An inverse solution optimization method and system for coupled motion of water jet machine tools

Abstract

The present invention discloses an inverse solution optimization method for coupled motion of a water jet machine tool with redundant degrees of freedom, comprising the following steps: S1: building a machine tool hardware system and establishing a machine tool DH model; S2: proposing three redundant parameter schemes according to the characteristics of the water jet machine tool; S3: optimizing the redundant parameter ρ 1 , 2 Optimize parameters; S4: Use geometric method to obtain inverse solution; S5: According to the characteristics of water jet processing, compare the advantages and disadvantages of three schemes after parameter optimization for the current working conditions and make a decision, select the best set of schemes to calculate the inverse solution and input it into the machine tool for actual processing. The present invention does not require complex station planning, can avoid the problem of water jet overcutting in sub-station processing, and can realize smooth coupling movement of the eight axes of the water jet machine tool to ensure high processing quality.

Description

Technical Field

[0001] The present invention relates to the technical field of processing equipment, in particular to an inverse solution optimization method and system for coupled motion of a water jet machine tool. Background Art

[0002] With the development of modern processing technology, many special processing methods have gradually matured and are applied to many different types of production and processing scenarios. Among them, water jet processing is one of the few cold processing methods and is widely used. However, under some extreme processing conditions, the degree of freedom of traditional five-axis linkage machine tools is inevitably a bit stretched. Therefore, installing a general six-axis robot on an external moving axis has become a better solution.

[0003] However, how to allocate the motion priority between the external axis and the six-axis robot has become a problem. In the past, more common methods were to use the robot and the external mobile axis to perform time-sharing motion to decouple the motion of the two. In the process of completing the entire processing task, the robot was moved to different positions through position planning to process multiple decomposed small processing tasks. This method requires the water jet to be kept stable at the end of the previous processing trajectory when the robot moves, which will cause overcutting problems. Therefore, how to achieve coupled motion between the robot and the external axis to avoid overcutting problems during the sub-station process has become a problem. There is also little research on how industrial machine tools can perform processing through stable coupled motion. Summary of the invention

[0004] In order to solve the problems of the prior art, the purpose of the present invention is to overcome the shortcomings of the existing technology and provide an inverse optimization method and system for the coupled motion of a water jet machine tool. It is designed for industrial processing, proposes a variety of redundant parameter schemes for water jet machine tools, and optimizes them. At the same time, it takes into account the characteristics of processing stability and flexibility, with high efficiency and diverse application scenarios.

[0005] In order to achieve the above invention purpose, the present invention adopts the following technical solution:

[0006] An inverse solution optimization method for coupled motion of a water jet machine tool is used to achieve smooth coupled motion between a robot and an external axis in a redundant degree of freedom machine tool, comprising the following steps:

[0007] S1: Build the machine tool hardware system and establish the machine tool DH model;

[0008] S2: Three redundant parameter schemes are proposed according to the characteristics of water jet machine tools;

[0009] S3: Optimize the redundant parameters ρ1 and ρ2;

[0010] S4: Use geometric method to obtain the inverse solution;

[0011] S5: According to the characteristics of water jet machining, compare the advantages and disadvantages of three schemes after parameter optimization for the current working conditions and make a decision. Select the best set of schemes to calculate the inverse solution and input it into the machine tool for actual machining.

[0012] For various types of processing scenarios, the method proposed in the technical solution of this aspect can determine the optimal inverse solution optimization solution based on multiple objective functions.

[0013] Preferably, in step S1, a machine tool hardware system is constructed, and in an eight-axis machine tool system, a six-axis robot is mounted upside down on an external XY moving axis, and an end clamp is provided to ensure that the end effector and the sixth axis of the robot remain collinear, so as to ensure that the subsequently established machine tool model can use the inverse solution optimization method for the coupled motion of the water jet machine tool.

