The Research Of Calibrating A Delta Robot Based On The Visual Metrology

In many fields of robot research,the improvement of robot precision is an important research.In industrial production,off-line programming and other environments that require high accuracy,the improvement of robot accuracy is particularly important.The technology of robot calibration can improve the accuracy of the robot by modifying the robot control software without changing the mechanical structure of the robot,the robot that does not meet the precision requirement can be put into use again without having to replace it,thus reducing the production cost.The technology is not only effective but also economical.The robot calibration is generally divided into four stages: modelling,measurement,identification and compensation.This article completes the calibration of the Delta robot according to the calibration sequence,the main research work is as follows:(1)First,the mathematical model of Delta robot calibration is proposed.The Delta robot forward kinematics equation and monocular vision measurement technology are combined to propose a model for this calibration.Determine the position of the robot end effector in the robot coordinate system through the robot forward kinematics equation,and use the monocular vision measurement technology to calculate the position of the camera's optical center in the world coordinate system,and establish the Delta robot according to the positions in the two coordinate systems Calibration model.At the same time,a mathematical model of the Delta robot calibration verification is proposed with the help of the side measurement method.(2)Secondly,the measurement method in the calibration process of the Delta robot is determined.This paper proposes a measurement method based on vision measurement from the perspective of measurement cost and operational complexity.In the specific measurement process,an improved method was proposed for the existing degenerate configuration problem,and the improved degenerate configuration problem was verified.When improving the problem of degenerate configuration,different types of auxiliary graphs are used for calibration.When verifying the problem of improved degenerate configuration,the idea of geometric calibration is used.Apply the improved measurement method to the experiment,repeat the operation,and complete multiple measurements of known parameters.(3)Then,the method of parameter identification and error compensation for Delta robot calibration is proposed.In the identification process,the Levenberg-Marquardt(LM)optimization algorithm and the Random Sample Consensus(RANSAC)algorithm are applied.Firstly,the existing calibration model is used to determine different optimization objective functions,so as to solve the unknown parameters in the objective function.Secondly,the RANSAC algorithm is used to filter the data with large experimental interference factors.After the parameter identification is completed,the calibration model is added to the robot driver to compensate the errors of the Delta robot.(4)Finally,analyze and demonstrate the concept proposed in this experiment.In order to verify the effectiveness of this experiment,a Delta robot was built for experimentation.Experimental results show that the improved monocular vision measurement technology meets practical applications,and the method can calibrate the old robot,reconstruct its standard kinematics equations and restore its accuracy.