A highway pavement milling construction method

Abstract

The present invention relates to the technical field of construction methods, and in particular to a highway pavement milling construction method, which is applied to a pavement milling construction control system; the method comprises: obtaining a three-dimensional topographic map of the pavement and a background image containing pavement markings and structures, and planning a reference line; correcting the reference line according to preset parameters, and inserting points between the calibration points of the corrected reference line at set intervals to determine the initial milling trajectory; using a sliding window least squares method to calculate the target milling depth and target milling trajectory of each insertion point; the milling machine runs at the target milling trajectory, and mills the sub-section corresponding to each window according to the target milling depth. The method plans the target milling trajectory and depth based on the three-dimensional topographic map of the pavement and the background map, significantly improves the flatness of the milled pavement, has high construction accuracy and efficiency, and reduces manpower input and safety hazards on site.

Description

Technical Field

[0001] The invention relates to the technical field of construction methods, in particular to a highway pavement milling construction method. Background Art

[0002] Milling and resurfacing is an important maintenance work to improve the technical condition of highway pavement and driving comfort. Traditional pavement milling technology mainly includes sliding shoe milling and balanced beam milling. Both focus more on system leveling. They are equal-thickness milling without a positioning system and cannot change the undulation of the original pavement. The improvement of pavement flatness after milling is limited. At the same time, the milling construction route, milling position, milling depth, etc. all need to be carried out by manual visual inspection of pile numbers, manual laying out or manual measurement. Traditional pavement milling has problems such as high manual participation, low automation, low data collection efficiency, insufficient safety, and insufficient control precision.

[0003] In order to improve the flatness based on traditional construction, the road elevation needs to be manually fitted before milling. This method does help improve the road flatness, but the source of the elevation data for manual fitting is still on-site manual measurement, and the error is still large; at the same time, due to the functional limitations of the equal-thickness milling machine, manual fitting can only help technicians to formulate a more accurate milling depth, and cannot significantly improve the road flatness. Therefore, how to combine elevation collection, route smoothing and construction control is a technical problem that urgently needs to be solved. Summary of the invention

[0004] In view of this, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a road surface milling construction method that can significantly improve the flatness.

[0005] In a first aspect, the present invention provides a highway pavement milling construction method, which is applied to a pavement milling construction control system; the method comprises:

[0006] Obtaining a three-dimensional topographic map and background image of the road surface;

[0007] Plan reference lines based on 3D topographic maps and background images;

[0008] The reference line is corrected according to preset parameters, and points are inserted between the calibration points of the corrected reference line at set intervals to determine the initial milling trajectory;

[0009] The sliding window least square method is used to linearly fit the initial milling trajectory to determine the target milling depth and target milling trajectory of each insertion point.

[0010] The milling machine runs along the target milling trajectory and mills the sub-section corresponding to each window according to the target milling depth.

[0011] In combination with the first aspect, the step of obtaining a three-dimensional topographic map of a road surface and a background image includes:

[0012] Perform three-dimensional scanning on the road surface to obtain the original point cloud data corresponding to the road surface;

[0013] Perform point cloud thinning processing on the original point cloud data to obtain initial point cloud data;

[0014] Obtaining the overall data of the construction section, and outputting a background image of the road surface based on the preset reference objects and the overall data;

[0015] Construct a three-dimensional topographic map of the road surface based on the initial point cloud data.

[0016] In combination with the first aspect, the background image includes a design line; and the step of planning a reference line according to the three-dimensional topographic map and the background image includes:

[0017] According to the background image, determine whether there is a bridge section in the construction section;

[0018] If so, determine the location of the expansion joint of the bridge section based on the background image;

[0019] Use the expansion joint location as the partition point;

[0020] Divide the design marking line corresponding to the construction section according to the partition point and the first preset distance to obtain multiple marking points;

[0021] The line connecting multiple calibration points is determined as the reference line.

[0022] In combination with the first aspect, after the step of determining whether there is a bridge section in the construction section according to the background image, the method further includes:

[0023] If not, dividing the design marking line according to the second preset distance to obtain a plurality of marking points;

[0024] The line connecting all the marked points on the same design mark line is determined as the reference line;

[0025] In combination with the first aspect, the preset parameters include at least the milling drum width and the lane width.

[0026] The steps of correcting the reference line according to preset parameters and inserting points between the calibration points of the corrected reference line at set intervals to determine the initial milling trajectory include:

[0027] According to the width of the milling drum, the reference line is translated along a first direction, and points are inserted between the calibration points of the modified reference line at set intervals to obtain a first reference line;

[0028] According to the difference between the lane width and the milling drum width, the first reference line is translated along the first direction until an initial milling trajectory covering the entire road surface is obtained;

[0029] The first direction is a direction perpendicular to the extension direction of the construction section, and the first direction and the extension direction of the construction section are in the same horizontal plane.

