A Measuring Device and Measuring Method for the Internal Cross-Sectional Dimensions of a Vehicle Body

Abstract

The present invention provides a device for measuring the internal cross-sectional dimensions of a vehicle body, including a mounting bracket, and further including a cross-section measuring mechanism for measuring the internal cross-sectional shape of the vehicle body and a lateral horizontal measuring mechanism for measuring whether the left and right vehicle body side walls are symmetrically installed. The cross-section measuring mechanism and the lateral horizontal measuring mechanism are fixed to the bracket through a mounting plate. The present invention further provides a method for measuring the internal cross-sectional dimensions of a vehicle body, which uses the above device to scan and measure the internal cross-section of the vehicle body. The device and method for measuring the internal cross-sectional dimensions of a vehicle body provided by the present invention propose a method for implementing measurement of key dimensional parameters based on a portable device for measuring the internal dimensions of a vehicle body, and provide a new solution to the problem of optimizing the measurement technology in this field.

Description

Technical Field

[0001] The present invention relates to the technical field of rail vehicles, and in particular to a device and method for measuring the internal cross-sectional dimensions of a car body. Background Art

[0002] At present, with the improvement of the urbanization level in China and the construction of urban agglomerations, the population in some large and medium-sized cities has increased rapidly. There is an urgent need for convenient urban rail public transportation. The extensive use of urban rail vehicles has put forward higher requirements for the manufacturing quality of urban rail trains. The overall internal dimensions of the urban rail vehicle car body and the assembly and positioning dimensions of the key internal installation components are important indicators for evaluating the excellent quality of urban rail vehicle products. Abroad, companies such as Spanesi in Italy and Caroliner in Sweden have developed automotive body electronic measurement systems, which have certain advantages in measurement accuracy and operability. Using laser and infrared scanning technologies, the three-dimensional external dimensions of the automotive body can be measured, meeting the new requirements of modern automotive repair industry detection technologies. There is very little measurement of the internal dimensions of rail transit vehicles. Domestically, the application of intelligent internal scanning measurement systems in the production of rail vehicle car bodies is relatively rare. Most traditional measurement methods are manual measurements, and the measurement results are affected by human factors more. Moreover, the measurement efficiency and accuracy are difficult to meet the requirements of the modern production cycle. In the current domestic and international markets, there are only laser measurement technologies for the external contour of trains and laser detection technologies for tunnels or pipelines similar to the detection of the internal contour of vehicles. No commercial device specifically for detecting the internal contour of train vehicles has been developed yet. Thus, it is extremely urgent to develop a device for detecting the key internal dimensions of trains required by the project. To solve the above problems, make the internal measurement process of urban rail vehicle car bodies more automated and accurate, and provide better data support for the assembly and positioning, quality evaluation, and internal maintenance of urban rail car bodies, a device and a scanning method for scanning the cross-sectional two-dimensional contour inside the car body are urgently needed. Summary of the Invention

[0003] The main purpose of the present invention is to solve the above problems and deficiencies, provide a device for measuring the internal cross-sectional dimensions of a car body, scan the cross-sectional two-dimensional contour inside the car body, and further provide a method for scanning using the measuring device.

[0004] To achieve the above object, the present invention first provides a device for measuring the internal cross-sectional dimensions of a car body, and its technical solution is:

[0005] A device for measuring the internal cross-sectional dimensions of a car body includes a mounting bracket, and further includes a cross-section measuring mechanism for measuring the cross-sectional shape of the inside of the car body and a transverse horizontal measuring mechanism for measuring whether the installation on the left and right car body side walls is symmetric. The cross-section measuring mechanism and the transverse horizontal measuring mechanism are fixed to the bracket through a mounting plate.

[0006] Further, the cross-section measuring mechanism includes a laser rangefinder, a rotating device that drives the laser rangefinder to rotate to achieve cross-section measurement, and a rotary encoder that records the rotation angle of the rotating device and the measured distance. The rotating device, the rotary encoder, and the lateral horizontal measuring mechanism are fixed to the mounting plate.