[0014] Preferably, in step S2, three redundant parameter schemes are adopted for the characteristics of water jet machining, each scheme includes two parameters ρ1 and ρ2, and the three schemes are:

[0015] Solution 1: ρ1 limits the rotation angle θ1 of the first axis of the robot, and ρ2 limits the extension of the robot;

[0016] Solution 2: ρ1 limits the rotation angle θ1 of the robot's first axis, and ρ2 limits the robot's arm span;

[0017] Solution 3: ρ1 limits the movement of the external X axis, and ρ2 limits the movement of the external Y axis;

[0018] Preferably, step S3 comprises:

[0019] Parameter optimization is performed on ρ1 in the three redundant parameter schemes. After obtaining the determined workpiece processing task, the STL model of the workpiece to be processed is first imported, and then the ρ1 optimization algorithm process is performed as follows, where:

[0020] Solution 1 is the optimization process of ρ1 when a rectangular envelope is selected:

[0021] First, the enveloping rectangle of the workpiece is divided into four triangles TriaA, B, C, and D using the diagonals of the rectangle, where the intersection of the diagonals is centreA. The ρ1 corresponding to the points to be processed in the triangles TriaA, B, C, and D is calculated as follows. The calculation formula for ρ1 corresponding to the points to be processed in TriaA is:

[0022]

[0023] Among them, Rp 1x With Rp1y Respectively represent the x and y coordinates of point Rp1, Rp 2x With Rp 2y Respectively represent the x and y coordinates of point Rp2, centreA x With centreA y Respectively represent the x and y coordinates of point centreA; Considering that the optimization method of ρ1 will cause a sudden change of ρ1 when processing the trajectory to be processed across two triangles, the angle mutation is not allowed due to the high stability requirements of water jet processing. When encountering this working condition, the process of selecting Solution 2 is as follows:

[0024] Solution 2 is the optimization process of ρ1 when a circular envelope is selected:

[0025] A circular envelope method is used, where the center of the circle is centreB, and ρ1 is calculated according to the following formula:

[0026] ρ1=atan2(TrackPoint(i) y -centreA y ,TrackPoiht(i) x -centreA x )

[0027] Among them, TrackPoint(i) x With TrackPoint(i) y Respectively represent the x and y coordinates of the i-th processing point in the processing path, centreB x With centreB y Respectively represent the x and y coordinates of point centreB.

[0028] Preferably, step S3 comprises:

[0029] Targeted parameter optimization is performed on ρ2 in the three redundant parameter schemes according to the restriction function and the objective function, where the restriction functions are Cst1 and Cst2:

[0030] Cst1 is the operating angle limit for each axis of the machine tool, and the function expression is:

[0031]

[0032] In the above formula, θ j It represents the angle of the jth joint when the robot arm is processing a certain processing point. and They represent the upper and lower limits of the motion range of the jth joint of the robot arm when processing a certain processing point. x and y represent the current displacement values ​​of the external X-axis and Y-axis of the machine tool system when processing a certain processing point. max With x min Respectively represent the upper and lower limits of the external X-axis motion range, max With y min Respectively represent the upper and lower limits of the motion range of the external Y-axis;

[0033] Cst2 is the limit for the singularity of the robot arm in the bed-adding system, and the function expression is:

[0034] Cst2=W>0

[0035] in is the calculation formula of machine tool operability, w represents the flexibility of machine tool, Represents a set of joint angle values ​​of the robot arm, J(θ * ) means when the robot arm axes are at θ * The Jacobian matrix of the robot arm, J T (θ * ) represents J(θ * ), det(J(θ * )J T (θ * )) represents the matrix J(θ * )J T (θ * )

[0036] The objective function includes Tar1 and Tar2:

[0037] The optimization goal of Tar1 is the overall operability of the machine tool. Assuming that a complete machining path has n machining points, the function is expressed as:

[0038]

[0039] where w i It indicates the maneuverability of the robot arm at the i-th processing point in the machine tool processing path;

[0040] The optimization goal of Tar2 is the overall stability of the machine tool:

[0041]

[0042] in It is a weighted coefficient proposed according to the influence of each axis of the machine tool on the stability. σ1, σ2, σ3, σ4, σ5, and σ6 respectively represent the mean square error of the angle change of the XY axis in the water jet machining system and the six axes of the six-axis robot during the machining process;

[0043] Finally, the improved quadratic sequence algorithm is used to optimize the parameters of ρ2.

