Influence Of Each Of The Geometric Errors On The Total Displacement Error Of The Machine

An algorithm for volumetric calibration is developed and verified practically by measuring of all geometric errors after numerical compensation. In this paper, analysis of the contribution of each of 9 translational and 9 rotational position dependent errors and each of 3 position independent errors in total displacement error vector is presented. Changing only one of the errors, and keeping all the others unchanged, the final total error is examined using the simulation based on forward calibration part of the calibration algorithm. The measurement of all 21 volumetric errors is expensive and time consuming. Instead of numerical compensation in the controller, this analysis yields opportunity to enhance accuracy of the machine, measuring and making correction of only few of the geometric errors. Results from the simulation showed that position independent errors have most significant influence on total displacement error. Decreasing of the squareness error S XY improves the mean of norms of total displacement vectors about 25%, and percentage of improvement for squareness error S ZX is about 20%. If all squareness errors are reduced by factor 0.04, then total improvement is more than 51%

Computer-based simulation and validation of robot accuracy improvement method and its verification in robot calibration procedure

Algorithm for improving accuracy of six-axes robot is developed and validation method based on computer simulation is implemented. Optimization is used to minimize the distances between nominal and actual positions of the tool. That way, the parameters of the robot are calibrated and using such calibrated parameters, accuracy of the robot is significantly enhanced. Measurement is done using API Radian laser tracker and experimental data is collected on KUKA 480 R3330. For the set of 75 points used for calibration, simulation predicted reduction of the mean of the total displacement error from 1.619 mm to 0.174 mm. After that, the same points were used for verification procedure. Another measurement is performed, using the calibrated parameters and numerically calculated compensation of the machine coordinates of the robot. The mean of total displacement error was 0.293 mm and that way the correctness of described method is verified