Adaptive robust control for electrical cylinder with friction compensation using modified LuGre model

The position tracking control problem of an electrical cylinder in the presence of dynamic friction nonlinearities in its transmission process is addressed in this paper. First, a torque decoupling approach is proposed to formulate the dynamic model. Secondly, to compensate the friction in the case of servo motion, a modified LuGre model is designed to make a continuous transition between a static model at a high speed and a LuGre model at a low speed to avoid instability due to discretization with a finite sampling rate. To accelerate the speed of estimating time-varying parameters, a fast adaption law is proposed by designing an attraction domain around a rough value related to the load force. Finally, a discontinuous projection based adaptive robust controller is synthesized to effectively handle parametric uncertainties for ensuring a guaranteed robust performance. A Lyapunov stability analysis demonstrates that all signals including tracking errors have the guaranteed convergent and bounded performance. Extensive comparative simulations with sinusoidal and point-point tracks are obtained respectively in low and high speeds. The results show the effectiveness and the achievable control performance of the proposed control strategy.