Robot grinding track planning method involving time-varying contact state

Abstract

The invention discloses a robot grinding track planning method involving a time-varying contact state, and relates to the technical field of robot machining, and the robot grinding track planning method comprises the steps that an initial machining path of a to-be-machined curved surface of an aero-engine is determined, and the to-be-machined curved surface and a grinding tool are utilized to establish a grinding contact coordinate system; determining a target chord height of a curve segment between adjacent initial processing points by using the initial processing path, and performing iterative adjustment on the initial processing points based on a comparison result of the target chord height and a target chord height error threshold; whether the actual overlapping distance between the equivalent grinding circles of the adjusted machining points meets the target overlapping distance or not is judged, and the adjusted machining points are adjusted based on the judgment result; and target machining paths are determined based on the equivalent grinding circle, and grinding operation on the curved surface component is carried out based on a target machining program generated by the grinding contact coordinate system, the target machining paths and the target machining points. And under the condition that the time-varying characteristic of the contact area in the flexible grinding process is not ignored, the grinding precision of the robot is improved.

Description

Technical Field

[0001] This invention relates to the field of robotic machining technology, and in particular to a robotic grinding trajectory planning method that takes into account time-varying contact states. Background Technology

[0002] In the field of robotic machining technology, robotic belt grinding is a key process for improving the surface quality of complex components such as blades and integral bladed disks. These components typically possess complex variable curvature geometry, placing extremely stringent requirements on profile accuracy and surface integrity. During machining, the flexible grinding system composed of the abrasive belt and contact wheel, with its excellent contact compliance, can effectively adapt to the continuous changes in the workpiece surface curvature, avoiding rigid impacts. However, this "flexible contact" characteristic also makes the contact behavior during the grinding process highly nonlinear and time-varying: as the robot moves along the trajectory, the nonlinear changes in the elastic deformation of the contact wheel induced by significant changes in the blade surface curvature cause uncontrollable dynamic changes in the size and shape of the actual grinding contact area.

[0003] Existing trajectory planning methods (such as traditional constant chord height discretization and isoparametric path planning) are mostly based on simplified geometric models or rigid contact assumptions, often neglecting the time-varying characteristics of the contact area during flexible grinding. This directly leads to difficulties in ensuring the accuracy of the blade profile and easily causes local over-grinding and under-grinding phenomena. On the one hand, in the step size discretization stage, traditional methods cannot accurately capture the true maximum chord height error at curvature abrupt changes and ignore the physical overlap rate of adjacent grinding circles, resulting in difficulty in ensuring profile accuracy and uneven material removal distribution. On the other hand, in the row spacing planning stage, fixed-parameter paths cannot adapt to the differences in contact area between the concave and convex surfaces of the blade, resulting in over-grinding at the blade base due to contact area expansion and under-grinding at the blade back due to contact area contraction. These problems ultimately lead to a significant reduction in the consistency of machining quality across the entire blade profile, making it difficult to guarantee the stringent profile accuracy requirements and severely weakening the blade's aerodynamic performance and fatigue life.

[0004] As can be seen from the above, how to improve the accuracy of robotic grinding without ignoring the time-varying characteristics of the contact area during flexible grinding is an urgent problem to be solved. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a robot grinding trajectory planning method, apparatus, device, and medium that takes into account time-varying contact states, which can improve the accuracy of robot grinding without ignoring the time-varying characteristics of the contact area during flexible grinding. The specific solution is as follows: Firstly, this application provides a robot grinding trajectory planning method that considers time-varying contact states, including: Based on the three-dimensional model corresponding to the curved component of the input aero-engine, the surface to be processed is determined, and the initial processing path of the surface to be processed is determined. The geometric relationship between the surface to be processed and the contact point of the grinding tool is used to establish a grinding contact coordinate system. The grinding contact coordinate system includes a first coordinate system corresponding to the curved component, a second coordinate system corresponding to the grinding tool, and a third coordinate system corresponding to the contact point. The initial processing path is discretized based on the chord height method to obtain each initial processing point. The target chord height of the curve segment between adjacent initial processing points is determined using a preset interval shrinkage algorithm. Based on the comparison result between the target chord height and the target chord height error threshold, each initial processing point is iteratively adjusted to obtain the adjusted processing point. An elastic extrusion model is constructed, and the equivalent grinding circle corresponding to each of the adjusted machining points is determined by combining the normal force of the grinding tool pressing against the surface to be machined and the elastic layer thickness of the grinding tool; the equivalent grinding circle is a circle used to equivalently characterize the boundary of the contact area between the grinding tool and the surface to be machined. Determine whether the actual overlap distance between adjacent equivalent grinding circles meets the target overlap distance. Based on the determination result, adjust the adjusted machining point using the bisection method to obtain the target machining point. Based on the equivalent grinding circle on the current machining path, the corresponding current grinding zone boundary is determined. Based on the current grinding zone boundary and using a preset iterative search algorithm, each target machining path is determined. Based on the grinding contact coordinate system, each target machining path and the machining point information of each target machining point, a target machining program that can be recognized by the robot is generated, so as to perform grinding operations on the curved surface component using the target machining program.

[0006] Optionally, the three-dimensional model corresponding to the curved component of the input aero-engine is used to determine the surface to be machined, and the initial machining path of the surface to be machined is determined. A grinding contact coordinate system is established using the geometric relationship between the contact point between the surface to be machined and the grinding tool, including: Obtain the three-dimensional model corresponding to the curved surface component of the input aero-engine, and determine the surface to be ground based on the three-dimensional model; Extract the parameter domain boundary information of the surface to be processed, and determine the initial processing path of the surface to be processed based on the parameter domain boundary information; The direction perpendicular to the surface to be processed and the surface of the grinding tool is determined as the common normal vector, and the movement direction of the grinding tool is determined as the feed direction. A unit vector perpendicular to the common normal vector and the feed direction is determined. A first coordinate system corresponding to the surface component, a second coordinate system corresponding to the grinding tool, and a third coordinate system corresponding to the contact point are established using the geometric relationship between the contact point of the surface to be processed and the grinding tool; the principal curvature directions of each coordinate system are consistent.

