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

The rotating speed of the downhole motor is very important to the drilling process, so it is necessary to be measured in real-time. Here, a self-powered downhole motor rotating speed sensor, which designed as a double friction belts and a compressed friction contact structure, is proposed based on triboelectric nanogenerator. The double friction belts or any single friction belt of the sensor can be used as a self-powered rotating sensor alone, which shows a high reliability, and the compressed friction contact method increases the contact pressure of the two friction layers, thereby increasing the output signal amplitude. Test results show that the maximum output voltage and output current of the sensor with double friction belts working are respectively 15.8 V and 42.28 nA, and the maximum output power is 194.83 × 10 ^-9 W when a 10 ⁹ ohm resistance is connected in series, while the parameters of the sensor with single friction belt working are respectively 15.6 V and 24.17 nA, and the maximum output power is 52.22 × 10 ^-9 W when a 10 ⁹ ohm resistance is connected in series. Further tests show that whether the sensor working with double belts or single belt, the measurement range is 0 to 910 r/min, the measurement error is less than 4%, and the working temperature range is 0 to 240 degrees Celsius, which shows that the sensor can meet the actual needs for the rotating speed measurement of downhole motor.