Underwater Robots - Gianluca Antonelli.pdf

182 7. Dynamic Control of UVMSs
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Fig. 7.20. Output feedback control; third case study. Comparison between
the control laws (7.43),(7.44) and (7.63): vehicle control moments. Left: control
law (7.43),(7.44). Right: control law (7.63)
is exploited to decompose the overall motion control problem inaset of elementary
control problems regarding the motion ofeach rigid body in the
system, namely the manipulator’s links and the vehicle. For each body, a
control action isdesigned to assign the desired motion, toadaptively compensate
for the body dynamics, and to counteract force/moment exchanged
with its neighborhoods along the chain.
The resulting control scheme has amodular structure which greatly simplifies
its application to systems with alarge number of links; furthermore, it
reduces the required computational burden by replacing onehigh-dimensional
problem with many low-dimensional ones; finally itallows efficient implementation
ondistributed computing architecture; itcan be embedded in a
kinematic control scheme, which allows handling of kinematic redundancy,
i.e., to achieve joint limits avoidance and dexterity optimization; finally, it
reduces the size of the control software code and improves its flexibility, i.e.,
its structure isnot modified bychanging the system’s mechanical structure.
Remarkably, the control law is expressed in terms of body-fixed coordinates
soastoovercome the occurrence of kinematic singularities. Moreover,
anon-minimal representation of the orientation —i.e., the unit quater-