Proposal for the NASA Reduced Gravity Student Flight Program



Investigating the use of tactile feedback systems to enhance spatial awareness in altered-gravity environments

A proposal for the August 1999 NASA Reduced Gravity

Student Flight Opportunities Program

Submitted: April 2, 1999

Purdue University School of Electrical and Computer Engineering

Point of Contact:

Ryan J. Casteel

casteel@ecn.purdue.edu

(765) 495-1737

Abstract

Spatial disorientation (SD), the incorrect perception of attitude, altitude, or motion of one’s own body, aircraft, or spacecraft, is a major problem facing military aviatiors and NASA astronauts. This problem costs the Department of Defense $300 million per year in lost aircraft and has caused astronauts to have motion sickness during shuttle missions.

This project proposes the use of a tactile feedback system to enhance spatial awareness. The proposed system will utilize a phenomenon call sensory saltation to simulate the feeling of someone drawing directional lines on the user’s back. Specifically, it will examine how the sense of touch can be engaged in a natural and intuitive manner to allow for the correct perception of position, motion and acceleration of one's body, an aircraft, or spacecraft. The system consists of an array of 3x3 vibrators attached to a backpack. To our knowledge, no experiments using sensory saltation have been conducted in a microgravity environment. By eliminating the perception of gravity in the test environment, it will be possible to more accurately measure the effectiveness of the tactile feedback system.

Successful implementation of this technology will also find applications in other areas. This system can provide better orientation awareness for astronauts during Extra-Vehicular Activities (EVAs), navigational cues to Special Forces operators during HALO (High-Altitude Low-Opening) parachute insertions, and silent communication for military units on the ground and in diving environments. Additionally, this system can be used for navigational assistance for the blind by using GPS-assisted directional finding.

Table of Contents

Background and Overview 4

Test Objectives 7

Test Description 8

In-Flight Test Procedures 11

Equipment Description 12

Structural Load Analysis 15

Parabola Requirements, Number, and Sequencing 19

Test Support Requirements, Ground and Flight 19

Data Acquisition System 19

Test Operating Limits 20

Proposed Manifest 20

Photographic Requirements 20

Hazard Analysis 20

Safety Certification 21

Outreach Program 22

Publicity 23

Official Verifications 23

Additional Support 23

References 24

Appendix A 25

Appendix B 26

Appendix C 27

Appendix D 28

Appendix E 29

Appendix F 30

Purdue Microgravity Flight Team

Ryan Casteel --Junior / Electrical Engineering

Jennifer Glassley --Junior / Electrical Engineering

Joachim Deguara --Sophomore / Electrical Engineering

Ryan Traylor --Sophomore / Electrical Engineering

Adrian Lim --Sophomore / Mechanical Engineering

Academic Institution/Department Involved

Purdue University

School of Electrical and Computer Engineering

West Lafayette, IN 47907

Supervising Faculty Member

Dr. Hong Tan

hongtan@ecn.purdue.edu

Background and Overview

In aviation, spatial disorientation (SD) is the incorrect perception of attitude, altitude, or motion of one’s own aircraft relative to the earth or other significant objects. It is a tri-service aviation problem that annually costs the Department of Defense in excess of $300 million in lost aircraft. Spatial disorientation is the number one cause of pilot related mishaps in the Navy and the Air Force. The typical SD mishap occurs when the visual system is compromised by temporary distractions, increased workload, reduced visibility, and most commonly, g-lock [1]. G-lock occurs when the pilot undergoes a high-g maneuver and temporarily blacks out behind the stick. Frequently, after pilots recover from the distraction, they rely on instinct rather than the instrument panel to fly the aircraft. Often times, the direction the pilot thinks he or she is traveling is much different from the actual direction. Additionally, the role of vision on orientation in zero-g has been a major concern for NASA astronauts. Significant work in visual reorientation illusions has been done by NASA’s Neurolab, specifically Dr. Charles Oman, aboard several Spacelab missions during the last 15 years [2].

This document proposes a new approach to examining this problem, namely how the sense of touch can be engaged in a natural and intuitive manner to allow for the correct perception of position, motion and acceleration of one's body, an aircraft, or spacecraft. The proposed system will utilize a phenomenon call sensory saltation to simulate the feeling of someone drawing directional lines on the user’s back. If an astronaut or pilot wears such a system, they may suffer less frequently from spatial disorientation.

The idea of utilizing the sense of touch to replace vision or audition (i.e., sensory substitution) is not new. In fact, numerous devices have been developed for persons with visual or auditory impairments (e.g., the Optacon, a reading-aid for the blind, and Tactaid VII, a hearing aid for the deaf). It is conceivable that such devices can be employed under conditions where visual / auditory sensory channels are overloaded or information received via visual / auditory channels are distorted. However, devices like the Optacon require extensive user training and high level of concentration during its use. In addition, it requires the use of the fingertip, which would interfere with many manual tasks. In contrast, the tactual[1] display[2] system we propose to use has many advantages. It uses the part of the body that is not usually engaged by other tasks (i.e., the back). It requires no user training. It delivers directional information that is easy to interpret (i.e., in the coordinate frame of the user's body). The importance of solving the spatial disorientation problem can be derived from its history.

