TEAM PENGUIN
TSGC Level I SOW Requirements
Spring 2009 An Inflight Neurovestibular Countermeasure for Gravitational Readaptation
Bernard Binder Luis Lazaro Auritra Mallick Steven Wu
Faculty Advisor: Dr. Maria Oden NASA Advisors: Dr. Tara Ruttley Dr. David Tomko Rice University Department of Bioengineering 6100 Main Street MS-142, Ste 116 Houston, TX 7705 1
Table of Contents
Re-Introduction of Project ……………………………………………………… 3 Semester I Recap …………………………………………………………………… 6 Key Accomplishments ……………………………………………………………. 12 Semester II Design Objective ……………………………………………….. 13 Semester II Design Plan ………………………………………………………… 13 Project Future …………………………………………………………………………. 17 Updated Timeline …………………………………………………………………….17 Updated Budget Plan ……………………………………………………………...17 Conclusion ……………………………………………………………………………….17 References ……………………………………………………………………………….19 Appendices ……………………………………………………………………………….20
List of Figures
Figure 1: Conceptual Foot Stimulation Device Figure 2: Conceptual Head Motion Device Figure 3: Motion Analysis Wireframe Figure 4: Foot Strike/Vertical Translation Data Figure 5: Neurovestibular Conditioning Suit Figure 6: Dynamic Force Application Boot Figure 7: Constructed Shoulder/Head Mount Table 1: Design Criteria and Objectives Table 2: Budget Plan
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Re-Introduction of Project Background Exposure to a microgravity environment triggers a host of physiological changes that affect the body’s handling of vestibular, ocular, and postural information. These changes can result in a condition called space motion sickness (SMS), caused by the adaptations the body and neurovestibular system make when interacting with a new environment.6 Upon return to an environment with normal gravity, a different but related set of physiological symptoms arise as a result of the body’s adaptation to weightlessness, including errors in postural control, gait, orientation, and coordination. These errors in turn result in difficulty walking in a straight line, problems rounding corners, falsely perceived motion, and difficulty standing straight.3,7 Several major theories have been proposed to explain neurovestibular disturbances in space and subsequent effects upon return to gravity. The most prevalent and well-supported theory is that of sensory conflict, which suggests that weightlessness destroys the relationship between signals from ocular, vestibular, touch, and other receptors.3,6 The resulting jumble of signals is not properly interpreted by the brain, and conflicting information about body orientation, acceleration, and body position, respectively, causes disorientation, nausea, and other negative effects. While the strict interpretation of sensory conflict is not rigorously provable or predictable
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under experimental conditions,3,6,7 it gives rise to a separate but related theory, the otolith tilt-translation reinterpretation (OTTR) hypothesis. OTTR is based on the principle that otolith graviceptors interpret both orientation with respect to gravity (tilt) and linear acceleration (translation).3 In a microgravity environment, the receptors stop responding to static pitch or roll because there is no defined up or down based on gravitational interaction. However, otoliths continue to respond to linear acceleration. This change in signaling contributes to motion sickness in space, until the body adapts to using graviceptor signals exclusively for linear acceleration and visual information for positional and rotational cues.3,6,7,10 Upon return to earth, however, this reliance on visual signals and loss of graviceptor pitch functionality results in postural instability and orientation and gait problems. The OTTR theory has been tested using three dimensional analyses of head motion before and after spaceflight, as well as measurement of dynamic posture, and comparisons of an astronaut’s ability to balance with and without visual cues postflight.3,10 As the focus of NASA’s space program shifts away from short-term orbital flights to longer, lunar or interplanetary missions, it is increasingly important to address microgravity-related neurovestibular problems that would be exacerbated by long travel times. In addition to the superficial discomfort experienced by astronauts after spaceflight, disorientation, postural, and reference frame problems could be extremely dangerous,
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especially under the unfamiliar terrain and conditions of another planet or moon. There are currently no effective existing countermeasures for spaceflight-induced neurovestibular problems. While nausea and motion sickness are currently treated with anticholinergic drugs, such pharmacological regimens do not improve postural and locomotive symptoms.13 With proposed flight times of over 200 days for a mission to Mars, there is a demonstrated need to develop new, effective countermeasures for post-flight neurovestibular symptoms.
