A method for realizing ultrasonic phased array sparse imaging of rail defects

Abstract

The application discloses a kind of methods for realizing steel rail defect ultrasonic phased array sparse imaging, comprising the following steps: S1, make inspection car travel to the steel rail line section needing to carry out defect detection;S2, with the movement of inspection car, ultrasonic phased array sensor is controlled to steel rail by ultrasonic signal excitation source and emits ultrasonic wave, and then ultrasonic echo signal transmission is transmitted to signal analysis device;S3, signal analysis device adopts DSMA algorithm to carry out sparse optimization processing to the receiving element position of ultrasonic phased array sensor, and carries out sparse imaging on this basis, to realize the visual representation of steel rail defect.The application can carry out non-contact online detection to steel rail defect, and considers detection precision and detection efficiency, can provide theoretical basis and practical guidance for steel rail safe service, early warning, timely maintenance.

Description

Technical Field

[0001] This invention relates to a method for realizing ultrasonic phased array sparse imaging of rail defects, belonging to the field of rail defect detection technology. Background Technology

[0002] Currently, rail flaw detection is mainly achieved using ultrasonic rail flaw detection vehicles. The main principle is that due to the different acoustic impedances between defects and homogeneous materials, an interface of different media is formed. The emitted ultrasonic waves are reflected upon encountering this interface, and the characteristics of the received reflected waves are analyzed to determine the location and nature of the defect. However, ultrasonic rail flaw detection vehicles have limited detection capabilities, only able to detect fatigue and welding defects within the rail head and web area, such as scratches, rail head crushing, and wavy wear. Furthermore, the detection results from these vehicles require interpretation by experienced inspectors, making it difficult to achieve quantitative characterization of rail damage and increasing the likelihood of missed detections. Ultrasonic phased arrays, on the other hand, consist of an array of multiple independent piezoelectric crystals. Each crystal unit can be excited according to certain rules and timing using an electronic system, thereby adjusting the position and direction of the focused sound beam. Therefore, constructing a vehicle-mounted ultrasonic phased array detection technology solution can fully utilize the advantages of automatic focusing and deflection of the ultrasonic beam, laying a theoretical foundation for rapid and accurate online detection of rail defects.

[0003] However, traditional ultrasound imaging uses a full-focusing imaging algorithm, which, due to the need to process a large amount of full-matrix data, suffers from significant deficiencies in real-time imaging. With the formation and development of my country's rail transit network, the rail transit industry has entered a stage where construction, operation, and maintenance are equally important. How to scientifically maintain such a large-scale operational network, ensure the stability and reliability of infrastructure, and thus enable the long-term safe operation of rail transit is a problem that must be solved in the current stage of rail transit development. Summary of the Invention

[0004] In view of the above-mentioned problems and needs of the existing technology, the purpose of this invention is to provide a method for realizing ultrasonic phased array sparse imaging of rail defects.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for achieving sparse ultrasonic phased array imaging of rail defects includes the following steps:

[0007] S1. The inspection vehicle is driven to the rail section where defect detection is required. The inspection vehicle is equipped with a vehicle bogie at the bottom. There is a side beam on each side of the vehicle bogie. The bottom of the side beam is equipped with a telescopic fixing frame that can extend and retract in the vertical direction. An ultrasonic phased array sensor is installed at the bottom of the telescopic fixing frame. The transmitting end of the ultrasonic phased array sensor is connected to the ultrasonic signal excitation source, and the receiving end of the ultrasonic phased array sensor is connected to the signal analysis device.

[0008] S2. As the inspection vehicle moves, the ultrasonic phased array sensor is controlled by the ultrasonic signal excitation source to emit ultrasonic waves toward the rail and receive the ultrasonic echoes reflected back from inside the rail. Then, the ultrasonic echo signals are transmitted to the signal analysis device.

[0009] S3. The signal analysis device uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor, and performs sparse imaging based on this, thereby realizing the visual characterization of rail defects. Specifically:

[0010] S31. The signal analysis device optimizes the SMA algorithm to obtain the DSMA algorithm, namely: First, the maximum number of iterations of the DSMA algorithm is set; second, the slime mold position is encoded with real numbers and discretized; then, the slime mold position dimension-specific formula is updated; then, a suitable fitness function is constructed to update the position of the receiving array element; finally, the algorithm iterative calculation process is executed to select the optimal receiving array element position.

