CN-121973101-A - Robot grinding track planning method considering time-varying contact state

CN121973101ACN 121973101 ACN121973101 ACN 121973101ACN-121973101-A

Abstract

The application discloses a robot grinding track planning method considering a time-varying contact state, which relates to the technical field of robot machining and comprises the steps of determining an initial machining path of a to-be-machined curved surface of an aeroengine, establishing a grinding contact coordinate system by using the to-be-machined curved surface and a grinding tool, determining target chord heights of curve sections between adjacent initial machining points by using the initial machining path, iteratively adjusting the initial machining points based on a comparison result of the target chord heights and a target chord height error threshold value, judging whether the actual overlapping distance between equivalent grinding circles of the adjusted machining points meets the target overlapping distance or not, adjusting the adjusted machining points based on the judgment result, determining a target machining path based on the equivalent grinding circles, and performing grinding operation on curved surface members based on a target machining program generated by the grinding contact coordinate system, each target machining path and the target machining points. The accuracy of the robot grinding is improved without neglecting the time-varying nature of the contact area during the flexible grinding process.

Inventors

ZOU LAI
MU YILIN
LI HENG
WANG WENXI
ZHANG JUNJIE
YAN SHENGBO

Assignees

重庆大学

Dates

Publication Date: 20260505
Application Date: 20260203

Claims (10)

