Method for measuring surface roughness of complex curved surface part

Abstract

The invention discloses a method for measuring the surface roughness of a complex curved surface part, and the method comprises the following steps: S1, importing a data model of a to-be-measured part into a five-axis roughness measurement system, and selecting a to-be-measured contour line on the surface of the data model of the to-be-measured part; s2, defining a reachable area, analyzing the interference condition of the measuring rod on the to-be-measured contour line to generate the reachable area of the measuring rod, and generating a planning path of the measuring rod according to the reachable area of the measuring rod; s3, dividing the to-be-measured contour line into a plurality of measurement sequence line segments according to the principle that the arch height error in the to-be-measured contour line does not exceed the microstroke of the measuring tip; and S4, fixing the to-be-measured part on the measuring equipment, controlling the measuring rod to work according to the planned path of the measuring rod, so that the measuring tip moves from the starting point to the end point of the to-be-measured contour line, completing the surface roughness measurement of the to-be-measured part, and outputting a measurement result. Compared with the prior art, the method can output an optimal non-interference measurement path, and achieves the high-efficiency and high-precision measurement of the surface roughness of a complex curved surface part.

Description

Technical Field

[0001] The invention relates to the field of precision measurement technology, and in particular to a method for measuring the surface roughness of a complex curved surface part. Background Art

[0002] Existing surface roughness measurement methods are divided into two categories: non-contact measurement and contact measurement. Non-contact measurement is mainly an optical measurement method, but the optical measurement method has high requirements for the surface state of the part, the light incident conditions, etc. If the surface quality of the part is too poor or the surrounding structure is blocked, it will not be able to receive effective light signals and cause measurement failure; contact measurement uses a tiny probe to contact the surface of the part and slide on the surface of the part for measurement. The contact force is small and the adaptability to the environment is strong. However, when measuring the surface roughness of complex curved parts, the probe is short and cannot rotate. It is affected by the geometric structure of the part, and the sensor may be interfered during measurement, and its measurement accessibility is limited.

[0003] At present, although there is a surface roughness measurement method based on five-axis detection technology, which combines an inductive surface roughness sensor with a five-axis rotating measuring head, it is a new method to solve the surface roughness measurement of complex curved parts, but there are also some shortcomings: 1) When measuring parts with complex structures, the flow channel between the blades is narrow and curved. If the measurement direction is selected arbitrarily, it is very likely to cause interference between the probe and the adjacent blades. Therefore, for parts with complex structures, their own geometric features form obstacles to the measured features, and it is impossible to automatically generate an interference-free measurement path to achieve rapid measurement of the surface roughness of the parts; 2) According to the definition of surface roughness, the measurement line is defined as a straight line. When measuring the surface roughness of parts with large curvature, although the curved measurement path can be converted into multiple approximate straight line segments for measurement, the measurement efficiency will be greatly reduced, and it is difficult to achieve batch measurement of parts with large curvature. Summary of the invention

[0004] The invention provides a method for measuring the surface roughness of a complex curved surface part, so as to solve the technical problem that the existing surface roughness measuring method is difficult to be applied to batch rapid measurement of complex curved surface parts with complex structures and large curvatures.

[0005] According to one aspect of the present invention, there is provided a method for measuring the surface roughness of a complex curved part, comprising the following steps: S1, importing a data model of the part to be measured into a five-axis roughness measurement system, and selecting a contour line to be measured on the surface of the data model of the part to be measured; S2, defining a reachable area, and analyzing the interference of a measuring rod on the contour line to be measured to generate a reachable area of ​​the measuring rod, and then generating a planned path of the measuring rod according to the reachable area of ​​the measuring rod; S3, dividing the contour line to be measured into a plurality of measurement sequence segments on the principle that the bow height error in the contour line to be measured does not exceed the micro-motion stroke of the measuring tip; S4, fixing the part to be measured on the measuring device, controlling the measuring rod to work according to the planned path of the measuring rod, so that the measuring tip moves from the starting point of the contour line to be measured to the end point, completing the surface roughness measurement of the part to be measured, and outputting the measurement result.

