CN109211166B - An on-board fast alignment device and alignment method for cabin structural parts based on wall thickness and shape constraints - Google Patents

Abstract

The invention discloses an on-board fast alignment device and alignment method for cabin structural parts based on wall thickness and shape constraints. The plane standard block is used to calibrate the position vector of the sensor, and the step block is used to calibrate the thickness gauge. Sound velocity calibration and zero calibration. Call the measurement program to collect the external profile and wall thickness information at the measuring point, and calculate the information of the inner cavity profile, move the laser displacement sensor to the corresponding measuring point, so that the inner cavity profile at the four-jaw clamping point is centered around the center of rotation It is axisymmetric to realize fast alignment of cabin parts. The present invention can be based on a numerically controlled lathe to realize rapid alignment of cabin parts on the machine, and can perform uniform treatment of wall thickness according to the constraint conditions of machining allowance. The alignment efficiency and precision are high. It has good practical value and application prospect in the study of wall thickness uniformity.

Description

An on-board fast alignment device for cabin structural parts based on wall thickness and shape constraints and its its correction method

technical field

The invention relates to the field of mechanical design and on-machine measurement, in particular to an on-machine fast alignment device and alignment method for cabin structural parts based on wall thickness and shape constraints.

Background technique

In machining, two typical cabin parts are often encountered: one is a linear rotary cabin part, and the other is a curved rotary cabin part. Since the inner wall is required to be aligned when machining the outer circle of the part, and the inner walls of the two types of parts cannot be machined, it is difficult to ensure uniform wall thickness, so it is very difficult to align the workpiece. Due to the irregular and complex shape of the inner wall of the blank, it is very difficult to design the model, and the accuracy is not easy to meet the requirements, so most of them use the method of multi-table alignment to solve this problem. However, this method inevitably has defects such as complex alignment process, low efficiency, and general accuracy; in addition, manual alignment is largely limited by operator experience, and there are great differences in alignment efficiency and accuracy, poor consistency, and possible The phenomenon of part scrapping is caused, and this method belongs to offline alignment, and its effect is not good in the face of small margin machining, and it is difficult to adapt to the production requirements of modern manufacturing automation and intelligentization. Therefore, the present invention proposes a combination of a laser displacement sensor and an ultrasonic thickness gauge to quickly realize the alignment of the cabin structure and uniform wall thickness on the machine tool.

Laser has a history of more than 50 years since it was invented in 1960. During this process, laser-related technologies have emerged in an endless stream, and their applications have become more and more extensive. Compared with general light sources, lasers have good monochromaticity and directionality, high brightness, Excellent coherence and other advantages. In aerospace, automobile industry and other fields, the requirements for high speed and high precision of surface profile measurement of various curved surfaces are getting higher and higher. Due to the advantages of small structure, fast measurement speed, high precision and non-contact, laser displacement sensor makes its It is more and more widely used in the fields of aircraft manufacturing, automobile manufacturing, and industrial automatic control. The laser displacement sensor is a non-contact measuring sensor. The single-point laser measuring head selected in the present invention is based on the triangular ranging principle, and calculates the displacement between the measured object and the sensor according to the light energy centroid variation range on the CCD receiving surface. In order to obtain the topography information of the measured surface. The basic principle of ultrasonic thickness measurement is: the propagation speed of ultrasonic waves in the same medium is stable, and a reflected pulse will be generated when encountering another medium during the propagation process, and the time from transmitting the pulse to receiving the reflected pulse is proportional to the thickness of the medium, according to the calibration Calculate the thickness of the test piece. The ultrasonic thickness gauge has high measurement accuracy and can be integrated on a CNC lathe to realize automatic measurement.