[0011] S32. The signal analysis device uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor, and then performs sparse imaging based on this.

[0012] One implementation scheme, the specific operation of step S31 is as follows:

[0013] S311. Set the maximum number of iterations for the DSMA algorithm:

[0014] The maximum number of iterations for the DSMA algorithm is set to max = 500. The iteration count t is automatically incremented by one after each iteration. When the iteration count t reaches max, the iteration calculation process ends and the optimization result is output.

[0015] S312. Encode the location of slime molds with real numbers:

[0016] The positions of slime molds are encoded using real-number encoding, where d represents the element position and L represents the aperture length of the ultrasonic phased array sensor. Taking a 32-element linear array as an example, the sparsity is set to 0.5 to satisfy the constraint: st.d1=0, d N =L, the dimension of the solution space = 32 * 0.5 - 2 = 14, the location of the slime mold is encoded as:

[0017] γ=[γ1,γ2,…,γ dim ],γ i ∈Z,0<γ i ≤N (1);

[0018] In equation (1): dim is the dimension of the solution space, γ represents the slime mold position encoding, N represents the number of array elements, and Z represents the set of integers;

[0019] Setting d c Let the element spacing be denoted by the following formula:

[0020] d = [d1, d2, ..., d N-1 ,d N ] T ={[γ1,γ2,…,γ dim ] T ×d c}∪{[d1,d N ] T} (2);

[0021] In equation (2): d1, d2, ..., d N The position of the matrix element is indicated by T, which represents the transpose of the matrix.

[0022] S313. Discretize the location of slime mold:

[0023] The position of the slime mold in the solution space during the initialization of the standard SMA algorithm is:

[0024] X 0 = rand·(UB-LB)+LB (3);

[0025] In equation (3): UB and LB are the upper and lower bounds of the solution space, respectively, and rand is a random number between 0 and 1;

[0026] To satisfy the constraint: st.i∈Z,1≤i≤N-1, the positions of slime molds in the solution space are discretized according to formula (4):

[0027] X t =X t-1 *η t (4);

[0028] In the formula η t Let X represent the discrete operator used in the t-th iteration calculation. t This represents the discrete location of the slime mold in the t-th iteration;

[0029] S314. Update the slime mold location dimension-specific formula:

[0030] To address the issue of inconsistencies in the searchable regions across different dimensions of the solution space in the sparse optimization model of ultrasonic arrays, the formula for calculating the location of slime molds in the solution space is improved as follows:

[0031]

[0032] In equation (5): L dim = N - dim + 1, where dim represents the dimension of the solution space; This represents the margin adjustment rate, which ranges from [-a, a], where a = arctanh[1-t / (max-t)], and max is the maximum number of iterations set. The deceleration rate is linearly decreasing from 1 to 0; t represents the current iteration number. This indicates the optimal position found in the current iteration. Indicates the current location of the slime mold; This indicates the locations of two randomly selected slime molds. Represents the weight of the slime mold; r represents a random value in the interval [0,1]; p = tanh|S(i) - DF|, i∈1,2,…,n, where S(i) represents The fitness of DF represents the optimal fitness across all iterations;

[0033] S315. Construct a suitable fitness function:

[0034] fitness = {0.8 × (PML / PSL)} 2 +0.2×(MLW full -MLW) 2} (6);

[0035] In equation (6): fitness represents the fitness function, PSL represents the sidelobe peak value, PML represents the main lobe peak value, MLW represents the main lobe width, and MLW represents the sidelobe peak value. full Indicates the maximum main lobe width;

[0036] S316. Execute the algorithm iterative calculation process:

[0037] Determine whether the current number of iterations of the DSMA algorithm has reached the maximum number of iterations. If not, continue to execute steps S313 to S315. If the current number of iterations of the DSMA algorithm has reached the maximum number of iterations, terminate the iterative calculation process and output the optimal receiver array element position.

[0038] One implementation scheme, the specific operation of step S32 is as follows:

[0039] After optimizing the SMA algorithm to obtain the DSMA algorithm, the signal analysis device uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor to obtain the optimal sparse positions. The sparse imaging formula is as follows:

[0040]

[0041]

[0042] In the above formula:

[0043] I(x,z) is the pixel value at any point Q inside the measured medium, and the coordinates of point Q are (x,z).

