A Spraying Path Planning Method and System for an Industrial Robot with a Rotary Table

Abstract

The present invention belongs to the technical field of robot spraying path generation, and specifically discloses a spraying path planning method and system for an industrial robot plus a turntable, which includes: determining an initial spraying path and an initial spraying posture according to a complex curved surface part model; determining other curved surfaces that may cause interference, and adjusting the initial spraying posture to obtain a non-interfering spraying posture; constructing a conversion relationship between the robot tool coordinate system and the spraying workpiece coordinate system based on the non-interfering spraying posture to obtain the correlation relationship between the robot spraying redundant angle and the turntable rotation redundant angle; constructing an optimization model, with the robot spraying joint efficiency as the optimization goal, the robot spraying redundant angle and the turntable rotation redundant angle as the optimization variables, considering the robot spraying reachability; and then based on the correlation relationship, using the differential evolution algorithm to solve the optimization model to obtain the robot spraying path and the turntable rotation redundant angle. The present invention can achieve smooth movement of the robot and the turntable of the positioner during spraying.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot spraying path generation, and more specifically, relates to a spraying path planning method and system for an industrial robot plus a turntable. Background Art

[0002] At present, with the rapid development of science and technology, complex curved surface parts are increasingly widely used in fields such as aerospace, automotive, and shipbuilding. Due to the high-temperature working environment of aeroengines, it is often necessary to perform plasma spraying on the surface of parts to cover thermal barrier coatings to enhance their surface strength and extend their service life. The processing quality of the plasma spraying process is of great significance for ensuring the yield and service performance of parts. Such parts have structural characteristics such as complex curved surfaces and small spacing. Currently, industrial robots are mostly used to clamp plasma spraying tools and cooperate with a one-degree-of-freedom turntable for spraying. Currently, the method of manual teaching is mostly used to generate paths. Due to the characteristics of plasma spraying, it is necessary to ensure that the axis of the flame flow is perpendicular to the spraying surface as much as possible. However, the paths generated by teaching cannot optimally consider the flame flow angle when adjusting interference, and there are redundant angles of end rotation and redundant angles of turntable rotation during the spraying process. Optimizing this can effectively improve the movement efficiency of the robot and reduce the speed fluctuation phenomenon. Therefore, it is necessary to study the pose optimization and redundant angle optimization during the robot spraying process.

[0003] Through the above analysis, the problems and defects existing in the prior art are as follows:

[0004] (1) The method of manual teaching cannot accurately ensure the angular relationship between the robot spraying flame flow and the spraying surface.

[0005] (2) The method of manual teaching does not consider the redundant degrees of freedom of the robot and the redundant degrees of freedom of the turntable during the robot spraying process, which can improve the spraying efficiency and stability of the robot.

[0006] (3) The method of manual teaching is applicable to the scenario of turntable split drive, and turntable linkage can reduce the commutation time and improve the spraying efficiency.

[0007] The difficulties in solving the above problems and defects are as follows:

[0008] The method of manual teaching cannot theoretically guarantee the spraying effect and requires strict theoretical derivation. Among them, the robot kinematics algorithm and redundant angle planning algorithm involved need to be jointly optimized in combination with the actual calibrated tool data and turntable data, and the calculation difficulty is large. Summary of the Invention

[0009] In view of the above deficiencies or improvement requirements of the prior art, the present invention provides a spraying path planning method and system for an industrial robot plus a turntable, aiming to improve the smoothness of the robot's movement during plasma spraying of the robot, obtain better coating quality, and improve spraying efficiency.

[0010] To achieve the above object, according to the first aspect of the present invention, a spraying path planning method for an industrial robot plus a turntable is proposed, including the following steps:

[0011] S1. According to the complex surface part model, obtain the surface parameters, and then determine the initial spraying path and the initial spraying posture;

[0012] S2. According to the surface to be sprayed, determine other surfaces that may cause interference, so as to adjust the initial spraying posture and obtain a non-interfering spraying posture;

[0013] S3. Based on the non-interfering spraying posture, construct the transformation relationship between the robot tool coordinate system and the sprayed workpiece coordinate system, and then obtain the correlation relationship between the redundant angle of the robot spraying and the redundant angle of the turntable rotation;

[0014] S4. Construct an optimization model, specifically with the efficiency of the robot spraying joint as the optimization goal, the redundant angle of the robot spraying and the redundant angle of the turntable rotation as the optimization variables, considering the reachability of the robot spraying; and then based on the correlation relationship, solve the optimization model to obtain the robot spraying path and the redundant angle of the turntable rotation.

