PID control performance of a water hydraulic servomotor system

In recent years water has been increasing used as a working fluid again, due to the global environmental problems. In this paper we develop the water hydraulic servo system by combining a servo valve and a hydraulic motor, and study the control performance of rotational angle. The problem encountered in the system is the existence of unmodeled dynamics, e.g., a large starting torque and friction force of water hydraulic servomotor, which cause the significant performance degradation. We composed the gain scheduled PID-controller that improves the large steady state error and overshoot. We have succeeded, to large extent, in attenuating the steady state error of the water hydraulic servomotor.