Error analysis of a new cylindrical capacitive sensor (CCS) for measuring five-dimensional motions of a rotor

Cylindrical capacitive sensor (CCS) refers to a class of displacement sensors that uses its whole circumference as sensing electrodes and conventional CCS’s usually measure the radial error motion of a rotor. In this paper, we propose a new smart sensor system that can measure the complete five-dimensional motions of a rotating shaft by combining two radial CCS’s and a specially designed target rotor. Due to the smaller number of sensors compared to the degrees of freedom to be measured, the sensor signals are susceptible to measurement errors such as the nonlinear errors and the cross talks. This paper presents a comprehensive error analysis of the proposed five-dimensional CCS. The result of error analysis is then used to come up with appropriate compensation methods for the nonlinearity and the cross talk of the proposed CCS. Simulation results are presented to verify the mathematical models for the measurement errors and also to validate the proposed compensation methods.

▶ A new CCS system is proposed using two regular CCS’s and a specially-shaped rotor. ▶ The error analysis is conducted for the proposed sensor system based on nonlinear model. ▶ Methods are developed to minimize undesirable signals coming from nonlinearities and cross talks. ▶ The new CCS system will be useful in rotating machines to monitor the rotor status in real-time.