History of Spatial Disorientation

Spatial disorientation and situational awareness (SA) issues were recognized when humans began flying more sophisticated aircraft, particularly during the Vietnam War. Early solutions to the SA/SD problem focused on better visual displays. Early medical research proved that SA and SD were directly influenced by the interrelationships of vision, vestibular (inner ear), and somatosensory (skin, joint, muscle) sensors [3].

As aviation advanced, spatial disorientation became more of a problem. The Navy reports that from 1980-89, disorientation was listed as the definite cause in accidents that resulted in loss of 38 lives and 32 aircraft. During Desert Storm, four out of eight single pilot aircraft and three out of six helicopter non-combat mishaps were due to spatial disorientation. [11] General Rufus DeHart, a Command Surgeon in the USAF Tactical Air Command, has reported that "the most significant human-factors (HF) problem facing the TAF today is spatial disorientation (SD), followed by high-G loss of consciousness. Of all HF mishaps, 30% in the F-16 and 19% in the F-15 and F-4 are due to SD". [4]

Currently, the U.S. military loses around 20 aircraft and 20 officers per year as a result of spatial disorientation mishaps. Additionally, the Federal Aviation has reported that SD is a cause or factor in 16% of fatal general aviation accidents. Other countries have had similar problems. The Royal Air Force reports that 15% of its helicopter accidents and 33% of its helicopter fatalities result from SD. The Dutch military has lost nearly 10 aircraft in the last 10 years from SD-related mishaps. Canada has lost six CF-18’s because of spatial disorientation. [3]

Spatial disorientation has been a continuing problem for NASA as well. Around 1973, astronaut Owen Garriott explained to Dr. Charles Oman’s research team of his experience with space sickness on Skylab. In smaller spacecraft, space sickness had not been a problem since the astronauts had very little room to move about. The new space shuttle would allow the astronauts to move about and possibly experience conflicting cues from their eyes, ears, and joints; hence, space sickness became an immediate concern. Dr. Oman and several colleagues wrote a successful proposal to develop a set of vestibular experiments for the Spacelab module. While waiting for the completion of Spacelab, they tried the experiments aboard the KC-135A. They learned about visual reorientation illusions, and begin to train the astronauts to be ready for them in orbit. Soon after they began flying in 1981, space sickness quickly became a well-publicized problem. Dr. Oman was able to fly experiments aboard several Spacelab missions during the last 15 years and has found some very interesting results. Specifically, “crewmembers became more dependent on visual and tactile cues to their self-rotation [2].”

Transistion???

Sensory Saltation

The "sensory saltation" phenomenon was discovered in the1970’s in the Cutaneous Research Laboratory at Princeton University. (The word “saltation” is Latin for “jumping”.) In an initial setup that led to the discovery of this phenomenon, three mechanical stimulators were placed with equal distance on the forearm (see Figure 1). Three brief pulses were delivered to the first stimulator closest to the wrist, followed by three more at the middle stimulator, followed by another three at the stimulator farthest from the wrist. Instead of feeling the successive taps localized at the three stimulator sites, the observer is under the impression that the pulses seem to be distributed with more or less uniform spacing from the site of the first stimulator to that of the third. The sensation is characteristically described as if a tiny rabbit was hopping up the arm from wrist to elbow; hence the nickname “cutaneous rabbit”.

[pic]

Figure 1. A Norwegian artist's interpretation of the "sensory saltation" phenomenon. [7]

We have constructed a 3-by-3-stimulator array that allows the simulation of "rabbit" paths in many directions. When this display is placed on the back, it simulates the sensation of someone drawing a directional line on the user's back. One might wonder whether there is enough spatial resolution in the back of the torso. Although it is true that the back is much poorer in spatial resolution as compared to, say the fingertip, it is well compensated by the much larger area that the tactual display can cover. Furthermore, the perceived taps in-between actual stimulators are perceptual illusions (see open circles in Figure 2. stimulation vs. sensation); thus their spatial resolution may not necessarily be limited by the actual receptor densities in the skin of the back. Another important advantage of our tactual directional display, as compared to visual displays on an instrument panel, is that the user does not have to look for it — s/he simply feels it.

Figure 2. Stimulation vs. sensation [12]

Research on the sensory saltation phenomenon has concentrated on the quality of lines that can be perceived [5]. Although some researchers have speculated on the neural mechanism of this phenomenon (ref), it is still not well understood how and why this illusion happens. The Reduced Gravity Student Flight Opportunities Program provides a unique opportunity for us to observe whether this illusion is robust under altered-g conditions, thus gaining some insight into whether this sensory illusion interacts with the visual system, other components of the tactual system (e.g., kinesthesis), and the vestibular sensory system.