[0006] Further, in step S3, the specific steps of defining the reachable area are as follows: select any measuring point on the contour line to be measured to establish a local coordinate system, take the surface normal of the measuring point as the Z axis, take the tangent of the measuring sequence line segment of the measuring point as the X axis, and take the straight line passing through the measuring point and perpendicular to the Z axis and the X axis respectively as the Y axis; when the measuring tip axis coincides with the surface normal of the measuring point, the angle ω between the projection line of the measuring rod in the XY plane and the X axis is obtained, and then the direction of the right-hand coordinate system is taken as the positive direction of ω, then the theoretical value range of ω is [-π ,π], the theoretical value range of ω is discretized into n intervals, and the reachable area of ​​the measuring point is represented as a 1×n row vector. Any element in the row vector takes the value of 0 or 1, where 0 represents that the measuring rod interferes with the part to be measured when ω is this angle, and 1 represents that the measuring rod interferes with the part to be measured when ω is this angle; the contour line to be measured is discretized into m sampling points, so that the reachable area of ​​the measuring rod is represented as an m×n matrix, and each element of the matrix represents whether the measuring rod direction corresponding to the current measuring point is reachable with 0 or 1.

[0007] Furthermore, the specific steps for analyzing the interference of the measuring rod on the contour line to be measured are:

[0008] The direction vectors of the X-axis, Y-axis and Z-axis in the local coordinate system in the coordinate system of the part to be measured in the five-axis roughness measurement system are expressed as f = [f x ,f y ,f z ] T , k=[k x , k y , k z ] T , n=[n x , n y , n z ] T , and obtain the angle θ between the probe rod axis and the probe tip axis. The direction vector of the probe rod axis in the coordinate system of the part to be measured in the five-axis roughness measurement system is expressed as:

[0009] V p =R*V L

[0010]

[0011] Among them, V L Represents the direction vector of the measuring rod in the local coordinate system, V p The direction vector representing the measuring rod direction in the part coordinate system;

[0012] Then discretize the surface of the part to be tested into a series of triangular patches, and set the three vertices of the triangular patch to V0, V1, and V2, respectively, to obtain the expression of any point in the triangular patch as the formula:

[0013] T(u,v)=(1-uv)V0+uV1+vV2 (1)

[0014] Among them, u≥0, v≥0 and u+v≤1;

[0015] Then move the measuring rod axis with starting point O and direction V p Expressed as a formula:

[0016] R(t)=O+tV p (2)

[0017] Based on formula (1) and formula (2), the following formula is obtained through the ray-plane intersection algorithm:

[0018]

[0019] Substitute the coordinates of the measuring rod in the set direction of any measuring point on the contour line to be measured into formula (3). If formula (3) has a solution and satisfies formula (4), the measuring rod in the set direction of the measuring point is inaccessible. Otherwise, the measuring rod in the set direction of the measuring point is reachable.

[0020] Furthermore, the specific steps for generating the reachable area of ​​the measuring rod are as follows: the measuring rods in any direction corresponding to all the measuring points on the contour line to be measured are respectively substituted into formula (3), and it is determined whether formula (4) is satisfied, so as to obtain data on whether the measuring rods in any direction corresponding to any point on the contour line to be measured are reachable, thereby generating the reachable area of ​​the measuring rod.

[0021] Furthermore, generating a planned path for the measuring rod according to the reachable area of ​​the measuring rod specifically includes the following steps: detecting whether there is at least one column of elements that are all 1 in the reachable area of ​​the measuring rod; if so, selecting the measuring rod direction corresponding to the column of elements as the planned direction of the measuring rod; if not, dividing the contour line to be measured into multiple measurement lines, and ensuring that there is at least one column of elements that are all 1 in the reachable area of ​​the measuring rod corresponding to each measurement line, and selecting the measuring rod direction corresponding to the column of elements as the planned direction of the measuring rod.

