Vibration sensor, condition and fault detection system based on triboelectric nanogenerator

Abstract

This invention relates to the field of vibration sensor technology, specifically to a vibration sensor and status and fault detection system based on a triboelectric nanogenerator. The sensor includes a base and a housing mounted on the base, as well as moving and fixed components. The fixed component includes a fixed magnet disposed on one side of the base, and a stainless steel pad, a first buffer layer, a first metal friction layer, and a polymer friction layer, sequentially connected from bottom to top on the base and located inside the housing. The moving component is located inside the housing and suspended above the fixed component, and includes a suspended magnet, a stainless steel washer, a second buffer layer, and a second metal friction layer, sequentially connected from top to bottom. This invention features an ultra-wide frequency response and high sensitivity, overcoming the shortcomings of existing self-powered sensors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vibration sensor, in particular to a vibration sensor based on friction nanogenerator, a state and fault detection system. BACKGROUND

[0002] The state of a machine is often represented by physical quantities such as vibration and temperature, and it has become an essential part of high-end intelligent equipment to determine the running state and fault type of the machine through vibration signals. With the rapid development of the Internet of Things, the number of sensors is large and widely distributed. However, traditional sensors have problems such as difficult maintenance, limited service life, and the need for additional energy supply, which makes it difficult to meet the needs of sensor networks required by intelligent Internet of Things. Therefore, it is urgent to develop a self-powered sensor with maintenance-free and long service life.

[0003] As a kind of energy conversion device, the friction nanogenerator converts mechanical energy into electrical energy through the triboelectric effect. The sensor based on friction nanogenerator has been proved to be a high-reliability and low-cost vibration detection device. Most friction nanogenerators work in the low frequency range below 100 Hz, and the existing technology also reports that it can work in the high frequency range of 1000 Hz, but its sensitivity still needs to be improved. To obtain a wider bandwidth, a smaller driving resistance is required; at the same time, to obtain higher sensitivity, more sufficient mass is required to obtain energy. Therefore, how to balance the relationship between driving resistance and mass has become a key problem in designing a self-powered sensor that can measure a wider frequency range and higher sensitivity. SUMMARY

[0004] One of the purposes of the present application is to provide a vibration sensor based on friction nanogenerator, which has the functions of ultra-wide frequency response and high sensitivity, and solves the defects existing in the existing self-powered sensor.

[0005] In order to achieve the above purpose, a vibration sensor based on friction nanogenerator is provided, which comprises a base, an outer shell arranged on the base, a moving part and a fixed part; the fixed part comprises a fixed magnet arranged on one side of the base, and a stainless steel gasket, a first buffer layer, a polytetrafluoroethylene film and a first copper foil layer arranged in the inner part of the outer shell and connected in sequence from bottom to top on the base; the moving part is located in the inner part of the outer shell and suspended above the fixed part, and comprises a suspended magnet, a stainless steel washer, a second buffer layer and a second copper foil layer arranged in sequence from top to bottom.

[0006] Further, the outer shell is a cylindrical outer shell body and a circular plate-shaped top cover, the top cover is detachably mounted on the upper end of the outer shell body, and the lower end of the outer shell body is detachably mounted on the base.

[0007] Further, the material of the outer shell is photosensitive resin.

[0008] Further, the material of the first and second buffer layers is a buffer material, including sponge.

[0009] Further, the distance gap between the high polymer friction layer of the fixed component and the second metal friction layer of the moving component constitutes a quasi-zero stiffness structure.

[0010] Further, the material of the first and second metal friction layers includes copper, aluminum and silver.

[0011] Further, the material of the high polymer friction layer includes polytetrafluoroethylene, polydimethylsiloxane, polyvinyl chloride and polyimide.

[0012] Principles and advantages:

[0013] 1. The working process of the scheme is based on the contact separation mode. The suspended magnet of the moving component and the fixed magnet of the fixed component are assembled in a repulsive manner to ensure that the moving part is in a suspended state. In the moving component, the stainless steel washer serves as the mass concentration point, and the sponge serves as the buffer material to ensure that the two friction materials (the second copper foil layer and the polytetrafluoroethylene film) are in complete contact. The second copper foil layer serves as both a friction material and an electrode. The suspended magnet is attached to the stainless steel washer, allowing the second copper foil layer to move up and down when the vibration source vibrates. The entire structure is small in size and easy to assemble.

