CONTROLLING POWER IN A PROSTHESIS OR ORTHOSIS BASED ON PREDICTED WALKING SPEED OR SURROGATE FOR SAME

• US 20140114437A1
• Filed: 12/20/2013
• Published: 04/24/2014
• Est. Priority Date: 04/05/2010
• Status: Active Grant

• Current Assignee: Otto Bock HealthCare LP (Nader Holding GmbH & Co. KG)
• Original Assignee: iWalk Incorporated (Ottobock SE & Co. KGaA)
• Inventors: Herr, Hugh Miller, Casler, Richard J. Jr., Han, Zhixiu, Barnhart, Christopher Eric, Girzon, Gary
• Granted Patent: US 9,693,883 B2
• Time in Patent Office: Days
• US Class Current: 623/24
• 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 2/74 fluid , i.e. hydraulic or pneumatic
• CPC Class Codes: A61F 2002/5003 having damping means, e.g. shock absorbers for implantable joints A61F2002/30563
• CPC Class Codes: A61F 2002/5007 having elastic means different from springs, e.g. including an elastomeric insert elastic coating A61F2002/3007; springs A61F2002/5072; plate-like springs for feet A61F2002/6657
• CPC Class Codes: A61F 2002/5018 for adjusting angular orientation
• 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 2002/607 Lower legs
• CPC Class Codes: A61F 2002/6685 S-shaped
• 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 2002/7645 for measuring torque, e.g. hinge or turning moment, moment of force
• CPC Class Codes: A61F 2002/7695 Means for testing non-implantable prostheses for testing implantable prostheses A61F2240/008; for implanting artificial joints A61F2/468
• CPC Class Codes: A61F 2005/0155 with actuating means
• CPC Class Codes: A61F 5/0127 for the feet A61F5/0111 takes precedence

Abstract

In some embodiments of a prosthetic or orthotic ankle/foot, a prediction is made of what the walking speed will be during an upcoming step. When the predicted walking speed is slow, the characteristics of the apparatus are then modified so that less net-work that is performed during that step (as compared to when the predicted walking speed is fast). This may be implemented using one sensor from which the walking speed can be predicted, and a second sensor from which ankle torque can be determined. A controller receives inputs from those sensors, and controls a motor'"'"'s torque so that the torque for slow walking speeds is lower than the torque for fast walking speeds. This reduces the work performed by the actuator over a gait cycle and the peak actuator power delivered during the gait cycle. In some embodiments, a series elastic element is connected in series with a motor that can drive the ankle, and at least one sensor is provided with an output from which a deflection of the series elastic element can be determined. A controller determines a desired torque based on the output, and controls the motor'"'"'s torque based on the determined desired torque.

Claims

1. An ankle-foot prosthesis or orthosis apparatus comprising:

a shank member;

a foot member that is operatively configured with respect to the shank member so as to support walking and permit the foot member to plantarflex and dorsiflex with respect to the shank member;

a motor configured to plantarflex the foot member with respect to the shank member;

a series elastic element connected between at least one of (a) the motor and the shank member and (b) the motor and the foot member;

at least one first sensor having an output from which a walking speed can be estimated; and

a controller configured to control the motor'"'"'s torque, based on the output of the at least one first sensor, so that the motor'"'"'s torque for slow walking speeds is lower than the motor'"'"'s torque for fast walking speeds.

2. The apparatus of claim 1, wherein the motor is also configured to dorsiflex the foot member with respect to the shank member.

3. The apparatus of claim 1, wherein the at least one first sensor comprises at least one of an angular rate sensor and an IMU.

4. The apparatus of claim 1, wherein the controller controls the motor'"'"'s torque based on the output of the at least one first sensor immediately before a reflex occurs.

5. The apparatus of claim 1, wherein the controller is configured to (i) determine, based on the output of the at least one first sensor, a control gain that varies with walking speed, wherein the control gain at slow walking speeds is lower than the control gain at fast walking speeds, (ii) determine a desired motor torque based on the control gain and a determined ankle torque, and (iii) drive the motor to achieve the desired motor torque.

6. The apparatus of claim 1, wherein the controller is configured to (i) determine, based on the output of the at least one first sensor, an angular rate ω

_x of the shank, (ii) determine a control gain Kv(ω

_x) that is a function of the angular rate, wherein the control gain at low angular velocities is lower than the control gain at low angular velocities, (iii) determine a desired motor torque based on the equation Motor torque=Kv(ω

_x)×

pff×

(normalized_Torque)ⁿ, where pff is a constant and n is between 2 and 7, and (iv) drive the motor to achieve the desired motor torque.

7. The apparatus of claim 6, wherein Kv(ω

_x)=0 when ω

_x=0, Kv(ω

_x)=1 when ω

_x exceeds a threshold ω

_TH, and Kv(ω

_x) is a monotonically increasing function between ω

_x=0 and ω

_TH.

8. The apparatus of claim 7, wherein the motor is also configured to dorsiflex the foot member with respect to the shank member.

9. The apparatus of claim 14, wherein the at least one second sensor measures ankle torque directly.

10. The apparatus of claim 14, wherein the at least one second sensor has at least one output from which a deflection of series elastic element can be determined, and the controller computes the torque based on the at least one output.

11. The apparatus of claim 14, wherein the at least one second sensor comprises a sensor that senses a position of the motor and a sensor that senses an angle of the foot member with respect to the shank member, and the controller computes the torque based on the sensed position of the motor and the sensed angle.

12. The apparatus of claim 14, wherein the at least one second sensor comprises a sensor that senses a position of the motor and a sensor that senses an angle of the foot member with respect to the shank member, and the controller determines a torque component Γ

_S based on the sensed position of the motor, the sensed angle, and a torque vs. deflection characteristics of the series elastic element.

13. The apparatus of claim 12, further comprising a bumper that is compressed when the foot member is sufficiently dorsiflexed with respect to the shank member,

wherein the controller determines a torque component Γ

_B based on the sensed angle and a torque vs. deflection characteristics of the bumper, and

wherein the controller determines a total torque based on Γ

_S and Γ

_B.

14. The apparatus of claim 1, further comprising at least one second sensor having an output from which ankle torque can be determined, and wherein the controller is configured to control the motor'"'"'s torque based on the output of the at least one second sensor.

15. The apparatus of claim 1, wherein control of the torque of the motor is based on non-linear positive feedback according to the output of the at least one first sensor.

16. The apparatus of claim 1, wherein the non-linear positive feedback involves adjustment of a parameter of a power control gain function, the parameter comprising at least one of a power control gain and a power exponent.