Method, device and system for detecting demagnetization of permanent magnet material

Abstract

The invention relates to a permanent magnet material demagnetization detection method, device and system, and the method comprises the steps: obtaining a force change signal of a target permanent magnet material from a permanent magnet material demagnetization detection device; and judging the demagnetization state of the target permanent magnet material according to the force change signal. Compared with a mode of detecting the magnetic field intensity of the surface of the permanent magnet material by using a Hall probe to carry out demagnetization detection on the permanent magnet material, the method in the embodiment is not influenced by manual operation. Compared with a method for evaluating the health state of the permanent magnet material by using a camera to shoot cracks, recesses and the like on the surface of the material, the relationship between the force change signals and the demagnetization degrees is clear, and different demagnetization degrees correspond to different force change signals; therefore, the method has higher detection accuracy and can judge the specific demagnetization degree. In conclusion, the permanent magnet material demagnetization detection method in the embodiment solves the problem that an existing permanent magnet material demagnetization detection method is low in detection accuracy.

Description

Technical Field

[0001] This application relates to the field of permanent magnet material detection, and particularly to a method, device, and system for demagnetization detection of permanent magnet materials. Background Art

[0002] Due to its excellent high remanence characteristics and coercivity, combined with its outstanding anti-demagnetization ability and wide temperature range adaptability, permanent magnet materials exhibit excellent magnetic property retention characteristics under complex working conditions. This material property advantage not only effectively overcomes the interference of environmental temperature fluctuations on magnetic properties but also maintains a stable magnetic flux output under long-term alternating magnetic fields. It has become a core material in high-tech and advanced manufacturing fields, especially in fields such as robots, new energy vehicles, aerospace, intelligent sensing, and communication base stations, where it has an indispensable application position, such as magnetic encoders, permanent magnet synchronous motors, satellite attitude control components, magnetic sensors, filters, etc. Due to the natural aging of permanent magnet materials, the complexity of the actual operating conditions of the equipment they are in, and high-temperature and humid working environments, etc., irreversible demagnetization of permanent magnet materials is likely to occur. However, after a permanent magnet material demagnetizes, it may lead to a decline in the performance of the associated equipment, energy waste, production downtime, increased maintenance costs, and potential safety hazards, which seriously affect enterprise operations and production efficiency. Therefore, laying a foundation for the regular maintenance and fault tolerance compensation of permanent magnet materials and achieving high-performance and stable operation of equipment is of great significance for promoting the development of the manufacturing field.

[0003] Currently, there are mainly two methods for demagnetization detection of permanent magnet materials. One is to detect the demagnetization of permanent magnet materials by using a Hall probe to detect the magnetic field strength on the surface of the permanent magnet material. This method is affected by factors such as the thickness of the Hall probe element and the level of the user, resulting in large differences in measurement data, and thus low detection accuracy and detection efficiency. The other is to evaluate the health status of permanent magnet materials by using a camera to photograph cracks, depressions, etc. on the material surface. Due to its excessive dependence on the texture information on the material surface and strong randomness, the error is large and the specific demagnetization degree cannot be judged.

[0004] Regarding the problem of low detection accuracy of the current demagnetization detection methods for permanent magnet materials, no effective solution has been proposed yet. Summary of the Invention

[0005] In the present invention, a method, device, and system for demagnetization detection of permanent magnet materials are provided to solve the problem of low detection accuracy of the current demagnetization detection methods for permanent magnet materials.

[0006] In a first aspect, the present invention provides a method for demagnetization detection of permanent magnet materials, including:

[0007] Obtain a force change signal regarding the target permanent magnet material from a device for detecting demagnetization of the permanent magnet material;

[0008] Judge the demagnetization state of the target permanent magnet material according to the force change signal;

[0009] Wherein, the device for detecting demagnetization of the permanent magnet material includes a transmission device, a fixing bracket, and a magnetic force signal acquisition device; the transmission device is used to move the target permanent magnet material; the fixing bracket is fixedly installed directly above the transmission path of the transmission device; the magnetic force signal acquisition device includes a rectangular permanent magnet material, a first thin film pressure sensor, and a second thin film pressure sensor. The first thin film pressure sensor and the second thin film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnet material and their vertical projections overlap. The fixing bracket fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin film pressure sensor and the lower surface of the second thin film pressure sensor;

[0010] During the process of the transmission device moving the target permanent magnet material, the first thin film pressure sensor and the second thin film pressure sensor provide the force change signal.

[0011] In a second aspect, a device for detecting demagnetization of a permanent magnet material is provided in the present invention, including:

[0012] A signal acquisition module, configured to obtain a force change signal regarding the target permanent magnet material from a device for detecting demagnetization of the permanent magnet material;

[0013] A demagnetization detection module, configured to judge the demagnetization state of the target permanent magnet material according to the force change signal;

[0014] Wherein, the device for detecting demagnetization of the permanent magnet material includes a transmission device, a fixing bracket, and a magnetic force signal acquisition device; the transmission device is used to move the target permanent magnet material; the fixing bracket is fixedly installed directly above the transmission path of the transmission device; the magnetic force signal acquisition device includes a rectangular permanent magnet material, a first thin film pressure sensor, and a second thin film pressure sensor. The first thin film pressure sensor and the second thin film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnet material and their vertical projections overlap. The fixing bracket fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin film pressure sensor and the lower surface of the second thin film pressure sensor;

[0015] During the process of the transmission device moving the target permanent magnet material, the first thin film pressure sensor and the second thin film pressure sensor provide the force change signal.

[0016] In a third aspect, the present invention provides a computer, including a memory and a processor. A computer program is stored in the memory, and the processor is configured to run the computer program to execute the method for detecting demagnetization of the permanent magnetic material as described in the first aspect of the claims.

[0017] In a fourth aspect, the present invention provides a system for detecting demagnetization of a permanent magnetic material, including:

[0018] a device for detecting demagnetization of the permanent magnetic material and the computer as described in the first aspect;

[0019] The device for detecting demagnetization of the permanent magnetic material includes a transmission device, a fixing frame, and a magnetic force signal acquisition device. The transmission device is used to move the target permanent magnetic material. The fixing frame is fixedly installed directly above the transmission path of the transmission device. The magnetic force signal acquisition device includes a rectangular permanent magnetic material, a first thin film pressure sensor, and a second thin film pressure sensor. The first thin film pressure sensor and the second thin film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnetic material and their vertical projections overlap. The fixing frame fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin film pressure sensor and the lower surface of the second thin film pressure sensor.

