A new variable structure control scheme which consists of continuous adaptive gain feedback (PID and feed-forward controls is developed to achieve accurate decoupled model following in a class of nonlinear time-varying system in the presence of disturbances, parameter variations and nonlinear dynamic interactions. The method is based on modified model following control with an improved sliding mode, which results in reducing the undesirable chattering remarkably. In addition an external torque observer with which the effects of external disturbances including parameter variations are roughly canceled is constructed. Then the developed method is practically applied to decoupled model following motion control for a two-degrees-of-freedom manipulator powered by PWM transistor converter-fed servo motors. The overall control strategies are implemented with both NEC PC-9801F (Intel 8086 Microprocessor) and TITMS32020 (DSP). The DSP is a very attractive hardware for the realization of the robust and fast observer algorithm. It is confirmed by experiments that the position trajectories are smooth and track the desired trajectories (output models) accurately. It is found that this new controller is simple and easy to be designed, performs extremely satisfactorily and is superior to the “conventional” PID controller for the robot manipulator.
MICROPROCESSOR-BASED NOVEL VARIABLE STRUCTURE CONTROL FOR ROBOT MANIPULATOR
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