Based on the advantages of the above two measurement methods, the present invention integrates a laser displacement sensor and an ultrasonic thickness gauge on a CNC lathe, and obtains the shape information of the cabin body through efficient and accurate processing of the measurement data, and thereby realizes the rapid processing of cabin-like workpieces. Alignment, with high alignment accuracy, provides a practical basis for the integrated production mode of subsequent measurement-alignment-processing integration. In the 1990s, the measurement technology based on the three-coordinate measuring machine was called "measurement center" because of its high precision, good performance, strong versatility, and large measurement range; however, as an offline measurement method, three-coordinate The measurement is not only costly and difficult to maintain, but also requires secondary clamping and repositioning, which seriously affects the efficiency of the entire processing and measurement. With the continuous development of science and technology, in the aerospace, automobile, shipbuilding and mold industries, the production mode has gradually evolved from large batches and single varieties to small and medium batches and multiple varieties, such as blades, cylinder blocks and cylinder heads in engines, Transmission housing and brake disc, etc. In view of the complex shape and high process requirements of these parts, once a waste product occurs, it will cause great losses. Therefore, how to improve the manufacturing quality of CNC machine tools and machining centers is of great significance, and the setting of the On Machine Measurement (On Machine Measurement) function is a a very effective means. On-machine measurement is different from three-coordinate measurement. It can not only collect measurement data in real time, avoid repeated positioning and secondary clamping procedures, but also directly use the measurement results for processing error compensation to realize the integration of processing, production and measurement. It has important guiding significance to reduce auxiliary time, improve processing efficiency, improve processing accuracy, and reduce defective rate.

According to the measurement method, on-machine measurement can be divided into three types: contact type, non-contact type and composite type. Although the contact measurement has high precision, the measurement efficiency is relatively low, and it may cause damage to the measurement surface. Therefore, the laser on-machine measurement method has attracted more and more attention in production because of its high efficiency and acceptable measurement accuracy. . However, most of the current research focuses on the surface measurement of complex parts on multi-axis machining centers. This is because the degree of freedom of machining centers is relatively high, which can meet the requirements of motion path planning required in the measurement process of laser sensors to complete complex parts. surface data collection. However, on a CNC lathe, the probe mounted on the tool post can only move in translation in the x-direction and z-direction, and cannot rotate, and the translation in the y-direction is also limited, which is difficult to meet the measurement needs. Therefore, for turning parts with rotary structure features, the difficulty of surface measurement is not only whether the data acquisition is accurate, but also whether the measurement method selection and measurement path planning are reasonable, whether the data processing algorithm is accurate and effective, and whether the model reconstruction is accurate or not. in place. The present invention effectively completes the design of the measuring device and method for the rotary structural parts and the improvement of the data algorithm on the CNC lathe, realizes the laser efficient and precise on-machine measurement process of the CNC lathe parts, and provides the integration of subsequent production-measurement-processing Practical basis.

Contents of the invention

The purpose of the present invention is to solve the problems of low alignment efficiency, insufficient precision and low degree of automation of the cabin structural parts of the numerical control lathe, and then realize the fast and accurate alignment of the cabin parts on the machine, and lay the foundation for the integration of alignment measurement-processing . To this end, the present invention provides a device and method for fast alignment of cabin structural parts on-board based on wall thickness and shape constraints. An adjustable and detachable "U"-shaped clamp is designed, and a laser sensor is assembled and clamped. With the ultrasonic thickness gauge, the distance value of the outer contour of the part measuring point and the wall thickness value of the part are measured on the machine, the data processing algorithm is compiled, and the inner cavity profile information at the measuring point is calculated, which is used as the basis for the adjustment of the lathe chuck, so as to achieve The purpose of high-precision and high-efficiency alignment of parts and uniform wall thickness.

For realizing above-mentioned technical purpose, the technical scheme that the present invention takes is:

An on-machine rapid alignment device for cabin structural parts based on wall thickness and shape constraints, which includes a fixture, a laser displacement sensor, and an ultrasonic thickness gauge. The laser displacement sensor and the ultrasonic thickness gauge are respectively fixed on the fixture, and the fixture Fixed on the lathe tool holder, the two ends of the cabin structure are grasped and fixed by the lathe chuck respectively, the laser displacement sensor and the measuring head of the ultrasonic thickness gauge face the cabin structure, and the laser displacement sensor can detect the outer surface of the cabin structure The ultrasonic thickness gauge can detect the bulkhead thickness of the cabin structure, the lathe tool holder can drive the fixture to move, and the lathe chuck can flip the cabin structure.

