Improvement of a Proportional Valve Dynamics by Means of a Peak & Hold Technique

As well known the performance of a closed or open control loop in hydraulic systems depends strongly on the dynamic behaviour of the directional valves. In this work a middle size proportional directional valve has been studied with a particular input Pulse Width Modulation (PWM) signal. The proportional solenoids of the tested valve have been supplied with a variable duty cycle PWM input signal to obtain a desired spool axial position. In particular an initial peak value of the supply current has been realized with a duty cycle value different from the duty cycle needed to obtain the target axial spool position. This technique has been used to improve the dynamics of the valve when the spool position changes from a lower metering section area to a greater one or vice versa. The results obtained by means of an experimental test rig will show the very important improvements that this new technique provides.