Calibration And Trajectory Planning Of SCARA Robot

With the growing and developing of automation industry in China day after day,industrial robots are widely used.But the main problem is that the robots positioning accuracy are not good enough,which can make mistake when the robot is working after offline programmed and the trajectory interpolation of some simple shapes in the robot sometimes cannot meet the requirement.In this dissertation,SCARA robot is the main research object,and its kinematic model error is calibrated and compensated,and the trajectory planning is carried out.Based on the MD-H model,the kinematics of the SCARA robot is modeled and the kinematics of the SCARA robot is solved.The source of positioning error and rotation error are analyzed,and the calibration model and compensation algorithm are established.The position error calibration model and the distance error calibration model are established for calibrating the position error.When using the position error calibration model to calibrate the robot,it is first necessary to measure the robot's base frame and then fit it so that the position error of the robot can be measured under the frame of the robot,but the distance error can be measured directly used.After the calibration based on the laser tracking,a more convenient and quick method with a four-hole calibration plate which is placed in the working area of the robot is designed.The plate works with one bar fixed on the robot's end effector then the robot model error can be calculated.After the positioning error calibration of the robot is completed,a vision system is selected as the measurement tool to calibrate the rotation error of the robot.It is also found that the vision system can be used to calibrate the positioning error and can meet the requirements.According to the motion characteristics of SCARA robot,the trajectory planning is carried out.Taking into account the existing several simple shape trajectory planning in robot control,such as: arc and straight line planning sometimes cannot meet the requirements,because the robot's trajectory may be irregular shape or have some complex features,so NURBS curve is used to interpolate the trajectory of the robot.The trajectory is interpolated based on the adaptive interpolation algorithm and the velocity is controlled with the S-type velocity curve.