Design Of Control System For Six-Axis Robot Based On EtherCAT Communication Protocol

In recent years,the concepts of ‘German Industry 4.0' and ‘Made in China 2025' have been put forward constantly,indicating that advanced manufacturing technology has become the key factor of manufacturing competition in various countries.Industrial robot as an automation,precision,intelligent equipment has an important strategic position in improving manufacturing productivity.The six-axis industrial robot has higher motion flexibility than the traditional three-axis and four-axis robots.Six-axis industrial robot consists of three parts: control system,robot body and drive system.This paper establishes the research goal from the aspect of control system,including:(1)A real-time industrial Ethernet technology-EtherCAT,which has good reliability and strong anti-interference property,is studied in this paper.By analyzing the communication protocol of EtherCAT,the master station and slave station are built with TwinCAT to complete the control of six-axis industrial robot.(2)The model of six-axis industrial robot is obtained according to DH modeling theory,the forward kinematics and inverse kinematics of six-axis industrial robot are analyzed,and the analytical solution of inverse kinematics is deduced.Through the irreversibility of Jacobi matrix,the singular position of six-axis industrial robot is deduced,and the joint attributes are divided.According to the joint attributes,a group of inverse kinematics multiple solutions is selected and verified by simulation on Matlab platform.(3)Based on the previous chapter,the trajectory planning of six-axis industrial robot is studied.The interpolation algorithm of velocity constraint and acceleration constraint in joint space are analyzed.The method of heuristic function is used to solve the problem of specifying velocity and acceleration of intermediate point.The linear interpolation and circular interpolation in Cartesian space are analyzed,and the circular interpolation is connected with the superior and inferior arcs of the fixed ending point,which simplifies the condition of judgment.(4)The PI gravity compensation controller is designed for the six-axis industrial robot.By using the Mathematic platform,the analytical formula of the gravity moment of each joint is derived by Lagrange equation,and the range of variation of the gravity moment is simulated.The thermal energy of the motor is estimated by integrating the instantaneous current and the output of the controller is limited by saturation,which ensuring the temperature of the motor is not too high and burned down.(5)According to the research contents of the previous chapter,the control system software is designed for the robot,and the task is divided into motion control module and Visualization module.This paper introduces the whole control architecture,the task assignment of control function,the realization method of each module,and through examples to verify the above parts.