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					The MIT Leg Lab: From Robots
          to Rehab
State Of The Art
   Otto Bock C-Leg
      Flex-Foot
         State of the Art:
Prosthetist defines knee damping
   Otto Bock C-Leg
     The MIT Knee: A Step
      Towards Autonomy

 Virtual               Virtual
Prosthetist         Biomechanist
How The MIT Knee Works:
      Mechanism
     How The MIT Knee Works:
             Sensors

  Knee Position
                    Measured Local to Knee
  Axial Force       Axis (no ankle or foot
  Bending Moment           sensors)



Amputee can use vertical shock system
How the MIT Knee Works:
     Stance Control




Goal: Early Stance Flexion &
         Extension
Stance Control: Three States
   Stance Flexion & Stance Extension
    –   A variable hydraulic damper
    –   Damping scales with axial load
   Late Stance
    –   Minimize damping

        Toe-Loading to trigger late-stance zero damping is
               automatically adjusted by system
Stance Flexion
 How the MIT Knee Works:
      Swing Control




Goal: Control Peak Flexion Angle &
         Terminal Impact
 Swing Control: Flexion
                          90                               100




                                                                 Swing-flexion damping
flexion angle (degrees)




                                                                 value (arbitrary units)
                          80                               90
   Maximum swing-


                          70                               80
                                                           70
                          60
                                                           60
                          50
                                                           50
                          40
                                                           40
                          30
                                                           30
                          20                               20
                          10                               10
                          0                                0
                               1        6     11     16
                                   Number of steps taken
                              Swing Control: Flexion

                  90                                                       90
Angle (degrees)




                                                         Angle (degrees)
                  60                                                       60

                  30                                                       30

                   0                                                        0
                       0.0   0.5     1.0 1.5 2.0   2.5                          0.0   0.5    1.0   1.5      2.0   2.5
                                   Speed (m/sec)                                            Speed (m/sec)
             Swing Phase: Extension
Extension damping adaptation
                                                          Foot Contact Time
 Stage one:                                    2.5
    –   Map tc versus impact force               2




                                     Time (s)
    –   Apply appropriate damping               1.5

   Stage two:                                   1

    –   Control final angle while               0.5
        minimizing impact force                  0
                                                      0    0.5   1          1.5   2   2.5
                                                                 Velocity (m/s)
The MIT Knee In Action
                     Human Knees
                    Brake and Thrust

               1
Power (W/Kg)




               0


               -1


                     Percent Gait Cycle
Human Ankles are Smart Springs

  Leg stiffness control   Variable stiffness
     in walking and          foot-ankle
    running humans            systems
Human Ankles are Powered
  Future of O&P Leg Systems:
 Intelligent Application of Power
• Greater Distance & Less Fatigue
• Natural Gait - Dynamic Cosmesis
• Enhanced Stability
• Increased Mobility
Human Rehab: A Road Map to
        the Future

Better Power Systems and Actuators
Series-Elastic Actuators
   (Muscle-Tendon)
Controlling Force, not Position



                  Weight: 2.5 lbs.
                  Stroke: 3 in.
                  Max. Force: 300 lbs.
                  Force Bandwidth: 30 Hz
Biomechatronics Group
    Hybrid Robots



           • Nearly autonomous
           • Controllable
           • Swam 0.5 body length per
                 second
Human Rehab: A Road Map to
        the Future

 Improved Walking Models
Low Stiffness Control: Virtual Model
         Control Language

• Passive walkers work using
    physical components
•   Q: Can active walker
    algorithms be expressed
    using physical metaphors?
• A: Yes, and they perform
    surprisingly well
Virtual Assistive Devices for Legged
                Robots
Troody
     Science              Technology
What are the biological
                            Virtual Model
  models for human
                                Control
       walking?


                          Active O&P Leg Systems
Human Rehab: A Road Map to
        the Future

Distributed Sensing and Intelligence
              User Intent


 Virtual                       Virtual
Prosthetist                 Biomechanist
               Collaborators
Leg Laboratory
  Gill Pratt

Biomechatronics Group
  Robert Dennis (UM)
  Nadia Rosenthal (MGH)
  Richard Marsh (NE)
Spaulding Gait Laboratory
  Casey Kerrigan
  Pat Riley
         Sponsors
•Össur
•DARPA
•Schaeffer Foundation
               Summary

Advances in the science of legged locomotion,
bioactuation, and sensing are necessary to step
towards the next generation of O&P leg
systems

				
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posted:8/29/2011
language:English
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