide a MPC565 development environment. The system is Plug and Play with the supplied Axiom Monitor in the on-board EPROM. Board features 2MByte (512K x 32) Synchronous SRAM, 4MByte (1M x 32) Burst Flash EEPROM, Communication Interfaces, Port Replacement Logic Unit, Keypad and LCD Module support, Serial Cable, Wall Plug power source, printed hardware manual and the MPC5xx support CD with programming utilities, support and sample software, and technical manuals.
Standard Features:
• Global Wall-Plug Power Supply (CE certified)
• Processor in socket on PM-5xx board with ZIF socket
• Mictor Logic Connectors for Address, data, and control signals
• AMD AM29BL160 type synchronous flash
PM-565 Features:
• 4Mhz reference Crystal Oscillator with large landing pads for easy value change
• BDM and Nexus 50 pin Development port connectors
• POR and Hard Reset buttons
• Voltage Indicators
• Reset Indicator
• Reset Configuration Switch for clocking options, enabling external configuration of operating mode or programming
• Stack connectors mapped for signal functionality
CMD-5XX Motherboard Features:
• Standard fixed memory (buffered):
• 512K x 32 Sync. SRAM (100MHz), 1M x 32 Burst Flash EEPROM
• Two Configurable 32pin memory sockets for 32K to 2MByte EPROM with 8 or 16 bit wide data bus, Axiom Monitor installed standard
• PRU - Port Replacement Unit provided for MPC555 ports A, C, and D allow simulation of single chip port operation when expanded bus is operating
• MAP Switch - provides easy assignment of chip selects to ram and flash memory banks
• MODE Switches - 4 DIP switches to fully support Hard Reset Word Configuration options
• COM Switch - provide easy method of applying or isolating serial connections to RS232 transceiver
• COM1 - SCIA1 w/ RS232 type DB9-S Connection
• COM2 - SCIA2 w/ RS232 type DB9-S Connection
• COM3, 4 - Not applied on MPC555
• CAN Ports - 2 CAN transceiver (PCA82C250) interfaced ports, 1 x 4 headers
• LCD Port - LCD Module Interface Connector w/ Contrast Adjust, Buffered and Memory Mapped
• KEYPAD and KEY Port - 16 Key or 20 Key interface, Debounced, Buffered, and Memory Mapped
• BUS Port - provides 32 data and 24 address or MPC555 ports A and D on 60 pin header
• CONTROL Port - Bus Controls for MPC555 ports on a 44 pin header
• QSM Ports - 2 Serial I/O ports with 16 pin socket headers
• MIOS Port - MDA, PWM, and MGP timer or I/O interface with 34 pin socket header
• TPU Ports - 2 Timing Processor I/O ports with 20 pin socket headers
• QADC Ports - 2 Analog I/O ports, one 20 pin and one 24 pin socket header
• INT Port - Interrupt or MPC555 SGP port I/O with 10 pin header
• POWER Port - Primary and standby power supply access port
• I/O Connectors in .1 grid, pin headers for bus and control provide easy ribbon cable connection for external connections. Socket headers provide easy wire connection to breadboard prototype area or with pin headers installed, will allow ribbon cable or wire wrap connections
• Mictor Logic Probe connectors for Bus and Control signals
• Large Prototyping Area (5 x 1.75 inch) with +5V and ground connection grids
• Breadboard Prototyping area (2.5 x 1.5 inch) for easy installation of test connections
• Power Indicators - Supply voltage indications for 5, 3.3, and 2.6V supplies
• Reset Switches - POR, Hard, Soft reset buttons
• User Indicators - 4 user indicators to provide user conceived visual response during testing
• CE certified class A as shipped with universal power supply
Other Specifications:
Power Supply - 6 to 20VDC Input, 300ma typical @ 9VDC
5.0V @ 2.5A output with 3.3V, and 2.6V regulated supplies
Board Size - 8 x 9.5 inch
Appendix B
Appendix B
Handy Board Specifications
Features:
• 52–pin Motorola 6811 microprocessor with system clock at 2 MHz
• 32K of battery-backed CMOS static RAM
• Two L293D chips capable of driving four DC motors
• 16 _ 2 character LCD screen
• Two user-programmable buttons, one knob, and piezo beeper
• Powered header inputs for 7 analog sensors and 9 digital sensors
• Hardware 38 kHz oscillator and drive transistor for IR output and on-board 38 kHz IR receiver
• 8-pin powered connector to 6811 SPI circuit (1Mbaud serial peripheral interface)
• Expansion bus with chip selects allows easy expansion using inexpensive digital I/O latches
