Exoskeleton cord loop-type actuator

1. An exoskeleton comprising:

a first support structure configured to be coupled to a wearer of the exoskeleton;

a second support structure configured to be coupled to the wearer of the exoskeleton;

a joint connecting the first and second support structures, the joint being configured to enable relative movement between the first and second support structures;

a first cord loop connecting the first and second support structures;

a second cord loop connecting the first and second support structures;

at least one motor configured to twist and thereby shorten the first and second cord loops, wherein shortening of the first cord loop causes relative pivotal movement of the first and second support structures about the joint in a first direction, and shortening of the second cord loop causes relative pivotal movement of the first and second support structures about the joint in a second, opposite direction; and

a brake configured to prevent relative movement of the first and second support structures about the joint in at least one of the first and second directions when one of the first and second cord loops breaks.

2. The exoskeleton of claim 1 , wherein:

the brake includes a gear coupled to the second support structure;

the brake includes a first pawl coupled to the first support structure;

the brake is configured such that the first pawl contacts the gear when the first cord loop breaks; and

the brake is configured such that contact between the first pawl and the gear prevents relative movement of the first and second support structures about the joint in at least one of the first and second directions.

3. The exoskeleton of claim 2 , wherein:

the brake includes a first pulley configured to contact the first cord loop;

the brake is configured such that contact between the first pulley and the first cord loop prevents contact between the first pawl and the gear;

the brake includes a first spring configured to apply a force to the first pawl; and

the brake is configured such that the first spring causes the first pawl to contact the gear when the first cord loop breaks.

4. The exoskeleton of claim 3 , wherein:

the brake includes a second pawl;

the brake is configured such that the second pawl contacts the gear when the second cord loop breaks;

the brake is configured such that contact between the second pawl and the gear prevents relative movement of the first and second support structures about the joint in at least one of the first and second directions;

the brake includes a second pulley configured to contact the second cord loop;

the brake is configured such that contact between the second pulley and the second cord loop prevents contact between the second pawl and the gear;

the brake includes a second spring configured to apply a force to the second pawl; and

the brake is configured such that the second spring causes the second pawl to contact the gear when the second cord loop breaks.

5. The exoskeleton of claim 1 , wherein the at least one motor includes a first motor configured to twist the first cord loop and a second motor configured to twist the second cord loop.

6. The exoskeleton of claim 1 , wherein the at least one motor includes a single motor configured to simultaneously twist, in opposite rotational directions, both the first and second cord loops.

7. The exoskeleton of claim 6 , further comprising an input shaft, a first spindle coupled to the first cord loop and a second spindle coupled to the second cord loop, wherein:

the single motor is configured to cause rotation of the input shaft;

the input shaft is configured to cause rotation of the first and second spindles;

the first spindle is configured to twist the first cord loop; and

the second spindle is configured to twist the second cord loop.

8. The exoskeleton of claim 7 , further comprising:

a first spring configured to reduce slack in the first cord loop; and

a second spring configured to reduce slack in the second cord loop.

9. The exoskeleton of claim 1 , further comprising a spindle coupled to one of the first and second cord loops, the spindle including a cord slot and a first cord guide, wherein the one of the first and second cord loops passes through the cord slot and contacts the first cord guide.

10. The exoskeleton of claim 9 , wherein the first cord guide is wedge-shaped such that no gap exists between the first cord guide and a twisted helical cord structure of the one of the first and second cord loops when the one of the first and second cord loops is twisted by the at least one motor.

11. The exoskeleton of claim 9 , further comprising a strand separator including a second cord guide, wherein:

the one of the first and second cord loops passes through the strand separator and contacts the second cord guide; and

the strand separator is configured such that a twisted helical cord structure of the one of the first and second cord loops only exists between the spindle and the strand separator when the one of the first and second cord loops is twisted by the at least one motor.

12. The exoskeleton of claim 11 , wherein the second cord guide is wedge-shaped such that no gap exists between the second cord guide and the twisted helical cord structure when the one of the first and second cord loops is twisted by the at least one motor.