Calibration device and calibration method for coordinate system fusion of multiple single-line laser sensors and rotary table

Abstract

The invention discloses a calibration device for coordinate system fusion of multiple single-line laser sensors and a rotary table and a calibration method of the calibration device. The device comprises the rotary table, four small calibration balls on the side and a large calibration ball on the top, wherein the four small calibration balls and the large calibration ball are installed on the rotary table through supports. The method comprises the following steps: acquiring point cloud data of four small standard balls at different visual angles through sensors arranged at the upper part, the side part and the lower part, and processing the data to obtain a conversion matrix of coordinate systems of the lower part and the middle sensor relative to a coordinate system of the upper part sensor; meanwhile, point cloud data of different positions of the large calibration ball are collected through an upper sensor, and a conversion matrix of the upper sensor and a rotating plane coordinate system can be obtained after data processing; therefore, the three sensors and the rotary table rotation plane coordinate system can be fused through the obtained conversion matrix. The method is small in hardware size, convenient to assemble and disassemble, small in calibration data volume, simple in process and low in hardware installation precision requirement, and all six parameters of coordinate system fusion can be rapidly solved.

Description

Technical Field

[0001] The invention belongs to the technical field of automatic detection, and in particular is a calibration device and a calibration method for fusing multiple single-line laser sensors with a turntable coordinate system. Background Art

[0002] In 3D detection engineering applications, multiple single-line laser sensors are often used for joint measurement. However, since single-line laser sensors can only obtain actual position information in the Z and X directions during scanning, the difficulty of coordinate system calibration and fusion is increased. When measuring a rotating body, the world coordinate system is generally defined in the center of the turntable. Therefore, there are two types of problems to be solved. One is to fuse the coordinate systems of multiple single-line laser sensors together, and the other is to fuse the fused coordinate system with the world coordinate system of the turntable. Only in this way can the 3D shape of the object be scanned and reproduced.

[0003] Currently, most single-line laser sensor coordinate system fusion methods are not simple and efficient enough, and have high requirements for equipment installation. Summary of the invention

[0004] In view of the above problems, the present invention proposes a calibration device and a calibration method for fusing multiple single-line laser sensors with a turntable coordinate system, which realizes the scanning of the shape of the rotating body to form a three-dimensional model by fusing the coordinate systems of multiple single-line laser sensors and fusing the coordinate system of the single-line laser sensor with the turntable coordinate system. The present invention can solve all six parameters required for the fusion of the coordinate system, and has no high requirements for the hardware installation accuracy. The calibration process is simple and fast, and the calibration mechanism is compact and easy to load and unload.

[0005] A device for fusion calibration of multiple single-line laser sensors and a turntable coordinate system, comprising three single-line laser sensors, a calibration mechanism and a circular turntable;

[0006] The annular turntable is designed with a support platform; a calibration mechanism is installed on the support platform;

[0007] The three single-line laser sensors include an upper sensor located above the calibration mechanism, a lower sensor located below the calibration mechanism, and a sensor located on the side of the calibration mechanism; after the three single-line laser sensors are installed, the laser surface emitted by the sensors is close to plane A, and the rotation axis of the annular turntable is close to plane A;

[0008] The calibration mechanism comprises a T-shaped slide rail, a calibration bracket, a magnetic ball seat and a calibration ball; wherein the T-shaped slide rail is arranged along the radius of the annular turntable; the calibration bracket is installed on the T-shaped slide rail; a top magnetic ball seat is installed on the top of the calibration bracket, and a large-diameter calibration ball is magnetically fixed on the top magnetic ball seat; four side magnetic ball seats are installed on the side openings of the calibration bracket; and a small-diameter calibration ball is magnetically fixed on the side magnetic ball seats;

[0009] The two connecting columns designed on the back of the top magnetic ball seat are respectively inserted into the two connecting columns designed on the top of the calibration bracket.

