Application of fuzzy sliding mode iterative learning control algorithm in hydraulic servo system

The common P (proportion) type or PD (proportion and differential) type ILC (iterative learning control) is difficult to apply in a hydraulic servo system because of its low convergence rate. To improve the convergence rate, a new ILC based on a sliding mode fuzzy control is presented which combines a sliding mode control with ILC. The new algorithm makes use of the fast response merit of a sliding mode control to quicken the convergence of ILC. The fuzzy control in the algorithm can smooth the control signal and lessen the common dithering of sliding mode control. The FSMILC (fuzzy sliding mode iterative learning control) is an iterative learning control algorithm essentially, which takes the function of a sliding mode control as the input of fuzzy control and takes the fuzzy control output as the control increment of iterative learning control. The simulation results indicate that the new algorithm is effective, which can achieve higher speediness than that of iterative learning control of P type or PD type.