[0044] i represents the label of the transmitting element, and j represents the label of the receiving element.

[0045] N0 is the number of array elements in the ultrasonic phased array sensor before sparsity, and M0 is the number of array elements in the ultrasonic phased array sensor after sparsity.

[0046] T ij (x,z) is the travel time of the sound wave, S ij [T ij [x,z] is the amplitude of the ultrasonic echo signal at point Q corresponding to all transmitting and receiving array elements;

[0047] d(x,z) is the sum of the distances from the transmitting and receiving elements to point Q; c is the speed of sound in the medium.

[0048] (x i ,z i (x) represents the coordinates of the transmitting element labeled i. j ,z j ) are the coordinates of the receiving array element labeled j.

[0049] In one embodiment, the bottom of the side beam is provided with a slide rail, and a slider adapted to it is movably mounted on the slide rail, the slider being connected to the top of the telescopic fixing frame.

[0050] In a preferred embodiment, each slider is connected to two telescopic fixing frames, and a stabilizing rod that can extend and retract in the vertical direction is provided between the frames of the two telescopic fixing frames. The top of the stabilizing rod is connected to the slider, and the bottom of the stabilizing rod is connected to the ultrasonic phased array sensor.

[0051] In one embodiment, the slider is equipped with a horizontal stepper motor and a vertical stepper motor inside, and both stepper motors are connected to a signal analysis device for signal control of their movement.

[0052] In one embodiment, the ultrasonic phased array sensor is an array composed of multiple air-coupled ultrasonic sensors arranged at equal intervals.

[0053] In one embodiment, a laser scanner is provided on the side of the ultrasonic phased array sensor, and the laser scanner is connected to a signal analysis device.

[0054] In one embodiment, the signal analysis device is signal-connected to a remote controller.

[0055] In one embodiment, the signal analysis device is a PC.

[0056] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0057] The method for ultrasonic phased array sparse imaging of rail defects provided by this invention can achieve non-contact online detection of rail defects, thereby enabling visual characterization of rail defects. It can also balance imaging efficiency and imaging accuracy, and can provide theoretical basis and practical guidance for safe rail service, early warning and timely maintenance. Therefore, this invention has significant progress and application value compared with the prior art. Attached Figure Description

[0058] Figure 1 This is a front view of the device corresponding to the method for realizing ultrasonic phased array sparse imaging of rail defects described in this invention;

[0059] Figure 2 yes Figure 1 A schematic diagram showing the device positioned above the rail;

[0060] Figure 3 yes Figure 1 A partial enlarged view of the device shown;

[0061] Figure 4 This is the flowchart corresponding to the sparse imaging described in this invention;

[0062] The following labels are used to indicate the components in the diagram: 1. Vehicle bogie; 1-1. Side beam of vehicle bogie; 2. Telescopic fixing frame; 3. Ultrasonic phased array sensor; 4. Ultrasonic signal excitation source; 5. Signal analysis device; 6. Rail; 7. Slide rail; 8. Slider; 9. Stabilizer bar; 10. Laser scanner; 11. Remote control. Detailed Implementation

[0063] The technical solution of the present invention will be further described clearly and completely below with reference to the accompanying drawings and embodiments.

[0064] Example

[0065] Figures 1 to 3The diagram shows the apparatus corresponding to the method for realizing ultrasonic phased array sparse imaging of rail defects according to the present invention. It includes a vehicle bogie 1, with a side beam 1-1 on each of the left and right sides of the vehicle bogie 1. The bottom of the side beam 1-1 is provided with a telescopic fixing frame 2 that can extend and retract in the vertical direction. An ultrasonic phased array sensor 3 is installed at the bottom of the telescopic fixing frame 2. The transmitting end of the ultrasonic phased array sensor 3 is connected to the ultrasonic signal excitation source 4, and the receiving end of the ultrasonic phased array sensor 3 is connected to the signal analysis device 5.

[0066] In this embodiment, the vehicle bogie 1 can be a commercially available product, compatible with the inspection vehicle, and can move synchronously with the inspection vehicle. The vehicle bogie 1 provides excellent guidance for the operation of the inspection vehicle. During installation, the vehicle bogie 1 is mounted on the body of the inspection vehicle, thus mounting the entire detection device on the inspection vehicle, making the entire device vehicle-mounted, thereby realizing the function of detection while in motion. The inspection vehicle in this embodiment can use existing technology; any vehicle that can normally travel on the rails 6 can be used, or it can be a train.