[0010] The rear thread of the parallel slide groove cooperates with the connecting nut; the position of the top magnetic ball seat is adjustable; the side magnetic ball seat is installed at the side opening of the calibration bracket through a support rod; a support rod is inserted into each opening to make the axial position of the support rod adjustable; at the same time, nuts are installed on both sides of the side plate of the support rod to fix the support rod axially; the end of the support rod has a mounting plate perpendicular to the support rod; two parallel slide grooves are designed on the mounting plate to cooperate with the two connecting columns on the back side of the side magnetic ball seat.

[0011] The calibration method of the calibration device based on the above structure has the following specific steps:

[0012] Step 1: Install the calibration mechanism

[0013] The calibration mechanism is assembled on the support table through a T-shaped slide rail, and 5 calibration balls are set and fixed on corresponding magnetic ball seats.

[0014] Step 2: Calibration ball position adjustment

[0015] Adjust the position of the calibration mechanism on the T-shaped slide rail so that the large-diameter ball is about 12 mm away from the rotating axis of the annular turntable; at the same time, by adjusting the position of the annular turntable, each magnetic ball seat and the support rod, ensure that all calibration balls are simultaneously located in the laser plane emitted by the three single-line laser sensors, and four of them are small-diameter balls, and the sphere centers are not coplanar.

[0016] Step 3: Calibration Data Collection

[0017] The collected data include two groups. One group of data is that the circular turntable rotates one circle starting from the artificially set zero position on the circumference. During this process, the encoder output pulse drives three single-line laser sensors to synchronously and evenly collect point cloud data of the corresponding positions of the upper large-diameter sphere at each collection moment during the circular turntable's rotation one circle; the second group of data is when the circular turntable returns to the zero position after rotating one circle, the three single-line laser sensors collect four small-diameter spheres in turn, and obtain the surface shape point clouds of the four small-diameter spheres on the side, and obtain three groups of surface point cloud data of four small-diameter spheres under three different viewing angles.

[0018] Step 4: Process the data collected in step 3

[0019] 401: Fitting arcs to the surface point cloud data of four small-diameter spheres at three different viewing angles obtained in step 3 obtains the spatial position coordinates of the four small-diameter spheres in the measurement coordinate systems of the three single-line laser sensors.

[0020] 402: The spatial position coordinates of the four small-diameter spheres in the measurement coordinate system of the single-line laser sensor calculated in step 401 are used to calculate the transformation matrix of the lower sensor measurement coordinate system and the middle sensor measurement coordinate system relative to the upper sensor measurement coordinate system.

[0021] 403: In the upper sensor measurement coordinate system, the large-diameter sphere point cloud data at each position obtained in step 3 are fitted with an arc, and the spatial position coordinates of the center of each arc corresponding to the upper sensor measurement coordinate system are further obtained, and a three-dimensional space point corresponding to the coordinate is generated; a three-dimensional space circle in the upper sensor measurement coordinate system is formed by the generated multiple three-dimensional space points, and the rotation plane of the upper sensor relative to the circular turntable is obtained, and then the transformation matrix between the measurement coordinate system of the upper sensor and the rotation plane of the circular turntable can be calculated.

[0022] The advantages of the present invention are:

[0023] 1. The present invention is used for the calibration device of multiple single-line laser sensors and the turntable coordinate system fusion, the hardware is stable in structure, compact in size, easy to load and unload, the calibration ball has high precision and is easy to replace;

[0024] 2. The present invention is used for the calibration method of integrating multiple single-line laser sensors with the turntable coordinate system, which has a simple operation process, requires a small amount of calibration data, and is fast and efficient;

[0025] 3. The calibration of the present invention is used for the calibration device of multiple single-line laser sensors and the coordinate system of the turntable. It has no requirements on the shape of the turntable, does not need to manually find the rotation axis of the turntable, and does not require the lasers of the single-line laser sensors to be strictly coplanar. Manually adjusting the coplanarity of the lasers is very difficult and prone to deviation.

[0026] 4. The present invention is used for a calibration device for the fusion of multiple single-line laser sensors and a turntable coordinate system, and can quickly calculate all six parameters of the coordinate system fusion from a small amount of data. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure is a schematic diagram of the overall composition of the device for merging and calibrating multiple single-line laser sensors with a turntable coordinate system according to the present invention.

