CN108180977B - Device for simultaneously measuring vibration condition and friction coefficient based on fiber bragg grating - Google Patents
Device for simultaneously measuring vibration condition and friction coefficient based on fiber bragg grating Download PDFInfo
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- CN108180977B CN108180977B CN201711404128.4A CN201711404128A CN108180977B CN 108180977 B CN108180977 B CN 108180977B CN 201711404128 A CN201711404128 A CN 201711404128A CN 108180977 B CN108180977 B CN 108180977B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N19/00—Investigating materials by mechanical methods
- G01N19/02—Measuring coefficient of friction between materials
Abstract
The invention provides a device for simultaneously measuring the vibration condition and the friction coefficient in friction self-excited vibration based on a fiber grating sensing technology, which comprises a vibration excitation mechanism, a vibration sensor, a force measuring sensor and a demodulator, wherein the vibration excitation mechanism is used for exciting the vibration of a fiber grating; the vibration exciting mechanism comprises a disc and a rotary driving mechanism thereof, and a vibrator mechanism which does simple harmonic vibration along with the rotation of the disc is arranged on the disc; the vibration sensor comprises a base, an elastic steel sheet and a mass block, wherein the base is fixed on the sliding block, one end of the elastic steel sheet is fixed on the base, the other end of the elastic steel sheet is fixed with the mass block, and two sides of the elastic steel sheet are respectively fixed with a fiber bragg grating; the force measuring sensor comprises an elastic movable edge, one end of the elastic movable edge is fixed, the other end of the elastic movable edge is connected with the other end of the spring, and two fiber gratings are fixed on two sides of the elastic movable edge respectively; the demodulator is connected with the tail fibers of all the fiber bragg gratings, the fiber bragg gratings are connected into different channels, and the fiber bragg grating signals are demodulated.
Description
Technical Field
The invention relates to the field of fiber grating sensing, in particular to a novel method for simultaneously measuring a friction coefficient and a vibration condition in friction self-excitation vibration based on a fiber grating sensing technology.
Background
The fiber grating is a diffraction grating formed by axially and periodically modulating the refractive index of a fiber core of an optical fiber through a certain method, and is a passive filter device. The fiber grating is formed by writing incident light into a fiber core in a coherent field pattern by using the photosensitivity of a fiber material through an ultraviolet light exposure method, so that the refractive index of the fiber core generates periodic change and generates periodic modulation, and a permanent spatial phase grating is formed in the fiber core of a single-mode fiber. Fiber gratings have been widely used in the field of fiber sensing since the advent. The fiber grating sensor has the advantages of corrosion resistance, electrical insulation, high sensitivity and the like, so the fiber grating sensor is more and more concerned. The resonant wavelength of the fiber grating is sensitive to stress strain and temperature change, so the fiber grating is mainly used for measuring the temperature and the stress strain.
The fiber grating sensor obtains sensing information by modulating the central wavelength of the Bragg fiber grating by external parameters (temperature or stress strain), so that the fiber grating sensor has the advantages of high sensitivity, strong anti-interference capability and low requirements on light source energy and stability, and is suitable for precise and accurate measurement. Fiber grating sensors have been used in various applications, such as monitoring of highways, bridges, dams, mines, airports, ships, railways. The physical quantity directly measured by the fiber grating is temperature and strain, the fiber grating sensor changes the grating pitch of the grating by the displacement or strain caused by the measured system through the wavelength modulation principle, and further changes the wavelength, so that in the experiment, the vibration information or the friction characteristic of the system can be reflected by detecting the change by using the strain principle of the fiber grating.
The cross sensitivity effect of the fiber grating to the existence of temperature and strain is the inherent characteristic of the sensing measurement, and the cross sensitivity effect exists when the temperature and the stress change simultaneously. Many experiments in the prior art cannot well solve the cross sensitivity problem. And a single fiber grating or a single fiber grating sensor can only measure one physical quantity, and based on the fact that the test bed needs to measure two parameters of vibration and friction coefficient at the same time, the previous measuring method measures the physical quantity only singly under the same experimental condition and cannot achieve the purpose of simultaneous measurement.
