Guide rail straightness measuring method based on line laser three-dimensional scanning

Abstract

The invention relates to the technical field of three-dimensional measurement, in particular to a guide rail straightness measurement method based on line laser three-dimensional scanning, and the method comprises the steps: obtaining guide rail point cloud data through a line laser three-dimensional scanner; traversing the guide rail point cloud data, and calculating a linear equation of each scanning position of the guide rail; obtaining a three-dimensional point array for straightness calculation based on the linear equation parameters; obtaining a reference straight line for straightness calculation based on the three-dimensional point array; the distance between each point of the three-dimensional point array and the reference straight line is calculated, the minimum value is subtracted from the maximum value, and the straightness of the guide rail is obtained, the high-precision linear motor drives the line laser three-dimensional scanner to obtain complete three-dimensional point cloud data of the measured guide rail, and then measurement of the straightness of the guide rail is completed based on the obtained point cloud data. According to the invention, high-speed and high-precision automatic measurement of the straightness of the guide rail is realized, the problem of damage to the surface of the guide rail caused by traditional contact measurement is avoided, errors caused by manual measurement are reduced, and the measurement speed and precision are high.

Description

Technical Field

[0001] The present invention relates to the field of three-dimensional measurement technology, and in particular to a guide rail straightness measurement method based on line laser three-dimensional scanning. Background Art

[0002] In traditional manufacturing, measuring product dimensions usually relies on manual measurement or contact measurement tools. In traditional guide rail straightness measurement, a feeler gauge is usually used for measurement. The guide rail to be measured is placed on a testing platform, and a feeler gauge is used to measure the contact surface between the guide rail and the testing platform.

[0003] However, this contact measurement method will not only damage the surface of the guide rail being measured, but also cause human errors. In addition, since the variation curve of the guide rail straightness cannot be obtained, it is impossible to straighten the guide rail with unqualified straightness. Summary of the invention

[0004] The purpose of the present invention is to provide a guide rail straightness measurement method based on line laser three-dimensional scanning, aiming to solve the problem that the contact measurement method not only damages the surface of the guide rail being measured, but also has human error.

[0005] To achieve the above object, the present invention provides a guide rail straightness measurement method based on line laser three-dimensional scanning, comprising the following steps:

[0006] Obtain guide rail point cloud data through a line laser 3D scanner;

[0007] Traversing the guide rail point cloud data, and calculating the straight line equation of each scanning position of the guide rail;

[0008] Obtaining a three-dimensional point array for straightness calculation based on the straight line equation parameters;

[0009] Acquire a reference straight line for straightness calculation based on the three-dimensional point array;

[0010] The distance from each point in the three-dimensional point array to the reference straight line is calculated, and the minimum value of the distance is subtracted from the maximum value to obtain the straightness of the guide rail.

[0011] The specific method of obtaining the guide rail point cloud data by using a line laser 3D scanner is as follows:

[0012] Place the high-precision linear motor and the guide rail to be measured on a marble platform, and then fix the line laser 3D scanner on the linear motor;

[0013] The sampling interval of the line laser three-dimensional scanner is set, and the linear motor is controlled to drive the line laser three-dimensional scanner to collect point cloud data on the surface of the measured guide rail to obtain the guide rail point cloud data.

[0014] The specific method of traversing the guide rail point cloud data and calculating the straight line equation of each scanning position of the guide rail is:

[0015] Traversing the complete guide rail three-dimensional point cloud data;

[0016] The guide rail point cloud data of each scanning position of the measured guide rail is extracted, and then straight line fitting is performed respectively to obtain the straight line equation of each scanning position.

[0017] The specific method of obtaining the three-dimensional point array for straightness calculation based on the straight line equation parameters is as follows:

[0018] Obtain the width of the guide rail to be measured and the starting point of the guide rail point cloud at each scanning position, and obtain the three-dimensional point at the middle position of the guide rail point cloud, that is, the middle point, based on the parameters of the straight line equation;

[0019] A plane with the straight line direction as the normal vector is constructed, the plane of the middle point is used as the reference plane, and the intersection of the straight line at each scanning position and the reference plane is calculated to obtain a three-dimensional point array for straightness calculation.