[0030] In combination with the first aspect, the step of using the sliding window least squares method to perform linear fitting on the initial milling trajectory to determine the target milling depth and target milling trajectory of each insertion point includes:

[0031] Determine the initial milling depth based on the maintenance design plan of the construction section, the thickness of the asphalt layer and the thickness of the undulating points;

[0032] Based on the initial milling depth, the initial milling trajectory is translated along the second direction to obtain the current milling trajectory; the second direction is the vertical direction of the normal of each insertion point in the initial milling trajectory;

[0033] The current milling trajectory is linearly fitted using a sliding window least square method to obtain a plurality of fitting line segments, wherein the plurality of fitting line segments correspond to the plurality of windows one by one;

[0034] For each fitting line segment, obtain the current milling depth corresponding to the midpoint of the fitting line segment window;

[0035] Use the current milling depth as the target milling depth for each insertion point in the window;

[0036] Based on the total target milling depth and the current milling trajectory, the target milling trajectory of the construction section is determined.

[0037] In combination with the first aspect, the step of linearly fitting the current milling trajectory using the sliding window least squares method to obtain multiple fitting line segments includes:

[0038] Dividing the current milling trajectory based on a preset step length and a preset window length to obtain a plurality of windows;

[0039] For each window, the least square method is used to perform linear fitting on the window to obtain the fitting line segment corresponding to the window.

[0040] In combination with the first aspect, for each window, a step of performing a straight line fitting on the window using the least squares method to obtain a fitting line segment corresponding to the window includes:

[0041] Calculate with the following formula:

[0042]

[0043] Among them, the x-axis is the horizontal projection of the current milling trajectory, the y-axis is the straight line perpendicular to the horizontal plane from the starting point of the window, and a j and b j are parameters, xi is the horizontal coordinate of the i-th reference point of the j-th window, that is, the horizontal projection length of the milling trajectory from the i-th reference point in the window to the starting point of the window, y i is the ordinate of the i-th reference point of the j-th window, that is, the elevation value of the i-th reference point, a j is the slope of the fitted line in the jth window, b j is the intercept of the fitted line in the jth window, L is the preset window length, and s is the preset step size.

[0044] In combination with the first aspect, after the step of determining the target milling trajectory of the construction section based on all target milling depths and the current milling trajectory, the method further includes:

[0045] Acquire simulation results of the milling machine running at a target milling trajectory and a target milling depth;

[0046] Determine whether the preset milling flatness requirements are met based on the simulation results;

[0047] If not, the target milling depth is modified until a simulation result that meets the preset milling flatness requirement is obtained.

[0048] In combination with the first aspect, the step of running the milling machine along the target milling trajectory and milling the sub-section corresponding to each window according to the target milling depth includes:

[0049] Get the actual milling depth during construction;

[0050] Compare the actual milling depth during construction with the designed milling depth, obtain the comparison result and use it as a basis to adjust the position of the milling drum;

[0051] Get the current road surface smoothness after construction is completed;

[0052] Compare the current road surface smoothness with the initial road surface smoothness to obtain a comparison result;

[0053] Save the comparison results.

[0054] The embodiments of the present invention bring about the following beneficial effects: the highway pavement milling construction method provided by the present application plans a reference line based on the three-dimensional topographic map and background image of the construction section, corrects the reference line according to preset parameters to determine the initial milling trajectory, and uses the sliding window least squares method to calculate the target milling depth and target milling trajectory of each insertion point of the initial milling trajectory. After that, the milling machine performs construction based on the determined target milling trajectory and target milling depth. The target milling trajectory and target depth are planned based on the three-dimensional topographic map and the background map, fully considering the terrain of the construction section, thereby improving the flatness of the road surface after milling treatment. At the same time, the method has high construction accuracy and efficiency, reduces manpower input and safety hazards on site.

[0055] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0056] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0058] Figure 1 A schematic diagram of the process flow of the highway pavement milling construction method provided by the present invention;

[0059] Figure 2 A schematic diagram of a planning window from the starting point to the end point of a construction section in the highway pavement milling construction method provided by the present invention;

[0060] Figure 3 A schematic diagram of a planning window from the end point to the starting point of a construction section in the highway pavement milling construction method provided by the present invention;

[0061] Figure 4 A flow chart of a highway pavement milling construction method provided in Example 2 of the present invention;

[0062] Figure 5 This is a flow chart of the highway pavement milling construction method provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0064] Traditional road milling technology is uniform thickness milling without a positioning system, which cannot change the undulation of the original road surface, and the improvement of road surface flatness after milling is limited. The source of artificially fitted elevation data is large error in on-site manual measurement and low milling accuracy, which limits the improvement of road surface flatness.

[0065] Based on this, an embodiment of the present application provides a highway pavement milling construction method.

[0066] Example 1

[0067] The present application provides a highway pavement milling construction method, combined with Figure 1 As shown, the method is applied to a digital construction control system; the method comprises:

[0068] S110, obtaining a three-dimensional topographic map of the road surface and a background image.

