Error Analysis of the Cylindrical Capacitive Sensor for Active Magnetic Bearing Spindles

Abstract

This paper discusses the effects of mechanical errors of the cylindrical capcitive sensor (CCS) for active magnetic bearing (AMB) spindles, including the roundness error of a rotor and the mounting error of a sensor. The CCS has earned much interest as an AMB sensor due to its advantages of high resolution and spatial-averaging effect. An analytical model of the CCS is given and its spatial-averaging effect is shown quantitatively. The analytical model of the measuring process with the variation of sensor geometry shows that the CCS is more robust to roundness errors than the generally used probe sensor. This is verified through simulations and experiments on measuring orbits of rotors with harmonic roundness errors. In addition, the effects of mounting errors of the sensor are modeled and investigated. [S0022-0434(00)02601-0]