[0020] The specific method of obtaining the reference straight line for straightness calculation based on the three-dimensional point array is as follows:

[0021] Establishing a vertical plane perpendicular to the reference plane and passing through the middle point;

[0022] Calculating the distance from each point in the three-dimensional point array to the vertical plane to obtain multiple sets of distance data;

[0023] Histogram statistics are performed on multiple groups of distance data to count the data sizes in different distance ranges, and the distance data with the most data are screened out for straight line fitting to obtain a reference straight line for straightness calculation.

[0024] The invention discloses a guide rail straightness measurement method based on line laser three-dimensional scanning, wherein the guide rail point cloud data is obtained by a line laser three-dimensional scanner; the guide rail point cloud data is traversed to calculate the straight line equation of each scanning position of the guide rail; a three-dimensional point array for straightness calculation is obtained based on the straight line equation parameters; a reference straight line for straightness calculation is obtained based on the three-dimensional point array for straightness calculation; the distance from each point in the three-dimensional point array to the reference straight line is calculated, and the minimum value of the distance is subtracted from the maximum value to obtain the guide rail straightness. The method places the guide rail to be measured on a marble platform, drives the line laser three-dimensional scanner to obtain the complete three-dimensional point cloud data of the guide rail to be measured by a high-precision linear motor, and then completes the measurement of the guide rail straightness based on the obtained point cloud data, realizing the high-speed and high-precision automatic measurement of the guide rail straightness. The method effectively avoids the problem of damage to the guide rail surface caused by traditional contact measurement, reduces the error caused by manual measurement, and the measurement system only needs to press the measurement button to complete the collection of the guide rail point cloud data, and then returns the straightness value of the side of the current guide rail, with fast measurement speed and high precision. The contact measurement method solves the problem that not only the surface of the guide rail to be measured is damaged, but also there is a problem of human error. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a flow chart of a guide rail straightness measurement method based on line laser three-dimensional scanning provided by the present invention.

[0027] Figure 2 It is a flowchart of a specific method of obtaining guide rail point cloud data through a line laser 3D scanner.

[0028] Figure 3 It is a flowchart of a specific method of traversing the guide rail point cloud data and calculating the straight line equation of each scanning position of the guide rail.

[0029] Figure 4 It is a flowchart of a specific method of obtaining a three-dimensional point array for straightness calculation based on the straight line equation parameters.

[0030] Figure 5 It is a flowchart of a specific method for obtaining a reference straight line for straightness calculation based on the three-dimensional point array. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0032] See also Figures 1 to 5 The present invention provides a guide rail straightness measurement method based on line laser three-dimensional scanning, comprising the following steps:

[0033] S1 obtains the guide rail point cloud data through a line laser 3D scanner;

[0034] Specific method:

[0035] S11 places the high-precision linear motor and the guide rail to be measured on a marble platform, and then fixes the line laser 3D scanner on the linear motor;

[0036] In the embodiment of the present invention, the measuring system places the high-precision linear motor and the guide rail to be measured on a marble platform, and fixes the line laser 3D scanner on the linear motor through a mounting plate. The line laser 3D scanner is hereinafter referred to as the scanner.

[0037] S12 sets the sampling interval of the line laser 3D scanner, controls the linear motor to drive the line laser 3D scanner to collect the point cloud data of the upper surface of the measured guide rail, and obtains the guide rail point cloud data.