[0069] S120, planning a reference line according to the three-dimensional topographic map and the background image.

[0070] S130, correcting the reference line according to preset parameters, and inserting points between the calibration points of the corrected reference line at set intervals to determine an initial milling trajectory.

[0071] S140, using a sliding window least square method to perform linear fitting on the initial milling trajectory to determine a target milling depth and a target milling trajectory for each insertion point.

[0072] S150, the milling machine runs along the target milling trajectory, and mills the road section corresponding to the window according to each target milling depth.

[0073] The road milling construction method provided by the present application plans reference lines based on the three-dimensional topographic map of the road surface of the construction section and the background image, corrects the reference lines to determine the initial milling trajectory, and then uses the sliding window least squares method to linearly fit the initial milling trajectory to smooth the initial milling trajectory to obtain the target milling trajectory. At the same time, the target milling depth of the insertion point corresponding to each window is determined during the linear fitting process. Finally, the milling machine runs based on the determined target milling trajectory and mills the sub-section corresponding to the window according to the target milling depth. In this way, the terrain information of the construction section is fully combined and the target milling depth is calculated for each window to improve the flatness of the road surface of the construction section after milling construction.

[0074] In combination with the first aspect, step S110 acquires a three-dimensional topographic map of the road surface and a background image, specifically including:

[0075] S111, performing a three-dimensional scan on the road surface to obtain original point cloud data corresponding to the road surface.

[0076] In this application, in order to improve the intelligence level of construction, reduce the number of workers, and improve the accuracy and engineering efficiency of road milling construction, a point cloud scanning module is first constructed. The point cloud scanning module and the milling machine external control module can share a base station or use multiple base stations for positioning control, which is not limited here.

[0077] Step S111 specifically includes:

[0078] After conducting a site survey and having an overall understanding of the road conditions, a GNSS base station is set up at a location that has a good signal, is not easily interfered with, and is convenient for subsequent construction and multiple installations. The basic parameters of the base station are:

[0079] (1) Static data acquisition frequency: 1 Hz (5 Hz is recommended);

[0080] (2) Satellite signals: support Beidou, Galileo, GPS, GLONASS;

[0081] (3) Static accuracy: Plane accuracy: ±(2.5+0.5×10 -6 ×D)mm, height accuracy: ±(5+0.5×10 -6 ×D)mm.

[0082] (4) RTK accuracy: Plane accuracy: ±(8+1×10 -6 ×D)mm; height accuracy: ±(15+1×10 -6 ×D)mm.

[0083] After the base station is set up, the road surface is scanned by the above-mentioned point cloud scanning module to obtain the three-dimensional coordinate information of the road surface point cloud and the original point cloud data of the road surface. The main technical parameters of the point cloud scanning module equipment are:

[0084] (1) Point cloud ranging accuracy: 0.5mm;

[0085] (2) Point cloud scanning width: ≥3.9m;

[0086] (3) Point cloud data density: 2 mm × 1.5 mm;

[0087] (4) Absolute positioning accuracy: ≤5cm;

[0088] (5) Operating speed: between 30km / h and 100km / h;

[0089] (6) TIF image resolution: 8mm, adjustable, minimum setting is 2mm.

[0090] S112, performing point cloud thinning processing on the original point cloud data to obtain initial point cloud data.

[0091] Since the original point cloud data obtained is massive, the workload of processing massive data is relatively heavy, and there is actually no need to process such a large amount of data, so in order to strike a balance between design accuracy and data processing difficulty, the original point cloud data is thinned out, and the point cloud density range is set to point cloud spacing horizontally × vertically = 1cm × 1cm ~ 6cm × 8cm. If it is smaller than this range, the data processing time will be too long, and if it is larger than this range, the design accuracy will be insufficient.

[0092] S113, obtaining overall data of the construction section, and outputting a background image of the road surface based on the reflectivity of a preset reference object and the overall data.

[0093] After that, the data of multiple scans of the construction section are fused according to the road marking reference objects (such as street lights, markings, trees) to obtain the overall data of the scanned section; at the same time, according to the different reflectivity characteristics of different structures such as road markings, asphalt mixtures, expansion joints, guardrails, etc., the background image of the road surface is output to correspond to the point cloud coordinates. After the data processing is completed, the point cloud data is converted into a preset data format.

[0094] S114, constructing a three-dimensional topographic map of the road surface according to the initial point cloud data.

[0095] The initial point cloud data is imported into the preset software to construct a three-dimensional terrain map model (DTM). It can be generated according to the selected point cloud area, or a three-dimensional model can be generated within the boundary line after defining and drawing the boundary line to obtain a three-dimensional terrain map of the road surface.

[0096] The obtained background image is imported into the above-mentioned preset software, so that the coordinates of each point in the background image are consistent with the corresponding point cloud coordinate position in the three-dimensional topographic map.

