An eccentric swing type robot irregular disc cutter touch point path planning method

Abstract

The application discloses a kind of eccentric swing type robot special-shaped disc cutter contact path planning method, comprising the following steps: according to the size of grinding area of special-shaped disc grinding mode calculation;According to the equal chord height error and equal sector error of hub end surface calculation cutter contact;According to the special-shaped disc polishing path of cutter contact planning.This application calculates the size of grinding area under constant polishing force according to the polishing operation mode of eccentric swing of special-shaped disc, then calculates the cutter contact of uniform grinding of hub workpiece end surface according to the equal chord height error and equal sector error of hub end surface, finally, according to the cutter contact, a reasonable grinding path is planned on the surface of hub, which is suitable for the eccentric swing polishing operation of polishing disc on the surface of workpiece.This application has important significance for the cutter contact planning of physical uniform grinding of robot special-shaped disc, the realization of physical uniform grinding of workpiece surface and the quality control of workpiece surface after grinding.

Description

Technical Field

[0001] This invention belongs to the field of workpiece processing technology, and more specifically, this invention relates to a method for planning the contact point path of an eccentric swinging robot with an irregularly shaped disc tool. Background Technology

[0002] In critical manufacturing sectors such as aviation, aerospace, shipbuilding, rail transportation, and automobiles, the demand for components with superior surface quality is constantly increasing. Currently, the grinding of complex curved workpieces mainly relies on manual operation, which is limited by the operator's skills, proficiency, and working conditions, making it difficult to ensure the consistency of the workpiece surface. At the same time, the noise and metal dust generated during the grinding process pose a potential long-term threat to worker health.

[0003] Industrial robot technology has demonstrated its effectiveness in building grinding platforms as a solution to the problems of continuous contact part production, especially in grinding tasks with low cutting force requirements, low precision standards, and large, complex-shaped workpieces, showing significant application advantages and development potential. As a key driver of intelligent manufacturing, industrial robots play a vital role in improving the level of production automation. The use of robotic technology for grinding complex curved surfaces foreshadows a promising future and enormous growth potential.

[0004] In the field of robotic grinding, lightweight and flexible grinding tools such as irregularly shaped grinding discs are favored because they facilitate precise position control and attitude adjustment by robots. The flexible contact between the rubber base of these tools and the workpiece surface not only reduces impact during grinding but also improves grinding efficiency while maintaining adaptability to complex curved surfaces. Research on toolpath planning for robots using these grinding tools is an important way to achieve precision grinding manufacturing, improve production automation, and promote industrial technological progress.

[0005] Therefore, this paper proposes a path planning method for the contact points of an eccentric swinging robot with irregularly shaped cutting discs, which is of great significance for improving the production efficiency of key components, realizing the automated production of high-end equipment, and promoting the development of intelligent manufacturing. Summary of the Invention

[0006] This invention provides a method for path planning of contact points of irregularly shaped cutting discs in an eccentric swinging robot, aiming to solve the above-mentioned problems.

[0007] The present invention relates to a method for path planning of contact points of an eccentric swinging robot with irregularly shaped cutting discs. The method steps are as follows:

[0008] Step 1: Calculate the size of the grinding area based on the grinding method of the irregular disc;

[0009] Step 2: Calculate the tool contact point based on the equal chord height error and equal sector error of the hub end face:

[0010] (1) Calculate the curvature of the hub end face;

[0011] (2) Calculate the tool contact distance of a single grinding path based on the equal chord height error;

[0012] (3) Calculate the tool contact distance between adjacent grinding paths based on the equal sector error;

[0013] Step 3: Plan the grinding path for the irregular disc based on the tool contact point:

[0014] (1) Connect the blade contacts of the wheel hub spokes into a directed diagram;

[0015] (2) Find the optimal path using depth-first search based on graph theory;

[0016] Furthermore, based on the eccentric oscillation operation mode of the robot's irregularly shaped disc, the calculation formula for the contact area between the irregularly shaped disc and the workpiece under constant grinding force is as follows:

[0017]

[0018]

[0019] Where w is the width of the contact area between the grinding disc and the workpiece surface under constant contact force when the grinding disc does not vibrate, and l is the length of the contact area under the same conditions. Let w be the equivalent radius of the grinding disc, h be the maximum contact depth of the grinding disc, and θ be the angle between the normal direction of the grinding disc and the normal direction of the workpiece surface. The grinding area is a rectangular area formed by w and l. To achieve physical uniform grinding within this rectangular area, the following tool contact point planning method is used.