[0038] In an embodiment of the present invention, the sampling interval of the scanner is set by software, and the movement of the linear motor is controlled to drive the scanner to collect point cloud data on the upper surface of the measured guide rail. Specifically, the sampling interval of the line laser three-dimensional scanner is first determined, and then the moving distance of one output pulse of the linear motor is determined according to the parameters of the high-precision linear motor. The trigger mode of the scanner is set to the pulse trigger mode, and the sampling frequency and number of sampling rows of the scanner are set accordingly. The scanning of the scanner can be controlled by the output pulse of the linear motor. During actual operation, by controlling the linear motor to run at a set speed, when the linear motor moves a certain distance, a pulse will be output to the scanner, thereby triggering the scanner to scan. When the linear motor moves to the end point, the scanner obtains the complete three-dimensional point cloud data of the guide rail.

[0039] S2 traverses the guide rail point cloud data and calculates the straight line equation of each scanning position of the guide rail;

[0040] Specific method:

[0041] S21 traverses the complete guide rail three-dimensional point cloud data;

[0042] S22 extracts the guide rail point cloud data at each scanning position of the measured guide rail, and then performs straight line fitting respectively to obtain the straight line equation of each scanning position.

[0043] In the embodiment of the present invention, the data is split into the guide rail point cloud data at each scanning position according to the size of the y value of the three-dimensional point. For example, y=1 represents the guide rail point cloud data at the first scanning position. Then, a straight line fitting is performed on the guide rail point cloud data at each scanning position. The obtained straight line equation is as follows:

[0044]

[0045] In the above formula, p=(x,y,z) represents any point on the line, p0=(x0,y0,z0) represents a point on the line, l=(l x ,l y ,l z ) represents the direction vector of the line.

[0046] S3 obtains a three-dimensional point array for straightness calculation based on the straight line equation parameters;

[0047] Specific method:

[0048] S31 obtains the width of the guide rail to be measured and the starting point of the guide rail point cloud at each scanning position, and obtains a three-dimensional point at the middle position of the guide rail point cloud, that is, a middle point, based on the parameters of the straight line equation;

[0049] In the embodiment of the present invention, by obtaining the width of the guide rail and the starting point of the guide rail point cloud at each scanning position, the three-dimensional point P at the middle position of the guide rail point cloud can be obtained based on the parameters of the straight line equation. mid , that is, the middle point P mid Specifically, according to the straight line equations of all scanned positions, the direction vectors of n straight lines can be obtained. The direction of the first straight line is taken as the positive direction, and the directions of the remaining n-1 straight lines are unified. If the angle between the direction vector of the current straight line and the direction vector of the first straight line is greater than 90°, the current direction vector is reversed. If it is less than 90°, it remains unchanged. After the directions are unified, the average value of the n direction vectors is calculated. The formula is as follows:

[0050]

[0051] In the above formula, n represents the number of sampling lines of the scanner, l i represents the direction vector of the i-th fitting line, Represents the average value of the direction vectors of these n straight lines.

[0052] According to the size of the x-coordinate value of the rail point cloud data at the current scanning position, the starting point and the ending point of the data can be obtained, and the width of the current rail can be calculated based on these two points. In order to eliminate the influence of noise on the calculation of the rail width, the starting point and the ending point of the rail point cloud data at all scanning positions are obtained to obtain the starting point array and the ending point array. The two arrays are sorted based on the x-coordinate value of the three-dimensional point, and then the median of the array is obtained to obtain a starting point p start =(x start ,y start ,z start ) and the end point p end =(x end ,y end ,z end ), the rail width w can be solved by the following formula:

[0053]

[0054] According to the starting point median p start , the width w of the guide rail and the average value of the straight line direction vector right After normalization, we can get the three-dimensional point coordinates p located in the middle of the guide rail. mid =(x mid ,y mid ,z mid ), the formula is as follows:

[0055]

[0056] S32 constructs a plane with the straight line direction as the normal vector, takes the plane of the middle point as the reference plane, calculates the intersection of the straight line at each scanning position and the reference plane, and obtains a three-dimensional point array for straightness calculation.

