Research On Calibration And Measurement's System For Industrial Robot Based On Cable Actuated Position Encoder

The absolute position accuracy of robots must be guaranteed to achieve automatic production. The absolute position error of a robot without being calibrated can achieve several millimeter, which can't satisfy the requirements of automatic production using robots. In order to make sure of robots' handling mission with high efficiency and reliability, the position information of robots' tool center point is also needed for analyzing their performances. Therefore, a calibration and measurement's system for industrial robots based on cable actuated position encoder is developed.The paper determines data acquisition scheme and overall structural layout of this system after verifying the system's necessity at first. Then the robots' calibration algorithm and measurement algorithm based on cable actuated position encoder is proposed under the requirements of system's overall scheme. The position of data acquisition equipment is regarded as a part of robot's errors transforming process. With the iteration of calculating data acquisition equipment's datum and identifying robot's structural parameter errors when applying calibration algorithm, the robot's structural parameters are compensated finally. Measurement algorithm mainly includes coordinate solving model and initial position referencing model. For coordinate solving model, three dimension coordinate of measurement point is obtained through the distance between robot's tool center point and base station's datum and the position of all base stations. Structural layout that the base stations can be moved is adopted in the system, so the position of base stations is unknown before taking measurement. The D-H(Denavit—Hartenberg) model representing relationship between each base station is established in initial position referencing model. The transform matrix between each base station and reference coordinate can be calculated by easy referencing process using initial position referencing model.The system's detailed structural design is completed according to its overall scheme and key algorithms. Then system's prototype is established and the software integrating calibration algorithm and measurement algorithm is developed. Finally, the calibration experiment and measurement experiment are carried out on the system's software and hardware platform, and the system's feasibility and accuracy is verified preliminarily via experiments.