[0044] Preferably, before performing parameter optimization, it is necessary to generate a minimum circumscribed circle or a minimum circumscribed rectangle for the workpiece model to be processed.

[0045] Preferably, before performing parameter optimization, it is necessary to analyze the robot's maneuverability space and reachable space, and generate a maneuverability space distribution map, and use this as a basis to give the initial value and optimization range in the optimization process in step S3, so as to achieve efficient iteration of the optimization algorithm, especially to achieve efficient iteration of the ρ2 optimization algorithm.

[0046] Preferably, during the parameter optimization process, it is necessary to actually compare the overall angle change diagram of the machine tool during the simulation of each redundant parameter solution.

[0047] Preferably, in step S4, the inverse solution calculation of the machine tool uses an improved geometric method, and the restrictions of optimized redundant parameters are added during the calculation process, so that the angles of each axis of the machine tool in each processing posture can be calculated in real time.

[0048] Preferably, in step S5, after completing the inverse solution of the machine tool for each redundant parameter scheme, it is necessary to select the optimal scheme through a decision algorithm, and finally implement the inverse solution of the entire machining process of the machine tool, so as to input it into the actual machine tool machining system to complete the physical machining.

[0049] A system for executing the inverse solution optimization method for coupled motion of a water jet machine tool of the present invention comprises a computer device, one or more processors, a memory coupled to the one or more processors, and a program for the inverse solution optimization method for coupled motion of a water jet machine tool stored in the memory, wherein when the program is executed by the one or more processors, the computer device executes the operating procedure of any one of the methods of claims 1-10.

[0050] Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

[0051] 1. In the past, the station planning processing required moving the robot's station after completing the processing task at one station. At this time, it was necessary to ensure that the end effector remained at the previous processing point. If the water jet was at one processing point for a long time, overcutting would occur. The eight-axis coupled motion proposed in the present invention can make the machine tool uninterrupted during the entire processing process and perform smooth processing motion, greatly improving the processing quality of the workpiece;

[0052] 2. Compared with other coupled motion solutions for mobile robots, the coupled motion of mobile robots only needs to ensure stable arrival at limited processing points, while industrial processing machine tools need to ensure that the machine tools stably arrive at the corresponding postures during the entire processing process; since the redundant parameter solution proposed in the present invention is proposed based on the characteristics of water jet processing, it can better realize the processing process;

[0053] 3. When performing parameter optimization, the method proposed in the present invention conducts a targeted analysis of the robot's workspace and flexibility space, and gives the initial value and optimization range of the optimization algorithm based on the analysis results, which greatly improves the calculation efficiency of the method;

[0054] 4. Compare the schemes involved in the comparison according to the operability and stability conditions, obtain the optimal inverse solution under the current working conditions, and finally use the scheme of the present invention to obtain the inverse solution according to the geometric method, which has higher calculation efficiency;

[0055] 5. The method of the present invention is simple, easy to implement, low in cost, and suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0057] Figure 1 This is the overall flow chart of the inverse optimization of the machine tool of the present invention.

[0058] Figure 2 This is a flow chart of the redundant parameter ρ1 optimization algorithm of the present invention.

[0059] Figure 3 It is a flow chart of the solution decision algorithm in the present invention.

[0060] Figure 4 It is the minimum envelope rectangle diagram of the workpiece obtained in step S3 of the present invention.

[0061] Figure 5 It is the minimum envelope circular diagram of the workpiece obtained in step S3 of the present invention. DETAILED DESCRIPTION

[0062] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0063] The above scheme is further described below in conjunction with specific implementation examples. The preferred embodiments of the present invention are described in detail as follows:

[0064] Embodiment 1:

[0065] In this embodiment, see Figure 1 , an inverse solution optimization method for the coupled motion of a water jet machine tool, which is used to realize smooth coupled motion between a robot and an external axis in a redundant degree of freedom machine tool, comprises the following steps:

[0066] S1: Build the machine tool hardware system and establish the machine tool DH model;

[0067] S2: Three redundant parameter schemes are proposed according to the characteristics of water jet machine tools;

[0068] S3: Optimize the redundant parameters ρ1 and ρ2;

[0069] S4: Use geometric method to obtain the inverse solution;

[0070] S5: According to the characteristics of water jet machining, compare the advantages and disadvantages of three schemes after parameter optimization for the current working conditions and make a decision. Select the best set of schemes to calculate the inverse solution and input it into the machine tool for actual machining.