[0057] In the embodiment of the present invention, a point p is constructed m id , taking the average value of the straight line direction vector The plane with the plane normal vector as the reference plane, the equation is as follows:

[0058]

[0059] Then, based on the reference plane equation and the straight line equations at all scanning positions, the intersection points of these n straight lines with the reference plane are calculated and stored in array P for subsequent guide rail straightness calculation. The equation for calculating the intersection point of a straight line and a plane is as follows:

[0060]

[0061] In the above formula, i = 1, 2, 3, ..., n, pi =(x i ,y i ,z i ) represents a point on the i-th straight line, represents the direction vector of the i-th line, p = (x, y, z) represents the intersection of the i-th line and the plane, t i represents a point p on the i-th straight line i The distance between the intersection point p, traverse all the straight lines, and put the calculated p into the array P.

[0062] S4 obtains a reference straight line for straightness calculation based on the three-dimensional point array;

[0063] Specific method:

[0064] S41 establishes a vertical plane perpendicular to the reference plane and passing through the middle point;

[0065] In the embodiment of the present invention, in order to reduce the influence of noise points in the array P on the fitting reference straight line, a vertical plane perpendicular to the reference plane is constructed as plane 1.

[0066] S42 calculates the distance from each point in the three-dimensional point array to the vertical plane to obtain multiple sets of distance data;

[0067] In the embodiment of the present invention, the distances from all points in the array P to the plane 1 are calculated to obtain a distance array D, and the normal vector v of the plane 1 1 The normal vector of the reference plane can be and the direction vector y of the scanner movement direction nor =(0,1,0) cross product, the equation is as follows:

[0068]

[0069] S43 performs histogram statistics on the multiple groups of distance data, counts the data sizes in different distance ranges, selects the distance data with the most data, performs straight line fitting, and obtains a reference straight line for straightness calculation.

[0070] In the embodiment of the present invention, the histogram statistics of the array D can be used to obtain the distance distribution of the point to the plane 1, and the group with the largest statistical value in the current distance range is taken as the fitting reference line. 1 After normalization, we can get a point p on the reference plane. m id , with vector v 1 The equation of plane 1 as a normal vector is as follows:

[0071]

[0072] After obtaining the equation of plane 1, calculate the distance from each point in array P to plane 1. The equation is as follows:

[0073]

[0074] Where i = 1, 2, 3, ..., n, p i =(x i ,y i ,z i ) represents the i-th point in the array P, d i Represents the distance from the i-th point in array P to plane 1. The calculated d i Put it into array D.

[0075] Sort the obtained array D, and then divide the array D into ten equal parts. According to the size of the current distance d, divide different d into these ten intervals respectively, and then count the number of data in these ten intervals, extract the data in the interval with the largest number, and finally fit the reference straight line through the data. The equation of the reference straight line is as follows:

[0076]

[0077] In the above formula, p ref =(x ref ,y ref ,z ref ) represents a point on the reference line, A vector representing the direction of the reference line.

[0078] S5 calculates the distance from each point of the three-dimensional point array to the reference straight line, and subtracts the minimum value from the maximum value of the distance to obtain the straightness of the guide rail.

[0079] In an embodiment of the present invention, the distances from all points in the array P to the reference line are calculated using the following equation:

[0080]

[0081] Where i = 1, 2, 3, ..., n, p i =(x i ,y i ,z i ) represents the i-th point in array P, Represents the distance from the i-th point in array P to the reference line.

[0082] Since the distance from a point to a straight line in space has no direction, in order to determine The positive or negative value of needs to determine whether the current point is above or below the reference line. Construct a plane containing the reference line as plane 2. The normal vector v2 of plane 2 can be obtained by the normal vector of the reference plane. and the direction vector l of the reference line ref The cross product gives the following equation:

[0083]

[0084] By normalizing the vector v2, we can get the point p on the reference line re f , the plane equation with vector v2 as the normal vector of plane 2 is as follows:

[0085]

[0086] Calculate the distance from each point in array P to plane 2. The equation is as follows:

[0087]

[0088] Where i = 1, 2, 3, ..., n, p i =(x i ,y i ,z i ) represents the i-th point in array P, d represents the distance from the i-th point in array P to plane 2. By judging the positive or negative value of d, we can determine whether the current point is above or below the reference line. If d < 0, it means that the current point p i Below the reference line, let Otherwise remain unchanged.

