Reactive layer control system for prosthetic and orthotic devices
A variable gain impedance controller for use in a control system for controlling a motorized prosthetic or orthotic apparatus provided with a joint. The controller comprises a sensor input for receiving a signal indicative of an interaction between the apparatus and the ground, a torque sensor input for receiving a signal indicative of the torque at the joint, and a variable gain scheduler in communication with the sensor input to receive data therefrom thereby providing a variable torque gain. The variable gain impedance controller adjusts its control on the apparatus based on the variable torque gain and the indicated torque to increase the joint resistance to motion when the signal received from the sensor input indicates an interaction between the apparatus and the ground, and decrease the joint resistance to motion when the signal received from the sensor input indicates an absence of interaction between the apparatus and the ground.
1. A method of modifying feedback of an impedance controller, the method comprising:
receiving, at the impedance controller, a first signal indicative of an interaction between a motorized prosthetic or orthotic apparatus and the ground, the apparatus including an actuator coupled to a prosthetic limb member, the actuator forming at least a portion of a joint of the apparatus;
receiving, at the impedance controller, a second signal indicative of torque at the joint;
based at least in part on the first signal, determining a torque feedback using the impedance controller, wherein during swing phase the impedance controller determines the torque feedback using at least the second signal and a first gain factor, wherein during stance phase the impedance controller determines the torque feedback using at least the second signal and a second gain factor that is different from the first gain factor; and
outputting a control signal to the actuator based at least in part on the torque feedback, wherein the actuator adjusts joint resistance to motion based at least in part on the control signal, wherein during the stance phase the control signal causes the actuator to increase the joint resistance to motion and during the swing phase the control signal causes the actuator to decrease the joint resistance to motion.
2. The method of claim 1 , wherein one of the first gain factor or the second gain factor is a positive value and the other one of the first gain factor or the second gain factor is a negative value.
3. The method of claim 1 , further comprising receiving, at the impedance controller, a third signal indicative of a position of the joint, wherein the control signal is further based at least in part on the third signal.
4. The method of claim 3 , further comprising:
determining a velocity of the joint based at least in part on the third signal; and
determining a braking feedback value based at least in part on a determination that the velocity satisfies a first threshold,
wherein the control signal is further based at least part on the braking feedback value so as to increase the joint resistance to motion.
5. The method of claim 4 , wherein the braking feedback value is based at least in part on a ratio of the velocity of the joint to a square of a position offset with a motion stop target of the apparatus.
6. The method of claim 5 , wherein the motion stop target of the apparatus is dynamically adjustable.
7. The method of claim 3 , wherein the control signal is further based at least in part on a difference between a position set-point and the position of the joint corresponding to the third signal.
8. The method of claim 3 , wherein said receiving the third signal comprises receiving the third signal from a position sensor.
9. The method of claim 1 , further comprising controlling the actuator to reduce joint flexion based at least in part on a determination that the first signal indicates an absence of interaction between the apparatus and the ground.
10. The method of claim 1 , wherein the first signal corresponds to a measure of load at a shank portion of the apparatus.
11. The method of claim 1 , wherein said receiving the first signal comprises receiving the first signal from a force sensor.
12. The method of claim 1 , further comprising determining a variable velocity gain based at least in part on the first signal, wherein the control signal is further based at least in part on the variable velocity gain.
13. The method of claim 12 , wherein the control signal is further based at least in part on a difference between a velocity set-point and a velocity estimation of the apparatus.
14. The method of claim 13 , further comprising determining the velocity estimation by applying an auto-regressive-moving-average process to the third signal.
15. The method of claim 1 , wherein said receiving the second signal comprises receiving the second signal from a torque sensor.
16. The method of claim 1 , further comprising determining a variable position gain based at least in part on the first signal, wherein the control signal is further based at least in part on the variable position gain.
17. The method of claim 1 , wherein the first gain factor is a unitary negative value, wherein the second gain factor is a unitary positive value.
18. The method of claim 17 , wherein the unitary positive value causes the actuator to increase the joint resistance to motion such that an increase in the torque at the joint causes the actuator to increase the joint resistance to motion, wherein the unitary negative value causes the actuator to decrease the joint resistance to motion such that an increase in the torque at the joint causes the actuator to decrease the joint resistance to motion.