The effects of unmodeled forces on robot control

The implementation feasibility and performance improvement potential of techniques for compensation of six degree of freedom manipulator forces unmodeled by Lagrange-Euler dynamics have been evaluated on a PUMA manipulator by analysis of their impact on the accuracy of the computed-torque control algorithm. The effects of improved inertial parameter measurements, feedforward friction compensation and PD and PID feedback strategies have been identified. More accurate inertial parameters have negligible impact on trajectory tracking ability. Implementation of nonlinear friction compensation in the feedforward loop is undesirable. Feedback compensation techniques permit tracking accuracy sufficient for gross motion control of a PUMA manipulator without additional instrumentation.