[0020] During the process of the transmission device moving the target permanent magnetic material, the first thin film pressure sensor and the second thin film pressure sensor provide a force change signal to the computer.

[0021] Compared with the related art, the method for detecting demagnetization of the permanent magnetic material first obtains a force change signal about the target permanent magnetic material through the device for detecting demagnetization of the permanent magnetic material, and then determines the demagnetization state of the target permanent magnetic material according to the force change signal. Compared with the method of detecting demagnetization of the permanent magnetic material by using a Hall probe to detect the magnetic field strength on the surface of the permanent magnetic material, the method in this embodiment is not affected by manual operation. Compared with the method of evaluating the health state of the permanent magnetic material by using a camera to photograph cracks, depressions, etc. on the surface of the material, since the relationship between the force change signal and the demagnetization degree is relatively clear, different demagnetization degrees correspond to different force change signals, so the method in this embodiment has higher detection accuracy and can determine the specific demagnetization degree. In summary, the method for detecting demagnetization of the permanent magnetic material in this embodiment solves the problem of low detection accuracy of the current method for detecting demagnetization of the permanent magnetic material.

[0022] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more concise and understandable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1It is the flowchart of the method for demagnetization detection of permanent magnet materials provided in this embodiment;

[0024] Figure 2 It is the structural diagram of the system for demagnetization detection of permanent magnet materials provided in this embodiment;

[0025] Figure 3 It is the schematic diagram of the cooperation between the magnetic force signal acquisition device and the fixing bracket provided in this embodiment;

[0026] Figure 4 It is the force analysis diagram when the rectangular magnet material repels the target magnet material in this embodiment;

[0027] Figure 5 It is the force change signal diagram when the rectangular magnet material repels the target magnet material in this embodiment;

[0028] Figure 6 It is the force analysis diagram when the rectangular magnet material attracts the target magnet material in this embodiment;

[0029] Figure 7 It is the force change signal diagram when the rectangular magnet material attracts the target magnet material in this embodiment;

[0030] Figure 8 It is the force change signal diagram when the rectangular magnet material repels the target magnet material with different demagnetization degrees in this embodiment;

[0031] Figure 9 It is the force change signal diagram when the rectangular magnet material attracts the target magnet material with different demagnetization degrees in this embodiment;

[0032] Figure 10 It is the schematic diagram of the change of the force change signal from Cartesian coordinates to polar coordinates in this embodiment;

[0033] Figure 11 It is the detailed comparison diagram of the rainbow diagrams converted from the force change signals of the target permanent magnet material in five different demagnetization states in this embodiment;

[0034] Figure 12 It is the architecture diagram of the DMA-RpViT demagnetization detection model provided in this embodiment;

[0035] Figure 13 It is the architecture diagram of the downsampling layer in the DMA-RpViT demagnetization detection model provided in this embodiment;

[0036] Figure 14 It is the architecture diagram of the feature extraction stage in the DMA-RpViT demagnetization detection model provided in this embodiment;

[0037] Figure 15It is the architecture diagram of the DMA module in the DMA-RpViT demagnetization detection model provided in this embodiment. Detailed implementation manners

[0038] To understand the purpose, technical solution and advantages of this application more clearly, the following describes and explains this application in combination with the accompanying drawings and embodiments.

[0039] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meanings understood by those with ordinary skills in the technical field to which this application belongs. In this application, words such as "a", "one", "a kind of", "the", "these" and the like do not indicate a limitation in quantity, and they can be singular or plural. The terms "including", "comprising", "having" and any variants thereof involved in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent in these processes, methods, products or devices. The terms "connected", "coupled" and the like involved in this application do not limit to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, and B exists alone. Usually, the character " / " indicates that the objects associated before and after are an "or" relationship. The terms "first", "second", "third" and the like involved in this application only distinguish similar objects and do not represent a specific sorting for the objects.

[0040] In this embodiment, a method for detecting the demagnetization of a permanent magnet material is provided, and this method is executed by a computer. Figure 1 It is the flowchart of the method for detecting the demagnetization of a permanent magnet material provided in this embodiment. As Figure 1 shown, this process includes steps S110 and S120.

[0041] Step S110, obtain the force change signal about the target permanent magnet material from the device for detecting the demagnetization of the permanent magnet material provided in this embodiment.

[0042] S120, judge the demagnetization state of the target permanent magnet material according to the force change signal.

[0043] Refer to Figure 2, the equipment for detecting the demagnetization of the permanent magnet material provided in this embodiment includes a transmission device 10, a fixing frame 20, and a magnetic force signal acquisition device 30; the transmission device 10 is used to move the target permanent magnet material 00; the fixing frame 20 is fixedly installed directly above the transmission path of the transmission device 10. Refer to Figure 3 , the magnetic force signal acquisition device 30 includes a rectangular permanent magnet material 33, a first thin-film pressure sensor 31, and a second thin-film pressure sensor 32. The first thin-film pressure sensor 31 and the second thin-film pressure sensor 32 are respectively attached to the upper and lower surfaces of the rectangular permanent magnet material 33 and their vertical projections overlap. The fixing frame 20 fixes the magnetic force signal acquisition device 30 by contacting the upper surface of the first thin-film pressure sensor 31 and the lower surface of the second thin-film pressure sensor 32; during the process of the transmission device 10 moving the target permanent magnet material 00, the first thin-film pressure sensor 31 and the second thin-film pressure sensor 32 provide force change signals.

[0044] Exemplarily, the permanent magnet material can be a neodymium iron boron permanent magnet. The target permanent magnet material is the permanent magnet to be detected. The thin-film pressure sensor is a one-dimensional single-point pressure sensor.