[0007] Optionally, the discretization of the initial processing path based on the chord height method to obtain each initial processing point includes: The initial processing path is discretized based on the chord height method and a preset discretization rule to obtain each initial processing point; the preset discretization rule is a discretization rule determined based on the curvature of the surface of the initial processing path.

[0008] Optionally, determining the target chord height of the curve segment between adjacent initial processing points using a preset interval contraction algorithm includes: The actual chord height is determined by the vertical distance from any point on the curve segment between each of the initial processing points to the target line segment; the target line segment is the straight line segment between each of the initial processing points. Based on a preset shrinkage coefficient, the parameter interval corresponding to the curve segment is shrunk to obtain a shrunk interval, and it is determined whether the actual chord height corresponding to the shrunk interval meets a preset shrinkage stop condition; the preset shrinkage stop condition is that the interval length corresponding to the shrunk interval is not greater than a target interval length threshold, and the difference between the maximum actual chord height and the minimum actual chord height of the shrunk interval is not greater than a first target difference threshold. If the preset contraction stop condition is met, the maximum actual chord height of the contracted interval is determined as the target chord height.

[0009] Optionally, the iterative adjustment of each initial processing point based on the comparison result between the target chord height and the target chord height error threshold to obtain the adjusted processing point includes: If the difference between the target chord height and the target chord height error threshold is greater than the second target difference threshold, then it is determined whether the target chord height is greater than the target chord height error threshold, and the parameter range is adjusted based on the determination result to obtain the target range; Based on the target interval, a new initial processing point is determined, and then the process jumps to the step of determining the vertical distance from any point on the curve segment between each initial processing point to the target line segment as the actual chord height, until the difference between the target chord height and the target chord height error threshold is not greater than the second target difference threshold, so as to obtain the adjusted processing point corresponding to the target chord height.

[0010] Optionally, determining whether the target chord height is greater than the target chord height error threshold, and adjusting the parameter range based on the obtained determination result to obtain the target range, includes: Determine whether the target chord height is greater than the target chord height error threshold; If the target chord height is greater than the target chord height error threshold, then the right endpoint of the parameter interval is shrunk to obtain the target interval; If the target chord height is less than the target chord height error threshold, then the right endpoint of the parameter interval is expanded to obtain the target interval.

[0011] Optionally, the step of constructing an elastic extrusion model and determining the equivalent grinding circle corresponding to each adjusted machining point by combining the normal force of the grinding tool pressing against the surface to be machined and the elastic layer thickness of the grinding tool includes: An elastic extrusion model is constructed, and the contact deformation of the grinding tool at each adjusted machining point is determined by combining the normal force of the grinding tool pressing against the surface to be processed, the elastic layer thickness of the grinding tool, the relative principal curvature, and the equivalent elastic modulus. The relative principal curvature is a parameter related to the principal curvature of the surface to be processed and the grinding tool at the adjusted machining point. The equivalent elastic modulus is an index for measuring the material hardness of the surface to be processed and the grinding tool. Based on the contact deformation, determine the semi-major axis and semi-minor axis of the contact circle corresponding to the contact point on each of the adjusted machining points, and use the semi-major axis and the semi-minor axis to determine the equivalent grinding circle.

[0012] Optionally, determining whether the actual overlap distance between adjacent equivalent grinding circles meets the target overlap distance, and adjusting the adjusted machining point based on the determination result and using a bisection method to obtain the target machining point, includes: The actual overlap distance between adjacent equivalent grinding circles at the adjusted machining point is determined, and it is judged whether the overlap distance error between the actual overlap distance and the target overlap distance is not greater than the target overlap distance error threshold; the target overlap distance is the overlap distance determined by the average value of each actual overlap distance at the adjusted machining point. If the overlap distance error is greater than the target overlap distance error threshold, the position of the adjusted machining point is adjusted using the bisection method to obtain a new adjusted machining point. Then, the process jumps to the step of determining the actual overlap distance between adjacent equivalent grinding circles on the adjusted machining point until the overlap distance error is not greater than the target overlap distance error threshold to obtain the target machining point.

[0013] Optionally, determining the corresponding current grinding zone boundary based on the equivalent grinding circle on the current machining path includes: The equivalent grinding circle corresponding to the target machining point on the current machining path is projected along the unit vector onto the parameter domain boundary information of the surface to be machined to obtain each projection point; The current grinding zone boundary is constructed based on the parameter coordinates of each of the projection points.

[0014] Optionally, determining each target machining path based on the current grinding zone boundary and using a preset iterative search algorithm includes: The maximum radius of the equivalent grinding circle on the current machining path is determined as the initial distance between the current grinding zone boundary and the next machining path, so as to determine the next machining path using the initial distance; Based on the estimated equivalent grinding circle corresponding to the target processing point on the next processing path, the estimated grinding zone boundary is determined, and the actual overlap between the current grinding zone boundary and the estimated grinding zone boundary is determined. Based on the difference between the actual overlap and the target overlap, the initial spacing is corrected using an adaptive factor to obtain the corrected spacing. The next target machining path is determined using the corrected spacing, and the next target machining path is determined as the new current machining path. Then, the process jumps to the step of projecting the equivalent grinding circle corresponding to the target machining point on the current machining path along the unit vector onto the parameter domain boundary information of the surface to be machined, until the maximum absolute value of the spacing correction is not greater than the target tolerance, so as to obtain each target machining path.

[0015] This application determines the surface to be processed based on the three-dimensional model corresponding to the curved component of the input aero-engine, and determines the initial processing path of the surface to be processed. A grinding contact coordinate system is established using the geometric relationship between the surface to be processed and the contact point of the grinding tool. The grinding contact coordinate system includes a first coordinate system corresponding to the curved component, a second coordinate system corresponding to the grinding tool, and a third coordinate system corresponding to the contact point. The initial processing path is discretized based on the chord height method to obtain each initial processing point. A preset interval shrinkage algorithm is used to determine the target chord height of the curve segment between adjacent initial processing points. Based on the comparison result between the target chord height and the target chord height error threshold, each initial processing point is iteratively adjusted to obtain the adjusted processing point. An elastic extrusion model is constructed, and combined with the normal of the grinding tool pressing against the surface to be processed... The force and the elastic layer thickness of the grinding tool determine the equivalent grinding circle corresponding to each of the adjusted machining points; the equivalent grinding circle is a circle used to equivalently characterize the boundary of the contact area between the grinding tool and the surface to be machined; it is determined whether the actual overlap distance between adjacent equivalent grinding circles meets the target overlap distance, and the adjusted machining points are adjusted based on the judgment result and using a bisection method to obtain the target machining point; the corresponding current grinding zone boundary is determined based on the equivalent grinding circle on the current machining path, and each target machining path is determined based on the current grinding zone boundary and using a preset iterative search algorithm; a target machining program that can be recognized by the robot is generated based on the grinding contact coordinate system, each target machining path and the machining point information of each corresponding target machining point, so as to perform grinding operations on the curved component using the target machining program.