Design Objectives The ultimate goal of this project is to design a device that reduces the effects of detrimental neurovestibular effects that arise as a consequence of exposure to microgravity. The device will be designed with the following considerations for the needs of the user: Minimize readaptation time to gravity following spaceflight Minimize time that user must devote to using the device Minimize device footprint on resources of the space vehicle Maximize simplicity both to set-up and use the device
Design criteria and objectives are listed in the following table:
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Design Objective Reduce adjustment time of astronauts to or from microgravity by 50% Durability in microgravity (no loss of performance) Device footprint less than 0.5 m2 Withstand forces of launch with no loss of functionality Wearable portions of device weigh less than 60 lb Require less than 15V/60W Cost less than $2,000 to build prototype Setup time less than 5 minutes Ability of user interface to support over 6 astronauts
Table 1 Method of Measurement or Design Estimate Compare adaptation time, unique to each astronaut, in days D with and without countermeasure Compare functionality F and effectiveness on a parabolic flight trainer (microgravity simulation) to F in 1 g Determine footprint by calculating area A occupied by widest portions of device Exposure to launch-strength forces on a centrifuge or other gravity simulator Estimate total wearable weight by summing weight of materials in each part Estimate electrical requirements by summing that of each component Determine cost by summing cost of components Determine time T required to unpack and pack device Determine number of unique astronaut profiles U that can be stored in device memory
Target Criterion D with countermeasure < ½ D without F in microgravity = F at 1 g A < 0.5 m2 F after launch = F before launch W < 60 lb V < 15V P < 60W C < $2,000 T < 5 min U>6
Semester I Recap Design Plan: Coordinated Head-Foot Stimulation for Locomotive Stability A combination of dynamic foot stimulation and head movement could prove to be a powerful approach toward attenuating loss of locomotive stability in astronauts returning from spaceflight. By designing an inflight 6
device that simulates the relationships between head tilt and lower limb motion that are ordinarily found in the presence of gravity, the user could be conditioned to retain the synchronicity between vertical head translation and pitch rotation that is usually disrupted by microgravity. An ideal device would allow a user to move their legs in a walking motion in microgravity while actively providing simulated forces to the feet and tilt to the head. Not only could this solution reduce readaptation time to gravity, but it could also partially mitigate the muscle atrophy and bone loss that occurs in space. The device will contain three distinct parts that will act together to simulate the forces felt on the astronaut’s foot during gait and the appropriate head motions that maintain a stable gaze. The first component, a customized boot (conceptual design shown in Figure 1), will contain accelerometers that track the user’s walking motion in microgravity. In order to
Figure 1 Conceptual dynamic foot stimulating boot
provide efferent neuromuscular stimulation during this motion, elastic therabands will connect the boot to a control pack to provide physical resistance against the legs. A series of bladders, pistons, or plates underneath a flexible sole will simultaneously apply pressure in a sequential manner to the
Figure 2 Conceptual head 7 motion device attached to control pack
bottom of the foot, corresponding to the heel strike and pushoff that would be found during normal gait on Earth. Since every astronaut has a distinct walking pattern and a unique response to microgravity conditions, the timing of the sequential pressure will be determined individually for each astronaut. The second component, a head mount, will guide the astronaut’s head to follow the pitch experienced during locomotion in sync with the application of pressure to the foot. Its fixed design will prevent motion of the head in any direction except that of forward tilt, and linear actuators at the joints will provide the force necessary to move the head. A conceptual head mount design is shown in Figure 2. The third component is a rigid, padded control pack that provides an attachment point for the head mount (see Figure 2). The pack will be fitted over the shoulders and fastened via chest strap to ensure that the actuators move the user’s head and not the rest of the body. It will also contain a power source and actuators. A microcontroller will collect and process data from the boot accelerometers and direct proper response from the head mount and pressure plates in the sole. The combination of dynamic foot stimulation and proper head motion should maintain familiarity with a pitching motion not normally found in microgravity and ease post-flight transition to gravity. It is important to note that this two-part device will not be incorporated into standard spacesuits or clothing. Rather, worn for an
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hour or two a day, dynamic head-foot stimulation could be used in a similar fashion as an exercise regimen to maintain conditioning. In order to accurately model the relationship between head and lower limb motion under gravitational conditions, motion analysis can be performed on a walking test subject. Reflective markers strategically positioned on a special suit are tracked by 8 or more cameras,
Figure 3 Wireframe representation of walking subject in a motion analysis laboratory. Important points are tracked by 8 or more cameras.
which triangulate the location of each marker and create a wire-frame motion analysis model. This analysis allows rigorous determination of the coordination between foot and head motion. Force plates embedded in the floor can be used in conjunction with the camera system to provide detailed information about pressures during the footstrike portion of the gait cycle. From this data, mathematical models and simulations may be constructed to accurately time the synchronization of the device in a manner consistent with terrestrial locomotion.
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Figure 4 Foot strike pressure data (right) can be combined with vertical translation data (left) from motion analysis to refine control of device timing.
Final Design Concept and Schematics: Neurovestibular Conditioning Suit The neurovestibular conditioning suit (schematic on following page) is a device that will be worn by astronauts for a predetermined period of time each day. Users will move their legs in a walking motion against the resistance of the elastic cords – during this motion, accelerometers at the feet will transmit information to the control pack, which will direct appropriately timed stimulation from the head brace and dynamic force application boot using models derived from preflight kinesiology lab data.
