The Influence of the Machining and Assembling Errors on the Performance of the Shaft Supported by Active Magnetic Bearings

Abstract

AMB (Active Magnetic Bearing) system consists of sensors, controllers, power amplifiers, and electromagnets. If all the elements are ideal, the position of the shaft could be controlled up to the sensor resolution. Because each element in real system has mechanical and electrical losses and nonlinearities, it is impossible to attain the desired performance. So far in order to obtain the desired performance of the AMB system, an additional controller or filter has been used in conventional control algorithm. Other factors that may affect the shaft behavior are the machining errors due to the machine work, and the assembling errors due to the accumulated machining errors or asymmetric screw down. The purposes of this paper are to model the machining and assembling errors in the 5-axis controlled AMBs, and to show the influence of the machining and assembling errors on the performance of the shaft supported by AMBs. In view of the results so far achieved, the roundness error of the radial sensor target and the perpendicularity error of the thrust rotor have considerable influence on the rotational precision of the shaft, however the machining errors of the radial rotor and assembling errors of the radial stators have little influence on the rotational precision of the shaft. But when the magnitude of the assembling errors increases over a certain limit, the bearing can not support the shaft properly.