Point laser plane scanning tracking method

Abstract

The invention discloses a point laser plane scanning and tracking method. The method specifically comprises the steps that S1, the installation pose of a point laser sensor on a flange coordinate system is obtained through a parameter calibration process; s2, constructing a position expression of a sampling point under a robot coordinate system; s3, continuously measuring in a specified period in the movement process of the robot, creating a point laser distance data queue and a robot pose data queue, carrying out dislocation matching, and then constructing pose-distance matching data; s4, constructing a surface point cloud data queue based on the posture-distance matching data of the lower position at a certain moment; s5, when entering a tracking state, screening an optimal point in the surface point cloud data queue to serve as a reference point; and S6, calculating the correction amount of the pose of a tail end tool installed on the robot by using the reference point, calculating an instruction point based on the correction amount, and controlling the robot to move by taking the instruction point as a target point. Real-time data scanning and track correction can be realized by using simple point laser equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial robots, and in particular relates to a point laser plane scanning and tracking method. Background Art

[0002] Industrial robots are general-purpose machines with multiple degrees of freedom, multiple functions and reprogrammable functions. They play an important role in many fields such as electronics, machinery and automation. Industrial robots have the advantages of high precision, good stability and large load, which not only improve the efficiency and quality of production operations, but also reduce the labor intensity of workers. The development of industrial robots plays an important role in improving the labor productivity of the manufacturing industry, reducing labor intensity and production costs of enterprises, enhancing the international competitiveness and product quality of products, improving working conditions and working environment, reducing environmental pollution, and achieving energy conservation and consumption reduction.

[0003] When industrial robots are used in scenarios such as laser cleaning, spraying, and surface treatment, they need to maintain a constant height relative to the processing surface during operation. Point laser equipment is a commonly used non-contact displacement measurement sensor with advantages such as small size, high precision, no moving parts, and no impact on the surface to be processed. It is widely used in data measurement and correction scenarios. However, the point laser itself only samples distance information, and in related applications it is only used to assist other measuring equipment in achieving precise positioning and data collection. There is a lack of methods to directly use point laser measurement data to achieve trajectory scanning and tracking.

[0004] The application document with application number 202110798597.9 discloses a method for extracting three-dimensional coordinate values ​​from images in robot scenes. It mainly performs layered modeling on the XY plane image at different heights (Z) from the camera to the target surface. The camera and point laser are fixed at a suitable position at the end of the robot. The robot and the additional axis are moved in a photographing posture so that the real-time image center crosshairs fall on the target point. When the camera line of sight is basically perpendicular to the target surface, the three-dimensional coordinate value of a point on any plane is obtained, which is conducive to the robot's operation path planning. However, in this scene, the point laser is only used to supplement the depth information in the camera image, thereby converting the vertical plane point information into three-dimensional point information, and the technical solution stipulates that the robot's measurement posture must be perpendicular to the working surface.

[0005] The application document with application number 2021104768138 discloses a single-line laser combined with point laser precise positioning method, system and storage medium. It mainly uses a single-line laser radar and a servo to scan the contour of the target object before planning the trajectory of the robotic arm, and generates point cloud data. The point cloud can be processed to obtain the three-dimensional coordinate information of the corners or edges of the target object. The robotic arm carries the point laser to a specified small area for precise positioning, and plans the motion trajectory of the robotic arm according to the precisely positioned three-dimensional coordinates, with an accuracy of up to millimeter level. However, the robot must perform a point scanning process in advance before performing the processing action, and correct the robot's motion trajectory according to the results. It is not suitable for scenarios where a known processing trajectory is fine-tuned. Summary of the invention

[0006] Purpose of the invention: In order to solve the problems existing in the above-mentioned prior art, the present invention provides a point laser plane scanning and tracking method.

