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Underwater Robots - Gianluca Antonelli.pdf

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214 8. Interaction Control of UVMSs<br />

[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 />

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

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

unexpected impact<br />

derwater manipulation are presented. These force control schemes exploit<br />

the system redundancy by using atask-priority based inverse kinematics algorithm<br />

[78]. This approach allows us to satisfy various secondary criteria<br />

while controlling the contact force. Both these force control schemes require<br />

separate motion control schemes which can be chosen tosuit the objective<br />

without affecting the performance of the force control. The possible occurrence<br />

ofloss of contact due to vehicle movement isalso analyzed. The proposed<br />

control schemes have extensively been tested in numerical simulation<br />

runs; the results obtained in acase study are reported to illustrate their<br />

performance.<br />

Two different versions of the scheme are implemented based on different<br />

projections ofthe force error from the task space to the vehicle/joint space.

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