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Underwater Robots - Gianluca Antonelli.pdf

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[N]<br />

[m]<br />

350<br />

300<br />

250<br />

200<br />

150<br />

100<br />

50<br />

0<br />

0.2<br />

0.1<br />

0<br />

−0.1<br />

8.5 Explicit Force Control 213<br />

0 5 10 15<br />

time [s]<br />

˜y E<br />

˜x E<br />

−0.2<br />

0 5 10 15<br />

time [s]<br />

Fig. 8.5. External force control. Force along z (top) and end-effector error components<br />

along the motion directions (bottom) without exploiting the redundancy<br />

and without unexpected impact<br />

singularity. Asuitable use of the system’s redundancy allows to reconfigure<br />

the system and to achieve the secondary task.<br />

Finally, inFigure 8.8 the time history of the primary task variables in<br />

case of an unplanned impact is shown. It can be noted that the undesired<br />

force along x ,due to the unexpected impact, is recovered yielding anon-zero<br />

position error along that direction.<br />

8.5 Explicit Force Control<br />

In this Section, based on [119] two force control schemes for UVMS that<br />

overcome many of the above-mentioned difficulties associated with the un-

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