Disclosure of Invention
The invention aims to solve the technical problems that in the prior art, strain and temperature are cross-sensitive and the vibration condition and the friction coefficient cannot be measured simultaneously, and provides a novel method for simultaneously measuring the friction coefficient and the vibration condition in friction self-excitation based on the fiber grating sensing technology, wherein the method can distinguish the respective changes of the temperature and the stress when the temperature and the stress change simultaneously.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a device for simultaneously measuring vibration condition and friction coefficient in friction self-excited vibration based on fiber grating sensing technology, which comprises a vibration excitation mechanism, a vibration sensor, a force sensor and a demodulator, wherein the vibration excitation mechanism is used for exciting vibration of a fiber grating;
the vibration excitation mechanism comprises a disc and a rotary driving mechanism thereof, a vibrator mechanism which does simple harmonic vibration along with the rotation of the disc is arranged on the disc, the vibrator mechanism comprises a sliding block, a spring and a guide mechanism, one end of the spring is fixed on the sliding block, the other end of the spring is fixed on an elastic movable edge of the force cell, and the spring and the sliding block are arranged on the guide mechanism in a penetrating way;
the vibration sensor comprises a base, an elastic steel sheet and a mass block, wherein the base is fixed on a sliding block, one end of the elastic steel sheet is fixed on the base, the other end of the elastic steel sheet is fixed with the mass block, two fiber gratings are respectively fixed on two sides of the elastic steel sheet, and the two fiber gratings are symmetrically arranged along the vertical central line direction;
the force measuring sensor comprises an elastic movable edge, one end of the elastic movable edge is fixed, the other end of the elastic movable edge is connected with the other end of the spring, two fiber gratings are fixed on two sides of the elastic movable edge respectively, and the two fiber gratings are symmetrically arranged along the direction of a vertical center line;
the demodulator is connected with the tail fibers of all the fiber bragg gratings, the fiber bragg gratings are connected into different channels, and the fiber bragg grating signals are demodulated.
According to the technical scheme, the elastic movable edge is a spring steel sheet.
In connection with the above technical solution, the force cell sensor further comprises a connecting block, one end of which is fixed with one end of the elastic movable edge, and the elastic movable edge forms an L-shaped structure.
According to the technical scheme, the fiber grating is packaged by epoxy resin AB sealant.
The invention also provides a method for simultaneously measuring the vibration condition and the friction coefficient in the friction self-excited vibration based on the fiber grating sensing technology, which is based on the device and specifically comprises the following steps:
sequentially connecting two fiber bragg grating tail fibers on the elastic steel sheet into a channel 1 and a channel 2 of the demodulator;
sequentially connecting two fiber bragg grating tail fibers of the force transducer into a channel 3 and a channel 4 of the demodulator;
a constant rotating speed is set for the disc through the rotary driving mechanism, so that the disc rotates, and the sliding block generates friction self-excited vibration on the disc;
in the process of reciprocating vibration, the slider transmits the vibration condition to the vibration sensor, simultaneously transmits the elastic force of the spring which is stretched back and forth to the force measuring sensor, the elastic steel sheet and the elastic movable edge generate strain immediately, and the strain signal is simultaneously transmitted to the fiber bragg grating to extend or contract so as to cause the wavelength change;
acquiring signals through a demodulator, simultaneously obtaining the vibration condition and the elasticity according to the wavelength variation of the demodulated fiber bragg grating, and calculating the friction coefficient by utilizing a formula through vibration and spring force, namely completing simultaneous measurement of the vibration and the friction coefficient;
the demodulator collects fiber grating signals in a period of time in the friction self-excited vibration process, analyzes the variation of the fiber grating wavelength along with the time according to the stored data, obtains the vibration condition and the elasticity according to the demodulated variation of the fiber grating wavelength, and calculates the friction coefficient through the vibration and the elasticity.
The technical scheme also comprises the following steps:
the rotation speed with a certain gradient is set by the rotation driving mechanism, the rotation speed is gradually increased from small to large, fiber grating signals on the vibration sensor and the force transducer at different rotation speeds are collected by the demodulator, and the simultaneous measurement of the vibration condition and the friction coefficient of the friction self-excited vibration at different rotation speeds is completed.