[0015] As a further preference, in step S2, the non-interfering spraying posture Specifically:

[0016]

[0017] Among them, is the initial spraying posture; establish a local path point coordinate system with the normal vector of the surface at the path point as the z-axis and the tangent vector as the x-axis, α and β are the angles of rotation of the initial spraying posture around the x-axis and y-axis respectively, and R x (α), R y (β) are the rotation matrices around the x-axis and y-axis respectively;

[0018] Adopt the OPCODE interference detection algorithm to detect the interference situation, and obtain the non-interfering spraying posture by iteratively adjusting α and β.

[0019] As a further preference, step S3 specifically includes:

[0020] Calibrate the rotation center of the external turntable and the sprayed workpiece coordinate system when the turntable rotates 0 degrees; and then obtain the relationship between the redundant angle θ of the turntable rotation and the sprayed workpiece coordinate system as:

[0021] T wcsθ = T turntable · rotz(θ) · inv(T turntable ) · T wcs0

[0022] where T wcsθ represents the rotation matrix of the spraying workpiece coordinate system when the turntable rotates by θ degrees, and T wcs0 represents the rotation matrix of the spraying workpiece coordinate system when the turntable rotates by 0 degrees, and T turntable represents the rotation matrix of the coordinate system with the turntable rotation center at 0 degrees. inv() represents the inverse of the matrix, and rotz(θ) is the rotation matrix for rotating by θ degrees around the z-axis;

[0023] Calibrate the robot tool coordinate system. Combining with robot kinematics, we have:

[0024]

[0025] where γ is the redundant angle of the robot spraying, is the spraying posture without interference, T b is the posture of the robot end joint, and T tcp represents the rotation matrix of the robot tool coordinate system;

[0026] Thus, the conversion relationship between the robot tool coordinate system and the spraying workpiece coordinate system is obtained. At the same time, based on the spraying workpiece coordinate system, the correlation relationship between the redundant angle θ of the robot spraying and the redundant angle γ of the turntable rotation is established.

[0027] As a further preference, the robot tool coordinate system is calibrated using the double four-point calibration method.

[0028] As a further preference, in step S4, the optimization model is specifically:

[0029]

[0030]

[0031] where Φ smooth is the objective function, i represents the path point, N is the total number of path points, j represents the robot joint, and M is the total number of robot joints; w j is the corresponding weight of the j-th robot joint, Δt i-1 is the running time from path point i - 1 to path point i, is the joint position of the j-th robot joint at the i-th path point; f -1 (·) is the inverse kinematics of the robot, J i is the joint position of the robot joint at the i-th path point, γ max , θ maxis the maximum value of the change in the redundant angle of the turntable rotation and the redundant angle of the robot spraying; J min and J max are respectively the minimum and maximum values of the robot joint limits, is the condition number of J i , and δ1 is the singular avoidance coefficient.

[0032] As a further preference, in step S4, based on the correlation between the redundant angle θ of the robot spraying and the redundant angle γ of the turntable rotation, the differential evolution algorithm is used to solve the optimization model to obtain the robot spraying path and the redundant angle of the turntable rotation.

[0033] As a further preference, in step S1, the initial spraying path is determined by the equal arc length method, and then the normal direction of the path point is used as the initial spraying posture.

[0034] According to the second aspect of the present invention, there is provided a spraying path planning system for an industrial robot with a turntable, including a processor for executing the above-mentioned spraying path planning method for the industrial robot with a turntable.

[0035] According to the third aspect of the present invention, there is provided a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, the above-mentioned spraying path planning method for the industrial robot with a turntable is implemented.

[0036] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following technical advantages are mainly possessed:

[0037] 1. According to the structural characteristics of complex curved surface parts and the spraying process, in combination with the working environment of the robot plus an external turntable as a positioner for linkage, the present invention avoids interference during spraying through attitude adjustment, and then realizes the high-efficiency and stability of robot spraying by optimizing the redundant angle of the robot end and the redundant angle of the turntable, thereby obtaining better coating quality.

