Measurement Of Radial Vibration Of Motor Shaft Based On Optical Fiber Sensing

With the improvement of the level of industrialization,motors have become the most important power equipment in people’s production and life,and are widely used in various fields of national economic production.During the long-term operation of the motor,some faults will inevitably occur.If the motor fault cannot be dealt with quickly and effectively,it is easy to cause major accidents.The research shows that the radial vibration signal of the motor shaft contains a lot of information about the running state of the motor.The research purpose of this paper is to explore a new method for the detection of radial vibration of the motor shaft,in order to solve the problems of the current traditional optical interferometry method,which is seriously disturbed by speckle,has low precision,is not easy to align,and is large and difficult to install.In order to optimize the measurement structure,improve the measurement accuracy,and can be used for the radial vibration measurement of ultra-micro motors.Optical fiber vibration sensor has the characteristics of strong anti-electromagnetic interference,high sensitivity,high precision,easy to bend and so on.Therefore,in this paper,the optical fiber vibration sensor is used to measure the radial vibration of the motor shaft,so as to effectively judge the running state of the motor,and realize the early warning and diagnosis of motor faults,which is of great significance to avoid major accidents and reduce maintenance costs.Firstly,the mechanism of fiber Fabry-Perot Interference(FPI)effect and the phase demodulation algorithm based on Multiple Hilbert Transform(MHT)are studied.According to the traditional FPI principle,the fiber FPI effect model is constructed,the output light intensity and phase equation expressions of the fiber FPI effect are derived,and the phase demodulation of the fiber FPI sensor vibration signal based on the MHT algorithm is proposed.On the basis of the fiber FPI theoretical model,a fiber FPI effect model based on microsphere metalens is constructed,and the phase demodulation algorithm based on MHT is used to demodulate the phase of the vibration measurement signal of the fiber FPI sensor based on microsphere metalens.It lays a theoretical foundation for the further development of the optical fiber FPI sensor to measure the radial vibration of the micro-precision motor shaft and the optical fiber FPI sensor based on the microsphere superlens to measure the radial vibration of the ultra-micro precision motor.Secondly,in view of the large spot size of the traditional optical measurement method,the signal is seriously disturbed by the speckle,and the measurement accuracy is low,an optical fiber-based FPI sensing measurement method is proposed.The method uses a single-mode fiber and a coupler to form a measurement system,and the single-mode fiber is used as a sensing probe,and its end face and the radial position of the rotation axis to be measured form a FabryPerot cavity(F-P cavity).When light passes through the single-mode fiber,the reflected light from the end face of the single-mode fiber interferes with the reflected light at the radial centerline of the rotating shaft.The optical interference technology is used to convert the phase change of the light wave caused by the radial vibration of the motor into the light intensity change.The phase change information is obtained through the MHT phase demodulation algorithm,so as to realize the measurement of the radial vibration of the motor shaft.The experimental results show that the method can effectively measure the radial vibration of the micro-precision motor shaft,and can realize the fault diagnosis of the motor.Finally,in view of the small diameter of the ultra-micro motor shaft,the diameter of which is one millimeter or even sub-millimeter,the traditional measurement method is large in size,difficult to install,and the spot size is large,which is difficult to collimate,a fiber-optic FPI sensor based on microsphere superlens is proposed.The miniature sensor consists of an optical fiber and a microsphere metalens with a diameter of 5 microns.The microsphere superlens and the optical fiber form a sensing probe,and the air end face of the microsphere superlens and the radial position of the rotating shaft of the ultra-micro motor under test form an F-P cavity.The microsphere superlens has good focusing performance.When the outgoing light from the optical fiber illuminates the microsphere superlens,the microsphere superlens can generate a beam waist with a sub-micron level of light spot,and the light spot is focused on the radial position of the rotating shaft.The spherical super lens can also focus the scattered light or reflected light from the radial position of the rotating shaft,so that the scattered light or reflected light carrying the radial vibration information returns to the optical fiber and interferes with the reflected light from the end face of the optical fiber.The optical interference technology is used to convert the phase change of the light wave caused by the radial vibration of the ultra-micro motor into the change of light intensity,and the phase change information is obtained through the MHT to realize the measurement of the radial vibration of the ultra-micro motor.The experimental results show that the method can effectively measure the radial vibration of ultramicro motors,and can realize the fault diagnosis of ultra-micro motors,which overcomes the problems of traditional non-optical measurement methods such as large size,complex structure and difficult installation;it also overcomes the problems of large spot size and difficult collimation of traditional optical measurement methods.