[0045] Continue to refer to Figure 2 , in this embodiment, the transmission device 10 is a conveyor belt 11, and a transmission path is formed when the conveyor belt 11 moves. In order to ensure that the conveyor belt 11 can stably move the target permanent magnet material 00, that is, there is no relative sliding between the conveyor belt 11 and the target permanent magnet material 00, a fixture can be fixedly arranged on the surface of the conveyor belt 11, and the target permanent magnet material 00 is clamped by the fixture. In order to ensure that the detection result is not affected by the equipment for detecting the demagnetization of the permanent magnet material, the conveyor belt 11, the fixing frame 20, and the fixture should not have magnetism. For example, the fixing frame 20 and the fixture are made of plastic, and the conveyor belt 11 is made of rubber. At the same time, the fixing frame 20 and the fixture can have a telescopic function and are respectively used to clamp rectangular permanent magnet materials 33 and target permanent magnet materials 00 with different sizes. Preferably, the fixing frame 20 is fixedly installed directly above the middle of the transmission path of the transmission device 10.

[0046] The principle of demagnetization detection by the above-mentioned device is as follows: When the target permanent magnet material 00 approaches, passes by, and then moves away from directly below the rectangular permanent magnet material 33, the force between the target permanent magnet material 00 and the rectangular permanent magnet material 33 will change, causing the force exerted on the two thin-film pressure sensors by the rectangular permanent magnet material 33 to change. Therefore, the force change signals of the two thin-film pressure sensors reflect the change in the force between the rectangular permanent magnet material 33 and the target permanent magnet material 00. For a target permanent magnet material 00 of a certain specification model, when it is in the non-demagnetized state, the force change signals of the two thin-film pressure sensors can be measured. When the target permanent magnet material 00 is demagnetized, the force between it and the rectangular permanent magnet material 33 becomes smaller, correspondingly causing different force change signals in the two thin-film pressure sensors. Therefore, based on the force change signals of the target permanent magnet material 00, it can be determined whether demagnetization occurs and the degree of demagnetization. Among them, the rectangular permanent magnet material 33 can be a healthy non-demagnetized permanent magnet material.

[0047] Furthermore, the method for detecting demagnetization of permanent magnet materials provided in this embodiment can detect multiple target permanent magnet materials 00 simultaneously. Specifically, multiple target permanent magnet materials 00 can be placed equidistantly on the conveyor belt 11. At this time, the magnetic force signal acquisition device 30 can sequentially obtain the force change signals of each target permanent magnet material 00. It should be noted that in order to ensure that there is no mutual interference between the target permanent magnet materials 00, a sufficient distance should be ensured between adjacent target permanent magnet materials 00 so that the two do not simultaneously exert forces on the rectangular permanent magnet material 33. This distance needs to be determined according to the specific specifications of the target permanent magnet material 00 and the rectangular permanent magnet material 33.

[0048] Correspondingly, in order to determine the relative positions of the target permanent magnet materials 00 in the transmission path, an optoelectronic sensor 40 can be fixedly arranged on one side of the transmission path. The position of the optoelectronic sensor 40 in the transmission device 10 is fixed and it does not move in the transmission path. For example, the optoelectronic sensor 40 can be arranged on the side plate of the conveyor belt 11. Since the relative position of the optoelectronic sensor 40 in the transmission path is known, when a target permanent magnet material 00 passes in front of the optoelectronic sensor 40, it can be detected by the optoelectronic sensor 40, and then the relative position of the target permanent magnet material 00 in the transmission path at this time can be determined. Since the distance between adjacent target permanent magnet materials 00 is known. Therefore, for each target permanent magnet material 00, the relationship between the force change signal and the relative position of the target permanent magnet material 00 can be determined, that is, a force signal change curve with the relative position of the target permanent magnet material 00 as the abscissa and the force signal magnitude as the ordinate is established.

[0049] Further, in this embodiment, to ensure that the measurement results of the first thin-film pressure sensor 31 and the second thin-film pressure sensor 32 do not interfere with each other, both should be installed parallel to the rectangular permanent magnet material 33 in a healthy state, and the contact surfaces on the upper and lower surfaces of the rectangular permanent magnet material 33 should correspond to the same (i.e., the vertical projections overlap). To ensure the accuracy of the measurement results, the target permanent magnet material 00 to be detected must pass directly below the rectangular permanent magnet material 33 in a healthy state, so that the directions of the instantaneous suction and repulsion forces when it passes through are perpendicular.

[0050] The following is an example of the use process of the equipment for detecting the demagnetization of permanent magnet materials.

[0051] 1. Place the target permanent magnet material to be tested on the retractable plastic fixture on the conveyor belt. The retractable plastic fixture is suitable for target permanent magnet materials of different sizes. The target permanent magnet material to be tested moves at a constant speed with the conveyor belt and is located at the midline position of the conveyor belt so that it can pass directly below the rectangular permanent magnet material.

[0052] 2. When the photoelectric sensor detects the target permanent magnet material, it feeds the position signal back to the computer. The computer starts to read the data of the upper and lower thin-film pressure sensors, and can obtain the change in the distance between the target permanent magnet material and the rectangular permanent magnet material. Finally, by calculation, the curve of the pressure values of the first thin-film pressure sensor and the second thin-film pressure sensor changing with the relative position of the target permanent magnet material is obtained, that is, the force change signal. Among them, when the target permanent magnet material repels the rectangular permanent magnet material, the rectangular permanent magnet material receives an upward repulsive force, and the pressure value of the first thin-film pressure sensor increases, while the pressure value of the second thin-film pressure sensor decreases. When the target permanent magnet material attracts the rectangular permanent magnet material, the rectangular permanent magnet material receives a downward suction force, the pressure value of the first thin-film pressure sensor remains unchanged, and the pressure value of the second thin-film pressure sensor increases.

[0053] In this step, the suction and repulsion forces between two neodymium-iron-boron permanent magnets can be approximately calculated using the magnetic dipole model. A magnetic dipole is a system composed of two magnetic charges with equal magnitudes, opposite directions, and a very small distance between them. The expression for the mutual force between two magnetic dipoles in general is:

[0054]

[0055] Among them, and are the magnetic moments of the two magnetic dipoles, is the vector pointing from one magnetic dipole to the other, r is the modulus, μ0 is the vacuum magnetic permeability, and its exact value is 4π×10 -7 T·m / A.