[0089] Through the above steps, the distance between the guide rail point cloud and the reference straight line at each scanning position can be obtained. Solution Maximum value d max and the minimum value d min The difference between the straightness s of the side of the current guide rail can be obtained by the following formula:

[0090] s=d max -d min

[0091] At this point, the straightness calculation of a single surface of the guide rail is completed. The above process can only complete the straightness measurement of one surface of the guide rail. The measurement system can be configured with a guide rail flipping mechanism for expansion. By controlling the flipping mechanism to drive the guide rail to flip, the straightness calculation of the upper surface and side of the guide rail can be realized.

[0092] What is disclosed above is only a preferred embodiment of the guide rail straightness measurement method based on line laser three-dimensional scanning of the present invention. Of course, this cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A guide rail straightness measurement method based on line laser three-dimensional scanning, characterized in that: The following steps are involved: Obtain guide rail point cloud data through a line laser 3D scanner; Traversing the guide rail point cloud data, and calculating the straight line equation of each scanning position of the guide rail; Obtaining a three-dimensional point array for straightness calculation based on the straight line equation parameters; Acquire a reference straight line for straightness calculation based on the three-dimensional point array; The distance from each point in the three-dimensional point array to the reference straight line is calculated, and the minimum value of the distance is subtracted from the maximum value to obtain the straightness of the guide rail.

2. The guide rail straightness measurement method based on line laser three-dimensional scanning as claimed in claim 1, It is characterized by: The specific method of obtaining the guide rail point cloud data by using the line laser 3D scanner is: Place the high-precision linear motor and the guide rail to be measured on a marble platform, and then fix the line laser 3D scanner on the linear motor; The sampling interval of the line laser three-dimensional scanner is set, and the linear motor is controlled to drive the line laser three-dimensional scanner to collect point cloud data on the surface of the measured guide rail to obtain the guide rail point cloud data.

3. The guide rail straightness measurement method based on line laser three-dimensional scanning as claimed in claim 1, It is characterized by: The specific method of traversing the guide rail point cloud data and calculating the straight line equation of each scanning position of the guide rail is: Traversing the complete guide rail three-dimensional point cloud data; The guide rail point cloud data of each scanning position of the measured guide rail is extracted, and then straight line fitting is performed respectively to obtain the straight line equation of each scanning position.

4. The guide rail straightness measurement method based on line laser three-dimensional scanning as claimed in claim 1, It is characterized by: The specific method of obtaining the three-dimensional point array for straightness calculation based on the straight line equation parameters is as follows: Obtain the width of the guide rail to be measured and the starting point of the guide rail point cloud at each scanning position, and obtain the three-dimensional point at the middle position of the guide rail point cloud, that is, the middle point, based on the parameters of the straight line equation; A plane with the straight line direction as the normal vector is constructed, the plane of the middle point is used as the reference plane, and the intersection of the straight line at each scanning position and the reference plane is calculated to obtain a three-dimensional point array for straightness calculation.

5. The guide rail straightness measurement method based on line laser three-dimensional scanning as claimed in claim 1, It is characterized by: The specific method of obtaining the reference straight line for straightness calculation based on the three-dimensional point array is: Establishing a vertical plane perpendicular to the reference plane and passing through the middle point; Calculating the distance from each point in the three-dimensional point array to the vertical plane to obtain multiple sets of distance data; Histogram statistics are performed on multiple groups of distance data to count the data sizes in different distance ranges, and the distance data with the most data are screened out for straight line fitting to obtain a reference straight line for straightness calculation.

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