[0038] 2. Based on the correlation between the redundant angle of the robot spraying and the redundant angle of the turntable rotation, the present invention solves the constructed optimization model to obtain the optimal solutions of the spraying path and the redundant angle, and at the same time prevents the spraying speed from fluctuating due to the too-fast changes of the turntable and the end through the setting of constraint conditions. Description of the Drawings

[0039] Figure 1 is the flow chart of the spraying path planning method for the industrial robot with a turntable according to the embodiment of the present invention;

[0040] Figure 2 is the schematic diagram of the equipment when the robot with a turntable performs plasma spraying according to the embodiment of the present invention;

[0041] Figure 3In (a) and (b) are schematic diagrams of the center points used for double four-point calibration at the end of the embodiment of the present invention;

[0042] Figure 4 In (a) and (b) are schematic diagrams of a complex curved surface part and a path diagram of the embodiment of the present invention;

[0043] Figure 5 In (a) and (b) are schematic diagrams of the redundant degrees of freedom of the spraying turntable and the redundant degrees of freedom at the end of the spraying tool of the embodiment of the present invention;

[0044] Figure 6 is a schematic diagram of the speed under the linkage of the robot positioner and the operation of a single robot in the embodiment of the present invention.

[0045] In all the drawings, the same reference numerals are used to represent the same elements or structures, where: 1-robot body, 2-spraying tool, 3-complex curved surface part, 4-external turntable. Detailed implementation manners

[0046] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] A spraying path planning method for an industrial robot with a turntable provided by an embodiment of the present invention, and the spraying equipment involved includes a robot body 1, a spraying tool 2, a complex curved surface part 3, and an external turntable 4. As Figure 2 shown, the spraying tool 2 is clamped and fixed at the end of the robot body 1 through a special fixture, and the complex curved surface part 3 and the external turntable 4 are bolted through a special fixture. At the same time, a coordinate system for robot spraying is established as Figure 2 shown, where the base coordinate system is {base}, the robot tool coordinate system (i.e., the spraying end coordinate system) is {tcp}, the spraying workpiece coordinate system is {wcs}, and the rotation center of the external turntable is {turntable}.

[0048] Specifically, the spraying path generation method, as Figure 1 shown, includes the following steps:

[0049] S1. According to the CAD model of the complex curved surface part, as Figure 4 shown, with the help of the UG secondary development platform, surface parameters are obtained, the initial spraying path is determined by the equal arc length method, and the normal direction of the path point is used as the initial spraying posture;

[0050] S2. Select other surfaces that may cause interference according to the surface to be sprayed, use the interference module to detect interference and adjust the posture, and consider the spraying angle constraint to obtain a non-interfering spraying posture;

[0051] S3. Calibrate the robot tool coordinate system, the rotation center of the turntable, and the position of the workpiece coordinate system of the turntable at the initial angle (0 degrees) according to the spraying working space, establish the kinematic conversion relationship of the robot spraying workstation, and calibrate the workpiece coordinate system of the spraying, so as to determine the correlation relationship between the two redundant angles;

[0052] S4. According to the calibrated spraying coordinate system, with the robot spraying joint efficiency as the optimization goal, the robot spraying redundant angle and the turntable rotation redundant angle as the optimization variables, and considering the reachability of the robot spraying, construct an optimization model; use the optimization method to solve to obtain the optimized robot spraying path and the turntable rotation angle.

[0053] Further, in step S1, the initial path of the robot spraying is determined by the equal arc length method, and the normal direction of the path point is used as the initial spraying posture, specifically including:

[0054] The pose information of plasma spraying uses the normal vector of the surface at the spraying point as the Z-axis and the tangent vector as the X-axis, and establishes a local path point coordinate system according to the right-hand screw rule, and is converted into ZYX Euler angles, then there are:

[0055]

[0056] Among them, are the coordinates and ZYX Euler angles of the spraying path points in the workpiece coordinate system of the spraying, and N is the number of spraying points.

[0057] Further, in step S2, obtaining a non-interfering spraying posture specifically includes:

[0058] According to in step S1,

[0059]

[0060] Convert it to obtain the initial attitude rotation matrix of the spraying point i as: At the initial attitude, since the spraying axis is a theoretical value, the spraying axis is strictly perpendicular to the spraying surface. Due to the complexity of the part, there will be an interference phenomenon between the spraying tool and the part. Adjust the initial attitude to avoid interference. The specific method is that the initial attitude of the end effector rotates by α around the x-axis and β around the y-axis, and the rotated attitude

[0061]

[0062] Whether there is interference can be determined by using the interference checking module built in UG or by calling other interference checking algorithms. By continuously iterating and adjusting α and β, a spraying posture without interference can be obtained, and the spraying angle can be controlled. Preferably, the OPCODE interference detection algorithm is used for detection.

