Underwater Robots - Gianluca Antonelli.pdf

144 7. Dynamic Control of UVMSs
is obtained by adding to the vehicle thrusters afeedforward compensation
term that is an estimate of τ m :
τ v = τ control + ˆτ m ( R I B , q , ζ , ˙ ζ ) (7.2)
where τ control ∈ IR 6 is the control actionoutput by the sole vehicle controller.
In [206] thereare experimentalresults conducted with the vehicle OTTER
that isabout 2 . 5m long, 0 . 95 mwide, and 0 . 45 mtall and weights about
145kginair. The arm used has a7. 1cmdiameter and is 1m long. The control
benefits from avariety of commercial sensors: an acoustic short-baseline
for the horizontal position, apressure transducer for the depth, adual-axis
inclinometer for the roll and pitch angles, aflux-gate compass for the yaw,
and solid-state gyros for the angular velocities. The control loop has been
implemented at afrequency of100 Hz, i.e., the frequency of all the sensors
expect the baseline acoustic that worked at 2 . 5Hz.
˜η ee1 [m]
˜η ee1 [m]
0.5
0.4
0.3
0.2
0.1
0
0 5 10 15 20
time [s]
Decoupling Control Only
0.5
0.4
0.3
0.2
0.1
No Vehicle Control
0
0 5 10 15 20
time [s]
˜η ee1 [m]
˜η ee1 [m]
0.5
0.4
0.3
0.2
0.1
0
0 5 10 15 20
time [s]
Feedback with Decoupling Control
0.5
0.4
0.3
0.2
0.1
Feedback Control Only
0
0 5 10 15 20
time [s]
Fig. 7.2. Feedforward Decoupling control. End-effector errors of aperiodic motion.
Top-left: without vehiclecontrol; top-right: with the sole decoupling action; bottomleft:
with the sole vehicle feedback control; bottom-right: the proposed approach
(courtesy of T. McLain, Brigham Young University)