Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Trade-Off Between Resolution and Response Time of Frequency-Modulated (FM) Eddy-Current Displacement Sensor for Active Magnetic Bearing (AMB)

Hyeong-Joon Ahn1,a and Ngoc Vu Vo2

1School of Mechanical Engineering, Soongsil University, 369 Sangdo-Ro, Dongjak-Gu, Seoul 06978, Korea

2Department of Mechanical Engineering, Graduate school, Soongsil University, 369 Sangdo-Ro, Dongjak-Gu, Seoul 06978, Korea


Active magnetic bearing (AMB) system is increasingly used in high-speed rotating machinery applications due to its high rotating speed, high efficiency, and energy savings over conventional bearings. Since AMB systems are open-loop unstable, they require displacement sensors to provide real-time position feedback of the suspended object and the displacement sensors' performance directly affects the AMBs' performance. Eddy-current displacement sensors are widely used for position feedback in the AMB system due to their simple structure, high sensitivity, and low cost. Although ordinary eddy current displacement sensors detect amplitude changes in oscillation circuits (AM sensors), a frequency modulation (FM) eddy-current sensor is occasionally used to improve the noise susceptibility. This paper presents trade-off between resolution and response time of frequency-modulated (FM) eddy current displacement sensor for active magnetic bearing (AMB). First, a one DOF AMB system with FM eddy-current displacement sensor is built. Then, a prescale combination based on an external counter chip and an internal prescale of a DSP (TMS320F28069M) is implemented to adjust the resolution and response time of the FM eddy-current displacement sensor. Finally, both static and dynamic performance are measured experimentally to evaluate the trade-off between resolution and response time of the system.

Keywords: Active magnetic bearing, Eddy-current sensor, Response time, Resolution

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