[0007] Further, it further includes a horizontal adjustment mechanism that can adjust the measuring directions of the lateral horizontal measuring mechanism and the cross-section measuring mechanism.

[0008] Further, the horizontal adjustment mechanism includes a first X-Y inclination sensor provided on the bracket, a second X-Y inclination sensor mounted on the mounting plate, and an X-Y pitching adjustment table fixed to the bracket and capable of adjusting the second X-Y inclination sensor to be parallel to the first X-Y inclination sensor.

[0009] Further, the horizontal adjustment mechanism further includes a rotating motor that adjusts the measuring direction of the lateral horizontal measuring mechanism to be perpendicular to the vehicle body, and the mounting plate is fixed to the output shaft of the rotating motor.

[0010] Further, the lateral horizontal measuring mechanism includes two horizontal laser rangefinders and a magnetic grating sensor that records the measured and moving distances of the horizontal laser rangefinders. The two horizontal laser rangefinders are arranged in opposite directions on the sliding seat of the sliding table, the magnetic grating sensor is arranged at the bottom of the sliding table, and the sliding table is fixed to the bracket.

[0011] Another invention of the present invention provides a method for measuring the internal cross-section size of a vehicle body, adopting the following technical solution:

[0012] A method for measuring the internal cross-section size of a vehicle body, adopting the following technical means:

[0013] a. Place the measuring device inside the vehicle body. The horizontal adjustment mechanism takes the data of the first X-Y inclination sensor on the bracket as a reference, and adjusts the first and second X-Y inclination sensors through the X-Y pitching adjustment table to make the measuring part of the entire device parallel to the bottom of the vehicle body;

[0014] b. Horizontally rotate the mounting plate and the lateral horizontal measuring mechanism and the cross-section measuring mechanism connected thereto, so that the measuring directions of the lateral horizontal measuring mechanism and the cross-section measuring mechanism are perpendicular to the inner wall side wall of the vehicle body;

[0015] c. Two horizontal laser rangefinders of the horizontal measurement mechanism on the same straight line move horizontally along the vehicle center line body driven by the sliding, and scan the side walls on both sides of the vehicle body respectively. The magnetic grating sensors start to measure the distance. When the laser of the horizontal laser rangefinder hits the edge of the side window, the magnetic grating sensors respectively record the vertical distances from the two horizontal laser rangefinders from the initial position to the adjacent side window, so as to judge whether there is a deviation between the two side windows relative to the vehicle body's transverse center plane;

[0016] d. The rotating device of the cross-section measurement mechanism drives the laser rangefinder and the rotary encoder to rotate. The laser rangefinder measures the distance from the measurement point to each object, and the rotary encoder rotates synchronously with the laser rangefinder to record the rotation angle. A measurement coordinate system is established by the measuring device, and the cross-section contour is constructed according to the length recorded by the laser rangefinder and the angle recorded by the rotary encoder, completing the in-situ real-time two-dimensional cross-section contour of the vehicle body interior.

[0017] Furthermore, for the rotating mounting plate and the horizontal measurement mechanism and cross-section measurement mechanism connected thereto, while rotating, the two laser rangefinders on the same straight line will measure the distance to the side wall of the vehicle body interior. When measuring multiple times and stopping at the position of the minimum length measured, at this time, the measuring direction of the entire measuring device is perpendicular to the side wall of the vehicle body interior.

[0018] Furthermore, when scanning the two-dimensional cross-section contour of the vehicle body, the vehicle body width is measured synchronously. Taking the laser rangefinder as point A, point B is selected from one side side wall, and the laser rangefinder turns from point B on the vehicle body side wall to point C on the other side side wall. The angle between point B and the horizontal plane is α, and the angle between point C and the horizontal plane is β. Controlled by the rotary encoder, make |AB|sinα = |AC|sin(180° - β), so as to obtain the width |CB| = |AB|cosα + |AC|cosβ at a certain point of the vehicle body through trigonometric functions.

