Fast motion control of robot manipulators with inclusion of actuator dynamics

This paper contains an extension of a previous work (18) to include actuator limitations. A mathematical model for describing the complete dynamics of a robot manipulator is obtained by combining the non-linear and coupled dynamic equations of motion of a manipulator linkage with those for its actuators. The combined equations are then piecewise linearized and discretized to form a set of state difference equations by which a mathematical basis is provided for computer control and simulations. The adaptive control scheme and on-line computational scheme which were proposed in reference (18) are employed to drive robot manipulators to follow high-speed trajectories specified by continuous time functions. These schemes are briefly described in this paper. The control strategy involves a combination of feedforward and feedback control. The control delay associated with time taken for on-line computation is eliminated by a state-and-control prediction scheme. The emphasis in this paper is on the effectiveness of the control strategy and the computational scheme proposed and on the influences of actuator dynamics. Simulation results are compared with those of reference (18), in which perfect actuators were assumed. The inclusion of actuator dynamics in the modelling is shown to influence the controller design substantially. With appropriate controller design procedures, the tracking performance of the robot is shown to be very good.