[0071] This embodiment is an inverse solution optimization method for the coupled motion of a water jet machine tool, designed for industrial processing, and proposes a variety of redundant parameter solutions for water jet machine tools. It also takes into account processing stability, flexibility and other characteristics, has high efficiency and a variety of application scenarios.

[0072] Embodiment 2:

[0073] This embodiment is basically the same as the first embodiment, except that:

[0074] In this embodiment, in step S1, a machine tool hardware system is constructed, and in an eight-axis machine tool system, a six-axis robot is mounted upside down on an external XY moving axis, and an end clamp is provided to ensure that the end effector and the sixth axis of the robot remain collinear, so as to ensure that the subsequently established machine tool model can use the inverse solution optimization method for the coupled motion of the water jet machine tool.

[0075] In this embodiment, in step S2, three redundant parameter schemes are used according to the characteristics of water jet machining. Each scheme includes two parameters, ρ1 and ρ2. The three schemes are:

[0076] Solution 1: ρ1 limits the rotation angle θ1 of the first axis of the robot, and ρ2 limits the extension of the robot;

[0077] Solution 2: ρ1 limits the rotation angle θ1 of the robot's first axis, and ρ2 limits the robot's arm span;

[0078] Solution 3: ρ1 limits the movement of the external X axis, and ρ2 limits the movement of the external Y axis;

[0079] In this embodiment, step S3 includes:

[0080] Parameter optimization is performed on ρ1 in the three redundant parameter schemes. After obtaining the determined workpiece processing task, the STL model of the workpiece to be processed is first imported, and then the ρ1 optimization algorithm process is performed as follows, where:

[0081] Solution 1 is the optimization process of ρ1 when a rectangular envelope is selected:

[0082] First, the enveloping rectangle of the workpiece is divided into four triangles TriaA, B, C, and D using the diagonals of the rectangle, where the intersection of the diagonals is centreA. The ρ1 corresponding to the points to be processed in the triangles TriaA, B, C, and D is calculated as follows. The calculation formula for ρ1 corresponding to the points to be processed in TriaA is:

[0083]

[0084] Among them, Figure 4 As shown, Rp 1x With Rp 1y Respectively represent the x and y coordinates of point Rp1, Rp 2x With Rp 2y Respectively represent the x and y coordinates of point Rp2, centreA x With centreA y Respectively expressed as Figure 4 The x and y coordinates of point centreA are shown in the figure. Considering that the optimization method of ρ1 will cause a sudden change in ρ1 when processing the trajectory to be processed across two triangles, and the water jet processing has high requirements for stability, angle mutation is not allowed. When encountering this working condition, Solution 2 is selected as follows:

[0085] Solution 2 is the optimization process of ρ1 when a circular envelope is selected:

[0086] A circular envelope method is used, where the center of the circle is centreB, and ρ1 is calculated according to the following formula:

[0087] ρ1=atan2(TrackPoint(i) y -centreA y , TrackPoint(i) x -centreA x )

[0088] Among them, TrackPoint(i) x With TrackPoint(i)y Respectively represent the x and y coordinates of the i-th processing point in the processing path, centreB x With centreB y Respectively expressed as Figure 5 The x and y coordinates of point centreB are shown.

