PSEUDO-PROPORTIONAL POSITION CONTROL OF WATER HYDRAULIC CYLINDER USING ON/OFF VALVES

Abstract

The paper studies the possibility to replace expensive water hydraulic proportional valve with a number of low-cost on/off valves. A position control system of a water hydraulic cylinder is realized with eight two-way solenoid valves and one four-way on/off valve. A pulse code modulation is used to achieve almost proportional control. A position controller based on multi-rate sampling is developed to minimize position error. Experimental results with a high inertial load show smooth movements, 0.2mm position accuracy and 200mm/s maximum velocity. The advantages and disadvantages of the on/off valve system are discussed.