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Test Bed 6- Human Assist Devices (Fluid-powered ankle-foot-orthoses)

Test Bed 6- Human Assist Devices (Fluid-powered ankle-foot-orthoses). Faculty. Students. Liz Hsiao-Wecksler (UIUC) Will Durfee (UM) Geza Kogler (GT) Zongliang Jiang (NCAT) Doug Cook (MSOE) Vito Gervasi (MSOE) Tom Chase (UM) David Kittelson (UM) Eric Barth (Vanderbilt).

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Test Bed 6- Human Assist Devices (Fluid-powered ankle-foot-orthoses)

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  1. Test Bed 6-Human Assist Devices(Fluid-powered ankle-foot-orthoses) Faculty Students Liz Hsiao-Wecksler (UIUC) Will Durfee (UM) Geza Kogler (GT) Zongliang Jiang (NCAT) Doug Cook (MSOE) Vito Gervasi (MSOE) Tom Chase (UM) David Kittelson (UM) Eric Barth (Vanderbilt) Yifan David Li(UIUC) Morgan Boes (UIUC) Mazhar Islam (UIUC) Jicheng Xia (UM) Nebiyu Fikru (UM) Lei Tian (UM) Mark Hofacker (Vanderbilt) Dan Cramer (Vanderbilt) Davorin Stajsic (NCAT)

  2. Overview • Motivation • Test Bed 6 Timeline • Progress on Pneumatic AFO • Progress on Hydraulic AFO • TB6 Affiliated Projects • Future Work

  3. Stroke (4.7M*) • Polio (1M*) • Multiple sclerosis (400K*) • Spinal cord injuries (200K*) • Cerebral palsy (100K*) • Trauma Major question being answered • Do energy-to-weight and power-to-weight advantages of fluid power (FP) continue to hold for tiny, mobile FP systems (10-100 W)? • Drive development of enabling FP technologies • Create new portable, wearable, FP assist devices • TB6 Product Platform: Ankle-Foot Orthosis • Numerous pathologies / injuries create below the knee muscle weakness and impair gait • Currently no portable powered ankle-foot orthosis avalible for treatment * Number of people in US that would benefit from an active lower limb orthosis [Dollar and Herr, IEEE Trans Robotics, 24(1): 144-158, 2008]

  4. Potentialapplications • Rehabilitation of lower leg muscles (possible from the patient’s personal residence instead of restricted to clinic) • Assistance in walking (including flexibility to walk outside) • General use for public commercial applications where large amounts of walking are required

  5. TB6Development Timeline • Multiple Design Versions • Started with motion control and progressed to powered actuation ca 2008 Custom integrated (Untethered) CCEFP affil. proj. 50-150 psi 6-20 Nm Light-weight Safer Powered pneumatic AFO for both motion control and assistance (Tethered) Pneumatic AFO Off-the-shelf components ca 2012 IMU ca 2007 ca 2010 • IMU based mode recognition • Functional energy efficiency analysis Passive pneumatic power- harvesting AFO for motion control (Untethered) Portable Powered pneumatic AFO for both motion control and assistance (Untethered) Hydraulic AFO

  6. Setup for Pneumatic AFO Structure: Shell, lines, integration Power: Engine or CO2 Actuation: Valves, Regulators, Actuator Electronics: Sensors and driving electronics The world’slightest, most compact, untethered, pneumatically poweredAFO

  7. Inertial Sensor Based Gait Mode Recognition and Actuation Control Goal: recognize different gait modes (stairs and ramps) and control the actuation accordingly Actuation for LEVEL GROUND Actuation for Stair Descent IMU • Mode recognized by IMU • Plantarflexor (0-20GC and 60-100GC) Different Functional Need for Stair Descent Level: Dorsiflexion, create clearance for limb advancement StairDescent: Plantarflexion, prepare for next landing

  8. Inertial Sensor Based Gait Mode Recognition and Actuation Control Stair and ramp modes can be recognized by tracking the vertical position differences and foot angle for each step Experimental Protocol Three gait mode conditions: Outdoor stairs, one step traverse Outdoor stairs, two step traverse Indoor stairs, two step traverse Level ground was assessed during approach for ascent and descent the stairs Three PPAFO actuation algorithms: Passive: no actuation provided Mode Controller: level controller except stair descent (plantarflexor torque during swing) Level Controller: actuation provided using original level ground walking mode controller for all gait modes Only (c) tested for gait mode conditions 2-4. Number of Subjects: 5 (male) Weight: average 82.0kg (70-97kg) Age: average 23.4 (20-27) Height: average 178.6cm (166-191cm)

  9. Functional Efficiency Analysis Goal: Compare fuel consumption and work output between different control algorithms Wireless Data Logging Force, Angle, Pressure Micro Controller CO2 Bottle • Procedure Notes: • Four healthy subjects (22-30 y.o.) • 3 minute trials of walking, ~150Hz sampling • CO2 bottles were weighed before and after each trial for fuel consumption • Each bottle was warmed to room temperature in a water bath before use • 4 bottles were rotated for use to allow warming Computer Data Logging Receiver

