Normal detection method for curved surface workpiece

Abstract

The invention discloses a curved-surface workpiece normal detection method, which comprises a laser scanning sensor and a curved-surface workpiece, the laser scanning sensor is connected with a three-way driving mechanism and is used for driving the laser scanning sensor to move along an X / Y / Z axis, and the method specifically comprises the following steps: a controller controls the three-way driving mechanism to move; the laser scanning sensor is driven to circularly scan the periphery to be machined with the axis of the hole to be machined as the circle center and the set distance as the radius r, and circumferential line data information is obtained; and the controller recognizes data values with obvious abnormities in the distance data on the z axis, recognizes abnormal values by adopting a sliding window box graph method, and removes abnormal points. The three-way driving mechanism drives the laser scanning sensor to move to obtain data information and position information of the circumference of the to-be-formed hole site, so that the normal vector of the curved surface workpiece is accurately measured, and compared with the prior art that surface data is obtained for normal vector measurement, the data calculation amount is effectively reduced, and the measurement efficiency is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of machining technology, and in particular to a method for detecting the normal direction of curved workpieces. Background Art

[0002] In high-precision hole-making, the workpiece is often not planar. To ensure hole quality, more and more workpieces with variable curvature surfaces require real-time measurement of the normal direction. Traditional normal measurement methods use a four-point method, where four laser displacement sensors simultaneously acquire distance information from four points and quickly calculate the normal deviation. However, due to the complex surface structure of the workpiece and the presence of numerous interfering objects, the traditional four-point method cannot identify objects that happen to be located on them, leading to measurement errors and affecting machining accuracy. As an improvement, existing technologies employ a line laser scanning normal measurement method. This method obtains surface data, allowing for the identification and automatic removal of interfering objects, thus ensuring measurement accuracy. However, the large amount of data and long computation time affect measurement efficiency. Summary of the Invention

[0003] To address the above problems, this invention proposes a method for detecting the normal direction of curved workpieces. Specifically, the following technical solution is adopted: This includes a laser scanning sensor and a curved workpiece. The laser scanning sensor is connected to a three-axis drive mechanism to drive the laser scanning sensor to move along the X / Y / Z axes. The specific steps include: 1) The controller controls the movement of the three-way drive mechanism, which drives the laser scanning sensor to perform a circular scan around the hole to be processed with the axis of the hole as the center and a set distance as the radius r, to obtain circumferential line data information; 2) The controller identifies obvious abnormal data values ​​in the distance data on the z-axis, and uses the sliding window box plot method to identify and remove outliers; 3) The controller uses the least squares method to fit the parameters of the plane ellipse, thereby identifying and removing interference points contained in the circumferential line data. 4) The controller uses the singular value decomposition method to fit the plane where the workpiece is located. By performing singular value decomposition on the coordinate matrix of the point to be fitted after centroid removal, the plane parameters are obtained and the normal information of the hole to be made is obtained.

[0004] Further, step 1) specifically includes: the laser scanning sensor performs circular motion on the plane with a radius of r, taking the center of the circle as the origin O, and marking points on the horizontal x-axis at intervals of length s. Points are marked from left to right on the upper half of the circle, resulting in a sequence of spatial coordinate points. The sequence of spatial coordinate points obtained by marking dots from right to left on the lower semicircle is as follows: This allows us to obtain information on 2N data points on the circumference.

[0005] Furthermore, in step 2) of The number of outliers is marked as K.

[0006] Further, the number of interference points in step 3) is denoted as H.

[0007] Furthermore, when 2r / s is an integer, When 2r / s is not an integer, That is, the floor value of 2r / s.

[0008] Furthermore, the data Divide according to a fixed window size T to obtain Given a data segment, calculate the first quartile of each data segment. and the third and fourth quartiles Thus, the interquartile range (IQR) is obtained. The interquartile range is used to determine the upper bound of outliers. and the lower realm They are defined as follows: ; ; Where T is the number of data points, and data points outside the upper and lower bounds are marked as outliers; K data points are marked as outliers. The corresponding coordinate points are removed from the original coordinate point sequence, thus obtaining the coordinate point sequence after outlier removal. .

[0009] Furthermore, the general form for fitting an elliptic curve using the least squares method is... , obtain parameters ; Calculate the actual coordinates of the points and the coordinates of the point on the ellipse The difference between them, i.e. Set threshold Difference sequence The standard deviation, i.e. ; in, For sequence The mean, when At that time, the point was considered an interference point; the set of coordinate points obtained after removal is... .

[0010] Furthermore, calculate the centroid of the coordinate points. : ; Translate the data points to a point where the centroid is the origin: ; For the centroid-free matrix Perform singular value decomposition: ; in: yes The left singular vector matrix; yes A diagonal matrix, where the diagonal elements are singular values. ; yes The right singular vector matrix, whose column vectors Corresponding to the main direction; normal vector of a plane Minimum singular value The corresponding right singular vector : ; Using the center of mass and normal vector Calculate coefficients : ; Thus, the equation of the plane containing the coordinate point is obtained: ; The unit normal vector of the hole to be made is then obtained as: ; in .