[0019] Furthermore, when scanning the two-dimensional cross-section contour, the squareness of the vehicle body is detected synchronously. The maximum distance from the laser rangefinder to the top of the vehicle body side wall and the maximum distance to the bottom of the opposite side wall are collected by rotating the laser rangefinder, and the rotation angle is recorded. The diagonal length in this direction is obtained through the cosine theorem. Similarly, the diagonal length in the other direction is obtained, and it is judged whether the vehicle body is installed squarely by the two diagonal lengths and the rotation angle.

[0020] In summary, a measuring device and method for the cross-sectional dimensions of the vehicle body interior provided by the present invention have the following advantages compared with the prior art:

[0021] 1. A method for measuring key dimensional parameters based on a portable measuring device for the interior dimensions of a vehicle body is proposed, providing a new solution for optimizing the measurement technology problems in this field;

[0022] 2. A high-precision laser ranging sensor is adopted to achieve non-contact accurate measurement of the key dimensional parameters inside the vehicle body, avoiding systematic errors generated by traditional contact measurement methods;

[0023] 3. By constructing a multi-axis servo precision motion system and using inclination and displacement sensors for feedback control, the repeated positioning accuracy of the measurement reference and the precision and automation of the measurement process are achieved, reducing measurement errors caused by human factors;

[0024] 4. The inventive device has multiple measurement functions, can achieve accurate measurement of multiple key dimensions inside the vehicle body, and provides technical support for the accurate assembly of the vehicle body. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : Side view of a device for measuring the cross-sectional dimensions inside a vehicle body provided by the present invention;

[0026] Figure 2 : Three-dimensional view (without bracket) of a device for measuring the cross-sectional dimensions inside a vehicle body provided by the present invention;

[0027] Figure 3 : Side view (without bracket) of a device for measuring the cross-sectional dimensions inside a vehicle body provided by the present invention;

[0028] Figure 4 : Schematic diagram of measuring the vehicle body width in a method for measuring the cross-sectional dimensions inside a vehicle body provided by the present invention;

[0029] Figure 5 : Schematic diagram of measuring the vehicle body diagonal in a method for measuring the cross-sectional dimensions inside a vehicle body provided by the present invention;

[0030] Among them, there are bracket 1, leg 2, display 3, first X-Y inclination sensor 4, X-Y pitch adjustment table 5, rotary motor 6, rotary mounting seat 7, laser rangefinder 8, direct drive servo motor 9, second X-Y inclination sensor 10, electrical slip ring 11, encoder mounting seat 12, rotary encoder 13, precision servo slide 14, horizontal laser rangefinder 15, slider 16, magnetic scale mounting plate 17, magnetic scale sensor 18, mounting plate 19, mounting right side plate 19a, mounting plate upper plate 19b, mounting plate bottom plate 19c. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0032] The present invention provides a device for measuring the internal cross-sectional dimensions of a vehicle body, including a mounting bracket 1, and further including a cross-section measuring mechanism for measuring the internal cross-sectional shape of the vehicle body and a lateral horizontal measuring mechanism for measuring whether the left and right vehicle body side walls are symmetrically installed. The cross-section measuring mechanism and the lateral horizontal measuring mechanism are fixed to the bracket 1 through a mounting plate 19.

[0033] As Figures 1 to 3 shown, in an embodiment of the device for measuring the internal cross-sectional dimensions of a vehicle body provided by the present invention, the cross-section measuring mechanism and the lateral horizontal measuring mechanism are both directly or indirectly fixed to the bracket 1. The bracket 1 can be a frame structure, with four or more legs 2 provided at the bottom to adjust the height of the entire device, or it can be a movable loading vehicle with wheels at the bottom for easy movement. A mounting plate 19 is fixedly installed at the top of the bracket 1, and the cross-section measuring mechanism and the lateral horizontal measuring mechanism are respectively fixed to the mounting plate 19. To prevent the components of the lateral horizontal measuring mechanism from affecting the measurement of the cross-section measuring mechanism, in this embodiment, the mounting plate 19 includes a mounting right side plate 19a and a mounting plate bottom plate 19c that are fixedly installed perpendicular to each other. The mounting bottom plate 19c is fixed to the bracket 1, the lateral horizontal measuring mechanism is fixed to the mounting bottom plate 19c, and the cross-section measuring mechanism is fixed to the middle upper part of the mounting right side plate 19a, with the measurement position higher than the top of the lateral horizontal measuring mechanism to avoid measurement interference.

