Simultaneous Temperature Compensation and Synchronous Error Elimination for Axial Displacement Sensors Using an Auxiliary Probe

The output stability of the displacement sensors is an important issue for safe operations in magnetic bearing supported high-speed rotor system. This paper proposes an effective postprocessing solution to the problems of temperature drift and synchronous measuring error for the axial displacement sensor in a 10-kW magnetically suspended motor. The proposed configuration of the axial displacement sensor consists of three probes: one pair is used to eliminate the synchronous measuring error, and the third probe is employed for the consideration of temperature drift. First, the generating mechanism of the synchronous measuring error caused by the improper assemble is presented, and an operational amplifier is proposed to obtain an accurate position of the axial center by adjusting the weights of sensing signals from one pair of probes. Then the scheme of temperature compensation using an auxiliary probe is presented. In order to obtain accurately the characteristics of temperature drift at the operating point, the detailed procedure is given to determine the temperature-drift ratio. Finally, the terms related to temperature drift and synchronous error in the final output of the displacement sensor are both eliminated. Experimental results on a magnetically suspended motor test rig show the effectiveness of the proposed solution.