Sliding mode control of a direct drive robot

The authors describe a two-level control scheme for an industrial robot. The inner loop realizes the linearization and the decoupling between the joint dynamics. In order to reduce the computational complexity of the decoupling and to enhance its robustness, a sliding-mode controller has been added to the nonlinear compensator for each joint. The outer loop effects the tracking of the desired trajectory using a discrete-time algorithm that can be easily implemented on a digital computer and allows the recovery of the previously accumulated errors in two sampling steps. The differences in applying the proposed scheme to direct-drive robots and to geared ones are presented. Simulation results validate the approach.<>