Activation element and method

1. An apparatus, comprising:

a first member;

a second member that is movable relative to the first member; and

a hydraulic muscle element configured to move the second member relative to the first member, the hydraulic muscle element extending longitudinally between a first element end and a second element end;

wherein the hydraulic muscle element at the first element end is connected to the first member;

wherein the hydraulic muscle element is connected to the second member, and an end portion of the hydraulic muscle element at the second element end is wrapped about at least a portion of the second member; and

wherein an intermediate portion of the hydraulic muscle element is not wrapped around the first member or the second member.

2. The apparatus of claim 1 , wherein a longitudinal length of the end portion of the hydraulic muscle element changes as the second member moves relative to the first member.

3. The apparatus of claim 2 , wherein an effective force output of the hydraulic muscle element changes as the longitudinal length of the end portion of the hydraulic muscle element changes.

4. The apparatus of claim 1 , wherein

the hydraulic muscle element has an internal channel for receiving hydraulic fluid; and

at least a portion of the internal channel is within the end portion of the hydraulic muscle element and is substantially collapsed.

5. The apparatus of claim 1 , wherein

the hydraulic muscle element has an internal channel for receiving hydraulic fluid; and

at least a portion of the internal channel is within the end portion of the hydraulic muscle element and is open and operable to receive the hydraulic fluid.

6. The apparatus of claim 1 , wherein the end portion of the hydraulic muscle element is wrapped at least three-hundred and sixty degrees around the second member.

7. The apparatus of claim 1 , wherein the end portion of the hydraulic muscle element is wrapped less than three-hundred and sixty degrees about the second member.

8. The apparatus of claim 1 , wherein the wrapping of the end portion of the hydraulic muscle element about the at least a portion of the second member secures the hydraulic muscle element to the second member.

9. The apparatus of claim 1 , wherein the hydraulic muscle element has a nominal length when at rest, the hydraulic muscle element being connected to the first member at a first location, the hydraulic muscle element being wrapped about the second member at a second location, the first location being spaced a given distance from the second location, and the given distance being less than the nominal length of the hydraulic muscle element.

10. The apparatus of claim 1 , further comprising a joint between the first member and the second member, wherein the joint is configured to permit the first member to pivot about the joint relative to the second member.

11. The apparatus of claim 10 , wherein the joint comprises a hinge.

12. The apparatus of claim 1 , wherein the hydraulic muscle element comprises an internal elastic element and an outer sheath that limits the expansion of the internal elastic element.

13. The apparatus of claim 12 , wherein the outer sheath comprises a braided element.

14. The apparatus of claim 1 , wherein an end portion of the hydraulic muscle element at the first element end is wrapped about the first member.

15. The apparatus of claim 1 , wherein the first element end of the activation element is anchored to the first member.

16. The apparatus of claim 1 , wherein the second member has a post, and the end portion of the hydraulic muscle element is wrapped about the post.

17. The apparatus of claim 1 , wherein the hydraulic muscle element comprises a plurality of independent hydraulic activation elements in a bundle.

18. The apparatus of claim 17 , wherein the plurality of independent hydraulic activation elements are operable to be independently activated and controlled to at least vary a power output of the bundle by selectively activating and controlling a select number of elements.