[0020] Further, the curvature of the hub end face is calculated. Then, the tool contact spacing of a single grinding path is calculated based on the equal chord height error. Finally, the tool contact spacing between adjacent grinding paths is calculated based on the equal sector error, including:

[0021] (1) The principal curvature at any point on a smooth free surface can be expressed by the normal curvature, and the calculation formula is as follows:

[0022]

[0023] Where, k n Let k1 and k2 represent the principal curvatures, where k1 and k2 are the two directions of maximum and minimum curvature at a point on the surface, respectively. n represents the direction of the normal to the freeform surface, s represents the value of the directed arc segment of the freeform surface, X represents the shape change of the surface in the horizontal direction, and Y represents the shape change of the surface in the vertical direction.

[0024] (2) The tool contact point planning method based on equal chord height error involves calculating the tool contact points in the X direction of the freeform surface and calculating the tool contact point spacing L for a single grinding path based on the equal chord height error. d The calculation method is as follows:

[0025]

[0026] Where ε is the maximum material removal depth achieved by the eccentric oscillation of the grinding disc, and R i The radius of curvature of the workpiece at the tool contact point on the workpiece surface. The tool contact spacing calculated based on the equal chord height error constitutes the tool contact planning for a single grinding path;

[0027] (3) The equal sector error tool contact point planning method calculates the tool contact points in the Y direction of the freeform surface, and calculates the tool contact point spacing W between adjacent grinding paths based on the equal sector error. d The calculation method is as follows:

[0028]

[0029] Among them, h m Let r be the maximum material removal depth of the irregularly shaped disk within the grinding zone, β be the eccentricity amplitude, and β be the elastic deformation parameter. The tool contact spacing calculated based on the equal sector error forms the tool contact planning for adjacent grinding paths.

[0030] Furthermore, the contact points of the wheel hub spokes are connected into a directed graph. Then, a depth-first search based on graph theory is used to find the optimal path, including:

[0031] (1) Calculate the poses of the vertices of the triangular mesh and the poses of the segmented points after cylindrical slicing on the end face model of the wheel hub using STL (Standard Triangle Language). Then, based on the cylindrical slicing method of the triangular mesh on the end face of the wheel hub, calculate the non-uniform slice spacing and the segmented points after slicing using the equal fan-shaped error knife contact point planning method. Then, convert the segmented points into knife contacts and connect them into a directed graph using the equal chord height error knife contact point planning method.

[0032] (2) Based on the depth-first algorithm, perform tool path planning on the generated tool contact points on the hub end face;

[0033] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0034] (1) A method for planning the contact point of an eccentric swinging robot cutting tool is provided, which can realize the planning of grinding tasks and provide an effective solution for the comprehensive application of robots;

[0035] (2) The tool contact point is calculated based on the equal chord height error and equal sector error of the hub end face, which can realize uniform grinding of the hub end face and quality control of the workpiece surface after grinding. Attached Figure Description

[0036] Figure 1 Flowchart of a method for planning the contact point path of an eccentric swinging robot with an irregularly shaped cutting disc, provided as an example of the present invention.