[0034] In this embodiment, the lateral horizontal measuring mechanism includes two horizontal laser rangefinders 15, which are fixedly installed at the top surface of a slider 16 of a precision servo slide 14 at the bottom. The laser beams emitted by the two horizontal laser rangefinders 15 are on the same straight line, and the laser emission directions are opposite, respectively facing the side walls on both sides of the vehicle body, and the emitted lasers are perpendicular to the corresponding side walls. The precision servo slide 14 is fixed to the mounting bottom plate 19c. A magnetic grating sensor 18 is fixedly installed on the bottom surface of the slider 16 through a magnetic grating mount 17, and the moving distances of the two horizontal laser rangefinders 15 are respectively measured and recorded through the magnetic grating sensor 18.

[0035] The mounting right side plate 19a is vertically fixed to the right side of the mounting bottom plate 19c. The cross-section measuring mechanism is fixed to the right side of the mounting right side plate 19a (the side facing away from the lateral horizontal measuring mechanism), and includes a laser rangefinder 8, a rotating device that can drive the laser rangefinder 8 to rotate for cross-section measurement, and a rotary encoder 13 for measuring distance and rotation angle, as Figure 2 and Figure 3As shown, in this embodiment, the rotating device includes a rotating mounting base 7 fixed to the output shaft of the direct-drive rotary servo motor 9. The laser rangefinder 8 is fixed to the rotating mounting base 7. The direct-drive rotary servo motor 9 is fixed to the right side of the right mounting side plate 19a. The other end of the rotating mounting base 7 passes through the right mounting side plate 19a and is sleeved with the slip ring 11. On the left side surface of the right mounting side plate 19a above the rotating mounting base 7, an upper mounting plate 19b is fixed. One end of the rotary encoder 13 is fixed to the encoder mounting base 12 below the upper mounting plate 19b, and the other end is inserted into the shaft of the rotating mounting base 7 for detecting the rotation angle of the laser rangefinder 8.

[0036] To obtain the true measurement data and reduce the measurement error, it is necessary to adjust the laser emitted by the horizontal measurement mechanism to be perpendicular to the side wall, and at the same time, the laser line is parallel to the floor. At the same time, when the laser beam of the cross-section measurement mechanism is in a horizontal state, it is also perpendicular to the side wall. Therefore, in this embodiment, a horizontal adjustment mechanism is further included to adjust the direction of the laser beam emitted by the horizontal measurement mechanism, such as Figure 2 and Figure 3 As shown, in this embodiment, the horizontal adjustment mechanism includes a first X-Y inclination sensor 4 provided on the bracket 1 and a second X-Y inclination sensor 10 provided on the upper mounting plate 19b. An X-Y pitch adjustment table 5 is also provided between the bottom mounting plate 19c and the top surface of the bracket 1. The installation direction of the second X-Y inclination sensor 10 is the same as the installation direction (laser emission direction) of the horizontal laser rangefinder 15. The upper and lower parts of the X-Y pitch adjustment table 5 are connected by sliders. The lower part is fixed to the top surface of the bracket 1, and the upper part is rotatably fixed to the bottom of the rotary motor 6. The output shaft (rotating platform) of the rotary motor 6 is fixed to the bottom surface of the mounting plate 19 and can drive the mounting plate 19 to rotate. A display 3 is also provided on the bracket 1. The display 3 includes a touch screen for displaying various data and has a built-in controller for receiving real-time data from the inclination sensors, further controlling the actions of each motor, and controlling the X-Y pitch adjustment table to adjust the inclinations of the first / second X-Y inclination sensors 4 / 10 to be the same, so that the laser emission direction of the horizontal laser rangefinder 8 is parallel to the floor.