[0016] As can be seen from the above, this application determines the initial machining path by extracting the parameter domain boundary information of the 3D model, establishes a coordinate system including curved components, grinding tools, and contact points, uses the chord height method to achieve adaptive discretization of the curvature of the initial machining points, and combines a preset interval shrinkage algorithm to accurately capture the true maximum chord height of the curve segment between adjacent machining points. The adjusted machining points are obtained by iteratively adjusting the position of the machining points, thus solving the defect of the traditional equal chord height method that takes the chord height of the midpoint of the curve as the maximum chord height. Based on the elastic extrusion model constructed by Hertz theory, the equivalent grinding circle corresponding to each adjusted machining point is obtained by combining the normal force and the thickness of the elastic layer. The equivalent grinding circle can accurately represent the size of the contact area under different curvature positions. The actual overlap distance between adjacent equivalent grinding circles is determined. Based on the target overlap distance, the adjusted machining points are adjusted by the bisection method to keep the overlap rate of the grinding circles constant, so as to obtain the target machining point. The grinding zone boundary is determined based on the equivalent grinding circle, and a preset iterative search algorithm is used to determine each target machining path. Then, combined with the reference information of the grinding contact coordinate system, a machining program that can be executed by the robot is generated. In this way, by using the target machining program to perform grinding operations on curved surface components, the concave and convex characteristics of the curved surface can be adapted, completely eliminating local over-grinding and under-grinding phenomena. This allows the grinding trajectory corresponding to the grinding operation to accurately match the curvature changes of the curved surface component, achieving adaptive adjustment of concave and convex areas without manual intervention, effectively improving the processing yield and reducing process debugging costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This application discloses a flowchart of a robot grinding trajectory planning method that considers time-varying contact states. Figure 2 A schematic diagram of the contact coordinate system between the surface to be machined and the grinding tool provided in this application; Figure 3 This application provides a schematic diagram of an initial processing path discreteness. Figure 4 This application provides a schematic diagram of the maximum actual chord height; wherein, Figure 4 Figure (a) shows a schematic diagram of the maximum actual chord height under an ideal condition. Figure 4 (b) is a schematic diagram of the maximum actual chord height under a real-world condition; Figure 5 A schematic diagram of an interval contraction algorithm provided in this application; Figure 6 A schematic diagram of parameter range adjustment provided in this application; wherein, Figure 6 Image (a) is a schematic diagram showing the adjustment of the left side of a parameter range. Figure 6 (b) is a schematic diagram of adjusting the right side of a parameter range; Figure 7 This application provides a schematic diagram of an initial processing point adjustment; Figure 8 This application provides a schematic diagram for solving an equivalent grinding circle. Figure 9 This application provides a schematic diagram of the adjustment of the processing point after adjustment; wherein, Figure 9 Image (a) is a schematic diagram of a contact projection. Figure 9 Image (b) is a schematic diagram of an overlap distance calculation. Figure 9 Image (c) is a schematic diagram of an overlap distance adjustment; Figure 10 A schematic diagram of the grinding band boundary provided in this application; Figure 11 This is a schematic diagram of a processing path correction provided in this application. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Currently, most existing trajectory planning methods are based on simplified geometric models or rigid contact assumptions, often neglecting the time-varying characteristics of the contact area during flexible grinding. This directly leads to difficulties in ensuring the accuracy of the blade profile and easily causes local over-grinding and under-grinding, resulting in a significant reduction in the consistency of the machining quality of the entire blade profile. This makes it difficult to guarantee the stringent profile accuracy requirements and severely weakens the aerodynamic performance and fatigue life of the blade. Therefore, this application provides a robotic grinding trajectory planning method that considers time-varying contact states. By using the target machining program to perform grinding operations on curved components, it can adapt to the concave and convex characteristics of the surface, completely eliminating local over-grinding and under-grinding. This allows the grinding trajectory corresponding to the grinding operation to accurately match the curvature changes of the curved component, achieving adaptive adjustment of concave and convex areas without manual intervention, effectively improving the machining yield and reducing process debugging costs.

[0021] See Figure 1 As shown, this embodiment of the invention discloses a robot grinding trajectory planning method that considers time-varying contact states, including: Step S11: Determine the surface to be processed based on the three-dimensional model corresponding to the curved component of the input aero-engine, and determine the initial processing path of the surface to be processed. Establish a grinding contact coordinate system using the geometric relationship between the surface to be processed and the contact point of the grinding tool. The grinding contact coordinate system includes a first coordinate system corresponding to the curved component, a second coordinate system corresponding to the grinding tool, and a third coordinate system corresponding to the contact point.

[0022] In this embodiment, the surface to be ground is determined based on the three-dimensional model corresponding to the curved surface component of the input aero-engine. Figure 2 This embodiment provides a schematic diagram of the contact coordinate system between the surface to be machined and the grinding tool, wherein... This represents the common normal vector between the surface to be machined and the grinding tool at the contact point O, i.e., the vector perpendicular to the surface to be machined. This indicates the feed direction of the contact wheel (i.e., the grinding tool), that is, the direction in which the grinding tool will move. Perpendicular to vector and The unit vector, by the right-hand rule Confirmed. The first coordinate system corresponding to the curved surface component is... The first coordinate system and The axes represent the principal curvature directions of the curved surface component, and similarly, the second coordinate system corresponding to the grinding tool is obtained. The third coordinate system corresponding to the contact point ; This represents the angle between the first coordinate system and the third coordinate system. This represents the angle between the second coordinate system and the third coordinate system.

