Modeling of an Absolute Displacement Sensor Using a Current-Feedback-Type Driver

Abstract

An absolute displacement sensor has been proposed for precise vibration control of semiconductor manufacturing equipments. Based on state feedback, a control model of the sensor is designed in order to obtain feedback gains as optimal regulator. However, frequency characteristics in simulations are different from those in experiments due to back electromotive force from a forcer coil. In this paper, a voltage-feedback-type driver of the sensor is replaced by a current-feedback-type driver in electric circuits. This is because the latter driver can ignore effects of the back electromotive force. Firstly, we express principles of the effects in equations. Next, the control model is modified, and simulation parameters are identified. As a result, the simulations are corresponding to the experiments.