Contactless Rotation Speed Measurement of Small-Scale Rotors Based on mm-Wave Radar

The accurate measurement of rotors' rotation speeds is critical for the stability and efficiency of precision manufacturing and industrial automation systems. Existing techniques, primarily based on electromagnetic or optical sensors, often have limitations, such as restricted operational range and reduced measurement accuracy in complex environments. Millimeter-wave radar (mmRadar) has been regarded as a promising sensing method for rotation speed measurement (RSM). However, when dealing with small-scale rotors, it may face specific issues such as multipath reflections during localization and autocorrelation distortion during RSM. In this article, we propose m-Tacho, a robust system that can simultaneously measure the rotation speeds of multiple small-scale rotors in a contactless manner over a relatively long distance. Specifically, to achieve precise localization, we design the multirotor localization (MRL) module to eliminate the static and multipath interference. Additionally, to accurately measure rotation speed, we design the RSM module to accurately extract rotation information from the distorted autocorrelation. We implement m-Tacho on a commercial mmRadar. Experimental results demonstrate that m-Tacho achieves an absolute percentage error (APE) of 0.235% in each rotor under varying conditions.