POWERED LEG PROSTHESIS AND CONTROL METHODOLOGIES FOR OBTAINING NEAR NORMAL GAIT

• US 20090265018A1
• Filed: 04/21/2009
• Published: 10/22/2009
• Est. Priority Date: 04/21/2008
• Status: Active Grant

• Current Assignee: Vanderbilt University
• Original Assignee: Vanderbilt University
• Inventors: Mitchell, Jason, Goldfarb, Michael, Sup, Frank Charles IV, Varol, Huseyin Atakan, Withrow, Thomas J.
• Granted Patent: US 8,652,218 B2
• Time in Patent Office: Days
• US Class Current: 623/40
• CPC Class Codes: A61F 2/60 Artificial legs or feet or parts thereof
• CPC Class Codes: A61F 2/64 Knee joints
• CPC Class Codes: A61F 2/66 Feet; Ankle joints
• CPC Class Codes: A61F 2/6607 Ankle joints
• CPC Class Codes: A61F 2/72 Bioelectric control, e.g. myoelectric
• CPC Class Codes: A61F 2002/30359 Pyramidally- or frustopyramidally-shaped protrusion and recess
• CPC Class Codes: A61F 2002/5073 Helical springs, e.g. having at least one helical spring
• CPC Class Codes: A61F 2002/6642 Heels
• CPC Class Codes: A61F 2002/665 Soles
• CPC Class Codes: A61F 2002/6657 having a plate-like or strip-like spring element, e.g. an energy-storing cantilever spring keel
• CPC Class Codes: A61F 2002/6836 Gears specially adapted therefor, e.g. reduction gears
• CPC Class Codes: A61F 2002/701 operated by electrically controlled means, e.g. solenoids or torque motors
• CPC Class Codes: A61F 2002/704 computer-controlled, e.g. robotic control
• CPC Class Codes: A61F 2002/705 Electromagnetic data transfer for implantable prostheses A61F2250/0002
• 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 2002/764 for measuring acceleration
• CPC Class Codes: A61F 2002/7645 for measuring torque, e.g. hinge or turning moment, moment of force
• CPC Class Codes: A61F 2002/768 for measuring battery status
• CPC Class Codes: A61F 2220/0033 made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit

Abstract

A powered leg prosthesis includes powered knee joint comprising a knee joint and a knee motor unit for delivering power to the knee joint. The prosthesis also includes a prosthetic lower leg having a socket interface coupled to the knee joint and a powered ankle joint coupled to the lower leg opposite the knee joint comprising an ankle joint and an ankle motor unit to deliver power to the ankle joint. The prosthesis further includes a prosthetic foot coupled to the ankle joint, at least one sensor for measuring a real-time input, and at least one controller for controlling movement of the prosthesis based on the real-time input.

Claims

1. A powered leg prosthesis, comprising:

a powered knee joint comprising a knee joint and a knee motor unit for delivering power to said knee joint;

a powered ankle joint coupled to said knee joint comprising an ankle joint and an ankle motor unit to deliver power to said ankle joint;

a prosthetic foot coupled to said ankle joint;

at least one sensor for measuring a real-time input; and

at least one controller for controlling movement of said prosthesis based on said real-time input.

2. The leg prosthesis of claim 1, further comprising at least one position sensor located at said knee joint and at least one position sensor at said ankle joint.

3. The leg prosthesis of claim 1, further comprising an assembly coupled to said knee joint that includes a motor connected to a ballscrew.

4. The leg prosthesis of claim 1, further comprising a knee and ankle motor unit that delivers power to the joint using at least one among a cable drive or a friction drive.

5. The leg prosthesis of claim 1, further comprising an assembly coupled to said ankle joint that includes a motor connected to a ballscrew in parallel with a spring, said spring increasing peak torque and power capability of said ankle joint.

6. The leg prosthesis of claim 1, wherein said foot further comprises a ball and a heel.

7. The leg prosthesis of claim 6, wherein at least one sensor measures a sagittal plane moment and ground interaction forces at said ball and at said heel.

