Research On Dynamic Correction Of Robot Pose Errors Towards Intelligent Manufacturing

In the field of large-scale high-end equipment manufacturing,the equipment components and overall manufacturing and assembly processes have manufacturing technology requirements and challenges such as large processing space,oversized manufacturing dimensions,ultra-precision machining,and high-precision assembly.An intelligent in-situ manufacturing system using robots and laser trackers as a manufacturing body provides a solution to the above requirements.Industrial robots,as the implementing agency of in-situ intelligent manufacturing,intelligent manufacturing and flexible manufacturing of high-end equipment products have put forward higher requirements for high-precision absolute pose measurement and control technology of industrial robots.Robotic on-line machining is a complicated multi-variable dynamic changing process.A variety of error factors affect the robot end pose accuracy.The action mechanism of each error source is different.With the robot's movement status and space-time changing,its distribution law and influence degree change accordingly.Thus,the real kinematics parameters of the robot change dynamically with the workspace,state,and environment,and the parametric description of the pose cannot be accurately obtained.Therefore,the single static parameter calibration result in the existing kinematics calibration technology cannot adapt to the multi-factor comprehensive effect with the multi-workspace domain change.The reliability of robot on-line absolute pose accuracy and the adaptability of the workspace domain cannot meet the high precision operational task requirements in large-scale equipment manufacturing.This paper aims at the pose precision requirements of industrial robots in manufacturing site environment.These theories and applications research oriented to intelligent manufacturing for industrial robots on-line pose error correction are carried out.Based on the further study of the error generation mechanism of industrial robots and the nonlinear variation of robot kinematics parameters,six degrees of freedom measurement technique with laser tracking is used to construct a new online kinematics pose error model and monitoring platform for industrial robots.Dynamic estimation calibration and compensation correction of comprehensive error is globally optimized.This realized high-precision online correction and guidance of robot pose.This thesis elaborated the basic principles,solving methods and key techniques of pose measurement,coordinate system transformation,error estimation and compensation,and completed the experimental verification.The main research contents of the thesis are summarized as follows:1.The error estimation method and calibration mechanism of the D-H model parameter calibration method for robot kinematics were studied,and the influence of the static parameterization constraint for pose error in workspace domains was analyzed.The experiment of error calibration using parameter optimization for six degrees of freedom joint robots was carried out.It was verified that the end pose error estimation of a robot exist problem of adaptability and reliablity in robot whole workspace domains.2.Based on a portable laser tracking system developed by the project group that supported the thesis,a photoelectric tracking and beam steering servo controlling of a laser tracking system was studied.For the measurement of large-scale space dynamic targets in industrial environments,six degrees of freedom pose measurement method based on laser tracking was studied.An integrated dual-mode six degrees of freedom measurement method based on laser beam transmission is proposed and applied for the robot's end position online tracking measurement.The 6-DOF pose measuring device calibration and pose measurement experiments were carried out.3.Aiming at the requirements for online laser tracking measuring and real-time correcting robot position and orientation,a rapid calibration conversion and solution method for robot coordinate frame and laser measurement coordinate frame is proposed.Based on the principle of distance,the coordinate of the optical tool center point(TCP)at the robot end is estimated.Using the space point coordinate center of gravity configuration,and the least-squares optimization algorithm based on the Rodrigues matrix transformation,the orthogonal rotation matrix in the pose relative transformation are solved to obtain.The equivalent similar transformation of coordinate frame of robot measurement system was studied.The description of orientation change model of robot end tool was established.The orientation angle solution method in measuring calibration process was given.4.The pose error estimation was carried out aiming at the robot whole workspace domain.A dynamic estimation and calibration method for synthetic robot kinematic errors based on non-parameterization constraints is proposed.The end pose errors of multiple factors are attributed to periodic dynamic functions change related to the joint rotation angle variables,and the dynamic function descriptions that represent and imitate the online change law of robot errors was realized.Based on the error equivalent differential variable and equivalent differential transformation of the link coordinate frames error,a dynamic non-parametric constrained error model was established.The joint motion coupling law of multi-link coordinate system of series robot was studied.The online decoupling transformation and compensation algorithm of multi-link coordinate system was designed.The algorithm simulation and experimental comparison experiments were carried out.5.Based on the idea of online,dynamic,real-time and comprehensive compensation of robot pose errors,an online error correction method with calibration pre-compensation and online correction guide was proposed.The online compensation mechanism of pose error and the online error information fusion method were studied,and the error correction mathematical model and compensation algorithm were established.Then an online robot pose observation and control experiment platform was built,the compensation algorithm was verified and online dynamic correction experiment of position and orientation errors were performed.The online high-precision absolute pose control of industrial robots was realized.