Axle length measuring mechanism and method

Abstract

The invention relates to an axle length measuring mechanism and method. The device comprises a base; the radial measurement grating ruler is arranged on the base and extends along the radial direction of the axle to be measured; the axial driving module is used for driving the base to move the moving frame along the axial direction of the axle to be measured and is connected to the base in a sliding manner along the length direction of the radial measuring grating ruler; the axial measurement grating ruler is arranged along the axial direction of the axle to be measured; the radial driving module is mounted on the base and drives the moving frame to move; and the visual device is mounted on the movable frame. According to the axle length measuring mechanism and method, abrasion and damage to the surface of an axle caused by traditional contact type measurement are avoided, the visual device is adopted for measurement, abrasion and damage to the surface of the axle caused by traditional contact type measurement are avoided, and the axle length measuring mechanism and method are particularly suitable for measuring the length of an axle with an arc section. And the application range and precision of measurement are improved.

Description

Technical Field

[0001] The invention relates to the technical field of shaft part measurement, and in particular to an axle length measurement mechanism and method. Background Art

[0002] With the improvement of the intelligence of testing equipment, the measurement requirements of axle diameter, length, arc shape, radial runout and other dimensions can be completed automatically, efficiently and accurately.

[0003] However, the traditional contact measurement method is not suitable for measuring the length of axles with arc sections, especially the length between the journals from arc sections to arc sections or from arc sections to non-arc sections. The traditional measurement method usually relies on a three-coordinate measuring machine or manual operation. Although this method can provide higher measurement accuracy, its equipment cost is high and the operation is complicated, which is not conducive to achieving efficient automated measurement. Summary of the invention

[0004] To this end, the present invention provides an axle length measuring mechanism and method, which avoids the wear and damage to the axle surface caused by traditional contact measurement, is suitable for measuring the length of an axle with an arc cross-section, and improves the applicable scope and accuracy of the measurement.

[0005] In order to solve the above technical problems, the present invention provides an axle length measuring mechanism, which is arranged on one side of an axle to be measured during measurement. The axle to be measured includes an axle body and a first journal and a second journal respectively connected to both ends of the axle body. The axle length measuring mechanism includes: Pedestal; A radial measuring grating ruler is arranged on the base and extends along the radial direction of the axle to be measured; An axial drive module drives the base to move along the axial direction of the axle to be tested; An axial measuring grating ruler is arranged along the axial direction of the axle to be measured; A movable frame is slidably connected to the base along the length direction of the radial measuring grating ruler; A radial driving module is installed on the base and drives the moving frame to move; The visual device is installed on the mobile frame.

[0006] In one embodiment of the present invention, the radial drive module comprises: A screw seat, mounted on the base; A lead screw, rotatably connected to the lead screw seat and arranged parallel to the radial measuring grating ruler; A slide rail, mounted on the base and arranged parallel to the lead screw; A nut, slidably connected to the lead screw; A slider, connected to the nut and the movable frame respectively and slidably connected to the slide rail; A power assembly is used to drive the lead screw to rotate.

[0007] In one embodiment of the present invention, the power assembly includes a servo drive motor, a first synchronous wheel is installed at the driving end of the servo drive motor, a second synchronous wheel is installed at the end of the lead screw, and a synchronous belt is connected between the first synchronous wheel and the second synchronous wheel.

[0008] In one embodiment of the present invention, a grating reading head that cooperates with the radial measuring grating scale is installed on the slider.

[0009] In one embodiment of the present invention, a photoelectric switch for detecting the position of the slider is installed on one side of the slide rail on the base.

[0010] In one embodiment of the present invention, the movable frame is arranged across the radial sides of the axle to be tested, and the visual device includes a visual camera and a parallel light source respectively installed at both ends of the movable frame, and the visual camera and the parallel light source are arranged opposite to each other and located on the radial sides of the axle to be tested.

[0011] In one embodiment of the present invention, the movable frame is installed with a lens holder and a light source cover, the lens holder is installed with a telecentric lens connected to the visual camera, and the light source cover is arranged to cover the parallel light source.

[0012] In one embodiment of the present invention, the axial drive module includes a servo linear module.