[0014] 2. Under initial conditions, the gap between the two friction energy storage materials (the second copper foil layer and the polytetrafluoroethylene film) is close to zero, preferably, to form a quasi-zero stiffness structure. At the same time, the magnetic induction intensity of the suspended magnet and the weight of the moving component are optimized, so that the distance and pressure between the polytetrafluoroethylene and the copper electrode are zero in the initial state, minimizing the driving force required for the contact separation of the friction nanogenerator. When the suspended magnet is just at the contact distance of zero through the suspended magnet, the gravitational force and the magnetic force of the moving part are balanced. At this time, when the system is subjected to medium-high frequency vibration, the stiffness of the system is approximately zero.

[0015] 3. When the second copper foil layer is in contact with the polytetrafluoroethylene film, the electron clouds of the two film surfaces overlap, and part of the electrons from the second copper foil layer enter the deeper potential well of the polytetrafluoroethylene film. Because the electronegativity of the polytetrafluoroethylene film is much higher than that of copper, the free electrons on the surface of the second copper foil layer are transferred to the lowest empty molecular orbital of the PTFE interface, so the polytetrafluoroethylene film is negatively charged and the copper is positively charged. When an external vibration source is loaded on the device, the magnetic force on the moving parts can counteract gravity, and the suspended magnet starts to move the stainless steel washer and the second copper foil layer upwards, and the second copper foil layer starts to separate from the polytetrafluoroethylene film. At this time, the polytetrafluoroethylene film obtains electrons from the second copper foil layer, and the current flows from the bottom electrode first copper foil layer to the top electrode second copper foil layer through the external circuit. Conversely, when the vibration source moves downward, the displacement of the moving parts reaches a maximum value, and the second copper foil layer will start to approach the polytetrafluoroethylene film, and the current flows from the top electrode second copper foil layer to the bottom electrode first copper foil layer due to the potential difference of the local electric field. Finally, the moving parts return to their original positions, the charge distribution returns to the initial state, and a motion cycle is completed.

[0016] 4. When the system vibration frequency is greater than 100 Hz, the external vibration excitation amplitude is micron level, and when the distance between the two magnets increases to a certain value, the equivalent stiffness value approaches zero. At this point, the system is close to a critical state of non-resonance. Due to the adoption of quasi-zero stiffness structure, the system has excellent frequency response performance in the medium and high frequency band.

[0017] 5. The present application has good linear response to acceleration in each detection of high frequency (greater than 400 Hz), and the output response of the friction nanogenerator to the single-period vibration pulse vibration signal of different accelerations shows that its response sensitivity is very high. The present application can realize and meet the performance requirements of wide frequency response and high sensitivity. The sensor network composed of the present application is expected to realize control logic feedback and potential application of fault monitoring through detection of key components of main equipment.

[0018] The second object of the present application is to provide a state and fault detection system comprising a vibration sensor based on a friction nanogenerator and a control device, the vibration sensor being used to convert the vibration of a target detection component into a voltage signal, and the control device comprising a data filtering and data acquisition module and a controller, the data filtering and data acquisition module being used to convert the analog voltage signal into a digital signal, and the controller comprising:

[0019] a feature extraction module for extracting features of the digital signal from the time domain and frequency domain of the digital signal, the features including skewness, kurtosis, wave crest factor, shape factor, pulse factor, gap factor, frequency centroid, mean square frequency, root mean square frequency, variance frequency, and root variance frequency;

[0020] State and fault analysis module: used for importing the features of the extracted digital signal into the trained state and fault analysis model, analyzing and predicting and outputting the running state and fault type of the target detection component.

[0021] Principles and advantages:

[0022] The vibration sensor designed based on the scheme converts the vibration of the key component (target detection component) into a voltage signal. Then, through the data filtering and data acquisition module, the analog voltage signal is converted into a digital signal. By further extracting and identifying the information contained in the voltage signal, such as extracting the features of the collected signal from the time domain and frequency domain signals. The collected features have 11 dimensionless features, such as skewness, kurtosis, peak factor, shape factor, pulse factor, gap factor, frequency centroid, mean square frequency, root mean square frequency, variance frequency and root variance frequency. Then, the conventional machine learning algorithm can be used to analyze and identify the signal of the running state and fault type of the vibration source. Among them, since the vibration sensor has the effect of measuring a wider frequency range and higher sensitivity, the analysis and identification of the signal of the running state and fault type of the vibration source are also more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the axial view of the vibration sensor based on the friction nanogenerator according to the embodiment of the application;

