Prosthetic ankle and method of controlling same based on adaptation to speed
Prosthetic devices and methods of controlling the same are provided. A prosthetic ankle device includes a foot unit and lower limb member moveable relative to one another and defining an ankle angle therebetween. The prosthetic ankle device further includes a controller to operate the device using different ankle angles depending on, for example, a user's gait speed. Methods of controlling the prosthetic ankle device include operating the device at different ankle angles depending on gait speed. For example, the prosthetic ankle device can provide for relatively more dorsiflexion at relatively slower gait speeds and relatively more plantarflexion at relatively faster gait speeds.
1. A method of controlling a prosthetic ankle device, comprising:
providing the prosthetic ankle device, the prosthetic ankle device comprising a foot unit, a lower limb member configured to move relative to the foot unit, the foot unit and lower limb member defining an ankle angle therebetween, and an actuator configured to affect the ankle angle defined between the foot unit and the lower limb member, wherein the actuator comprises an active actuator configured to provide the movement between the foot unit and the lower limb member;
determining gait speed based on data provided by one or more sensors on the prosthetic ankle device; and
operating the active actuator of the prosthetic ankle device based on the determined gait speed, wherein:
at gait speeds less than a first threshold speed, the active actuator of the prosthetic ankle device is operated using a neutral ankle angle curve, wherein the neutral ankle angle curve represents a relationship between percent of completion of a stride of a user of the prosthetic ankle device and number of degrees of the ankle angle, wherein the first threshold speed is greater than zero;
at gait speeds at or above the first threshold speed and below a second threshold speed and traversed across a level surface, the active actuator of the prosthetic ankle device is operated using a first speed adaptive ankle angle curve that is shifted relative to the neutral ankle angle curve so that, for each percent of completion of the stride corresponding to a same percent completion of the stride on the neutral ankle angle curve, the prosthetic ankle device is more dorsiflexed than when the active actuator of the prosthetic ankle device is operated using the neutral ankle angle curve; and
at gait speeds at or above the second threshold speed and traversed across the level surface, the active actuator of the prosthetic ankle device is operated using a second speed adaptive ankle angle curve that is shifted relative to the neutral ankle angle curve so that, for each percent of completion of the stride corresponding to a same percent completion of the stride on the neutral ankle angle curve, the prosthetic ankle device is more plantarflexed than when the active actuator of the prosthetic ankle device is operated using the neutral ankle angle curve.
2. The method of claim 1 , wherein, at the gait speeds at or above the first threshold speed and below the second threshold speed, points on the first speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted by smaller amounts relative to the neutral ankle angle curve as the gait speed increases toward the second threshold speed.
3. The method of claim 2 , wherein, at the gait speeds at or above the first threshold speed and below the second threshold speed, points on the first speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted linearly by smaller amounts relative to the neutral ankle angle curve as the gait speed increases toward the second threshold speed.
4. The method of claim 1 , wherein, at the gait speeds at or above the second threshold speed and below a third threshold speed, points on the second speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted by greater amounts relative to the neutral ankle angle curve as the gait speed increases toward the third threshold speed.
5. The method of claim 4 , wherein, at the gait speeds at or above the second threshold speed and below the third threshold speed, points on the second speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted linearly by greater amounts relative to the neutral ankle angle curve as the gait speed increases toward the third threshold speed.
6. The method of claim 1 , wherein, at gait speeds at or above a third threshold speed that is greater than the second threshold speed and traversed across the level surface, the active actuator of the prosthetic ankle device is operated using a third speed adaptive ankle angle curve that is shifted relative to the neutral ankle angle curve so that, for each percent of completion of the stride corresponding to a same percent completion of the stride on the neutral ankle angle curve, the prosthetic ankle device is more plantarflexed than when the active actuator of the prosthetic ankle device is operated using the neutral ankle angle curve, and wherein points on the third speed adaptive ankle angle curve are shifted relative to the neutral ankle angle curve by a constant amount as the gait speed increases beyond the third threshold speed.
7. The method of claim 1 , wherein the prosthetic ankle device is operatively connected to a transtibial amputee.
8. The method of claim 1 , wherein the prosthetic ankle device is operatively connected to a transfemoral amputee.
9. The method of claim 8 , wherein the active actuator of the prosthetic ankle device is operated in combination with controlling a prosthetic knee.
