Research On Robot Control Technology Based On EtherCAT

Based on the research on kinematics and trajectory control technology of six-axis serial manipulator,EtherCAT technology was used to realize the motion trajectory control of six-axis serial manipulator.It lays a foundation for the subsequent research on trajectory control technology of multi-joint manipulator with complex trajectory and high-precision trajectory.Robot kinematics is the basis of motion control technology.This paper introduces the knowledge of coordinate transformation and forward and inverse kinematics of robot,and proposes a method of calculating inverse kinematics of serial six-axis manipulator based on analytic geometry.The terminal pose is represented by three feature points instead of the common homogeneous matrix.When calculating the inverse solution,the possible attitude of the manipulator’s connecting rod when the end pose reaches the target pose is analyzed first.Based on one of the postures,a set of possible inverse solutions are obtained according to the geometric relations between the links.Consider axis 1,3,and 4 as key axes.There are two solutions for each key axis under the orientation of the terminal target,and another possible solution for each key axis is analyzed and calculated.By combining the solutions of the three key axes,eight groups of solutions of the key axes are obtained.The rotation angles of other axes were calculated according to the key axis rotation angles,and 8 sets of solutions were obtained for the rotation axis rotation angles when the end pose reached the target pose.Finally,it is proved that the inverse algorithm is accurate and feasible by means of experimental calculation.Then the trajectory planning and interpolation of the manipulator are introduced.The calculation process of trajectory planning is complicated when the terminal pose is represented by homogeneous matrix.The terminal pose is represented by three feature points,which can simplify the calculation process of trajectory planning.The trajectories of the terminal pose are represented by three trajectories of three feature points.Trajectory planning is equivalent to planning the motion trajectories of the three feature points respectively.The proposed robot trajectory was interpolated,and the joint Angle of the interpolation point was calculated by the inverse solution algorithm.The obtained joint Angle curve was used to control the rotation of the rotation axis,so as to realize the trajectory motion of the manipulator.The trajectory planning of straight line and spiral curve based on three feature points is proposed,and the trajectory motion simulation is carried out on MATLAB,which verifies the feasibility of the proposed trajectory planning and interpolation method.Finally,according to the principle and constitution of EtherCAT system,the corresponding equipment was selected to build the experimental platform.EtherCAT was used to control the trajectory of the manipulator.The joint Angle data corresponding to the interpolation points of the trajectory were calculated by MATLAB.The motion control program is written on TwinCAT3 software,and the joint Angle data is inserted into the control program to realize the motion control of the manipulator.Experimental results show that EtherCAT technology is feasible to realize the traj ectory motion control of a series six-axis manipulator.