Experimental evaluation of the nonlinear feedback robot controller

The trajectory tracking performance of the nonlinear feedback controller based on differential geometric control theory was experimentally studied. The performance is compared to three other methods: independent joint proportional-derivative (PD) control, independent joint PD control with feedforward torque computations, and the computed torque method. In the nonlinear feedback controller, servo is in the task space. In the other three methods servo is in the joint space. Path planning is in the task space. Circular and straight line paths are considered. A sampling frequency of 200 Hz is used. The effect of sampling frequency on tracking error is studied for the nonlinear feedback control scheme. The performance of these methods was tested on a PUMA 560 arm. The trajectory tracking performance of the robot arm under the nonlinear feedback controller is comparable to that of the computed torque control schemes