Applications

Tactile technology can be expanded beyond solving SA/SD problems into areas such as navigation, communication, alarms and indicators, and training and simulation.

Tactile technology can be used to reduce mission failure, aircraft loss and pilot loss due to pilot disorientation, and to enhance pilot performance by simplifying the flight task. Currently the only accurate sensory information available to pilots concerning their attitude and motion is visual interpretation of instruments or outside reference to the horizon. By integrating the tactile directional display with existing systems, pilots can be steered in the right direction when they fall off course. Ideally, the pilot could maneuver the aircraft using tactile displays in the complete absence of visual cues.

Tactile technology utilizing sensory saltation can enhance EVA safety and effectiveness. Having a correct perception of their own position and motion will allow astronauts to work even more productively and confidently in space.

For military Special Operations, tactile displays provide the advantages of low signature, a silent form of communication, reduction of information overload, a backup to other senses, a good representation of 3-D space, and the utilization of an otherwise unused sense. For example, if a team is attacking target X at night, the leader can give silent commands for attack strategy: a pulse going around the operator’s back could mean to “surround the building.” Also, if a team is performing a High Altitude Low Opening parachute insertion in the pitch black of night, a system integrated with a Global Positioning System could allow all operators too easily find the on-ground rendezvous point [1].

Application of a tactile system for the blind is evident. With a GPS, the system could help guide the user through unfamiliar territory, and perhaps one day to even drive a car. Even for the non-blind, a wearable tactile display could guide the user through an unfamiliar building to find a room or help a tourist navigate through an unfamiliar city [12].

Test Objectives

The goals of our proposed experiment are (1) to examine if the "sensory saltation" illusion is robust under altered-g conditions, and (2) to gain some insight into whether this illusion interacts with the vestibular sensory system. Specifically, the perceived direction of various directional signals, as well as the perceived strengths of such signals, will be documented.

Test Description

Setup

This experiment will consist of one team member serving as a test subject and one team member running the experiment and collecting data. The test subject will put on the backpack containing the tactual directional display and its associated electronics (see Figure 3). The experimenter will set up the experimental conditions, and document the experiment with a video camera and data collection sheets.

Written Test Procedure Figure 3: Experiment Backpack

The experimenter will choose one of four signals-- up, down, right, or left--by selecting one of the four buttons on a keypad mounted on the backpack. The ordering of the four signals will be randomized. The other team member (test subject) will not be informed as to which of the four signals was selected. The test subject then will experience the directional signals delivered to his/her back by the tactual directional display mounted on the side of the backpack towards his/her torso. The subject will verbally report the sensations to the experimenter. The results will be documented on video camera and on data collection sheets by the experimenter.

The subject will be asked to experience and report his/her perception of the directional signal relative to his/her torso. For example, the sensation of something "crawling up the spine" will be reported as "up". The sensation of something "going down the spine" will be reported as "down". Reports of "left" and "right" signals will also be based on the orientation of one's own torso. In order to maximize the duration of data collection during the flight, all team members will have an opportunity to experience the four signals and their associated directions before the flight.

The selected signal is repeatedly delivered to the subject's back while his/her body is positioned at different orientations relative to the aircraft. These orientations range from lying down, sitting, floating in any direction, and free-floating with the subject's eyes closed. This test will include all four ranges of gravity: two times normal gravity, normal gravity, zero gravity, and the transition periods of gravity.

Once all possible cases are examined, the experimenter will select another signal at random, and the experiment will begin again. This will continue until all possible cases are examined. If time remains and both team members are capable, the roles will be reversed, and another set of data will be collected.

These test cases can be seen in Table 1 for Flight #1 and Table 2 for Flight #2. Table 1 consists of experiments investigating the effects on the perceived direction caused by body orientations and eyesight. Table 2 consists of experiments that investigate the effects caused by body motions. The ordering of the signals selected by the experimenter will be randomized during the actual flights.

In-Flight Test Case Example

An example of a complete in-flight test scenario is given below. The same procedure is summarized in the next section entitled “In-Flight Test Procedures” in the form of a checklist.

Just before the KC-135 begins the parabolas, the test subject puts on the backpack containing the sensors and the microcontroller. The experimenter turns on the camcorder, ensures a new videotape is loaded, sets the recording mode, and begins recording. The microcontroller is turned on. Finally, any outreach materials are setup.

At the commencement of the testing, the experimenter selects the upward-traveling pulse pattern, which will begin to cycle repeatedly. The experimenter then verifies the chosen signal with the LED display. The test subject positions him/herself sideways with the respect to the plane and the experimenter documents this orientation and other related data. The test subject then describes the perceived signal felt during the period of zero-g, which the experimenter then documents. This procedure is repeated for the signal felt during the transition between zero and positive 2g, and during positive 2g. When responses to all three conditions are received, the test subject then moves into the next orientation, which is lying horizontally face up with their feet pointing forward. The experimenter will once again ask for the perceived signal in all three gravity states. This test will continue for the last three cases of sitting vertical facing forward, spinning in any direction, and free-floating with the eyes closed. Once all five cases are completed, the experiment is repeated for the downward, right, and left-traveling pulse patterns. Finally, all outreach activities will be performed in the time remaining.