[0022] Furthermore, step S3 specifically includes the following steps:

[0023] Based on the principle that the bow height error does not exceed the stylus tip micro-movement stroke, the following formula is obtained:

[0024] max d(L i )>ε,i=2,…,j-1 (5)

[0025] Among them, d(L i ) is the bow height error of the sampling point, ε is the micro-movement stroke of the probe tip;

[0026] The contour line to be measured is sampled at equal intervals to obtain multiple sampling points. Starting from the second sampling point, each sampling point is checked in turn to see if it satisfies formula (5). If so, the contour line to be measured is segmented at the current sampling point. If not, it is not segmented until the second to last sampling point is checked.

[0027] Furthermore, after the part to be measured is fixed on the measuring device, the method further includes the steps of: establishing the coordinates of the part using a conventional measuring probe, and then replacing the conventional measuring probe with a roughness measuring probe.

[0028] Furthermore, the measuring device is a coordinate measuring machine.

[0029] Furthermore, the five-axis roughness measurement system includes a three-coordinate measuring machine, a rotating measuring seat arranged on the three-coordinate measuring machine, and a roughness measuring needle arranged on the rotating measuring seat, wherein the roughness measuring needle includes a measuring rod and a measuring tip.

[0030] Furthermore, a photoelectric sensor is arranged inside the measuring rod for acquiring micro-motion signals of the measuring rod and outputting the signals to the three-dimensional coordinate measuring machine.

[0031] The present invention has the following beneficial effects:

[0032] The method for measuring the surface roughness of a complex curved surface part of the present invention imports a data model of the part to be measured into a five-axis roughness measurement system, selects a contour line to be measured on the surface of the data model of the part to be measured; defines a reachable area, and analyzes the interference of a measuring rod on the contour line to be measured to generate a reachable area of ​​the measuring rod, and then generates a planned path of the measuring rod according to the reachable area of ​​the measuring rod, so as to automatically generate an interference-free path during the measurement process; divides the contour line to be measured into a plurality of measurement sequence line segments based on the principle that the bow height error in the contour line to be measured does not exceed the micro-movement stroke of the measuring tip, so as to convert a complex curve segment into a minimum number of straight line segments, thereby improving the measurement efficiency and ensuring that the measuring rod is within the reachable area of ​​the measuring rod during the measurement process. There is no interference in the direction within the same measurement sequence line segment to adapt to the measurement of the surface roughness of parts with large curvature; the part to be measured is fixed on the measuring equipment, and the measuring rod is controlled to work according to the planned path of the measuring rod, so that the measuring tip moves from the starting point of the contour line to be measured to the end point, the surface roughness measurement of the part to be measured is completed, and the measurement result is output; compared with the prior art, this scheme can output the best interference-free measurement path by generating the reachable area of ​​the measuring rod and the reasonable division of the contour line to be measured, thereby realizing efficient and high-precision measurement of the surface roughness of complex curved surface parts, thereby being able to quickly measure batches of complex curved surface parts, with strong practicality and suitable for wide promotion and application.

[0033] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0035] Figure 1 It is a flowchart of a method for measuring the surface roughness of a complex curved surface part according to a preferred embodiment of the present invention;

[0036] Figure 2 It is a schematic diagram of establishing a local coordinate system at a measuring point when defining a reachable area in a method for measuring the surface roughness of a complex curved surface part according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0038] like Figure 1As shown, the method for measuring the surface roughness of complex curved surface parts of this embodiment includes the following steps: S1, importing the data model of the part to be measured into the five-axis roughness measurement system, and selecting the contour line to be measured on the surface of the data model of the part to be measured; S2, defining the reachable area, and analyzing the interference of the measuring rod on the contour line to be measured to generate the reachable area of ​​the measuring rod, and then generating the planned path of the measuring rod according to the reachable area of ​​the measuring rod; S3, dividing the contour line to be measured into multiple measurement sequence segments based on the principle that the bow height error in the contour line to be measured does not exceed the micro-motion stroke of the measuring tip; S4, fixing the part to be measured on the measuring equipment, controlling the measuring rod to work according to the planned path of the measuring rod, so that the measuring tip moves from the starting point of the contour line to be measured to the end point, completing the surface roughness measurement of the part to be measured, and outputting the measurement result.

