Artificial Ankle-Foot System with Spring, Variable-Damping, and Series-Elastic Actuator Components

• US 20130110256A1
• Filed: 12/21/2012
• Published: 05/02/2013
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Herr, Hugh M., Dilworth, Peter, Au, Kwok Wai Samuel, Paluska, Daniel Joseph
• Granted Patent: US 8,734,528 B2
• Time in Patent Office: Days
• US Class Current: 623/24
• CPC Class Codes: A61F 2/60 Artificial legs or feet or parts thereof
• CPC Class Codes: A61F 2/605 Hip joints
• CPC Class Codes: A61F 2/64 Knee joints
• CPC Class Codes: A61F 2/6607 Ankle joints
• CPC Class Codes: A61F 2/68 Operating or control means
• CPC Class Codes: A61F 2/70 electrical
• CPC Class Codes: A61F 2002/5004 operated by electro- or magnetorheological fluids
• CPC Class Codes: A61F 2002/5006 Dampers, e.g. hydraulic damper
• CPC Class Codes: A61F 2002/503 for adjusting elasticity, flexibility, spring rate or mechanical tension
• CPC Class Codes: A61F 2002/5033 for adjusting damping damping means A61F2002/5003
• CPC Class Codes: A61F 2002/5073 Helical springs, e.g. having at least one helical spring
• CPC Class Codes: A61F 2002/5075 Multiple spring systems including two or more helical springs
• CPC Class Codes: A61F 2002/5079 Leaf springs A61F2002/6657 takes precedence
• CPC Class Codes: A61F 2002/509 specially designed for children, e.g. having means for adjusting to their growth implantable A61F2250/0082
• 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 2002/6678 L-shaped
• CPC Class Codes: A61F 2002/6818 for braking
• 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 2002/7625 for measuring angular position
• CPC Class Codes: A61F 2002/763 : for measuring spatial position, e.g. global positioning system [GPS]
• 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: B25J 19/0008 : Balancing devices
• CPC Class Codes: B62D 57/032 : with alternately or sequentially lifted supporting base and legs; with alternately or sequentially lifted feet or skid B62D57/024 takes precedence

Abstract

An artificial foot and ankle joint consists of a curved leaf spring foot member having a heel extremity and a toe extremity, and a flexible elastic ankle member that connects the foot member for rotation at the ankle joint. An actuator motor applies torque to the ankle joint to orient the foot when it is not in contact with the support surface and to store energy in a catapult spring that is released along with the energy stored in the leaf spring to propel the wearer forward. A ribbon clutch prevents the foot member from rotating in one direction beyond a predetermined limit position. A controllable damper is employed to lock the ankle joint or to absorb mechanical energy as needed. The controller and sensing mechanisms control both the actuator motor and the controllable damper at different times during the walking cycle for level walking, stair ascent, and stair descent.

Claims

1. A device comprising:

a mechanical leg joint;

a controllable actuator to exert a torque about the joint, the actuator comprising;

a motor; and

a spring operatively coupled with the motor;

an artificial sensory system comprising at least one sensor selected from the group consisting of a position sensor, a velocity sensor, a gyroscope, an accelerometer, and a force sensor; and

an operative connection to the motor and the at least one sensor, wherein the device is adapted to store elastic energy during one phase of a gait cycle and to release elastic energy during a subsequent phase of the gait cycle to augment power output of the joint.

2. The device of claim 1, wherein the mechanical joint comprises an ankle joint.

3. The device of claim 2, wherein the motor is adapted to deflect the spring during controlled dorsiflexion for later release during powered plantar flexion.

4. The device of claim 3, wherein the motor is controlled to store spring energy over a longer period of time than the amount of time to release the spring energy.

5. The device of claim 1, further comprising a stop adapted to prevent rotation of the joint beyond a predetermined limit.