The invention has the following beneficial effects: the invention provides a novel method for simultaneously measuring the vibration condition and the friction coefficient in the friction self-excitation based on the fiber bragg grating sensing technology, and Fiber Bragg Gratings (FBGs) are symmetrically adhered to two surfaces of an elastic steel sheet and an elastic movable edge, so that the strain delta at two ends is zero in an integral period in the experimental process, and the problem of cross sensitivity is solved. And under the same experimental condition, the two sensor elements simultaneously generate strain and transmit the strain to the fiber grating, and the conditions of vibration and friction coefficient can be simultaneously measured based on the fiber grating sensing technology, so that the problem of single physical quantity measurement is solved. The measuring method can be applied to machines with changed strain, particularly to the occasions with transient change of strain, and can realize simultaneous measurement of the vibration condition and the friction coefficient, for example, the vibration condition and the friction coefficient of a vibrating object at any moment in the friction self-excited vibration process can be measured simultaneously.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a drawing of an overall apparatus of a friction self-excited vibration experiment table according to an embodiment of the present invention
FIG. 2 is a diagram showing the relative positions of various components on a disk in accordance with an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a vibration sensor according to an embodiment of the present invention;
FIG. 4 is a schematic view of a load cell according to an embodiment of the present invention; ,
FIG. 5 is a diagram of an elastic force calibration experiment apparatus according to an embodiment of the present invention;
FIG. 6 is a graph of spring force versus strain calibration (spring original length 16.5cm) for an embodiment of the present invention.
In the figure, the device comprises a base plate 1, an adjusting foot 2, a bottom plate 3, a support frame (comprising a base plate 4, a seat plate 5, a vertical plate 6, a rib plate 7, an upper transverse plate 8 and a lower transverse plate) 9, an aluminum section truss (comprising a rectangular frame 10, a vertical frame 11, a vertical frame 12, an upper transverse frame 13 and a lower transverse frame 14, a servo motor 15, a speed reducer 16, a plum blossom coupling 17, a step shaft 18, a tapered roller bearing 19, a disc 20, a sliding block 21, a spring 22, a smooth guide rod 23, a L-shaped part 24, a vibration sensor (comprising a base 25, a base 26, an elastic steel sheet 27 and a mass block 28, a force measuring sensor (comprising a 29, a connecting block 30 and an elastic movable edge), a number 1 optical fiber grating, a number 32 and a number 2 optical fiber grating, a number 33 and a number 3 optical grating, a number 34 and a number 4 optical grating 35, a bolt, a 36, a nut 37, a square gasket 38, a pressing sheet 39, a dynamometer, a height.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the novel apparatus for simultaneously measuring the vibration condition and the friction coefficient in the friction self-excitation based on the fiber grating sensing technology according to the embodiment of the present invention includes:
vibration excitation mechanism, the device mainly include subassembly such as disc, slider, spring, guiding mechanism, motor, speed reducer, bottom plate and section bar, select servo motor as driving motor for use, in order to further obtain stable rotational speed, select reduction ratio 20: the speed reducer of 1 is used together with a motor, a disc is driven to rotate by the motor, one end of a spring is fixed on a sliding block, and the other end of the spring is fixed on an elastic movable edge.
When the disc rotates at a constant speed, firstly, the sliding block is only acted by friction force on the disc and vibrates along the rotating direction, the sliding block is not only acted by the friction force but also by the elastic force of the spring after moving, the resultant force of the two generates acceleration, and the sliding block moves reversely when the speed is zero, so that simple harmonic vibration (friction self-excited vibration) is formed by one-time repeated movement;
the vibration sensor is a sensor based on fiber grating sensing technology and comprises a base, an elastic steel sheet and a mass block, wherein one end of the rectangular elastic steel sheet is fixed on the base, the other end of the rectangular elastic steel sheet is provided with the mass block, and the fiber grating is adhered near the fixed end of the elastic steel sheet. When the vibration of the sliding block is measured, the base is fixed on the sliding block, the base and the sliding block vibrate simultaneously, so that the vibration of the mass block on the elastic steel sheet is caused, the elastic steel sheet generates strain under the action of inertia force, the fiber bragg grating is driven to extend and contract, so that the change of the bragg wavelength of the fiber bragg grating is caused, and the vibration measurement is realized by detecting the change of optical power corresponding to the change of the bragg wavelength;
the force transducer is composed of a connecting block and an elastic movable edge to form an L-type structure, the connecting block is fixed on an upper cross frame of a section bar by bolts and nuts, the elastic movable edge is connected with one end of a spring, the other end of the spring is fixed on a sliding block, the spring vibrates back and forth along with the sliding block and the elastic movable edge along with the spring in the friction self-excitation vibration process, the elastic movable edge generates certain strain due to the spring force, so that the wavelength change of the fiber bragg gratings on the two sides of the elastic movable edge is caused, the fiber bragg grating tail fiber is connected into a demodulator, the size of the spring force is obtained by demodulating the signal of the fiber bragg grating, and the size of the friction force and the friction coefficient can be obtained by the spring.