[0039] like Figure 1 As shown, specifically, the method for measuring the surface roughness of a complex curved surface part of the present invention imports the data model of the part to be measured into the five-axis roughness measurement system, selects the contour line to be measured on the surface of the data model of the part to be measured; defines the reachable area, and analyzes the interference of the measuring rod on the contour line to be measured to generate the reachable area of ​​the measuring rod, and then generates the planning path of the measuring rod according to the reachable area of ​​the measuring rod, so as to realize the automatic generation of the interference-free path during the measurement process; divides the contour line to be measured into a plurality of measurement sequence line segments based on the principle that the bow height error in the contour line to be measured does not exceed the micro-movement stroke of the measuring tip, so as to convert the complex curve segments into the minimum number of straight line segments, thereby improving the measurement efficiency and ensuring the measurement process In the method, the direction of the measuring rod has no interference within the same measurement sequence line segment to adapt to the measurement of the surface roughness of parts with large curvature; the part to be measured is fixed on the measuring equipment, and the measuring rod is controlled to work according to the planned path of the measuring rod, so that the measuring tip moves from the starting point of the contour line to be measured to the end point, the surface roughness measurement of the part to be measured is completed, and the measurement result is output; compared with the prior art, this scheme can output the best interference-free measurement path by generating the reachable area of ​​the measuring rod and the reasonable division of the contour line to be measured, thereby realizing efficient and high-precision measurement of the surface roughness of complex curved surface parts, so that batches of complex curved surface parts can be quickly measured, and it is highly practical and suitable for wide promotion and application.

[0040] It should be understood that, since the present solution is mainly applied to the measurement of the surface roughness of parts with complex curved surfaces, the contour line to be measured is usually a curve.

[0041] like Figure 2As shown, in this embodiment, in step S3, the specific steps of defining the reachable area are: select any measuring point on the contour line to be measured to establish a local coordinate system, take the surface normal of the measuring point as the Z axis, take the tangent of the measurement sequence line segment of the measuring point as the X axis, and take the straight line passing through the measuring point and perpendicular to the Z axis and the X axis respectively as the Y axis; when the measuring tip axis coincides with the surface normal of the measuring point, the angle ω between the projection line of the measuring rod in the XY plane and the X axis is obtained, and then the right-hand coordinate system direction is taken as the positive direction of ω, then the theoretical value range of ω is [ -π,π], the theoretical value range of ω is discretized into n intervals, and the reachable area of ​​the measuring point is represented as a 1×n row vector, in which any element is 0 or 1, where 0 represents that the measuring rod interferes with the part to be measured when ω is this angle, and 1 represents that the measuring rod interferes with the part to be measured when ω is this angle; the contour line to be measured is discretized into m sampling points, so that the reachable area of ​​the measuring rod is represented as an m×n matrix, and each element of the matrix is ​​0 or 1 to represent whether the measuring rod direction corresponding to the current measuring point is reachable.

[0042] Specifically, by defining the reachable area, the reachable area of ​​the measuring rod is subsequently generated, and when performing roughness measurement, the reachable area of ​​the measuring rod is used to analyze the interference-free situation during the measurement process, so that there is no interference between the measuring rod and the part to be measured.

[0043] like Figure 2 As shown, in this embodiment, the specific steps of analyzing the interference of the measuring rod on the contour line to be measured are:

[0044] The direction vectors of the X-axis, Y-axis and Z-axis in the local coordinate system in the coordinate system of the part to be measured in the five-axis roughness measurement system are expressed as f = [f x , f y , f z ] T , k=[k x , k y , k z ] T , n=[n x , n y , n z ] T , and obtain the angle θ between the probe rod axis and the probe tip axis. The direction vector of the probe rod axis in the coordinate system of the part to be measured in the five-axis roughness measurement system is expressed as:

[0045] V p =R*V L

[0046]

[0047] Among them, V L Represents the direction vector of the measuring rod in the local coordinate system, V pThe direction vector representing the measuring rod direction in the part coordinate system;

[0048] Then discretize the surface of the part to be tested into a series of triangular patches, and set the three vertices of the triangular patch to V0, V1, and V2, respectively, to obtain the expression of any point in the triangular patch as the formula:

[0049] T(u,v)=(1-uv)V0+uV1+vV2 (1)

[0050] Among them, u≥0, v≥0 and u+v≤1;

[0051] Then move the measuring rod axis with starting point O and direction V p Expressed as a formula:

[0052] R(t)=O+tV p (2)

[0053] Based on formula (1) and formula (2), the following formula is obtained through the ray-plane intersection algorithm:

[0054]

[0055] Substitute the coordinates of the measuring rod in the set direction of any measuring point on the contour line to be measured into formula (3). If formula (3) has a solution and satisfies formula (4), the measuring rod in the set direction of the measuring point is inaccessible. Otherwise, the measuring rod in the set direction of the measuring point is reachable.

[0056] Specifically, a coordinate system is established to construct a mathematical model for the axis of the measuring rod and the surface of the part to be measured, and an intersection operation is performed to determine the interference between the measuring rod and the part to be measured.

[0057] In this embodiment, the specific steps for generating the reachable area of ​​the measuring rod are as follows: the measuring rods in any direction corresponding to all the measuring points on the contour line to be measured are respectively substituted into formula (3), and it is determined whether formula (4) is satisfied, so as to obtain data on whether the measuring rod in any direction corresponding to any point on the contour line to be measured is reachable, thereby generating the reachable area of ​​the measuring rod.

[0058] Specifically, after the reachable area is defined in the measurement system, the reachable area of ​​the measuring rod is generated by performing an intersection operation on the axis of the measuring rod and the surface of the part to be measured, so as to improve data support for the subsequent generation of the planning path of the measuring rod.

[0059] In this embodiment, generating a planned path for the measuring rod according to the reachable area of ​​the measuring rod specifically includes the following steps: detecting whether there is at least one column of elements that are all 1 in the reachable area of ​​the measuring rod; if so, selecting the measuring rod direction corresponding to the column of elements as the planned direction of the measuring rod; if not, dividing the contour line to be measured into multiple measurement lines, and ensuring that there is at least one column of elements that are all 1 in the reachable area of ​​the measuring rod corresponding to each measurement line, and selecting the measuring rod direction corresponding to the column of elements as the planned direction of the measuring rod.

[0060] Specifically, it is determined whether the contour line to be measured needs to be divided according to the reachable area of ​​the measuring rod, so as to ensure that there is no interference between the measuring rod and the part to be measured during the roughness measurement.

[0061] In this embodiment, step S3 specifically includes the following steps:

[0062] Based on the principle that the bow height error does not exceed the stylus tip micro-movement stroke, the following formula is obtained:

[0063] max d(L i )>ε,i=2,…,j-1 (5)

[0064] Among them, d(L i ) is the bow height error of the sampling point, ε is the micro-movement stroke of the probe tip;

[0065] The contour line to be measured is sampled at equal intervals to obtain multiple sampling points. Starting from the second sampling point, each sampling point is checked in turn to see if it satisfies formula (5). If so, the contour line to be measured is segmented at the current sampling point. If not, it is not segmented until the second to last sampling point is checked.

[0066] Specifically, by dividing the contour line to be measured into multiple measurement sequence segments to ensure that there is no interference in the direction of the measuring rod within the same measurement sequence segment, and based on the principle that the bow height error does not exceed the micro-motion stroke of the measuring tip, the number of measurement sequence segments can be minimized, thereby maximizing the measurement efficiency.

[0067] It should be understood that j is the sequence number of the last sampling point, and i is the sequence number of the current sampling point.

[0068] In this embodiment, after the part to be measured is fixed on the measuring device, the method further includes the steps of: using a conventional measuring probe to establish the coordinates of the part, and then replacing the conventional measuring probe with a roughness measuring probe.

