Abstract
Machines with rotary parts are prevalent in industrial systems and our daily lives. Rotation speed measurement is a crucial task for monitoring machinery health. Previous approaches for rotation speed sensing are constrained by limited operation distance, strict requirement for illumination, or strong dependency on the target object’s light reflectivity. In this work, we propose mRotate, a practical mmWave radar-based rotation speed sensing system liberated from all the above constraints. Specifically, mRotate separates the target signal reflected by the rotating object from the mixed reflection signals, extracts the high-quality rotation related features, and accurately obtains the rotation speed through the customized radar sensing mode and algorithm design. We implement mRotate on a commercial mmWave radar and extensively evaluate it in both lab environments and in a machining workshop for field tests. mRotate achieves an MAPE of 0.24% in accuracy test, which is 38% lower than that produced by the baseline device, a popular commercial laser tachometer. Besides, our experiments show that mRotate can measure a spindle whose diameter is only 5mm, maintain a high accuracy with a sensing distance as far as 2.5m, and simultaneously measure the rotation speeds of multiple objects.