The demodulation instrument is a fiber grating demodulation instrument, a vibration sensor and all fiber grating tail fibers on the elastic movable edge are connected to each channel of the demodulation instrument together, fiber gratings on the two sensors simultaneously generate strain in friction self-excitation vibration to cause wavelength change, signals of vibration and force can be simultaneously collected through the demodulation instrument, relevant data are stored through demodulation software, and then the vibration condition and the friction coefficient at any moment can be measured together according to the wavelength change quantity of each fiber grating.
The device comprises 4 fiber bragg gratings (namely 2 fiber bragg gratings pasted on an elastic steel sheet of the vibration sensor and 2 fiber bragg gratings pasted on an elastic movable edge), and the 4 fiber bragg gratings are sequentially and independently connected into four channels of the demodulator. The fiber gratings are adhered along the vertical central line direction of the sensor element, namely the vertical central line directions of the elastic movable edge and the elastic steel sheet are symmetrically arranged;
in the device, the fiber grating can be packaged by epoxy resin AB glue.
The invention relates to a novel method for simultaneously measuring friction coefficient and vibration condition in friction self-excitation based on fiber bragg grating and strain gauge sensing technology, which comprises the following steps based on the device:
respectively sticking a fiber grating on the front surface and the back surface of an elastic steel sheet on the vibration sensor, and sequentially marking;
respectively sticking a fiber grating on the front surface and the back surface of an elastic movable edge on the force transducer, and sequentially marking;
placing the vibration sensor above the sliding block, and adding pins to fix the base and the sliding block at pin holes;
selecting a spring with proper spring stiffness and a slider with proper mass;
one end of the spring is fixed on the sliding block by a pressing sheet and a screw, and the other end of the spring is fixed on the elastic movable edge;
a smooth guide rod is sequentially penetrated into a center hole of a sliding block and a round hole at the bottom end of an elastic movable edge, one side of the sliding block of the guide rod is fixed on an L-shaped part 23 by bolts and nuts, and the L-shaped part 23 is fixed on a cross frame on a section frame;
the four fiber grating tail fibers marked on the two sensors are sequentially and independently accessed into four channels of a demodulator, the demodulator is connected with a computer, the demodulator is started, demodulation software is started, and the central wavelength of the fiber grating at a static moment is measured and recorded;
a constant rotating speed is set for the disc through a driving motor, so that the disc rotates, and the sliding block generates friction self-excitation vibration on the disc;
the demodulator collects the fiber grating signals in a period of time in the friction self-excited vibration process, and analyzes the change of the fiber grating wavelength along with the time according to the stored data, so as to obtain the vibration condition and the friction coefficient.
In the method, a sliding block transmits the vibration condition to a vibration sensor in the process of reciprocating vibration, meanwhile, the elastic force of a spring which is stretched back and forth is transmitted to a force measuring sensor, an elastic steel sheet and an elastic movable edge generate strain immediately, the strain signal is transmitted to a fiber grating at the same time to enable the fiber grating to extend or contract so as to cause wavelength change, a demodulator is used for acquiring signals, the vibration condition and the elastic force are obtained at the same time according to the wavelength change quantity of the demodulated fiber grating, and the friction coefficient is calculated by vibration and spring force according to a formula, namely, the simultaneous measurement of the vibration and the friction coefficient is completed;
in the method of the present invention, to obtain a constant disc speed, the motor speed is set according to the reduction ratio of the reducer 20: 1.
In the method, different rotating speeds of a motor are controlled, the rotating speed is gradually increased from small to large, and fiber grating signals under different rotating speeds of a disc are collected;
in the method, during the movement process of the sliding block, the acceleration is measured by the vibration sensor, the spring force is measured by the force measuring sensor, and the friction force and the friction coefficient are calculated by utilizing a mechanical formula, so that the friction coefficient is synchronously measured, the whole process is real-time measurement, the vibration condition and the friction coefficient at any moment in the measuring process can be simultaneously obtained, and the consistency of the simple harmonic movement phase is reflected.
