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Fig. 16.7 A comparison between the hybrid visual servoing schemes under a pure translation
displacement: (a) control scheme in Section 16.3.3.2; (b) control scheme in Section 16.3.3.3;
and (c) control scheme in Section 16.3.3.4
Experiment 2 . In this set of experiments, the three hybrid schemes are compared
when only a translational motion t =[80 80
40] cm has to be realized. The results
are shown in Figure 16.7. It can be observed that the behavior of the three control
schemes is similar. These results confirm also that the control scheme based on the
features ρ i
ρ i seems to be the most sensitive to measurement noises. One can also
observe a nonzero rotational velocities at the beginning due to the measurement
noises and calibration errors.
Experiment 3 . In this set of experiments, only a rotational motion about the Z -axis is
considered. The control laws B , C and D are first tested with a huge rotation of 140
deg. In this case, only the control law C allows to reach the desired configuration.
When using the control laws B and D the robot reached its joint limits due to the
coupling between rotational and translational motions. In the results shown in Figure
16.8, the rotation about the Z -axis is reduced to 90 deg for the control laws B and D .
Finally, the full decoupling between translational and rotational motions provided
by the control scheme C can be clearly observed.
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