[0089] In this embodiment, step S3 includes:

[0090] Targeted parameter optimization is performed on ρ2 in the three redundant parameter schemes according to the restriction function and the objective function, where the restriction functions are Cst1 and Cst2:

[0091] Cst1 is the operating angle limit for each axis of the machine tool, and the function expression is:

[0092]

[0093] In the above formula, θ j It represents the angle of the jth joint when the robot arm is processing a certain processing point. and They represent the upper and lower limits of the motion range of the jth joint of the robot arm when processing a certain processing point. x and y represent the current displacement values ​​of the external X-axis and Y-axis of the machine tool system when processing a certain processing point. max With x min Respectively represent the upper and lower limits of the external X-axis motion range, max With y min Respectively represent the upper and lower limits of the motion range of the external Y-axis;

[0094] Cst2 is the limit on the machine tool's singularity, and the function expression is:

[0095] Cst2=w>0

[0096] in is the calculation formula of machine tool operability, w represents the flexibility of machine tool, Represents a set of joint angle values ​​of the robot arm, J(θ * ) means when the robot arm axes are at θ * The Jacobian matrix of the robot arm, J T (θ * ) represents J(θ * ), det(J(θ * )JT(θ * )) represents the matrix J(θ * )J T (θ * )

[0097] The objective function includes Tar1 and Tar2:

[0098] The optimization goal of Tar1 is the overall operability of the machine tool, and the function is expressed as:

[0099]

[0100] where w i It indicates the maneuverability of the robot arm at the i-th processing point in the machine tool processing path;

[0101] The optimization goal of Tar2 is the overall stability of the machine tool:

[0102]

[0103] in It is a weighted coefficient proposed according to the influence of each axis of the machine tool on the stability; among them, σ1, σ2, σ3, σ4, σ5, and σ6 respectively represent the mean square error of the angle change of the XY axis in the water jet machining system and the six axes of the six-axis robot during the machining process;

[0104] Finally, the improved quadratic sequence algorithm is used to optimize the parameters of ρ2.

[0105] In this embodiment, before performing parameter optimization, it is necessary to generate a minimum circumscribed circle or a minimum circumscribed rectangle for the workpiece model to be processed.

[0106] In this embodiment, before performing parameter optimization, it is necessary to analyze the robot's maneuverability space and reachable space, and generate a maneuverability space distribution map, and based on this, give the initial value and optimization range in the optimization process in step S3 to achieve efficient iteration of the optimization algorithm.

[0107] In this embodiment, in step S4, the inverse solution calculation of the machine tool uses an improved geometric method, and the restrictions of optimized redundant parameters are added during the calculation process, so that the angles of each axis of the machine tool in each processing posture can be calculated in real time.

[0108] In this embodiment, in step S5, after completing the inverse solution of the machine tool for each redundant parameter solution, it is necessary to select the optimal solution through a decision algorithm, and finally implement the inverse solution of the entire machining process of the machine tool, so as to input it into the actual machine tool machining system to complete the actual machining.

[0109] The eight-axis coupled motion of this embodiment can make the machine tool uninterrupted in the entire processing process, and perform smooth processing motion, which greatly improves the processing quality of the workpiece; since the redundant parameter scheme proposed in the present invention is proposed based on the characteristics of water jet processing, the processing process can be better realized; when optimizing parameters, the method proposed in the present invention conducts a targeted analysis of the robot's workspace and flexibility space, and gives the initial value and optimization range of the optimization algorithm according to the analysis results, which greatly improves the calculation efficiency of the method; using the scheme of the present invention to perform inverse solution according to the geometric method, the calculation efficiency is higher.

[0110] Embodiment three:

[0111] This embodiment is basically the same as the above embodiment, with the following features:

[0112] In this embodiment, see Figure 3 , an inverse solution optimization method for the coupled motion of a water jet machine tool, which is used to realize smooth coupled motion between a robot and an external axis in a redundant degree of freedom machine tool, comprises the following steps:

[0113] S1: Build the machine tool facilities and computer storage media corresponding to the method, install the six-axis robot upside down on the suspended external XY moving axis, the travel range of the external moving axis is 0-1200mm, the robot uses YASKAWAMOTOMAN-GP8, the robot has a repeat positioning accuracy of ±0.02mm, a maximum load mass of 8KG, a dynamic range of 727mm, and the end gripper uses a homemade gripper that can ensure that the end effector and the sixth axis of the robot remain in line. After the construction is completed, connect the storage medium of the method in the present invention, that is, an industrial computer, and establish a DH model for the built machine tool hardware for subsequent analysis;

