Design of a Centrifugal Force-Based Speed Sensor for Downhole Turbodrills

Turbodrill is an important type of drilling tool. Rotating speed is a key parameter to measure and control the efficiency of a turbodrill. Therefore, it is necessary to measure the rotating speed when a turbodrill is working under a well. However, current speed measurement devices and sensors cannot meet the requirements of the on-site downhole conditions due to many factors, including inadequate sealing, signal interference, difficult installation, and theoretical limitations. To break the aforementioned bottleneck, a new speed sensor used for turbodrills is designed based on the centrifugal force theory. In more detail, the measurement of the speed is performed based on a functional relation between the rotating speed and the centrifugal force of the turbodrill. Besides, the sensor was tested both in-lab and on-site. The test results illustrate that the measurement error is within ±4%, which meets the practical on-site conditions