The MIT Leg Lab: From Robots to Rehab

State Of The Art Flex-Foot Otto Bock C-Leg

State of the Art: Prosthetist defines knee damping Otto Bock C-Leg

The MIT Knee: A Step Towards Autonomy Virtual Prosthetist Virtual Biomechanist

How The MIT Knee Works: Mechanism

How The MIT Knee Works: Sensors Knee Position Axial Force Bending Moment Measured Local to Knee Axis (no ankle or foot sensors) Amputee can use vertical shock system

Goal: Early Stance Flexion & Extension How the MIT Knee Works: Stance Control

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

Goal: Control Peak Flexion Angle & Terminal Impact How the MIT Knee Works: Swing Control

Swing Control: Flexion

Swing Phase: Extension Extension damping adaptation Stage one: – Map t c versus impact force – Apply appropriate damping Stage two: – Control final angle while minimizing impact force Foot Contact Time

The MIT Knee In Action

Human Knees Brake and Thrust 0 1 Power (W/Kg) Percent Gait Cycle

Human Ankles are Smart Springs Variable stiffness foot-ankle systems Leg stiffness control in walking and running humans

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

Nearly autonomous Controllable Swam 0.5 body length per second Biomechatronics Group Hybrid Robots

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 models for human walking? Virtual Model Control Active O&P Leg Systems

Human Rehab: A Road Map to the Future Distributed Sensing and Intelligence

Virtual Prosthetist Virtual Biomechanist User Intent

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