[0023] Specifically, the process involves determining the surface to be processed based on the 3D model corresponding to the curved component of the input aero-engine, determining the initial processing path of the surface to be processed, and establishing a grinding contact coordinate system using the geometric relationship between the surface to be processed and the contact point of the grinding tool. This includes: acquiring the 3D model corresponding to the curved component of the input aero-engine, and determining the surface to be ground based on the 3D model; extracting the parameter domain boundary information of the surface to be processed, and determining the initial processing path of the surface to be processed based on the parameter domain boundary information; determining the direction perpendicular to the surface to be processed and the surface of the grinding tool as a common normal vector, and determining the feed direction based on the movement direction of the grinding tool, and determining a unit vector perpendicular to the common normal vector and the feed direction; establishing a first coordinate system corresponding to the curved component, a second coordinate system corresponding to the grinding tool, and a third coordinate system corresponding to the contact point using the geometric relationship between the surface to be processed and the contact point of the grinding tool; the principal curvature directions of each coordinate system are consistent.

[0024] Step S12: Discretize the initial processing path based on the chord height method to obtain each initial processing point. Use a preset interval shrinkage algorithm to determine the target chord height of the curve segment between adjacent initial processing points. Based on the comparison result between the target chord height and the target chord height error threshold, iteratively adjust each initial processing point to obtain the adjusted processing point.

[0025] In this embodiment, the initial processing path of the surface to be processed is curved and cannot be ground in one go. Therefore, the initial processing path needs to be discretized to obtain each initial processing point. The greater the curvature of the initial processing path, the more initial processing points there are. That is, the curvature of the initial processing path is directly proportional to the number of initial processing points. Figure 3 This embodiment provides a discrete schematic diagram of the initial machining path. The feed direction represents the movement direction of the grinding tool along the curved surface component. The points in the diagram are the initial machining points. In conventional methods, the vertical distance from the midpoint of the curve segment between adjacent initial machining points to the target line segment is determined as the maximum actual chord height, i.e., at the initial machining point... , , ,Will and As the actual chord height.

[0026] Furthermore, Figure 4 This is a schematic diagram of the maximum actual chord height provided in this embodiment. Figure 4 Figure (a) shows a schematic diagram of the maximum actual chord height under an ideal condition. Figure 4 (b) is a schematic diagram of the maximum actual chord height under a real-world condition; Figure 4 In the middle (a), it means that under ideal conditions, the curve segment... arrive Midpoint Or a straight segment arrive midpoint The corresponding chord height is taken as the maximum actual chord height; however, this assumes that the curvature of each point on the curve segment is equal or does not change much. In reality, the curvature of the curve segment changes, so the maximum actual chord height under ideal conditions is inaccurate. Figure 4 In diagram (b), it is shown that under actual conditions, the curvature of each point on the curve segment changes, with the midpoint... Using the corresponding chord height as the maximum actual chord height is clearly incorrect. Therefore, the curve segment should be based on the actual condition. arrive Determine the maximum actual chord height and the corresponding highest point First, define two vectors. , The corresponding formula is as follows: ; in, For curve segments arrive Any point within; a straight line segment arrive Any point within; , For two adjacent initial processing points, the above two vectors are used to determine... The actual chord height corresponding to the point The corresponding formula is as follows: ; in, for endpoints of straight line segments and The included angle formed.

[0027] Understandable, Figure 5 This is a schematic diagram of an interval shrinkage algorithm provided in this embodiment, in the initial interval. arrive Select two test points. and Among them, test points distance Near, test site distance Recently, the actual chord heights corresponding to the two test points, i.e., the first chord height, were determined using the above method. Second string height If the height of the first chord is less than the height of the second chord, it means that the maximum actual chord height is not at the test point. To the left of, therefore narrowing the range to arrive Similarly, if the first chord height is greater than the second chord height, then the range of the maximum actual chord height is narrowed down to... arrive Then, the narrowed interval is determined as the new initial interval, and the step of selecting test points is repeated until the interval length corresponding to the narrowed interval is not greater than the target interval length threshold, and the difference in actual chord heights within the narrowed interval is not greater than the first target difference threshold. Then, the maximum actual chord height within the narrowed interval is determined as the target chord height. It is worth mentioning that the first target difference threshold and the target interval length threshold can be adjusted according to the actual situation.

[0028] Specifically, the discretization of the initial processing path based on the chord height method to obtain each initial processing point, and the determination of the target chord height of the curve segment between adjacent initial processing points using a preset interval shrinkage algorithm, includes: discretizing the initial processing path based on the chord height method and a preset discretization rule to obtain each initial processing point; the preset discretization rule is a discretization rule determined based on the curvature of the surface of the initial processing path; determining the actual chord height as the vertical distance from any point on the curve segment between each initial processing point to the target line segment; the target line segment is the straight line segment between each initial processing point; shrinking the parameter interval corresponding to the curve segment based on a preset shrinkage coefficient to obtain a shrunken interval, and determining whether the actual chord height corresponding to the shrunken interval meets a preset shrinkage stopping condition; the preset shrinkage stopping condition is that the interval length corresponding to the shrunken interval is not greater than a target interval length threshold, and the difference between the maximum and minimum actual chord heights of the shrunken interval is not greater than a first target difference threshold; if the preset shrinkage stopping condition is met, the maximum actual chord height of the shrunken interval is determined as the target chord height.

[0029] In this embodiment, after obtaining the target chord height, the magnitude of the target chord height and the target chord height error threshold is determined, and then the initial processing point is adjusted using a parameter domain search algorithm. The corresponding formula is as follows: ; in, The range between two adjacent initial processing points arrive Target chord height ; The target chord height error threshold is defined as follows. Figure 6 This is a schematic diagram of parameter range adjustment provided in this embodiment. Figure 6 Image (a) is a schematic diagram showing the adjustment of the left side of a parameter range. Figure 6 (b) is a schematic diagram of adjusting the right side of a parameter range; in the first case, if the target chord height is greater than the target chord height error threshold, it indicates the initial processing point. Leave Too far, need to go Move it slightly in the direction, adjusting the range to: the end of the interval. To the start of the interval The direction is adjusted to obtain a new interval endpoint, and the maximum value corresponding to the adjustable interval is... The maximum value is Therefore, the target chord height corresponding to this interval becomes smaller; in the second case, if the target chord height is less than the target chord height error threshold, it indicates that the distance between the two initial processing points in the current interval is too close, and the target chord height can be reduced. Move it a little further away, and adjust the range to: the end of the interval. Adjust the interval to the right of its endpoint to obtain a new endpoint. The maximum value corresponding to the adjustable interval is... The maximum value is Therefore, the target chord height corresponding to this interval increases.