Upon completion of the test, all outreach materials will be stowed away. The microcontroller and the camcorder are stopped and turned off. The test subject removes the vest and microcontroller, and all remaining materials are put away. The team then prepares for landing.

Table 1: Test Case Sequencing for Flight #1

|FLIGHT #1 |

|Parabolas |Signal |Test |

|1-2 |Up |Traveling sideways with respect to the plane |

|3-4 |Up |Lying horizontal facing up with feet forward |

|5-6 |Up |Sitting vertical facing forward |

|7-8 |Up |Spinning any directions |

|9-10 |Up |Eyes closed any body orientation |

|11-12 |Down |Traveling sideways with respect to the plane |

|13-14 |Down |Lying horizontal facing up with feet forward |

|15-16 |Down |Sitting vertical facing forward |

|17-18 |Down |Spinning any directions |

|19-20 |Down |Eyes closed any body orientation |

|21-22 |Right |Traveling sideways with respect to the plane |

|23-24 |Right |Lying horizontal facing up with feet forward |

|25-26 |Right |Sitting vertical facing forward |

|27-28 |Right |Spinning any directions |

|29-30 |Right |Eyes closed any body orientation |

|31-32 |Left |Traveling sideways with respect to the plane |

|33-34 |Left |Lying horizontal facing up with feet forward |

|35-36 |Left |Sitting vertical facing forward |

|37-38 |Left |Spinning any directions |

|39-40 |Left |Eyes closed any body orientation |

Table 2: Test Case Sequencing for Flight #2

|FLIGHT #2 |

|Parabolas |Signal |Test |

|1-2 |Right |Strapped down to the floor |

|3-4 |Right |Traveling backward with respect to the plane |

|5-6 |Right |Moving in a forward direction |

|7-8 |Right |Moving in a sideways direction |

|9-10 |Right |Free Motion |

|11-12 |Down |Strapped down to the floor |

|13-14 |Down |Traveling backward with respect to the plane |

|15-16 |Down |Moving in a forward direction |

|17-18 |Down |Moving in a sideways direction |

|19-20 |Down |Free Motion |

|21-22 |Left |Strapped down to the floor |

|23-24 |Left |Traveling backward with respect to the plane |

|25-26 |Left |Moving in a forward direction |

|27-28 |Left |Moving in a sideways direction |

|29-30 |Left |Free Motion |

|31-32 |Up |Strapped down to the floor |

|33-34 |Up |Traveling backward with respect to the plane |

|35-36 |Up |Moving in a forward direction |

|37-38 |Up |Moving in a sideways direction |

|39-40 |Up |Free Motion |

In-Flight Test Procedures (Check List)

Initial Setup

_____1. Test Subject puts on backpack containing sensors and microcontroller.

_____2. Turn on Camcorder.

_____3. Ensure new Videotape is loaded.

_____4. Set Record mode on Camcorder.

_____5. Start Recording on Camcorder.

_____6. Turn on Microcontroller.

_____7. Setup any Outreach Materials.

Testing

_____8. Experimenter Selects Desired Signal on Microcontroller Keypad.

_____9. Verify Signal on LED display.

____10. Test Subject moves into orientation for specific parabola.

____11. Experimenter documents orientation and other related data.

____12. Test Subject describes signal felt during zero-g.

____13. Experimenter documents response.

____14. Test Subject describes signal felt during transition between zero and +2g.

____15. Experimenter documents response.

____16. Test Subject describes signal felt during +2g.

____17. Experimenter documents response.

____18. Repeat steps 9-16 for new test condition.

____19. When all test conditions are examined, choose new signal.

____20. Repeat steps 8-17 for new signal.

____21. Upon completion and time remains, repeat any tests on which further data is desired.

____22. Do any additional Outreach activities.

Test Conclusion

____23. Put away all Outreach materials.

____24. Turn off the Microcontroller.

____25. Stop Recording on Video Camcorder.

____26. Turn off Camcorder.

____27. Stow all remaining materials

____28. Test Subject removes vest and microcontroller.

____29. Prepare for landing.

Equipment Description

Overview

The hardware used to generate the

directional signals can be described by four

functional blocks. These blocks are the

control box, signal generator, vibrator driver

circuit, and display as shown in Figure 4.

The control box utilizes a keypad to input the

desired directional signal. Inputs are decoded

by the signal generator and the resulting on/off

pattern is supplied to the vibrator driver circuit.

