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A position control of a class of servomotors is addressed in this paper via a novel adaptive fuzzy PI sliding mode control. The premise and the consequence parts of the fuzzy rules are tuned with adaptive schemes. To attenuate chattering effectively, the discontinuous control is approximated by an adaptive PI control structure. Moreover, the bound of the discontinuous control term is assumed to be unknown, and an adaptive mechanism is used to estimate this bound. All adaptive laws are derived via Lyapunov synthesis method, thereby guaranteeing the closed-loop stability. The proposed approach has the added advantage that, for external disturbances, it only requires a bound to exist, without needing to know the magnitude of this bound. The proposed controller is applied to control a model of uncertain induction servomotor subject to significant disturbances and a model of DC servomotor with unknown parameters and uncertainty in load condition. The analysis of simulations reveals the effectiveness of the proposed method in controlling servomotors in terms of significant reduction in chattering while maintaining asymptotic convergence.
Date of Publication: March 2008