Investigation Of Joint Clearance Effects On 6R Serial Mechanism’s Dynamic Performance And Pose Error

Since great achievements have been gained in modern science and technology, there’re higher performance requirements in the fields of aerospace industry, medical devices and Industrial automation equipment. High speed, high precision, high efficiency have become important symbols of modern machinery. In order to analysis the comprehensive performance of mechanical system more accurately, joint clearance will be taken into consideration this time. In this paper, the key issues of the industrial robot’s dynamic performance and pose error with joint clearance will be investigated to lay a solid foundation for the mechanism design, reliability analysis and stability control. The contents are as followings:First, a 3D mathematic model for revolute joint with clearance has been established. Since the changeable clearance size caused by axis’ s translation and rotation has been taken into consideration, the model is more accurate to judge the contact mode. By analyzing the simulation result of a collision caused by the 3D imperfect revolute joint, a suitable contact force model has been selected to describe the contact process in detail.Establish dynamic equation of mechanism with joint clearance and develop a computation algorithm with Matlab. Based on the dynamic simulation results above, analysis how clearance sizes, driving speed and joint material’s parameters affect the dynamic performance of the whole mechanism. The simulation results show that the mechanism’s acceleration is very sensitive to clearance’s size, the larger the clearance’s size is, the more intensive of vibration is. It also shows that raising the driving speed in a certain range is beneficial to improve the stability of the operation, as well as to decrease the impact force between joint elements. What’s more, the material of the imperfect joint shows a comprehensive influence on the dynamic performance of the mechanism. The larger the contact stiffness is, the larger the impact force is and a shorter contact time is needed. The larger damping coefficient is, the more energy is lost during the collision. A larger friction coefficient can make the acceleration’s vibration more seriously, so as to deteriorate the mechanism’s dynamic performance.Establish dynamic pose error analysis model of 6R serial mechanism with imperfect joints. Quantitatively analysis the pose error of the end effector and compare the results with the ones calculated in static pose error analysis model. It shows a noteworthy bias between the two results. So when the mechanism is working at a high speed and under a heavy load, it’s better to use dynamic pose error analysis model to compute the pose error of the end effector and it seems to be more accurate.