[0056] (1) When the force between the target permanent magnet material and the rectangular permanent magnet material is repulsive:

[0057] Referring to Figure 4 , F is the repulsive force between the two. Since a one-dimensional single-point pressure sensor is used in this embodiment, only the vertical component force F1 = Fsinθ is considered. G is the gravity existing in the rectangular permanent magnet material 33 itself. F 上 is the pressure measured by the first thin-film pressure sensor 31, and F 下 is the pressure measured by the second thin-film pressure sensor 32.

[0058] From Figure 5 it can be seen that when the target permanent magnet material (the permanent magnet to be measured) is at point A, F 下 = G, and F1 gradually increases from 0N. When the target permanent magnet material gradually approaches the rectangular permanent magnet material along with the conveyor belt, the repulsive force between the two gradually increases. When F1 < G, F 上 is 0N. As the distance gets closer, F 下 = G - F1, and its variation is a gradually decreasing curve. When the target permanent magnet material is at point B, F1 = G, and at this time F 上 is 0N, and F 下 is also 0N. As the distance gradually decreases, F1 gradually increases. When F1 > G, F 下 is 0N. As the distance gets closer, F 上 = F1 - G, and its variation is a gradually increasing curve. When the target permanent magnet material is at point C, when the target permanent magnet material is exactly directly below the rectangular permanent magnet material, the curve rises to the highest point. As the position continuously moves away from directly below the rectangular permanent magnet material, F1 gradually decreases, and F 上 = F1 - G, and its variation is a gradually decreasing curve. When the target permanent magnet material is at point D, F1 = G, and at this time F 上 is 0N, and F 下 is also 0N. Subsequently, since F1 < G, F 上 is always 0N. As the distance continuously increases, F 下 = G - F1, and its variation is a gradually increasing curve. Until the target permanent magnet material is at point E, F1 decreases to 0N, and F 下 = G.

[0059] Let it be a complete cycle from when F1 > 0 starts to when F1 = 0 ends. Since there is a situation where when F 上 = 0N, F 下 is not 0. When F 下 = 0N, F 上 is not 0. For the data collected by the two thin-film pressure sensors, by splicing, F 上 and F 下The situation of change with distance constitutes a continuous curve, serving as the force change signal.

[0060] (2) When the force between the target permanent magnet material and the rectangular permanent magnet material is an attractive force:

[0061] Refer to Figure 6 , F is the repulsive force between the two. Since a one-dimensional single-point pressure sensor is used in this embodiment, only the vertical component of the force F1 = Fsinθ is considered. G is the gravity existing in the rectangular permanent magnet material 00 itself. F 上 is the pressure measured by the first thin-film pressure sensor 31, and F 下 is the pressure measured by the second thin-film pressure sensor 32.

[0062] From Figure 7 it can be known that F 上 is 0N from beginning to end. When the target permanent magnet material (the permanent magnet to be measured) reaches point A, F 下 = G, and F1 gradually increases from 0N. Subsequently, F 下 = G + F1. As it gets closer and closer to directly below the rectangular permanent magnet material, the change situation of F 下 is a gradually rising curve. When the target permanent magnet material reaches point B, when it is directly below the rectangular permanent magnet material, F 下 reaches the maximum value. Subsequently, F 下 gradually becomes smaller until the target permanent magnet material is at point C, F 下 = G.

[0063] Since F 上 is always 0N, only the curve of F 下 changing with distance needs to be considered. Let the section from F1 > 0 to F1 = 0 be a complete cycle, and use the data of this section of F 下 changing with distance as the force change signal.

[0064] Figure 8 is the change curve of the pressure values of the upper and lower two thin-film pressure sensors when the force between the target permanent magnet material and the fixed rectangular permanent magnet material is a repulsive force. Figure 9 is the change curve of the pressure values of the upper and lower two thin-film pressure sensors when the force between the target permanent magnet material and the fixed rectangular permanent magnet material is an attractive force. Among them, the abscissa is the distance between the target permanent magnet material and directly below the rectangular permanent magnet material. Both show the force change curves of the healthy condition, 20% demagnetization degree, 40% demagnetization degree, 60% demagnetization degree, and 80% demagnetization degree. It can be seen from the figure that whether in the case of attraction or repulsion, the force change curves of the target permanent magnet materials with different demagnetization degrees are different, providing a basis for distinguishing different demagnetization degrees.

[0065] 3. The computer obtains the force change signal and determines the demagnetization state of the target permanent magnet material based on the force change signal.

[0066] In this embodiment, S120 specifically includes: converting the force change signal into a two-dimensional rainbow image through rainbow view transformation; inputting the two-dimensional rainbow image into the trained DMA-RpViT demagnetization detection model, and predicting the demagnetization state of the target permanent magnet material through the DMA-RpViT demagnetization detection model.

[0067] After obtaining the force change signal of the target permanent magnet material, it is used as a one-dimensional signal to be processed. Then, the one-dimensional signal is converted into a two-dimensional image by using the signal processing method of rainbow view transformation. The specific conversion process is as follows:

[0068] First, referring to Figure 10 , the force change signal x of the target permanent magnet is transformed from Cartesian coordinates to polar coordinates, and the frequency and amplitude of the original signal are represented by a 2D polar symmetric pattern:

[0069]

[0070]

[0071] where x i is the amplitude of x at the i-th sampling point, that is, the corresponding F 上 or F 下 value at this point, τ is the time delay parameter, 1 ≤ τ ≤ 10, x i+τ represents the amplitude of the τ-th sampling point after the i-th sampling point; x max and x min represent the maximum amplitude and minimum amplitude of the force change signal x respectively; v is the gain angle of each part of the image, v < θ l , θ l is the reference starting angle of the l-th mirror symmetry plane; r(i) represents the polar radius, and θ(i) and φ(i) represent the rotation angles of the mirror symmetry plane in the clockwise and counterclockwise directions respectively.