[0037] Figure 2 A schematic diagram of the contact area between the grinding disc and the workpiece surface when the grinding disc is not vibrating, as provided in this embodiment of the invention;

[0038] Figure 3 A schematic diagram of the grinding area of ​​the grinding disc and the workpiece provided for an example of the present invention;

[0039] Figure 4 A schematic diagram of a partial freeform surface of a wheel hub provided as an example of the present invention;

[0040] Figure 5 A schematic diagram for calculating the chord height error of the grinding disc and the tool contact point, provided as an example of the present invention;

[0041] Figure 6 A schematic diagram of adjacent grinding paths provided for an example of the present invention;

[0042] Figure 7 A schematic diagram for calculating the fan-shaped error tool contact points of a grinding disc, etc., provided as an example of the present invention;

[0043] Figure 8 A schematic diagram of the pose of the wheel hub end face segmentation point provided for an example of the present invention;

[0044] Figure 9 A schematic diagram of the wheel hub end face grinding path planning results provided for an example of the present invention. Detailed Implementation

[0045] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0046] Figure 1 This is a flowchart of a method for planning the contact point path of an eccentric swinging robot with an irregularly shaped cutting disc, provided in an embodiment of the present invention. The method includes the following steps:

[0047] Step 1: Calculate the size of the grinding area based on the grinding method of the irregular disc;

[0048] Based on the eccentric oscillation operation mode of the robot's irregularly shaped grinding disc, the formula for calculating the contact area between the irregularly shaped grinding disc and the workpiece under constant grinding force is as follows:

[0049]

[0050]

[0051] Where w is the width of the contact area between the grinding disc and the workpiece surface under constant contact force when the grinding disc does not vibrate, and l is the length of the contact area under the same conditions. Let w be the equivalent radius of the grinding disc, h be the maximum contact depth of the grinding disc, and θ be the angle between the normal direction of the grinding disc and the normal direction of the workpiece surface. The grinding area is a rectangular area formed by w and l. To achieve physical uniform grinding within this rectangular area, the following tool contact point planning method is used.

[0052] Figure 2 This diagram illustrates the contact between the grinding disc and the workpiece surface. The rubber base of the grinding disc flexibly contacts the workpiece surface, allowing it to better adapt to changes in the workpiece's surface shape and curvature during grinding, reducing uneven material removal caused by surface irregularities. The elastic rubber base also provides cushioning for the robot, effectively reducing impact and friction between the robot and the workpiece. The grinding disc, with an equivalent radius of m, initially contacts the workpiece at point O. An orthogonal coordinate system O-XYZ is established on the workpiece surface according to the following rules: the robot's end-effector motion direction f is the X-axis, aligned with the surface normal direction n, and perpendicular to the workpiece surface at the initial contact point O is the Z-axis. The Y-axis is given by the unit vector n×f. The contact area, represented by a gray region, is defined as the area where the grinding disc undergoes local deformation near the initial contact point O after pressing into the workpiece at an angle θ during polishing. The initial contact point O represents the maximum contact depth h within this contact area.

[0053] Figure 3 This is a schematic diagram of the grinding area. The contact area has a length of l and a width of w. The leftmost point on the contact area is (x... m y m The topmost point is (x) M y M The grinding zone is in the region x = x m x = 0 and y = 2y M Within a rectangular boundary area.

[0054] Step 2: Calculate the tool contact point based on the equal chord height error and equal sector error of the hub end face:

[0055] (1) Calculate the curvature of the hub end face;

[0056] Figure 4 This is a schematic diagram of a local freeform surface of a wheel hub. For workpieces like wheel hubs with freeform surfaces, the shape characteristics of the local freeform surface are represented parametrically. Parameter X represents the shape change of the surface in the horizontal direction, and parameter Y represents the shape change of the surface in the vertical direction. and Let be the principal curvature radius of the workpiece surface, e1 and e2 be the principal curvature directions of the workpiece surface near O, and the angle between the robot end motion direction f and the principal curvature direction e1 is φ.

[0057] The principal curvature at any point on a smooth free-form surface can be expressed as the normal curvature, and the calculation formula is as follows:

[0058]

[0059] Where, k n Let k1 and k2 represent the principal curvatures, where k1 and k2 are the two directions of maximum and minimum curvature at a point on the surface, respectively. n represents the direction of the normal to the freeform surface, s represents the value of the directed arc segment of the freeform surface, X represents the shape change of the surface in the horizontal direction, and Y represents the shape change of the surface in the vertical direction.

