Sensorless position estimating and transition time identifying for the spool of a high speed on/off solenoid valve

In this paper, a sensorless method of detecting the spool position of a high-speed on/off solenoid valve is presented. The method depends on analyzing the time-current curve of the solenoid coil passing current and measuring the maximum stroke of the valve spool, such that the dynamic behavior of the valve is estimated and the spool displacement curve is plotted. A mathematical model of the solenoid valve is developed and the effect of the hydraulic force on the valve spool is studied. Experimental results show that the proposed method error is less than 7% when compared to valve spool displacement measured by the commonly used linear variable displacement transducer.