[0072] The calculation formula of θ l is as follows:

[0073]

[0074] In the formula, m = 0, 1, 2,..., n - 1; n is the number of mirror symmetry planes, which is set to 6 in this embodiment. Therefore, the two parameters τ and v are very important and need to be set to appropriate values. In this embodiment, the normalized cross-correlation method is introduced to select appropriate parameters, and the signal can be better visualized through the above steps, as shown below:

[0075]

[0076] In the above formula, A and B are 2D matrices corresponding to two different images, with a size of m×n. A mn and B mn represent the gray values at the corresponding positions, and represent the average gray value, r(A, B) represents the prior similarity, and its value range is 0 to 1. The larger the value of r, the higher the similarity between images A and B. In this embodiment, by comparing the rainbow images in different demagnetization states, the parameters τ and v when r is the smallest, that is, when the similarity is the smallest, are selected as the optimal parameters.

[0077] In this embodiment, the signal processing method for rainbow view conversion adds different color information during the image mapping process to enhance local features. The detailed principle of the rainbow view conversion method is as follows:

[0078] 1. First, the mapping coordinates (α(i), β(i)) of the mirror symmetry plane in the clockwise or counterclockwise direction can be calculated based on above. The calculation method is as follows:

[0079]

[0080] In the formula, Round() represents the rounding function, and Ang represents θ(i) or The value of R is 100. When Ang represents θ(i), (α(i), β(i)) represents the mapping coordinates of the mirror symmetry plane in the clockwise direction; conversely, it represents the mapping coordinates in the counterclockwise direction.

[0081] 2. Calculate the amplitude Amp(i) in the clockwise or counterclockwise direction according to the mapping coordinates (α(i), β(i)) as follows:

[0082]

[0083] In the formula, (α(i), β(i)) represents the mapping coordinates of the mirror symmetry plane in the clockwise direction.

[0084] 3. To visualize the signal amplitude change, a rainbow color mapping function is adopted. Determine the specific color value according to the normalized amplitude value. The color mapping process is as follows:

[0085]

[0086] Among them, Rainbow() represents the color mapping function, Amp max and Amp minRefers to the maximum and minimum amplitudes of the color mapping function. The rainbow color mapping follows its preset color gradient rule and assigns different colors to different input values. Therefore, the rainbow image can produce different color changes corresponding to the amplitude changes.

[0087] Refer to Figure 11 , which shows the detailed comparison diagram of the rainbow images converted from the force change signals of two thin-film pressure sensors under five different demagnetization states (non-demagnetized, 20% demagnetized, 40% demagnetized, 60% demagnetized, 80% demagnetized) of the target permanent magnet material. It can be clearly seen from the figure that there are obvious differences in the corresponding rainbow images under different demagnetization states, thus providing a basis for the identification of different demagnetization states.

[0088] As above, it is a specific description of the rainbow view conversion. The obtained two-dimensional image is input into the trained DMA-RpViT demagnetization detection model, and the demagnetization state of the target permanent magnet material can be predicted through the DMA-RpViT demagnetization detection model.

[0089] Among them, the DMA-RpViT demagnetization detection model needs to be pre-trained. Specifically, the two-dimensional rainbow images converted from the force change signals corresponding to the same demagnetization state are used as homogeneous samples. The rainbow images corresponding to the permanent magnet materials with a demagnetization degree of 1-99% are used to form a sample library to train the DMA-RpViT demagnetization detection model.

[0090] It should be noted that since it is difficult to customize permanent magnet materials with demagnetization faults, the healthy permanent magnet materials can be heated at different temperatures by using a temperature-controlled ceramic chip to obtain permanent magnet materials with different demagnetization degrees. The temperature of the permanent magnet material is measured by an infrared thermometer, and the magnetic flux density is quantitatively analyzed by a gaussmeter to obtain the demagnetization degree. Then, the permanent magnet materials with a demagnetization degree from 1% to 100% are respectively arranged in the form of N-pole up and S-pole up, and a sample library composed of rich samples with different demagnetization degrees can be obtained through the permanent magnet material demagnetization detection device in this embodiment. This sample is used to train the DMA-RpViT demagnetization detection algorithm.

[0091] It should also be noted that converting the force change signal into a two-dimensional rainbow diagram as the DMA-RpViT demagnetization detection model is an optimal means. As introduced above, the force change signals corresponding to permanent magnetic materials under different demagnetization degrees are also different. Therefore, in other embodiments, the force change signal can also be directly used as the input of the DMA-RpViT demagnetization detection model. In the corresponding embodiment, S120 specifically includes: inputting the force change signal into the trained DMA-RpViT demagnetization detection model, and predicting the demagnetization state of the target permanent magnetic material through the DMA-RpViT demagnetization detection model. Correspondingly, the training samples of the DMA-RpViT demagnetization detection model are the force change signals corresponding to permanent magnetic materials with a demagnetization degree of 1-99%.

[0092] Referring to Figure 12 , in this embodiment, the DMA-RpViT demagnetization detection model includes an input layer, an intermediate layer (composed of feature extraction stage 1 to feature extraction stage 4), and an output layer (composed of a pooling layer and a linear layer) connected in sequence; connected in sequence means that according to the connection order, the output of the previous network layer is the input of the next network layer. Specifically, the input of the DMA-RpViT demagnetization detection model is the input of the input layer, the output of the input layer is the input of the intermediate layer, the output of the intermediate layer is the input of the output layer, and the output of the output layer is the output of the DMA-RpViT demagnetization detection model.

[0093] Referring to Figure 13 , the input layer is used to perform convolution and pooling on the input of the DMA-RpViT demagnetization detection model, and it can specifically include a 3×3 convolution, an activation layer, and a 3×3 convolution connected in sequence. The intermediate layer extracts features from the output of the input layer, and the output layer performs pooling and mapping on the output of the intermediate layer to obtain the demagnetization state of the target permanent magnetic material. The intermediate layer is divided into four feature extraction stages connected in sequence, and adjacent two feature extraction stages are connected by a downsampling layer. Each feature extraction stage is composed of at least one SEVT module and at least one OEVT module connected alternately. Among them, the downsampling layer can specifically include an OEVT module, a 3×3 depth convolution, a 1×1 convolution, and a feedforward neural network layer (FNN) connected in sequence. In the first, second, and fourth feature extraction stages, both the SEVT module and the OEVT module are one; in the third feature extraction stage, both the SEVT module and the OEVT module are seven.