[0024] Figure 2 is the cross-sectional view of the vibration sensor;

[0025] Figure 3 is the axial exploded view of the vibration sensor;

[0026] Figure 4 is the flowchart of the state and fault detection system according to the embodiment of the application;

[0027] Figure 5 represents the function of open circuit voltage with vibration frequency under different accelerations, and the inserted figure is the enlarged output signal diagram less than 220Hz;

[0028] Figure 6 represents the function of short circuit current with vibration frequency under different accelerations, and the inserted figure is the enlarged output signal diagram less than 220Hz;

[0029] Figure 7 represents the curve of open circuit voltage with acceleration under different frequencies of 400-1800Hz;

[0030] Figure 8 represents the curve of open circuit voltage with acceleration under different frequencies of 2000-4000Hz. DETAILED DESCRIPTION

[0031] The following will be further described in detail through specific embodiments:

[0032] The reference signs in the attached drawings of the specification include: top cover 1, shell 2, stainless steel gasket 3, second buffer layer 4, second copper foil layer 5, polytetrafluoroethylene film 6, first copper foil layer 7, first buffer layer 8, stainless steel gasket 9, base 10, fixed magnet 11, suspended magnet 12.

[0033] Embodiment

[0034] A vibration sensor based on a friction nanogenerator, substantially as shown in Figure 1 , Figure 2 , Figure 3 , comprising a base 10 and a shell 2 covering the base 10, and a moving part and a fixed part.

[0035] The shell 2 is a cylindrical shell body and a circular plate-shaped top cover 1, which is detachably mounted on the upper end of the shell body, and the lower end of the shell body is detachably mounted on the base 10. In this embodiment, the top cover 1 is adhesively mounted and fixed on the upper end of the shell body, and the lower end of the shell body is adhesively mounted and fixed on the base 10. In other embodiments, detachable connection can be achieved by thread, buckle and the like. The material of the shell 2 is photosensitive resin, which is light and easy to carry.

[0036] The fixed part includes a fixed magnet 11 arranged on one side of the base 10, and a stainless steel gasket 9, a first buffer layer 8, a first metal friction layer (corresponding to the first copper foil layer 7) and a high polymer friction layer (corresponding to the polytetrafluoroethylene film 6) arranged in the shell 2 in sequence from bottom to top on the base 10. In this embodiment, the fixed magnet 11 is mounted in the mounting groove arranged on the lower surface of the base 10 and fixed by adhesion. In other embodiments, the fixed magnet 11 can be mounted in the mounting groove arranged on the upper surface of the base 10.

[0037] The moving part is located in the shell 2 and suspended above the fixed part, and includes a suspended magnet 12, a stainless steel gasket 3, a second buffer layer 4 and a second metal friction layer (corresponding to the second copper foil layer 5) arranged in sequence from top to bottom. The materials of the first buffer layer 8 and the second buffer layer 4 are both buffer materials, including sponge and silica gel. In this embodiment, sponge is used. The materials of the first metal friction layer and the second metal friction layer include copper, aluminum and silver. In this embodiment, copper is preferred, and is arranged as the first copper foil layer 7 and the second copper foil layer 5, respectively. The material of the high polymer friction layer includes polytetrafluoroethylene, polydimethylsiloxane, polyvinyl chloride and polyimide. In this embodiment, polytetrafluoroethylene is preferred, and is arranged as the polytetrafluoroethylene film 6.

[0038] The moving part and the fixed part are based on the contact separation mode, the suspension magnet 12 of the moving part and the fixed magnet 11 of the fixed part are assembled in repulsion to ensure that the moving part is in a suspended state. At the same time, the distance gap between the polytetrafluoroethylene film 6 of the fixed part and the second copper foil layer 5 of the moving part constitutes a quasi-zero stiffness structure, that is, the gap between the two friction energy storage materials is close to zero. The gap d between the two friction energy storage materials is 0, at this time the magnetic force F(d+B) acting on the moving part can be balanced with its gravity G, and the moving part is in a suspended state, that is

[0039] F(d+B)=G

[0040] In the formula, d is the distance between the moving part and the fixed part, and B is the distance between the two magnets (fixed magnet 11 and suspension magnet 12) when d=0.

