Abstract:

The paper concerns problem of determination of positioning errors of an end-effector of an exemplary manipulating robot. The procedure of ISO 9283 standard was the base of determination of a set of 5 measurement points. For comparison, the extended set containing 9 points was also used. Kinematic DH model of a manipulator was applied to determine nominal poses of measurement points. Actual poses were obtained by introduction of small arbitrarily selected changes to parameters of the nominal kinematic model. Simulated measurement results were obtained by sequential modification of actual coordinates by adding pseudorandom error partly corresponding to the simulated measurement errors. Determination of the positioning error was composed of alignment of the robot base frame to the instrument coordinate frame followed by calculation of the positioning error with respect to the aligned base frame. An attempt to improve the initial results consisted in an iterative updating of the alignment using results of estimation of zero joint coordinates offsets.

The simulation results confirmed that erroneous alignment of the robot base frame to the instrument frame was a significant factor influencing accuracy of determination of the positioning error, and that this accuracy might be improved by iterative updating of values of the joint coordinates with the estimated zero joint offsets.