阅读说明：本技术 一种轨道车辆车体底架曲面面型检测系统及其检测方法 (Detection system and detection method for curved surface shape of underframe of railway vehicle body ) 是由 陈祺 梁雯雯 陈飞 张国旺 杨盛 张煜超 于 2021-08-10 设计创作，主要内容包括：本发明公开一种轨道车辆车体底架曲面面型检测系统及方法,系统包括：控制器、用于支撑待测车体底架的支撑机构以及设置于支撑机构上方的测量架；测量架上安装有至少一个测量单元；各测量单元包括光栅投影仪和分别设置于光栅投影仪两侧的图像采集器,两个图像采集器的视场总范围至少覆盖光栅投影仪在待测车体底架上的投影范围；控制器控制光栅投影仪向待测车体底架表面投射多组位相不同的光栅条纹图像,图像采集器采集待测车体底架平面上的光栅图像,控制器根据采集的光栅图像数据以及向投影仪发出的移相控制参数,计算待测车体底架表面的曲面面型。本发明利用光栅投影位相解调成像法实现对车辆车体底架表面面型数据的获取,准确且自动化程度较高。(The invention discloses a detection system and a detection method for a curved surface type of a chassis of a railway vehicle body, wherein the system comprises the following steps: the device comprises a controller, a supporting mechanism for supporting the underframe of the vehicle body to be measured and a measuring frame arranged above the supporting mechanism; at least one measuring unit is arranged on the measuring frame; each measuring unit comprises a grating projector and image collectors respectively arranged at two sides of the grating projector, and the total range of the view fields of the two image collectors at least covers the projection range of the grating projector on the underframe of the vehicle body to be measured; the controller controls the grating projector to project a plurality of groups of grating stripe images with different phases to the surface of the underframe of the vehicle body to be measured, the image collector collects the grating images on the plane of the underframe of the vehicle body to be measured, and the controller calculates the curved surface type of the surface of the underframe of the vehicle body to be measured according to the collected grating image data and phase-shifting control parameters sent to the projector. The invention realizes the acquisition of the surface type data of the vehicle body underframe by using a grating projection phase demodulation imaging method, and has accuracy and higher automation degree.)

1. The utility model provides a rail vehicle automobile body chassis curved surface face type detecting system which characterized in that includes: the controller is used for supporting a supporting mechanism of the underframe of the car body to be measured and a measuring frame arranged above the supporting mechanism;

at least one measuring unit is arranged on the measuring frame; each measuring unit comprises a grating projector and image collectors respectively arranged at two sides of the grating projector, and the total range of the view fields of the two image collectors at least covers the projection range of the grating projector on the underframe of the vehicle body to be measured; the data output end of the image collector and the control end of the grating projector are respectively connected with the controller, and the control end of the grating projector comprises a phase-shifting control end;

the controller controls the grating projector to project a plurality of groups of grating stripe images with different phases to the surface of the underframe of the vehicle body to be measured, the image collector collects the grating images on the plane of the underframe of the vehicle body to be measured and transmits the grating images to the controller, and the controller calculates the curved surface type of the surface of the underframe of the vehicle body to be measured according to the received grating image data and the phase-shifting control parameters sent to the projector.

2. The rail vehicle body underframe curved surface profile detection system according to claim 1, further comprising a plurality of calibration light sources arranged at two sides of a measurement station of the body underframe to be detected, wherein the field of view area of each image collector at least covers 2 calibration light sources;

all the calibration light sources are located on the same reference plane, and the reference plane and the base frame reference plane of the railway vehicle body are located in the same plane.

3. The rail vehicle car body underframe curved surface profile detection system of claim 1, wherein the measuring rack comprises a horizontally arranged slide rail, and the measuring unit is slidably connected and mounted on the slide rail;

the supporting mechanism is at least 4 supports, and the 4 supports are arranged on four corner points of the same rectangle.

4. The rail vehicle car body underframe curved surface profile detection system as claimed in claim 2, wherein at least two measurement units are mounted on the measurement frame at the same height, the projection range edges of adjacent measurement units overlap each other, and the field range edges overlap each other.