[0069] In this embodiment, the measuring device is a three-dimensional coordinate measuring machine, which is used to quickly establish a part coordinate system and a local coordinate system of a measuring point, thereby quickly generating a reachable area of ​​a measuring rod to plan an optimal measuring path.

[0070] In this embodiment, the five-axis roughness measurement system includes a three-coordinate measuring machine, a rotating measuring seat arranged on the three-coordinate measuring machine, and a roughness measuring needle arranged on the rotating measuring seat, and the roughness measuring needle includes a measuring rod and a measuring tip. Specifically, after the part to be measured is fixed on the table of the three-coordinate measuring machine, the axis of the measuring tip coincides with the normal direction of the measured point, and the measuring tip lightly touches the measured curved surface and is kept in contact with the measured surface by the measuring machine to produce a slight deformation.

[0071] In this embodiment, a photoelectric sensor is arranged inside the measuring rod to obtain the micro-motion signal of the measuring rod and output it to the three-dimensional coordinate measuring machine. Specifically, when the measuring tip moves on the measured surface of the part to be measured, its micro-motion up and down can reflect the fluctuation of the part surface. After the micro-motion signal is obtained by the photoelectric sensor inside the measuring rod, the microscopic morphology information of the part surface can be output, and the measurement result can be generated by the three-dimensional coordinate measuring machine.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the surface roughness of a complex curved surface part, characterized in that: The following steps are involved: S1, importing the data model of the part to be measured into the five-axis roughness measurement system, and selecting the contour line to be measured on the surface of the data model of the part to be measured; S2, defining a reachable area, and analyzing the interference of the measuring rod on the contour line to be measured to generate a reachable area of ​​the measuring rod, and then generating a planned path of the measuring rod according to the reachable area of ​​the measuring rod; S3, dividing the contour line to be measured into a plurality of measurement sequence line segments based on the principle that the bow height error in the contour line to be measured does not exceed the micro-movement stroke of the measuring tip; S4, fix the part to be measured on the measuring device, control the measuring rod to work according to the planned path of the measuring rod, so that the measuring tip moves from the starting point to the end point of the contour line to be measured, complete the surface roughness measurement of the part to be measured, and output the measurement result.

2. The method for measuring the surface roughness of complex curved parts according to claim 1, characterized in that: In step S3, the specific steps of defining the reachable area are: Select any measuring point on the contour line to be measured to establish a local coordinate system, with the surface normal of the measuring point as the Z axis, the tangent of the measuring sequence line segment of the measuring point as the X axis, and the straight line passing through the measuring point and perpendicular to the Z axis and the X axis respectively as the Y axis; When the axis of the stylus tip coincides with the surface normal of the measuring point, the included angle ω between the projection line of the stylus rod in the XY plane and the X-axis is obtained. The direction of the right-hand coordinate system is taken as the positive direction of ω, and the theoretical value range of ω is [-π,π]. The theoretical value range of ω is discretized into n intervals, and the reachable area of ​​the measuring point is represented as a 1×n row vector. Any element in the row vector takes the value of 0 or 1, where 0 represents that the stylus rod interferes with the part to be measured when ω is this angle, and 1 represents that the stylus rod interferes with the part to be measured when ω is this angle. The contour line to be measured is discretely represented as m sampling points, so that the reachable area of ​​the measuring rod is represented as an m×n matrix, and each element of the matrix represents whether the measuring rod direction corresponding to the current measuring point is reachable with 0 or 1.