[0028] Figure 2 The present invention is a schematic diagram of the calibration mechanism structure used in the calibration device for fusing multiple single-line laser sensors with a turntable coordinate system.

[0029] Figure 3 Schematic diagram of the calibration bracket structure in the calibration mechanism.

[0030] Figure 4 The present invention is a flow chart of the calibration method of the device for merging calibration of multiple single-line laser sensors with a turntable coordinate system.

[0031] In the figure:

[0032] 1- Single-line laser sensor 2- Calibration mechanism 3- Ring turntable

[0033] 201-T-type slide rail 202-calibration bracket 203-magnetic ball seat

[0034] 202a- base 202b- inclined beam 202c- horizontal beam

[0035] 202d- side plate 202e- support rod 202f- mounting plate

[0036] 204- small diameter ball 205- large diameter ball 301- support table DETAILED DESCRIPTION

[0037] The present invention is used for a device for merging a plurality of single-line laser sensors with a turntable coordinate system, such as Figure 1 As shown, Figure 2 As shown, it includes three single-line laser sensors 1, a calibration mechanism 2 and a circular turntable 3.

[0038] The surface of the annular turntable 3 is designed with three support platforms 301 at equal angles in the circumferential direction, and the three support platforms 301 jointly support the detected rotating body. Before the rotating body detection, three laser sensors 1 and a calibration mechanism 2 are set to perform a fusion calibration of the three single-line laser sensors 1 and the annular turntable 301 coordinate system.

[0039] Among the three single-line laser sensors 1, the first one is set in the hollow part inside the annular turntable 3 through a bracket, and its vertical position is lower than the surface of the annular turntable 3, making it a lower sensor. The other two are arranged up and down, and are set outside the annular turntable 3 through a bracket, making them an upper sensor and a middle sensor respectively. The two share a bracket for installation, and the middle sensor is vertically higher than the lower sensor. After the three single-line laser sensors 1 are installed, the emitted surface laser is as close to plane A as possible, and the rotation axis of the annular turntable 3 is as far as possible located in the plane A. Since the three single-line laser sensors 1 make it difficult to determine the coplanarity of the emitted surfaces and the rotation axis of the annular turntable 3, a certain deviation is allowed in the adjustment of the laser surface coplanarity A and the adjustment of the rotation axis coplanarity with surface A.

[0040] like Figure 3 As shown, the calibration mechanism 2 is installed on any one of the support platforms 301, and includes a T-shaped slide rail 201, a calibration bracket 202, a magnetic ball seat 203 and a high-precision calibration ball.

[0041] Among them, the calibration bracket 202 includes a base 202a, an inclined beam 202b, a cross beam 202c, a side plate 202d, a support rod 202e and a mounting plate 202f. The base 202a is slidably connected with the T-shaped slide rail 201; the calibration bracket 202 is installed on the support platform 301 by fixing the T-shaped slide rail 201 to the surface of the support platform 301 by bolts. The T-shaped slide rail 5 needs to be set along the radius of the circular turntable 3 so that the sliding direction of the calibration mechanism 2 passes through the central axis of the circular turntable 3. The inclined beam 202 is set in the longitudinal plane A where the T-shaped slide rail is located, inclined toward the outside of the circular turntable 4, and is set at an angle of 25° with the surface of the base 201. The bottom end is connected to the top surface of the base 201 to form a whole. A platform is designed at the top of the inclined beam 202a, and the platform is parallel to the plane of the circular turntable 3 for installing the calibration ball. The side of the inclined beam 202a is provided with a connecting plate 202d, and two cross beams 202b are installed on the connecting plate 202d along the long direction of the inclined beam 202a, and the inner ends of the two cross beams 202b are connected to the connecting plate 202d to form a whole. The other side of the two cross beams 202b is connected to the inner wall of the side plate 202c to form a whole, and the side plate 202c is located in a radial section of the annular turntable 3. Four through holes are designed at equal intervals on the side plate 202c along the long direction of the inclined beam, and a support rod 202e is inserted into each through hole, so that the axial position of the support rod 202e can be adjusted. At the same time, fixing nuts are installed on the support rod 202e on both sides of the side plate 202c; after the support rod 202e is adjusted in place, the position between the support rod 202e and the side plate 202c can be fixed by tightening the fixing nuts. The end of the support plate 202e is designed with a mounting plate 202f perpendicular to the support rod 202e; the mounting plate 202f is designed with two parallel slide grooves for mounting the side magnetic ball seat 203. At the same time, two parallel slide grooves are also designed on the top platform 202d of the aforementioned inclined beam 202a for mounting the top magnetic ball seat 203.

