A NEW MODEL-BASED TRACKING CONTROLLER FOR ROBOT MANIPULATORS USING TRAJECTORY PATTERN INVERSE DYNAMICS

A new inverse-dynamics model-based tracking controller is presented. The inverse dynamics models are derived using the trajectory pattern method. The path of motion is divided into a number of relatively large segments, along which the motion is described by a selected trajectory pattern. The resulting inverse dynamics models are in the form of a summation of a fundamental sinusoidal time function and a number of its harmonics with constant coefficients. The coefficients are computed off-line using analytical expressions that are derived for the selected trajectory pattern. The structure of the inverse-dynamics models is fixed for all trajectory patterns and robot manipulators with the only difference being in the number of harmonics appearing in the inverse-dynamics model. The controller permits ultrahigh-speed generation of the desired trajectory and feedforward signals, as required for the control of lightweight robots operating at high speeds. The on-line computations are minimal and can all be performed in parallel. The computations can even be reduced to a single multiplication and a single addition per sample time. The inverse-dynamics model of a spatial 3R manipulator is derived for a specified trajectory pattern. The controller structure and simulation results indicating its effectiveness are presented.