3. The method for measuring the surface roughness of a complex curved surface part according to claim 2, characterized in that: The specific steps for analyzing the interference of the measuring rod on the contour line to be measured are: The direction vectors of the X-axis, Y-axis and Z-axis in the local coordinate system in the coordinate system of the part to be measured in the five-axis roughness measurement system are expressed as f = [f x , f y , f z ] T , k=[k x , k y , k z ] T , n=[n x , n y , n z ] T , and obtain the angle θ between the probe rod axis and the probe tip axis. The direction vector of the probe rod axis in the coordinate system of the part to be measured in the five-axis roughness measurement system is expressed as: V p =R*V L Among them, V L Represents the direction vector of the measuring rod in the local coordinate system, V p The direction vector representing the measuring rod direction in the part coordinate system; Then discretize the surface of the part to be tested into a series of triangular patches, and set the three vertices of the triangular patch to V0, V1, and V2, respectively, to obtain the expression of any point in the triangular patch as the formula: T(u,v)=(1-uv)V0+uV1+vV2 (1) Among them, u≥0, v≥0 and u+v≤1; Then move the measuring rod axis with starting point O and direction V p Expressed as a formula: R(t)=O+tV p (2) Based on formula (1) and formula (2), the following formula is obtained through the ray-plane intersection algorithm: Substitute the coordinates of the measuring rod in the set direction of any measuring point on the contour line to be measured into formula (3). If formula (3) has a solution and satisfies formula (4), the measuring rod in the set direction of the measuring point is inaccessible. Otherwise, the measuring rod in the set direction of the measuring point is reachable.

4. The method for measuring the surface roughness of a complex curved surface part according to claim 3, characterized in that: The specific steps to generate the reachable area of ​​the measuring rod are: Substitute the measuring rods in any direction corresponding to all measuring points on the contour line to be measured into formula (3) respectively, and judge whether formula (4) is satisfied, so as to obtain data on whether the measuring rod in any direction corresponding to any point on the contour line to be measured is reachable, thereby generating the reachable area of ​​the measuring rod.

5. The method for measuring the surface roughness of a complex curved surface part according to claim 4, characterized in that: Generating a planned path of the measuring rod according to the reachable area of ​​the measuring rod specifically includes the following steps: Check whether there is at least one column of elements that are all 1 in the reachable area of ​​the measuring rod. If so, select the measuring rod direction corresponding to the column of elements as the planned direction of the measuring rod. If not, divide the contour line to be measured into multiple measurement lines, and ensure that there is at least one column of elements that are all 1 in the reachable area of ​​the measuring rod corresponding to each measurement line, and select the measuring rod direction corresponding to the column of elements as the planned direction of the measuring rod.

6. The method for measuring the surface roughness of a complex curved surface part according to any one of claims 1 to 4, characterized in that: Step S3 specifically includes the following steps: Based on the principle that the bow height error does not exceed the stylus tip micro-movement stroke, the following formula is obtained: max d(L i )>ε,i=2,…,j-1 (5) Among them, d(L i ) is the bow height error of the sampling point, ε is the micro-movement stroke of the probe tip; The contour line to be measured is sampled at equal intervals to obtain multiple sampling points. Starting from the second sampling point, each sampling point is checked in turn to see if it satisfies formula (5). If so, the contour line to be measured is segmented at the current sampling point. If not, it is not segmented until the second to last sampling point is checked.

7. The method for measuring the surface roughness of a complex curved surface part according to any one of claims 1 to 4, characterized in that: After the part to be tested is fixed on the measuring device, the following steps are also included: Use a conventional stylus to establish the coordinates of the part, then replace the conventional stylus with a roughness stylus.

8. The method for measuring the surface roughness of a complex curved surface part according to any one of claims 1 to 4, characterized in that: The measuring equipment is a three-dimensional coordinate measuring machine.

9. The method for measuring the surface roughness of a complex curved surface part according to any one of claims 1 to 4, characterized in that: The five-axis roughness measurement system includes a three-coordinate measuring machine, a rotating measuring head arranged on the three-coordinate measuring machine, and a roughness measuring needle arranged on the rotating measuring head, wherein the roughness measuring needle includes a measuring rod and a measuring tip.

10. The method for measuring the surface roughness of a complex curved surface part according to claim 1, characterized in that: A photoelectric sensor is arranged inside the measuring rod to obtain the micro-motion signal of the measuring rod and output it to the three-coordinate measuring machine.

Images