[0063] Further, step S3 specifically includes:

[0064] Calibrate the robot tool coordinate system {tcp} using the double four-point calibration method. Due to the plasma spraying process, the spraying end is an ion flame, without an actual spraying end tip, and the spraying range is 110 - 150 mm, without a confirmed tip. Therefore, in the present invention, the spraying end direction is calibrated by calibrating the end with two tips twice. Two tips with different lengths (l1, l2) are clamped to the robot end in a way that coincides with the spraying flame. l1 < l2. As Figure 3 shown, in this embodiment, l1 = 80 mm and l2 = 130 mm; two spraying tips A1 and A2 with different lengths at the end are obtained through two four-point calibrations, and the direction of the vector is calculated, which is the actual direction of the spraying flame at the end; then the coordinate points of different spraying distances l are as shown in the following formula (4), and the robot tool coordinate system T tcp .

[0065]

[0066] Calibrate the rotation center of the external turntable {turntable} and the spraying workpiece coordinate system {wcs0} of the turntable at 0 degrees, and obtain the relationship between the turntable rotation angle θ and the spraying workpiece coordinate system {wcs θ} as:

[0067] T wcsθ = T turntable ·rotz(θ)·inv(T turntable )·T wcs0 (5)

[0068] Among them, T wcsθ represents the rotation matrix of the spraying workpiece coordinate system when the turntable rotates θ degrees, T turntable represents the coordinate system rotation matrix of the turntable rotation center at 0 degrees, inv() represents the inverse of the matrix, and rotz(θ) is the rotation matrix rotating θ around the z-axis, and its specific form is

[0069] Combined with robot kinematics, the closed kinematic chain of robot spraying is obtained as:

[0070]

[0071] Among them, the turntable rotation angle θ and the end rotation angle γ are redundant angles, so formula (6) can be changed to:

[0072]

[0073] Among them, is the spraying posture without interference, T b is the posture of the robot end relative to the base coordinate system, T tcp represents the robot tool coordinate system;

[0074] Then, by combining equations (5) and (7), the correlation relationship between the redundant angle of robot spraying and the redundant angle of turntable rotation can be obtained.

[0075] Furthermore, in step S4, taking the efficiency of the robot spraying joint as the optimization goal, this embodiment takes a 6-degree-of-freedom robot as an example for illustration. Since the spraying performs a five-dimensional task, and the robot plus the linkage positioner has 7 degrees of freedom, there are two redundant degrees of freedom. Therefore, taking the redundant angle γ of robot spraying and the redundant angle θ of turntable rotation as the optimization variables, as Figure 5 shown, considering the reachability of robot spraying, the optimized robot spraying path and the turntable rotation angle are obtained, specifically:

[0076] First, an optimization model based on the smoothness of robot spraying motion is established. The smoothness and motion efficiency of the robot motion can be represented by the weighted sum of squares of the speeds of the robot joints [J1, J2,..., J M-1 , J M :

[0077]

[0078] Among them, w j is the corresponding joint weight and can be freely adjusted.

[0079] Finally, the optimization model is obtained as:

[0080]

[0081] Among them, Φ smooth is the objective function, i represents the path point, N is the total number of path points, j represents the robot joint, M is the total number of robot joints, and in this embodiment, M = 6; w j is the corresponding weight of the jth robot joint, Δt i-1 is the running time from path point i - 1 to path point i, is the joint position of the jth robot joint at the ith path point;

[0082] f -1 (·) is the inverse kinematics of the robot, J i is the joint position of the robot joint at the ith path point, γ max , θ maxis the maximum value of the change in the redundant angle of the turntable rotation and the redundant angle of the robot spraying; J min and J max are respectively the minimum and maximum values of the robot joint limit, is the condition number of J i , and δ1 is the singular avoidance coefficient. This optimization task is high-dimensional and nonlinear. In order to obtain the optimal γ and θ, the differential evolution algorithm (DE) is used to solve the overall optimal solution in the multi-dimensional space, and the optimized joint path and the degree of the redundant angle of the turntable are obtained. The differential evolution algorithm is divided into four steps: initializing the population, mutation, crossover, and selection. Mutation and crossover are used to explore the search space; the selection process is used to retain the information of promising individuals.

[0083] As Figure 6 shown, it is a schematic diagram of the speed under the linkage of the robot positioner and the operation of a single robot after optimization. It can be noted that the running speed of the robot under the linkage of the positioner is more stable and has higher efficiency.

[0084] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated designed hardware. Those of ordinary skill in the art can understand that the above devices and methods can be implemented using computer-executable instructions and / or included in the processor control code, for example, such code is provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuits of programmable hardware devices such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips and transistors, or field programmable gate arrays and programmable logic devices, can also be implemented by software executed by various types of processors, or can be implemented by a combination of the above hardware circuits and software, such as firmware.