[0030] Understandable, Figure 7 This embodiment provides a schematic diagram of initial processing point adjustment. Regardless of the situation described above, the current adjustment range is first determined (i.e., arrive midpoint of ) The corresponding formula is: ; in, This is the minimum value within the current adjustment range; The maximum value within the current adjustment range is used; the midpoint is selected as a candidate point to obtain the new target chord height. Then, the new target chord height is compared with the target chord height error threshold. If the new target chord height is greater than the target chord height error threshold, then it indicates that... It's still too far; change the maximum value of the interval to the midpoint. If the new target chord height is less than the target chord height error threshold, then... If the distance is too close, it needs to be adjusted to a greater distance. The minimum value of the interval is changed to the midpoint, and then the target chord height corresponding to the new interval is determined. The process then proceeds to the step of comparing the target chord height with the target chord height error threshold. This process is repeated until the difference between the target chord height and the target chord height error threshold is no greater than a second target difference threshold. This yields the adjusted processing point corresponding to the target chord height, ensuring the physical uniformity of the distribution of the adjusted processing points. The second target difference threshold can be adjusted according to the actual situation.

[0031] Specifically, the iterative adjustment of each initial processing point based on the comparison result of the target chord height and the target chord height error threshold to obtain the adjusted processing point includes: if the difference between the target chord height and the target chord height error threshold is greater than a second target difference threshold, then determining whether the target chord height is greater than the target chord height error threshold; if the target chord height is greater than the target chord height error threshold, then shrinking the right endpoint of the parameter interval to obtain the target interval; if the target chord height is less than the target chord height error threshold, then expanding the right endpoint of the parameter interval to obtain the target interval; determining a new initial processing point based on the target interval, and then jumping to the step of determining the vertical distance from any point on the curve segment between each initial processing point to the target line segment as the actual chord height, until the difference between the target chord height and the target chord height error threshold is not greater than the second target difference threshold, so as to obtain the adjusted processing point corresponding to the target chord height.

[0032] Step S13: Construct an elastic extrusion model, and determine the equivalent grinding circle corresponding to each of the adjusted processing points by combining the normal force of the grinding tool pressing against the surface to be processed and the elastic layer thickness of the grinding tool; the equivalent grinding circle is a circle used to equivalently characterize the boundary of the contact area between the grinding tool and the surface to be processed.

[0033] In this embodiment, when the surface to be processed contacts the grinding tool, the contact area is an irregular ellipse or curved surface. An ellipse with a fixed radius is used to replace this irregular area, i.e., an equivalent grinding circle. First, an elastic extrusion model is constructed based on Hertz theory to determine the contact deformation, semi-major axis and semi-minor axis of the contact ellipse, and contact pressure distribution value when the surface to be processed contacts the grinding tool. The corresponding formulas are as follows: ; ; in, The amount of contact deformation; The normal force applied perpendicularly by the grinding tool to the surface to be processed; The thickness of the elastic layer on the surface of the grinding tool; and The curvature superposition value of the surface to be processed and the grinding tool, respectively, corresponding to two orthogonal curvature directions, is the relative principal curvature; It is the equivalent elastic modulus, which is the combined value of the overall hardness of the surface to be processed and the grinding tool; To contact the semi-major axis of the ellipse; To contact the semi-minor axis of the ellipse; Let be the contact pressure distribution value corresponding to any point (x, y) within the contact area. Substituting the obtained contact deformation, semi-major axis, and semi-minor axis of the contact ellipse into... In the formula, if a contact pressure distribution value that conforms to physical laws is obtained, for example, in the middle region... The maximum value is reached at the edge area, and the value gradually decreases at the edge area. This indicates that the contact deformation, the semi-major axis and the semi-minor axis of the contact ellipse conform to physical laws.

[0034] Understandable, Figure 8 This is a schematic diagram of an equivalent grinding circle solution provided in this embodiment. This represents the common normal vector between the surface to be machined and the grinding tool at the contact point O, i.e., the vector perpendicular to the surface to be machined. This indicates the feed direction of the contact wheel (i.e., the grinding tool), that is, the direction in which the grinding tool will move. Perpendicular to vector and , unit vector; For the surface to be processed, , For surface parameters; To contact the semi-major axis of the ellipse; To contact the semi-minor axis of the ellipse; The length of a certain segment of the surface curve on the grinding trajectory; and The coordinate system axes are for the feed direction. The radius of the equivalent grinding circle; Let be the angle between the first coordinate system corresponding to the curved surface component and the second coordinate system corresponding to the grinding tool. Therefore, after obtaining the semi-major axis and semi-minor axis of the contact ellipse, the radius of the equivalent grinding circle is calculated using the following formula: ; in, The radius of the equivalent grinding circle; To contact the semi-major axis of the ellipse; To contact the semi-minor axis of the ellipse; The angle between the first coordinate system corresponding to the curved surface component and the second coordinate system corresponding to the grinding tool is defined. The equivalent grinding circle is determined based on the radius of the equivalent grinding circle.

[0035] Specifically, the step of constructing an elastic extrusion model and determining the equivalent grinding circle corresponding to each adjusted machining point by combining the normal force of the grinding tool pressing against the surface to be machined and the elastic layer thickness of the grinding tool includes: constructing an elastic extrusion model and determining the contact deformation of the grinding tool at each adjusted machining point by combining the normal force of the grinding tool pressing against the surface to be machined, the elastic layer thickness of the grinding tool, the relative principal curvature, and the equivalent elastic modulus; the relative principal curvature is a parameter related to the principal curvature of the surface to be machined and the grinding tool at the adjusted machining point; the equivalent elastic modulus is an index for measuring the material hardness of the surface to be machined and the grinding tool; determining the semi-major axis and semi-minor axis of the contact circle corresponding to the contact point at each adjusted machining point based on the contact deformation, and determining the equivalent grinding circle using the semi-major axis and semi-minor axis.