Other Specifications:
Power Supply - 12 volt, 500 mA DC output
Internal 9.6V NiCad battery with built-in recharging circuit
Board Size - 4.25 x 3.15 inch
Appendix C
Appendix C
EPIC AMD™ Geode GX2 Low Power SBC - EPX-GX
Features:
• AMD Geode™ GX500@1.0W processor
• EPIC-compliant board
• 128 to 512MB of system PC2700DDR SDRAM supported in a 200-pin SODIMM socket
• Type I and II CompactFlash (CF) cards supported
• PC-compatible supports Linux, Windows® CE and XP embedded, plus other x86-compatible RTOS
• High-resolution video controller supports
• • Color panels supported with up to 18-bits/pixel
• • Panel resolutions up to 1280 x 1024
• • Backlight power supported
• • CRT supports 1600 x 1200 pixels
• 10/100 Mbps Intel PCI Ethernet controller
• 4 RS-232 serial ports with FIFO, COM1 & COM2 with optional RS-422/485 support
• Bi-directional LPT port supports EPP/ECP
• 24 bi-directional TTL digital I/O lines (WS16C48)
• Two USB 1.1 ports onboard
• MiniPCI connector for 802.11 a/b/g wireless module
• Floppy disk controller supports up to 2 drives
• Ultra DMA 66 EIDE hard disk controller
• Optional 12-bit A/D with up to 8 SE or 4 DI channels, with independent software programmable input ranges of ±5V, ±10V, 0-5V, and 0-10V
• AC97 Audio supports 6 channels (5.1 surround)
• PC/104 and PC/104- Plus expansion connectors
• AT keyboard controller and PS/2 mouse support
• GPS support via external serial module
• Activity LEDs onboard for visual status
• Two interrupt controllers and 7 DMA channels
• Three, 16-bit counter/timers
• -40°C to +85°C operating temperature range
• +5 volt only operation and low power
• Up to 2 minute reset on watchdog timer
• Real time clock, and power fail reset
• Small size: 4.5 " x 6.5" (115 mm x 165 mm)
Overview:
The EPX-GX is an AMD Geode 500@1.0W-based, EPIC-compatible single board computer (SBC). AMD Geode processors have extremely low power dissipation which allows fanless operation.
The EPX-GX supports 9 different functions providing a processor and I/O-intensive solution for demanding applications. Applications include test equipment, medical instruments, communications devices, transportation systems, military/COTS, data loggers, security,
robotics, semiconductor manufacturing instruments, and industrial control systems.
The board is configured with up to 512MB of PC2700 DDR SDRAM plus a CompactFlash (CF) memory socket. Also, a 10/100 Ethernet controller, video with CRT and flat panel interfaces, four serial COM channels, 24 digital I/O lines, 6 channels of AC97 audio, and the standard AT peripheral feature set are included.
The EPX-GX measures 4.5 x 6.5-inches (115mmx165mm) and is compliant with the EPIC (Embedded Platform for Industrial Computing) standard. It offers additional I/O expansion with PC/104 and PC/104-Plus connectors or with two high-speed USB 1.1 channels.
It also supports 2 floppy disk drives and two Ultra-DMA 33/66 IDE drives.
There is a socket for bootable Type I and II Compact-Flash cards. The EPX-GX2 also includes a socket for a miniPCI wireless 802.11 a/b/g card. Plus a connector is included to support a remote GPS receiver.
The board will operate from - 40° to +85°C without a requiring a fan, for rugged embedded applications. It is ideal for low-power, high-performance, battery-powered and portable applications.
Software Support:
Software - The EPX-GX is an x86-compatible SBC. It is designed to run both 16-bit and 32-bit x86 instruction set software and is compatible with Microsoft's Windows® CE and XP operating systems as well as the applications that run on them. It also supports Linux and other operating systems such as QNX or VxWorks. Its x86-PC software compatibility assures a wide range of tools to aid in developing and checkout of your application’s program.
Software Developers Kit - WinSystems offers the SDK4 software developers kit to provide the necessary hardware, software and cables to begin program development with the EPX-GX board. The configuration consists of an operating system, CD-ROM drive, a 20 GB or larger hard disk, a 1.44 MB high density 3.5-inch floppy disk, plus required cables and triple output power supply housed in an enclosure. This packaging permits easy access to the board, PC/104 modules and peripherals during program development.