[0085] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A spraying path planning method for an industrial robot plus a turntable, characterized in that It includes the following steps: S1. According to the complex surface part model, obtain the surface parameters, and then determine the initial spraying path and the initial spraying posture; S2. According to the surface to be sprayed, determine other surfaces that may cause interference, so as to adjust the initial spraying posture and obtain a non-interfering spraying posture; S3. Based on the non-interfering spraying posture, construct the transformation relationship between the robot tool coordinate system and the sprayed workpiece coordinate system, and then obtain the correlation relationship between the robot spraying redundant angle and the turntable rotation redundant angle; S4. Construct an optimization model. Specifically, take the robot spraying joint efficiency as the optimization goal, take the robot spraying redundant angle and the turntable rotation redundant angle as the optimization variables, and consider the reachability of the robot spraying; then, based on the correlation relationship, solve the optimization model to obtain the robot spraying path and the turntable rotation redundant angle; In step S2, the spraying posture without interference Specifically: Among them, is the initial spraying posture; a local path point coordinate system is established with the normal vector of the surface at the path point as the z-axis and the tangent vector as the x-axis. α and β are the angles of rotation of the initial spraying posture around the x-axis and y-axis respectively, and R x (α), R y (β) are the rotation matrices for rotation around the x-axis and y-axis respectively; Adopt the OPCODE interference detection algorithm to detect the interference situation, and obtain a non-interfering spraying posture by iteratively adjusting α and β; Step S3 specifically includes: Calibrate the rotation center of the external turntable and the sprayed workpiece coordinate system when the turntable rotates 0 degrees; then the relationship between the turntable rotation redundant angle θ and the sprayed workpiece coordinate system is: T wcsθ = T turntable · rotz(θ) · inv(T turntable ) · T wcs0 Among them, T wcsθ represents the rotation matrix of the spraying workpiece coordinate system when the turntable rotates by θ degrees, and T wcs0 represents the rotation matrix of the spraying workpiece coordinate system when the turntable rotates by 0 degrees, and T turntable represents the rotation matrix of the coordinate system with the turntable rotation center at 0 degrees. inv() represents the inverse of the matrix, and rotz(θ) is the rotation matrix that rotates by θ degrees around the z-axis; Calibrate the robot tool coordinate system. Combining with robot kinematics, there is: Among them, γ is the redundant angle of the robot spraying, is the spraying posture without interference, T b is the posture of the end joint of the robot, T tcp represents the rotation matrix of the robot tool coordinate system; Thus, obtain the transformation relationship between the robot tool coordinate system and the sprayed workpiece coordinate system, and at the same time, based on the sprayed workpiece coordinate system, establish the correlation relationship between the robot spraying redundant angle θ and the turntable rotation redundant angle γ.

2. The spraying path planning method for an industrial robot plus turntable according to claim 1, characterized in that, In step S3, the robot tool coordinate system is calibrated by using the double four-point calibration method.

3. The spraying path planning method of the industrial robot plus turntable according to claim 1, characterized in that, In step S4, the optimization model is specifically: Among them, Φ smooth is the objective function, i represents the path point, N is the total number of path points, j represents the robot joint, and M is the total number of robot joints; w j is the corresponding weight of the j-th robot joint, Δt i-1 is the running time from path point i - 1 to path point i, is the joint position of the j-th robot joint at the i-th path point; f -1 (·) is the inverse kinematics of the robot, J i is the joint position of the robot joint at the i-th path point, γ max , θ max are the maximum values of the change in the redundant rotation angle of the turntable and the redundant spraying angle of the robot; J min , J max are the minimum and maximum values of the robot joint limit respectively, is the condition number of J i , and δ1 is the singular avoidance coefficient.

4. The spraying path planning method for an industrial robot plus a turntable according to claim 3, wherein In step S4, based on the correlation relationship between the robot spraying redundant angle θ and the turntable rotation redundant angle γ, use the differential evolution algorithm to solve the optimization model to obtain the robot spraying path and the turntable rotation redundant angle.

5. The spraying path planning method for an industrial robot plus turntable according to any one of claims 1-4, characterized in that, In step S1, the initial spraying path is determined by the equal arc length method, and then the normal direction of the path point is used as the initial spraying posture.

6. A spraying path planning system for an industrial robot plus a turntable, characterized in that, It includes a processor, and the processor is used to execute the spraying path planning method of the industrial robot plus turntable according to any one of claims 1-5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it realizes the spraying path planning method of the industrial robot plus turntable according to any one of claims 1-5.

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