Performance comparison of four manipulator servo schemes

Using experimental results on trajectory tracking performance of four servo schemes, a comparison is made of nonlinear task-level and joint-level servo schemes. Tracking performance is also compared for two other joint-level servo schemes: independent joint proportional-derivative (PD) control, and PD control with feedforward torque computations. These four algorithms are implemented on a six-degree-of-freedom PUMA 560 arm. Task planning was done in the six-dimensional task space of Cartesian position and an orientation representation corresponding to Unimation´s OAT convention. A reduced dynamic model was used and all schemes were compared at a servo rate of 185 Hz. The importance of the dynamical model in the control of the PUMA 560 manipulator is elicited. The effect of sampling rate on tracking performance is experimentally studied.<>