Development of capacitive sensors for measuring vibrations and small displacements of a high-speed rotating machines for use in active vibration control systems

This work focuses on the development of custom capacitive sensors for measuring vibration and small displacements of high-speed rotating machines. The main criteria for this development are to use cheap and available resources and to optimize these resources to achieve the best possible performance. The aim was to design a solution that could be implemented within an Active Vibration Control (AVC) system, where the focus is mainly on high measurement frequency. The paper also includes a theoretical description of the measurement methodology with capacitive sensors and the use of the FDC2214 capacitive-digital converter (CDC), which works on the principle of a resonant LC circuit. The last part of the paper is devoted to the comparison of different designs of sensitive parts and also the concepts themselves. In addition to the calibration, the static characteristics are also described, and a measurement range error analysis is performed. The result of this work is a solution with a maximum measurement frequency of 3.8 MHz, maximum relative error of about 0.7% and sensor resolution from about 700 nm to 14 µm. The work also includes the deployment of the resulting smart sensors on the high-speed rotating machine to prove the capability to use them in the already mentioned AVC system. [Display omitted] •Explanation of the principles of capacitive sensing.•Development of an efficient and low-cost solution for measuring small displacements in the range of 0–1000 micrometers.•Comparison of several developed sensor designs.•The maximum relative error of the sensor is approximately 0.7% over the measuring range.•Maximum measurement frequency reached up to 3.8 MHz.