Robust Speed Control of a Variable-Displacement Hydraulic Motor Considering Saturation Nonlinearity

Abstract

This paper presents the speed control of a variable-displacement hydraulic motor on a constant pressure network, which is noted for its high system efficiency, fast dynamic response, and energy recovery capability. The speed control and response characteristics of the conventional cascade PI controller are considerably affected by load torque disturbances, variations in system parameters, and input magnitude. To obtain robust speed control under such conditions, the load torque is estimated by an observer and compensated for by a feedforward loop, and a windup compensator is used to prevent windup phenomena due to saturation of the regulating piston and integral controller. It is shown by experiment that improved speed control can be obtained with the proposed controller in spite of load torque disturbances, variations in system parameters, and input magnitude. [S0022-0434(00)00401-9]