Abstract: The main idea of adaptive control design theory based on the error polynomial algebra is to make the adaptive control error incline to zero as time passed. It can make the adaptive control system be steady on the basis of the theory of LIAPUNOV A M. An adaptive control method adapted to the asymmetric cylinder hydraulic servo system controlled by symmetric valve is presented to make the output of the system follow the output of the reference model progressively, so that the problems of dynamic performance asymmetry, low accuracy, low stability, narrow bandwidth and big delay are resolved.

Key words: Adaptive control, Error polynomial, Model reference, Servo valve asymmetric cylinder