[0060] (2) Calculate the tool contact distance of a single grinding path based on the equal chord height error;

[0061] Figure 5 This is a schematic diagram for calculating the contact point of the tool to maintain the chord height error of the grinding disc. The grinding disc starts from P(u) i ) to P(u i+1 The distance between the tool contacts in the horizontal direction on the workpiece surface is l. d When the distance between the knife contact points is sufficiently small, it is approximately assumed that P(u) i ) and P(u i+1 The radius of curvature is equal at point R, i.e. i =R i+1 P(u) i ) and P(u i+1 The midpoint is M(u) i ε represents the maximum material removal depth. When the maximum material removal depth equals the curve P(u... i ) and P(u i+1 When the corresponding chord length is given, the horizontal tool contact distance on the workpiece surface is calculated as L according to the Pythagorean theorem. d for:

[0062]

[0063] (3) Calculate the tool contact distance between adjacent grinding paths based on the equal sector error.

[0064] Figure 6 This is a schematic diagram of adjacent grinding paths, S i and S i+1 This represents two adjacent grinding paths. By rationally planning the spacing between adjacent paths, the sector error of the overlapping area is ensured to be equal, thereby achieving consistency in material removal from the workpiece surface.

[0065] Figure 7 This is a schematic diagram for calculating the contact points of the grinding disc and other fan-shaped error tools. The distance between the contact points of two adjacent grinding paths in the vertical direction on the workpiece surface is W. d When the distance between the tool contacts is sufficiently small, R is approximately considered to be... i =R i+1 The unground area between adjacent paths is shown in gray in the figure. Depending on the workpiece surface shape, different cases need to be discussed. The tool contact distance in the vertical direction of the workpiece surface is calculated as W using the Pythagorean theorem. d for:

[0066]

[0067] Among them, h m Let r be the maximum material removal depth of the irregularly shaped disk within the grinding zone, β be the eccentricity amplitude, and β be the elastic deformation parameter. The tool contact spacing calculated based on the equal sector error forms the tool contact planning for adjacent grinding paths.

[0068] Step 3: Plan the grinding path for the irregularly shaped disc based on the tool contact point:

[0069] (1) Connect the blade contacts of the wheel hub spokes into a directed diagram;

[0070] The poses of the vertices of the triangular mesh and the poses of the segmented points after cylindrical slicing are calculated on the end face model of the wheel hub using STL (Standard Triangle Language). Next, based on the cylindrical slicing method of the triangular mesh on the end face of the wheel hub, the non-uniform slice spacing and the segmented points after slicing are calculated using the equal sector error knife-contact planning method. Then, the segmented points are transformed into knife-contact points and connected into a directed graph using the equal chord height error knife-contact planning method.

[0071] Figure 8 The diagram shows the pose of the segmentation point on the end face of the wheel hub. A directed graph is formed by defining the movement sequence and direction of the irregularly shaped disk on the pose of the segmentation point on the end face of the wheel hub.

[0072] (2) Find the optimal path using depth-first search based on graph theory.

[0073] Based on the depth-first algorithm, toolpath planning is performed on the planned tool contact points on the end face of the wheel hub.

[0074] Figure 9 The image shows the grinding path planning result on the wheel hub end face. The main principle of planning the robot's tool path for irregularly shaped discs on the wheel hub end face based on the tool contact point is as follows:

[0075] (1) Take the directed graph generated by the spoke slice on the hub end face as a unit, and mark the node at any end of the directed graph as visited;

[0076] (2) Visit the node at the other end of the directed graph and set it as the current node;

[0077] (3) On the hub end face, select an unvisited adjacent node from the current node, mark it as visited, and take the other end node of its directed graph as the current node;

[0078] (4) Repeat steps (2) and (3) until the current node has no unvisited neighboring nodes;

[0079] (5) If the current node has no unvisited adjacent nodes, backtrack to the previous node and continue steps (2) and (3) until all directed graph nodes on the hub end face have been traversed.