[0007] Technical solution: The present invention provides a point laser plane scanning tracking method, comprising the following steps:

[0008] S1: The point laser sensor is fixedly installed at the end of the robot. The point laser sensor can move and rotate with the end of the robot. The installation posture C of the point laser sensor on the flange coordinate system is obtained through the parameter calibration process;

[0009] S2: constructing a position expression of the sampling point in the robot coordinate system according to the installation position C of the point laser sensor in the flange coordinate system, the position A of the robot in the robot coordinate system, and the position B of the sampling point of the surface to be measured in the point laser measurement coordinate system;

[0010] S3: During the robot movement, continuous measurement is performed at a specified period, a point laser distance data queue and a robot posture data queue are created, misaligned matching is performed according to the actual situation, and then posture-distance matching data is constructed;

[0011] S4: Based on the pose-distance matching data at a certain moment, the installation pose C of the point laser sensor in the flange coordinate system and the expression constructed in step 2, the coordinates of the sampling point in the robot coordinate system at that moment are obtained, and a surface point cloud data queue is constructed;

[0012] S5: When entering the tracking state, the robot takes the planned trajectory point to be executed as the target, selects the best point in the surface point cloud data queue according to the principle of proximity, and uses it as the reference point for the tracking action at this time;

[0013] S6: Use the reference point to calculate the correction amount of the end tool posture installed on the robot, calculate the instruction point based on the correction amount, and control the robot to move with the instruction point as the target point.

[0014] Furthermore, the step 1 is specifically as follows:

[0015] Step 1.1: Operate the robot to move so that the measurement point of the point laser sensor is aligned with the fixed reference point and the laser data is valid;

[0016] Step 1.2: Based on the requirements of step 1.1, under the conditions of different robot postures and the same point laser distance, collect n sets of robot position-laser distance data, where the laser distance is the distance between the surface to be measured and the end point of the point laser sensor lens; based on the n sets of robot position-laser distance data, use the least squares method to calculate the position of the fixed reference point in the robot coordinate system;

[0017] Step 1.3: Move the robot based on the requirements of step 1.1, and collect another set of robot position-laser distance data. When collecting this set of data, the robot's position and point laser distance are different from those in step 1.2;

[0018] Step 1.4: Based on the position of the fixed reference point obtained in step 1.2 in the robot coordinate system and the data collected in step 1.3, calculate the coordinate values ​​corresponding to the point laser distance in step 1.2 and the laser distance in step 1.3 in the flange coordinate system, connect the two coordinates in the flange coordinate system, and obtain the installation posture of the point laser sensor based on the connection direction; finally, calculate the installation posture C of the point laser sensor in the flange coordinate system.

[0019] Furthermore, the step 2 is specifically as follows:

[0020] Step 2.1: According to the posture A of the robot in the robot coordinate system and the installation posture C of the point laser sensor in the flange coordinate system, obtain the posture of the point laser sensor in the robot coordinate system;

[0021] Step 2.3: Construct an expression for the position of the sampling point in the surface to be measured in the robot coordinate system: D = C × B × A.

[0022] Furthermore, the step 3 is specifically as follows:

[0023] Step 3.1: During the robot movement, the position B and the posture A are collected continuously at a specified period, and the collected position B is stored in the point laser distance data queue in time sequence, and the posture A is stored in the robot posture data queue in time sequence;

[0024] Step 3.2: According to the system delay of the actual sampling process, the data collection time of the two queues in step 3.1 is compared, and the two adjacent data in the queue with relatively advanced collection time are interpolated;

[0025] Step 3.3: Match the interpolated queues and output the matched pose-distance matching data (A, B).

[0026] Furthermore, the step 4 is specifically as follows: performing window average filtering on the coordinates of the sampling points calculated in step 4 in the robot coordinate system, calculating the distance between the filtered result and the last point in the surface point cloud data queue, and if the distance is greater than or equal to a preset threshold, saving the filtered result to the surface point cloud data queue, otherwise not saving;

[0027] Furthermore, the proximity principle in step 5 is specifically as follows: projecting the points in the surface point cloud data queue onto the XOY plane of the end tool coordinate system, obtaining the projection distance between the point and the XOY plane, and selecting the point with the smallest projection distance as the reference point in the current posture.

[0028] Furthermore, the step 6 is specifically as follows: converting the reference point to the end tool coordinate system, obtaining the projection distance G of the reference point in the Z-axis direction of the end tool coordinate system, calculating the deviation I, I=HG, H represents the tracking height between the preset robot trajectory and the surface to be measured, the posture of the end tool in the Z-axis translation deviation I of the end tool coordinate system, obtaining the corrected tracking point posture, using the corrected tracking point posture as the input of the PID controller, using the actual robot end posture as the feedback of the PID controller, and using the output of the PID controller as the instruction point for trajectory tracking to control the robot movement.

[0029] Furthermore, the measuring point of the point laser sensor is located in front of the tip of the end tool.