The above-mentioned fixture is a "U"-shaped fixture. The fixture includes a fixture base. Mounting holes are provided at both ends of the fixture base. The laser displacement sensor is fixed on one end of the fixture through an adjusting screw, and the ultrasonic thickness gauge is fixed on the other end of the fixture.

The above fixture also includes a locking cover plate, which is an “Ω” type plate, the middle part of the locking cover plate presses the ultrasonic thickness gauge, and the two ends are fixed with the mounting holes on the fixture base by screws.

The above-mentioned lathe chuck is a four-jaw chuck, and the four claws of the lathe chuck grip the end of the cabin structure in an equal arc, and the claws of the two lathe chucks are staggered by 45°.

The inner cavities at both ends of the above-mentioned cabin structural member are filled with hoods for improving the rigidity of the ends of the cabin structural member.

A fast on-board alignment method for cabin structural parts based on wall thickness and shape constraints, comprising the following steps:

Step 1. Assemble the laser displacement sensor and the ultrasonic thickness gauge on the fixture respectively, and then connect the fixture with the lathe tool holder in the groove edge positioning mode. After adjusting the position, tighten and fix the fixture with the lathe tool holder through screws;

Step 2. Use the plane calibration block to calibrate the beam deflection error and height error of the laser displacement sensor, and use the step block to calibrate the sound velocity and zero position of the ultrasonic thickness gauge to ensure that the structural parts of the detection cabin measured by the laser displacement sensor The distance between the outer surface and the laser displacement sensor and the bulkhead thickness data of the cabin structural parts measured by the ultrasonic thickness gauge are true and reliable;

Step 3. Clamp the two ends of the cabin structure on the lathe chuck of the CNC lathe. The lathe chuck clamps the cabin structure with moderate strength. Set several measuring points on the cabin structure. The location is marked with a black marker;

Step 4. Call the measurement program, first use the laser displacement sensor to measure the distance value from the measuring point to the probe, and then use the ultrasonic thickness gauge to measure the wall thickness at the same position, and add the two values to get the inner cavity at this position The distance value from the surface to the probe,

Step 5. Move the tool holder of the lathe so that the laser displacement sensor is facing another measuring point, and repeat step 4; by analogy, measure the distance between the inner cavity surface and the probe at all measuring points;

Step 6. Aim at the same distance between the measuring point and the relative point rotated 180° from the measuring head, calculate the theoretical displacement at each measuring point, then move the laser displacement sensor to the measuring point, and use its reading as a reference to adjust the corresponding card The readings from the claw to the sensor are calculated values, so as to realize the fast alignment of the cabin parts.

In step 2, the standard block calibrates the beam deflection error and height error of the laser sensor as follows: Assume that the angle between the beam direction and the X-axis is α, and move the probe along the negative X direction for a distance Δx. In the laser triangulation method, the reference plane along The rotation angle of the hour hand is α, and the reading of the measuring head changes to ΔL, as shown in Figure 6, from the triangular relationship, we get: cosα=Δx/ΔL, where α is the deflection error calibration in the XOZ plane; use the height gauge to adjust on the CNC lathe Calibrate the plane of the block so that it is perpendicular to the plane of the beam, move the tool holder along the negative direction of z, take the measured average value, and denote it as L; then, rotate the calibration block clockwise around the center of rotation for different angles, denoted as βi, and the measurement path remains unchanged. The average value is recorded as Li, and the height error at different angles is recorded as ΔHi, then

ΔHi=(L-Li)×cosα/tanβi

Where: α is the sensor deflection angle

βi are different rotation angles

Take the average value and record it as ΔH. At this time, the calibration of deflection error and height error is completed, and error compensation is performed in the subsequent measurement results to improve the measurement accuracy and achieve more accurate alignment.

The method of calculating the theoretical displacement at each measuring point in step 6 is as follows:

Assume that the distance measured by the laser displacement sensor at measuring point 1 is L1, the measured value of the ultrasonic wall thickness is T1, the distance measured by the sensor at the relative point rotated 180° is L3, and the measured value of the ultrasonic wall thickness is T3, so the cavity type The distances from point 1 and point 3 to the laser displacement sensor are respectively (L1+T1) and (L3+T3), and the alignment target is L1+T1=L3+T3, but in fact the two are not equal, so the difference Half the value is the adjustment:

L = 0.5×(L1+T1-L3-T3)

The adjustment amount calculation of other measurement points is the same.