Specifications:
Electrical
EPX-GX CPU AMD Geode 500@1.0W-based
PC/104 Interface: 16-bit, non-stackthrough
PC/104- Plus Interface: 32-bit PCI, non-stackthrough
Ethernet data rate: 10/100 megabits per second
USB Interface: Two USB 1.1-compliant ports
Serial Interface: 4 Serial channels with RS-232 levels plus RS-422/485 on COM1 and COM2
LPT Interface: Bi-directional LPT with ECP/EPP
Parallel Interface: 24 I/O lines, TTL compatible
UDMA66/33 EIDE interface: Supports 2 drives
Floppy Disk Interface: BIOS supports one or two 360K/720K/1.2M/1.44M drives
Vcc = +5V ±5% at 1.5 Amps typ.
System Memory: Addressing: Up to 512 Megabytes 200-pin SODIMM DDR memory
Solid State Disk: Device: One Type I or II CompactFlash card
Mechanical: Dimensions: 4.5" x 6.5" (115mm x 165mm)
Environmental: Operating Temperature: - 40°C to +85°C
Appendix D
Appendix D
VIA EPIA-EN12000EG Mini-ITX Motherboard with VIA C7 1.2GHz Specifications
Features:
• 52–pin Motorola 6811 microprocessor with system clock at 2 MHz
• VIA EPIA EN12000G 1.2GHz VIA C7 nanoBGA2 Fanless Processor
• 1.2GHz VIA Eden nanoBGA2 Fanless Processor Onboard
• VIA CN700 Chipset with Integrated VIA UniChrome Pro AGP Graphics with MPEG-2 Decoding Acceleration
• DDR2 533 SDRAM
• 1 PCI slot
• ATA 100/133 & 2 SATA ports Support
• VIA Vinyl 8 Channel Audio
• VIA IEEE 1394, 6 USB 2.0 ports & 2 COM ports
• VIA Gigabit Ethernet
• VIA TV Out (HDTV Resolution)
• LVDS/DVI (an add-on card is required)
• Mini-ITX Form Factor (170mm X 170mm)
• RoHS Compliant
Specifications:
|Processor |• 1.2GHz VIA Eden nanoBGA2 Processor |
|Chipset |• VIA CN700 North Bridge |
| |• VIA VT8237R Plus South Bridge |
|System Memory |• 1 DDR2 400/533 DIMM socket |
| |• Up to 1 GB memory size |
|VGA |• Integrated VIA Unichrome Pro AGP graphics with MPEG-2 decoding acceleration |
|Expansion Slots |• 1 PCI |
|Onboard IDE |• 2 X UltraDMA 133/100/66 Connectors |
|Onboard LAN |• VIA VT6122 GLAN Controller |
|Onboard Audio |• VIA VT1618 8-channel AC'97 Codec |
|Onboard TV Out |• VIA VT1625M HDTV Encoder |
|Onboard 1394 |• VIA VT6307S IEEE 1394 Firewire |
|Back Panel I/O |• 1 PS2 mouse port |
| |• 1 PS2 keyboard port |
| |• 1 VGA Port |
| |• 1 Serial port |
| |• 1 RJ-45 port |
| |• 4 USB 2.0 ports |
| |• 1 RCA port (S/PDIF or TV out) |
| |• 1 S-Video port |
| |• 3 Audio jacks: line-out, line-in and mic-in (Horizontal, Smart 5.1 Support) |
|Onboard I/O Connectors |• 1 USB connector for 2 additional USB 2.0 ports |
| |• 1 1394 connector for 1 1394 port |
| |• 2 SATA Connectors |
| |• 1 Front-panel audio connector (Mic-in and Line Out) |
| |• 1 Serial port connector for a second com port |
| |• 1 LPT connector |
| |• 1 CIR connector (Switchable for KB/MS) |
| |• 1 SIR pin header (IrDA 1.0) |
| |• 2 Fan connectors: CPU/Sys FAN |
| |• 1 SMBUS connector |
| |• 1 S/PDIF in connector |
| |• 1 S/PDIF out connector |
| |• 1 LVDS/TTL/DVI module connector (an add-on card is required) |
| |• 1 Component (YPbPr) video pin header |
| |• ATX Power connector |
|Operating System |• Windows 2000/XP, Linux, Win CE/XPe |
|Software Application |• VIA FliteDeck Utility |
| |• MissionControl-H/W Monitoring, Remote SNMP Management |
| |• FlashPort-Live BIOS Flash |
| |• SysProbe-Live DMI Browser |
|System Monitoring & Management |• CPU temperature reading, CPU voltage monitoring |
| |• Wake-on-LAN, Keyboard-Power-on, Timer-Power-on |
| |• Watch Dog Timer, FAN control |
| |• System power management, AC power failure recovery |
References
References
-----------------------
[[i]] Axiom Manufacturing. CMD-565 Motorola Oak Series Development Board Features. 4 November 2006.