  10. Results on fuel consumption and net work output for different controllers • Results • SE took on average 6% more fuel than DE. • SER saves 17.5% of fuel compared to the fuel consumption of SE. • The DE scheme did more work than SE or SER. • SE and SER did approximately the same amount of work per gait cycle

  11. Hydraulic Ankle Foot Orthosis: First Platform Torque: 90 N-m (600 lbs force for a 3cm moment arm) Small packaging space Weight: < 1 kg Portability: untethered Longevity: 10,000 steps Peak power: 250 W Artist rendering

  12. Many System Level Questions Need to Be Answered Before Specifying Each Component Electric Motor Battery Pump Conduits Actuators Piston? or Vane? Long? or Short? Linear? or Rotary? Gearhead? or Not?

  13. The Efficiency and Weight of Each Component Can Be Modeled Analytically Gear-head Efficiency Electric DC Motor Weight Hydraulic Cylinder Weight Axial-Piston Pump Efficiency

  14. The Established Efficiency and Weight Models Can Identify the AFO Configuration Power Pack

  15. Design Variables Can Be Expressed by Known Parameters* Pump displacement (cc/rev): Num. of pistons Pitch radius Pump piston area (m^2): Swash-plate angle Pump piston bore (m): Pump efficiency: * Key pump design variable: pump displacement, pump piston bore and pump efficiency. To simplify the design problem, other pump parameters were adopted from the three-piston Oildyne pump.

  16. Design Variables Can Be Plotted on P-n Plot

  17. The Hydraulic AFO Components Can Be Specified Based on the Design Map

  18. Conclusions System level analyses are necessary to identify the design guidelines for the hydraulic AFO. The analytical efficiency and weight models for the system level analyses are achievable. For the hydraulic AFO, the actuators would better be separated from the power source, similar to an excavator. The analytical efficiency and weight models are also needed to specify each component in the hydraulic AFO system.

  19. Affiliated Projects: 2F MEMS Valve (Nebiyu Fikru, UMN) • Goal : Create an efficient MEMS based proportional valve for controlling air flow in pneumatic systems • Targets • High flow rate (40 slpm at 6 → 5 bar) • Compact (< 4 cm3) • Low power usage (< 1 mW) • Progress • Port plate with array of orifices successfully fabricated and tested for flow and pressure • Displacement sensor integrated to meso-scaleprototype valve • Fabrication of MEMS unimorph actuator nearing completion • Next Steps • Complete and test MEMS unimorph actuator • Demonstrate proportional control on meso-scale valve • Fabricate MEMS bimorph PZT actuator

  20. Affiliated Projects Clinician Centered AFO Interface (Davorin Stajsic, NCAT) Spring 2013 plans • NCAT will continue to work on Quanser and XNA integration, and further game and GUI development. Currently there are some XNA and Quanser API incompatibilies that need to be resolved. • Plan on doing experimental research using CybexNorm system (shown) to emulate a game therapy session in order to test the effects of different factors that may have an impact on game performance (social interaction among patients, leg dexterity, different seating positions, etc.) • This experiment will help with further development of the game with features that ensure patient improvement, and a game therapy that is effective on a more diverse patient population.

  21. Affiliated Projects – 2D MSOE • Passive HCCI thermal-management • Successful testing w/ surrogate source • http://utwired.engr.utexas.edu/lff/symposium/proceedingsArchive/pubs/Manuscripts/2012/2012-09-Cook.pdf • Currently not funded by CCEFP • Developing high-efficiency pneumatic actuation system • >60% ηthermodynamic using <15g fuel/hr • CCEFP rejected 2011 proposal • Proposal submitted to NSF National Robotics Institute • Co-robotics applications – legged robots, assisting humans

  22. Affiliated Projects Elastomeric Accumulator (Dan Cramer, Vanderbilt) • Goal : Create a gravimetrically and volumetrically efficient strain accumulator for pneumatic systems • Targets • Pressures 7-10 bar • Max volume of 34 ml • Progress • Accumulator operating below 7 bar fitted • Next Steps • Fabricate accumulator for use with pressures up to 150 psi • Evaluate gravimetric and volumetric efficiencies

  23. Affiliated Projects: 2B.4 Controlled Stirling Thermocompressor (Eric Barth, Vanderbilt) • Goal : Create a compact, near silent, pneumatic power source with low amounts of vibration • Targets • 20 Watts • 80 psig • Mounted on ankle-foot orthosis • Progress • Completed dynamic model of thermocompressor • Constructed single stage prototype • Novel take on Stirling cycle device • Piston controlled directly by brushless DC motor and reciprocating lead screw • Developed method of achieving high rates of heat transfer in compact device • In process of patenting • High Temperature/High Efficiency • Enabled by use of fused quartz and machinable ceramic • Next Steps • Instrument and test prototype • Refine model • Build multistage compressor capable of high pressure Stainless Steel Heater Head Fused Quartz Cylinder Reciprocating Lead Screw Macor Machinable Ceramic Pressure Transducer DC Motor

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