[0030] A computer storage medium stores a computer program, which implements the above-mentioned point laser plane scanning tracking method when executed by a processor.

[0031] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned point laser plane scanning and tracking method when executing the computer program.

[0032] Beneficial effects: The present invention can realize real-time data scanning and trajectory correction using a simple point laser device, decoupling the data scanning process from the trajectory correction action. The posture change in the trajectory tracking process does not affect the measurement result. Since the data is recorded in the form of surface point cloud, the point cloud data obtained by scanning can be combined with the robot's terminal posture to infer the direction of the surface normal, which is convenient for the robot to correct the operating posture of the running direction when tracking the running trajectory. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a control flow chart of the present invention;

[0034] Figure 2 This is a structural diagram of a six-joint robot in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] like Figure 1 As shown, a point laser plane scanning and tracking method of the present invention is specifically as follows:

[0037] S1: Obtain the installation position of the point laser sensor on the robot end flange coordinate system through the parameter calibration process; specifically:

[0038] S11: The robot point laser is fixedly installed at the end of the robot and can move and rotate with the end of the robot.

[0039] S12: Manually operate the robot to move so that the laser measurement point is aligned with the fixed reference point and the laser data is valid.

[0040] S13: According to the requirements of step S12, under the conditions of different robot postures and the same point laser distance, four sets of robot position-laser distance data are collected (because the laser is emitted from the origin of the point laser measurement coordinate system along the Z+ axis, the laser distance is the distance between the surface to be measured and the origin of the point laser measurement coordinate system, and the origin of the coordinate system is the end point of the point laser sensor lens as the origin), and the position of the fixed reference point in the space in the robot coordinate system can be calculated by the least squares method.

[0041] S14: Move the robot as required by step S12, and collect another set of robot position-laser distance data under the conditions of different posture and laser distance from S13. Combined with the position of the fixed reference point and the fifth set of robot position-laser distance data, the two positions of the two laser distances in the flange coordinate system can be calculated, and the installation posture of the point laser sensor can be obtained through the direction of the line connecting the two positions. The installation posture C of the point laser in the flange coordinate system can be calculated through the installation posture, the position in the flange coordinate system and the laser distance value.

[0042] This step does not require the end of the robot tool to contact an external fixed point to measure its specific position. It only needs to align with the fixed point and collect five sets of robot flange position and point laser distance information as required to complete the installation posture calibration. The operation is convenient and the measurement accuracy is high.

[0043] S2: construct an expression for the position of the sampling point in the robot coordinate system based on the distance data between the surface to be measured and the installation position of the point laser sensor measured by the point laser sensor, the installation position of the point laser sensor, and the position of the robot end flange coordinate system;

[0044] S21: According to the current posture A of the robot flange in the robot coordinate system and the installation posture C of the point laser sensor in the flange coordinate system obtained in step S14, the posture of the point laser sensor in the robot coordinate system at this time is obtained.

[0045] S22: According to the result of S21 and the position B of the surface to be measured in the point laser measurement coordinate system (that is, the position of the sampling point in the point laser measurement coordinate system), the position D of the sampling point in the robot coordinate system is obtained through the expression F(A,B,C)=C*A*B, D=F(A,B,C)=C*A*B.

[0046] S3: During the robot movement, continuous measurement is performed at a specified period, and a point laser distance data queue and a robot posture data queue are created, and the data are staggered and matched according to the actual situation to eliminate the sampling delay error;

[0047] S31: To ensure the reliability of the tracking effect, the plane scanning position should be earlier than the tracking action position. Therefore, in the trajectory movement direction during programming, the measurement point of the point laser sensor is required to be ahead of the end tool tip position.

[0048] S32: During the robot movement, the point laser measurement value B (i.e., the position of the surface to be measured in the point laser measurement coordinate system) and the robot posture A are collected continuously at a specified period, and the collection results are stored in the point laser distance data queue and the robot posture data queue in sequence.

[0049] S33: According to the system delay of the actual sampling process, the data collection time of the two queues in S32 is compared, and the two adjacent data in the queue with relatively advanced collection time are interpolated; if the time of the distance data queue is earlier than that of the robot posture data queue, the distance data queue is interpolated.

[0050] S34: Match the queues after interpolation in step S33 to compensate for the sampling delay error of the two data, and output the matched results (A, B).

[0051] This step does not require taking values ​​when the robot is stationary. Through the interpolation misalignment matching method, the error caused by sampling delay is eliminated, and the accuracy of measuring the spatial position of the sampling point during robot movement is improved.

