Research On Mechanical Vibration Period Inspection Based On Backscatter Signals

Making senses of vibration is an important task in many areas.Separated sensing and communication modules are always necessary for traditional vibration inspection systems.The high cost of these systems prohibits the widespread use of the inspection.Meanwhile,in some certain environment,the systems are occluded or suffer from the narrow field of view(e.g.,laser).These influences have a crippling effect on many vibration inspection.This paper proposes an innovative way to make sense of the world,which is based on backscatter signals instead of sensors.In this work,we present an RFID-based solution for the inspection of mechanical vibration.This solution exploits COTS RFID tags and readers.As typical backscatter nodes,RFID tags are low-cost,battery-free,and work in non-line-of-sight scenarios,allowing them to address the limitations of traditional solutions.Readings of tags provide random and low-frequency features which make the inspection of micro and high-frequency vibration more challenging.To the best of our knowledge,high period accuracy has long been a major problem for the mechanical vibration measurement,let alone with sub-millisecond level.We developed a prototype Tagbeat to make sense of vibration based on the findings that vibration displaces the tag attached on the vibrating surface within a small range,resulting its backscatter signals change in a regular pattern.This paper introduces three main innovations.First,for micro and weak signals whose amplitudes are samller than a threshold,a new digital amplification method is designed.Second,for high-frequency vibration,it introduces compressive sensing to recover the aliasing signals which are sampled with a relatively low RFID read frequency.Third,when feed with a few periods of short and noisy samples,it accurately measures mechanical vibration and search its period using COTS RFID system.We exploited COTS RFID devices to implement the prototype Tagbeat.Also we evaluated it with a commercial centrifugal machine.Based on the results from empirical benchmark Tagbeat is able to inspect the vibration period with a mean accuracy of 0.36 ms and 0.03% relative error rate.Furthermore three practical cases are studied to associate our measurement solution with the requirements of daily life.