[0067] In this embodiment, the telescopic fixing frame 2 can be a commercially available product. The telescopic fixing frame 2 is used to adjust the distance between the ultrasonic phased array sensor 3 and the surface of the rail 6 to be tested. As long as it can automatically extend and retract in the vertical direction, it is acceptable.

[0068] In this embodiment, the ultrasonic phased array sensor 3, the ultrasonic signal excitation source 4, and the signal analysis device 5 can all be commercially available products. The ultrasonic phased array sensor 3 refers to an array composed of multiple air-coupled ultrasonic sensors arranged at equal intervals. The ultrasonic phased array sensor 3 is controlled by the ultrasonic signal excitation source 4 to emit ultrasonic waves toward the rail 6 and receive the ultrasonic echoes reflected back from inside the rail 6. Then, the ultrasonic echo signals are transmitted to the signal analysis device 5. When defects appear on the surface or inside the rail 6, the characteristics of the ultrasonic echo signals will change significantly. By analyzing and processing the ultrasonic echo signals through the signal analysis device 5, automatic detection of rail defects can be achieved.

[0069] During installation, the ultrasonic phased array sensor 3 can first be placed in a fixing device made of carbon fiber plate, with polypropylene material used to shield the surrounding area. Then, it is fixed together with the fixing device to the bottom of the telescopic fixing frame 2 to effectively prevent the ultrasonic phased array sensor 3 from being damaged by other hard objects during operation. The ultrasonic signal excitation source 4 and the signal analysis device 5 can be installed directly inside the inspection vehicle's cargo compartment instead of on the vehicle bogie 1.

[0070] In this embodiment, the bottom of the side beam 1-1 is provided with a slide rail 7, and a slider 8 adapted to it is movably mounted on the slide rail 7. The slider 8 is connected to the top of the telescopic fixing frame 2. The slider 8 moves horizontally along the slide rail 7, which causes the telescopic fixing frame 2 to move horizontally relative to the slide rail 7, thereby driving the ultrasonic phased array sensor 3 at the bottom of the telescopic fixing frame 2 to move horizontally, thereby adjusting the ultrasonic phased array sensor 3 to align with the detection area of ​​the rail 6. Furthermore, the slider 8 is internally equipped with a horizontal stepper motor and a vertical stepper motor (existing technology, omitted in the figure). Both stepper motors are connected to the signal analysis device 5 and operate under its control. When the signal analysis device 5 controls the horizontal stepper motor, the slider 8 moves horizontally along the slide rail 7, causing the telescopic fixing frame 2 to move horizontally relative to the slide rail 7. When the signal analysis device 5 controls the vertical stepper motor, the slider 8 transmits the force to the telescopic fixing frame 2, causing the telescopic fixing frame 2 to extend and retract vertically under the force, adjusting the distance between the ultrasonic phased array sensor 3 and the surface of the rail 6 to be tested. Since this part is prior art, it will not be described in detail here.

[0071] In this embodiment, each slider 8 is connected to two telescopic fixing frames 2. A stabilizing rod 9 that can extend and retract in the vertical direction is provided between the frames of the two telescopic fixing frames 2. The top of the stabilizing rod 9 is connected to the slider 8, and the bottom of the stabilizing rod 9 is connected to the ultrasonic phased array sensor 3. The movement trajectory of the stabilizing rod 9 is consistent with that of the telescopic fixing frame 2, and it extends and retracts with the telescopic fixing frame 2. It can fix the ultrasonic phased array sensor 3 to prevent the ultrasonic signal emitted by the ultrasonic phased array sensor 3 from being deflected when the train is moving and bumping.

[0072] In this embodiment, a laser scanner 10 is provided on the side of the ultrasonic phased array sensor 3, and the laser scanner 10 is connected to the signal analysis device 5. The laser scanner 10 can be a commercially available product, such as a commercially available 3D laser scanner. The laser scanner 10 is used to detect the horizontal position and vertical height of the ultrasonic phased array sensor 3 relative to the rail 6, and sends this information to the signal analysis device 5 for processing. The signal analysis device 5 controls the operation of the stepper motors in the horizontal and vertical directions according to the detection results of the laser scanner 10, so that the ultrasonic phased array sensor 3 can be aligned with the center of the rail 6 to be detected and located at a suitable position directly above the rail 6 to ensure the quality of the received ultrasonic echo signal.

