FIG. 6.

For the revolute joint, two separate PID controllers commanded a desired force for each actuator in reaction to estimated joint angle error terms e_i. When the Smart Braids were used for feedback, e_i were determined individually from the measured inductance and pressure. When the encoder was used for feedback, e_i were equal. To generate the desired forces, the controller computed desired pressure values from a model of the actuator force-pressure-length relationship and sent these values to two pressure control valves.