The measuring point positions are distributed on the cabin surface of the cabin structural part which is very close to the clamping place of the lathe chuck.

The device and method for on-board rapid alignment of cabin structural parts based on wall thickness and shape constraints of the present invention adopts an adjustable and detachable "U"-shaped fixture, and fixes its assembly on the numerical control through the groove edge positioning method. On the rotatable tool holder of the lathe, the sensor is calibrated by using the plane standard block, and the sound velocity of the ultrasonic thickness gauge is calibrated by using the stepped block. Then, measure the distance between the measuring point on the outer surface of the cabin part and the wall thickness of the probe, and calculate the distance from the inner cavity surface at all measuring points to the measuring probe. Combined with the coordinates of the machine tool, calculate the theoretical displacement adjustment of each claw; move the laser displacement sensor to the measuring point, and gradually adjust the claws with its reading as a reference, so as to realize fast and accurate on-machine alignment of cabin parts and uniform wall thickness. The invention realizes on-machine fast alignment of cabin structural parts with high precision, and has good practical value and application prospect in the research fields of on-machine measurement and alignment of revolving body parts.

Innovation point of the present invention is:

1. Hardware module: Design and manufacture adjustable and detachable "U"-shaped fixtures, which are assembled with sensors and thickness gauges and installed on the knife holder in the way of groove edge positioning, and the screws are tightened. The cabin parts are evenly distributed and clamped by the four-jaw chucks at both ends, and can be accurately adjusted according to the adjustment amount obtained by subsequent algorithm processing. The device is accurate in positioning, stable and reliable.

2. Software module: Use a plane standard block to calibrate the position and vector direction of the laser sensor. First, move the probe to calibrate the deflection error, and then rotate the standard block to calibrate the height error. Thickness gauges mainly rely on step blocks for sound velocity calibration and zero calibration. After the calibration is completed, the measurement program is called to collect the outer surface information and wall thickness of the cabin parts, and the inner cavity information at the measuring point is calculated accordingly; the distance between the symmetrical point and the measuring head is equal to the goal, and the distance at each measuring point is calculated. The theoretical displacement is used to solve the jaw adjustment amount and realize fast alignment. This method is simple in calculation and high in accuracy.

3. The present invention does not require major changes to the structure of the machine tool, as long as the two ends are equipped with four-jaw chucks, which increases the adaptability of the measurement and alignment system; comprehensively considering the alignment efficiency and alignment accuracy, it can optimize the alignment for the cabin Implementation scheme of on-machine alignment of body parts.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the schematic diagram of fixture;

Fig. 3 is the schematic diagram of locking cover plate;

Figure 4 is a top view of the assembly of the fixture, the laser displacement sensor and the ultrasonic thickness gauge;

Fig. 5 is a front view of the assembly of the fixture, the laser displacement sensor and the ultrasonic thickness gauge;

Fig. 6 is a schematic diagram of calibration of the beam deflection error of the laser sensor by the standard block;

Fig. 7 is a schematic diagram of a laser sensor beam shining on a cabin structure;

Fig. 8 is a schematic diagram of calibration of the beam height error of the laser sensor by the standard block.

Fig. 9 is a schematic structural diagram of a standard block;

Fig. 10 is a left side view of the standard block.

The reference signs are: clamp 1 , clamp base 11 , locking cover 12 , laser displacement sensor 2 , ultrasonic thickness gauge 3 , cover 4 , cabin structure 5 , and lathe chuck 6 .

Detailed ways

Embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings.

The present invention is based on a numerically controlled lathe, combined with the characteristics of fast measurement speed and high precision of laser sensors and ultrasonic thickness gauges, and then designing supporting fixtures to realize fast alignment of cabin parts on the machine; in addition, the compiled algorithm performs the measurement data processing, and accurately calculate the real-time adjustment of each jaw, which can effectively improve the accuracy of on-machine alignment.