[0073] In this embodiment, the signal analysis device 5 is connected to a remote controller 11 for remotely activating the signal analysis device 5.

[0074] In this embodiment, the signal analysis device 5 is a PC, which can be a desktop computer, a laptop computer, or a tablet computer. On one hand, the signal analysis device 5 processes the detection signal from the laser scanner 10 to achieve motion control of the stepper motors in the horizontal and vertical directions; on the other hand, the signal analysis device 5 uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor 3, and performs sparse imaging on this basis to achieve visual characterization of rail defects.

[0075] Using the above-described apparatus, the present invention provides a method for achieving sparse ultrasonic phased array imaging of rail defects, comprising the following steps:

[0076] S1. The inspection vehicle is driven to the section of rail 6 where defect detection is required. The inspection vehicle is equipped with a vehicle bogie 1 at the bottom. There is a side beam 1-1 on each side of the vehicle bogie 1. The bottom of the side beam 1-1 is equipped with a telescopic fixing frame 2 that can extend and retract in the vertical direction. An ultrasonic phased array sensor 3 is installed at the bottom of the telescopic fixing frame 2. The transmitting end of the ultrasonic phased array sensor 3 is connected to the ultrasonic signal excitation source 4, and the receiving end of the ultrasonic phased array sensor 3 is connected to the signal analysis device 5.

[0077] S2. As the inspection vehicle moves, the ultrasonic phased array sensor 3 is controlled by the ultrasonic signal excitation source 4 to emit ultrasonic waves toward the rail 6 and receive the ultrasonic echo reflected back from the rail 6. Then, the ultrasonic echo signal is transmitted to the signal analysis device 5.

[0078] S3, the signal analysis device 5 uses the DSMA algorithm to perform sparse optimization processing on the receiving element position of the ultrasonic phased array sensor 3 (which can effectively reduce the number of ultrasonic echo signals required for imaging), and performs sparse imaging on this basis, thereby realizing the visual characterization of the defects of the rail 6 (while also taking into account imaging efficiency and imaging accuracy). Figure 4 The diagram shown is a flowchart corresponding to sparse imaging. The specific process is as follows:

[0079] S31, Signal analysis device 5 optimizes the SMA algorithm to obtain the DSMA algorithm:

[0080] Because the standard SMA algorithm uses a non-binary encoding method, it is suitable for continuous optimization problems. However, the ultrasonic array sparsity problem is a discrete optimization problem, and the SMA algorithm cannot be directly applied to solving the ultrasonic array sparsity problem. To adapt to the optimization model of ultrasonic sparse linear arrays, the SMA algorithm needs to be improved accordingly, namely:

[0081] First, the maximum number of iterations of the DSMA algorithm is set; second, the slime mold positions are encoded with real numbers and discretized; next, the slime mold position dimension-specific formula is updated; then, a suitable fitness function is constructed to update the positions of the receiving array elements; finally, the algorithm iterative calculation process is executed to select the optimal receiving array element positions.

[0082] Specifically:

[0083] S311. Set the maximum number of iterations for the DSMA algorithm:

[0084] The maximum number of iterations for the DSMA algorithm is set to max = 500. The iteration count t is automatically incremented by one after each iteration. When the iteration count t reaches max, the iteration calculation process ends and the optimization result is output.

[0085] S312. Encode the location of slime molds with real numbers:

[0086] The standard SMA algorithm lacks an encoding method. To adapt to the optimization model of the ultrasonic sparse linear array, a real-number encoding method is used to encode the slime mold positions. Here, d represents the element position, and L represents the aperture length of the ultrasonic phased array sensor. Taking a 32-element linear array as an example, the sparsity is set to 0.5. To satisfy the constraint: st.d1 = 0, d N =L, the dimension of the solution space = 32 * 0.5 - 2 = 14, the location of the slime mold is encoded as:

[0087] γ=[γ1,γ2,…,γ dim ],γ i ∈Z,0<γ i ≤N (1);

[0088] In equation (1): dim is the dimension of the solution space, γ represents the slime mold position encoding, N represents the number of array elements, and Z represents the set of integers;

[0089] Setting d c Let the element spacing be denoted by the following formula:

[0090] d = [d1, d2, ..., d N-1 ,d N ] T ={[γ1,γ2,…,γ dim ] T ×d c}∪{[d1,d N ] T} (2);

[0091] In equation (2): d1, d2…d N The position of the matrix element is indicated by T, which represents the transpose of the matrix.