[0114] S2: According to the above-mentioned water jet construction characteristics and water jet processing characteristics, three redundant parameter schemes are proposed, corresponding to different processing conditions:

[0115] Solution a. ρ1 limits the rotation angle θ1 of the first axis of the robot, and ρ2 limits the extension of the robot;

[0116] Solution b. ρ1 limits the rotation angle θ1 of the first axis of the robot, and ρ2 limits the arm span of the robot;

[0117] Solution c. ρ1 limits the movement of the external X axis, and ρ2 limits the movement of the external Y axis;

[0118] S3: For the optimization process of parameter ρ1, after obtaining the determined workpiece processing task, first import the STL model of the workpiece to be processed, and then follow the following Figure 2 The ρ1 optimization algorithm flow shown in Figure 1 is as follows:

[0119] Solution 1 is the ρ1 optimization process when a rectangular envelope is selected:

[0120] First, the envelope of the workpiece is as follows Figure 4 As shown, the rectangle is divided into four triangles TriaA, B, C, and D using the diagonals of the rectangle, where the intersection of the diagonals is centreA. The ρ1 corresponding to the points to be processed in the triangles TriaA, B, C, and D is calculated as follows. For example, the calculation formula for the ρ1 corresponding to the points to be processed in TriaA is:

[0121]

[0122] Obviously, using this method to process the machining trajectory that spans two triangles will lead to a sudden change in ρ1. Since water jet machining has high requirements for stability, angle mutations are not allowed. When encountering this working condition, Solution 2 is selected.

[0123] Solution 2 is the optimization process of ρ1 with circular envelope:

[0124] The circular envelope is Figure 5 As shown, the center of the circle is centreB, and ρ1 is calculated according to the following formula

[0125] ρ1=atan2(TrackPoint(i) y -centreA y , TrackPoint(i) x -centreA x )

[0126] The parameter optimization of ρ2 in the three proposed redundant parameter schemes is carried out according to the restriction function and the objective function, where the restriction functions are Cst1 and Cst2:

[0127] Cst1 is the operating angle limit for each axis of the machine tool, and the function expression is:

[0128]

[0129] Cst2 is the limit on the machine tool's singularity, and the function expression is:

[0130] Cst2=w>0

[0131] in The calculation formula for the operability of the machine tool is

[0132] The objective function includes Tar1 and Tar2:

[0133] The optimization goal of Tar1 is the overall flexibility of the machine tool, and the function expression is:

[0134]

[0135] The optimization goal of Tar2 is the overall stability of the machine tool:

[0136]

[0137] in It is a weighted coefficient proposed based on the influence of each axis of the machine tool on stability.

[0138] Finally, based on the above-mentioned restriction functions Cst1, Cst2 and objective functions Tar1, Tar2, the improved quadratic sequence algorithm is used to optimize the parameters of ρ2, where the optimization initial value of the quadratic sequence algorithm is given according to the flexibility distribution of the robot's workspace, and the optimization range limit is given according to the robot's three-dimensional workspace.

[0139] S4: After step S3 is completed, the redundant parameters ρ1 and ρ2 with determined values ​​will be obtained, and then they will be substituted into the geometric method to obtain the eight-axis inverse kinematics solution of the machine tool.

[0140] S5: Steps S1-S4 are completed as follows: Figure 3 As shown in the figure, all the processes before selecting the optimal solution based on the operability and the mean square error of the angle change, step S5 will select the optimal solution to implement the inverse solution of the entire machining process of the machine tool, and finally input it into the actual machine tool machining system to complete the actual machining.

[0141] This embodiment is aimed at the inverse solution optimization method of the coupled motion of the redundant degree of freedom water jet machine tool, builds the machine tool hardware system and establishes the machine tool DH model; proposes three redundant parameter schemes according to the characteristics of the water jet machine tool; optimizes the redundant parameters ρ1 and ρ2; uses the geometric method to obtain the inverse solution; according to the characteristics of water jet processing, compares the advantages and disadvantages of the three schemes after parameter optimization according to the current working conditions and makes a decision, selects the best set of schemes to calculate the inverse solution and inputs it into the machine tool for actual processing. The present invention does not require complex station planning, can avoid the problem of water jet overcutting in sub-station processing, and can realize the smooth coupling motion of the eight axes of the water jet machine tool to ensure high processing quality.

