Prosthetic simulator with soft tissue modeling

• US 20070051180A1
• Filed: 08/14/2006
• Published: 03/08/2007
• Est. Priority Date: 08/12/2005
• Status: Active Grant

• Current Assignee: Advanced Mechanical Technologies, Inc.
• Original Assignee: Advanced Mechanical Technologies, Inc.
• Inventors: White, Bruce
• Granted Patent: US 7,823,460 B2
• Time in Patent Office: Days
• US Class Current: 73/760
• CPC Class Codes: A61F 2/24 Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/38 for elbows or knees
• CPC Class Codes: A61F 2/3804 for elbows
• CPC Class Codes: A61F 2/3859 Femoral components
• CPC Class Codes: A61F 2/389 Tibial components A61F2/3868 takes precedence
• CPC Class Codes: A61F 2/40 for shoulders
• CPC Class Codes: A61F 2/4202 for ankles
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• CPC Class Codes: A61F 2/468 Testing instruments for artificial joints for testing non-implantable prostheses A61F2/76

Abstract

A virtual soft tissue control system that provides enhanced motion control to a prosthetic simulator machine. The prosthetic simulator provides a non-human environment in which to evaluate new and existing prosthetic devices, particularly implantable prosthetic devices, through accelerated life testing. The control system advantageously adds a “virtual soft tissue” control scheme to a conventional control system, such as a digital proportional integral derivative (PID) controller, to algorithmically model the soft tissue constraints that would be encountered by the prosthesis within the human body, and account for these forces in driving the simulator. In another aspect, a prosthetic simulator comprises a prosthetic drive mechanism; a feedback control system that drives the prosthetic drive mechanism; and an iterative learning control system that determines an error from a previous iteration of motion of the drive mechanism and uses the error to determine a drive signal for a subsequent iteration of motion. In certain embodiments, the prosthetic simulator uses both a soft tissue model and an iterative learning control system.

Claims

1. A simulator for an implantable prosthetic element, comprising

a prosthetic drive mechanism;

a sensor for measuring the force or torque applied to the prosthetic element; and

a control system responsive to the sensor and to a simulation input, wherein the control system includes a soft tissue model to account for soft tissue action to drive the drive mechanism.

2. The simulator of claim 1, wherein the soft tissue model comprises an algorithmic model of the soft tissue constraints encountered by the prosthetic element when implanted in a human or animal body.

3. The simulator of claim 1, further comprising a position sensor for measuring the position of the prosthetic element, the control system being responsive to the position sensor.

4. The simulator of claim 3, wherein the control system modifies the simulation input to account for soft tissue action based on a measurement of the position sensor.

5. The simulator of claim 3, wherein the control system comprises a nested loop design.

6. The simulator of claim 5, wherein an inner loop of the nested loop design comprises a proportional integral derivative (PID) controller that drives the drive mechanism based on the simulation input and feedback from the sensor for measuring the force or torque applied to the prosthetic element.

7. The simulator of claim 6, wherein an outer loop of the nested loop design comprises a virtual soft tissue controller that modifies the simulation input based on feedback from the position sensor and an algorithmic model of the soft tissue constraints.

8. The simulator of claim 1, wherein the drive mechanism comprises a hydraulic actuator.

9. The simulator of claim 1, wherein the simulation input comprises a waveform representing active musculature forces of a human or animal.

10. The simulator of claim 1, wherein the prosthetic element comprises a prosthetic knee.

11. The simulator of claim 1, wherein the prosthetic element comprises a prosthetic hip.

12. The simulator of claim 1, wherein the prosthetic element comprises at least one of a prosthetic hip, shoulder, elbow, spine, ankle, heart, and heart valve.

13. The simulator of claim 1, further comprising:

an iterative learning control system that determines an error from a previous iteration of motion of the drive mechanism and uses the error to determine a drive signal for a subsequent iteration of motion.

14. A control system for use in a simulator for a prosthetic element, the control system comprising a soft tissue model.

15. A simulator for an implantable prosthetic element, comprising:

a prosthetic drive mechanism;

a feedback control system that drives the prosthetic drive mechanism; and

an iterative learning control system that determines an error from a previous iteration of motion of the drive mechanism and uses the error to determine a drive signal for a subsequent iteration of motion.

16. The simulator of claim 15, wherein the feedback control system receives feedback data regarding the force or torque applied to the prosthetic element during an iteration of motion of the drive mechanism.

17. The simulator of claim 15, wherein the feedback control system receives feedback data regarding the position of the prosthetic element during an iteration of motion of the drive mechanism.

18. The simulator of claim 15, wherein the drive mechanism comprises a hydraulic actuator.

19. The simulator of claim 15, wherein the prosthetic element comprises a prosthetic knee.

20. The simulator of claim 15, wherein the prosthetic element comprises a prosthetic hip.

21. The simulator of claim 15, wherein the prosthetic element comprises at least one of a prosthetic hip, shoulder, elbow, spine, ankle, heart, and heart valve.

22. The simulator of claim 15, further comprising a soft tissue model, the drive mechanism being responsive to the soft tissue model.

23. A method for controlling a simulator for an implantable prosthetic element, comprising

measuring the force or torque applied to the prosthetic element;

measuring the position of the prosthetic element;

driving the prosthetic element based on the measured torque or force, the measured position of the prosthetic element, and an algorithmic model of soft tissue constraints.

24. A method for controlling a simulator for an implantable prosthetic element, comprising

determining an error from a previous iteration of motion of a prosthetic drive mechanism;

and

using the error to determine a drive signal for a subsequent iteration of motion.