[0097] It can be understood that the road milling construction control system provided in this embodiment includes a control mechanism. As an implementable method, the control mechanism stores the pre-acquired three-dimensional topographic map and background image of the road surface, that is, the background image of the construction section and the three-dimensional topographic map of the road surface are acquired within a set time before construction or based on the road surface point cloud information stored after the previous construction, and stored in the control mechanism. In this way, the three-dimensional topographic map and background image of the road surface of the construction section can be directly retrieved from the control mechanism during the current construction.

[0098] Step S120 plans reference lines according to the three-dimensional topographic map and the background image, specifically including:

[0099] S121, judging whether there is a bridge section in the construction section according to the background image.

[0100] If yes, that is, there is a bridge section in the construction section, execute steps S122-S125; if no, that is, there is no bridge section in the construction section, execute steps S126-S127.

[0101] S122, determining the expansion joint position of the bridge section according to the background image.

[0102] S123, the expansion joint position is used as the partition point.

[0103] Among them, the expansion joint position (including the concrete pouring area) is not milled.

[0104] S124, dividing the design marking line corresponding to the construction section according to the partition point and the preset distance to obtain a plurality of marking points.

[0105] S125, determining a line connecting the plurality of calibration points as a reference line.

[0106] When there is a bridge section, first determine the position of the expansion joint of the bridge section as the partition point of the overall reference line. Then, according to the principle of "replacing curves with straight lines and setting the distance", divide the other sections of the construction section, that is, use a combination of multiple straight lines instead of curves in curved sections, and try to ensure that the distance between each line segment is an integer and equidistant. It is recommended to set a calibration point every 50-100m in long straight sections, a calibration point every 20m in short straight sections, and a calibration point every 5-15m in curves. Manual positioning is used in locations where equidistant alignment cannot be used. It is worth noting that when translating the reference line, in order to meet the requirement of consistent pile numbers during design, the length of the reference line after translation will be shortened. In order to avoid the loss of reference points due to shortened length, the occurrence of non-integer alignment should be minimized in this process.

[0107] S126, dividing the designed marking line according to the second preset distance to obtain a plurality of marking points.

[0108] S127, determining the line connecting all the marking points on the same design marking line as the reference line.

[0109] Similarly, the method of “replacing curves with straight lines and setting lines at fixed distances” is adopted to divide the design marking line into multiple marking points, and then determine the reference line.

[0110] In combination with the first aspect, S130 corrects the reference line according to preset parameters, and inserts points between the calibration points of the corrected reference line at set intervals. The preset parameters in the step of determining the milling trajectory include at least the milling drum width and the lane width. Step S130 specifically includes:

[0111] S131, according to the width of the milling drum, translate the reference line along the first direction, and insert points between the calibration points of the first reference line at set intervals to obtain a first reference line.

[0112] Since the width of the commonly used milling drum is D=2m, the distance of the first translation is generally S1=2m. In other cases, the distance of the first translation should be consistent with the width of the milling drum used. The first direction is a direction perpendicular to the extension direction of the construction section, and the first direction and the extension direction of the construction section are in the same horizontal plane. For example, in geodetic coordinates, the extension direction of the construction section is set to the X-axis, the elevation direction of the construction section is the Z-axis, the Y-axis is in the same horizontal plane as the X-axis, and the Z-axis is perpendicular to the horizontal plane where the X-axis and the Y-axis are located. In this embodiment, the first direction refers to the direction of the Y-axis.

[0113] To ensure that there is no missed milling in adjacent milling tracks, it is necessary to ensure that adjacent milling tracks have overlapping parts, so the subsequent reference line translation distance should be less than 2m or the width of the milling drum used. The remaining milling track translation distance can be divided according to the distance remaining after deducting the milling drum width from the overall width of the road section, or it can be determined according to the width of a single lane. The milling track should fall on the edge of the marking line.

[0114] At the same time, the corrected reference line (i.e., the reference line after translation processing along the first direction) is interpolated to set the spacing between two adjacent calibration points to insert more dense reference points, for example, insert an insertion point every 10cm, 25cm, 50cm, etc., to obtain more points on the reference line, and all of these points are used as reference points. It is worth noting that the spacing between reference points can be selected according to the actual engineering accuracy requirements, but should not be less than the spacing between two original points in the three-dimensional topographic map.

[0115] S132, according to the difference between the lane width and the milling drum width, the first reference line is translated along a first direction until an initial milling track covering the entire road surface is obtained, wherein the first direction is a direction perpendicular to the extension direction of the construction section, and the first direction and the extension direction of the construction section are in the same horizontal plane.

