A CONTROL STRATEGY OF A 2-DOF PARALLEL MANIPULATOR WITH FRACTIONAL ORDER PDμ CONTROL

Liping Wang, Dong Wang, and Jun Wu

Keywords

Parallel manipulator, fractional order PDμcontrol, feedforwardcompensation

Abstract

This paper proposes a control strategy of a parallel manipulator with two rotational degrees of freedom. The control strategy consists of a feedback fractional order PDμ (FOPD) controller and a model-based dynamic feedforward compensation controller. The fractional order controller is designed in frequency domain through three appropriate constraints, which can ensure that the system is stable and has ideal crossover frequency, large phase margin and strong robustness. The feedforward controller is an open-loop compensator based on the inverse dynamic model, which can eliminate dynamic disturbance. To design the compensation controller, the dynamic model is established through the principle of virtual work. The control method is compared with a classical kinematic-based proportional derivative controller and an FOPD controller without dynamic feedforward compensation. The numerical results show that the tracking performance of the parallel manipulator is further improved when using the control strategy proposed in this paper even if the dynamic model is not accurate.

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