5. The rail vehicle body chassis curved surface type detection system as claimed in claim 4, wherein the calibration light sources are LED lamp beads, the number of the single-side calibration light sources is 5, the calibration light sources on two sides are respectively arranged in a one-to-one opposite manner, and the distances between adjacent calibration light sources in the single-side calibration light sources are equal;

in each measuring unit, the overlapping area of the field ranges of the two image collectors covers a pair of calibration light sources; the overlapping area of the field of view ranges of the image collectors of the adjacent measuring units covers a pair of calibration light sources; the outer edge of the total view field range of each measuring unit image collector covers a pair of calibration light sources.

6. The rail vehicle car body underframe curved surface profile detection system as claimed in claim 1, wherein the measurement unit is installed at a height position of 1.8m above the surface of the car body underframe to be detected, the field of view of a single image collector covers the range of 6.2m by 4.9m of the surface of the car body underframe to be detected, and the field of view of adjacent image collectors has an overlapping region.

7. The curved surface type detection system for the underframe of the railway vehicle body as claimed in claim 1, wherein the image collector adopts a 2592 x 2048 pixel gigabit industrial CMOS camera, the pixel size is 4.8 μm x 4.8 μm, and a 12mm focal length industrial lens is matched; the raster projector uses a 4096 x 2160 pixel high definition projector, the projection range is 50-300 inches in diameter, and the model can be 3LCD/0.74 inch chip/2500 lumens.

8. The detection method of the curved surface type detection system of the underframe of the railway vehicle body according to any one of claims 1 to 7 is characterized by comprising the following steps:

the controller controls the grating projector to project sinusoidal grating stripes with set frequency to the surface of the underframe of the vehicle body to be measured;

the controller obtains stripe images of the surface of the underframe of the vehicle body to be measured in a corresponding single projection area through 2 calibrated image collectors in each measurement unit;

the controller controls the grating projector to project sinusoidal grating stripes on the surface of the underframe of the vehicle body to be detected to shift the phase for multiple times, and an image collector is used for acquiring a stripe image of the surface of the underframe of the vehicle body to be detected after phase shifting each time;

the controller calculates and obtains image stripe phase changes at different positions on the surface of the underframe of the vehicle body to be measured by utilizing a preset grating stripe phase-shifting demodulation algorithm according to the obtained image data and the phase corresponding to the image;

and the controller determines the surface type distribution data of the surface curved surface of the underframe of the vehicle body to be detected according to the phase change of the image stripes.

9. The method for detecting the curved surface profile of the underframe of a railway vehicle body as claimed in claim 8, wherein the controller controls the grating projector to project sinusoidal grating stripes on the surface of the underframe of the car body to be detected to shift 4 times at intervals of pi/4 of phase.

10. The method for detecting the curved surface type of the underframe of the railway vehicle body as claimed in claim 9, wherein the preset grating fringe phase-shift demodulation algorithm adopts a four-step phase-shift algorithm, comprising: assuming that the sinusoidal grating stripes respectively shift the phase by 0, pi/2, pi and 3 pi/2, the acquired stripe images respectively correspond to I₀(x,y)、I_π/2(x,y)、I_π(x, y) and I_3π/2(x, y), then the four sinusoidal raster images are represented as:

wherein A represents the background light intensity, B represents the modulation amplitude of the fringes, and I (x, y) represents the light intensity of a point with coordinates (x, y), and the corresponding phase position of any point (x, y)Comprises the following steps:

for each point on the curved surface of the chassis, the phase position to be obtainedAnd comparing the phase variation with a preset initial phase to obtain the phase variation of each point on the underframe of the vehicle body to be detected.

Technical Field

The invention relates to the technical field of rail vehicle manufacturing and detection, in particular to a rail vehicle body chassis curved surface type detection system and a detection method thereof.

Background

In the production of the body of a railway vehicle, a certain upward deflection deformation is always reserved during the production of the underframe and after the completion of the body of the railway vehicle, and a prestress is formed to resist the gravity deformation when the vehicle is fully loaded. The deflection of the vehicle and the underframe is an important evaluation criterion for the quality of the vehicle body product, and various vehicle interior parts need to be installed above the floor after the welding of the vehicle body is completed. Therefore, the measurement of the curved surface of the underframe of the vehicle body is the basis and the precondition of the mounting quality of the vehicle.

In the prior art, the curved surface profile of the underframe of the vehicle body is measured, and the limitations in the aspects of measurement efficiency, measurement range and measurement accuracy exist.