[0142] Embodiment 4:

[0143] This embodiment is basically the same as the above embodiment, with the following features:

[0144] In this embodiment, a system for executing the inverse solution optimization method for the coupled motion of a water jet machine tool described in the above embodiments is characterized in that it includes a computer device, including one or more processors, a memory coupled to the one or more processors, and also includes a program for the inverse solution optimization method for the coupled motion of a water jet machine tool stored in the memory, and when the program is executed by the one or more processors, the computer device executes the operating program of any one of the methods in the above embodiments.

[0145] This embodiment is an inverse optimization system for the coupled motion of a water jet machine tool and is designed for industrial processing. Its running program proposes a variety of redundant parameter schemes for water jet machines and optimizes them, while taking into account processing stability, flexibility and other characteristics. It has high efficiency and a variety of application scenarios.

[0146] The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention and do not deviate from the technical principles and inventive concepts of the present invention, they belong to the protection scope of the present invention.

Claims

1. An inverse solution optimization method for coupled motion of a water jet machine tool, characterized in that: The method is used to realize smooth coupling motion between a robot and an external axis in a redundant degree of freedom machine tool, and includes the following steps: S1: Build the machine tool hardware system and establish the machine tool DH model; S2: Three redundant parameter schemes are proposed according to the characteristics of water jet machine tools; S3: Optimize the redundant parameters ρ1 and ρ2; S4: Use geometric method to obtain the inverse solution; S5: According to the characteristics of water jet machining, the three schemes after parameter optimization are compared for the current working conditions and a decision is made. The best set of schemes is selected to calculate the inverse solution and input it into the machine tool for actual machining; In the step S1, a machine tool hardware system is constructed. In the eight-axis machine tool system, a six-axis robot is mounted upside down on an external XY moving axis, and an end clamp is set to ensure that the end effector and the sixth axis of the robot remain collinear. After the machine tool hardware system is constructed, a storage medium, i.e., an industrial computer, is connected to establish a DH model for the constructed machine tool hardware system for subsequent analysis; ensuring that the subsequently established machine tool model can use the inverse solution optimization method for the coupled motion of the water jet machine tool; In step S2, three redundant parameter schemes are used according to the characteristics of water jet machining. Each scheme includes two parameters, ρ1 and ρ2. The three schemes are: Solution 1: ρ1 limits the rotation angle θ1 of the first axis of the robot, and ρ2 limits the extension of the robot; Solution 2: ρ1 limits the rotation angle θ1 of the robot's first axis, and ρ2 limits the robot's arm span; Solution 3: ρ1 limits the movement of the external X axis, and ρ2 limits the movement of the external Y axis; The step S3 comprises: Parameter optimization is performed on ρ1 in the three redundant parameter schemes. After obtaining the determined workpiece processing task, the STL model of the workpiece to be processed is first imported, and then the ρ1 optimization algorithm process is performed as follows, where: Solution 1 is the optimization process of ρ1 when a rectangular envelope is selected: First, the enveloping rectangle of the workpiece is divided into four triangles TriaA, B, C, and D using the diagonals of the rectangle, where the intersection of the diagonals is centreA. The ρ1 corresponding to the points to be processed in the triangles TriaA, B, C, and D is calculated as follows. The calculation formula for ρ1 corresponding to the points to be processed in TriaA is: Among them, Rp 1x With Rp 1y Respectively represent the x and y coordinates of point Rp1, Rp 2x With Rp 2y Respectively represent the x and y coordinates of point Rp2, centreA x With centreA y Respectively represent the x and y coordinates of point centreA; Considering that the optimization method of ρ1 will cause a sudden change of ρ1 when processing the trajectory to be processed across two triangles, the angle mutation is not allowed due to the high stability requirements of water jet processing. When encountering this working condition, the process of selecting Solution 2 is as follows: Solution 2 is the optimization process of ρ1 when a circular envelope is selected: A circular envelope method is used, where the center of the circle is centreB, and ρ1 is calculated according to the following formula: ρ1=atan2(TrackPoint(i) y -centreA y ,TrackPoint(i) x -centreA x ) Among them, TrackPoint(i) x With TrackPoint(i) y Respectively represent the x and y coordinates of the i-th processing point in the processing path, centreB x With centreB y Respectively represent the x and y coordinates of point centreB; In step S4, the inverse solution of the machine tool is calculated using an improved geometric method, and optimized redundant parameter restrictions are added during the calculation process, so that the angles of each axis of the machine tool in each processing posture can be calculated in real time.