[0013] The present invention also provides a method for measuring the length of an axle, using the axle length measuring mechanism, the method comprising: The visual device moves to one radial side of the first journal to obtain the first radial grating scale coordinate system position, the first axial grating scale coordinate system position and the first visual coordinate system position of the first intersection; the visual device moves to the other radial side of the first journal to obtain the second radial grating scale coordinate system position, the second axial grating scale coordinate system position and the second visual coordinate system position of the second intersection; wherein the first intersection and the second intersection are respectively corresponding to the connection points of the first journal and the axle body on both radial sides of the first journal; Determine the world coordinate system position of the first intersection point according to the first radial grating scale coordinate system position, the first axial grating scale coordinate system position and the first visual coordinate system position, and determine the world coordinate system position of the second intersection point according to the second radial grating scale coordinate system position, the second axial grating scale coordinate system position and the second visual coordinate system position; The visual device moves to one radial side of the second journal to obtain the third radial grating scale coordinate system position, the third axial grating scale coordinate system position and the third visual coordinate system position of the third intersection. The visual device moves to the other radial side of the second journal to obtain the fourth radial grating scale coordinate system position, the fourth axial grating scale coordinate system position and the fourth visual coordinate system position of the fourth intersection; wherein the third intersection and the fourth intersection are respectively the connection points of the second journal and the axle body corresponding to the radial sides of the second journal; Determine the world coordinate system position of the third intersection point according to the third radial grating scale coordinate system position, the third axial grating scale coordinate system position and the third visual coordinate system position, and determine the world coordinate system position of the fourth intersection point according to the fourth radial grating scale coordinate system position, the fourth axial grating scale coordinate system position and the fourth visual coordinate system position; Acquire a first line segment between the first visual coordinate system position and the second visual coordinate system position, and a second line segment between the third visual coordinate system position and the fourth visual coordinate system position; The length of the axle body is obtained according to the length of a perpendicular line from the midpoint of the first line segment to the second line segment.

[0014] In one embodiment of the present invention, the line types on both sides of the connection between the first journal and the second journal and the axle body are extracted by the visual device, and the line types are arcs and / or straight lines.

[0015] The above technical solution of the present invention has the following advantages compared with the prior art: The axle length measuring mechanism and method described in the present invention adopts a visual device for measurement, thereby avoiding the wear and damage to the axle surface caused by traditional contact measurement, and is particularly suitable for measuring the length of axles with arc cross-sections, thereby improving the applicable scope and accuracy of the measurement. By integrating axial and radial measuring grating scales, axial and radial drive modules, visual devices and other components, fully automated measurement of axle length is achieved. The visual device can move quickly at different positions, and in conjunction with the position feedback of the axial and radial measuring grating scales, it can quickly and continuously obtain measurement data, greatly improving measurement efficiency and reducing manual intervention and errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0017] Figure 1 It is a schematic diagram of the overall structure of the axle length measuring mechanism of the present invention from a side perspective.

[0018] Figure 2It is a schematic diagram of the overall structure of the axle length measuring mechanism of the present invention from another side perspective.

[0019] Figure 3 It is a structural schematic diagram of the radial drive module of the present invention.

[0020] Figure 4 It is a structural schematic diagram of the shell of the present invention.

[0021] Figure 5 It is a schematic diagram of the structure of the axle length measuring mechanism of the present invention when arranged during testing.

[0022] Figure 6 It is a structural schematic diagram of the axle measuring device of the present invention.

[0023] Description of the Figures in the Specification: 100, axle to be tested; 110, axle body; 120, first journal; 130, second journal; 1. Base; 11. Photoelectric switch; 12. Housing; 2. Radial measuring grating ruler; 21. Grating reading head; 3. Radial drive module; 31. Screw seat; 32. Screw; 33. Slide rail; 34. Screw nut; 35. Sliding block; 36. Servo drive motor; 37. First synchronous wheel; 38. Second synchronous wheel; 39. Synchronous belt; 4. Mobile rack; 5. Axial drive module; 6. Visual device; 61. Visual camera; 62. Parallel light source; 63. Lens holder; 64. Light source cover; 65. Telecentric lens; 7. Axial measurement grating ruler. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0025] In the present invention, if directions (up, down, left, right, front and back) are described, it is only for the convenience of describing the technical solution of the present invention, and does not indicate or imply that the technical features referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention.