Disclosure of Invention

The invention aims to provide a detection system and a detection method for the curved surface profile of a vehicle body underframe of a railway vehicle, which are used for acquiring the surface profile data of the vehicle body underframe by utilizing a grating projection phase demodulation imaging method and have the characteristics of simplicity, practicability and high automation degree.

The technical scheme adopted by the invention is as follows: a rail vehicle automobile body chassis curved surface type detecting system includes: the controller is used for supporting a supporting mechanism of the underframe of the car body to be measured and a measuring frame arranged above the supporting mechanism;

at least one measuring unit is arranged on the measuring frame; each measuring unit comprises a grating projector and image collectors respectively arranged at two sides of the grating projector, and the total range of the view fields of the two image collectors at least covers the projection range of the grating projector on the underframe of the vehicle body to be measured; the data output end of the image collector and the control end of the grating projector are respectively connected with the controller, and the control end of the grating projector comprises a phase-shifting control end;

the controller controls the grating projector to project a plurality of groups of grating stripe images with different phases to the surface of the underframe of the vehicle body to be measured, the image collector collects the grating images on the plane of the underframe of the vehicle body to be measured and transmits the grating images to the controller, and the controller calculates the curved surface type of the surface of the underframe of the vehicle body to be measured according to the received grating image data and the phase-shifting control parameters sent to the projector.

Optionally, the system further includes calibration light sources disposed at two sides of the measurement station of the underframe of the vehicle body to be measured, the number of the calibration light sources at each side is multiple, and the field area of each image collector at least covers 2 calibration light sources;

all the calibration light sources are located on the same reference plane, and the reference plane and the base frame reference plane of the railway vehicle body are located in the same plane.

The position of the calibration light source is known, the calibration light source at the known position is collected by the image collector, and the related parameters of the position of the measured point calculated by the data collected by the camera can be calculated, so that the position (mainly highlighting the elevation of the standard plane) of each point on the image can be calculated according to the image collection result in actual detection.

Optionally, the measuring rack includes a slide rail horizontally arranged, and the measuring unit is slidably connected and mounted on the slide rail;

the supporting mechanism is at least 4 supports, and the 4 supports are arranged on four corner points of the same rectangle. The arrangement of the slide rail can enable the system to realize the measurement of the surface of the chassis of the longer vehicle body only by the sliding of one measuring unit on the slide rail, and the system cost is reduced. The supporting mechanism can ensure that the chassis of the vehicle body to be measured cannot shake in the measuring process, and the accuracy of the measuring result is ensured.

Optionally, at least two measuring units located at the same height are installed on the measuring rack, the edges of the projection ranges of the adjacent measuring units are overlapped, and the edges of the field of view ranges are overlapped. The method can ensure that the whole curved surface to be detected can be detected, and is beneficial to calibrating the camera parameters by utilizing the calibration light source positioned in the overlapping area.

Optionally, the calibration light sources are LED lamp beads, the number of the single-side calibration light sources is 5, the calibration light sources on two sides are respectively arranged in a one-to-one correspondence, and the distances between adjacent calibration light sources in the single-side multiple calibration light sources are equal;

in each measuring unit, the overlapping area of the field ranges of the two image collectors covers a pair of calibration light sources; the overlapping area of the field of view ranges of the image collectors of the adjacent measuring units covers a pair of calibration light sources; the outer edge of the total view field range of each measuring unit image collector covers a pair of calibration light sources.

The multiple groups of calibration light sources can be used for calibrating the image collector before measurement more accurately, so that basic parameters are provided for image splicing and surface type calculation during real time of the controller.

Preferably, the two measuring units are arranged at the height position of 1.8m above the surface of the underframe of the vehicle body to be measured, the field range of a single image collector covers the range to be measured of 6.2m 4.9m above the surface of the underframe of the vehicle body to be measured, and the field ranges of adjacent image collectors are provided with overlapping areas. The measuring range of the whole vehicle body with the length of at least 23m and the width of 4.9m can be ensured.

Preferably, the image collector adopts a gigabit network industrial CMOS camera: 2592 × 2048 pixels, pixel size: 4.8 microns multiplied by 4.8 microns and is matched with a 12mm focal length industrial lens; the raster projector uses a 4096 x 2160 pixel high definition projector, the projection range is 50-300 inches in diameter, and the model can be 3LCD/0.74 inch chip/2500 lumens.

When the invention is applied, the CMOS camera can be adjusted or the focal length of the lens can be changed according to the measurement precision and the erection allowable height, and 2 groups, 3 groups or more than two groups of measurement units can be adopted simultaneously to meet the measurement of the sizes of the vehicle bodies of various vehicle types.