6. A device comprising:

a mechanical ankle joint;

a motor adapted to exert a torque about the ankle joint;

an artificial sensory system comprising at least one sensor selected from the group consisting of a position sensor, a velocity sensor, a gyroscope, an accelerometer, and a force sensor; and

an operative connection to the motor and the at least one sensor,

wherein the operative connection is adapted to output a control sequence for stair or slope descent in which during a swing phase an angle of the ankle joint is reoriented for toe-first contact and in which during a stance phase a damping response is subsequently applied during controlled dorsiflexion.

7. A device comprising:

a mechanical ankle joint;

an artificial elastic element adapted to store elastic energy;

a motor adapted to exert a torque about the ankle joint;

a stop for limiting rotation of the ankle joint;

at least one sensor; and

an operative connection to the motor and the at least one sensor, wherein the operative connection is adapted to control at least one of joint stiffness, equilibrium position, damping, and torque.

8. The device of claim 7, wherein the elastic element is in series with the motor such that, when the joint is locked, the elastic element can be compressed or stretched by the motor in series to the elastic element without the joint rotating.

9. The device of claim 7, wherein the elastic element amplifies joint power output during a stance phase.

10. The device of claim 7, wherein the elastic element is adapted to store energy over a longer period of time than that during which the energy is released.

11. The device of claim 7, wherein the elastic element is adapted to store energy when the stop is engaged.

12. The device of claim 7, wherein the sensor comprises an inertial measurement unit.

13. The device of claim 7, wherein the operative connection is adapted to determine elevation and is further adapted to reset determined elevation to zero when non-gravitational acceleration is zero.

14. The device of claim 7, wherein the operative connection is adapted to determine elevation after toe-off

15. The device of claim 7, wherein the operative connection is adapted to control an angle of the ankle joint during a swing phase in response to terrain.

16. The device of claim 15, wherein the operative connection controls the ankle angle to provide toe strike when the elevation change is negative relative to the elevation when the foot last left the ground.

17. The device of claim 7, wherein the operative connection is adapted to output control signals to adjust the ankle joint angle during a swing phase of stair descent.

18. The device of claim 7, further comprising a variable damper operatively connected to the motor.

19. The device of claim 18, wherein the elastic element is adapted to store energy when the variable damper is set at a sufficiently high damping level.

20. The device of claim 18, wherein at least one of the motor and the variable damper are programmable.

21. The device of claim 7, wherein the stop is unidirectional such that engagement occurs at a predefined ankle joint position to resist dorsiflexion movement.

22. The device of claim 7, wherein the stop is positioned in parallel with the motor.

23. The device of claim 7, wherein the operative connection is adapted to compute torque based on a displacement of the elastic element.

24. The device of claim 7, wherein the operative connection is adapted to compute motor velocity.

25. The device of claim 7, wherein the operative connection is adapted to control at least one of joint stiffness, equilibrium position, damping, and torque, which at least one parameter comprises at least one of gait cycle phase, walking speed, elevation and terrain.

26. An artificial joint system comprising:

an artificial joint;

an artificial actuator for actuating the joint;

an artificial sensory system comprising at least one inertial measurement unit adapted to be positioned on a component of the system; and

an operative connection adapted to compute absolute orientation and displacement of the joint system based on information from the sensory system, and to reset operative connection computations upon the detection of an absence of non-centrifugal, non-gravitational linear acceleration.

27. The system of claim 26, wherein the operative connection is adapted to determine at least one of velocities of interior points of the system and an absolute movement pattern of the joint.

28. The system of claim 26, wherein the sensory system further comprises at least one position sensor adapted to measure joint angle.

29. The system of claim 26, wherein the operative connection is adapted to distinguish between level ground walking and descending or ascending one of stairs and a steep incline.

30. The system of claim 26, wherein the operative connection is adapted to control at least one of joint stiffness, equilibrium position, damping, and torque, in accordance with at least one parameter determined by the controller, which at least one parameter comprises at least one of gait cycle phase, walking speed, elevation and terrain.