The on-board rapid alignment device for cabin structural parts based on wall thickness and shape constraints of the present invention includes a fixture 1, a laser displacement sensor 2 and an ultrasonic thickness gauge 3, and the laser displacement sensor 2 and the ultrasonic thickness gauge 3 are respectively fixed on On the fixture 1, the fixture 1 is fixed on the tool holder of the lathe, and the two ends of the cabin structure 5 are grasped and fixed by the lathe chuck 6 respectively, and the measuring heads of the laser displacement sensor 2 and the ultrasonic thickness gauge 3 face the cabin structure 5, The laser displacement sensor 2 can detect the distance between the outer surface of the cabin structural member 5 and the laser displacement sensor 2, the ultrasonic thickness gauge 3 can detect the bulkhead thickness of the cabin structural member 5, the lathe tool holder can drive the clamp 1 to move, and the lathe The chuck 6 can turn over the cabin structure 5 .

In the embodiment, the clamp 1 is a "U"-shaped clamp, and the clamp 1 includes a clamp base 11. Mounting holes are provided at both ends of the clamp base 11. The laser displacement sensor 2 is fixed on one end of the clamp 1 through an adjusting screw. The ultrasonic thickness gauge 3 Fix it on the other end of fixture 1.

In the embodiment, the clamp 1 also includes a locking cover 12, which is an "Ω" type plate, the middle part of the locking cover 12 presses the ultrasonic thickness gauge 3, and the two ends are connected with the clamp base 11 by screws. The mounting holes are fixed.

In the embodiment, the lathe chuck 6 is a four-jaw chuck, and the four claws of the lathe chuck 6 are caught on the end of the cabin structure 5 in an equal arc, and the claws of the two lathe chucks 6 are staggered by 45° .

In the embodiment, the inner cavities at both ends of the cabin structure 5 are filled with hoods 4 for improving the rigidity of the ends of the cabin structure 5 .

A fast on-board alignment method for cabin structural parts based on wall thickness and shape constraints, comprising the following steps:

Step 1. Assemble the laser displacement sensor 2 and the ultrasonic thickness gauge 3 on the fixture 1 respectively, and then connect the fixture 1 with the lathe tool rest in the groove edge positioning mode. After adjusting the position, connect the fixture 1 to the lathe tool rest through screws Tighten and fix;

Step 2: Use the plane calibration block to calibrate the beam deflection error and height error of the laser displacement sensor 2, and use the step block to calibrate the sound velocity and zero position of the ultrasonic thickness gauge 3 to ensure that the detection chamber measured by the laser displacement sensor 2 The distance between the outer surface of the body structure 5 and the laser displacement sensor 2 and the bulkhead thickness data of the cabin structure 5 measured by the ultrasonic thickness gauge 3 are true and reliable;

Step 3: Clamp the two ends of the cabin structural part 5 on the lathe chuck 6 of the numerically controlled lathe, and the lathe chuck 6 clamps the cabin structural part 5 with moderate strength. point, the distribution position of the measuring point is marked with a black marker pen;

Step 4. Call the measurement program, first use the laser displacement sensor to measure the distance value from the measuring point to the probe, and then use the ultrasonic thickness gauge to measure the wall thickness at the same position, and add the two values to get the inner cavity at this position The distance value from the surface to the probe,

Step 5. Move the tool holder of the lathe so that the laser displacement sensor is facing another measuring point, and repeat step 4; by analogy, measure the distance between the inner cavity surface and the probe at all measuring points;

Step 6. Aim at the same distance between the measuring point and the relative point rotated 180° from the measuring head, calculate the theoretical displacement at each measuring point, then move the laser displacement sensor to the measuring point, and use its reading as a reference to adjust the corresponding card The readings from the claw to the sensor are calculated values, so as to realize the fast alignment of the cabin parts.

