Calibration of multi-robot system without and under load using electronic theodolites

The new algorithm of the kinematic calibration of robot system using two electronic theodolites is presented. All measurements are carried out relatively to the global, Cartesian coordinate system (GCS) based on three markers fixed on the walls of measurement laboratory instead of system fixed to the theodolites. Since marker distances are measured with relatively low accuracy an error correction procedure was applied. The presented algorithm was applied first to the calibration of two-robot system with five and six degree of freedom respectively. The parameters of robot kinematics were estimated using optimisation procedures. All calculations were performed for coordinates measured in GCS giving significant improvement of robots accuracy. Moreover, using the algorithms developed the calibration of serial-parallel robot was performed. To compare results of robot calibration obtained for robot without load and under load the measurement stand for robot calibration was designed. The serial-parallel robot was calibrated both under load and without load and results obtained were compared.