Research On Accuracy Maintenance Method For Industrial Robot In Manufacturing Field

Industrial robot,as a highly flexible multi-joint motion platform,has been widely used in the process of the automobile manufacture such as welding,handling and detection.However,industrial robot is also an open-loop motion system,whose kinematic accuracy is easily affected by its own factors and environmental factors.For example,at the manufacturing site,the continuous high-speed movement of the industrial robot will cause the robot heating up,so that the kinematic model parameters will drift slowly.In addition,both of the change of the ending tool and the collision between the tool and the workpiece during manufacturing will result in position and orientation error of tool control frame,affecting the processing quality of the robot.Only solving the problem of industrial robot's long-term repeatability can broaden its application field and make it playing an increasingly important role in the transition process from the traditional manufacturing to the advanced intelligent manufacturing.This paper studies two typical precision maintenance problems of the robot temperature drift and the ending tool position error,and puts forward the solutions that can be applied to the manufacturing site respectively.In the process of robot working,these two accuracy compensation methods are performed alternately,which can achieve the purposes of real-time online accuracy maintenance for industrial robot.In this paper,the study reads as follows:1.Based on basic theories of robot kinematics model and spatial coordinate system transformations,the establishment process of robot kinematics model and the ending tool coordinate system is analyzed.The effects of kinematics parameters model and TCF coordinate system on accuracy maintenance for industrial robot are analyzed and summarized.2.After analyzing the reason for the temperature change of the robot and varying pattern of the kinematics parameters affected by the temperature,a complete set of compensation parameters selection process is proposed,which can filter out parameters that are obviously affected by the temperature.A vision measurement system suitable for the thermal error compensation is designed and calibrated.The consuming time of this compensation process can perfectly meet the requirements of the production cycle.3.In this paper,methods of quick automatic calibration for TCP are researched.Then a cross-cutting laser measurement method is proposed and a algorithm of establishing a tool control frame is derived.The trajectory of industrial robot is designed and used for rapid calibration of tool control frame.Finally,the parameters error analysis for the system is carried out and a strict system calibration process is designed.4.Some experiments are performed to verify the methods of thermal error compensation and TCF rapid calibration.Experimental platforms are established for each part of the research about the accuracy maintenance for the robot.The validity of the methods is verified by analyzing experimental data,and some further improvements are proposed according to the experimental results.