An approach for predicting the calibration accuracy in planar cable-driven parallel robots and experiment validation

This work presents a method of predicting the calibration accuracy of a 3-DoF, 2-cable, planar cable-driven parallel robot (CDPR). The calibration is realized with the combination of a laser displacement sensor and an inclinometer attached to the moving-platform, as well as the cable encoders. The actual accuracies of the sensors are first experimentally determined for higher calibration quality. Simulation of the calibration are performed from 6 to 50 measurement poses, with 500 repetitions for each pose number to avoid outliers. The simulation results show that the error on the CDPR parameters decreases with the number of calibration poses considered, reaching a plateau of +/- 9 mm of error after approximately 40 poses. The effect of each sensor on the calibration accuracy is studied. Calibration experiments are carried out for a 5.2 m-span CDPR. After verification by an accurate laser tracker, the calibration results match the previous simulation.