[0092] S313. Discretize the location of slime mold:

[0093] The position of the slime mold in the solution space during the initialization of the standard SMA algorithm is:

[0094] X 0 = rand·(UB-LB)+LB (3);

[0095] In equation (3): UB and LB are the upper and lower bounds of the solution space, respectively, and rand is a random number between 0 and 1. Since this position is represented as a continuous real value, in order to satisfy the constraint: st.i∈Z,1≤i≤N-1, the position of the slime mold in the solution space needs to be discretized according to equation (4):

[0096] X t =X t-1 *η t (4);

[0097] In the formula η t Let X represent the discrete operator used in the t-th iteration calculation. t This represents the discrete location of the slime mold in the t-th iteration;

[0098] S314. Update the slime mold location dimension-specific formula:

[0099] When updating the location of slime molds using the standard SMA algorithm, since the searchable regions in different dimensions of the solution space are of equal length, the components of the search vector of each slime mold individual in the solution space are fixed across the coordinate axes. To address the issue of unequal searchable regions in different dimensions of the solution space of the ultrasonic array sparse optimization model, the calculation formula for the location of slime molds in the solution space is improved as follows:

[0100]

[0101] In equation (5): L dim = N - dim + 1, where dim represents the dimension of the solution space; This represents the margin adjustment rate, which ranges from [-a, a], where a = arctanh[1-t / (max-t)], and max is the maximum number of iterations set. The deceleration rate is linearly decreasing from 1 to 0; t represents the current iteration number. This indicates the optimal position found in the current iteration. Indicates the current location of the slime mold; This indicates the locations of two randomly selected slime molds. Represents the weight of the slime mold; r represents a random value in the interval [0,1]; p = tanh|S(i) - DF|, i∈1,2,…,n, where S(i) represents The fitness of DF represents the optimal fitness across all iterations;

[0102] S315. Construct a suitable fitness function:

[0103] Constructing a suitable fitness function is crucial for ensuring algorithm convergence and array optimization performance. The constructed fitness function is as follows:

[0104] fitness = {0.8 × (PML / PSL)} 2 +0.2×(MLW full -MLW) 2} (6);

[0105] In equation (6): PSL represents the sidelobe peak value, PML represents the main lobe peak value, and MLW represents the main lobe width. full This represents the maximum main lobe width. Theoretical analysis and multiple experimental verifications show that the optimal receiver element positions can be selected based on the fitness function.

[0106] S316. Execute the algorithm iterative calculation process:

[0107] Determine whether the current number of iterations of the DSMA algorithm has reached the maximum number of iterations. If not, continue to execute steps S313 to S315. If the current number of iterations of the DSMA algorithm has reached the maximum number of iterations, terminate the iterative calculation process and output the optimal receiver array element position.

[0108] S32. After the signal analysis device 5 uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor 3 (effectively reducing the number of ultrasonic echo signals required for imaging while ensuring imaging accuracy), sparse imaging is performed on this basis, specifically:

[0109] After optimizing the SMA algorithm to obtain the DSMA algorithm, the signal analysis device can use the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor to obtain the optimal sparse positions.

[0110] Assuming the number of array elements of the ultrasonic phased array sensor before and after sparsification is N0 and M0 respectively, then a total of N0*N0 ultrasonic echo signals are obtained before sparsification, and a total of N0*M0 ultrasonic echo signals are obtained after sparsification.

[0111] Let the coordinates of any point Q inside the medium under test be (x, z), and let i and j represent the labels of the transmitting and receiving array elements, respectively. The coordinates of the transmitting array element labeled i are (x, z). i ,z i The coordinates of the receiving array element labeled j are (x j,z j The sum of the distances from the transmitting and receiving elements to point Q is denoted as d(x,z). Combined with the propagation speed c of ultrasound in the medium, the travel time T of the sound wave can be calculated using formula (8). ij (x,z) allows us to obtain the amplitude of each ultrasonic echo signal at point Q. Finally, we calculate the amplitude S of the ultrasonic echo signals corresponding to all transmitting and receiving array elements at point Q. ij [T ij The sparse imaging formula can be expressed as follows: [x, z] are superimposed to form the pixel value I(x, z) at any point Q inside the measured medium.