In the embodiment of the invention, as shown in figure 1, the disc type friction self-excitation vibration experiment table mainly comprises a base part, a supporting part, a driving part and an excitation part, wherein the base part comprises a bottom plate and adjusting legs, the supporting part comprises a supporting frame, an aluminum profile truss and a step shaft, the driving part comprises a servo driver, a servo motor and a speed reducer, the excitation part comprises a disc, a 20 slider, an elastic element and a guide rod device, the eight adjusting legs are arranged at the periphery of the bottom surface of the bottom plate, the height of each adjusting leg is adjusted to keep the adjusting leg in a horizontal state, the supporting frame comprises a seat plate, a vertical plate, a ribbed plate, an upper transverse plate and a lower transverse plate, the seat plate, the vertical plate, the ribbed plate and the upper transverse plate are connected through welding, the lower transverse plate is fixed on the vertical plate through bolts, the supporting frame is arranged at the center of the top surface of the bottom plate, the aluminum profile truss is formed by assembling eight aluminum profiles through T-shaped bolts, flange nuts and outer corner pieces, the rectangular frame is composed of rectangular frame, the upper transverse frame, the rectangular frame, the upper transverse frame, the lower transverse frame is fixed on the bottom surface of the circular steel profile truss, the bottom surface of the circular disc, the circular cone bearing, the circular cone transverse plate, the bottom surface of the circular cone transverse plate, the transverse plate.
Principle of experiment
The measuring method is based on a friction self-excited vibration experiment table, the whole device of the experiment table is shown in figure 1, a sliding block is subjected to the combined action of constant friction force and alternating elastic force through the rotation of a disc and the traction of a spring, and friction self-excited vibration is generated under the guiding action of a smooth guide rod.
According to the FBG strain sensing model, the vibration measurement system can measure dynamic strain generated by various periodic motions (such as simple harmonic vibration), and the strain is completed by transmitting the motion to the elastic steel sheet through the vibration sliding block. The parameters of the vibration system include speed, acceleration, frequency, amplitude, etc., which can be converted into each other, and if the acceleration and the vibration frequency are known, the remaining parameters can be expressed, so the acceleration is commonly used to describe the vibration. According to the principle, a vibration sensor can be manufactured for the experiment table. After the measurement system converts the external acceleration into dynamic strain, the reflection wavelength of the FBG changes periodically, and then the change of the acceleration is reflected. The structure of the vibration sensor is shown in fig. 3, the grating is attached to the front surface and the back surface of the elastic steel sheet, namely two positions with completely opposite strain, the temperature change gradient in the test bed is not obvious, and the two surfaces of the sensor can be considered to be in the same temperature environment, so that the grating is subjected to the same temperature influence, and the contribution to the wavelength change is basically the same. When the vibration condition parameters are solved, the wavelengths of the two are subtracted, so that the central wavelength drift caused by temperature change can be eliminated, and the problem of cross sensitivity of the strain and the temperature is solved. When the sliding block vibrates, the base is fixed on the sliding block, the base and the sliding block vibrate simultaneously, so that vibration of a mass block on the sensor is caused, the elastic steel sheet generates strain under the action of inertia force, the fiber bragg grating is driven to extend and contract, so that the change of the bragg wavelength of the fiber bragg grating is caused, and the vibration measurement is realized by detecting the change of optical power corresponding to the change of the bragg wavelength.
The load cell also adopts a double grating method, the structure of which is shown in figure 4, 2 fiber gratings are symmetrically arranged on the front and back sides of the elastic movable edge to eliminate the influence caused by the temperature, when the temperature rises, the temperature of the load cell rises simultaneously, and when the element is stressed, the gratings are distributed on the front and back sides of the elastic movable edge, so that 1 grating is stressed, the central wavelength is increased, 1 grating is stressed, and the central wavelength is reduced. Because the 2 adhered fiber gratings are at the same temperature, the two fiber gratings are influenced by the same temperature, the wavelength change value of the fiber grating under pressure is subtracted from the wavelength change value of the fiber grating under tension, the obtained wavelength change value is the wavelength change value eliminating the wavelength influence caused by the temperature, so that the strain value of the current measured object is obtained, and the spring force value corresponding to the spring system is calculated according to the strain-elasticity coefficient obtained by calibration.
