Powered method for augmenting a joint function of a human
A method for controlling a powered device to augment a joint function of a human during a gait cycle using a powered actuator that supplies an augmentation torque, an impedance, or both to a joint is disclosed. In some embodiments, the method modulates the augmentation torque, the impedance, and a joint equilibrium according to a phase of the gait cycle to provide at least a biomimetic response. Accordingly, the actuator is capable of normalizing or augmenting human biomechanical function, responsive to a wearer's activity, regardless of speed and terrain.
1. A method for augmenting a joint function of a human during a gait cycle, the method comprising:
providing a powered actuator configured to supply at least one of an augmentation torque and an impedance to a joint and a controller configured to modulate the augmentation torque and the impedance;
compute, using the controller, a normalized biomimetic torque for a phase of the gait cycle, the normalized biomimetic torque according to a speed of ambulation, a terrain, or both a speed of ambulation and a terrain;
retrieve, using the controller, a state-specific attenuation factor for the phase of the gait cycle;
scale, using the controller, the normalized biomimetic torque based on the state-specific attenuation factor to determine the augmentation torque; and
apply, using the powered actuator, the augmentation torque to the joint to provide at least a biomimetic response.
2. The method of claim 1 , wherein the impedance comprises at least one of a stiffness component, a damping component, and an inertial component, and further comprising modulating the impedance by determining at least one of the stiffness component and the damping component.
3. The method of claim 1 , wherein the impedance comprises a non-linear impedance, and further comprising modulating the impedance by determining a gain of the non-linear impedance and an exponent of the non-linear impedance.
4. The method of claim 1 , wherein the augmentation torque is modulated according to the phase of the gait cycle that is determined, at least in part, according to at least one of a direction of joint angular velocity, joint angular velocity, joint inertial rate, joint acceleration, or a joint torque applied to the joint.
5. The method of claim 1 , wherein the augmentation torque is supplied in addition to natural joint torque supplied by the human to achieve a pre-determined total joint torque response.
6. The method of claim 1 , wherein applying the augmentation torque comprises applying a closed-loop torque control at the joint.
7. The method of claim 4 , further comprising: modeling the joint torque applied to the joint; and determining the phase of the gait cycle based on a joint torque model.
8. The method of claim 1 , further comprising generating a kinematic reconstruction by kinematically reconstructing a path of a proximal link connected to at least one of the joint and another joint proximal to the joint, within the gait cycle.
9. The method of claim 8 , wherein the kinematic reconstruction comprises determining a terrain type as one of substantially level surface, sloping surface, and stairs.
10. The method of claim 9 , wherein the kinematic reconstruction comprises determining an activity according to the terrain type, the activity being one of ascending stairs, descending stairs, walking on substantially level surface, walking on a surface sloping up, and walking on a surface sloping down.
11. The method of claim 1 , wherein the impedance is supplied to the joint during a controlled plantar flexion phase of the gait cycle in order to mitigate foot slap.
12. The method of claim 1 , wherein the augmentation torque, the impedance, and a joint equilibrium are modulated in order to mitigate foot drop.
13. The method of claim 1 , wherein the augmentation torque, the impedance, and a joint equilibrium are modulated in order to provide a pre-determined net work according to at least one of the speed of ambulation and the terrain.
14. The method of claim 1 , wherein the augmentation torque is modulated according to a positive-force feedback.
15. The method of claim 14 , wherein the augmentation torque is modulated according to the positive-force feedback in combination with a natural joint torque supplied by the human to approximate a normal joint torque.
16. The method of claim 14 , wherein the positive-force feedback comprises a gain and an exponent.
17. The method of claim 16 , wherein at least one of the gain and the exponent is determined according to at least one of the speed of ambulation and the terrain.