A Sensorless Method for Detecting Spool Position in Solenoid Actuators

In this paper, a method is developed to estimate the position of the moving part in a solenoid actuator. The authors superpose a sinusoidal component onto the base duty ratio of the drive Pulse Width Modulation. Thus, a scan signal is generated which is used to identify and 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.