[0026] In the present invention, "several" means one or more, "multiple" means more than two, "greater than", "less than", "exceed" and the like are understood to exclude the number itself; "above", "below", "within" and the like are understood to include the number itself. In the description of the present invention, if there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0027] In the present invention, unless otherwise clearly defined, the words "set", "install", "connect" and the like should be understood in a broad sense, for example, they can be directly connected or indirectly connected through an intermediate medium; they can be fixedly connected or detachably connected or integrally formed; they can be mechanically connected or electrically connected or able to communicate with each other; they can be the internal connection of two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0028] Reference Figure 1 , Figure 2 As shown, an axle length measuring mechanism of the present invention is arranged on one side of an axle 100 to be measured during measurement. The axle 100 to be measured includes an axle body 110 and a first journal 120 and a second journal 130 respectively connected to both ends of the axle body 110. The axle length measuring mechanism includes: Base 1; A radial measuring grating ruler 2 is arranged on the base 1 and extends along the radial direction of the axle 100 to be measured; An axial driving module 5 drives the base 1 to move along the axial direction of the axle 100 to be tested; An axial measuring grating ruler 7 is arranged along the axial direction of the axle 100 to be measured; A movable frame 4 is slidably connected to the base 1 along the length direction of the radial measuring grating ruler 2; A radial driving module 3 is installed on the base 1 and drives the moving frame 4 to move; The visual device 6 is installed on the mobile frame 4.

[0029] By arranging the measuring mechanism on one side of the axle, the convenience of equipment installation and use is ensured, while the occupied space is reduced. The base 1 provides a stable support, the radial measuring grating scale 2 extends along the radial direction of the (axle to be measured 100), and the axial measuring grating scale 7 extends along the axial direction of the (axle to be measured 100), which helps to accurately measure the length change. The design of the axial drive module 3 and the radial drive module 5 are responsible for the movement of the base 1 and the mobile frame 4 respectively, so that the measuring mechanism can move flexibly in the axial and radial directions of the axle, enhancing the flexibility and range coverage of the measurement. The visual device 6 enables the system to obtain the characteristic image of the axle in real time, and then perform precise measurement, which significantly improves the accuracy and efficiency of the measurement.

[0030] In one embodiment, referring to Figure 3 As shown, the radial drive module 3 includes: A screw seat 31 is mounted on the base 1; A lead screw 32, rotatably connected to the lead screw seat 31 and arranged parallel to the radial measuring grating ruler 2; A slide rail 33, mounted on the base 1 and arranged parallel to the lead screw 32; A nut 34, slidably connected to the lead screw 32; A slider 35, connected to the nut 34 and the moving frame 4 respectively and slidably connected to the slide rail 33; The power assembly is used to drive the lead screw 32 to rotate.

[0031] Specifically, the power assembly includes a servo drive motor 36 , a first synchronous wheel 37 is installed at the driving end of the servo drive motor 36 , a second synchronous wheel 38 is installed at the end of the lead screw 32 , and a synchronous belt 39 is connected between the first synchronous wheel 37 and the second synchronous wheel 38 .

[0032] By adopting the combination of (ball) screw 32 and slide rail 33, precise linear motion control is achieved. The screw 32 structure can effectively reduce friction and provide high-precision positioning, while the design of the slide rail 33 ensures the smoothness and reliability of movement. The power assembly drives the screw 32 to rotate, thereby driving the linear movement of the nut 34 and the slider 35. This structure can achieve precise axial positioning in a small space and is suitable for measurement scenarios that require high precision and high stability.

[0033] In one embodiment, referring to Figure 2 As shown, a grating reading head 21 cooperating with the radial measuring grating ruler 2 is installed on the slider 35. In addition, a reading head cooperating with the axial driving module 5 is also installed on the base 1.

[0034] In one embodiment, a photoelectric switch 11 for detecting the position of the slider 35 is installed on one side of the slide rail 33 on the base 1 .

[0035] In one embodiment, referring to Figure 5 As shown, the movable frame 4 is arranged across the radial sides of the axle 100 to be tested, and the visual device 6 includes a visual camera 61 and a parallel light source 62 respectively installed at both ends of the movable frame 4, and the visual camera 61 and the parallel light source 62 are arranged opposite to each other and located on the radial sides of the axle 100 to be tested.