10. The method of claim 9 , wherein the prosthetic knee is an actuatable prosthetic knee.
11. The method of claim 1 , wherein the angle defined between the lower limb member and the foot unit is adjusted based on the gait speed to change to one of the neutral ankle angle and speed adaptive ankle angle curves.
12. A prosthetic system, comprising:
a prosthetic ankle device comprising a foot unit, a lower limb member configured to move relative to the foot unit, the foot unit and lower limb member defining an ankle angle therebetween, and an actuator configured to affect the ankle angle defined between the foot unit and the lower limb member, wherein the actuator comprises an active actuator configured to provide the movement between the foot unit and the lower limb member; and
a controller configured to:
at gait speeds less than a first threshold speed, operate the active actuator of the prosthetic ankle device using a neutral ankle angle curve, wherein the neutral ankle angle curve represents a relationship between percent of completion of a stride of a user of the prosthetic ankle device and number of degrees of the ankle angle, wherein the first threshold speed is greater than zero;
at gait speeds at or above the first threshold speed and below a second threshold speed and traversed across a level surface, operate the active actuator of the prosthetic ankle device using a first speed adaptive ankle angle curve that is shifted relative to the neutral ankle angle curve so that, for each percent of completion of the stride corresponding to a same percent of completion of the stride on the neutral ankle angle curve, the prosthetic ankle device is more dorsiflexed than when the active actuator of the prosthetic ankle device is operated using the neutral ankle angle curve; and
at gait speeds at or above the second threshold speed and traversed across the level surface, operate the active actuator of the prosthetic ankle device using a second speed adaptive ankle angle curve that is shifted relative to the neutral ankle angle curve so that, for each percent of completion of the stride corresponding to a same percent completion of the stride on the neutral ankle angle curve, the prosthetic ankle device is more plantarflexed than when the active actuator of the prosthetic ankle device is operated using the neutral ankle angle curve.
13. The prosthetic system of claim 12 , further comprising one or more sensors to measure one or more variables indicative of the user's gait speed.
14. The prosthetic system of claim 12 , further comprising a prosthetic knee.
15. The prosthetic system of claim 12 , wherein, at the gait speeds at or above the first threshold speed and below the second threshold speed, points on the first speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted by smaller amounts relative to the neutral ankle angle curve as the gait speed increases toward the second threshold speed.
16. The prosthetic system of claim 15 , wherein, at the gait speeds at or above the first threshold speed and below the second threshold speed, points on the first speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted linearly by smaller amounts relative to the neutral ankle angle curve as the gait speed increases toward the second threshold speed.
17. The prosthetic system of claim 12 , wherein, at the gait speeds at or above the second threshold speed and below a third threshold speed, points on the second speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted by greater amounts relative to the neutral ankle angle curve as the gait speed increases toward the third threshold speed.
18. The prosthetic system of claim 17 , wherein, at the gait speeds at or above the second threshold speed and below the third threshold speed, points on the second speed adaptive ankle angle curve used to operate the active actuator of the prosthetic ankle device are shifted linearly by greater amounts relative to the neutral ankle angle curve as the gait speed increases toward the third threshold speed.
19. The prosthetic system of claim 12 , wherein, at gait speeds at or above a third threshold speed that is greater than the second threshold speed and traversed across the level surface, the active actuator of the prosthetic ankle device is operated using a third speed adaptive ankle angle curve that is shifted relative to the neutral ankle angle curve so that, for each percent of completion of the stride corresponding to a same percent completion of the stride on the neutral ankle angle curve, the prosthetic ankle device is more plantarflexed than when the active actuator of the prosthetic ankle device is operated using the neutral ankle angle curve, and wherein points on the third speed adaptive ankle angle curve are shifted relative to the neutral ankle angle curve by a constant amount as the gait speed increases beyond the third threshold speed.
20. The prosthetic system of claim 12 , wherein the prosthetic ankle device is operatively connected to a transtibial or transfemoral amputee.
21. The prosthetic system of claim 12 , further comprising a prosthetic knee, wherein the controller is further configured to control the prosthetic knee.