HYDRAULIC FORCE CONTROL UNDER DISTURBANCES REALIZED AS PRESSURE CONTROL

Abstract

Hydraulic cylinders are typical actuators in force control applications. The friction force is the most serious disturbance of a force control, when the piston does not move. When the piston is moving the volume flow and changes in the controlled volume are disturbances. In this study the force control is realized as the piston side pressure control of a hydraulic cylinder. Three different ways to control the pressure are compared. The 3-way valve is used in this study. The influence of the piston movement and spring force on the performance of the force control is studied experimentally. The theoretical background of force and pressure controls is presented. Experimental results are shown and different solution compared. Two different ways to modify the conventional PI controller are presented and tuned to fulfill the system requirements.