Abstract
This paper deals with a sliding mode control algorithm when it is applied to an electro-hydraulic servo system. It is well known that, in such a servo system, a steady-state error can appear in time responses that originate from disturbances external to the system. We propose that, as a method for overcoming this problem, a disturbance observer be used in the sliding mode control algorithm. In the proposed algorithm, an input for the suppression of disturbance is estimated by the disturbance observer. It was verified by experiments and simulations that, in spite of the existence of unknown disturbances, the steady-state error and chatter phenomena were notably reduced by such use of a disturbance observer.
