06.02.2013 Views

Underwater Robots - Gianluca Antonelli.pdf

Underwater Robots - Gianluca Antonelli.pdf

Underwater Robots - Gianluca Antonelli.pdf

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

7.6 Sliding Mode Control 155<br />

Practical implementation of (7.10), therefore, requiresreplacementofthe sign<br />

function, e.g., with the sat function<br />

u = B † [ K D s + ˆg ( q , R B I )+K S sat(s ,ε)] , (7.21)<br />

where the sat(x ,ε)isthe vector function whose i -th component is<br />

⎧<br />

⎨ 1 ifxi >ε<br />

sat(x ,ε) i = − 1<br />

⎩ x i<br />

ε<br />

ifxi < − ε<br />

otherwise.<br />

Convergence tothe equilibrium of the UVMS under this different control<br />

law can be easily demonstrated starting from (7.12) following the guidelines<br />

in [268]. In detail, it is obtained that ˙ V < 0inthe region characterized<br />

by � s � ≥ ε ,while the sign of ˙ V is undetermined in the boundary layer<br />

characterized by � s �

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!