[[ii]] Margin, Fred G. The Handy Board Technical Reference. 4 November 2006.
[[iii]] Gleason Research. The Handy Board System. 4 November 2006.
[[iv]] WinSystems. EPIC AMD™ Geode GX2. 29 November 2006.
[[v]] Mini-Box. VIA EPIA-EN12000EG Mini-ITX Motherboard. 4 November 2006.
[[vi]] Active Robots. Devantech SRF04 Ultra Sonic Ranger Module. 8 November 2006.
[[vii]] Acroname, Inc. Devantech SRF235. 10 November 2006.
[[viii]] Acroname, Inc. SensComp Instrument Package. 10 November 2006.
[[ix]] Acroname, Inc. Sharp GP2D05 IR Ranger. 10 November 2006.
[[x]] Acroname, Inc. Sharp GP2Y0A02YK IR Sensor. 10 November 2006.
[[xi]] Acroname, Inc. Hokuyo URG-04LX Laser Sensor. 10 November 2006.
[[xii]] Acroname, Inc. Devantech Compass. 10 November 2006.
[[xiii]] Bartolini, Daniel. Analog Devices ADXRS150 Angular Rate Sensing Gyroscope. 8 November 2006.
[[xiv]] Spark Fun Electronics. Gyro Breakout Board - ADXRS150. 10 November 2006.
[[xv]] US Digital, Inc. MA2 Miniature Absolute Magnetic Shaft Encoder. 8 November 2006.
[[xvi]] Digi-key. IC CONVERTER D/A 8BIT 16-DIP. 3 December 2006.
[[xvii]] Trident. POS Keypad GPA 400 PIN Pad. 12 November 2006.
[[xviii]] . Targus USB Numeric 19-Key Mini Keypad (Silver). 12 November 2006.
[[xix]] . Kensington Pocket KeyPad w/2-Port USB Hub. 12 November 2006.
[[xx]] Phidgets. PhidgetTextLCD 20X2 : Blue : Integrated 8/8/8 InterfaceKit. 12 November 2006. 1165288346205.241.141.184&IID=116
[[xxi]] Ituner Networks Corp. picoLCD 20x2 (OEM). 12 November 2006.
[[xxii]] TVI Electronics Online Store. Optrex Monochrome Graphic Series Displays. 12 November 2006.
[[xxiii]] TVI Electronics Online Store. Touch Screen LCD Module TM1B5BW. 15 November 2006.
[[xxiv]] Acroname, Inc. Devantech SRF04 Ranger. 10 November 2006.
[[xxv]] Robot Electronics, Inc. SRF04 - Ultra-Sonic Ranger Technical Specification. 8 November 2006.
[[xxvi]] Robot Electronics, Inc. CMPS03 - Robot Compass Module. 8 November 2006.
[[xxvii]] Analog Devices, Inc. ADXRS150 - Angular Rate Sensor ADXRS150. 8 November 2006.
[[xxviii]] Crystalfontz America, Inc. CFAH2004A Standard LCD Modules. 12 November 2006.
-----------------------
LCD Display
HC-LCD
USB
ADC
USB
RS 232
9VDC Power Supply
RFID Reader
RW-310
Wheelchair
Joystick
[pic]
Gyroscope
ADXRS150
Compass
R117
Ultrasonic Sensors
S4F04
Keypad
HC-KP
Controller
Mini-ITX
12Vreg
Joystick
DC Jack
24V Battery
Gyroscope
DAC
Left/Right
5.9V ± 1V
5.9V ± 1V
Forward/Reverse
[0:7]
[0:7]
ADC
ADC
DB15
Motor Control Box
RS232
Controller
RFID
Reader
5Vreg
Compass
9Vreg
Sonar Array
(x13)
Echo
[0:12]
2
1
Trigger
[0:12]
3
LCD
Display
USB
USB
Keypad
4
5
9
7
8
10
1 Controller
2 LCD
3 Keypad
4 Compass
5 Gyroscope
6 Modified joystick
7 Motor Control Box
8 Batteries
9 Sonar
10 RFID Reader
6
Calculate path from start to end
Determine critical obstacles
Recalculate path from current location
Left/right wheel control for intended
speed/turn
Starting position/final destination
Current location
Distance to obstacles
Magnetic orientation
Gyroscope orientation
Outputs
Processing
Inputs
Left/right wheel control
Sensor stimuli
Input information (interfacing)
Location information (debugging)
Wheelchair
Row of unique RFID tags
Row of identical RFID tags
Path of traversal
Doorway
PWM
ADC
ADC
................
................
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