1. The robot grinding track planning method considering the time-varying contact state is characterized by comprising the following steps of: Determining a curved surface to be processed based on an input three-dimensional model corresponding to a curved surface component of an aeroengine, determining an initial processing path of the curved surface to be processed, and establishing a grinding contact coordinate system by utilizing the geometric relationship of a contact point of the curved surface to be processed and a grinding tool, wherein the grinding contact coordinate system comprises a first coordinate system corresponding to the curved surface component, a second coordinate system corresponding to the grinding tool and a third coordinate system corresponding to the contact point; Dispersing the initial processing paths based on a chord height method to obtain initial processing points, determining target chord heights of curve segments between adjacent initial processing points by using a preset interval contraction algorithm, and iteratively adjusting the initial processing points based on a comparison result of the target chord heights and a target chord height error threshold to obtain adjusted processing points; Constructing an elastic extrusion model, and determining an equivalent grinding circle corresponding to each adjusted processing point by combining the normal force of the grinding tool pressed against the curved surface to be processed and the thickness of the elastic layer of the grinding tool, wherein the equivalent grinding circle is a circle for equivalently characterizing the boundary of the contact area between the grinding tool and the curved surface to be processed; Judging whether the actual overlapping distance between the adjacent equivalent grinding circles meets the target overlapping distance or not, and adjusting the adjusted machining point by using a dichotomy based on the judging result to obtain a target machining point; And determining a corresponding current grinding band boundary based on the equivalent grinding circle on the current machining path, determining each target machining path based on the current grinding band boundary and utilizing a preset iterative search algorithm, and generating a target machining program identifiable by a robot based on the grinding contact coordinate system, each target machining path and machining point information of each corresponding target machining point so as to conduct grinding operation on the curved surface member by utilizing the target machining program.
2. The method for planning grinding track of a robot in consideration of time-varying contact state according to claim 1, wherein the determining a curved surface to be machined based on the three-dimensional model corresponding to the curved surface component of the input aero-engine, determining an initial machining path of the curved surface to be machined, and establishing a grinding contact coordinate system by using the geometric relationship between the curved surface to be machined and a contact point of a grinding tool comprises: acquiring a three-dimensional model corresponding to an input curved surface component of the aeroengine, and determining a curved surface to be processed, which needs to be ground, based on the three-dimensional model; Extracting parameter domain boundary information of the curved surface to be processed, and determining an initial processing path of the curved surface to be processed based on the parameter domain boundary information; Determining a direction perpendicular to the curved surface to be processed and the surface of the grinding tool as a common normal vector, determining a moving direction of the grinding tool as a feeding direction, and determining a unit vector perpendicular to the common normal vector and the feeding direction; and establishing a first coordinate system corresponding to the curved surface member, a second coordinate system corresponding to the grinding tool and a third coordinate system corresponding to the contact point by utilizing the geometric relationship of the contact point of the curved surface to be processed and the grinding tool, wherein the main curvature directions of the coordinate systems are consistent.
3. The method for planning a grinding track of a robot in consideration of a time-varying contact state according to claim 1, wherein the dispersing the initial machining path based on a chord height method to obtain each initial machining point comprises: And dispersing the initial processing path based on a chord height method and a preset dispersing rule to obtain each initial processing point, wherein the preset dispersing rule is a dispersing rule determined based on the curved surface bending degree of the initial processing path.
4. The method for planning a grinding track of a robot in consideration of a time-varying contact state according to claim 1, wherein determining a target chord height of a curve segment between adjacent initial machining points by using a preset interval contraction algorithm comprises: Determining the vertical distance from any point on the curve segment between the initial processing points to a target line segment as the actual chord height; Shrinking the parameter interval corresponding to the curve section based on a preset shrinkage coefficient to obtain a shrunk interval, and judging whether the actual chord height corresponding to the shrunk interval meets a preset shrinkage stopping condition, wherein the preset shrinkage stopping condition is that the interval length corresponding to the shrunk interval is not greater than a target interval length threshold, and the difference value between the maximum actual chord height and the minimum actual chord height of the shrunk interval is not greater than a first target difference value threshold; And if the preset shrinkage stopping condition is met, determining the maximum actual chord height of the shrunk section as a target chord height.
5. The method for planning a grinding track of a robot in consideration of a time-varying contact state according to claim 4, wherein iteratively adjusting each of the initial machining points based on a comparison of the target chord height and a target chord height error threshold to obtain adjusted machining points comprises: if the difference value between the target chord height and the target chord height error threshold is larger than a second target difference value threshold, judging whether the target chord height is larger than the target chord height error threshold or not, and adjusting the parameter interval based on the obtained judging result to obtain a target interval; And 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 the initial processing points 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 a second target difference threshold so as to obtain an adjusted processing point corresponding to the target chord height.
6. The method for planning a grinding track of a robot in consideration of a time-varying contact state according to claim 4, wherein the determining whether the target chord height is greater than the target chord height error threshold and adjusting the parameter interval based on the obtained determination result to obtain a target interval comprises: Judging whether the target chord height is larger than the target chord height error threshold; if the target chord height is larger than the target chord height error threshold, contracting a right interval end point of the parameter interval to obtain a target interval; and if the target chord height is smaller than the target chord height error threshold, expanding the right interval end point of the parameter interval to obtain a target interval.
7. The method for planning a grinding track of a robot in consideration of a time-varying contact state according to claim 1, wherein the constructing an elastic extrusion model and determining an equivalent grinding circle corresponding to each adjusted machining point by combining a normal force of the grinding tool to press the curved surface to be machined and an elastic layer thickness of the grinding tool comprises: An elastic extrusion model is constructed, and the contact deformation of the grinding tool at each adjusted processing point is determined by combining the normal force of the grinding tool pressing the curved surface to be processed, the thickness of an elastic layer of the grinding tool, the relative principal curvature and the equivalent elastic modulus, wherein the relative principal curvature is a principal curvature related parameter of the curved surface to be processed and the grinding tool at the adjusted processing point, and the equivalent elastic modulus is an index for measuring the softness of materials of the curved surface to be processed and the grinding tool; And determining a semi-major axis and a semi-minor axis of a contact circle corresponding to the contact point on each adjusted machining point based on the contact deformation, and determining an equivalent grinding circle by using the semi-major axis and the semi-minor axis.
8. The method for planning a grinding track of a robot in consideration of a time-varying contact state according to claim 1, wherein the determining whether the actual overlapping distance between adjacent equivalent grinding circles satisfies a target overlapping distance, adjusting the adjusted machining point by a dichotomy based on a determination result to obtain a target machining point, includes: determining the actual overlapping distance between the adjacent equivalent grinding circles on the adjusted machining point, and judging whether the overlapping distance error between the actual overlapping distance and the target overlapping distance is not more than a target overlapping distance error threshold value; And if the overlapping distance error is larger than the target overlapping distance error threshold, adjusting the position of the adjusted machining point by a dichotomy to obtain a new adjusted machining point, and then jumping to the step of determining the actual overlapping distance between the adjacent equivalent grinding circles on the adjusted machining point until the overlapping distance error is not larger than the target overlapping distance error threshold so as to obtain the target machining point.
9. The method of robotic grinding track planning in consideration of time-varying contact conditions in accordance with any one of claims 1-8, wherein the determining of the corresponding current grinding zone boundary based on the equivalent grinding circle on the current machining path comprises: projecting the equivalent grinding circle corresponding to the target processing point on the current processing path to the parameter domain boundary information of the curved surface to be processed along the unit vector so as to obtain each projection point; and constructing the current grinding belt boundary based on the parameter coordinates of each projection point.
10. The method for planning a grinding track of a robot in consideration of a time-varying contact state according to claim 2, wherein the determining each target machining path based on the current grinding belt boundary and using a preset iterative search algorithm comprises: determining the maximum radius of the equivalent grinding circle on the current machining path as the initial distance between the boundary of the current grinding belt and the next machining path, and determining the next machining path by utilizing the initial distance; determining a predicted grinding belt boundary based on a predicted equivalent grinding circle corresponding to the target machining point on the next machining path, and determining the actual overlapping amount of the current grinding belt boundary and the predicted grinding belt boundary; And correcting the initial distance by using a self-adaptive factor based on the difference value between the actual overlapping amount and the target overlapping amount to obtain a corrected distance, determining a next target machining path by using the corrected distance, determining the next target machining path as a new current machining path, and jumping to the step of projecting the equivalent grinding circle corresponding to the target machining point on the current machining path to the parameter domain boundary information of the curved surface to be machined along the unit vector until the maximum absolute value of the distance correction is not greater than a target tolerance to obtain each target machining path.