[0036] A vision camera 61 is an industrial digital camera used to capture images. It can convert the physical features of an object (such as shape, color, texture) into digital image data. Its core components usually include image sensors (such as CCD or CMOS sensors), lenses, image processing chips, etc.

[0037] The telecentric lens 65 is a special industrial lens. The telecentric lens 65 is a lens with a constant magnification within a certain working distance range. The image size obtained by the telecentric lens 65 will not change with the displacement of the object.

[0038] The visual device 6 (visual camera 61) is used to extract the two sides of the connection between the first journal 120 and the second journal 130 and the axle body 110 ( Figure 6 a) and b) line type, the line type is an arc and / or a straight line.

[0039] In one embodiment, referring to Figure 1 As shown, the movable frame 4 is installed with a lens bracket 63 and a light source cover 64 , the lens bracket 63 is installed with a telecentric lens 65 connected to the visual camera 61 , and the light source cover 64 is covered by the parallel light source 62 .

[0040] The visual device 6 (including the visual camera 61 and the telecentric lens 65) is installed on the mobile frame 4, and can take pictures and perform image analysis on different parts of the axle. Through the image processing algorithm, the visual device 6 can extract the image of each feature on the axle.

[0041] By combining the visual camera 61 with the radial measuring grating ruler 2 and the axial measuring grating ruler 7, the characteristic points of different parts of the axle (such as the connection point between the journal and the axle body 110, Figure 6 The axle length can be measured with high precision, ensuring the accuracy and consistency of the measurement.

[0042] In one embodiment, referring to Figure 5As shown, the axial drive module 5 includes a servo linear module.

[0043] In addition, the length measurement mechanism is equipped with a master controller (such as an industrial PC or PLC) to ensure the synchronous operation of the vision system, motion control system and data acquisition system.

[0044] Reference Figure 4 As shown, in order to protect the internal components, a shell 12 matched with the base 1 is also provided, and the shell 12 can cover various devices, leaving only the mobile frame 4 and the visual device 6 extended.

[0045] This embodiment also provides a method for measuring the length of an axle, using the axle length measuring mechanism, the method comprising: S1, the visual device 6 moves to one radial side of the first journal 120, obtains the first radial grating scale coordinate system position, the first axial grating scale coordinate system position and the first visual coordinate system position of the first intersection, and the visual device 6 moves to the other radial side of the first journal 120, obtains the second radial grating scale coordinate system position, the second axial grating scale coordinate system position and the second visual coordinate system position of the second intersection; wherein the first intersection and the second intersection correspond to the connection points of the first journal 120 and the axle body 110 on both radial sides of the first journal 120; S2, determining the world coordinate system position of the first intersection point according to the first radial grating scale coordinate system position, the first axial grating scale coordinate system position and the first visual coordinate system position, and determining the world coordinate system position of the second intersection point according to the second radial grating scale coordinate system position, the second axial grating scale coordinate system position and the second visual coordinate system position; S3, the visual device 6 moves to one radial side of the second journal 130, obtains the third radial grating scale coordinate system position, the third axial grating scale coordinate system position and the third visual coordinate system position of the third intersection, and the visual device 6 moves to the other radial side of the second journal 130, obtains the fourth radial grating scale coordinate system position, the fourth axial grating scale coordinate system position and the fourth visual coordinate system position of the fourth intersection; wherein the third intersection and the fourth intersection correspond to the connection points of the second journal 130 and the axle body 110 on both radial sides of the second journal 130, respectively; S4, determining the world coordinate system position of the third intersection according to the third radial grating scale coordinate system position, the third axial grating scale coordinate system position and the third visual coordinate system position, and determining the world coordinate system position of the fourth intersection according to the fourth radial grating scale coordinate system position, the fourth axial grating scale coordinate system position and the fourth visual coordinate system position; S5, acquiring a first line segment between the first visual coordinate system position and the second visual coordinate system position, and a second line segment between the third visual coordinate system position and the fourth visual coordinate system position; S6. Obtain the length of the axle body 110 according to the length of a perpendicular line from the midpoint of the first line segment to the second line segment.