[0042] The back sides of the side magnetic ball seat 203 and the top magnetic ball seat 203 are designed with two connecting columns; the two connecting columns on the back side of the side magnetic ball seat 203 are respectively inserted into the two parallel grooves on the mounting plate 202f and then threadedly connected to the fixing nuts; the two connecting columns on the back side of the top magnetic ball seat 203 are respectively inserted into the two parallel grooves on the top platform and then threadedly connected to the fixing nuts; thereby, the position adjustment of the side magnetic ball seat 203 and the top magnetic ball seat 203 is achieved, and when the position adjustment is fixed, the position of the side magnetic ball seat 203 and the top magnetic ball seat 203 is fixed by tightening the fixing nuts.

[0043] The calibration ball includes four small-diameter balls 204 and one large-diameter ball 205. The four small-diameter balls 204 are 38.1 mm in diameter and are respectively arranged in the concave spherical surfaces of the four side magnetic ball seats 203, and are fixed by adsorption between the magnetic ball seats 203. The large-diameter ball 205 is 50.8 mm in diameter and is arranged in the concave spherical surface of the top magnetic ball seat 203, and is fixed by adsorption between the magnetic ball seat 203.

[0044] Based on the above device, the present invention is used for a method for fusion calibration of multiple single-line laser sensors and a turntable coordinate system, such as Figure 4 As shown, the specific steps are:

[0045] Step 1: Install the calibration mechanism 2.

[0046] The calibration mechanism 2 is assembled on any supporting platform 301 through the T-shaped slide rail 201 , and five calibration balls are arranged on corresponding magnetic ball seats 203 and fixed.

[0047] Step 2: Calibration ball position adjustment

[0048] The position of the calibration mechanism 2 on the T-shaped slide rail 201 is adjusted so that the center of the large diameter ball 205 is about 12 mm away from the rotation axis of the annular turntable 3. At the same time, by adjusting the positions of the annular turntable 3, each magnetic ball seat 203 and the support rod 202e, it is ensured that all calibration balls are simultaneously located in the laser plane emitted by the three single-line laser sensors 1, and the four small diameter balls 301 have non-coplanar centers.

[0049] Step 3: Calibration Data Collection

[0050] The collected data include two groups. One group of data is that the circular turntable 3 rotates one circle from the zero position artificially set on the circumference of the circular turntable 3. During this process, the encoder outputs pulses to drive three single-line laser sensors 1 to synchronously and evenly collect point cloud data of the corresponding position of the upper large-diameter sphere 205 at each collection time during the circular turntable 3 rotates one circle; the second group of data is that when the circular turntable 3 rotates one circle and returns to the zero position, the three single-line laser sensors 1 collect four small-diameter spheres 204 in turn, and obtain the surface shape point clouds of the four small-diameter spheres 204 on the side, and obtain three groups of surface point cloud data of the four small-diameter spheres 204 under different viewing angles.

[0051] Step 4: Process the data collected in step 3.

[0052] 401 : Fitting arcs to the surface point cloud data of the four small-diameter spheres 204 at three different viewing angles obtained in step 3 is performed to obtain the spatial position coordinates of the four small-diameter spheres 204 in the measurement coordinate systems of the three single-line laser sensors 1 .

[0053] 402: The spatial position coordinates of the four small-diameter spheres 204 in the measurement coordinate system of the single-line laser sensor 1 calculated in step 401 can be used to calculate the transformation matrix of the lower sensor measurement coordinate system and the middle sensor measurement coordinate system relative to the upper sensor measurement coordinate system.