[0094] Referring to Figure 14 , the SEVT module includes a first 3×3 depth convolution, a DMA module, and a first feedforward neural network connected in sequence, and the input and output of the first 3×3 depth convolution are connected with residuals. The OEVT module includes a second 3×3 depth convolution, an SE (squeeze-and-excitation) module, and a second feedforward neural network connected in sequence, and the input and output of the second 3×3 depth convolution are connected with residuals.

[0095] The overall data flow of the DMA-RpViT demagnetization detection model is as follows:

[0096] The input layer takes the input X of the DMA-RpViT demagnetization detection model m (a two-dimensional rainbow diagram in this embodiment) and performs convolution and pooling operations to extract basic features and obtain the intermediate feature map Z1.

[0097] The first feature extraction stage performs convolution operations on Z1 to further extract features and obtain the intermediate feature map Z2.

[0098] The first downsampling layer downsamples Z2 to reduce the size of the feature map and increase the number of channels simultaneously to obtain the intermediate feature map Z3.

[0099] The second feature extraction stage performs convolution operations on Z3 to further extract features and obtain the intermediate feature map Z4.

[0100] The second downsampling layer downsamples Z4 to reduce the size of the feature map and increase the number of channels simultaneously to obtain the intermediate feature map Z5.

[0101] The third feature extraction stage performs convolution operations on Z5 to further extract features and obtain the intermediate feature map Z6.

[0102] The third downsampling layer downsamples Z6 to reduce the size of the feature map and increase the number of channels simultaneously to obtain the intermediate feature map Z7.

[0103] The fourth feature extraction stage performs convolution operations on Z7 to further extract features and obtain the intermediate feature map Z8.

[0104] The pooling layer in the output layer performs global pooling operations on the feature map of Z8 to convert the feature map into a fixed-length vector Z9.

[0105] The linear layer in the output layer further maps Z9 to the final regression target value and outputs a continuous numerical value Z10, which is used to represent the result of the regression prediction, that is, the demagnetization degree of the target permanent magnetic material.

[0106] Among them, the specifications of Z1 to Z2 are all (H / 4, W / 4, 48); the specifications of Z3 to Z4 are (H / 8, W / 8, 96); the specifications of Z5 to Z6 are (H / 16, W / 16, 192); the specifications of Z7 to Z8 are (H / 32, W / 32, 384); Z9 is a feature vector with a dimension of 1152; Z10 is a vector with a dimension of 1.

[0107] Furthermore, a new DMA module is provided in this embodiment. Refer to Figure 15, the feature processing steps of the DMA module include: dividing the input feature map of the DMA module into three groups; performing 1×1 convolution on the first group of input feature maps to obtain a first feature map, performing average pooling on the first feature map along the X direction and the Y direction respectively, concatenating the two average pooling results along the Z direction and then performing 1×1 convolution to obtain a second feature map, and weighting the three groups of input feature maps based on the activation result of the second feature map; performing 3×3 depthwise separable convolution on the second group of input feature maps to obtain a third feature map, performing 5×5 dilated convolution on the second group of input feature maps to obtain a fourth feature map, and weighted summing the activation results of the third feature map and the fourth feature map to obtain a fifth feature map; sequentially performing group normalization and average pooling on the weighted three groups of input feature maps to obtain a sixth feature map, and performing average pooling on the fifth feature map to obtain a seventh feature map; performing matrix dot product operation on the activation result of the sixth feature map and the fifth feature map to obtain an eighth feature map, and performing matrix dot product operation on the activation result of the seventh feature map and the group normalization result of the three groups of input feature maps to obtain a ninth feature map; weighting the three groups of input feature maps through the activation result of the addition result of the eighth feature map and the ninth feature map to obtain the output feature map of the DMA module.

[0108] The above feature processing steps of the DMA module are described in detail through an example as follows.

[0109] 1. Dynamic multi-scale fusion: Divide the input feature map of size C×H×W into G groups, with each group having a shape of C / G×H×W. Different operations are performed on each group of feature maps respectively.

[0110] (1) For one group of input feature maps, capture local features through 1×1 conventional convolution, and output a feature map of size C / G×H×W (the first feature map). Then, perform average pooling along the X direction (XAvg Pool) to obtain a feature map with a shape of C / G×1×W, and perform average pooling along the Y direction (YAvg Pool) to obtain a feature map with a shape of C / G×H×1. Then, concatenate the results of pooling along the X direction and pooling along the Y direction along the image height direction, and pass through convolution Conv(1×1) to obtain a feature map with a shape of C / G×1×1 (the second feature map). Finally, use two non-linear Sigmoid functions to fit the 2D binary distribution of the linear convolution, and re-weight (Re-weight) the original each group of input feature maps, so as to achieve cross-channel feature interaction.

[0111] Among them, the formulas for global average pooling along the horizontal and vertical directions are:

[0112]

[0113] In the formula, x c(H, i) refers to the input feature at the c-th channel, height h, and width i. x c (j, W) refers to the input feature at the c-th channel, height j, and width w.

[0114] 2. Perform 3×3 depthwise separable convolution on one group of input feature maps to capture deep features, and output a feature map of size C / G×H×W (the third feature map). Then perform 5×5 dilated convolution on the other group of input feature maps, which can expand the receptive field to obtain more context information, and output a feature map of size C / G×H×W (the fourth feature map). Then use the Softmax activation function to perform weight normalization operations respectively, and then perform feature map fusion through weighted summation to obtain the fifth feature map, thus realizing feature fusion at different scales.

[0115] Among them, the formula for extracting deep features F local is:

[0116] F local = DWConv 3×3 (X)

[0117] In the formula, DWConv 3×3 is depthwise separable convolution, which is decomposed into 3×3 channel-wise convolution and 1×1 pointwise convolution.

[0118] Among them, the formula for extracting context features F mid is:

[0119] F mid = DilatedConv 5×5 (X)

[0120] In the formula, DilatedConv 5×5 is dilated convolution, with the dilation rate set to 2 and the equivalent receptive field being 9×9.