In a second aspect, the invention provides a detection method of the detection system for the curved surface shape of the underframe of the railway vehicle body, which comprises the following steps:

the controller controls the grating projector to project sinusoidal grating stripes with set frequency to the surface of the underframe of the vehicle body to be measured;

the controller obtains stripe images of the surface of the underframe of the vehicle body to be measured in a corresponding single projection area through 2 calibrated image collectors in each measurement unit;

the controller controls the grating projector to project sinusoidal grating stripes on the surface of the underframe of the vehicle body to be detected to shift the phase for multiple times, and an image collector is used for acquiring a stripe image of the surface of the underframe of the vehicle body to be detected after phase shifting each time;

the controller calculates and obtains image stripe phase changes at different positions on the surface of the underframe of the vehicle body to be measured by utilizing a preset grating stripe phase-shifting demodulation algorithm according to the obtained image data and the phase corresponding to the image;

and the controller determines the surface type distribution data of the surface curved surface of the underframe of the vehicle body to be detected according to the phase change of the image stripes.

Optionally, the controller controls the sinusoidal grating stripes projected to the surface of the underframe of the vehicle body to be measured by the grating projector to shift the phase for 4 times according to the phase interval pi/4. The phase-shift fringe data of a plurality of periods are collected for operation, and the phase demodulation precision of measurement can be improved.

Optionally, the preset grating fringe phase-shift demodulation algorithm adopts a four-step phase-shift algorithm, including: assuming that the sinusoidal grating stripes respectively shift the phase by 0, pi/2, pi and 3 pi/2, the acquired stripe images respectively correspond to I₀(x,y)、I_π/2(x,y)、I_π(x, y) and I_3π/2(x, y), then the four sinusoidal raster images are represented as:

wherein A represents the background light intensity, B represents the modulation amplitude of the fringes, and I (x, y) represents the coordinate (x, y)The light intensity of a point is the corresponding phase of any point (x, y)Comprises the following steps:

for each point on the curved surface of the chassis, the phase position to be obtainedAnd comparing the phase variation with a preset initial phase to obtain the phase variation of each point on the underframe of the vehicle body to be detected.

Advantageous effects

The automatic detection method for the curved surface profile based on the grating projection phase demodulation imaging method is an important detection method required by detection compensation for the curved surface profile on the surface of the underframe of the railway vehicle body, has the characteristics of large measurement range, high measurement speed and the like, gives the profile data of the whole underframe of the vehicle body at one time, can be used as a vehicle body production quality detection means, and can also provide accurate basic data for subsequent built-in installation according to the subsequent assembly requirements, guide an operator to install and improve the detection quality and the working efficiency.

After the detection device is calibrated, the surface profile of the underframe of the railway vehicle body can be automatically measured, three-dimensional data of the surface profile of the underframe of the vehicle body can be obtained, the measurement can be carried out when the underframe of the measurement vehicle body is hoisted in place, the detection process time is short, the data is accurate, and the operation is simple, convenient and quick.

Drawings

FIG. 1 is a schematic diagram of an embodiment of a detection system according to the present invention;

FIG. 2 is a schematic diagram of an embodiment of a detection system according to the present invention;

in the figure: 1. a measuring unit; 101. a grating projector; 102. image collector-CMOS camera; 2. a support; 3. controller-industrial control computer; 4. a support; 5. a measuring frame; 6. calibrating a light source-LED lamp bead; 7. a power source; 8. a guide rail; 9. and (5) a vehicle body underframe to be tested.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

Example 1

This embodiment introduces a rail vehicle automobile body chassis curved surface type detecting system, includes: the controller is used for supporting a supporting mechanism of the underframe of the car body to be measured and a measuring frame arranged above the supporting mechanism;

at least one measuring unit is arranged on the measuring frame; each measuring unit comprises a grating projector and image collectors respectively arranged at two sides of the grating projector, and the total range of the view fields of the two image collectors at least covers the projection range of the grating projector on the underframe of the vehicle body to be measured; the data output end of the image collector and the control end of the grating projector are respectively connected with the controller, and the control end of the grating projector comprises a phase-shifting control end;

the controller controls the grating projector to project a plurality of groups of grating stripe images with different phases to the surface of the underframe of the vehicle body to be measured, the image collector collects the grating images on the plane of the underframe of the vehicle body to be measured and transmits the grating images to the controller, and the controller calculates the curved surface type of the surface of the underframe of the vehicle body to be measured according to the received grating image data and the phase-shifting control parameters sent to the projector.