Because the fiber grating demodulator has 4 channels, the self-made vibration sensor and the force measuring sensor based on the fiber grating sensing technology have 2 fiber gratings respectively, all the fiber gratings can be just accessed into the demodulator channel at the same time, 1 fiber grating occupies one channel, and the positions and labels of the fiber gratings in the experiment are shown in fig. 2. When the disk rotates, the slide block starts to generate friction self-excited vibration, the motion condition of the slide block is simultaneously transmitted to the vibration sensor and the force measuring sensor, the elastic steel sheet on the vibration sensor is vibrated to generate strain, and simultaneously the elastic movable edge on the force measuring sensor is also subjected to strain by elasticity, thereby simultaneously causing the two pairs of fiber gratings on the elastic steel sheet and the elastic movable edge to extend or contract to cause the respective wavelengths to change, acquiring the wavelength data of the fiber gratings within a period of time through a demodulator and demodulation software, that is, the vibration signal and the elastic signal are recorded at the same time, the vibration condition and the elastic force are obtained by analyzing the wavelength change of the fiber bragg grating and multiplying the vibration calibration coefficient and the elastic calibration coefficient respectively, the friction force of the sliding block can be obtained by the vibration acceleration and the elastic force by using a related formula, and the friction coefficient is obtained by dividing the friction force by the positive pressure of the sliding block. Because all the fiber gratings are connected into different channels of the same demodulator, the acquired vibration signals and the elastic signals are synchronous, namely phase consistency, and two parameters of vibration conditions and friction coefficients can be simultaneously obtained by analyzing the motion state at any moment in simple harmonic motion, so that the vibration conditions and the friction coefficients can be simultaneously measured in the friction self-excitation vibration process by the methods of signal acquisition, analysis and calculation.
Specific experimental scheme
In this experiment, two parameters, vibration condition and friction coefficient, respectively, need to be measured. Before the test bed measurement experiment, the fiber bragg grating on the vibration sensor needs to be subjected to acceleration calibration, the fiber bragg grating and the strain gauge on the force transducer need to be subjected to tension calibration, and then the simultaneous measurement experiment of the vibration condition and the friction coefficient is carried out.
Simultaneous measurement of vibration conditions and coefficient of friction
The fiber bragg gratings are respectively attached to the vibration sensor and the force sensor, and after the fiber bragg gratings are sequentially connected to the demodulator, fiber bragg grating signals on the elastic steel sheet and the elastic movable edge in the friction self-excitation vibration process can be simultaneously acquired, and vibration conditions and elastic force changes can be simultaneously obtained through respectively analyzing data stored by demodulation software. The specific experimental steps are as follows:
1) the method comprises the following steps of firstly connecting all parts in an experimental device according to the method shown in figure 2, fixing two ends of a spring on a sliding block and an elastic movable edge respectively by using a screw, a nut and a pressing sheet, fixing the elastic movable edge and a connecting block, fixing the connecting block on an upper cross frame of an aluminum profile, sequentially penetrating a smooth guide rod through a central hole of the sliding block and a round hole at the bottom end of the elastic movable edge, fixing the other side of the sliding block on L-shaped parts 23, fixing the upper end of L-shaped parts 23 on the upper cross frame, and connecting the fixing structures in a bolt and nut mode.
2) The fiber bragg grating tail fibers No. 1 and No. 2 on the elastic steel sheet of the vibration sensor are sequentially connected into channels No. 1 and No. 2 of a demodulator, the fiber bragg grating tail fibers No. 3 and No. 4 on the elastic movable edge of the force-measuring sensor are connected into channels No. 3 and No. 4 of the demodulator, the demodulator is connected with a computer through a network cable, the power supply of the demodulator is connected, fiber bragg grating demodulation software on the computer is started, connection is clicked under a menu, the demodulator is connected with the computer for signal transmission, the central wavelength corresponding to one fiber bragg grating in the 4 channels can be observed after the connection is successful, and the sampling frequency is set to be 4000 Hz.
