Motion Reliability Analysis And Optimization Of Serial Robot

Serial robots currently occupy a pivotal position in the field of industrial development.In this field,serial robots are not only widely used in automotive welding,casting and other operations,but also begin to be used in more demanding operations such as dimensional inspection and precision assembly.However,from the current research,most serial robots cannot meet the requirements of high reliability and high precision.Therefore,this paper analyzes the motion reliability of the RB08 serial robot under the influence of joint parameter error and joint clearance,and performs multi-objective topology optimization,which provides an effective method for improving the robot's motion accuracy.The main research contents are as follows:1)Based on D-H modeling method,determine D-H parameters of RB08 serial robot,establish kinematics model,and conduct forward kinematics analysis.Find the transformation matrix of the end effector relative to the base coordinate system,and derive the generalized coordinates of the end effector.The transformation matrix of end-effector relative to the base coordinate system is obtained and the generalized coordinates of end-effector are derived.On the basis of kinematics analysis,the pose error model of the end-effector of the serial robot is derived.Monte carlo method is used to solve the RB08 serial robot workspace.2)Considering the error of joint parameters,analyze the reliability of the serial robot's motion accuracy.Based on the RB08 serial robot position error model,the end-effector point reliability model and time-dependent reliability model are established.By introducing the concepts of upper and lower crossing rates in mechanism reliability analysis,combining the first-order second moment method and the poisson approximation method of first-crossing,the analytical expressions of time-dependent reliability of robot end-effector are derived,and the established reliability model is solved.It is found that the time-dependent reliability is always less than or equal to the point reliability.Obviously,the time-dependent reliability results are more reasonable.3)Considering the joint parameter error and joint clearance,analyze the reliability of the serial robot's motion accuracy.Assuming that the joint axis of RB08 robot is parallel to the axis of the hole,the joint clearance is simplified to a planar two-dimensional vector.Based on cut hybrid dimension reduction method,the statistical correlation of joint space clearance is processed.Kinematics analysis and error analysis are carried out on the robot,and the motion reliability model is solved by combining the first-order second moment method and envelope method.By comparing the obtained failure probability curve with the failure probability curve under the influence of a single factor,it is found that the joint clearance will also affect the kinematics reliability of the robot,which cannot be ignored in the process of developing and designing the robot.4)In order to reduce the vibration deformation generated during the movement of the robot and improve the reliability of the motion accuracy,a static and dynamic multi-objective topology optimization method is proposed.Combining multi-level tolerance sequence programming and the eclectic programming,multi-optimization targets are processed in a hierarchical manner to avoid large-scale targets dominating the optimization results.Optistruct is used for static and dynamic multi-objective topology optimization,and the optimized structure is redesigned.The improved rigidity of the new structure of the arm and the low-order natural frequency have been improved,and the vibration deformation has been reduced to achieve the purpose of optimization.