Hip exoskeleton

1. An exoskeleton wearable on a body of a human having two legs, the exoskeleton comprising: a first HAA joint and a second HAA joint configured to assist the human with leg abduction and adduction movements at a hip of the body, wherein the leg abduction and adduction movements are parallel to a frontal plane, each of the first and the second HAA joints having an actuator, each actuator including a low-level controller, a motor, a torque sensor, and a clutch, the low level controller configured to calculate an interaction torque that represents a difference between a trajectory of a respective leg of the two legs and a trajectory of the respective first HAA joint or the second HAA joint using data sensed by the torque sensor, wherein the interaction torque is a torque that exists between the exoskeleton and the human; a sensor system for measuring a combined center of mass of the human and the exoskeleton in the frontal plane and a step width of the human in the frontal plane; and a high-level controller that outputs adjustment angles for each of the first and the second HAA joints based on the center of mass and the step width; wherein the first and the second HAA joints are respectively rotated based on the respective output adjustment angles, and wherein the clutch of each actuator is configured to be selectively disengaged from the respective motor during rotation of the respective first HAA joint or the second HAA joint based on the calculated interaction torque, to disconnect the actuator from the respective first HAA joint and second HAA joint and allow the hip to function on its own under the influence of gravity; wherein each low-level controller is configured to control a rotation of the first HAA joint or the second HAA joint using both the adjustment angles output by the high-level controller and the interaction torque measured by the respective torque sensor of the first HAA joint or the second HAA joint.

2. The exoskeleton of claim 1 , wherein each actuator includes a spring that has a double spiral disc shape and a stiffness of 2.15 Nm/degree.

3. The exoskeleton of claim 1 , wherein the torque sensor is a spring-based torque sensor.

4. The exoskeleton of claim 3 , wherein the spring-based torque sensor includes four strained beams, each having a rectangular groove.

5. The exoskeleton of claim 1 , wherein the controller includes a high-level sub-system including the high-level controller and a low-level sub-system including the low-level controller, and wherein the high-level sub-system is controlled by a finite-state-machine and uses the combined center of mass of the human and the exoskeleton in the frontal plane and the step width of the human in the frontal plane to determine the adjustment angles for each of the respective first and the second HAA joints.

6. The exoskeleton of claim 1 , further comprising a back support, a first leg support, and a second leg support, the first HAA joint being operatively coupled between the back support and the first leg support and the second HAA joint being operatively coupled between the back support and the second leg support.

7. The exoskeleton of claim 1 , wherein the sensor system includes a foot-pressure sensor array, the foot-pressure sensor array configured to detect foot-ground contact events.

8. The exoskeleton of claim 1 , wherein each actuator includes a transmission, wherein each clutch is a mechanical clutch configured to automatically disengage and engage the transmission.

9. The exoskeleton of claim 1 , wherein each clutch is an electromagnetic tooth-type clutch.