[0052] S4: Calculate the sampling points and filter them according to the minimum spacing parameter of the sampling points to obtain the point cloud data of the measured surface;

[0053] S41: Use the posture-distance matching data (A, B) aligned along the time axis output in step S34, read the installation posture C obtained in step S14, substitute it into the scanning point calculation equation created in step S22, and obtain the scanning point data D to be processed.

[0054] S42: Perform sliding window average filtering on the scan point data D, calculate the distance between the filtered result and the last sampling point in the surface point cloud data queue, and save the result into the surface point cloud data queue E when the distance is greater than the required minimum spacing parameter of the sampling points.

[0055] S5: When entering the tracking state, the robot takes the planned trajectory point to be executed as the target, selects the best point in the point cloud according to the principle of proximity, and uses it as the reference point for the tracking action at this time;

[0056] S51: Read the target point posture of the robot in the planned teaching trajectory (the target point posture is the end tool posture in the robot coordinate system).

[0057] S52: Convert the surface point cloud data queue E output in step S42 into the end tool coordinate system.

[0058] S53: Sort the converted points according to the projection distance on the XOY plane of the end tool coordinate system, and take the point with the smallest projection distance as the reference point P in the current posture.

[0059] This step does not require the robot to keep its scanning posture unchanged. The optimal reference point is selected by sorting the vertical projection distance, eliminating the impact of the change in the distance between the point laser sampling position and the tip of the end tool, greatly improving the applicability of the tracking process.

[0060] S6: By using the reference point to compare with the target trajectory point interpolated by the teaching program, the correction amount at the end of the robot at this time can be calculated, and then the correction amount can be superimposed on the planned trajectory point to be executed to complete the trajectory tracking process.

[0061] Convert point P to the end tool coordinate system obtained in step S51, and obtain its projection distance G in the Z-axis direction of the end tool coordinate system, where G is the distance between the robot target point and the surface of the tracked object. The robot trajectory tracking function specifies the tracking height H that the robot trajectory and the surface of the tracked object should maintain, and the deviation that should be corrected is I=HG. Translate the robot target point posture along the Z-axis of the end tool coordinate system by the deviation I to obtain the corrected tracking point posture. Use the tracking point posture as the input of the PID controller, the actual robot end posture as the feedback of the PID controller, and the output of the PID controller as the final instruction point of trajectory tracking to control the robot movement.

[0062] This embodiment uses a six-axis industrial robot and a point laser device for data scanning and tracking. When working, its measurement position is about 5 cm ahead of the tool tip in the trajectory direction. The work object is a power battery tray with a discontinuous surface, and another point laser device is installed at the tool position to verify this method. The measurement direction of the point laser is consistent with the Z-axis direction of the tool. The robot used in this embodiment is as follows Figure 2 shown.

[0063] The method of this embodiment enables the six-axis industrial machine to perform scanning and tracking at a speed of 5 m / min on a discontinuous splicing plane (with a drop of 5 mm). The actual effect of the scanning and tracking process is shown in Table 1.

[0064] Table 1

[0065] Tracking Error RMS Mean Maximum Point Laser Tracking 0.26mm 0.24mm 2.67mm

[0066] The device installed on the robot tool can measure the actual distance between the tool tip and the plane, and the tracking deviation can be obtained by subtracting the tracking height set in the plane tracking instruction. As can be seen from Table 1, the present invention achieves a relatively good tracking effect.

[0067] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A point laser plane scanning tracking method, characterized in that: The steps include: S1: The point laser sensor is fixedly installed at the end of the robot. The point laser sensor can move and rotate with the end of the robot. The installation posture C of the point laser sensor on the flange coordinate system is obtained through the parameter calibration process; S2: constructing a position expression of the sampling point in the robot coordinate system according to the installation position C of the point laser sensor in the flange coordinate system, the position A of the robot in the robot coordinate system, and the position B of the sampling point of the surface to be measured in the point laser measurement coordinate system; S3: During the robot movement, continuous measurement is performed at a specified period, a point laser distance data queue and a robot posture data queue are created, misaligned matching is performed according to the actual situation, and then posture-distance matching data is constructed; S4: Based on the pose-distance matching data at a certain moment, the installation pose C of the point laser sensor in the flange coordinate system and the expression constructed in step 2, the coordinates of the sampling point in the robot coordinate system at that moment are obtained, and a surface point cloud data queue is constructed; S5: When entering the tracking state, the robot takes the planned trajectory point to be executed as the target, selects the best point in the surface point cloud data queue according to the principle of proximity, and uses it as the reference point for the tracking action at this time; S6: Use the reference point to calculate the correction amount of the end tool posture installed on the robot, calculate the instruction point based on the correction amount, and control the robot to move with the instruction point as the target point.