[0046] The specific operation is as follows: at the beginning of the measurement, the visual device 6 moves to the leftmost side of the axle. Then, the axial drive module 3 moves the visual device 6 to the first journal 120 on the left side of the length of the axle 100 to be measured, and records the reading of the axial measurement grating ruler 7 at this time to obtain the grating X coordinate; The visual camera 61 is driven up and down by the radial driving module 5 to ensure that the visual camera 61 can cover the top of the axle 100 to be measured, and the reading of the radial measuring grating ruler 2 is recorded at this time to obtain the grating Z coordinate; If there is a chamfer (arc) on one side of the measured journal, first extract the arc curve on the chamfered side (arc side) of the journal, and then extract the straight line on the other side of the journal; If there is no chamfer (arc) on one side of the measured journal, directly extract the vertical line on that side, and then extract the line to the other side of the journal; The (first and second) intersections of the extracted arc curve (or straight line) and the straight line are calculated. Given the resolution of the industrial camera, the visual coordinate system positions of these intersections (including the visual coordinate system X and Z coordinates of the intersections) are determined; the world coordinate system X coordinate of the intersection can be determined based on the grating X coordinate and the visual coordinate system X coordinate, and the world coordinate system Z coordinate of the intersection can be determined based on the grating Z coordinate and the visual coordinate system Z coordinate.

[0047] The radial drive module 5 drives the visual camera 61 to move downward so that the visual camera 61's field of view can include the bottom of the axle 100 to be measured, and the reading of the grating reading head 21 is recorded again; Perform feature extraction again on the arc side (if any) and the straight side of the journal. According to the intersection position in the camera coordinate system and the radial and axial grating scale coordinate system positions, convert the intersection position in the world coordinate system, and connect the two intersection points measured above and below into a line segment (the first line segment). Repeat the above steps, perform the same measurement and recording operations on the second journal 130 on the right side, obtain the corresponding grating position and the intersection point in the world coordinate system, and connect them into another line segment (the second line segment).

[0048] Finally, draw a perpendicular line from the midpoint of the first line segment (midpoint coordinates) to the second line segment, and determine the length of the measured axle based on the length of this perpendicular line (the distance between the midpoint coordinates of the first line segment and the midpoint coordinates of the second line segment).

[0049] It should be understood that the visual coordinate system is a coordinate system defined by the visual device 6 (industrial camera). It is usually based on the pixel coordinates of the camera sensor and is used to describe the relative position of objects in the image captured by the camera. The grating scale coordinate system is a coordinate system defined by the grating scale. The world coordinate system is a fixed, global reference coordinate system used to describe the absolute position in the entire measurement system. All measurement results must eventually be converted to this coordinate system to ensure the uniformity and consistency of the measurement data.

[0050] In this embodiment, the relationship between the visual coordinate system, the grating scale coordinate system and the world coordinate system is pre-calibrated by establishing a conversion relationship between different coordinate systems. By converting the measurement position in the visual coordinate system and the measurement position in the grating scale coordinate system into the position in the world coordinate system, it is ensured that all measurements are performed in the same coordinate system, thereby ensuring the consistency and accuracy of the measurement results.

[0051] The measuring method of the present invention can handle axles of different shapes and features, including the length measurement between axle necks from arc sections to arc sections or from arc sections to non-arc sections. It is suitable for axles of various complex shapes and can adapt to axles of different diameters and lengths, and has a wide range of applications.

[0052] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An axle length measuring mechanism, which is arranged on one side of an axle (100) to be measured during measurement, wherein the axle (100) to be measured comprises an axle body (110) and a first journal (120) and a second journal (130) respectively connected to two ends of the axle body (110), characterized in that: The axle length measuring mechanism comprises: Base (1); A radial measuring grating ruler (2) is arranged on the base (1) and extends along the radial direction of the axle (100) to be measured; An axial drive module (5) drives the base (1) to move along the axial direction of the axle (100) to be tested; An axial measurement grating ruler (7) is arranged along the axial direction of the axle (100) to be measured; A movable frame (4) is slidably connected to the base (1) along the length direction of the radial measuring grating ruler (2); A radial drive module (3) is mounted on the base (1) and drives the movable frame (4) to move; A visual device (6) is installed on the movable frame (4).