[0080] The optimal path is found by depth-first search based on graph theory, forming a circular tool path on the hub end face. The tool contact points are then connected in a reasonable way to form a continuous tool path for the robot's irregularly shaped disk.

[0081] The method for planning the contact point of an eccentric swinging robot with irregularly shaped cutting discs provided by this invention has the following beneficial technical effects:

[0082] (1) A method for planning the contact point of an eccentric swinging robot cutting tool is provided, which can realize the planning of grinding tasks and provide an effective solution for the comprehensive application of robots;

[0083] (2) The tool contact point is calculated based on the equal chord height error and equal sector error of the hub end face, which can realize uniform grinding of the hub end face and quality control of the workpiece surface after grinding.

[0084] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0085] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for path planning of contact points of an eccentric swinging robot with irregularly shaped cutting discs, characterized in that, The method specifically includes the following steps: Step 1: Calculate the size of the grinding area based on the grinding method of the irregular disc; Step 2: Calculate the tool contact point based on the equal chord height error and equal sector error of the hub end face: (1) Calculate the curvature of the hub end face; The principal curvature at any point on a smooth free-form surface can be expressed as the normal curvature, and the calculation formula is as follows: Where, k n Let k1 and k2 represent the principal curvatures, where k1 and k2 are the principal curvatures in the two directions where the curvature is greatest and least at a point on the surface, respectively. n represents the direction of the normal to the freeform surface, s represents the value of the directed arc segment of the freeform surface, X represents the shape change of the surface in the horizontal direction, and Y represents the shape change of the surface in the vertical direction. (2) Calculate the tool contact distance of a single grinding path based on the equal chord height error; The constant chord height error tool contact point planning method calculates the tool contact points in the X direction of the freeform surface, and calculates the tool contact point spacing L for a single grinding path based on the constant chord height error. d The calculation method is as follows: Where ε is the maximum material removal depth achieved by the eccentric oscillation of the grinding disc, and R i The workpiece surface at the tool contact point is the workpiece radius of curvature; the tool contact spacing calculated based on the equal chord height error constitutes the tool contact planning on a single grinding path; (3) Calculate the tool contact distance between adjacent grinding paths based on the equal sector error; The equal sector error tool contact planning method calculates tool contact points in the Y direction of the freeform surface, and calculates the tool contact point spacing W between adjacent grinding paths based on the equal sector error. d The calculation method is as follows: Among them, h m The maximum material removal depth of the irregular disk in the grinding area is denoted by r, which is the eccentricity amplitude, and β is the elastic deformation parameter. The tool contact spacing calculated based on the equal sector error constitutes the tool contact planning on adjacent grinding paths. Step 3: Plan the grinding path for the irregularly shaped disc based on the tool contact point: (1) Calculate the pose of the vertices of the triangular mesh and the pose of the segmented points after the cylindrical slice on the STL end face model of the hub. Then, on the end face of the hub, calculate the non-uniform slice spacing and the segmented points after slicing based on the triangular mesh cylindrical slice method and the equal fan-shaped error knife contact point planning method. Then, convert the segmented points into knife contacts and connect them into a directed graph using the equal chord height error knife contact point planning method. (2) Based on graph theory, depth-first algorithm is used to plan tool paths for the generated tool contact points on the hub end face.

2. The method for planning the contact point path of an eccentric swinging robot with an irregularly shaped cutting disc according to claim 1, characterized in that, Based on the eccentric oscillation operation mode of the robot's irregular-shaped grinding disc, the formula for calculating the contact area between the irregular-shaped grinding disc and the workpiece under constant grinding force is as follows: Where w is the width of the contact area between the grinding disc and the workpiece surface under constant contact force when the grinding disc does not vibrate, and l is the length of the contact area under the same conditions. Let w be the equivalent radius of the grinding disc, h be the maximum contact depth of the grinding disc, θ be the angle between the normal direction of the grinding disc and the normal direction of the workpiece surface, and the grinding area be the rectangular area formed by w and l.

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