Description

Robot grinding track planning method considering time-varying contact state Technical Field The invention relates to the technical field of robot machining, in particular to a robot grinding track planning method considering time-varying contact states. Background In the technical field of robot processing, robot abrasive belt grinding is a key process for improving the surface quality of complex components such as blades, blisks and the like. Such components typically have complex variable curvature geometries, placing severe demands on profile accuracy and surface integrity. In the processing process, the flexible grinding system formed by the abrasive belt and the contact wheel can effectively adapt to the continuous change of the curved surface of the workpiece by virtue of good contact compliance, so that rigid impact is avoided. However, the flexible contact characteristic also causes the contact behavior of the grinding process to show high nonlinearity and time variability, namely, the size and shape of the actual grinding contact area can be subjected to uncontrollable dynamic change under the influence of nonlinear change of the elastic deformation of the contact wheel caused by remarkable change of the curvature of the blade surface when the robot moves along the track. The conventional track planning method (such as traditional equal chord height dispersion and equal parameter path planning) is mostly based on a simplified geometric model or rigid contact assumption, so that the time-varying characteristic of a contact area in the flexible grinding process is often ignored, the profile precision of a blade profile is difficult to ensure and local overgrinding and undergrinding phenomena are easily caused, on one hand, in a step length dispersion link, the conventional method cannot accurately capture the true maximum chord height error of a curvature mutation part, the physical overlapping rate of adjacent grinding circles is ignored, the profile precision is difficult to ensure and the material removal amount is unevenly distributed, on the other hand, in a line distance planning link, the path with fixed parameters cannot adapt to the contact area difference of concave-convex curved surfaces of the blade, overgrinding is caused at a blade basin due to expansion of a contact area, and undergrinding is caused at a blade back due to shrinkage of the contact area. These problems ultimately lead to significant reduction in the consistency of the quality of the processing of the full profile of the blade, difficulty in ensuring the stringent profile accuracy requirements, and severely impaired aerodynamic performance and fatigue life of the blade. From the above, how to improve the accuracy of robot grinding without neglecting the time-varying characteristics of the contact area during flexible grinding is a current problem to be solved. Disclosure of Invention In view of the above, the present invention aims to provide a method, a device, equipment and a medium for planning a grinding track of a robot, which allow for a time-varying contact state, and can improve the accuracy of grinding of the robot without neglecting the time-varying characteristics of a contact area in a flexible grinding process. The specific scheme is as follows: In a first aspect, the present application provides a method for planning a grinding track of a robot in consideration of a time-varying contact state, including: Determining a curved surface to be processed based on an input three-dimensional model corresponding to a curved surface component of an aeroengine, determining an initial processing path of the curved surface to be processed, and establishing a grinding contact coordinate system by utilizing the geometric relationship of a contact point of the curved surface to be processed and a grinding tool, wherein the grinding contact coordinate system comprises a first coordinate system corresponding to the curved surface component, a second coordinate system corresponding to the grinding tool and a third coordinate system corresponding to the contact point; Dispersing the initial processing paths based on a chord height method to obtain initial processing points, determining target chord heights of curve segments between adjacent initial processing points by using a preset interval contraction algorithm, and iteratively adjusting the initial processing points based on a comparison result of the target chord heights and a target chord height error threshold to obtain adjusted processing points; Constructing an elastic extrusion model, and determining an equivalent grinding circle corresponding to each adjusted processing point by combining the normal force of the grinding tool pressed against the curved surface to be processed and the thickness of the elastic layer of the grinding tool, wherein the equivalent grinding circle is a circle for equivalently characterizing the boundary of the contact area between the grind