Optimization method for in-situ measurement postures of robots in restricted space

SONG Huipeng; WANG Yingpeng; SUN Yuwen

doi:10.7688/j.issn.1000-1646.2025.02.01

Abstract：[Objective]In modern manufacturing,as the demand for machining accuracy and efficiency continues to rise,in-situ measurement technology,serving as a real-time and precise measurement method,is gradually becoming an indispensable part of modern machining processes.Industrial robots are widely applied in in-situ measurement and processing of complex parts due to their large work space,high motion flexibility,and ease of programming.However,limited by complicate measurement space constraints and the nonlinear transmission and expression of measurement motion in the joint space of the robots,they exhibit posturenon-smoothness at their ends and even suffer collisions during measurement along a predefined path.To tackle this issue,a posture optimization method based on the redundant motion parameter of the robot measurement system was proposed.[Methods]Firstly,the forward and inverse kinematics model of the robot was established,and the motion transmission relationship between the measurement motion and the joint space of the robot was calculated with this model.Considering that there existed a redundant motion parameter in the robot measurement system that rotates around the axis of the measuring tool,a set of redundant measurement postures satisfying the joint angle limitconstraint and posture singularity constraint at each path point were constructed.Subsequently,to avoid collision between the robot and obstacles,an oriented bounding box was employed to model themeasurement of large-size complex curved components,and then the Gilbert-Johnson-Keerthi(GJK)method was implemented for rapid collision detection between the robot and the obstacles to screen a set of robot in-situ measurement postures that meeting collision-free constraints.Finally,the Dijkstra's shortest path technique was applied to determine the robot measurement posture sequence with the minimum joint angle variation,enhancing the stability of robots during in-site measurement in restricted space.[Results]The proposed method was verified by experiments.The joint angle data of the robot during the measurement process were collected.The results indicate that the method significantly enhances the joint motion smoothness of the robot,reduces the cumulative changes in joint angles,and effectively lowers the amplitude and standard deviation of joint angle fluctuations.The robot is enabled to perform smooth and collision-free measurement of parts in restricted space.[Conclusion]The proposed optimization method for in-situ measurement postures of robots based on the redundant motion parameter can effectively avoid global interference between the robot and obstacles and significantly enhance the smoothness of robot postures during the measurement process.