[0116] The standard lane width is W0=3.75m. During the milling process, it is preferred to mill according to the lane width. Since step S131 has been translated by 2m, the translation distance S2=S0-S1. The subsequent translation distance can be determined according to the width of the adjacent markings. The remaining milling track translation distance can be divided equally according to the distance remaining after deducting the milling drum width from the overall width of the road section, or it can be determined according to the width of a single lane. The milling track should preferably fall on the edge of the marking. The first reference line is translated multiple times until an initial milling track that can cover the entire road surface is obtained.

[0117] In combination with the first aspect, step S140 uses a sliding window least squares method to perform linear fitting on the initial milling trajectory to determine a target milling depth and a target milling trajectory for each insertion point, specifically including:

[0118] S141, determine the initial milling depth based on the maintenance design plan of the construction section, the thickness of the asphalt layer and the thickness of the undulating points.

[0119] After confirming the initial milling trajectory, the initial milling depth is calculated. Specifically, in order to avoid damage to the underlying layer of the road surface during construction, the milling depth should not exceed the thickness of the asphalt pavement layer. At the same time, in order to ensure a smooth line shape, the maximum milling depth should be greater than the thickness of the maximum undulation point of the road surface.

[0120] S142, based on the initial milling depth, the milling trajectory is translated along the second direction to obtain the current milling trajectory, where the second direction is a direction perpendicular to the normals of the insertion points of the initial milling trajectory.

[0121] The longitudinal section line of the original road surface line is translated downward by the initial milling depth, that is, the initial milling trajectory is translated by the initial milling depth distance along the height direction (combined with the Z axis of the geodetic coordinate system described above).

[0122] S143, using a sliding window least square method to perform linear fitting on the current milling trajectory to obtain a plurality of fitting line segments, wherein the plurality of fitting line segments correspond to the plurality of windows one by one.

[0123] S145, for the fitting line segment, obtaining the current milling depth corresponding to the midpoint of the fitting line segment window.

[0124] S146, taking the current milling depth as the target milling depth of the window;

[0125] S147, determining a target milling trajectory of the construction section based on all target milling depths and the current milling trajectory.

[0126] After determining the initial milling trajectory, multiple insertion points are first inserted into the initial milling trajectory to obtain more reference points on the initial milling trajectory. Then, the initial milling depth is determined based on the asphalt layer pavement thickness and the thickness of the undulating point, and the target milling depth of each window is determined through linear fitting. Based on the target milling depth of each window, the current milling trajectory is corrected to obtain the target milling trajectory. In this way, the milling depth calculation is performed for the sections corresponding to each window in the construction section, so that the flatness of the construction section after milling construction is improved.

[0127] In combination with the first aspect, step S144 uses a sliding window least square method to perform linear fitting on the current milling trajectory to obtain multiple fitting line segments. The specific method is as follows:

[0128] S1441, dividing the current milling trajectory based on a preset step size and a preset window length to obtain multiple windows.

[0129] The two end points of the initial milling trajectory are respectively used as the starting point and the end point, and the first window is planned with the preset window length L as the starting point of the first window; and the step length s after the starting point is used as the starting point of the second window, and the second window is planned with the preset window length L; the starting point of the third window is used as the point twice the step length s after the starting point, and the third window is planned with the preset window length L... Similarly, the window is planned from the end point of the initial milling trajectory toward the starting point.

[0130] Assume that the initial milling trajectory has n points (including left and right endpoints) after inserting reference points at preset intervals. Let the starting point of the reference design line be numbered 1 and the end point be numbered n. All reference points in the initial milling trajectory are represented by a data point sequence: D = [(x1, y1), (x2, y2), (x3, y3), …, (x n ,y n )], where x i is the horizontal projection of the distance between the reference point i and the starting point, y i is the elevation value corresponding to the reference point i.

[0131] With the interval s as the step length and the window length = L, the least squares fitting is performed, and the start and end mileage expressions of each calculation window are:

[0132]

[0133] Among them, x s is the starting mileage, x e is the terminal mileage, x n is the nth reference point. s 、x e , we can get the corresponding sequence subset D′={(x,y)|x s <x<x e}.

[0134] Along the starting point to the end point of the initial milling trajectory, the sliding window path is as follows Figure 2 As shown; along the direction from the end point to the starting point of the initial milling trajectory, the sliding window path is as follows Figure 3 shown.

[0135] Among them, the preset window length can also be determined based on the principle of minimum engineering workload.

[0136] S1442, for each window, a least square method is used to perform straight line fitting to obtain a fitting line segment corresponding to the window.

[0137] Among them, according to the order of step size s, the corresponding window is j, and the straight line expression is y = a j x+b j , then for each reference point x in window j i , the corresponding fitted value is yi =a j x i +b j , the objective function can be written as:

[0138]

[0139] Among them, a j , b j is the parameter, Y i For point x i The actual elevation value.

[0140] According to the principle of least squares method, the sum of the squares of the distances from all points to the fitting line is minimized, and the parameters a and j With parameter b j The partial derivatives of are:

[0141]

[0142] Solve the above about a i With b i The result of the two-variable linear equation system is:

[0143]

[0144] Calculate each window a in turn according to the original ground data in each window j With b j value, and obtain the straight line expression after fitting in the jth window.

