Systems and methods for adjusting the angle of a prosthetic ankle based on a measured surface angle

1. A method for operating a prosthetic ankle worn by a user, comprising:

providing a prosthetic ankle comprising a foot unit, a lower limb member, and at least one actuator having a first end connected to the foot unit and a second end connected to the lower limb member, the at least one actuator configured to adjust an ankle angle between the foot unit and the lower limb member, the foot unit and lower limb member configured to rotate at about a location of a natural human ankle;

measuring a degree of a surface angle of a surface upon which the user moves with the prosthetic ankle; and

actuating the at least one actuator to move the foot unit relative to the lower limb member to an ankle response angle, wherein the ankle response angle is determined by,

applying the measured surface angle degree to a first formula when the measured surface angle degree is less than zero degrees, and

applying the measured surface angle degree to a second formula when the measured surface angle degree is greater than zero degrees, the first formula being different than the second formula.

2. The method of claim 1 , wherein actuating the at least one actuator to move the foot unit relative to the lower limb member comprises decreasing the ankle response angle between about zero and thirty degrees when the measured surface angle degree is greater than zero degrees.

3. The method of claim 1 , wherein actuating the at least one actuator to move the foot unit relative to the lower limb comprises increasing the ankle response angle between about zero and thirty degrees when the measured surface angle degree is less than zero degrees.

4. The method of claim 1 , wherein the surface angle is measured using at least one sensor provided on the prosthetic ankle.

5. A method for operating a prosthetic ankle worn by a user, comprising:

providing a prosthetic ankle comprising a foot unit and a lower limb member, the foot unit and lower limb member configured to rotate at about a location of a natural human ankle;

measuring a degree of a surface angle of a surface upon which the user moves with the prosthetic ankle; and

adjusting an angle between the foot unit and the lower limb member to an ankle response angle based on the measured surface angle degree, wherein the ankle response angle is determined by,

applying the measured surface angle degree to a first formula when the measured surface angle degree is less than a predetermined angle, and

applying the measured surface angle degree to a second formula when the measured surface angle degree is greater than the predetermined angle, the first formula being different than the second formula.

6. The method of claim 5 , wherein adjusting an angle between the foot unit and the lower limb member comprises decreasing the ankle response angle between about zero and thirty degrees when the measured surface angle degree is greater than the predetermined angle.

7. The method of claim 5 , wherein adjusting an angle between the foot unit and the lower limb member comprises increasing the ankle response angle between about zero and thirty degrees when the measured surface angle degree is less than the predetermined angle.

8. The method of claim 5 , wherein the angle between the foot unit and lower limb member is adjusted with at least one actuator.

9. The method of claim 5 , wherein the surface angle is measured using at least one sensor provided on the prosthetic ankle.

10. A method for operating a prosthetic ankle worn by a user, comprising:

providing a prosthetic ankle comprising a foot unit and a lower limb member, the foot unit and lower limb member configured to rotate at about a location of a natural human ankle;

measuring a surface angle of a surface upon which the user moves with the prosthetic ankle;

calculating a desired angle between the foot unit and the lower limb member for moving upon the surface, wherein the calculation is based at least in part on the measured surface angle, wherein said calculating further comprises,

applying the measured surface angle to a first formula when the surface comprises a declined surface, and

applying the measured surface angle to a second formula when the surface comprises an inclined surface, the first formula being different than the second formula; and

adjusting an angle between the foot unit and the lower limb member to the desired angle.

11. The method of claim 10 , wherein the desired angle is a percentage of the measured surface angle for at least one of the surface comprising the declined surface and the surface comprising the inclined surface.

12. The method of claim 11 , wherein the desired angle is a percentage of the measured surface angle when the surface comprises the inclined surface.

13. The method of claim 10 , wherein the desired angle decreases in dorsiflexion from an angle of the prosthetic ankle in a neutral position when the surface comprises the inclined surface, and the desired angle increases in plantarflexion from an angle of the prosthetic ankle in the neutral position when the surface comprises the declined surface.

14. The method of claim 13 , wherein an amount that the desired angle decreases in dorsiflexion is larger relative to the measured surface angle of the inclined surface than an amount that the desired angle increases in plantarflexion relative to the measured surface angle of the declined surface.

15. The method of claim 14 , wherein the amount that the desired angle decreases in dorsiflexion is about 100% of the measured surface angle of the inclined surface, and the amount that the desired angle decreases in plantarflexion is between about 10% and 100% of the measured surface angle of the declined surface.

16. The method of claim 15 , wherein the amount that the desired angle decreases in plantarflexion increases nonlinearly as the measured surface angle of the declined surface increases.

17. The method of claim 10 , wherein an amount of angle adjustment to achieve the desired angle is between about 10% and 100% of the measured surface angle of the declined surface.

18. The method of claim 10 , wherein the measured surface angle is measured using at least one sensor provided on the prosthetic ankle.

19. The method of claim 10 , wherein an amount of ankle adjustment to achieve the desired angle on the declined surface changes approximately according to the formula y=−0.017x 2+ 0.1501x, wherein x is the surface angle and y is the response angle for achieving the desired angle between the foot unit and the lower limb member.

20. The method of claim 10 , wherein the desired angle is an increased angle relative to an angle of the prosthetic ankle in a neutral position when the measured surface angle corresponds to the declined surface.

21. The method of claim 10 , wherein the desired angle is a decreased angle relative to an angle of the prosthetic ankle in a neutral position when the measured surface angle corresponds the inclined surface.

22. The method of claim 1 , wherein at least one of the first and second formulas comprises a non-linear formula.

23. The method of claim 22 , wherein the second formula comprises a linear formula.

24. A method for operating a prosthetic ankle worn by a user, the method comprising:

measuring a surface angle of a surface upon which a user moves with a prosthetic ankle comprising a foot unit and a lower limb member, the foot unit and lower limb member configured to rotate at about a location of a natural human ankle;

calculating a desired angle between the foot unit and the lower limb member for moving upon the surface, wherein the calculation is based at least in part on the measured surface angle, wherein an amount of ankle adjustment to achieve the desired angle changes approximately according to the formula y=−0.017x 2+ 0.1501x, wherein x is the surface angle and y is the desired angle between the foot unit and the lower limb member; and

adjusting an angle between the foot unit and the lower limb member to the desired angle.