Sliding mode compensation of inverse dynamics velocity control

Direct drive manipulators operate at high speeds, because the reduction gears are eliminated for accurate positioning of the end effector. Obviously, inverse dynamics velocity control is a suitable choice for the control of direct drive manipulator to tackle the dynamic effects due to its high speed operation. However, uncertainty in the dynamic model, and also in the inverse dynamic model, of the manipulator deteriorates its tracking performance. This paper presents a novel approach of inverse dynamics velocity control of direct drive manipulator based on sliding mode compensation technique. The compensated inverse dynamics velocity control scheme is robust against the ill-effects of the model uncertainties and exhibits robust tracking performance of the desired velocity trajectories in the robot joint space. Moreover, the proposed inverse dynamic controller can be designed based on the nominal dynamic model, thus eliminating the need for the online calculation of the computation intensive time varying parameters of the robot dynamic model. The effectiveness of the proposed control algorithm has been validated in the simulation considering a 3 DOF direct drive manipulator model.