Kinematics Calibration And RTCP Test Of A 5-DOF Hybrid Robot

With the rapid development of aerospace,railway transportation,large-scale shipping and other fields,there is a large number of demand for on-site processing,assembly and maintenance of large structural parts.Large-scale structural parts have the characteristics of large size,complex geometry and high precision requirements.There are many technical difficulties in their manufacture and maintenance.In order to adapt to the service environment of large-scale moving and local high-speed precision machining,the single machine manufacturing unit or multi machine manufacturing system with parallel/hybrid equipments as the core functional component is gradually becoming an indispensable tool.Geometric accuracy is one of bottleneck problems restricting the extension of application of the hybrid robot.On the premise of having a certain basic manufacturing accuracy,kinematic calibration is an effective means of improving the geometric accuracy.In the study,the kinematic calibration technology of a new-type5-degree of freedom(DOF)hybrid robot was investigated.Moreover,by applying a regularization method,the problem whereby the identification algorithm shows poor robustness due to the presence of an ill-posed identification matrix during error identification was solved.At first,a geometric error model for hybrid robots satisfying completeness and minimality was established based on screw theory.Then,when identifying error parameters,two indices for evaluating the effectiveness of identification algorithms were proposed,and on this basis,the stabilities of solutions obtained through four regularization identification algorithms and the predictive capability of solutions for the model was analysed and compared by simulated experiment.Additionally,the influence of measurement noises at different levels on five identification algorithms was explored.Finally,an error compensation strategy was proposed and a kinematic calibration experiment was conducted.The test results showed that,after kinematic calibration,the position and orientation errors of hybrid robots within the whole workspace separately reduced to less than 0.054 mm and less than 0.041?,thus validating the effectiveness of the proposed method.RTCP detection technology is an effective way to test the comprehensive accuracy performance and processing ability of five axis machining equipment.This paper focuses on the application of RTCP detection theory and technology in hybrid robot.Firstly,based on the multi-objective optimization algorithm,the position of RTCP inspection center and the maximum inspection attitude angle of the hybrid robot are obtained,so that the robot can increase the corresponding motion range of the active joint in the joint space as much as possible on the premise that the operation space has the maximum detection range of attitude angle.Then,three kinds of standard RTCP test trajectories and an optimized 8-shaped trajectories are designed and planned.Finally,the minimum curvature radius of RTCP trajectory is calculated,the maximum interpolation step length of NC instruction is determined,and the corresponding NC instruction is generated according to the planned inspection trajectory,and then the RTCP accuracy detection experiment of hybrid robot is carried out.Experimental results show that on the basis of kinematic calibration,RTCP method can effectively detect the dynamic error of the hybrid robot by checking the end position error,and then evaluate the five-axis linkage accuracy of the hybrid robot.