The Research On Direct Teaching And Collision Detection Of 7-DOF Collaborative Robot

Collaborative robots are designed to reduce the risk of injury and can safely interact with humans directly.They are more collaborative and safe than traditional industrial robots.The objective of collaborative robots is to combine the repetitive performance of robots with the individual skills and ability of people.People have an excellent capability for solving imprecise exercises and robots exhibit precision,power and endurance.In this paper,7-DOF(Degree of Freedom)collaborative robot is taken as the object of research,robot direct teaching,teaching playback and collision detection are deeply studied in order to improve the cooperation and security of the robot.The main research contents of this article are as follows:(1)Dynamic modeling and parameter identification of 7-DOF robot.Newton-Euler method based on screw theory is used to establish the dynamic model of 7-DOF collaborative robot,and static friction + coulomb friction + viscous friction theory is used to establish the joint friction model of 7-DOF collaborative robot.The dynamic inertial parameters of the robot are obtained using SolidWorks,and the friction model parameters of the robot are identified using the WLS(Weighted Least Squares)method.The simulation experiment of 7-DOF collaborative robot dynamics model without friction model is accomplished in Simulink platform.(2)Robot direct teaching without external sensor.7-DOF collaborative robot end-payload dynamic model is established and experimented in Simulink platform.This paper improves 7-DOF collaborative robot friction model.Based on robot dynamics model with end-payload dynamic model,use torque control based zero-control method to achieve robot direct teaching.The robot direct teaching experiment is accomplished and the results show that the operator can quickly,flexibly teach the robot with end-payload by using the method in this paper.(3)Robot teaching playback.According to the robot actual application,this paper divides the robot teaching playback into teaching point playback mode and teaching trajectory playback mode.In the study of the teaching point playback model,operator can switch different coordinate systems in the teach pendant to change the movement trajectory of the robot,add or delete teaching points to meet the actual application requirements.In the study of the teaching trajectory playback model,including data extraction,data smoothing.By comparing three different smoothing methods,a teaching trajectory mode algorithm based on cubic B-Spline curve smoothing method is proposed.The robot teaching playback experiment is accomplished,and the results show that the robot teaching playback can be realized by using the method in this paper-and meet the actual application requirements.(4)Robot collision detection without external sensor.Using a method based generalized momentum to establish momentum deviation observer to realize collision detection of robot without end-payload.An end-payload torque elimination algorithm is proposed that can eliminate the torque of the end-payload on the robot joints.Combine the two methods to propose a robot collision detection algorithm with end-payload.The simulation experiment is accomplished in Simulink platform,and through the comparison of the simulation results,the effectiveness and feasibility of the proposed robot collision detection algorithm with end-payload is verified.The robot collision detection experiment is accomplished and the results show that using the method in this paper can effectively and quickly detect whether the robot with end-payload has collided.