[0041] In the moving part, the stainless steel washer 3 is the mass concentration point, and the sponge is the buffer material, which ensures that the two friction materials (the second copper foil layer 5 and the polytetrafluoroethylene film 6) are in complete contact. The second copper foil layer 5 serves as both a friction material and an electrode, and the suspension magnet 12 is attached to the stainless steel washer 3, so that the second copper foil layer 5 can move up and down when the vibration source vibrates.

[0042] When the second copper foil layer 5 contacts the polytetrafluoroethylene film 6, the electron clouds on the surfaces of the two films overlap, and some of the electrons from the second copper foil layer 5 enter the deeper potential well of the polytetrafluoroethylene film 6. Because the electronegativity of the polytetrafluoroethylene film 6 is much higher than that of copper, the free electrons on the surface of the second copper foil layer 5 transfer to the lowest empty molecular orbital of the PTFE interface, so the polytetrafluoroethylene film 6 is negatively charged and the copper is positively charged. Because when the external vibration source is loaded on the device, the magnetic force on the moving part can balance the gravity, the suspended magnet starts to move the stainless steel washer 3 and the second copper foil layer 5 upwards, and the second copper foil layer 5 starts to separate from the polytetrafluoroethylene film 6. At this time, the polytetrafluoroethylene film 6 obtains electrons from the second copper foil layer 5, and the current flows from the bottom electrode first copper foil layer 7 to the top electrode second copper foil layer 5 through the external circuit. Conversely, when the vibration source moves downward, the displacement of the moving part reaches a maximum value, and the second copper foil layer 5 begins to approach the polytetrafluoroethylene film 6, and the current flows from the top electrode second copper foil layer 5 to the bottom electrode first copper foil layer 7 due to the potential difference of the local electric field. Finally, the moving part returns to its original position, the charge distribution returns to the initial state, and a motion cycle is completed.

[0043] The output open-circuit voltage and short-circuit current of the high-sensitivity vibration sensor based on the triboelectric nanogenerator under different accelerations and vibration frequencies of 2.5-4000 Hz are measured, as shown in Figure 5 and Figure 6 The blue, red and blue (in Figure 6The lines and dots represent the peak output electrical signals of the high-sensitivity vibration sensor based on the triboelectric nanogenerator under 0.5 g, 1 g and 1.5 g accelerations, respectively. The maximum open-circuit voltage and short-circuit current of the output are 207.11 V and 18.23 μA, respectively, under the conditions of a vibration frequency of 22.5 Hz and an acceleration of 1.5 g.

[0044] To further verify the linear relationship between the output voltage signal and the excitation vibration acceleration of the high-sensitivity vibration sensor based on the triboelectric nanogenerator at different frequencies, the open-circuit voltage of the high-sensitivity vibration sensor based on the triboelectric nanogenerator was measured in the vibration frequency range of 400-1800 Hz. As shown in Figure 7 , the acceleration function is 0.5-6 g, and the linear range is 0.75-2.81 V / g. In the vibration frequency range of 2000-4000 Hz, the relationship between the output voltage of the high-sensitivity vibration sensor based on the triboelectric nanogenerator and the different accelerations of 0.1-1.5 g is shown in Figure 8 . Obviously, when the frequency is greater than 400 Hz, the output voltage signal has a good linear relationship with various vibration accelerations, and the linear range of the high-sensitivity vibration sensor based on the triboelectric nanogenerator is 0.08-2.81 V / g. In particular, the high-sensitivity vibration sensor based on the triboelectric nanogenerator can detect high-frequency small acceleration vibration signals (frequency up to 4000 Hz, acceleration as low as 0.1 g). In summary, the vibration sensor of the present scheme has the functions of ultra-wide frequency response and high sensitivity.

[0045] A state and fault detection system, as shown in Figure 4 , includes a vibration sensor based on a triboelectric nanogenerator and a control device, the vibration sensor is used to convert the vibration of a target detection component into a voltage signal, the target detection component includes a motor, a speed reducer, a bearing, a compressor, a blower and other vibration sources. The control device includes a data filtering and data acquisition module and a controller, the data filtering and data acquisition module is used to convert the analog voltage signal into a digital signal, and the controller includes:

[0046] a feature extraction module for extracting features of the digital signal from the time domain and frequency domain of the digital signal, the features including skewness, kurtosis, peak factor, shape factor, pulse factor, gap factor, frequency centroid, mean square frequency, root mean square frequency, variance frequency and root variance frequency;

[0047] a state and fault analysis module for importing the extracted features of the digital signal into a trained state and fault analysis model, analyzing, predicting and outputting the running state and fault type of the target detection component.

