1. R. Riener, H. Vallery, A. Duschau-Wicke ETH Zurich, Balgrist University Hospital, Hocoma Z. Rymer & Y. Dhaher Rehabilitation Institute of Chicago MARS-RERC Advisory Board Meeting 18/19 August 2009 D1: Cooperative Control for Robot-Aided Gait Therapy

2. Zurich Network R. Riener & V. Dietz & G. Colombo

3. Robotic Treadmill Training: Lokomat Conventional Version Position control: fixed trajectory, no interactivity Fixed speed Limitted pelvis movement G. Colombo, V. Dietz

4. Cited Limitations Altered EMG patterns [Hidler & Wall 2005] Abnormal force patterns [Neckel et al. 2007] Irregular accelerations and decelerations [Regnaux et al. 2008] Better treatment outcome of manual therapy compared to Lokomat [Hornby et al. 2008; Hidler et al. 2009] Limitations of Robotic Gait Training

5. Parameters Virtual Assistent Position Force Patient-Cooperative Control

6. Design and evaluate cooperative control strategies that provide more freedom and participation by the patients, while still guaranteeing functional gait training Assess the effects of cooperative control strategies on stroke patients using quantitative and qualitative measures of gait performance D1 Objectives

7. Patient-Cooperative Control Goal: Active patient participation Prerequisites -Transparency: “Hide” the robot when not needed -Constraints: Keep patient within safe domain

8. Goal: Active patient participation Prerequisites -Transparency: “Hide” the robot when not needed -Constraints: Keep patient within safe domain Patient-Cooperative Control

9. Transparency: Task Formulation Minimize Interaction Forces/Torques!

10. Transparency: Task Formulation Interaction torques Inertia Gravity, Coriolis, centrifugal, damping Actuator torques (robot)

11. Example: Mass with 1 DOF 1. Given Mass (Robot) Connected to Operator (Human)

12. 2. Given Movement of the Operator (Human) 3. Calculate Forces to Let Mass (Robot) Follow Example: Mass with 1 DOF

13. 4. Find Optimal Conservative (Elastic) Force Field as Function of Position 5. Apply Force Field by Actuators (Robot) Example: Mass with 1 DOF

14. Multi-Joint Robot: Optimal Force Field

15. Generalized Elasticities: Results Mean RMS Interaction Torques at the Joints

16. Generalized Elasticities: Results Impact on Gait Parameters

17. Generalized Elasticities: Results Gravity cancellation Generalized elasticities

18. Goal: Active patient participation Prerequisites: -Transparency: “Hide” the robot when not needed -Constraints: Keep patient within safe domain Patient-Cooperative Control

19. Challenge Support, but do not restrict patient Path Control Path: virtual tunnel Robot applies assistive and corrective torques Path Control

20.  1 (hip angle)  2 (knee angle) φ ref φ act F allowed region reference path Idea Combine free timing with spatial guidance

21. Generalized Elastic Path Control Solution Re-formulate path control as a potential field with constraining forces outside the tunnel and generalized elasticities inside the tunnel.  1 (hip angle)  2 (knee angle) Constraining forces Transparency-enhancing forces to hide robot

22. Path Control: Healthy Subject Tested on 12 Healthy Subjects

23. Path Control: iSCI Subject

24. Muscle Activity Heart Rate Pos.contr. Path contr. 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 Init. loading Mid stance Term. stance Pre swing Init. swing Mid Swing Term. swing Normalized muscle activity (BF) Position control Path control Relative increase of heart rate 14 incomplete SCI subjects Path Control Increases Participation

25. Path Control Increases Variability Position Control -20-10010203040 0 10 20 30 40 50 60 70 80 Hip angle [°] Knee angle [°] Path Control -20-10010203040 0 10 20 30 40 50 60 70 80 Hip angle [°] Knee angle [°]

26. Treadmill Speed Adaptation Basic Principle F = m a = m v. Admittance Controller Treadmill F a a m F Processing F m => v = ∫ F/m dt + v 0

27. Is that enough? Video courtesy of Klinik Valens

28. Lokomat Extension from 4 to 7 DoF 4 active DoF 11 11 7 active DoF 11 22 1

29. Components of 7DoF Control 5 DoF Generalized Elastic Path Control: Hip and knee flexion + pelvis translation 6 DoF collision avoidance: Hip and knee flexion + hip abduction 2 x 1 DoF abduction limitation: Abduction only

30. Evaluation on Stroke Patients at the RIC

31. Shift to Clinical Evaluation 2009 2010 Balgrist, 4 DoF Healthy; SCI pilot RIC, 4 DoF Stroke pilot Balgrist, 7 DoF Tests on healthies RIC, 7 DoF Stroke pilot RIC, Stroke study today Balgrist, 7 DoF Multicenter RCT with iSCI?