[0145] In step S145, the entire construction section is fitted to form a curve connected by multiple fitting line segments. To avoid the curve being too smooth, only the fitting elevation data at the midpoint of each window is calculated in each window, and this is used as the final fitting data of the point. Figure 2 It can be seen that from the starting point to the window length distance L / 2, the length of each window is less than the complete window length L. At this time, the elevation of the point at a distance of L / 2 from the end point of each window is calculated as the fitting elevation of the point; Figure 3 It can be seen that the end point has the same situation as the starting point. After the same processing as the starting point window, there is a large fluctuation with other fitting data. In order to reduce the fluctuation, a straight line is determined by using the fitting data of the reference point with a distance L from the end point and the data after deducting the preliminary designed milling depth D from the original elevation of the end point, so that all fitting points within a distance L from the end point fall on this straight line, and the corresponding fitting elevation is used as the final fitting elevation data of the corresponding point.

[0146] Depend on Figure 2 , Figure 3It can be seen that at the beginning L / 2 and the end L / 2 of the current milling trajectory, the window size is less than L. It is necessary to decide whether to adjust it according to the final calculation result. The smoothness of the final milling line can be adjusted by adjusting the length of the window L.

[0147] In combination with the first aspect, after determining the target milling trajectory of the construction section based on all target milling depths and the current milling trajectory in step S146, the method further includes:

[0148] Get simulation results of the milling machine running at the target milling trajectory and target milling depth.

[0149] Determine whether the preset milling flatness requirements are met based on the simulation results.

[0150] If not, adjust the target milling depth until a simulation result that meets the preset milling flatness requirement is obtained.

[0151] In the present application, the construction situation can be simulated by means of simulation software to obtain simulation results after milling the road section corresponding to each window based on the determined target running trajectory and the target milling depth. Then, by setting the equal-thickness milling elevation surface, the software is imported to check whether there is a large area of ​​the construction section where the milling design surface is higher than the original road surface, that is, whether there is a large area of ​​filled road section. If so, it means that the road surface flatness is poor and the target milling depth needs to be corrected. As an implementable method, the initial milling depth is changed, and the target milling depth of each window is re-performed and the simulation is performed again until the simulation results satisfy that there is no large area of ​​filled road section in the overall road section and the flatness requirements are met at the same time. As another implementable method, the window length L can be changed while keeping the initial milling depth unchanged, and the target milling depth corresponding to each window can be recalculated. Similarly, the simulation is performed again until the simulation results satisfy that there is no large area of ​​filled road section in the overall road section and the flatness requirements are met at the same time.

[0152] It is worth noting that after step S1423, if the cross section does not meet the drainage elevation requirements (the elevation of the hard shoulder of the non-superelevation section is lower than the elevation of the central dividing strip, and the superelevation section meets the design superelevation elevation requirements), the cross section elevation needs to be adjusted until the requirements are met.

[0153] Step S150: The milling machine runs along the target milling trajectory and performs milling on the sub-section corresponding to each window according to the target milling depth. Specifically, the steps include:

[0154] Establish a communication connection between the milling machine and the road milling construction control system. Combined with the above example, a sensor can be installed near the milling drum of the milling machine, and a positioning receiving antenna can be installed on the top of the milling machine.

[0155] The coordinate system of the milling machine is verified with the coordinates in the road milling construction control system, and subsequent construction is continued within the allowable error range. The usually acceptable error range is 1-2cm.

[0156] Afterwards, the milling machine runs according to the target milling trajectory, and performs milling at the calculated target milling depth on the sub-section corresponding to each window, so as to achieve targeted milling of each sub-section, thereby improving the flatness of the construction section after construction. Compared with the scenario in which milling is performed at a unified milling depth in the prior art, the flatness of the construction section can be significantly improved.

[0157] Preferably, the construction process uses RTK to check the real-time milling depth in real time and compare it with the calculated target milling depth, so as to adjust the position of the milling drum in real time and improve the degree of automation.

[0158] In combination with the first aspect, after the step S150 in which the milling machine runs along the target milling trajectory and mills the sub-section corresponding to each window according to the target milling depth, the method further includes:

[0159] S160, obtaining the actual milling depth during the construction process.

[0160] S170, comparing the actual milling depth during the construction process with the designed milling depth, and adjusting the position of the milling drum in real time based on the comparison.

[0161] S180, obtaining the current road surface smoothness after the construction is completed.

[0162] S190, comparing the current road surface flatness with the initial road surface flatness to obtain a comparison result.

[0163] S200, saving the comparison result.

[0164] After the construction is completed, the road surface flatness is tested and compared with the initial flatness, and the construction-related data is recorded to facilitate subsequent program adjustments and optimization.