This circuit accomplishes three tasks. First,

it supplies a 220 Hz sinusoidal signal, and then

it acts as a power amplifier to produce oscillations

in the vibrators (tactors). Finally, a tactile display

is implemented with a 3x3 array of vibrators

attached to a backpack. All of this hardware is enclosed

in a box of length 11.02 inches, width of 7.87 inches, and

depth of 2.95 inches. (See Figure 5)

Figure 4: Functional Flowchart

(Drawn by: Ryan Traylor)

Figure 5: Hardware Enclosure Box

Control Box

The first hardware component is the control box, which consists of a keypad and certain encoding components. Each button on the sixteen-key keypad is assigned a binary number from zero to fifteen. Encoding hardware, the 74C922J integrated circuit, provides a binary output corresponding to the particular button that is pressed on the keypad. The binary output is of a form that can be read and interpreted by a microcontroller used for signal generation. The 74C922J also provides an active high strobe to its Data Available pin whenever a key is pressed. This feature is later utilized as an interrupt to the microcontroller to allow another pattern to be generated. The schematic diagram for the control box circuit is shown in Figure 6.

[pic]

Figure 6: Control Box Circuit

(Drawn by: Ryan Traylor)

Signal Generation

The next module in the hardware model is the signal generation performed by a microcontroller. The specific microcontroller chosen for this task is the PIC16C84 8-bit CMOS microcontroller with EEPROM memory (Microchip Inc., AZ). Ease of programming and its 13 I/O lines make this chip an ideal choice. The PIC16C84 (PIC) is programmed to read a four bit number supplied by the control box and convert it into a directional pattern signal employing nine output pins. An interrupt is generated using the Data Available pin from the control box. The interrupt signal is inverted and then supplied to the PIC’s RESET pin. An inverter is necessary because the PIC has an active low RESET and the interrupt signal is active high. Upon reset, the PIC executes routines, which select the appropriate pattern chosen by the keypad, and applies the corresponding signals to the nine output pins. The schematic of the microcontroller portion of the hardware is shown in Figure 7 along with the pin assignments of the pattern array located on the backpack. The PIC is able to control which outputs are turned on for specified amounts of time and what delay should be inserted between each signal. A carefully orchestrated sequence of pulses and delays directed by the precise timing of the PIC creates the sensation of a line being drawn on the user’s back.

[pic]

Figure 7: Microcontroller Schematic

(Drawn by: Ryan Traylor)

Vibrator Driver Circuit

Since the PIC can only supply gated high or low pulses, the output pins cannot be used directly to supply the 220 Hz sinusoidal wave to the vibrators. An intermediate device, the vibrator driver circuit, is needed to accomplish this task. The driver circuit’s main function is to supply an amplified oscillating signal to the vibrators when prompted by the PIC to do so. The circuit consists mainly of a power supply, a 220 Hz oscillator, and nine 16-Watt bridge amplifiers. When the driver circuit receives a high signal from the microcontroller, it responds by supplying a 220 Hz oscillating signal to the corresponding vibrator in the vest. A schematic of the bridge amplifier is shown in Figure 8.

Figure 8: 16W Bridge Amplifier [8]

Tactile Display

The final piece of hardware is the tactile display consisting of a collection of nine vibrators attached to a backpack. The vibrators are placed on a regular 3x3 grid with an eight centimeter spacing between adjacent vibrators (see right panel of Figure 7). The vibrators are made of flat speakers, four inches in diameter, modified for this application (Audiological Engineering Corp., MA). The driver circuit’s outputs also control a small array of LED’s set up in the same arrangement as the vibrators on the vest. This secondary display is used by the experimenter to visually determine what directional pattern the user is experiencing.

Tactor locator system issues:

• Tactor type used

• One size does not fit all

• Material constraints

• User flexibility and movement (diver vs. pilot)

• Cabling and external interface

• Existing vs. custom systems

• Ease of use and related human factors issues

Structural Load Analysis

The device has been designed to be contained inside a backpack. In this case, since the device is not restrained such as bolted to the ground of the airplane, its only loading will be its own weight. The following calculation and explanation summarize the stress-strain relations and the safety of the proposed device.

A= 11.02 in

B= 7.87 in

C= 2.95 in

Figure 9: Dimensions of the Flame Retardant Plastic Cases and Aluminum panel [13].

Mass of Device

Mass of 1598 ABS Flame Retardant Plastic Instrument Cases

= 0.678 kg

=1.495 lbf

Mass of Aluminum Panels

= 2 ( 0.064 in ( 7.87 in ( 2.95 in ( 0.1 lbf/in3

= 0.297 lbf

Mass of Battery

=2.2 lbf

Mass of Inner Component

= 0.194 kg

= 0.428 lbf

Mass of Vibrators

= 9 ( 0.031 kg

= 0.615 lbf

Total Mass of Device (Md)

= 5.035 lbf

Factor of Safety (FS)

FS = (failure load) / (allowable load)

In this analyses, FS = (yield strength) / (maximum load)

Assumptions

1. The contribution of thermal expansion to the stress analyses is negligible.

2. The thickness is uniform throughout the ABS Flame Retardant Plastic Instrument Cases.

3. All screws are significantly stronger than the casing they are securing and will not deform.

4. The forces exerted by the entire device are evenly distributed to the 2 belts that support the backpack.

5. The mass of backpack is negligible.

6. The loading on the plastic casing is uniformly distributed throughout the surface area.

Analysis

Figure 10: A small portion of the thin plastic plate experiencing uniform stress [6].

