The Design and Fabrication of an On-Rotor Sensing Wireless Vibration Node for Motor Condition Monitoring

With the advancement of electronics and micromanufacturing technology, the micro-electromechanical system (MEMS) sensor is being manufactured with higher performance, providing excellent potential for developing cost-effective condition monitoring systems. Traditional accelerometer sensing methods are affected by strong background noise, limiting the performance of monitoring various electric motors. Hence, a new on-rotor sensing (ORS) method is presented in this article to measure acceleration directly on the rotating rotor of motors. The ORS system consists mainly of an embedded MEMS accelerometer to directly sense vibration on rotors and a Bluetooth low energy (BLE) 5.0 module to implement over-the-air vibration data transmission. Specifically, the ORS sensor node can be mounted directly on a motor shaft and rotates with the rotor shaft. By such a configuration, the accelerometer is close to the vibration source and the signal perceived has a high signal-to-noise ratio (SNR). As a result, it can be sensitive to small changes in rotor systems for early stage rotor fault detection and accurate fault severity diagnosis. To meet the general requirement for vibration-based condition monitoring of a wide range of motors, the wireless ORS sensor node is fabricated with a dynamic range from ±2 to ±16 g at a sampling rate of 16 kHz. The experimental results based on a widely used 4-kW ac motor show that the ORS node can achieve a higher SNR of over 45 dB compared to a traditional accelerometer, resulting in a high amplitude response at the fault frequency, allowing the progression of the faults to be monitored more accurately.