As shown in figure 1, in the detection system, a controller adopts an industrial control computer 3, a measuring unit 1 is arranged on a measuring frame 5, the measuring frame is arranged on a support 2 and is positioned above a bottom frame 9 of a railway vehicle body to be detected, and a supporting mechanism comprises 4 supporting seats 4 which are arranged on 4 corner points of the same rectangle.

In the embodiment, two groups of fixed-position measurement units are arranged by considering the length of a vehicle body to be measured, and in each measurement unit, the grating projector 101 and the image collector-CMOS camera 102 can respectively adopt the existing products; the grating projector and the CMOS camera are both electrically connected with the industrial control computer 3, and the projector, the CMOS camera and the industrial control computer are powered by a power supply 7.

The detection system further comprises calibration light sources, in the embodiment, the calibration light sources adopt LED lamp beads 6, as shown in FIG. 1, in order to adapt to the length of the underframe of the railway vehicle body, 10 LED lamp beads are arranged, 5 LED lamp beads are arranged on each side of the underframe, the calibration light sources on two sides are respectively arranged in a one-to-one opposite mode, and the distances between the adjacent calibration light sources in the multiple calibration light sources on one side are equal; all the calibration light sources are positioned on the same reference plane, and the reference plane and the base frame reference plane of the railway vehicle body are positioned in the same plane.

The position of the calibration light source is known, the calibration light source at the known position is collected by the image collector, and the related parameters of the position of the measured point calculated by the data collected by the camera can be calculated, so that the position of each point on the image can be calculated according to the image collection result during actual detection.

In order to improve the reliability of the camera calibration result, in this embodiment, the edges of the projection ranges of the adjacent measurement units are overlapped with each other, and the edges of the field of view ranges are overlapped with each other; in each measuring unit, the overlapping area of the field ranges of the two image collectors covers a pair of calibration light sources; the overlapping area of the field of view ranges of the image collectors of the adjacent measuring units covers a pair of calibration light sources; the outer edge of the total view field range of each measuring unit image collector covers a pair of calibration light sources. Therefore, the view field area of each image collector can cover at least 2 calibration light sources, and the whole curved surface to be detected can be ensured to be detected.

According to the measurement precision and the erection allowable height, the solution of the CMOS camera is adjusted, or the focal length of a lens is replaced, and 2 groups, 3 groups or a plurality of groups of measurement units are combined to meet the measurement of the sizes of the vehicle bodies of various vehicle types.

The measuring unit and the measuring frame of the embodiment can be arranged on a support 2, and the support and the measuring unit can be moved to the upper part of the underframe to be measured after the underframe of the car body to be measured is welded and hoisted on a support of a measuring station. The two measuring units are arranged at the height position 1.8m above the surface of the underframe of the vehicle body to be measured, the field range of a single image collector covers the range to be measured of 6.2m 4.9m above the surface of the underframe of the vehicle body to be measured, and the field ranges of adjacent image collectors are provided with overlapping areas. The measuring range of the whole vehicle body with the length of at least 23m and the width of 4.9m can be ensured.

After the positions of the measuring units are determined, the high-definition projector is controlled by the industrial control computer to project sinusoidal grating stripes to the surface of the underframe of the vehicle body to be measured, and the projected sinusoidal grating is imaged by 2 gigabit network CMOS cameras of each measuring unit. When the surface of the underframe fluctuates, the imaging sinusoidal grating deforms, the phase of the grating image is locally changed, and the phase change is demodulated to obtain the height change of the surface of the underframe.

Example 2

The detection system is based on the same inventive concept as that of embodiment 1, but is different from embodiment 1 in that at least 2 measurement units are arranged to realize detection of curved surface shapes at different positions of a chassis of a vehicle body to be detected, in the detection system of the embodiment, as shown in fig. 2, a measurement frame comprises a slide rail which is horizontally arranged, and the measurement units are slidably connected and installed on the slide rail. During measurement, the measurement of the surface of the long vehicle body underframe is realized through the sliding of the measuring unit on the sliding rail, and the system cost is reduced. The measuring unit can be arranged on the sliding rail in a sliding mode through the sliding seat, the sliding driving of the sliding mounting seat can adopt an automatic structural design, and then the controller controls the sliding driving, so that the automatic control and the matching of the movement and the detection of the measuring unit are realized, and the whole-course measurement is covered in a moving measurement mode.