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Figure 5 Neurovestibular Conditioning Suit
Figure 6 Dynamic Force Application Boot
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Key Accomplishments to Date So far, the majority of the structural/mechanical elements of the conditioning suit have been adapted and constructed. A Rice University football helmet and a set of shoulder pads have been fitted with a linear actuator that successfully controls head tilt when extended and retracted as planned (see figure 7). Although the actuator has been hitherto controlled by a manually wired switch and power supply, Team Penguin is currently in the process of programming a Texas Instruments Piccolo TMS320C2000 microcontroller kit to modulate voltage supply and properly control the actuator. Potentiometer
Figure 7 Constructed head/shoulder mount with linear actuator controlling head tilt. The setup is controlled by a TI Piccolo microcontroller (not shown).
feedback corresponding to stroke length will be an input to the controller, ensuring safety when adjusting and testing device functionality. Construction of the boot system is also underway, and the soles from modified rollerblading boots have been removed, allowing for the installation of a flexible sole membrane. 3-axis VTT Technology accelerometers have also been received and are currently under investigation.
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Semester II Design Objectives The second semester goal for this project continues the first semester objectives (see Table 1). Specifically, Team Penguin will construct, program, and refine a device that functions in a manner that will putatively reduce the effects of detrimental neurovestibular effects that arise as a consequence of exposure to microgravity. The constructed device will meet the physical criteria described last semester and respond to simulated walking movements by applying appropriate head tilt and foot stimulation, determined by algorithms representing real kinesiology lab data.
Semester II Design Plan The combination of dynamic foot stimulation and head movement described in the Fall semester (see page 6) will be implemented using a variety of commercially available equipment. Specifics include the head mount, a snugly-fitting football helmet, which will be attached to shoulder pads by a 4-inch-stroke linear actuator with potentiometer feedback. Extension speed and length will be controlled by a Texas Instruments Piccolo board and will be regulated by actuator feedback. The actuator will also prevent extraneous head motion due to the nature of the mounting brackets. In addition to controlling actuator stroke, the microcontroller board will be programmed with mathematical models from kinesiology gait lab data
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and linked to the three-axis accelerometers to determine the precise amount of head motion needed. Foot stimulation will likely be determined by the same algorithm, and will be applied to specially modified roller blading boots with the soles removed. The soles will be replaced with flexible rubber or cloth sheeting, and pressure will be provided sequentially by either 1 inch stroke actuators or inflatable bladders. Since the neurovestibular conditioning device is intended for use in microgravity, testing options are limited. Available parabolic flight trainers that simulate microgravity do not allow for human testing of devices, so testing will be limited to proof-of-concept demonstrations on Earth. Testing under gravitational conditions will be considered successful if the device correctly interprets leg motions performed by the user and provides the sensory inputs to the user. Accelerometer Testing This device incorporates accelerometers located in the dynamic stimulating boots. These sensors are used to determine where the user is in the gait cycle as the feet are moved in a walking motion. It is important that the microcontroller accurately interprets the accelerometer data to provide the most accurate simulation of the timing of the gait cycle. To test this, a test subject will be strapped to a body-weight unloading treadmill at the National Center for Human Performance or the Johnson Space Center. The subject will wear boots with accelerometers in
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the same orientation as those found on the device’s stimulating boots. Acceleration data (adjusted to remove the acceleration component due to gravity) will be recorded in tandem with camera-based motion capture data for at least 10 full gait cycles. An algorithm will be developed to identify various events in the gait cycle from accelerometer data and will be compared with an existing algorithm that interprets motion capture data. The degree of parallelism, calculated by determining the standard time deviation between the two methods, will be used to judge the success of the device. Dynamic Force Application Boot Testing This device also incorporates dynamic stimulation of the bottom of the user’s foot to simulate ground forces experienced by the foot during the gait cycle and will be most effective when stimulation is accurately synchronized with the gait cycle. This test will incorporate a force-sensing sole as developed by Steven Irby at Shriner’s Children Hospital. Boots will be fitted with the force-sensing sole and accelerometers located in the same orientation as those in the stimulating boots. A test subject will wear these boots and walk for at least 10 full gait cycles as force and acceleration data is collected. Next, an artificial foot will be placed in the dynamic stimulating boots, and the acceleration data captured previously will be inputted into a control computer. As the boots apply a force to the plantar surface of the artificial
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foot, force data will be acquired as before. The timing between forces applied to the heel and the balls of the feet by the boots will be compared to those experienced by the subject during data capture. The standard deviation between the two will be calculated and used to judge success. Head Mount Testing The device also incorporates a head tilt device that tilts the head in synchronicity with the movement of the user’s feet. Under normal conditions, this head tilt compensates for vertical translation during walking. Maintaining the timing of head tilt during gait is the underlying principle behind this design and should be thoroughly tested. This test will incorporate a camera-based motion capture system. First, a test subject will be fitted with reflective markers and tilt data will be collected by the motion capture system as the subject walks. Acceleration data will be gathered as well, as before. Next, the head mount will be fitted with reflective markers. The head of a mannequin or dummy will be fitted with the mount. Acceleration data will be fed into the control computer and the head mount will be moved for at least 10 full gait cycles as tilt data is collected by the motion capture system. The two sets of tilt data will be compared to determine how well the device simulates complementary head tilt.