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention drives the laser scanning sensor to move through a three-way drive mechanism to obtain the circumferential line data and position information of the hole to be made, thereby accurately measuring the normal vector of the curved workpiece. Compared with the prior art of obtaining surface data for normal vector measurement, the present application effectively reduces the amount of data calculation and ensures measurement efficiency.

[0012] 2) This invention automatically identifies abnormal points and interference points through the algorithm of the built-in controller, ensuring the accuracy and validity of the measurement data. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the measurement principle of the laser scanning sensor of the present invention; Figure 2 This is a schematic diagram of the laser scanning sensor marking points according to the present invention; Figure 3This is a flowchart of the normal alignment process for curved workpieces according to the present invention.

[0014] In the figure: 1. Laser scanning sensor, 2. Curved workpiece. Detailed Implementation

[0015] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0016] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0017] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0018] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0019] like Figure 1 As shown, this embodiment of the invention provides a method for detecting the normal direction of a curved workpiece, including a laser scanning sensor 1, a curved workpiece 2, and a three-axis drive mechanism connected to the laser scanning sensor 1 and driving the laser scanning sensor 1 to move along the X / Y / Z axes. Specifically, the method includes the following steps: 1) The controller controls the movement of the three-way drive mechanism, which drives the laser scanning sensor 1 to perform a circular scan around the hole to be processed with the axis of the hole as the center and a set distance as the radius r, so as to obtain the circumferential line data information; Specifically, this includes: the laser scanning sensor 1 performs circular motion on a plane with a radius of r, and the center of the circle is taken as the origin O. It marks a point every length s along the horizontal x-axis, and the data obtained at each mark is the distance between the laser scanning sensor 1 and the workpiece. The trajectory of the laser scanning sensor 1's circular motion is as follows: Figure 2 As shown. Points are marked on the upper semicircle from left to right, resulting in a sequence of spatial coordinate points. When 2r / s is an integer, When 2r / s is not an integer, That is, the floor value of 2r / s. Starting point. The coordinates on the x-axis are The coordinates on the y-axis are The coordinate on the z-axis represents the distance data obtained by laser scanning sensor 1 when it hits the workpiece. Then, point by point is taken to the right in sequence until the last coordinate point of the upper part of the circular motion is obtained. Its coordinates on the x-axis are The coordinates on the y-axis are The coordinates on the z-axis represent the distance data at this point. .

[0020] Similarly, by marking points from right to left on the lower semicircle, the resulting sequence of spatial coordinate points is as follows: Starting point The coordinates on the x-axis are The coordinates on the y-axis are The coordinates on the z-axis represent distance data. Continue taking points to the left in sequence until you reach the last coordinate point of the lower half of the circular motion. Its coordinates on the x-axis are The coordinates on the y-axis are The coordinate on the z-axis represents the distance data obtained by the sensor hitting the workpiece at this moment. Thus, information on 2N data points on the circumference is obtained.

[0021] 2) The controller identifies data values ​​with obvious anomalies in the distance data on the z-axis, and uses the sliding window box plot method to identify and remove outliers; Specifically, this includes: taking into account factors such as sensor measurement anomalies, and taking appropriate measures to address any obvious anomalies in the data. For example, regarding the coordinate point sequence... If there are obvious outliers in the distance data on the z-axis, outlier handling is the first step. A sliding window box plot method is used to identify outliers. According to fixed window size (T is usually taken as 30) is divided to obtain There are several data segments; the details of each data segment are as follows: ; G represents the specific data segment interval, and l represents the number of data segments; For each data segment, a box plot method is used. Specifically, the first quartiles of the two key statistics in each data segment are calculated. and the third and fourth quartiles Thus, the interquartile range (IQR) is obtained. ; Use the interquartile range to determine the range of outliers, the upper bound ( ) and lower bound ( ) are defined as follows ; ; Where T is the number of data points, and data points outside the upper and lower bounds are marked as outliers. Data The corresponding coordinate points are removed from the original coordinate point sequence, thus obtaining the coordinate point sequence after outlier removal. .

[0022] 3) The controller uses the least squares method to fit the parameters of the plane ellipse, thereby identifying and removing interference points contained in the circumferential line data. Specifically, this includes: considering the roughness of the workpiece surface and interference from impurities, and processing the data to address potential interference. The least squares method is used to fit the parameters of the plane ellipse, thereby identifying the interference points it contains. Specifically, based on the coordinate point sequence... The general form of fitting the following elliptic curve using the least squares method is given. , obtain parameters Since the sequence of coordinate points does not all lie on the elliptic curve, it is necessary to calculate the actual coordinates of the points. and the coordinates of the point on the ellipse The difference between them, i.e. Set threshold Difference sequence The standard deviation, i.e. ; in, For sequence The mean, when At that time, the point is considered an interference point. The H marked interference points are... The set of coordinate points obtained after removal is .