[0121] 2. Cross-space learning part: It consists of two parallel branches. Perform GroupNorm on each group of input feature maps after reweighting. Then perform global average pooling (Avg Pool) on the two branches respectively to obtain feature maps of shape C / G×1×1 (the sixth and seventh feature maps respectively). Then the two branches respectively use the natural non-linear function Softmax of 2D Gaussian mapping to fit the linear transformation (obtaining the activation results of the sixth and seventh feature maps respectively). Finally, realize cross-space learning by multiplying the outputs after the previous step with matrix dot product operations respectively (that is: perform matrix dot product operation on the activation result of the sixth feature map and the fifth feature map to obtain the eighth feature map, and perform matrix dot product operation on the activation result of the seventh feature map and the group normalization result of the three groups of input feature maps to obtain the ninth feature map).

[0122] Among them, the formula for the global average pooling operation is:

[0123]

[0124] In the formula, x c (i,j) refers to the input feature at the c-th channel, with height i and width j.

[0125] 3. Add the cross-space learning results of the two parallel branches (add the eighth feature map and the ninth feature map), and then perform Sigmoid activation and re-weighting (Re-weight). Finally, an output feature map with the shape of C×H×W is obtained.

[0126] As can be seen from the above embodiments, the method for detecting the demagnetization of the permanent magnet material first obtains the force change signal of the target permanent magnet material through the device for detecting the demagnetization of the permanent magnet material, and then judges the demagnetization state of the target permanent magnet material according to the force change signal. Compared with the method of detecting the demagnetization of the permanent magnet material by using a Hall probe to detect the magnetic field intensity on the surface of the permanent magnet material, the method in this embodiment is not affected by manual operation. Compared with the method of evaluating the health state of the permanent magnet material by using a camera to photograph cracks, depressions, etc. on the surface of the material, since the relationship between the force change signal and the demagnetization degree is relatively clear, different demagnetization degrees correspond to different force change signals, so the method in this embodiment has higher detection accuracy and can judge the specific demagnetization degree. In summary, the method for detecting the demagnetization of the permanent magnet material in this embodiment solves the problem of low detection accuracy of the current method for detecting the demagnetization of the permanent magnet material.

[0127] Moreover, the method for detecting the demagnetization of the permanent magnet material uses a DMA-RpViT demagnetization detection model with a new architecture to identify the force change signal. Compared with the conventional deep learning model, the DMA-RpViT demagnetization detection model with this new architecture is more suitable for identifying the force change signal and has higher identification accuracy, thereby being able to further improve the detection accuracy of the demagnetization of the permanent magnet material.

[0128] In this embodiment, a device for detecting the demagnetization of the permanent magnet material is also provided. This device is used to implement the method for detecting the demagnetization of the permanent magnet material provided in this embodiment, and those that have been described will not be repeated. The following terms "module", "unit", "sub-unit", etc. can be a combination of software and / or hardware that can achieve a predetermined function. Although the device described in the following embodiments is preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0129] The device for detecting the demagnetization of the permanent magnet material provided in this embodiment includes a signal acquisition module and a demagnetization detection module.

[0130] The signal acquisition module is used to acquire the force change signal of the target permanent magnet material from the device for detecting the demagnetization of the permanent magnet material.

[0131] The demagnetization detection module is used to judge the demagnetization state of the target permanent magnet material according to the force change signal.

[0132] Among them, the device for detecting the demagnetization of the permanent magnet material includes a transmission device, a fixing frame, and a magnetic force signal acquisition device; the transmission device is used to move the target permanent magnet material; the fixing frame is fixedly installed directly above the transmission path of the transmission device; the magnetic force signal acquisition device includes a rectangular permanent magnet material, a first thin film pressure sensor, and a second thin film pressure sensor. The first thin film pressure sensor and the second thin film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnet material and their vertical projections overlap. The fixing frame fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin film pressure sensor and the lower surface of the second thin film pressure sensor; during the process of the transmission device moving the target permanent magnet material, the first thin film pressure sensor and the second thin film pressure sensor provide the force change signal.

[0133] It should be noted that the above-mentioned each module can be a functional module or a program module, and can be implemented either by software or by hardware. For the modules implemented by hardware, the above-mentioned each module can be located in the same processor; or the above-mentioned each module can also be located in different processors in any combined form.

[0134] In this embodiment, a computer is also provided, which includes a memory and a processor. A computer program is stored in the memory, and the processor is configured to run the computer program to execute the method for detecting the demagnetization of the permanent magnet material provided in this embodiment.

[0135] In this embodiment, a system for detecting the demagnetization of the permanent magnet material is also provided, which includes: the device for detecting the demagnetization of the permanent magnet material and the computer provided in this embodiment.

[0136] The device for detecting the demagnetization of the permanent magnet material includes a transmission device, a fixing frame, and a magnetic force signal acquisition device; the transmission device is used to move the target permanent magnet material; the fixing frame is fixedly installed directly above the transmission path of the transmission device; the magnetic force signal acquisition device includes a rectangular permanent magnet material, a first thin film pressure sensor, and a second thin film pressure sensor. The first thin film pressure sensor and the second thin film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnet material and their vertical projections overlap. The fixing frame fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin film pressure sensor and the lower surface of the second thin film pressure sensor; during the process of the transmission device moving the target permanent magnet material, the first thin film pressure sensor and the second thin film pressure sensor provide the force change signal to the computer.

[0137] It should be understood that the specific embodiments described herein are for purposes of explaining the application and not for limiting it. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided in this application without creative efforts fall within the scope of protection of this application.

[0138] Obviously, the accompanying drawings are only some examples or embodiments of this application. For those of ordinary skill in the art, this application can also be applied to other similar situations based on these drawings without creative efforts. Additionally, it can be understood that although the work done during this development process may be complex and time-consuming, for those of ordinary skill in the art, certain design, manufacturing, or production changes based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient disclosure of this application.

