A Sensorless Method for Detecting Spool Position in Solenoid Actuators

Abstract

Abstract — A method is developed to estimate the position of the moving part in a solenoid actuator. We superpose a sinusoidal component onto the base duty ratio of the drive PWM (Pulse Width Modulation), thus, a scan signal is generated which is used to first identify, then to “measure ” the system during actuation. A model of the actuator device is derived from experimental analyses and the effects of e.g. scan signal frequency and supply voltage are studied. External force disturbances, which may be present in flow control applications, are also considered and an algorithm is provided for its compensation in position estimation, thus, force estimation is realized as well. The hardware requirements are low which makes the presented method suitable for cost effective embedded applications. Experimental results are also provided.