A novel Cylindrical Capacitive Sensor (CCS) For Both Radial And Axial Motion Measurement

This paper proposes a novel cylindrical capacitive sensor (CCS) for both radial and axial motion measurement. The proposed CCS has almost the same geometric configuration as the conventional CCS and the unused axial area of the CCS is utilized to measure the axial motion of a rotor, which can reduce complexity of the hardware configuration and offer more degree of freedom in design. First, a theoretical model of the proposed CCS considering the nonlinear characteristic of the CCS is derived. Based on the derived theoretical model, a simple compensation method to decouple the radial and axial motion measurements is proposed. In addition, error analysis is performed and a design rule is proposed to guarantee the same accuracy in measuring both radial and axial motion. Finally, a test rig and electronics for the proposed CCS are built and the performances of the proposed CCS is verified experimentally.