[0036] Step S14: Determine whether the actual overlap distance between adjacent equivalent grinding circles meets the target overlap distance. Based on the determination result, adjust the adjusted machining point using the bisection method to obtain the target machining point.

[0037] In this embodiment, after obtaining the equivalent grinding circle, it is necessary to consider whether the grinding area overlaps evenly. By adjusting the adjusted processing point, the overlap distance of adjacent equivalent grinding circles is made consistent, avoiding excessive (over-grinding) or insufficient (under-grinding) local overlap, and finally achieving uniform material removal. Figure 9 This is a schematic diagram of the adjustment of the processing point after adjustment provided in this embodiment. Figure 9 Image (a) is a schematic diagram of a contact projection. Figure 9 Image (b) is a schematic diagram of an overlap distance calculation. Figure 9 (c) is a schematic diagram of an overlap distance adjustment; the next adjusted processing point... Projected onto the current adjusted processing point On the tangent plane, to obtain the projection point Corresponding Cartesian coordinates The corresponding formula is as follows: ; in, The Cartesian coordinates of the next adjusted processing point; This is the normal vector corresponding to the currently adjusted processing point; The Cartesian coordinates of the current adjusted machining point; the actual overlap distance of the equivalent grinding circles corresponding to two adjacent adjusted machining points. It can be represented as: ; in, This is the equivalent grinding circle corresponding to the currently adjusted machining point; The equivalent grinding circle corresponding to the next adjusted machining point; The current adjusted processing point and projection point The Euclidean distance between them.

[0038] It is understood that the average value corresponding to each actual overlap distance at the adjusted processing point is determined as the target overlap distance, and the corresponding formula is as follows: ; in, The target overlap distance; The actual overlap distance; Let be the total number of processing points after adjustment. Then, a binary search method is used to adjust the positions of the adjusted processing points. The convergence condition for determining whether the positions of the adjusted processing points are in place is as follows: ; in, The target overlap distance; The actual overlap distance; The target overlap distance error threshold can be adjusted according to the actual situation.

[0039] Specifically, determining whether the actual overlap distance between adjacent equivalent grinding circles meets the target overlap distance, and adjusting the adjusted machining point based on the determination result using a bisection method to obtain the target machining point, includes: determining the actual overlap distance between adjacent equivalent grinding circles at the adjusted machining point; determining whether the overlap distance error between the actual overlap distance and the target overlap distance is not greater than the target overlap distance error threshold; the target overlap distance is the overlap distance determined by the average value of each actual overlap distance at the adjusted machining point; if the overlap distance error is greater than the target overlap distance error threshold, the position of the adjusted machining point is adjusted using a bisection method to obtain a new adjusted machining point, and then the process jumps to the step of determining the actual overlap distance between adjacent equivalent grinding circles at the adjusted machining point until the overlap distance error is not greater than the target overlap distance error threshold to obtain the target machining point.

[0040] Step S15: Determine the corresponding current grinding zone boundary based on the equivalent grinding circle on the current machining path; determine each target machining path based on the current grinding zone boundary and using a preset iterative search algorithm; generate a target machining program that can be recognized by the robot based on the grinding contact coordinate system, each target machining path and the machining point information of each target machining point, so as to perform grinding operations on the curved surface component using the target machining program.

[0041] In this embodiment, Figure 10 This embodiment provides a schematic diagram of the grinding zone boundary, which determines the current machining path for the current machining path. Corresponding current grinding zone boundary ;in, Located on the left side of the feed direction, it is the edge line of the current grinding belt extending to the left of the feed direction; Located to the right of the feed direction, it is the edge line extending to the right of the current grinding band; the boundary of the current grinding band is formed by continuously connecting the projection points of the boundary points of a series of equivalent grinding circles generated along the path onto the curved surface. The equivalent grinding circles are then mapped along the unit vector. Parameter domain boundary information projected onto the surface to be processed The corresponding formula is as follows: ; in, The parameter domain boundary information of the surface to be processed; This indicates the feed direction, that is, the direction in which the grinding tool will move. The unit vector; The equivalent grinding circle corresponding to the target machining point on the current machining path; For parameters The change in the parameter; by solving the above formula, the parameter increment can be obtained. The corresponding formula is as follows: ; in, The parameter domain boundary information of the surface to be processed; This indicates the feed direction, that is, the direction in which the grinding tool will move. The unit vector; This is the equivalent grinding circle corresponding to the target machining point on the current machining path.

[0042] It is understandable that, after obtaining the parameter increment, it can be determined that... Figure 10 Coordinates of midpoint G in the parameter domain The corresponding formula is as follows: ; in, The coordinates of the contact point o on the current machining path; The parameter increment is used to determine the current grinding zone boundary based on the parameter increment corresponding to the equivalent grinding circle in the current machining path.

[0043] In this embodiment, Figure 11 This embodiment provides a schematic diagram of a processing path correction, which modifies the current processing path. The maximum radius of the equivalent grinding circle of each of the target machining points mentioned above is determined as the right boundary of the current grinding zone of the current machining path. and the next processing path initial spacing Using calculations of the current grinding zone boundary The method involves similarly calculating the left boundary of the current grinding zone on the next machining path using the elastic extrusion model. , The right boundary of the current grinding zone, i.e., the estimated grinding zone boundary; the formula corresponding to the correction amount of the initial spacing is as follows: ; in, This is the correction amount for the initial spacing; The target ideal spacing; The initial spacing; The length of the equivalent grinding circle overlap between adjacent paths is set based on preset process requirements.

[0044] Understandably, an adaptive factor is introduced to calculate convergence stability and speed. and The new estimated spacing between them, that is, the corrected spacing obtained by correcting the initial spacing, is given by the following formula: ; in, The next processing path for the target determined based on the corrected spacing; This is the correction amount for the initial spacing; The initial spacing; This is an adaptive factor. The correction amount is adjusted using the adaptive factor until the maximum absolute value of the correction amount for the initial spacing does not exceed the target tolerance, thus obtaining the target next processing path. The above steps are then repeated to obtain each target processing path.

