APPLICATION OF AN ADAPTIVE MODEL FOLLOWING CONTROL TECHNIQUE TO A HYDRAULIC SERVO SYSTEM SUBJECTED TO UNKNOWN DISTURBANCES

This paper deals with a position control of hydraulic servo systems subjected to unknown and time-varying external load disturbances. Since hydraulically operated processes are often subjected to unknown disturbances, an adaptive model following control (AMFC) scheme was derived based upon the Liapunov's Direct Methods which was employed by Monopoli (1981). As an adaptation criterion this method utilizes an ultimate boundary of the uncertain parameters associated with the plant dynamics and the unknown disturbances. The performance of the derived adaptive controller is evaluated through simulation and experimental studies. The results show that the proposed AMFC is fairly insensitive to unknown and time-varying external load disturbances, yielding much better response characteristics, compared with those of a conventional constant PI feedback controller.