Loading

The device is approximately stress- and strain-free during the micro-gravity period. However, as soon as the airplane starts to accelerate upward, the device will experience a large deceleration, which causes a loading onto the surface of the plastic casing. The following calculation and explanation depict the worse case scenario (an acceleration of 6g) to ensure the safety of the device.

(Fy = N – mg = m(6g)

N = 7mg = 35.25 lbf

By assumption (6), the worse loading of the plastic casing is the loading on the smaller surface area (B(C).

Stress = (

Strain = (

( = N/A = 35.25 lbf / (7.87 in ( 2.95 in) = 1.518 psi

The followings are generalized Hooke’s Law for isotropic materials:

Modulus of Elasticity = E

Poisson’s Ratio = (

Shear Modulus = G = E / 2(1+()

(x = [E / (1+()(1-2()][(1-()(x + (((y +(z) – (1+()(((T)]

(y = [E / (1+()(1-2()][(1-()(y + (((x +(z) – (1+()(((T)]

(z = [E / (1+()(1-2()][(1-()(z + (((x +(y) – (1+()(((T)]

Since the loading is only on the surface, (x and (y does not apply to the system.

(x = 1/E [ (x - (((y + (z)] + ((T

(y = 1/E [ (y - (((x + (z)] + ((T

(z = 1/E [ (z - (((x + (y)] + ((T

From the above conclusion and by assumption (1)

(x = (-((z)/E

(y = (-((z)/E

(z = (z/E

Considering the mechanical properties of plastics:

Modulus of Elasticity, E = 0.35 – 0.4 ksi

Poisson’s Ratio, ( = 0 – 0.4

Strains in all directions have magnitudes of 10–3 or less. Thus we can expect an extremely small percentage of deformation on the plastic surface of out device during the upward acceleration. Besides, bolts supporting the lower and upper cases will be used to secure the inner components in place. This significantly decreases the elasticity of the lower and upper plate, which makes the deformation negligible.

Internal Loading

The internal components in the plastic casing will exert a force of 2.568 lbf when it is accelerated at 6g. Compared to the compressive/tensile strength of the plastic (6 ksi < ( y < 8.5 ksi), this loading becomes insignificant and thus will not deform the casing. Moreover, the stability of the casing is aided by the backpack that embraces the entire device.

Belt of Backpack

Figure 11: Loading of the backpack

(Drawn by: Adrian Lim)

By assumption (4) and (5),

(F = 2T – mg = m ( (6g)

Tmax = 7/2 mg = 17.623 lbf

For a belt cross-sectional area of A in2

(max = Tmax / A = 17.623 / A lbf/in2

Considering the mechanical properties of nylon:

Yield strength, (y = 8.0 ksi

Ultimate strength, (u = 11.0 ksi

The minimum cross sectional area for the belt has to be 2.203 ( 10-3 in2. The belts can withstand the force exerted in an acceleration of 6g as long as the cross sectional areas are above the minimum value, e.g. A = 0.75 in2.

Conclusion

The structural configuration of the device has been chosen so that maximum stresses in the components do not exceed the allowable stress. When loads are considered, the maximum applied load does not exceed, and is much less than, the allowable load (ultimate strength). The results (300 < FS < 400) of this analysis are well above the normal range of values for the normal factor of safety 1.3 – 3.0 (Craig, pg. 65, 1996). There is no likelihood that failure will result.

Parabola Requirements, Number, and Sequencing

Due to the nature of this experiment, no special parabola sequencing is necessary. Despite the fact that this experiment was designed around a forty-parabola flight, the procedure can be easily altered on the fly. Data will be collected during each parabola and in the transition period between cycles. This permits useable data to be obtained on any number of parabolas.

Test Support Requirements, Ground and Flight

The experiment will not require any major ground or flight assistance from the Johnson Space Center Reduced Gravity Office. However, we may need assistance in setting up and mounting our data collection cameras.

Data Acquisition System

No automated system will be utilized for data collection. Instead, video coverage will provide real-time data documentation.

The experimenter is responsible for documenting all of the comments stated by the test subject. In addition to the checklist (see section "In-Flight Test Procedures"), the experimenter will be provided with specific data collection sheets (see Appendix A) allowing an easier method of data documentation. These categories will consist of the orientation of the person, the person’s direction of movement (if any), the actual signal sent, the perceived signal, the state of altered gravity of the airplane, the perceived strength of the signal, and any extra comments the subject may have.