[0037] The present invention further provides a method for measuring the two longitudinal profiles of the interior cross-section of a vehicle body using the above measurement device, including the following steps:

[0038] a. Place the measuring device inside the vehicle body. The first X-Y inclination sensor 4 under the bottom bracket 1 will feedback the collected results to the display 3 and display them on the display screen. Then, based on this data, the staff will adjust the X-Y pitching adjustment table (5) according to the results collected by the second X-Y inclination sensor 10 on the upper side of the upper plate 19b of the laser rangefinder mounting plate, so that the inclination angles of the second X-Y inclination sensor 10 and the first X-Y inclination sensor 4 are the same. In this way, the measuring direction of the entire measuring device (lateral horizontal measuring mechanism and cross-section measuring mechanism) located on the mounting plate 19 is parallel to the vehicle body bottom;

[0039] b. The controller built in the display 3 drives the rotary motor 6, so that the rotary platform at the end of the rotary motor 6 drives the mounting plate (19) and the measuring device connected thereto to rotate within a 90-degree angle range; and controls the horizontal laser rangefinder 15 to emit laser for distance measurement. While rotating, the two horizontal laser rangefinders 15 on the same straight line will respectively measure the distances L1 and L2 to the inner side wall of the vehicle body on the corresponding side. At this time, the magnetic grating sensor 18 will respectively record the rotation angles of the two horizontal laser rangefinders 15 and L1 and L2, and control the rotary motor 6 to stop at the position where the minimum lengths of L1 and L2 are measured; at this time, the measuring angle (laser beam direction) of the lateral horizontal measuring mechanism is perpendicular to the inner side wall of the vehicle body;

[0040] c. After adjusting the measuring angle of the measuring device, the controller controls the slider 16 of the precision servo slide 14 to move from the rightmost end to the left on the precision servo slide 14. The two horizontal laser rangefinders 15 on the slider 16 will then perform scanning feed accordingly. The laser beams of the horizontal laser rangefinders 15 move along the vehicle body length direction from the upper edge of the vehicle body side wall, and the magnetic grating sensor 18 installed below the slider 16 also starts to measure the distance; when the laser of the horizontal laser rangefinder 15 hits the edge of the side window, the magnetic grating sensor (18) will record the distance at this time. In this way, the vertical distances L3 and L4 from the starting position to the corresponding side side windows are respectively measured. When L3 = L4, the distances from the measuring starting position to the two side windows are equal, and whether the two side walls are symmetrically installed along the vehicle body length direction without deviation. When L3 ≠ L4, the deviation of the two side walls relative to the vehicle body transverse center plane = │L3 - L4│. If necessary, the installation positions of the two side walls can be adjusted accordingly according to the deviation situation;

[0041] d. The controller controls the direct-drive servo motor 9 on the right side of the mounting plate right side plate 19a, causing it to drive the rotary mounting base 7 and the laser rangefinder 8 and rotary encoder 13 connected thereto to rotate 360 degrees within the cross-section perpendicular to the floor; the laser rangefinder 8 measures the distance to each object within this cross-section, and the rotary encoder 13 rotates synchronously with the laser rangefinder 8 to record the rotation angle; a measurement coordinate system is established with the laser rangefinder 8 as the center, and the cross-section contour is constructed based on the length recorded by the laser rangefinder 8 and the angle recorded by the rotary encoder 13, completing the in-situ real-time two-dimensional cross-section contour scanning measurement of the vehicle body interior.