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Project Future Ideally, proof of concept of the neurovestibular conditioning suit will allow for additional testing in a microgravity trainer with IRB approval, and potentially in space on a shuttle or ISS extended-stay mission. If ultimately successful, the project could be beneficial for astronauts spending extended periods of time in microgravity, regardless of whether they are returning to Earth or travelling to an extraterrestrial environment. Project Timeline Please see attached project timeline. Budget Plan Team Penguin will be funded by TSGC, with small amounts of supplementary funding from Rice University. Table 2 TSGC Total Award Amount (all levels and options) Basic Expenses (printing fees, supplies, etc) Prototype (construction materials and testing) Travel and Lodging Miscellaneous Net Expenditure Conclusion There are currently no physical countermeasures for preventing detrimental neurovestibular symptoms that astronauts experience when 17 +$1250 -$100 -$700 -$300 -$150 $0
transitioning from microgravity to a gravitational environment. Designing a device that can reduce adaptation time or attenuate negative physiological effects is of significant interest, especially given that there is increasing emphasis on long-term spaceflight missions. In order to achieve this goal, Team Penguin is designing, constructing, and testing a combined, coordinated head-foot stimulation device that will be used inflight with a simulated walking motion to help condition astronauts and expedite readaptation to normal locomotion under gravity.
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References
[1] Young L.R., Oman C.M., Watt D.G.D., Money K.E., Lichtenberg B.K., Kenyon R.V., Arrott A.P. "M. I. T./Canadian vestibular experiments on the Spacelab-1 mission: 1. Sensory adaptation to weightlessness and readaptation to one-g: an overview.” Exp Brain Res 64:291-298 (1986). [2] Clement G., Reschke M., Wood S. “Neurovestibular and Sensorimotor Studies in Space and Earth Benefits.” Current Pharmaceutical Biotechnology 6:267-283 (2005). [3] Reschke M.F, Bloomberg J.J, Harm D.L., Paloski W.H. “Space flight and neurovesibular adaptation.” J Clin Parmacol 34:609-617 (1994). [4] Angelaki D.E. and Dickman J.D. “Gravity or translation: Central processing of vestibular signals to detect motion or tilt.” J Vestibular Res 9:46 (2004). [5] Oman Charles. NSBRI Neurovestibular Adaptation Team Strategic Plan. Massachusetts Institute of Technology, Cambridge, MA. [6] Nicogossian A.E., Mohler, S.R, Gazenko O.G., Grigoriev A.I,. “Space Biology and Medicine, Volume III Humans in Spaceflight Book 1.” American Institute of Aeronautics and Astronautics, Inc. 136-146 (1996). [7] Churchill S.E. “Fundamentals of Space Life Sciences Volume I.” Krieger Publishing Company Inc. 66-78 (1997). [8] Ruttley, Tara “The Role of Body Load-Regulating Mechanisms in Gaze Stabilization During Locomotion, 11-12” Diss. University of Texas Medical Branch, (2007) [9] Kyparos, A., Feeback, D.L., Layne, C.S., Martinez, D.A., and Clarke, M.S.F. “Mechanical stimulation of the plantar foot surface attenuates soleus muscle atrophy induced by hindlimb unloading in rats.” J Appl Physiol 99:739-746 (2005). [10] Bloomberg J, Mulavara A. “Changes in Walking Strategies after Spaceflight. IEE Engineering in Medicine and Biology Magazine 2:58-62 (2004). [11] D’Andrea SE, et al. A dual track treadmill in virtual reality environment as a countermeasure for neurovestibular adaptations in microgravity. NASA/ CP 1:113130 (2004). [12] Britton TC, et al. “Postural electromyographic responses in the arm and leg following galvanic stimulation in man.” Exp Brain Res 94:143-151 (1993). [13] Holmick, JL. “Space motion sickness.” Acta Astronautica 6:1259-1272 (1979).
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Appendix A: Expense/Budget Report See attached Appendix B: Team Pictures
Team Penguin from left to right: Steven Wu, Auritra Mallick, Luis Lazaro, Bernard Binder
Bernard Binder
Steven Wu
Auritra Mallick
Luis Lazaro
Appendix C: Option Areas See attached
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