A Self-Powered Multifunctional Sensor for Downhole Motor Based on Triboelectric Nanogenerator

The rotational state of the downhole motor is critical for monitoring its operational condition. In this work, a self-powered multifunctional sensor (hereafter referred to as SPMS) is proposed to monitor the rotational speed, angle, and direction of rotation of downhole motor without external power supply. The experimental results show that the SPMS can measure the rotational speed in the range of 0–750 r/min with an error rate of less than 2% and an excellent linearity. In addition to the speed measurement function, it can also measure the rotation direction and angle with a resolution of 22.5°. Furthermore, the possibility of the SPMS converting downhole motor rotation energy into electrical energy and powering other downhole devices is also explored. The experimental results show that the SPMS has an open-circuit voltage of about 1.2 kV and a peak power of 1.128 mW at 150 r/min. It can light up 601 series light-emitting diodes (LEDs) and force a low-power temperature sensor. Compared with traditional downhole sensors, the SPMS can achieve multiparameter measurement without external power supply, which expands the application range of downhole sensors and is more suitable for downhole working conditions.