[0165] After the construction is completed, verification is carried out according to the on-site conditions: if paving is required immediately, different representative reference points are selected, such as the transition points of milling depth changes, points with larger or smaller milling depths, for coordinate verification; if paving can be delayed, the point cloud scanning module can be used to scan the road surface after milling, and the data before and after milling can be imported into the data processing software, and the code can be used to implement the elevation verification of the same north-east coordinate points.

[0166] Example 2

[0167] This embodiment explains the situation that the construction section is a straight line section with no bridges or tunnels in the section.

[0168] Combination Figure 4 As shown, specifically, obtain the point cloud information of the road surface: use the point cloud scanning module to obtain the three-dimensional point cloud information of the road surface, and at the same time obtain the background image with clear road markings. Thin the point cloud spacing to horizontal × vertical width = 6cm × 8cm, and convert it into .las format for output.

[0169] Generate a triangular mesh 3D topographic map: Import the thinned point cloud data into the preset software, and use the "Generate topographic map by selected area" function to generate a triangular mesh 3D topographic map.

[0170] Background image insertion: Insert a .tif format background image and check if there are any coordinate differences with the topographic map.

[0171] Background image verification: Based on the background image, determine whether there are bridges and tunnels. In this embodiment, there are no bridges and tunnels.

[0172] Planning reference line: Using the background map as a reference, insert the reference line along the outer contour line of the outermost marking line every 50m as a calibration point. There is no partition in the middle of the reference line, extending from the milling start point to the milling end point.

[0173] Densified design elevation points: Select 25cm as the step size and add multiple insertion points on the reference line.

[0174] Shift the reference line according to the milling width: According to the lane width and lane distribution, shift the initial milling trajectory by a distance of 2m+Nm to ensure that the outer edge of each marking line coincides with the reference line to obtain the initial milling trajectory.

[0175] According to the designed milling depth, the ground line is translated downward as the design line: according to the thickness of the pavement layer, the initial milling depth is determined to be 20mm, and the longitudinal section is translated downward by 20mm, that is, the initial milling trajectory is translated to obtain the current milling trajectory.

[0176] Smoothing the design line: Use the sliding window least squares method mentioned above to linearly fit the curve to smooth the initial milling trajectory, and determine the target milling depth of the window according to the elevation of the midpoint of each window to determine the target milling trajectory.

[0177] Verify the results of the construction simulation to determine whether there is a large area of ​​fill: check the cross section of the entire target milling trajectory, adjust the cross slope to ensure the correct superelevation of the road, keep the hard shoulder elevation lower than the central divider elevation, and ensure smooth drainage of the entire road surface.

[0178] If there is a large area of ​​fill, it is necessary to recalculate the initial milling depth based on the road conditions and pavement structure layer, and recalculate the target milling depth of each window.

[0179] Save and output construction data: Export the target milling trajectory and target milling depth in .txt format and transmit them to the milling machine. During the construction process, global positioning technology is used to ensure that the milling machine's route does not deviate from the target milling trajectory. The system external module is used to adjust the milling drum up and down to achieve the purpose of variable milling of the entire line.

[0180] Example 3

[0181] This embodiment takes the construction section as a straight and curved combination section, and there is a bridge in the construction section as an example to explain the method provided by the present application. Figure 5 As shown, specifically: In order to ensure the accuracy of construction, the point cloud scanning module is used to obtain and thin the point cloud to a density of 1cm×1cm, and then converted into .xyz format for output.

[0182] Generate a 3D topographic map and draw a reference line along the road markings. Additional calibration points are required at the bridge expansion joints. When designing the milling depth, ensure that the bridge expansion joints remain unchanged in elevation, and all other points are shifted downward to the initial milling depth; then use the expansion joints as breakpoints and smooth the longitudinal curves before and after the expansion joints through linear fitting.

[0183] After that, the cross slope is processed, and after checking that there is no large amount of fill on the road surface and that the drainage and superelevation meet the requirements, the data is exported and transmitted to the milling machine. The milling machine control module performs construction according to the target milling trajectory and target milling depth.

[0184] An embodiment of the present application also provides a road milling system, including a control mechanism, a point cloud scanning module, and a communication module. The control mechanism is connected to the control module and the point cloud scanning module of the milling machine through the communication module.

[0185] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0186] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0187] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0188] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0189] Finally, it should be noted that the above embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that any person skilled in the art can still modify the technical solutions recorded in the above embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A highway pavement milling construction method, characterized in that: The method is applied to a road milling construction control system; the method comprises: Obtaining a three-dimensional topographic map and background image of the road surface; Plan reference lines based on 3D topographic maps and background images; Correcting the reference line according to preset parameters, and inserting points between the calibration points of the corrected reference line at set intervals to determine an initial milling trajectory; The initial milling trajectory is linearly fitted using a sliding window least squares method to determine a target milling depth and a target milling trajectory for each insertion point; The milling machine runs along the target milling trajectory and mills the sub-section corresponding to each window according to the target milling depth.