A video camera will be utilized to help document all test subject comments and corresponding orientations. This camera will be mounted within the aircraft to provide the experimenter more freedom of movement and activity.

The data collection sheets will then be examined along with the video recordings of the experiments for off-line data analysis.

Test Operating Limits

Our calculation on structural load analysis indicates that the equipment is extremely safe to bring aboard the aircraft. The temperature limitations on all of the important electronic components fall into the range of 0(C to 70(C. The multiplexer (CD4053) has temperature ranges from –65(C to 150(C [9] and the amplifiers have a temperature range from 0(C to 70(C [8], but for safety we have provided a heat sink. The PIC chip (which tells which channel to drive) has a range of –40(C to 85(C [14]. The Oscillator (XR2206) has and range from –55(C to 125(C. [10]. The board has been designed to accept a load from 9 to 15 volts, which complies with our 12-volt battery.

Proposed Manifest

Equipment (enclosed in a backpack)

Extra Batteries (2)

Video Camcorder

Video Tapes (4)

Data Collection Sheets

Outreach Materials (to be determined upon proposal acceptance)

Photographic Requirements

As stated in the In-Flight Data Collection section, a Video Camcorder will be utilized to help document all test subject comments and orientations. Still cameras will be brought aboard and will be used for personal photographs only. Any photographs taken by the zero-g office would be appreciated.

Hazard Analysis

The electronic hardware and its enclosure have been designed to withstand a 6-g acceleration, which is well within the expected range of accelerations. Because the vibrators hug close to the test subject’s body, they should be given consideration in the hazard assessment. The vibrators produce a ( 10 V peak-to-peak signal. If a high output occurs, the user won’t feel more intense pulses; instead, the output will be clipped. There is no chance of the vibrators producing a signal of any higher voltage that +10V. A 12-Volt lead acid gel cell battery furnishes the main source of power. It sealed battery and there will be no possibility of acid leakage.

If any electrical hazard is identified, the battery can be electrically isolated from the main circuitry by pressing a “panic button” conveniently located on the hardware enclosure. In addition, the backpack and the box will be constructed out of flame retardant materials. The box is designed to reduce hazard with standard insulated wires and safe contacts with heat-shrink wrap. The circuitry has also been designed so that there are no hazards of being shocked.

Safety Certifications

The signed safety certifications are enclosed in Appendix F.

Outreach Program

(See letters in Appendix B)

An extensive outreach program, designed to reach people of all ages, has been designed around this proposal. The following is a summary of these outreach activities:

Lower School

Oakland Elementary School in Lafayette, IN has agreed to participate in our outreach program. The plan is to do a presentation about our project to selected students before the end of the school year. Fourth and fifth grade students will give us feed back on the presentation and we would discuss the effects of reduced gravity and suggest other potential projects for the program. The students will let us know what types of experiments that they want us to fly for them aboard the aircraft, should our proposal be selected. In the fall, we’ll do a follow-up presentation where we’ll present video footage of the flight to the students and also let them know how their experiments went.

Middle School

Sunnyside Middle School in Lafayette, IN has agreed to participate in our outreach program. The plan is to do a presentation about our experiment and technology to selected students before the end of the school year. The students will let us know what types of experiments that they want us to fly for them aboard the aircraft, should our proposal be selected. In the fall, we’ll do a follow-up presentation where we’ll present video footage of the flight to the students and also let them know how their experiments went.

High School

Jefferson High School in Lafayette, IN has agreed to participate in our outreach program. The plan is to do a presentation about our experiment and technology to selected students before the end of the school year. The students will let us know what types of experiments that they want us to fly for them aboard the aircraft, should our proposal be selected. In the fall, we’ll do a follow-up presentation where we’ll present video footage of the flight to the students and also let them know how their experiments went.

Undergraduate

We will be setting up a display in the Materials Science and Electrical Engineering Building at Purdue University. Engineering students of all ages as well as Purdue visitors will be able to see our project.

Museums

The Imagination Station in Lafayette, IN has agreed to participate in our outreach program. The plan is to do a workshop for visitors of all ages in the spring and fall. It will be for community interest and will provide for significant feedback opportunity.

Publicity

(See letters in Appendix C)

(Rick Dawson – Channel 8)

Decatur Herald and Review

The main newspaper for the city of Decatur, IL writes that it is especially interested in providing first-time coverage of the Program.

Purdue Exponent

The school newspaper of Purdue University writes that it would excitedly cover the story should our proposal be selected.

Official Verifications

(See letters in Appendix D)

The following letters are included as requested by the Texas Space Grant Consortium:

Letter from Dean Richard Schwartz

The Dean of Engineering at Purdue University pledges his support for the project.

Letter from Dr. Kent Fuchs

The Head of the School of Electrical and Computer Engineering at Purdue University pledges his support for the project.