[0048] Based on the foregoing design of the vibration sensor, the vibration of the key component (target detection component) is converted into a voltage signal. Then, through the data filtering and data acquisition module, the analog voltage signal is converted into a digital signal. By further extracting and identifying the information contained in the voltage signal, such as extracting the characteristics of the collected signal from the time domain and frequency domain signals. The collected characteristics have 11 dimensionless characteristics, such as skewness, kurtosis, wave peak factor, shape factor, pulse factor, gap factor, frequency centroid, mean square frequency, root mean square frequency, variance frequency and root variance frequency. Then, the conventional machine learning algorithm can be used to analyze and identify the signal of the running state and fault type of the vibration source. Among them, since the vibration sensor has the effect of measuring a wider frequency range and higher sensitivity, the analysis and identification of the signal of the running state and fault type of the vibration source are also more accurate.

[0049] The above is only an embodiment of the present application, and the common knowledge of the specific structure and characteristics in the scheme is described too much. The ordinary skilled person in the art knows all the ordinary technical knowledge in the field of the application before the application date or the priority date, can know all the prior art in the field, and has the ability to apply conventional experimental means before that date. The ordinary skilled person in the art can improve and implement the present scheme under the guidance of the present application, and some typical known structures or known methods should not be an obstacle to the implementation of the present application by the ordinary skilled person in the art. It should be pointed out that for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, and these will not affect the effect and practicality of the patent. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. A vibration sensor based on a frictional nanogenerator, characterized by: The application relates to a friction nanogenerator-based vibration sensor and a control device, wherein the vibration sensor is used for converting the vibration of a target detection component into a voltage signal; the control device comprises a data filtering and data acquisition module and a controller; the data filtering and data acquisition module is used for converting an analog voltage signal into a digital signal; the controller comprises: a feature extraction module which is used for extracting the features of the digital signal from the time domain and the frequency domain of the digital signal, wherein the features include skewness, kurtosis, wave crest factor, shape factor, pulse factor, gap factor, frequency centroid, mean square frequency, root mean square frequency, variance frequency and root variance frequency; and a state and fault analysis module which is used for importing the extracted features of the digital signal into a trained state and fault analysis model, analyzing, predicting and outputting the running state and the fault type of the target detection component. The distance gap between the high polymer friction layer of the fixed component and the second metal friction layer of the moving component constitutes a quasi-zero stiffness structure. 2.The vibration sensor based on the friction nanogenerator of claim 1, wherein: The shell is a cylindrical shell body and a circular plate-shaped top cover; the top cover is detachably mounted on the upper end of the shell body; and the lower end of the shell body is detachably mounted on the base. 3.The vibration sensor based on the friction nanogenerator of claim 2, wherein: The material of the shell is photosensitive resin. 4.The vibration sensor based on the friction nanogenerator of claim 1, wherein: The materials of the first buffer layer and the second buffer layer are both buffer materials, and the buffer materials include sponge. 5.The vibration sensor based on the friction nanogenerator of claim 4, wherein: The materials of the first metal friction layer and the second metal friction layer include one of copper, aluminum and silver. 6.The vibration sensor based on the friction nanogenerator of claim 4, wherein: The material of the high polymer friction layer includes one of polytetrafluoroethylene, polydimethylsiloxane, polyvinyl chloride and polyimide.

7. A condition and fault detection system characterised by: The application relates to a friction nanogenerator-based vibration sensor and a control device, wherein the vibration sensor is used for converting the vibration of a target detection component into a voltage signal; the control device comprises a data filtering and data acquisition module and a controller; the data filtering and data acquisition module is used for converting an analog voltage signal into a digital signal; the controller comprises: a feature extraction module which is used for extracting the features of the digital signal from the time domain and the frequency domain of the digital signal, wherein the features include skewness, kurtosis, wave crest factor, shape factor, pulse factor, gap factor, frequency centroid, mean square frequency, root mean square frequency, variance frequency and root variance frequency; and a state and fault analysis module which is used for importing the extracted features of the digital signal into a trained state and fault analysis model, analyzing, predicting and outputting the running state and the fault type of the target detection component. ​ ​

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