[0042] When performing the two-dimensional cross-section contour scanning measurement, the vehicle body width measurement can be carried out simultaneously. The method for measuring the vehicle body width by rotating the laser rangefinder sensor is as follows:

[0043] As Figure 4 shown, the laser rangefinder sensor 8 is the center point A. The laser beam rotates from point B on one side wall of the vehicle body to point C on the opposite side wall. The selection of point C needs to satisfy |AB|sinα = |AC|sin(180° - β), so as to ensure that points B and C are at the same height during measurement, making the line segment |CB| parallel to the floor. Then, according to trigonometric functions, |CB| = |AB|cosα + |AC|cosβ. Corresponding points B and C can be selected at different positions on the two side walls of the vehicle body, so as to obtain the width of the vehicle body at different heights.

[0044] Furthermore, when performing the two-dimensional cross-section contour scanning measurement, the symmetry detection of the vehicle body mounting cross-section can also be carried out. The positions of the two points with the maximum distance from the sensor to the vehicle body are collected by rotating the laser rangefinder 8. As Figure 5 shown, select point E at the top of one side of the vehicle body side wall, which is the farthest from point A where the laser rangefinder 8 is located, and then select point F at the bottom of the opposite side, which is the farthest from point A where the laser rangefinder 8 is located. The laser rangefinder 8 collects the maximum distance points |AE| and |AF|, and the encoder records the included angle γ from point E to point F. Then, the length L of the vehicle body diagonal is calculated using the cosine theorem, L = |EF|. Let a = |AE| and b = |AF|, then:

[0045] |EF| = √(a² + b² - 2ab*cosγ).

[0046] Using the same method, the length L' of the diagonal in the other direction is measured. According to the calculated L and L', it is judged whether the rectangular cross-section of the vehicle body mounting is symmetric.

[0047] In summary, a vehicle body interior cross-section size measurement device and method provided by the present invention have the following advantages compared with the prior art:

[0048] 1. A method for measuring key dimensional parameters based on a portable in-vehicle interior dimension measuring device is proposed, providing a new solution to the problem of optimizing measurement techniques in this field;

[0049] 2. By using a high-precision laser ranging sensor, non-contact and accurate measurement of key in-vehicle interior dimensional parameters is achieved, avoiding systematic errors caused by traditional contact measurement methods;

[0050] 3. By constructing a multi-axis servo precision motion system and using inclination and displacement sensors for feedback control, the repeated positioning accuracy of the measurement reference and the precision and automation of the measurement process are achieved, reducing measurement errors caused by human factors;

[0051] 4. The inventive device has multiple measurement functions, can achieve accurate measurement of multiple key in-vehicle interior dimensions, and provides technical support for the accurate assembly of the vehicle body.

[0052] As described above, similar technical solutions can be derived in combination with the given solution content. Any simple modifications, equivalent changes and decorations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A measuring device for the internal cross-sectional dimensions of a vehicle body, comprising a mounting bracket, characterized in that: it further comprises a cross-section measuring mechanism for measuring the internal cross-sectional shape of the vehicle body and a lateral horizontal measuring mechanism for measuring whether the installations on the left and right vehicle side walls are symmetric. The cross-section measuring mechanism and the lateral horizontal measuring mechanism are fixed to the bracket through a mounting plate; the cross-section measuring mechanism comprises a laser rangefinder, a rotating device for driving the laser rangefinder to rotate to achieve cross-section measurement, and a rotary encoder for recording the rotation angle of the rotating device and the measured distance. The rotating device, the rotary encoder and the lateral horizontal measuring mechanism are fixed to the mounting plate; it further comprises a horizontal adjustment mechanism for adjusting the measuring directions of the lateral horizontal measuring mechanism and the cross-section measuring mechanism; the horizontal adjustment mechanism comprises a first X-Y inclination sensor arranged on the bracket, a second X-Y inclination sensor mounted on the mounting plate, and an X-Y pitch adjustment table fixed to the bracket and capable of adjusting the second X-Y inclination sensor to be parallel to the first X-Y inclination sensor; the horizontal adjustment mechanism further comprises a rotating motor for adjusting the measuring direction of the lateral horizontal measuring mechanism to be perpendicular to the vehicle body. The mounting plate is fixed to the output shaft of the rotating motor; the lateral horizontal measuring mechanism comprises two horizontal laser rangefinders and a magnetic grating sensor for recording the measured and moving distances of the horizontal laser rangefinders. The two horizontal laser rangefinders are arranged in opposite directions on the slider of a slide table. The magnetic grating sensor is arranged at the bottom of the slide table. The slide table is fixed to the bracket.