2. The axle length measuring mechanism according to claim 1, characterized in that: The radial drive module (3) comprises: A screw seat (31) mounted on the base (1); A lead screw (32) rotatably connected to the lead screw seat (31) and arranged parallel to the radial measuring grating scale (2); A slide rail (33) mounted on the base (1) and arranged parallel to the lead screw (32); A nut (34) slidably connected to the lead screw (32); A sliding block (35) connected to the nut (34) and the movable frame (4) respectively and slidably connected to the sliding rail (33); A power assembly is used to drive the lead screw (32) to rotate.

3. The axle length measuring mechanism according to claim 2, characterized in that: The power assembly comprises a servo drive motor (36), a driving end of the servo drive motor (36) is mounted with a first synchronous wheel (37), an end of the lead screw (32) is mounted with a second synchronous wheel (38), and a synchronous belt (39) is connected between the first synchronous wheel (37) and the second synchronous wheel (38).

4. The axle length measuring mechanism according to claim 3, characterized in that: The slider (35) is provided with a grating reading head (21) that cooperates with the radial measuring grating ruler (2).

5. The axle length measuring mechanism according to claim 2, characterized in that: A photoelectric switch (11) for detecting the position of the slider (35) is installed on the base (1) on one side of the slide rail (33).

6. The axle length measuring mechanism according to claim 1, characterized in that: The movable frame (4) is arranged across two radial sides of the axle (100) to be tested, and the visual device (6) comprises a visual camera (61) and a parallel light source (62) respectively mounted at two ends of the movable frame (4), and the visual camera (61) and the parallel light source (62) are arranged opposite to each other and are located on two radial sides of the axle (100) to be tested.

7. The axle length measuring mechanism according to claim 6, characterized in that: The movable frame (4) is mounted with a lens support (63) and a light source cover (64); the lens support (63) is mounted with a telecentric lens (65) connected to the visual camera (61); and the light source cover (64) covers the parallel light source (62).

8. The axle length measuring mechanism according to claim 1, characterized in that: The axial drive module (5) comprises a servo linear module.

9. A method for measuring axle length, characterized in that: Utilizing the axle length measuring mechanism according to any one of claims 1 to 8, the method comprises: The visual device (6) moves to one radial side of the first journal (120) to obtain a first radial grating scale coordinate system position, a first axial grating scale coordinate system position and a first visual coordinate system position of a first intersection; the visual device (6) moves to the other radial side of the first journal (120) to obtain a second radial grating scale coordinate system position, a second axial grating scale coordinate system position and a second visual coordinate system position of a second intersection; wherein the first intersection and the second intersection are respectively corresponding to connection points of the first journal (120) and the axle body (110) on both radial sides of the first journal (120); Determine the world coordinate system position of the first intersection point according to the first radial grating scale coordinate system position, the first axial grating scale coordinate system position and the first visual coordinate system position, and determine the world coordinate system position of the second intersection point according to the second radial grating scale coordinate system position, the second axial grating scale coordinate system position and the second visual coordinate system position; The visual device (6) moves to one radial side of the second journal (130) to obtain a third radial grating scale coordinate system position, a third axial grating scale coordinate system position and a third visual coordinate system position of a third intersection; the visual device (6) moves to the other radial side of the second journal (130) to obtain a fourth radial grating scale coordinate system position, a fourth axial grating scale coordinate system position and a fourth visual coordinate system position of a fourth intersection; wherein the third intersection and the fourth intersection are respectively corresponding to connection points of the second journal (130) and the axle body (110) on both radial sides of the second journal (130); Determine the world coordinate system position of the third intersection point according to the third radial grating scale coordinate system position, the third axial grating scale coordinate system position and the third visual coordinate system position, and determine the world coordinate system position of the fourth intersection point according to the fourth radial grating scale coordinate system position, the fourth axial grating scale coordinate system position and the fourth visual coordinate system position; Acquire a first line segment between the first visual coordinate system position and the second visual coordinate system position, and a second line segment between the third visual coordinate system position and the fourth visual coordinate system position; The length of the axle body (110) is obtained according to the length of a perpendicular line from the midpoint of the first line segment to the second line segment.

10. The method for measuring axle length according to claim 9, characterized in that: The visual device (6) extracts line types on both sides of the connection between the first journal (120) and the second journal (130) and the axle body (110), wherein the line types are arcs and / or straight lines.

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