2. The inverse solution optimization method for the coupled motion of a water jet machine tool according to claim 1 is characterized in that: The step S3 comprises: Targeted parameter optimization is performed on ρ2 in the three redundant parameter schemes according to the restriction function and the objective function, where the restriction functions are Cst1 and Cst2: Cst1 is the operating angle limit for each axis of the machine tool, and the function expression is: In the above formula, θ j It represents the angle of the jth joint when the robot arm is processing a certain processing point. and They represent the upper and lower limits of the motion range of the first and second joints of the robot arm when processing a certain processing point. x and y represent the current displacement values ​​of the external X-axis and Y-axis of the machine tool system when processing a certain processing point. max With x min Respectively represent the upper and lower limits of the external X-axis motion range, max With y min Respectively represent the upper and lower limits of the motion range of the external Y-axis; Cst2 is the limit on the machine tool's singularity, and the function expression is: Cst2=w>0 in is the calculation formula of machine tool operability, w represents the flexibility of machine tool, Represents a set of joint angle values ​​of the robot arm, J(θ * ) means when the robot arm axes are at θ * The Jacobian matrix of the robot arm, J T (θ * ) represents J(θ * ), det(J(θ * )J T (θ * )) represents the matrix J(θ * )J T (θ * ) The objective function includes Tar1 and Tar2: The optimization goal of Tar1 is the overall operability of the machine tool, and the function is expressed as: where w i It indicates the maneuverability of the robot arm at the i-th processing point in the machine tool processing path; The optimization goal of Tar2 is the overall stability of the machine tool: in It is a weighted coefficient proposed according to the influence of each axis of the machine tool on the stability. σ1, σ2, σ3, σ4, σ5, and σ6 respectively represent the mean square error of the angle change of the XY axis in the water jet machining system and the six axes of the six-axis robot during the machining process; Finally, the improved quadratic sequence algorithm is used to optimize the parameters of ρ2.

3. The inverse solution optimization method for the coupled motion of a water jet machine tool according to claim 1 or 2, characterized in that: Before performing parameter optimization, it is necessary to generate the minimum circumscribed circle or minimum circumscribed rectangle of the workpiece model to be processed.

4. The inverse solution optimization method for the coupled motion of a water jet machine tool according to claim 2 is characterized in that: Before performing parameter optimization, it is necessary to analyze the robot's maneuverability space and reachable space, and generate a maneuverability space distribution map, based on which the initial value and optimization range in the optimization process in step S3 are given to achieve efficient iteration of the optimization algorithm.

5. The inverse solution optimization method for the coupled motion of a water jet machine tool according to claim 1, characterized in that: In step S5, after completing the inverse solution of the machine tool for each redundant parameter solution, it is necessary to select the optimal solution through a decision algorithm, and finally implement the inverse solution of the entire machining process of the machine tool, so as to input it into the actual machine tool machining system to complete the actual machining.

6. A system for executing the inverse optimization method for coupled motion of a water jet machine tool as claimed in claim 1, characterized in that: The invention comprises a computer device, one or more processors, a memory coupled to the one or more processors, and a program of an inverse solution optimization method for coupled motion of a water jet machine tool stored in the memory, wherein when the program is executed by the one or more processors, the computer device executes an operating procedure of any one of the methods of claims 1 to 5.

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