In step 2, the standard block calibrates the beam deflection error and height error of the laser sensor as follows: Assume that the angle between the beam direction and the X-axis is α, and move the probe along the negative X direction for a distance Δx. In the laser triangulation method, the reference plane along The rotation angle of the hour hand is α, and the reading of the measuring head changes to ΔL, as shown in Figure 6, from the triangular relationship, we get: cosα=Δx/ΔL, where α is the deflection error calibration in the XOZ plane; use the height gauge to adjust on the CNC lathe Calibrate the plane of the block so that it is perpendicular to the plane of the beam, move the tool holder along the negative direction of z, take the measured average value, and denote it as L; then, rotate the calibration block clockwise around the center of rotation for different angles, denoted as βi, and the measurement path remains unchanged. The average value is recorded as Li, and the height error at different angles is recorded as ΔHi, then

ΔHi=(L-Li)×cosα/tanβi

Where: α is the sensor deflection angle

βi are different rotation angles

Take the average value and record it as ΔH. At this time, the calibration of deflection error and height error is completed, and error compensation is performed in the subsequent measurement results to improve the measurement accuracy and achieve more accurate alignment.

The method of calculating the theoretical displacement at each measuring point in step 6 is as follows:

Assume that the distance measured by the laser displacement sensor 2 at measuring point 1 is L1, the measured value of the ultrasonic wall thickness is T1, the distance measured by the sensor at the relative point rotated 180° is L3, and the measured value of the ultrasonic wall thickness is T3, so the inner cavity The distances from point 1 and point 3 on the surface to the laser displacement sensor are respectively (L1+T1) and L3+T3, and the alignment target is L1+T1=L3+T3, but in fact the two are not equal, so the difference Half of is the adjustment:

L = 0.5×L1+T1-L3-T3

The adjustment amount calculation of other measurement points is the same.

The positions of the measuring points are distributed on the cabin surface of the cabin structure 5 which is very close to the clamping place of the lathe chuck 6 .

After adopting the above scheme, the present invention realizes on-machine rapid alignment of cabin parts by using a combination of laser displacement sensor and ultrasonic thickness gauge on a numerically controlled lathe, and improves the real-time alignment accuracy through data processing and algorithm solution. precision. The invention provides an on-board fast alignment mode of the structural parts of the cabin body, which reduces the auxiliary time and significantly improves the alignment efficiency.

The above are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims (7)