[0112]

[0113]

[0114] The above formula can be used to perform sparse imaging, thereby enabling the visual characterization of rail defects.

[0115] This invention employs an ultrasonic phased array sensor 3, composed of multiple air-coupled ultrasonic sensors arranged at equal intervals, in conjunction with an ultrasonic signal excitation source 4 and a signal analysis device 5, to detect defects in rails 6. During the detection process, the ultrasonic phased array sensor 3, controlled by the ultrasonic signal excitation source 4, emits ultrasonic waves towards the rails 6 and receives ultrasonic echoes reflected from the rails 6. The ultrasonic echo signals are then transmitted to the signal analysis device 5 for analysis and processing. The signal analysis device 5 uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor 3, effectively reducing the number of ultrasonic echo signals required for imaging. Based on this, sparse imaging is performed, realizing the visual characterization of rail defects while balancing imaging efficiency and accuracy, providing a valid basis for rail maintenance.

[0116] Finally, it should be pointed out that the above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for achieving sparse ultrasonic phased array imaging of rail defects, characterized in that: Includes the following steps: S1. The inspection vehicle is driven to the rail section where defect detection is required. The inspection vehicle is equipped with a vehicle bogie at the bottom. There is a side beam on each side of the vehicle bogie. The bottom of the side beam is equipped with a telescopic fixing frame that can extend and retract in the vertical direction. An ultrasonic phased array sensor is installed at the bottom of the telescopic fixing frame. The transmitting end of the ultrasonic phased array sensor is connected to the ultrasonic signal excitation source, and the receiving end of the ultrasonic phased array sensor is connected to the signal analysis device. S2. As the inspection vehicle moves, the ultrasonic phased array sensor is controlled by the ultrasonic signal excitation source to emit ultrasonic waves toward the rail and receive the ultrasonic echoes reflected back from inside the rail. Then, the ultrasonic echo signals are transmitted to the signal analysis device. S3. The signal analysis device uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor, and performs sparse imaging based on this, thereby realizing the visual characterization of rail defects. Specifically: S31. The signal analysis device optimizes the SMA algorithm to obtain the DSMA algorithm, namely: First, the maximum number of iterations of the DSMA algorithm is set; second, the slime mold positions are encoded with real numbers and discretized; next, the slime mold position dimension-specific formula is updated; then, a suitable fitness function is constructed to update the positions of the receiving array elements; finally, the algorithm iterative calculation process is executed to select the optimal receiving array element positions; wherein, S314. The specific steps for updating the slime mold location dimension specific formula are as follows: To address the issue of inconsistencies in the searchable regions across different dimensions of the solution space in the sparse optimization model of ultrasonic arrays, the formula for calculating the location of slime molds in the solution space is improved as follows: (5)； In equation (5): , dim represents the dimension of the solution space; This represents the margin adjustment rate, and its value range is... , max is the maximum number of iterations set; The deceleration rate is linearly decreasing from 1 to 0; t represents the current iteration number. This indicates the optimal position found in the current iteration. Indicates the current location of the slime mold; This indicates the locations of two randomly selected slime molds. represents the weight of the slime mold; r represents a random value in the interval [0,1]. , express The fitness of DF represents the optimal fitness across all iterations; S315. The specific steps for constructing a suitable fitness function are as follows: (6)； In equation (6): fitness represents the fitness function, PSL represents the sidelobe peak value, PML represents the main lobe peak value, MLW represents the main lobe width, and MLW represents the sidelobe peak value. full Indicates the maximum main lobe width; S32. The signal analysis device uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor, and then performs sparse imaging based on this.

