Development of a Sensorless Magnetic Levitation Control System

Abstract

A method of measuring the air gap of the magnetic levitation system from the pulse width modulation (PWM) carrier frequency component is presented. It is intended that an electromagnet be used as a gap sensor and a levitation control actuator. The inductance of the magnet is a function of the air gap which can be estimated from the PWM carrier component of the driving voltage and current. The estimated air gap is used to control the duty ratio of the PWM driving voltage. The proposed method is applied to a simple experimental apparatus and its capability is tested.