[0054] 403: In the upper sensor measurement coordinate system, the point cloud data of the large-diameter sphere 205 at each position obtained in step 3 are fitted with an arc, and the spatial position coordinates of the center of each arc corresponding to the upper sensor measurement coordinate system are further obtained, and the three-dimensional space point corresponding to the coordinate is generated; a three-dimensional space circle in the upper sensor measurement coordinate system is formed by the generated multiple three-dimensional space points, and the attitude parameters of the upper sensor relative to the rotation plane of the annular turntable 3 (the reference plane of the world coordinate system (X, Y, Z)) can be obtained (6 parameters of translation and rotation of the X, Y, and Z axes), and then the transformation matrix between the upper sensor and the world coordinate system can be calculated.

[0055] Therefore, the method mentioned above obtains that the lower sensor measurement coordinate system and the middle sensor measurement coordinate system are associated with the upper sensor measurement coordinate system; at the same time, the upper sensor measurement coordinate system is associated with the world coordinate system, and then the three single-line laser sensors 1 can be combined with the world coordinate system to realize the fusion of the three single-line laser sensors and the turntable coordinate system.

[0056] The original data obtained by the method of the present invention are respectively 4096*72 resolution and depth Figure 1 4096*1 sheets are the data of one rotation of the circular turntable 3 collected by the upper sensor, which are used to establish a connection between the upper sensor coordinate system and the circular turntable 3 coordinate system; three sheets of 4096*1 correspond to the original data of the four small balls collected by the side sensor and the lower sensor, which are used to establish a connection between the side and lower sensor coordinate systems and the upper sensor coordinate system; the collection time is within 20s, and all calibration results are calculated within 30s (since the current sensor's own resolution is 4096, the speed will also increase when the resolution is reduced). If the sensor position is slightly offset, it can be recalibrated, and other system hardware equipment can be quickly put into use without manual adjustment. In addition, the calibration mechanism 2 in the present invention adopts a modular design, which is easy to maintain and save; in the measurement system in which a single-line laser sensor and a circular turntable 3 are coordinated, this calibration method can be applied in theory, and it only needs to modify the connection method between the calibration mechanism 2 and the circular turntable 3, the size of the entire mechanism, and the size of the calibration ball.

Claims

1. A calibration device for fusing multiple single-line laser sensors with a turntable coordinate system, characterized in that: It includes three single-line laser sensors, a calibration mechanism and a circular turntable; The annular turntable is designed with a support platform; a calibration mechanism is installed on the support platform; The three single-line laser sensors include an upper sensor located above the calibration mechanism, a lower sensor located below the calibration mechanism, and a sensor located on the side of the calibration mechanism; after the three single-line laser sensors are installed, the laser surface emitted by the sensors is close to plane A, and the rotation axis of the annular turntable is close to plane A; The calibration mechanism comprises a T-shaped slide rail, a calibration bracket, a magnetic ball seat and a calibration ball; wherein the T-shaped slide rail is arranged along the radius of the annular turntable; the calibration bracket is installed on the T-shaped slide rail; a top magnetic ball seat is installed on the top of the calibration bracket, and a large-diameter calibration ball is magnetically fixed on the top magnetic ball seat; four side magnetic ball seats are installed on the side openings of the calibration bracket; and a small-diameter calibration ball is magnetically fixed on the side magnetic ball seats; The two connecting columns designed on the back of the top magnetic ball seat are respectively inserted into the two connecting columns designed on the top of the calibration bracket. The rear thread of the parallel slide groove cooperates with the connecting nut; the position of the top magnetic ball seat is adjustable; the side magnetic ball seat is installed at the side opening of the calibration bracket through a support rod; a support rod is inserted into each opening to make the axial position of the support rod adjustable; at the same time, nuts are installed on both sides of the side plate of the support rod to fix the support rod axially; the end of the support rod has a mounting plate perpendicular to the support rod; two parallel slide grooves are designed on the mounting plate to cooperate with the two connecting columns on the back side of the side magnetic ball seat.