2. A method for measuring the internal cross-sectional dimensions of a vehicle body, using the measuring device for the internal cross-sectional dimensions of a vehicle body as described in claim 1, characterized in that: a. The measuring device is placed inside the vehicle body. The horizontal adjustment mechanism takes the data of the first X-Y inclination sensor on the bracket as a reference, and through the adjustment of the X-Y pitch adjustment table, makes the inclination angles of the first X-Y inclination sensor and the second X-Y inclination sensor the same, so that the measuring part of the whole device is parallel to the bottom of the vehicle body; b. Horizontally rotate the mounting plate and the lateral horizontal measuring mechanism and the cross-section measuring mechanism connected thereto, so that the measuring directions of the lateral horizontal measuring mechanism and the cross-section measuring mechanism are perpendicular to the inner wall side wall of the vehicle body; c. The two horizontal laser rangefinders of the lateral horizontal measuring mechanism on the same straight line horizontally move along the vehicle body center line driven by the slider and respectively scan the side walls on both sides of the vehicle body. The magnetic grating sensor starts to measure the distance. When the laser of the horizontal laser rangefinder hits the edge of the side window, the magnetic grating sensor respectively records the vertical distances of the two horizontal laser rangefinders from the initial position to the adjacent side window, so as to judge whether there is a deviation of the side windows on both sides relative to the vehicle body transverse center plane; d. The rotating device of the cross-section measuring mechanism drives the laser rangefinder and the rotary encoder to rotate. The laser rangefinder measures the distance from the measuring point to each object. The rotary encoder rotates synchronously with the laser rangefinder and records the rotation angle. A measuring coordinate system is established with the measuring device, and a cross-section contour is constructed according to the length recorded by the laser rangefinder and the angle recorded by the rotary encoder.

3. The measurement method of the internal cross-sectional dimension of a vehicle body as described in claim 2, characterized in that: The rotating mounting plate and the horizontally transverse measurement mechanism and cross-section measurement mechanism connected thereto are rotated. While rotating, two laser rangefinders on the same straight line will measure the distance to the side wall of the vehicle body inner wall. Multiple rotational measurements are performed and stopped at the position of the measured minimum length. At this time, the measurement direction of the entire measuring device is perpendicular to the side wall of the vehicle body inner wall.

4. The measurement method of the internal cross-sectional dimension of a vehicle body as described in claim 2, characterized in that: When scanning the two-dimensional cross-sectional contour of the vehicle body, the width of the vehicle body is measured synchronously. Taking the laser rangefinder as point A, point B is selected from one side wall. The laser rangefinder turns from point B on the vehicle body side wall to point C on the other side wall. The angle between point B and the horizontal plane is α, and the angle between point C and the horizontal plane is β. Controlled by a rotary encoder, make |AB|sinα = |AC|sin(180° - β), so that through trigonometric functions, the width |CB| at a certain point of the vehicle body is obtained as |CB| = |AB|cosα + |AC|cosβ.

5. The measurement method of the internal cross-sectional dimension of a vehicle body as described in claim 2, characterized in that: When scanning the two-dimensional cross-sectional contour, the squareness of the vehicle body is detected synchronously. The maximum distance from the laser rangefinder to the top of the vehicle body side wall and the maximum distance from the bottom of the opposite side wall to the laser rangefinder are collected by rotating the laser rangefinder, and the rotation angle is recorded. The diagonal length in this direction is obtained by the cosine theorem. Similarly, the diagonal length in the other direction is obtained, and whether the vehicle body is installed squarely is judged by the lengths of the two diagonals.

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