3) Because the motor of this test bench cooperates the speed reducer to use, the reduction ratio is 20:1, controls the disc rotational speed through servo driver, sets for the rotational speed: the disc speed was 20: 1. In the experiment, the slide block is reset to the original length position of the spring before the disc rotates, the static wavelength at the moment is measured, and the 10s data is also stored. Then setting the rotating speed of the disc to be 10r/min, saving the data for 10s after the sliding block starts to generate friction self-excited vibration on the disc, and saving the data files measured in the static state and the vibration state in the computer in different naming modes.
4) And (3) repeating the step 3) to carry out three times of measurement, firstly, mediating down the test bed before carrying out the next measurement, then, resetting the sliding block, measuring the corresponding static wavelength, similarly storing 10s of data, and then, resetting the rotating speed to carry out the next experiment.
5) And increasing the rotating speed of the disc for measurement, setting the rotating speeds of the disc to be 10, 20, 30, 40, 50 and 60r/min because the spring can generate friction self-excited vibration within 10-60r/min, repeating the steps 3) and 4), measuring the vibration condition and the friction coefficient in the friction self-excited vibration process at different rotating speeds, repeating the measurement for three times for each group of rotating speed, adjusting the test bed to stop before the next measurement, resetting the sliding block, measuring the wavelength corresponding to the static state, storing 10s of data, and resetting the rotating speed for the next experiment.
6) And replacing a spring with different spring stiffness to repeat the measurement, setting different rotating speeds, and measuring the wavelength of each fiber grating within 10-60 r/min.
7) The number of the sliders is increased to increase the mass, i.e. to increase the friction, and the above measurement steps are repeated, measuring three sets at each rotation speed.
8) The acquired data under each working condition are processed and analyzed by Matlab, the vibration condition can be obtained by the calibration coefficient of the vibration sensor and the wavelength change of the No. 1 and No. 2 fiber gratings, the spring elasticity can be obtained by the calibration coefficient of the force sensor and the wavelength change of the No. 3 and No. 4 fiber gratings, and the friction force and the friction coefficient can be obtained by calculation of a related formula, so that the simultaneous measurement of the vibration condition and the friction coefficient is completed.
The simultaneous measurement of the vibration condition and the friction coefficient in the friction self-excited vibration process can be completed through the experiment, two pairs of collected fiber grating signals of No. 1, No. 2, No. 3 and No. 4 are respectively processed by Matlab and a physical analysis method, then change condition curves of vibration and elasticity along with time change are drawn, the two fiber grating signals are in a sine curve, the change conditions are from the same time to the same time, the phases are consistent, and the vibration condition and the friction coefficient in the friction self-excited vibration process can be obtained simultaneously by analyzing data at any time.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (4)
1. A device for simultaneously measuring vibration condition and friction coefficient in friction self-excited vibration based on fiber grating sensing technology is characterized by comprising a vibration excitation mechanism, a vibration sensor, a force measuring sensor and a demodulator;
the vibration exciting mechanism comprises a disc and a rotary driving mechanism thereof, a vibrator mechanism which does simple harmonic vibration along with the rotation of the disc is arranged on the disc, the vibrator mechanism comprises a slide block, a spring and a guide mechanism, one end of the spring is fixed on the slide block, and the spring and the slide block are both arranged on the guide mechanism in a penetrating way;
the vibration sensor comprises a base, an elastic steel sheet and a mass block, wherein the base is fixed on a sliding block, one end of the elastic steel sheet is fixed on the base, the other end of the elastic steel sheet is fixed with the mass block, two fiber gratings are respectively fixed on two sides of the elastic steel sheet, and the two fiber gratings are symmetrically arranged along the vertical central line direction;
the force measuring sensor comprises an elastic movable edge, one end of the elastic movable edge is fixed, the other end of the elastic movable edge is connected with the other end of the spring, two fiber gratings are fixed on two sides of the elastic movable edge respectively, and the two fiber gratings are symmetrically arranged along the direction of a vertical center line;
the demodulator is connected with the tail fibers of all the fiber bragg gratings, the fiber bragg gratings are connected into different channels, and the fiber bragg grating signals are demodulated.
2. The device of claim 1, wherein the resiliently movable edge is a piece of spring steel.
3. The apparatus of claim 1, wherein the load cell further comprises a connecting block having one end secured to one end of the flexible edge to form an L-type configuration.
4. The apparatus of claim 1, wherein the fiber grating is encapsulated with an epoxy AB sealant.
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