56.4 Calibration
In this section, the model-based approach to improve robot work cell accuracy is presented. The first step of the calibration process is to acquire a set of measurements containing the pose of the end-effector frame relative to a fixed measurement frame and the corresponding joint angles at that pose. This set of measurement data will be used to optimize the set of parameters pi for i = 1, ... , n+1 in the robot kinematic model (12), where n denotes the number of robot joints, to best describe the end-effector pose given a set of joint angles. The frame assignment used in this section is illustrated in Fig. 2 for a 6-link robot. The reference frame used in this section is the measurement frame {K0}.
Fig. 2 Frame assignment for calibration
Fig. 5 Experimental setup
Table 1 Summary of calibration results
Table 2 Sensor frame poses before and after calibration
Fig. 6 Calibration results based on proposed calibration algorithm
Table 3 Error between computed and measured poses (after verification)
Table 4 Error between desired and measured poses (after implementation)
Fig. 7 Randomly generated poses in 800 mm diameter sphere