8. The leg prosthesis of claim 1, wherein said controller determines a torque for application to said ankle and knee joints by performing a torque decomposition, wherein a torque for said joints is decomposed by said controller into an active portion and a passive portion.

9. The leg prosthesis of claim 8, wherein said active portion results from an interaction between a user and said prosthesis measured by said sensor, and wherein said passive portion has a nonlinear spring-dashpot behavior.

10. The leg prosthesis of claim 8, wherein active passive torque decomposition comprises solving a constrained optimization problem.

11. The leg prosthesis of claim 1, wherein said controller further comprises at least one accelerometer for measuring shank accelerations in the frontal, sagittal, and axial planes and one accelerometer for measuring foot accelerations in the frontal, sagittal, and axial planes.

12. The leg prosthesis of claim 1, wherein said controller comprises an intent recognizer for recognizing an intent of a user of said prosthesis via signals from said sensor.

13. The leg prosthesis of claim 12, wherein said controller comprises an intra-modal controller and a supervisory gait controller, wherein said supervisory gait controller determines said intent of said user, said intent recognition coupled to modulate an output of said intra-modal controller.

14. The leg prosthesis of claim 12, wherein said intent recognition determines an activity mode of said prosthesis including at least one of standing, walking, ascending, descending, and sitting by comparing stored (recent) samples from said sensors to a stored sample database.

15. The leg prosthesis of claim 12, wherein said intent recognizer comprises a cadence estimator for estimating a cadence of the user based on the intervals of the ground reaction peaks from said sensor between consecutive strides.

16. The leg prosthesis of claim 15, wherein said cadence estimator modulates an output of said intra-modal controller based on said estimated cadence.

17. The leg prosthesis of claim 12, where said intent recognizer comprises a slope estimate for estimating a ground slope based on an accelerometer placed below the ankle joint for measuring foot accelerations in the frontal, sagittal, and axial planes.

18. The leg prosthesis of claim 17, wherein said slope estimator modulates an output of said intra-modal controller based on said estimated ground slope.

19. The leg prosthesis of claim 1, wherein said controller further comprises a sitting mode controller for determining a sitting phase of a user during a sitting mode.

20. The leg prosthesis of claim 19, wherein said sitting mode controller varies a power delivered to at least one of said ankle joint or said knee joint according to said sitting phase.

21. A method of controlling a powered leg prosthesis comprising at least one of an ankle and a knee joint, said leg prosthesis coupled to a user of said prosthesis, comprising:

representing behavior of said at least one joint as a plurality of different activity modes,

responsive to sensing of at least one input from said user, switching between said activity modes, wherein;

the behavior of the prosthesis within each activity mode is governed by an intramodal controller, wherein;

each intramodal controller consists of a number of internal phases,

responsive to sensing of at least one input initiated by said user, switching between said internal phases, wherein;

a torque is delivered to said at least one joint upon said switching between said phases, and

provided said phase remains unchanged, no net energy is delivered to said at least one joint.

22. The method of claim 21, wherein joint torques in said phases are each defined by an impedance-based function, said impedance-based function comprising a damping term and a stiffness term.

23. The method of claim 22, wherein said impedance-based function further comprises an equilibrium angle term that is differenced relative to a measured angle of said joint to generate an argument that is used for said stiffness term.

24. A powered leg prosthesis, comprising:

a powered knee joint comprising a knee joint and a knee motor unit for delivering power to said knee joint;

a prosthetic lower leg having a socket interface above said knee joint;

a powered ankle joint coupled to said lower leg opposite said knee joint comprising an ankle joint and an ankle motor unit to deliver power to said ankle joint;

a prosthetic foot including a ball and a heel;

at least one sensor for providing a sagittal plane moment, and ground interaction forces at said ball and at said heel, and

at least one controller coupled to said sensor for extracting real-time input from said user based on data from said sensor for controlling movement of said prosthesis.

25. The leg prosthesis of claim 24, further comprising a knee and ankle motor unit that delivers power to the joint using at least one among cable drive or a friction drive.