Switching Control of a Linear Hydraulic Drive - Experimental Analysis

In this paper a rather simple hydraulic circuit for controlling a linear motion by means of two 2/2 way switching valves is studied experimentally. It is intended to replace proportional control of a hydraulic piston by switching control mainly to achieve a considerable cost reduction. Energy saving and recuperation - both being generally major aspects in the development of hydraulic switching control – are no issues in this paper. A key component for such a system is a low cost and fast switching valve (40 l/min @ 5bar, 1ms switching time) which can be operated in a pulse width mode. The proper design of the circuitry for limitation of pressure pulsation which are inevitably generated by the switching of the valve to an acceptable level is another challenge. To avoid flow force problems oil flow peaks in the switching valve have to be reduced by a proper arrangement of an inductance. For pressure pulsation attenuation different combinations of a hydraulic line and an accumulator are investigated. For system evaluation the major assessment criteria are noise level and cavitation avoidance and system response.