Measuring Micrometer-Level Vibrations With mmWave Radar

Abstract

Vibration measurement is a crucial task in industrial systems, where vibration characteristics reflect health conditions and indicate anomalies of the devices. Previous approaches either work in an intrusive manner or fail to capture the micrometer-level vibrations. In this work, we propose mmVib, a practical approach to measure micrometer-level vibrations with mmWave radar. First, we derive a metric called <i>Vibration Signal-to-Noise Ratio</i> (VSNR) that highlights the directions of reducing measurement errors of tiny vibrations. Then, we introduce the design of mmVib based on the concept of <i>Multi-Signal Consolidation</i> (MSC) for the error reduction and multi-object measurement. We implement a prototype of mmVib, and the experiments show that it achieves <inline-formula><tex-math notation="LaTeX">$3.946\%$</tex-math></inline-formula> relative amplitude error and <inline-formula><tex-math notation="LaTeX">$0.02487\%$</tex-math></inline-formula> relative frequency error in median. Typically, the average amplitude error is only <inline-formula><tex-math notation="LaTeX">$3.174um$</tex-math></inline-formula> when measuring the <inline-formula><tex-math notation="LaTeX">$100um$</tex-math></inline-formula> -amplitude vibration at around 5 meters. Compared to two existing mmWave-based approaches, mmVib reduces the 80th-percentile amplitude error by <inline-formula><tex-math notation="LaTeX">$69.21\%$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$97.99\%$</tex-math></inline-formula> respectively.