Simulation Analysis Of Position Reliability Of Industrial Robots Under Multiple Factors

Since the last century,industrial robots have been widely used in modern manufacturing industries such as automobile manufacturing,chip production and engineering instruments.Because of the advantages of high safety,high productivity and high versatility,industrial robots have become an effective way to fill the labor gap in the current context of the gradually disappearing demographic dividend in China.The research on positioning accuracy of robots mainly includes two aspects: repetitive positioning accuracy and absolute positioning accuracy.As an important technical index to measure the performance of robots,the positioning accuracy of robots is usually well guaranteed in terms of repetitive positioning accuracy,but for the same robot,its absolute positioning accuracy is often low,which makes it difficult to meet the needs of modern manufacturing industry.Therefore,with the help of virtual prototyping technology,the paper investigates the absolute positioning accuracy of robot end-effector under the influence of multiple factors.The error modeling and reliability study is carried out for a six-degree-of-freedom tandem industrial robot considering geometric errors,joint gaps and flexible deformation of the linkage.The main research contents are as follows.Firstly,a study of the reliability of the robot considering geometric errors was carried out.At the very start,the error sources of the robot were analyzed.Then a structured decomposition of the robot was carried out based on the meta-action theory to establish the Function-Motion-Action(FMA)decomposition tree.The error modeling considering the variation of structural and motion parameters of the robot was carried out through the error transfer mode between the meta-action chains,and the main error sources affecting the position accuracy of the end-effector were analyzed.It is found that the joint torsion angle has the greatest influence,followed by the joint rotation angle,and the errors of linkage bias and linkage length have relatively small effects on the end-effector position of the robot.Then,a reliability study considering the joint clearances of the robot was conducted.Firstly,3D modeling of the industrial robot was carried out,and kinematic simulation without considering joint clearance was performed using virtual prototype technology.Then,assuming that the axes in the robot joints are parallel to the axes of the axis holes,the kinematic sub-clearance vector was simplified to a planar two-dimensional vector,and the kinematic simulation of the robot considering the kinematic sub-clearance was performed.Finally,the effect of each joint clearance amount on the motion accuracy of the end-effector was analyzed separately.It is found that under the influence of gravity,the absolute positioning accuracy of each joint has the lowest reliability in the gravity direction when the clearance exists,and reducing of it can improve the reliability to a certain extent.Finally,a reliability study considering the flexible deformation of the robot linkage was conducted.Under the condition that gravity was set,the static analysis of the industrial robot was firstly carried out;then some of the rods were flexibly processed,and the simulation and analysis of the motion accuracy of the end-effector were carried out for different loads.It was found that the absolute positioning accuracy of the robot endeffector under the influence of gravity was significantly less reliable in the gravity direction than in other directions;and the increase of the end load amplified this gap.