Study On The Dynamic Response Of The Working End Under The Clearance Effect Of The Hinged Joint Of A Mechanical Arm

With the rapid development of science and technology,robots are used more and more.Robot is a complex system,which consists of multiple components connected by motion pairs.However,due to the existence of the clearance of the motion pair,the robot will deviate from the ideal state in the actual motion,and the collision between the two pairs of elements will occur,which will affect the stability of the robot system.Therefore,in order to ensure the stability and reliability of the robot,it is of great significance to study the dynamic response of the end of the robot under the clearance effect of the hinged joints of the manipulator.In the research of this paper,the research object of this paper is the NACHI robot.Firstly,the 3D model is built for the object of study,and then the dynamic simulation is carried out by using ADAMS.The influence of clearance on the running process and the executing end of the robot is analyzed,and the effect of the running speed of the hinge joint on the running process and the executing end of the robot is also analyzed.Finally,the conclusion with certain reference value is obtained.This paper mainly studies from the following aspects:(1)Aiming at the dynamics of robot with clearance,this paper first studies the gap structure between the kinematic pairs of hinged joints,and then establishes the contact collision model between the two elements of the kinematic pair.At the same time,the friction model between the two elements of the motion pair is established.Finally,the dynamic model of the multi-body system with clearance is established on the basis of the dynamics of the multi-body system.(2)Based on the dynamic simulation analysis of the NACHI robot,the simulation data of the robot with no gap is compared with the simulation data of the robot with the gap.Firstly,the kinematics model of the robot is established by D-H coordinate method,and the dynamic model of the robot is established by using the multi-body dynamics model with gaps.Then the three-dimensional model of the robot with and without gap is established by Solid Works.The model of robot with clearance is divided into three kinds of gap robot model with clearance accuracy,and then it is introduced into the ADAMS software for experimental simulation.The results of dynamic response are compared with those of the robot without gaps.The results show that the gap has little effect on the displacement and velocity of the end of the robot,but has a great effect on the acceleration at the end of the robot.(3)In view of the effect of different clearance and different driving speed on the dynamic response of robot,two groups of different driving velocities,symmetrical angle and symmetrical trapezoid,are adopted in this paper.Then the dynamic response of the robot with different joint clearance accuracy is compared at the same driving speed.It is found that the impact force in the extreme position is too large when the precision is too high and the collision force is too large in the normal operation process when the precision is too low.Finally,it is obtained that the more suitable precision of the robot model is IT8 under two different driving speeds of symmetrical angle and symmetrical trapezoid.(4)Aiming at the different effects of symmetrical angular driving velocity and symmetrical trapezoidal driving velocity on the robot with clearance,this paper simulates two groups of manipulator with clearance driven by speed,and compares the simulation results.Finally,the dynamic response performance of the robot with clearance at symmetric angular velocity is better than that of the robot with clearance under symmetric trapezoid velocity.Therefore,the acceleration time should be prolonged as much as possible when selecting the driving speed of the robot,which will be beneficial to the stability of the robot in the process of operation.