2. The method according to claim 1, characterized in that The step of obtaining the three-dimensional topographic map and background image of the road surface includes: Performing a three-dimensional scan on a road surface to obtain original point cloud data corresponding to the road surface; Performing point cloud thinning processing on the original point cloud data to obtain initial point cloud data; Acquire overall data of the construction section, and output a background image of the road surface based on the reflectivity of a preset reference object and the overall data; A three-dimensional topographic map of the road surface is constructed according to the initial point cloud data.

3. The method according to claim 1, characterized in that The background image includes original road markings and various artificial markers; The steps of planning reference lines based on the 3D topographic map and background image include: Judging whether there is a bridge section in the construction section according to the background image; If so, determining the location of the expansion joint of the bridge section according to the background image; The expansion joint position is used as a partition point; Dividing the design marking line corresponding to the construction section according to the partition point and the first preset distance to obtain a plurality of marking points; The line connecting all the marked points on the same design mark line is determined as the reference line.

4. The method according to claim 3, characterized in that After the step of judging whether there is a bridge section in the construction section according to the background image, the method further includes: If not, dividing the designed marking line according to a second preset distance to obtain a plurality of marking points; The line connecting all the calibration points on the same design mark line is determined as the reference line.

5. The method according to claim 1, characterized in that The preset parameters include at least the milling drum width and the lane width; The step of correcting the reference line according to preset parameters and inserting points between the calibration points of the corrected reference line at set intervals to determine the initial milling trajectory includes: According to the width of the milling drum, the reference line is translated along a first direction, and points are inserted between the calibrated points of the first reference line at set intervals to obtain a first reference line; According to the difference between the lane width and the milling drum width, translating the first reference line along the first direction until an initial milling trajectory covering the entire road surface is obtained; The first direction is a direction perpendicular to the extension direction of the construction section, and the first direction and the extension direction of the construction section are in the same horizontal plane.

6. The method according to claim 5, characterized in that The step of using the sliding window least square method to linearly fit the initial milling trajectory to determine the target milling depth and target milling trajectory of each insertion point includes: Determine the initial milling depth based on the maintenance design plan of the construction section, the thickness of the asphalt layer and the thickness of the undulating points; Based on the initial milling depth, the initial milling trajectory is translated along a second direction to obtain a current milling trajectory, where the second direction is a direction perpendicular to the normal of each insertion point in the initial milling trajectory; The current milling trajectory is linearly fitted using a sliding window least square method to obtain a plurality of fitting line segments; wherein the plurality of fitting line segments correspond to the plurality of windows one by one; For each fitting line segment, obtaining the current milling depth corresponding to the midpoint of each window of the fitting line segment; Using the current milling depth as the target milling depth for each of the insertion points in the window; Based on all of the target milling depths and the current milling trajectory, a target milling trajectory of the construction section is determined.

7. The method according to claim 6, characterized in that The step of using the sliding window least square method to perform linear fitting on the current milling trajectory to obtain multiple fitting line segments includes: Dividing the current milling trajectory based on a preset step length and a preset window length to obtain a plurality of windows; For each of the windows, a least square method is used to perform linear fitting on the window to obtain a fitting line segment corresponding to the window.

8. The method according to claim 7, characterized in that The step of performing straight line fitting on each window by using the least square method to obtain a fitting line segment corresponding to the window includes: For the jth window, the calculation is as follows: Among them, the x-axis is the horizontal projection of the current milling trajectory, the y-axis is the straight line perpendicular to the horizontal plane from the starting point of the window, and a j and b j are parameters, x i is the horizontal coordinate of the i-th reference point of the j-th window, that is, the horizontal projection length of the milling trajectory from the i-th reference point in the window to the starting point of the window, y i is the ordinate of the i-th reference point of the j-th window, that is, the elevation value of the i-th reference point, a j is the slope of the fitted line in the jth window, b j is the intercept of the fitted line in the jth window, L is the preset window length, and s is the preset step size.

9. The method according to claim 1, characterized in that: After the milling machine runs along the target milling trajectory and performs the milling step on the sub-section corresponding to each window according to the target milling depth, the method further includes: Acquire simulation results of the milling machine running at the target milling trajectory and the target milling depth; Determine whether the preset milling flatness requirement is met according to the simulation result; If not, the target milling depth is modified until a simulation result that meets the preset milling flatness requirement is obtained.

10. The method according to claim 1, characterized in that The step of the milling machine running along the target milling trajectory and milling the sub-section corresponding to each window according to the target milling depth includes: Get the actual milling depth during construction; Compare the actual milling depth during construction with the designed milling depth, obtain the comparison result and use it as a basis to adjust the position of the milling drum; Get the current road surface smoothness after construction is completed; Comparing the current road surface flatness with the initial road surface flatness to obtain a comparison result; The comparison result is saved.

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