Claims

1. A method for detecting demagnetization of a permanent magnetic material, characterized in that, Including: Obtaining a force change signal regarding a target permanent magnet material from a device for detecting demagnetization of a permanent magnet material; Judging the demagnetization state of the target permanent magnet material according to the force change signal; Wherein, the device for detecting demagnetization of the permanent magnet material includes a transmission device, a fixing bracket, and a magnetic force signal acquisition device; the transmission device is used for moving the target permanent magnet material; the fixing bracket is fixedly installed directly above the transmission path of the transmission device; the magnetic force signal acquisition device includes a rectangular permanent magnet material, a first thin-film pressure sensor, and a second thin-film pressure sensor, the first thin-film pressure sensor and the second thin-film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnet material and their vertical projections overlap, and the fixing bracket fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin-film pressure sensor and the lower surface of the second thin-film pressure sensor; During the process that the transmission device moves the target permanent magnet material, the first thin-film pressure sensor and the second thin-film pressure sensor provide the force change signal.

2. The method for detecting demagnetization of a permanent magnet material according to claim 1, wherein Judging the demagnetization state of the target permanent magnet material according to the force change signal includes: Converting the force change signal into a two-dimensional rainbow map through rainbow view conversion; Inputting the two-dimensional rainbow map into a trained DMA-RpViT demagnetization detection model, and predicting the demagnetization state of the target permanent magnet material through the DMA-RpViT demagnetization detection model.

3. The method for detecting demagnetization of the permanent magnet material according to claim 2, wherein, The parameters in the rainbow view conversion are determined by the normalized cross-correlation method.

4. The method for detecting demagnetization of a permanent magnet material according to claim 2, wherein, The DMA-RpViT demagnetization detection model includes an input layer, an intermediate layer, and an output layer connected in sequence; The input layer is used for performing convolution and pooling on the input of the DMA-RpViT demagnetization detection model, the intermediate layer extracts features from the output of the input layer, and the output layer performs pooling and mapping on the output of the intermediate layer to obtain the demagnetization state of the target permanent magnet material.

5. The method for detecting demagnetization of a permanent magnet material according to claim 4, wherein, The intermediate layer is divided into four feature extraction stages connected in sequence, and adjacent two feature extraction stages are connected by a downsampling layer, and each feature extraction stage is composed of at least one SEVT module and at least one OEVT module connected alternately; The SEVT module includes a first 3×3 depth convolution, a DMA module, and a first feedforward neural network connected in sequence, and the input and output of the first 3×3 depth convolution are connected with residuals; The OEVT module includes a second 3×3 depth convolution, an SE module, and a second feedforward neural network connected in sequence, and the input and output of the second 3×3 depth convolution are connected with residuals.

6. The method for detecting demagnetization of a permanent magnet material according to claim 5, characterized in that, The feature processing steps of the DMA module include: Dividing the input feature map of the DMA module into three groups; Performing 1×1 convolution on the first group of the input feature maps to obtain a first feature map, performing average pooling on the first feature map along the X direction and the Y direction respectively, splicing the two average pooling results along the Z direction and then performing 1×1 convolution to obtain a second feature map, and weighting the three groups of the input feature maps based on the activation result of the second feature map; Perform 3×3 depthwise separable convolution on the second group of the input feature maps to obtain a third feature map, perform 5×5 dilated convolution on the second group of the input feature maps to obtain a fourth feature map, and perform weighted summation on the activation results of the third feature map and the fourth feature map to obtain a fifth feature map; Perform group normalization and average pooling on the three groups of weighted input feature maps in sequence to obtain a sixth feature map, and perform average pooling on the fifth feature map to obtain a seventh feature map; Perform matrix dot product operation on the activation result of the sixth feature map and the fifth feature map to obtain an eighth feature map, and perform matrix dot product operation on the activation result of the seventh feature map and the group normalization results of the three groups of input feature maps to obtain a ninth feature map; Perform weighting on the three groups of input feature maps through the activation result of the addition result of the eighth feature map and the ninth feature map to obtain the output feature map of the DMA module.

7. The method for detecting demagnetization of a permanent magnet material according to claim 5, characterized in that, In the first, second, and fourth feature extraction stages, both the SEVT module and the OEVT module are one; in the third feature extraction stage, both the SEVT module and the OEVT module are seven.

8. A device for detecting demagnetization of a permanent magnet material, characterized in that, Comprising: A signal acquisition module, configured to acquire a force change signal regarding the target permanent magnet material from a device for detecting demagnetization of a permanent magnet material; A demagnetization detection module, configured to judge the demagnetization state of the target permanent magnet material according to the force change signal; Wherein, the device for detecting demagnetization of a permanent magnet material includes a transmission device, a fixing bracket, and a magnetic force signal acquisition device; the transmission device is used to move the target permanent magnet material; the fixing bracket is fixedly installed directly above the transmission path of the transmission device; the magnetic force signal acquisition device includes a rectangular permanent magnet material, a first thin-film pressure sensor, and a second thin-film pressure sensor, the first thin-film pressure sensor and the second thin-film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnet material and their vertical projections overlap, and the fixing bracket fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin-film pressure sensor and the lower surface of the second thin-film pressure sensor; During the process of the transmission device moving the target permanent magnet material, the first thin-film pressure sensor and the second thin-film pressure sensor provide the force change signal.

9. A computer, comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to execute the method for detecting demagnetization of a permanent magnet material according to any one of claims 1 to 7.

10. A system for detecting demagnetization of a permanent magnet material, characterized in that, Comprising: A device for detecting demagnetization of a permanent magnet material and the computer according to claim 9; The device for detecting demagnetization of a permanent magnet material includes a transmission device, a fixing bracket, and a magnetic force signal acquisition device; The transmission device is used to move the target permanent magnetic material; the fixing frame is fixedly installed directly above the transmission path of the transmission device; the magnetic force signal acquisition device includes a rectangular permanent magnetic material, a first thin-film pressure sensor, and a second thin-film pressure sensor. The first thin-film pressure sensor and the second thin-film pressure sensor are respectively attached to the upper and lower surfaces of the rectangular permanent magnetic material and their vertical projections overlap. The fixing frame fixes the magnetic force signal acquisition device by contacting the upper surface of the first thin-film pressure sensor and the lower surface of the second thin-film pressure sensor; During the process of the transmission device moving the target permanent magnetic material, the first thin-film pressure sensor and the second thin-film pressure sensor provide a force change signal to the computer.

Images