Sensorless Plunger Position Control for a Switching Solenoid

Abstract

In this study, the sensorless control algorithm is applied to improve the position control accuracy of the output plunger of a switching solenoid. The main purpose of this study is the attempt to develop a fluid-technical proportional valve with simplest construction and lowest cost. Since the switching solenoid is not equipped with a position sensor and consequently no closed-loop control theory can be applied, the accuracy of the position control of the output plunger becomes a most critical question. Therefore, a modified open-loop controller using the sensorless control algorithm is proposed. The basic idea is the utilization of the sensorless control algorithm to estimate the steady-state position of the plunger. Then, this estimated position is fedback to the controller and the input current during the steady-state response is real-time adjusted according to the error signal. Finally, a series of experiments are carried out and the results show that the proposed modified open-loop controller improves significantly the steady-state accuracy of the plunger position and provides an alternative approach to design unconventional proportional valves.

Sensorless position detection in solenoid valve based on inductance model

“…The second term refers to EMF caused by current changes and the third refers to motion electromotive force caused by movement. Literature [8] shows that the third movement electromotive force in solenoid valve under normal operating conditions has little effect on voltage. Fig.…”

“…Coil inductance L depends on the moving iron core displacement x and input current I. According to Kirchhoff's law and Faraday's law, voltage balance equation could be established [8]:…”

A Solution to Ambiguities in Position Estimation for Solenoid Actuators by Exploiting Eddy Current Variations

“…State-of-the-art techniques for sensorless position detection of solenoid actuators can be divided into three categories: observer based on the back-induced electromotive force (back-EMF) [ 7 , 8 ], identification of the differential inductance [ 4 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ] and identification of eddy current losses [ 23 , 27 , 28 ]. Observer-based techniques exploit the back-EMF induced inside an actuator during movement [ 6 , 7 , 8 ], thus delivering precise and unique estimates of the position when the actuator is moving at middle or high speed.…”

Real-time Sensorless Estimation of Position and Force for Solenoid Actuators

“…The first estimation method uses a pulse width modulation (PWM) voltage input (11) (12) . The inductance of the solenoid is calculated based on the voltage and current responses.…”