2. The method for achieving sparse ultrasonic phased array imaging of rail defects according to claim 1, characterized in that: S311. The specific steps for setting the maximum number of iterations for the DSMA algorithm are as follows: The maximum number of iterations for the DSMA algorithm is set to max=500. The iteration count t is automatically incremented by one after each iteration. When the iteration count t reaches max, the iteration calculation process ends and the optimization result is output. S312. The specific operation for encoding the slime mold location with real numbers is as follows: The positions of slime molds are encoded using a real-number encoding method, where d represents the element position and L represents the aperture length of the ultrasonic phased array sensor. Taking a 32-element linear array as an example, the sparsity is set to 0.5 to satisfy the constraint: st.d1=0, d N =L; The dimension of the solution space = 32 × 0.5 - 2 = 14, and the location of the slime mold is encoded as: (1)； In equation (1): dim is the dimension of the solution space. The location encoding of slime mold is represented by N, where N represents the number of array elements and Z represents the set of integers. Setting d c Let the element spacing be denoted by the following formula: (2)； In formula (2): The position of the matrix element is indicated by T, and the transpose of the matrix is ​​indicated by T. S313. The specific steps for discretizing the location of slime molds are as follows: The position of the slime mold in the solution space during the initialization of the standard SMA algorithm is: (3)； In equation (3): UB and LB are the upper and lower bounds of the solution space, respectively, and rand is a random number between 0 and 1; To satisfy the constraints: The positions of slime molds in the solution space are discretized according to formula (4): (4)； In the formula This represents the discrete operator used in the t-th iteration calculation. This represents the discrete location of the slime mold in the t-th iteration; S316. The specific operations for executing the algorithm iterative calculation process are as follows: Determine whether the current number of iterations of the DSMA algorithm has reached the maximum number of iterations. If not, continue to execute steps S313 to S315. If the current number of iterations of the DSMA algorithm has reached the maximum number of iterations, terminate the iterative calculation process and output the optimal receiver array element position.

3. The method for realizing ultrasonic phased array sparse imaging of rail defects according to claim 2, characterized in that: The specific operation of step S32 is as follows: After optimizing the SMA algorithm to obtain the DSMA algorithm, the signal analysis device uses the DSMA algorithm to perform sparse optimization processing on the receiving element positions of the ultrasonic phased array sensor to obtain the optimal sparse positions. The sparse imaging formula is as follows: (7); (8); In the above formula: It is any point inside the measured medium. The pixel value at that point The coordinates are as ; These are the labels indicating the transmitting array elements. This is a label indicating the receiving array element; It refers to the number of array elements in an ultrasonic phased array sensor before sparseness. It is the number of array elements in the ultrasonic phased array sensor after sparsening; It is the travel time of sound waves. It is the ultrasonic echo signal corresponding to all transmitting and receiving array elements in The amplitude at the point; For transmitting array elements and receiving array elements to The sum of distances between points; The speed at which ultrasound propagates in the medium; It is labeled as The coordinates of the transmitting array elements, It is labeled as The coordinates of the receiving array element.

4. The method for realizing ultrasonic phased array sparse imaging of rail defects according to claim 1, characterized in that: The bottom of the side beam is provided with a slide rail, and a slider adapted to it is movably mounted on the slide rail. The slider is connected to the top of the telescopic fixing frame.

5. The method for realizing ultrasonic phased array sparse imaging of rail defects according to claim 4, characterized in that: Each slider is connected to two telescopic fixing frames. A stabilizing rod that can extend and retract in the vertical direction is provided between the frames of the two telescopic fixing frames. The top of the stabilizing rod is connected to the slider, and the bottom of the stabilizing rod is connected to the ultrasonic phased array sensor.

6. The method for achieving sparse ultrasonic phased array imaging of rail defects according to claim 4 or 5, characterized in that: The slider is equipped with a horizontal stepper motor and a vertical stepper motor inside. The stepper motors are all connected to the signal analysis device and their movement is controlled by the signal analysis device.

7. The method for realizing ultrasonic phased array sparse imaging of rail defects according to claim 1, characterized in that: The ultrasonic phased array sensor is an array composed of multiple air-coupled ultrasonic sensors arranged at equal intervals.

8. The method for achieving sparse ultrasonic phased array imaging of rail defects according to claim 1, characterized in that: A laser scanner is provided on the side of the ultrasonic phased array sensor, and the laser scanner is connected to the signal analysis device.

9. The method for achieving sparse ultrasonic phased array imaging of rail defects according to claim 1, characterized in that: The signal analysis device is connected to a remote controller.

10. The method for realizing ultrasonic phased array sparse imaging of rail defects according to claim 1, characterized in that: The signal analysis device is a PC.

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