Hybrid control for induction servomotor drive

The position control of an induction servomotor drive using a hybrid control system is studied. The design of a hybrid control system contains three parts: (i) the design of a computed torque controller that compensates for nonlinear effects and attempts to cancel nonlinear terms; (ii) the design of an adaptive fuzzy sliding-mode uncertainty observer to estimate all uncertainties that exist in the controlled system; and (iii) the design of a robust controller to dispel the effect of the minimum approximation error introduced by the uncertainty observer. All parameters in the hybrid control system are tuned in the sense of the Lyapunov theorem, thus the stability of the closed-loop system can be guaranteed. Simulated and experimental results verify that the proposed hybrid control scheme can achieve a favourable tracking performance and is robust with regard to parameter variations and external load disturbances. In addition, the advantages of the proposed hybrid control system are indicated in comparison with the traditional computed torque and sliding-mode control systems.