Research On LC Wireless Passive Flexible Strain Sensor Integrated With Ferrite Film

It is of great significance to test the strain parameters of bearings in high-speed rotating environment for monitoring the health status of bearings.Aiming at the problem that the traditional strain measurement method requires energy supply and wiring,this paper proposes LC wireless passive strain sensor is proposed to measure bearing strain.The sensor transmits energy and signal by electromagnetic coupling,and the test of strain parameters is realized by measuring the change of the resonant frequency of the sensor.Bearings in the mechanical industry are made of bearing alloys,aluminum-based alloys,copper alloys and other metal materials.Because the metal material has the effect of shielding electromagnetic waves,there is a problem of signal failure when using LC sensors on bearings.In this study,by analyzing the mechanism of ferrite absorbing and reflecting electromagnetic waves,the signal simulation of LC sensor integrated with ferrite material is completed in the metal environment,and a wireless passive strain sensor integrated with ferrite film is prepared,and the strain test is completed.The main research contents are as follows:(1)The LC sensor has the advantages of easy installation,high sensitivity and fast response.The LC strain sensor designed in this paper uses the interfinger capacitor structure as the strain sensing unit;A planar spiral inductor is used for the inductor used on the bearing.A metal equicantilever strain test platform was built,and a spiral micrometer was used to generate strain on the equi-strength cantilever.The standard resistance strain gauge was connected to the strain meter to complete the calibration test,and the resonant frequency of the sensor was measured by the network analyzer to obtain the corresponding strain parameter changes.The test results show that the wireless passive strain sensor can be used in the range of 0～1300 με,and the strain sensitivity can reach 61.54 Hz/με.(2)The reason of signal failure of LC sensor in metal environment is analyzed,and the signal of absorber material ferrite is simulated by electromagnetic simulation software HFSS.The capacitors and inductors were fabricated by electroplating process.In order to enhance its strain sensitivity,the β-phase PVDF was prepared in the interfinger part by electrospinning.And the ferrite material was integrated on the back of the LC sensor substrate through the screen printing process to complete the preparation of the sensor.(3)The electromagnetic signal was tested on the simulated bearing platform.Using Lab View to build a dynamic test system for network analysis data acquisition.The dynamic test of strain was completed on the rotating bearing with the speed of 0～1200 rpm.In this paper,the signal transmission principle,model optimization design,manufacturing test and integrated ferrite process of LC wireless passive sensor system are studied.The prepared sensor realizes the signal test in the metal environment,and has the advantages of no power supply,easy installation and high measurement accuracy.It has broad application prospects in the test of high-speed rotating bearings in the machinery industry.