Letter from Dr. Hong Tan

Our faculty advisor explains that the Purdue students involved will receive academic credit for the project.

Additional Support

(See letter in Appendix D)

Letter from Jerry Ross

Senior EVA Astronaut Jerry Ross writes that he enthusiastically supports the project and is very interested in the applications resulting from this technology.

References

[1] Naval Aerospace Medical Research Laboratory

TSAS: Accurate orientation information through a tactile sensory pathway in aerospace, land, and sea environments.

Available:

[2] Oman, Charles M.

“Principal Investigator: Roles of Visual Cues in Microgravity Spatial Orientation”. Meet: Charles M. Oman, Ph.D. Available

[3] Naval Aerospace Medical Research Laboratory

Tactile Situation Awareness System. Presentation.

Available:

[4] Aviation Space and Environmental Medicine Vol. 57:725 July 1986

[5] Cholewiak, RW.

Exploring the conditions that generate a good vibrotactile line, presented at the

Psychonomic Society Meetings, Los Angeles, CA, 1995

[6] Craig, Roy R., Jr.,

Mechanics of Materials. United States of America: John Wiley & Sons, Inc.. 1996.

[7] Geldard, F.A.,

Sensory Saltation: Metastability in the Perceptual World, Lawrence Erlbaum Associates, Hillsdale, New Jersey, 1975.

[8] National Semiconductor (.

“LM 383 / LM 383A 7W Audio Power Amplifier”. Datasheets. 7 Jan 1996. 1-6. 30 March 1999. Online. Internet. Available

[9] Fairchild Semiconductor TM.

“CD 4053BC Triple 2-Channel Analog Multiplexer/Demultiplexer”. Datasheets. Jan 1999. 1-12. 30 March 1999. Online. Internet. Available

[10] Exar TM.

“XR-2206 Monolithic Function Generator”. Datasheets. June 1997. 1-16. 30 March 1999. Online. Internet. Available

[11] NAMRL Science and Technology Directorate.

Vestibular Test Development

Available:

[12] Tan, H. Z., & Pentland, A.

“Tactual displays for wearable computing”. Digest of the First International Symposium on Wearable Computers, 84-89. 1997.

[13] Digi-Key( Catalog

Catalog no. Q983. July-September 1998. Digi-Key Corporation, 1998.

[14] Microchip Technology Inc.

“PIC16C84”. PIC16/17 Microcontroller Data Book, Section 2. Pg. 824. 1995.

Appendix A

(Located in Power point documentation labeled Appendix A)

Appendix B

Letter from Oakland Elementary School

• Letter from Sunnyside Middle School

• Letter from Jefferson High School

• Letter from the Imagination Station

• Letter form Marian Delp

Appendix C

• Letter from (the supporting news station)

• Letter from the Decatur, IL Herald and Review

• Letter from the Purdue Exponent

Appendix D

• Letter from Dean Richard Schwartz

• Letter from Dr. Kent Fuchs

• Letter from Dr. Hong Tan

• Letter from Jerry Ross

Appendix E

• Insurance Waivers

• Proof of Age

Appendix F

• Safety Certifications

About Us

Ryan Casteel is a junior in the school of Electrical and Computer Engineering at Purdue University. He is a cooperative education student for the Department of Defense in Washington D.C. His current interests include control systems, communications, and international affairs. He is currently pursuing minors in mathematics and political science.

Jennifer Glassley is a junior in the school of Electrical and Computer Engineering at Purdue University. She is a cooperative education student for NASA / Lyndon B. Johnson Space Center. Her current projects with NASA include communication and electrical sensor work on the New Technology Spacesuits for Mars, the Moon, and the International Space Station.

Joachim Deguara is a sophomore at Purdue University, majoring in Electrical Engineering and minoring in Music Theory. He is in charge of the electronics in our study and has assembled and tested the building of the board and box. His main interests here at Purdue are doing research, community work, and working for the weekend.

Ryan Traylor is a sophomore in the school of Electrical and Computer Engineering at Purdue University. He is currently studying the psychophysics involved in tactual directional displays and is also interested in embedded microcontroller systems.

Adrian Lim is a sophomore in the school of Mechanical Engineering at Purdue University. He is currently minoring in Electrical and Computer Engineering and is involved in the research of Human Psychophysics. His academic interests in Purdue are robotics and design.

-----------------------

[1] The human tactual sense is generally regarded as made up of two subsystems: the tactile and kinesthetic senses. Tactile (or cutaneous) sense refers to the awareness of stimulation to the body surfaces and kinesthetic sense refers to the awareness of limb positions, movements and muscle tensions. The term haptics is often used to refer to manipulation as well as perception through the tactual sense.

[2] We use the term "display" to emphasize the fact that information flows from a machine to a human user.

-----------------------

[pic]

[pic]

[pic]

[pic]

[pic]

[pic]

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download