Simultaneous and on-line calibration of a robot-based inspecting system

•A method for simultaneous and on-line calibration of a robot-based inspecting system is proposed.•The inspecting system can be calibrated without external measurement devices.•The proposed method simultaneously calibrates the inspecting system in one step to avoid error propagation.•The paper analyzes and eliminates redundant kinematic parameters in the inspecting system's model and derives a MDH model without redundancy.•Experiments are conducted on a 6 DOF serial robot to validate the good performance of the proposed method.

For a robot-based inspecting system calibration procedure in the production environment, it is desirable that the calibration technique should be automatic, time-saving and convenient to implement. The paper presents a new self-calibration method to calibrate and compensate for the robot-based inspecting system's kinematic errors. Compared with traditional calibration methods, this calibration approach has several unique features. First, the inspecting system can be calibrated without external measurement devices since an optical sensor is mounted to the robot end-effector as its integral part, so it can make the inspecting system realizing on-line calibration. Second, it simultaneously calibrates all the kinematic parameters of the inspecting system in one step to avoid error propagation rather than calibrate the hand-eye relationship, the robot itself and the robot exterior relationship separately. Third, the paper analyzes and eliminates redundant kinematic parameters in the inspecting system's kinematic model and derives a MDH model without redundancy. These features not only realize the automatic calibration of the inspecting system but also greatly reduce the number of identified parameters and avoid error propagation, therefore, enhance the efficiency and accuracy of parameter estimation. Experiments are conducted on a 6 DOF serial robot-based inspecting system to validate the good performance of the proposed method.

Graghical abstractFig. 1. A robot-based inspecting systemAs we know, a robot-based inspecting system includes three coordinate transformation relationships (THS,BHT and PHB). Compared with traditional calibration methods, the paper proposes a global kinematic model without redundancy to simultaneously calibrate all the kinematic parameters of the inspecting system in one step to avoid error propagation. What is more, it is a self-calibration method and can be used to calibrate the inspecting system periodically and automatically in the production environment.Download high-res image (152KB)Download full-size image