2. A calibration device for fusing multiple single-line laser sensors with a turntable coordinate system as claimed in claim 1, characterized in that: Three support platforms are designed at equal angles on the circumference of the circular turntable to support the rotating body to be tested; when calibrating before testing, the calibration mechanism is installed on any support platform.

3. A calibration device for fusing multiple single-line laser sensors with a turntable coordinate system as claimed in claim 1, characterized in that: The calibration bracket includes a base, an inclined beam, a cross beam, a side plate, a support rod and a mounting plate; the base is slidably connected with the T-shaped slide rail; the inclined beam is arranged in the longitudinal plane A where the T-shaped slide rail is located, inclined toward the outside of the annular turntable, and the bottom end is connected with the top surface of the base to form a whole; a platform is designed at the top of the inclined beam, and the platform is parallel to the plane of the annular turntable for installing the top magnetic ball seat; a connecting plate is provided on the side of the inclined beam, and two cross beams are installed on the connecting plate along the long direction of the inclined beam, and the inner ends of the two cross beams are connected with the connecting plate to form a whole; the other side of the two cross beams is connected with the inner wall of the side plate to form a whole, and the side plate is located in a radial section of the annular turntable; a through hole is provided on the side plate for installing the support rod.

4. A calibration device for fusing multiple single-line laser sensors with a turntable coordinate system as claimed in claim 1, characterized in that: The diameter of the four small-diameter balls is 38.1 mm; the diameter of the large-diameter ball is 50.8 mm.

5. A calibration method for fusing multiple single-line laser sensors with a turntable coordinate system as claimed in claim 1, characterized in that: The specific steps are: Step 1: Install the calibration mechanism The calibration mechanism is assembled on the support table through a T-shaped slide rail, and 5 calibration balls are set and fixed on the corresponding magnetic ball seats; Step 2: Calibration ball position adjustment Adjust the position of the calibration mechanism on the T-shaped slide rail so that the large-diameter ball is about 12 mm away from the rotating axis of the annular turntable; at the same time, by adjusting the position of the annular turntable, each magnetic ball seat and the support rod, ensure that all calibration balls are simultaneously located in the laser plane emitted by the three single-line laser sensors, and the four small-diameter balls have non-coplanar centers; Step 3: Calibration Data Collection The collected data includes two groups. One group of data is that the circular turntable starts to rotate one circle from the artificially set zero position on the circumference. During this process, the encoder output pulse drives three single-line laser sensors to synchronously and evenly collect point cloud data of the corresponding positions of each collection mark on the upper large-diameter sphere during the circular turntable's rotation of one circle; the second group of data is that when the circular turntable returns to the zero position after one rotation, the three single-line laser sensors collect four small-diameter spheres in turn, and obtain the surface shape point clouds of the four small-diameter spheres on the side, and obtain three groups of surface point cloud data of four small-diameter spheres under three different viewing angles; Step 4: Process the data collected in step 3 401: fitting arcs to the surface point cloud data of four small-diameter spheres at three different viewing angles obtained in step 3 to obtain spatial position coordinates of the four small-diameter spheres in the measurement coordinate systems of three single-line laser sensors; 402: Calculate the spatial position coordinates of the four small-diameter spheres in the measurement coordinate system of the single-line laser sensor calculated in step 401, and obtain the conversion matrix of the lower sensor measurement coordinate system and the middle sensor measurement coordinate system relative to the upper sensor measurement coordinate system; 403: In the upper sensor measurement coordinate system, the large-diameter sphere point cloud data at each position obtained in step 3 are fitted with an arc, and the spatial position coordinates of the center of each arc corresponding to the upper sensor measurement coordinate system are further obtained, and a three-dimensional space point corresponding to the coordinate is generated; a three-dimensional space circle in the upper sensor measurement coordinate system is formed by the generated multiple three-dimensional space points, and the rotation plane of the upper sensor relative to the circular turntable is obtained, and then the transformation matrix between the measurement coordinate system of the upper sensor and the rotation plane of the circular turntable can be calculated.

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