1. An on-board fast alignment method for cabin structural parts based on wall thickness and shape constraints, characterized in that: the on-board fast alignment device for cabin structural parts based on wall thickness and shape constraints includes a clamp (1) , laser displacement sensor (2) and ultrasonic thickness gauge (3), described laser displacement sensor (2) and ultrasonic thickness gauge (3) are respectively fixed on the fixture (1), and described fixture (1) is fixed On the lathe turret, the two ends of the cabin structure (5) are grasped and fixed by the lathe chuck (6) respectively, and the measuring heads of the laser displacement sensor (2) and the ultrasonic thickness gauge (3) face the cabin Structural part (5), described lathe tool rest can drive fixture (1) to move, and described lathe chuck (6) can turn over cabin body structural part (5); Described lathe chuck (6) is four Jaw chuck, the four claws of the lathe chuck (6) grip the end of the cabin structure (5) in an equal arc, and the claws of the two lathe chucks (6) are staggered by 45°; based on the wall thickness The on-board rapid alignment method of cabin structural parts with shape constraints includes the following steps: Step 1. Assemble the laser displacement sensor (2) and the ultrasonic thickness gauge (3) on the fixture (1) respectively, and then connect the fixture (1) to the tool post of the lathe by positioning the groove edge. After adjusting the position, place the Fixture (1) is tightened and fixed by screws and lathe tool rest; Step 2. Use the plane calibration block to calibrate the beam deflection error and height error of the laser displacement sensor (2), and use the step block to calibrate the sound velocity and zero position of the ultrasonic thickness gauge (3) to ensure that the laser displacement sensor (2) ) and the distance between the outer surface of the inspection cabin structural member (5) and the laser displacement sensor (2) and the bulkhead thickness data of the cabin structural member (5) measured by the ultrasonic thickness gauge (3) are true and reliable ; Step 3: Clamp the two ends of the cabin structural member (5) on the lathe chuck (6) of the CNC lathe, and the lathe chuck (6) clamps the cabin structural member (5) with moderate force. Several measuring points are set on the structural part (5), and the distribution positions of the measuring points are marked with a black marker; Step 4. Call the measurement program, first use the laser displacement sensor to measure the distance value from the measuring point to the probe, and then use the ultrasonic thickness gauge to measure the wall thickness at the same position, and add the two values to get the inner cavity at this position The distance value from the surface to the probe, Step 5. Move the tool holder of the lathe so that the laser displacement sensor is facing another measuring point, and repeat step 4; by analogy, measure the distance between the inner cavity surface and the probe at all measuring points; Step 6. Aim at the same distance between the measuring point and the relative point rotated 180° from the measuring head, calculate the theoretical displacement at each measuring point, then move the laser displacement sensor to the measuring point, and use its reading as a reference to adjust the corresponding card The value displayed by the claw to the laser displacement sensor is the calculated value of the theoretical displacement, so as to realize the rapid alignment of the cabin parts. 2. An on-board rapid alignment method for cabin structural parts based on wall thickness and shape constraints according to claim 1, characterized in that: the clamp (1) is a "U"-shaped clamp, and the The fixture (1) comprises a fixture base (11), and both ends of the fixture base (11) are provided with mounting holes, and the laser displacement sensor (2) is fixed on one end of the fixture (1) by adjusting screws, so The ultrasonic thickness gauge (3) described above is fixed on the other end of the fixture (1). 3. An on-board fast alignment method for cabin structural parts based on wall thickness and shape constraints according to claim 2, characterized in that: the clamp (1) also includes a locking cover (12) , the locking cover (12) is an "Ω" type plate, the middle part of the locking cover (12) presses the ultrasonic thickness gauge (3), and the two ends are connected to the fixture base (11) by screws The mounting holes are fixed. 4. An on-machine rapid alignment method for cabin structural parts based on wall thickness and shape constraints according to claim 3, characterized in that: the inner cavities at both ends of the cabin structural parts (5) are filled There is a cover (4) for improving the rigidity of the end of the cabin structural member (5). 5. An on-board rapid alignment method for cabin structural parts based on wall thickness and shape constraints according to claim 1, characterized in that: in step 2, the plane calibration block is used for the beam deflection error and height error of the laser displacement sensor The calibration method is as follows: Assuming that the angle between the beam direction and the X-axis is α, move the probe along the negative direction of X for a distance Δx, and rotate the reference plane clockwise by the angle α in the laser triangulation method, and the reading of the probe changes to ΔL, which is determined by the triangulation Relationship, get: cosα=Δx/ΔL, where α is the deflection error calibration in the XOZ plane; use the height gauge to adjust the plane calibration block plane on the CNC lathe to make it perpendicular to the beam plane, move the tool holder along the negative z direction, take The measured average value is recorded as L; then, the plane calibration block is rotated clockwise around the center of rotation by different angles, which is recorded as βi, the measurement path remains unchanged, and the average value is recorded as Li, and the height error at different angles is recorded as ΔHi, then ΔHi=(L-Li)×cosα/tanβi; Where: α is the deflection angle of the sensor; βi are different rotation angles; i is the serial number; Take the average value and record it as ΔH. At this time, the calibration of deflection error and height error is completed, and error compensation is performed in the subsequent measurement results to improve the measurement accuracy and achieve more accurate alignment. 6. A method for quickly aligning cabin structural parts on-board based on wall thickness and shape constraints according to claim 1, characterized in that: the method for calculating the theoretical displacement at each measuring point in step 6 is as follows: Suppose the distance value measured by the laser displacement sensor (2) at measuring point 1 is L1, the measured value of the ultrasonic wall thickness is T1, and the measured distance value of the sensor at the relative point 3 of its rotation of 180° is L3, and the measured value of the ultrasonic wall thickness is T3, Therefore, the distances between the inner cavity surface points corresponding to points 1 and 3 and the laser displacement sensor are (L1+T1) and (L3+T3) respectively, and the alignment target is L1+T1=L3+T3, but in fact both are not equal, so half their difference is the adjustment: L = 0.5×(L1+T1-L3-T3) The adjustment amount calculation of other measurement points is the same. 7. An on-machine rapid alignment method for cabin structural parts based on wall thickness and shape constraints according to claim 6, characterized in that: the measuring points are distributed at a distance from the clamping place of the lathe chuck (6) The cabin profile of the nearest cabin structure (5).