Research On Pose Planning Algorithm For Six-Joint Spraying Robot

As robotic technology has been evolving over the past half century,industrial manipulator has been widely applied in mechanical,chemical,food,medical and other industry,playing a key role in automation and showing its advantage in cost saving,efficiency as well as quantity.In the new economic situation,the use of robots instead of manual spraying is an urgent need for the transformation and upgrading of China's manufacturing industry.In the process of robot automatic spraying,the pose of end-effector has an important influence on the machining quality of the robot.In this paper,a trajectory planning and optimization algorithm is proposed toward a 6 DOF direct-teaching spraying robot.Accounting for manipulation feature of the robot and the manufacturing technique,this algorithm aims to smooth the trajectory of end effector of the robot and its velocity.At first,the manipulator kinematics of the robot is solved,and then the position as well as orientation interpolation algorithm in Cartesian space is discussed in detail.Finally,the entire procedure of obtaining smooth trajectory and optimized velocity,accelerated velocity from noisy scattered teaching way points is presented.At first,the forward and inverse manipulator kinematics,which is modeled via D-H parameters,is solved and verified in the MATLAB robotic toolbox.Secondly,common interpolation methods for robotic trajectory planning in Cartesian space are given,including line interpolation,arc interpolation and NURBS curve interpolation,which is analyzed particularly.We then proceed to the velocity planning for end effector according S-shape acceleration/deceleration model,and present the approach accounting for interpolation residual.As for the orientation planning problem,the parameterizations methods of orientation are analyzed,and then the linear interpolation of orientations based on the unit quaternion is discussed.In view of the multi orientations planning problem in robot spraying process,the quaternion curve is introduced to interpolate the orientations,and the trajectory generation method of the curve is given.A secant-method based quaternion curve interpolation method is proposed for controlling the angular velocity of end effector during the interpolation process.Based on the application and structure characteristics of the six joint direct teaching spraying robot,the pose planning scheme of the robot is discussed,and the position and orientation synchronization method for the position and orientation planning of the robot endeffector is given.The trajectory planning method is simulated and verified by a series of experiments.Finally,a pose optimization algorithm for direct-teaching trajectories based on curve fitting is proposed for the vibration problem.First,the teaching data are resampling,then the position and orientation information in the teaching trajectory are fitted,and the curves are interpolated according to the velocity law in the original trajectory,and the optimal trajectory is obtained.The correctness of the algorithm is verified by analyzing and contrasting the trajectories before and after optimization.