Identification of Dynamic Parameters of Modified LuGre Model and Application to Hydraulic actuator

Abstract

This paper deals with the identification of dynamic parameters included in the modified LuGre model and the identification method is applied to a hydraulic actuator. In order to simulate dynamic behaviors of friction of a hydraulic actuator well, Yanada and Sekikawa have modified the LuGre model by incorporating lubricant film dynamics into the LuGre model and have shown that the dynamic friction behaviors of a hydraulic actuator can be simulated by the modified LuGre model with a relatively good accuracy10). However, no method to identify the dynamic parameters included in the modified LuGre model has been proposed yet. In this paper, a method to identify the dynamic parameters, i.e., the time constant of lubricating film dynamics and the bristle stiffness is proposed. Using a single rod hydraulic cylinder, friction characteristics are experimentally investigated under various conditions of velocity variation under different supply pressures. The friction force of the hydraulic cylinder is measured based on the equation of motion using measured values of the pressures in the cylinder chambers and the acceleration of the hydraulic piston. Measured friction characteristics are compared with simulated ones by the modified LuGre model. It is shown that the dynamic behaviors of friction simulated using the parameters identified by the proposed method agree relatively well with those obtained by experiments and that the proposed identification method is appropriate. It is also shown that the time constant becomes longer under higher pressures and that the bristle stiffness does not depend on the pressure.