[0023] 4) The controller uses the singular value decomposition method to fit the plane where the workpiece is located. By performing singular value decomposition on the coordinate matrix of the point to be fitted after centroid removal, the plane parameters are obtained and the normal information of the hole to be made is obtained.

[0024] Specifically, this includes: coordinate points on a plane in known space. .

[0025] Calculate the centroid of the coordinate point: ; Translate the data points to a point where the centroid is the origin: ; For the centroid-free matrix Perform singular value decomposition: ; in: yes The left singular vector matrix; yes A diagonal matrix, where the diagonal elements are singular values. ; yes The right singular vector matrix, whose column vectors Corresponding to the main direction; normal vector of a plane Minimum singular value The corresponding right singular vector : ; Using the center of mass and normal vector Calculate coefficients : ; Thus, the equation of the plane containing the coordinate point is obtained: ; The unit normal vector of the hole to be made is then obtained as: ; in .

[0026] In summary, the three-way drive mechanism of this invention drives the laser scanning sensor 1 to move, acquires the circumferential line data and position information of the hole to be made, thereby accurately measuring the normal vector of the curved workpiece. Compared with the prior art of acquiring surface data to measure the normal vector, this application effectively reduces the amount of data calculation and ensures measurement efficiency.

[0027] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0028] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting the normal direction of a curved workpiece, characterized in that, The device includes a laser scanning sensor and a curved workpiece. The laser scanning sensor is connected to a three-axis drive mechanism to drive the laser scanning sensor to move along the X / Y / Z axes. The specific steps include: 1) The controller controls the movement of the three-way drive mechanism, which drives the laser scanning sensor to perform a circular scan around the hole to be processed with the axis of the hole as the center and a set distance as the radius r, to obtain circumferential line data information; 2) The controller identifies obvious abnormal data values ​​in the distance data on the z-axis, and uses the sliding window box plot method to identify and remove outliers; 3) The controller uses the least squares method to fit the parameters of the plane ellipse, thereby identifying and removing interference points contained in the circumferential line data. 4) The controller uses the singular value decomposition method to fit the plane where the workpiece is located. By performing singular value decomposition on the coordinate matrix of the point to be fitted after centroid removal, the plane parameters are obtained and the normal information of the hole to be made is obtained.

2. The method for detecting the normal direction of a curved workpiece according to claim 1, characterized in that, Step 1) specifically includes: the laser scanning sensor performs circular motion on a plane with a radius of r. Taking the center of the circle as the origin O, it marks points along the horizontal x-axis at intervals of length s. Points are marked from left to right on the upper half of the circle, resulting in a sequence of spatial coordinate points. The sequence of spatial coordinate points obtained by marking dots from right to left on the lower semicircle is as follows: This allows us to obtain information on 2N data points on the circumference.

3. The method for detecting the normal direction of a curved workpiece according to claim 2, characterized in that, Step 2) In The number of outliers is marked as K.

4. The method for detecting the normal direction of a curved workpiece according to claim 3, characterized in that, The number of interference points in step 3) is marked as H.

5. The method for detecting the normal direction of a curved workpiece according to claim 2, characterized in that, When 2r / s is an integer When 2r / s is not an integer, That is, the floor value of 2r / s.

6. The method for detecting the normal direction of a curved workpiece according to claim 4, characterized in that, Data Divide according to a fixed window size T to obtain Given a data segment, calculate the first quartile of each data segment. and the third and fourth quartiles Thus, the interquartile range (IQR) is obtained. The interquartile range is used to determine the upper bound of outliers. and the lower realm They are defined as follows: ； ； Where T is the number of data points, and data points outside the upper and lower bounds are marked as outliers; K data points are marked as outliers. The corresponding coordinate points are removed from the original coordinate point sequence, thus obtaining the coordinate point sequence after outlier removal. .

7. The method for detecting the normal direction of a curved workpiece according to claim 6, characterized in that, General formula for fitting elliptic curves using the least squares method , obtain parameters ; Calculate the actual coordinates of the points and the coordinates of the point on the ellipse The difference between them, i.e. Set threshold Difference sequence The standard deviation, i.e. ； in, For sequence The mean, when At that time, the point was considered an interference point; the set of coordinate points obtained after removal is... .

8. The method for detecting the normal direction of a curved workpiece according to claim 7, characterized in that, Calculate the centroid of the coordinate point : ； Translate the data points to a point where the centroid is the origin: ； For the centroid-free matrix Perform singular value decomposition: ； in: yes The left singular vector matrix; yes A diagonal matrix, where the diagonal elements are singular values. ; yes The right singular vector matrix, whose column vectors Corresponding to the main direction; normal vector of a plane Minimum singular value The corresponding right singular vector : ； Using the center of mass and normal vector Calculate coefficients : ; Thus, the equation of the plane containing the coordinate point is obtained: ; The unit normal vector of the hole to be made is then obtained as: ； in .

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