2. A point laser plane scanning tracking method according to claim 1, characterized in that: The step 1 is specifically as follows: Step 1.1: Operate the robot to move so that the measurement point of the point laser sensor is aligned with the fixed reference point and the laser data is valid; Step 1.2: Based on the requirements of step 1.1, under the conditions of different robot postures and the same point laser distance, collect n sets of robot position-laser distance data, where the laser distance is the distance between the surface to be measured and the end point of the point laser sensor lens; based on the n sets of robot position-laser distance data, use the least squares method to calculate the position of the fixed reference point in the robot coordinate system; Step 1.3: Move the robot based on the requirements of step 1.1, and collect another set of robot position-laser distance data. When collecting this set of data, the robot's position and point laser distance are different from those in step 1.2; Step 1.4: Based on the position of the fixed reference point obtained in step 1.2 in the robot coordinate system and the data collected in step 1.3, calculate the coordinate values ​​corresponding to the point laser distance in step 1.2 and the laser distance in step 1.3 in the flange coordinate system, connect the two coordinates in the flange coordinate system, and obtain the installation posture of the point laser sensor based on the connection direction; finally, calculate the installation posture C of the point laser sensor in the flange coordinate system.

3. A point laser plane scanning and tracking method according to claim 1, characterized in that: The step 2 is specifically as follows: Step 2.1: According to the posture A of the robot in the robot coordinate system and the installation posture C of the point laser sensor in the flange coordinate system, obtain the posture of the point laser sensor in the robot coordinate system; Step 2.3: Construct an expression for the position of the sampling point in the surface to be measured in the robot coordinate system: D = C × B × A.

4. The point laser plane scanning and tracking method according to claim 1, characterized in that: The step 3 is specifically as follows: Step 3.1: During the robot movement, the position B and the posture A are collected continuously at a specified period, and the collected position B is stored in the point laser distance data queue in time sequence, and the posture A is stored in the robot posture data queue in time sequence; Step 3.2: According to the system delay of the actual sampling process, the data collection time of the two queues in step 3.1 is compared, and the two adjacent data in the queue with relatively advanced collection time are interpolated; Step 3.3: Match the interpolated queues and output the matched pose-distance matching data (A, B).

5. The point laser plane scanning tracking method according to claim 1, characterized in that: The step 4 is specifically as follows: performing window average filtering on the coordinates of the sampling points calculated in step 4 in the robot coordinate system, calculating the distance between the filtered result and the last point in the surface point cloud data queue, and if the distance is greater than or equal to a preset threshold, saving the filtered result to the surface point cloud data queue, otherwise not saving.

6. The point laser plane scanning tracking method according to claim 1, characterized in that: The proximity principle in step 5 is specifically as follows: projecting the points in the surface point cloud data queue onto the XOY plane of the end tool coordinate system, obtaining the projection distance between the point and the XOY plane, and selecting the point with the smallest projection distance as the reference point in the current posture.

7. The point laser plane scanning and tracking method according to claim 1, characterized in that: The step 6 is specifically as follows: converting the reference point to the end tool coordinate system, obtaining the projection distance G of the reference point in the Z-axis direction of the end tool coordinate system, calculating the deviation I, I=HG, H represents the tracking height between the preset robot trajectory and the surface to be measured, the Z-axis translation deviation I of the end tool posture in the end tool coordinate system, obtaining the corrected tracking point posture, using the corrected tracking point posture as the input of the PID controller, using the actual robot end posture as the feedback of the PID controller, and using the output of the PID controller as the instruction point for trajectory tracking to control the robot movement.

8. The point laser plane scanning and tracking method according to claim 1, characterized in that: The measuring point of the point laser sensor is located in front of the end tool tip.

9. A computer storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, a point laser plane scanning and tracking method as described in any one of claims 1 to 8 is implemented.

10. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, a point laser plane scanning and tracking method as described in any one of claims 1 to 8 is implemented.

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