Example 3

The embodiment describes a detection method of a curved surface type detection system of a vehicle body chassis of a railway vehicle, which adopts the detection system described in embodiment 1 or 2, and the detection method comprises the following steps:

the controller controls the grating projector to project sinusoidal grating stripes with set frequency to the surface of the underframe of the vehicle body to be measured;

the controller obtains stripe images of the surface of the underframe of the vehicle body to be measured in a corresponding single projection area through 2 calibrated image collectors in each measurement unit;

the controller controls the grating projector to project sinusoidal grating stripes on the surface of the underframe of the vehicle body to be detected to shift the phase for multiple times, and an image collector is used for acquiring a stripe image of the surface of the underframe of the vehicle body to be detected after phase shifting each time;

the controller calculates and obtains image stripe phase changes at different positions on the surface of the underframe of the vehicle body to be measured by utilizing a preset grating stripe phase-shifting demodulation algorithm according to the obtained image data and the phase corresponding to the image;

and the controller determines the surface type distribution data of the surface curved surface of the underframe of the vehicle body to be detected according to the phase change of the image stripes.

More specifically, the following is concerned.

First, camera calibration before measurement

According to the embodiment shown in the figures 1 and 2, 10 LED lamp beads in 2 rows are symmetrically arranged on two sides of a chassis of a vehicle body to be placed at a measuring station, the transverse distance between the lamp beads is 3.6m, the longitudinal placement position is in the overlapping area of the edges of the visual fields of adjacent cameras, the adjacent cameras can image the lamp beads, and the high-precision laser plane scanner is used for determining that the 10 lamp beads are in the same horizontal plane. The known positions of the 10 LED lamp beads are used for determining the installation, debugging and positioning of the measuring unit, calibrating camera parameters and splicing image data among CMOS cameras.

The camera calibration is realized by the aid of a calibration light source, and the related parameters of the camera can be determined by using the acquired image data at the light source position and the known data of the light source position by adopting the existing calibration algorithm.

Second, detection process

Before the first measurement, a standard plane is selected, and the support is adjusted to enable the standard plane and the plane of 10 LED lamp beads to be in the same plane. Starting a projector, projecting sinusoidal grating stripes to a standard plane, simultaneously acquiring images by 4 cameras, sequentially changing the phase of the projected stripes, moving the phase of pi/2 each time, continuously acquiring the images for 4 times, solving the phase of each point on the image stripes by using a phase-shifting demodulation method, taking the phase as an initial phase, and storing the initial phase in a computer, namely completing the calibration of the measuring unit.

After the vehicle body underframe to be measured is hoisted in place, the projector is controlled to project sine stripes with specific frequency to the surface of the vehicle body to be measured, the shape of the image stripes can be changed due to the change of the surface relief of the vehicle body underframe, the phase of the stripes is changed, the camera collects 4 frames of images during each phase shift, and the phase of each point on the image stripes is solved by using a phase shift method.

In the measuring process, the camera carries out sampling for 4 times in each measuring period, the projected stripes move by pi/2 phase in the length direction of the vehicle body between each sampling, and the gigabit network industrial CMOS camera respectively obtains surface stripe images at each position of the underframe.

The CMOS camera transmits the data to an industrial control computer, and the industrial control computer solves the phase change of the image stripes by a grating stripe phase-shifting demodulation method to obtain the surface profile distribution data of the surface of the underframe.

The sinusoidal grating stripes respectively shift the phase of 0, pi/2, pi and 3 pi/2, and the stripe images collected by the CMOS camera respectively correspond to I₀(x,y)、I_π/2(x,y)、I_π(x, y) and I_3π/2(x, y), then the four sinusoidal raster images are represented as:

wherein A represents the background light intensity, B represents the modulation amplitude of the fringes, and I (x, y) represents the light intensity of a point with coordinates (x, y), and the corresponding phase position of any point (x, y)Comprises the following steps:

solving the phase of each point on the image by using the above formulaAnd comparing the phase with the initial phase calibrated in advance to obtain the phase variation of each point on the underframe of the vehicle body to be measured, namely the surface profile data.

The above is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.