[0045] Specifically, determining the corresponding current grinding zone boundary based on the equivalent grinding circle on the current machining path, and determining each target machining path based on the current grinding zone boundary and using a preset iterative search algorithm, includes: projecting the equivalent grinding circle corresponding to the target machining point on the current machining path along the unit vector onto the parameter domain boundary information of the surface to be machined to obtain each projection point, and constructing the current grinding zone boundary based on the parameter coordinates of each projection point; determining the maximum radius of the equivalent grinding circle on the current machining path as the initial distance between the current grinding zone boundary and the next machining path, and using the initial distance to determine the next machining path; and determining the target machining path based on the target machining point on the next machining path. The estimated equivalent grinding circle corresponding to the machining point determines the estimated grinding zone boundary, and the actual overlap between the current grinding zone boundary and the estimated grinding zone boundary is determined. Based on the difference between the actual overlap and the target overlap, the initial spacing is corrected using an adaptive factor to obtain the corrected spacing. The next target machining path is determined using the corrected spacing, and the next target machining path is determined as the new current machining path. Then, the process jumps to the step of projecting the equivalent grinding circle corresponding to the target machining point on the current machining path along the unit vector onto the parameter domain boundary information of the surface to be machined, until the maximum absolute value of the spacing correction is not greater than the target tolerance, so as to obtain each target machining path.

[0046] Furthermore, after obtaining the target machining path, a base coordinate system corresponding to the robot is established, and the transformation matrix chain between the base coordinate system and the second coordinate system corresponding to the grinding tool is determined. Then, the kinematics is understood, the joint angles of the robot are determined, the position of the grinding tool is installed, the inverse kinematics solution is solved, the grinding contact coordinate system is used as the grinding direction standard, and the grinding tool installed on the end flange of the robot is used to generate a target machining program that can be executed by the robot based on the spatial three-dimensional coordinates and attitude tilt angle of each target machining point, so as to perform the grinding operation on the curved component using the target machining program.

[0047] As can be seen from the above, this application determines the initial machining path by extracting the parameter domain boundary information of the 3D model, establishes a coordinate system including curved components, grinding tools, and contact points, uses the chord height method to achieve adaptive discretization of the curvature of the initial machining points, and combines a preset interval shrinkage algorithm to accurately capture the true maximum chord height of the curve segment between adjacent machining points. The adjusted machining points are obtained by iteratively adjusting the position of the machining points, thus solving the defect of the traditional equal chord height method that takes the chord height of the midpoint of the curve as the maximum chord height. Based on the elastic extrusion model constructed by Hertz theory, the equivalent grinding circle corresponding to each adjusted machining point is obtained by combining the normal force and the thickness of the elastic layer. The equivalent grinding circle can accurately represent the size of the contact area under different curvature positions. The actual overlap distance between adjacent equivalent grinding circles is determined. Based on the target overlap distance, the adjusted machining points are adjusted by the bisection method to keep the overlap rate of the grinding circles constant, so as to obtain the target machining point. The grinding zone boundary is determined based on the equivalent grinding circle, and a preset iterative search algorithm is used to determine each target machining path. Then, combined with the reference information of the grinding contact coordinate system, a machining program that can be executed by the robot is generated. In this way, by using the target machining program to perform grinding operations on curved surface components, the concave and convex characteristics of the curved surface can be adapted, completely eliminating local over-grinding and under-grinding phenomena. This allows the grinding trajectory corresponding to the grinding operation to accurately match the curvature changes of the curved surface component, achieving adaptive adjustment of concave and convex areas without manual intervention, effectively improving the processing yield and reducing process debugging costs.

Claims

1. A robot grinding trajectory planning method considering time-varying contact states, characterized in that, include: Based on the three-dimensional model corresponding to the curved component of the input aero-engine, the surface to be processed is determined, and the initial processing path of the surface to be processed is determined. The geometric relationship between the surface to be processed and the contact point of the grinding tool is used to establish a grinding contact coordinate system. The grinding contact coordinate system includes a first coordinate system corresponding to the curved component, a second coordinate system corresponding to the grinding tool, and a third coordinate system corresponding to the contact point. The initial processing path is discretized based on the chord height method to obtain each initial processing point. The target chord height of the curve segment between adjacent initial processing points is determined using a preset interval shrinkage algorithm. Based on the comparison result between the target chord height and the target chord height error threshold, each initial processing point is iteratively adjusted to obtain the adjusted processing point. An elastic extrusion model is constructed, and the equivalent grinding circle corresponding to each of the adjusted machining points is determined by combining the normal force of the grinding tool pressing against the surface to be machined and the elastic layer thickness of the grinding tool; the equivalent grinding circle is a circle used to equivalently characterize the boundary of the contact area between the grinding tool and the surface to be machined. Determine whether the actual overlap distance between adjacent equivalent grinding circles meets the target overlap distance. Based on the determination result, adjust the adjusted machining point using the bisection method to obtain the target machining point. Based on the equivalent grinding circle on the current machining path, the corresponding current grinding zone boundary is determined. Based on the current grinding zone boundary and using a preset iterative search algorithm, each target machining path is determined. Based on the grinding contact coordinate system, each target machining path and the machining point information of each target machining point, a target machining program that can be recognized by the robot is generated, so as to perform grinding operations on the curved surface component using the target machining program.

2. The robot grinding trajectory planning method considering time-varying contact states according to claim 1, characterized in that, The three-dimensional model corresponding to the curved surface component of the aero-engine, based on the input, determines the surface to be machined and the initial machining path of the surface to be machined. A grinding contact coordinate system is established using the geometric relationship between the contact point between the surface to be machined and the grinding tool, including: Obtain the three-dimensional model corresponding to the curved surface component of the input aero-engine, and determine the surface to be ground based on the three-dimensional model; Extract the parameter domain boundary information of the surface to be processed, and determine the initial processing path of the surface to be processed based on the parameter domain boundary information; The direction perpendicular to the surface to be processed and the surface of the grinding tool is determined as the common normal vector, and the movement direction of the grinding tool is determined as the feed direction. A unit vector perpendicular to the common normal vector and the feed direction is determined. A first coordinate system corresponding to the surface component, a second coordinate system corresponding to the grinding tool, and a third coordinate system corresponding to the contact point are established using the geometric relationship between the contact point of the surface to be processed and the grinding tool; the principal curvature directions of each coordinate system are consistent.

