Dynamics Modeling And End Jitter Suppression Of 6-DOF Series Industrial Robot Considering Joint Flexibility

At present,industrial robots are developed with the trends of high precision,high speed,light weight and large span.The effects of robot joint flexibility are becoming more and more obvious.Traditional rigid body system theories cannot accurately describe the dynamic characteristics of robot systems.Since the existence of flexibility will also cause vibration problems during the operation of the robot,the vibration of its end-effector will have a serious adverse effect on the use of the robot arm,so its vibration must be suppressed in practical applications.Supported by the general programs of NSFC(51675306)and Shenzhen NSFC(JCYJ2019082170811682),a six-degree-of-freedom industrial robot XB7L is investigated,which is from ROKAE Company and has a jitter problem at the end during operation.On the basis of rigid body dynamics model and considering the influence of flexibility in robot system,a six DOF robot dynamics model considering joint flexibility is established.On the basis of the dynamic model,the dynamic characteristics of the robot are analyzed,the influence of different system parameters on the robot end flange jitter is studied,the main factors affecting the robot end jitter are analyzed,and finally the control strategy of the robot is studied..First,this paper uses the Kane method to establish a full-rigid six-degree-of-freedom robot dynamics model.Based on the rigid dynamics model,considering the joint flexibility factors,the Spong model is used to simulate the joint flexibility and establish a dynamic model of the joint flexibility.Considering the joint flexibility the six-degree-of-freedom robot dynamic equation is a partial differential equation,which is solved by the numerical algorithm Newmark-? method dynamic equation,and the accuracy of the dynamic model is verified using Adams simulation.Secondly,the dynamic characteristics of xb71 robot are analyzed.Based on the six degree of freedom dynamic model considering joint flexibility,the effects of joint stiffness,connecting rod mass and moment of inertia on the actual output angle and end trajectory of xb71 robot are studied;the actual working condition of xb71 robot with severe end jitter is simulated,and the main factors affecting the end jitter of human are analyzed;the natural frequency is analyzed by modal simulation with finite element.The dynamic characteristics are verified by modal experiments.Finally,the end jitter suppression of xb71 robot is studied.The control algorithm of xb71 robot is PD control based on gravity compensation.In this paper,independent PD control method and PD control method based on gravity compensation are studied.Because the robot has many uncertain factors under the action of different attitude and external force,it is difficult to determine the gravity term accurately.Therefore,when there is an error between the actual output displacement and the ideal output displacement,the gravity term can not be accurately compensated,which leads to the end jitter of the robot.In this paper,the actual output trajectory of the robot controlled by different PD parameters based on independent PD is studied,and the influence laws of different PD parameters on the output displacement are compared,so as to obtain the appropriate proportional differential parameters,which can ensure that the actual output displacement is consistent with the ideal output displacement without gravity compensation,so as to achieve the suppression of the end jitter of xb71 robot Finally,trajectory tracking experiments are carried out to verify the effectiveness of this method for the end jitter suppression of xb71 robot.