Displacement measurement of four -axis electrostatical suspension system with insulated electrodes

In order to improve the reliability of electrostatic bearing system, the insulation processes are made for the voltage-controlled four-axis non-orthogonal electrostatic bearing system. However the insulation of the electrodes could affect the displacement measurement of the bearing system. To solve this problem, the principle of four axis displacement measurement is analyzed, and a method used to ensure the rotor ground potential is given. The influences of electrodes insulation on gap capacitances and displacement measurement are studied. An enhancement factor is introduced to quantify this influence, and the module of displacement measurement is remodeled. Experiments show that the measurement accuracy is superior to 0.2 μm, and the measurement of rotor displacement can be realized under the condition that the electrodes are insulated.