Control system for prosthetic knee

• US 7,799,091 B2
• Filed: 10/08/2007
• Issued: 09/21/2010
• Est. Priority Date: 03/29/2000
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Wilkenfeld, Ari, Bleck, Olaf, Herr, Hugh M.
• Primary Examiner(s): Willse; David H
• Assistant Examiner(s): Blanco; Javier G
• Application Number:
  US11/868,941
• Publication Number:
  US 20080114272A1
• Time in Patent Office: 1,079 Days
• Field of Search: 623 24- 27, 623 39- 45
• US Class Current: 623/44
• CPC Class Codes: A61B 5/1038 Measuring plantar pressure during gait
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61F 2/64 Knee joints
• CPC Class Codes: A61F 2/70 electrical
• CPC Class Codes: A61F 2002/5003 having damping means, e.g. shock absorbers for implantable joints A61F2002/30563
• CPC Class Codes: A61F 2002/5004 operated by electro- or magnetorheological fluids
• CPC Class Codes: A61F 2002/6818 for braking
• CPC Class Codes: A61F 2002/704 computer-controlled, e.g. robotic control
• CPC Class Codes: A61F 2002/7625 for measuring angular position
• CPC Class Codes: A61F 2002/7635 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61F 2002/7645 for measuring torque, e.g. hinge or turning moment, moment of force
• CPC Class Codes: F16F 9/535 Magnetorheological [MR] fluid dampers springs comprising magnetorheological [MR] elastomers F16F1/361

Abstract

The invention relates to an automated speed-adaptive and patient-adaptive control scheme and system for a knee prosthesis. The control scheme and system utilizes sensory information measured local to the prosthesis to automatically adjust stance and swing phase knee resistances to a particular wearer under a wide variety of locomotory activities. Advantageously, no patient-specific information needs to be pre-programmed into the prosthetic knee by a prosthetist or the patient. The system is able to adapt to various types of disturbances once the patient leaves the prosthetist'"'"'s facility because it is patient-adaptive and speed-adaptive.

Claims

1. A method of adaptively controlling a prosthetic joint worn by an amputee, comprising:

measuring speed indicative data with sensors local to said prosthetic joint as said amputee moves at various speeds;

storing said data in a memory of said prosthetic joint in bins corresponding to the speed of said amputee;

iteratively modulating the damping to achieve a predetermined and/or computed target until the damping converges within each bin; and

controlling said prosthetic joint by utilizing the converged damping values to control the damping of said prosthetic joint by varying the viscosity of a magnetorheological fluid contained in said prosthetic joint that provides variable resistance to flexion and/or extension, wherein said damping is created primarily by shear forces,

wherein said prosthetic joint comprises a prosthetic knee, and wherein said method further comprises controlling said prosthetic knee worn by said amputee using a controller which transitions between a plurality of states of biological gait including a first state generally corresponding to stance flexion, a second state generally corresponding to stance extension, a third state generally corresponding to knee break, a fourth state generally corresponding to swing flexion, and a fifth state generally corresponding to swing extension, said method further comprising;

measuring sensory information and providing said sensory information to said controller for computation of axial force, extension moment, knee angle and velocity;

transitioning from said first state to said second state under condition C12 and said condition C12 being satisfied when said prosthetic knee achieves a predetermined extension velocity;

transitioning from said second state to said third state under condition C23 and said condition C23 being satisfied when said extension moment is below a first threshold;

transitioning from said third state to said fourth state under condition C34 and said condition C34 being satisfied when said axial force falls below a second threshold;

transitioning from said fourth state to said fifth state under condition C45 and said condition C45 being satisfied when said prosthetic knee begins to extend;

transitioning from said fifth state to said first state under condition C51 and said condition C51 being satisfied when said axial force climbs above a third threshold; and

controlling operation of said prosthetic knee in said states of biological gait by processing said sensory information to provide a controlled and variable resistance to flexion and/or extension.

2. The method of claim 1, wherein measuring speed indicative data comprises measuring ground contact time.

3. The method of claim 2, wherein said ground contact time changes substantially monotonically with the speed of said amputee.

4. The method of claim 2, wherein said ground contact time is stored in about twenty said bins.

5. The method of claim 4, wherein each of said bins has a size that represents about 100 milliseconds.

6. The method of claim 1, wherein iteratively modulating the damping comprises iteratively modulating the damping to achieve a target swing flexion angle over a range of speeds of the amputee.

7. The method of claim 6, wherein said target swing flexion angle is about 80°

.

8. The method of claim 1, wherein controlling said prosthetic joint comprises controlling flexion and/or extension of said prosthetic joint over a range of speeds of the amputee.

9. The method of claim 1, wherein said method further comprises applying a magnetic field to vary the viscosity of said magnetorheological fluid.

10. The method of claim 9, wherein said method further comprises shearing said magnetorheological fluid.

11. The method of claim 10, wherein shearing said magnetorheological fluid comprises shearing said magnetorheological fluid in a plurality of gaps.

12. The method of claim 10, wherein shearing said magnetorheological fluid comprises shearing said magnetorheological fluid in a plurality of gaps formed between a plurality of blades.

13. The method of claim 12, wherein said blades are rotatable.

14. The method of claim 13, wherein said blades are in mechanical communication with a lower leg portion.

15. The method of claim 13, wherein said blades are in mechanical communication with an upper leg portion.

16. The method of claim 1, wherein said condition C23 is further satisfied when said prosthetic knee is at or close to full extension.

17. The method of claim 16, wherein said condition C23 is further satisfied when said prosthetic knee has been substantially still for a predetermined time.

18. The method of claim 1, wherein said method further comprises transitioning from said first state to said third state under condition C13 and said condition C13 is satisfied when said extension moment is below a fourth threshold.

19. The method of claim 18, wherein said condition C13 is further satisfied when said prosthetic knee is at or close to full extension.

20. The method of claim 19, wherein said condition C13 is further satisfied when said prosthetic knee has been substantially still for a predetermined time.

21. The method of claim 1, wherein said method further comprises transitioning from said first state to said fourth state under condition C14 and said condition C14 is satisfied when said axial force falls below a fourth threshold.

22. The method of claim 1, wherein said method further comprises transitioning from said second state to said first state under condition C21 and said condition C21 is satisfied when said prosthetic knee achieves a predetermined flexion velocity.

23. The method of claim 1, wherein said method further comprises transitioning from said second state to said fourth state under condition C24 and said condition C24 is satisfied when said axial force falls below a fourth threshold.

24. The method of claim 1, wherein said method further comprises transitioning from said third state to said first state under condition C31 and said condition C31 is satisfied when said prosthetic knee has been in said third state for a predetermined time.

25. The method of claim 1, wherein said method further comprises transitioning from said third state to said first state under condition C31 and said condition C31 is satisfied when extension moment is above a fourth threshold.

26. The method of claim 25, wherein said condition C31 is further satisfied when said prosthetic knee is at or close to full extension.

27. The method of claim 1, wherein said method further comprises transitioning from said fourth state to said first state under condition C41 and said condition C41 is satisfied when said axial force climbs above a fourth threshold.

28. The method of claim 1, wherein said prosthetic knee comprises a magnetorheological damper.