3. The robot grinding trajectory planning method considering time-varying contact states according to claim 1, characterized in that, The discretization of the initial processing path based on the chord height method to obtain each initial processing point includes: The initial processing path is discretized based on the chord height method and a preset discretization rule to obtain each initial processing point; the preset discretization rule is a discretization rule determined based on the curvature of the surface of the initial processing path.

4. The robot grinding trajectory planning method considering time-varying contact states according to claim 1, characterized in that, The step of determining the target chord height of the curve segment between adjacent initial processing points using a preset interval contraction algorithm includes: The actual chord height is determined by the vertical distance from any point on the curve segment between each of the initial processing points to the target line segment; the target line segment is the straight line segment between each of the initial processing points. Based on a preset shrinkage coefficient, the parameter interval corresponding to the curve segment is shrunk to obtain a shrunk interval, and it is determined whether the actual chord height corresponding to the shrunk interval meets a preset shrinkage stop condition; the preset shrinkage stop condition is that the interval length corresponding to the shrunk interval is not greater than a target interval length threshold, and the difference between the maximum actual chord height and the minimum actual chord height of the shrunk interval is not greater than a first target difference threshold. If the preset contraction stop condition is met, the maximum actual chord height of the contracted interval is determined as the target chord height.

5. The robot grinding trajectory planning method considering time-varying contact states according to claim 4, characterized in that, The process of iteratively adjusting each initial processing point based on the comparison result between the target chord height and the target chord height error threshold to obtain the adjusted processing point includes: If the difference between the target chord height and the target chord height error threshold is greater than the second target difference threshold, then it is determined whether the target chord height is greater than the target chord height error threshold, and the parameter range is adjusted based on the determination result to obtain the target range; Based on the target interval, a new initial processing point is determined, and then the process jumps to the step of determining the vertical distance from any point on the curve segment between each initial processing point to the target line segment as the actual chord height, until the difference between the target chord height and the target chord height error threshold is not greater than the second target difference threshold, so as to obtain the adjusted processing point corresponding to the target chord height.

6. The robot grinding trajectory planning method considering time-varying contact states according to claim 4, characterized in that, The step of determining whether the target chord height is greater than the target chord height error threshold, and adjusting the parameter range based on the obtained determination result to obtain the target range, includes: Determine whether the target chord height is greater than the target chord height error threshold; If the target chord height is greater than the target chord height error threshold, then the right endpoint of the parameter interval is shrunk to obtain the target interval; If the target chord height is less than the target chord height error threshold, then the right endpoint of the parameter interval is expanded to obtain the target interval.

7. The robot grinding trajectory planning method considering time-varying contact states according to claim 1, characterized in that, The construction of the elastic extrusion model, and the determination of the equivalent grinding circle corresponding to each adjusted machining point by combining the normal force of the grinding tool pressing against the surface to be machined and the elastic layer thickness of the grinding tool, includes: An elastic extrusion model is constructed, and the contact deformation of the grinding tool at each adjusted machining point is determined by combining the normal force of the grinding tool pressing against the surface to be processed, the elastic layer thickness of the grinding tool, the relative principal curvature, and the equivalent elastic modulus. The relative principal curvature is a parameter related to the principal curvature of the surface to be processed and the grinding tool at the adjusted machining point. The equivalent elastic modulus is an index for measuring the material hardness of the surface to be processed and the grinding tool. Based on the contact deformation, determine the semi-major axis and semi-minor axis of the contact circle corresponding to the contact point on each of the adjusted machining points, and use the semi-major axis and the semi-minor axis to determine the equivalent grinding circle.

8. The robot grinding trajectory planning method considering time-varying contact states according to claim 1, characterized in that, The step of determining whether the actual overlap distance between adjacent equivalent grinding circles meets the target overlap distance, and adjusting the adjusted machining point based on the determination result using a bisection method to obtain the target machining point, includes: The actual overlap distance between adjacent equivalent grinding circles at the adjusted machining point is determined, and it is judged whether the overlap distance error between the actual overlap distance and the target overlap distance is not greater than the target overlap distance error threshold; the target overlap distance is the overlap distance determined by the average value of each actual overlap distance at the adjusted machining point. If the overlap distance error is greater than the target overlap distance error threshold, the position of the adjusted machining point is adjusted using the bisection method to obtain a new adjusted machining point. Then, the process jumps to the step of determining the actual overlap distance between adjacent equivalent grinding circles on the adjusted machining point until the overlap distance error is not greater than the target overlap distance error threshold to obtain the target machining point.

9. The robot grinding trajectory planning method considering time-varying contact states according to any one of claims 1 to 8, characterized in that, The step of determining the corresponding current grinding zone boundary based on the equivalent grinding circle on the current machining path includes: The equivalent grinding circle corresponding to the target machining point on the current machining path is projected along the unit vector onto the parameter domain boundary information of the surface to be machined to obtain each projection point; The current grinding zone boundary is constructed based on the parameter coordinates of each of the projection points.

10. The robot grinding trajectory planning method considering time-varying contact states according to claim 2, characterized in that, The process of determining each target machining path based on the current grinding zone boundary and using a preset iterative search algorithm includes: The maximum radius of the equivalent grinding circle on the current machining path is determined as the initial distance between the current grinding zone boundary and the next machining path, so as to determine the next machining path using the initial distance; Based on the estimated equivalent grinding circle corresponding to the target processing point on the next processing path, the estimated grinding zone boundary is determined, and the actual overlap between the current grinding zone boundary and the estimated grinding zone boundary is determined. Based on the difference between the actual overlap and the target overlap, the initial spacing is corrected using an adaptive factor to obtain the corrected spacing. The next target machining path is determined using the corrected spacing, and the next target machining path is determined as the new current machining path. Then, the process jumps to the step of projecting the equivalent grinding circle corresponding to the target machining point on the current machining path along the unit vector onto the parameter domain boundary information of the surface to be machined, until the maximum absolute value of the spacing correction is not greater than the target tolerance, so as to obtain each target machining path.

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