Underwater Robots - Gianluca Antonelli.pdf

96 5. Experiments Dynamic Control of a6-DOF AUV
The following control gains have been used:
Λ =diag{ 0 . 5 , 0 . 5 , 0 . 15, 0 . 8 , 0 . 8 , 0 . 8 } ,
K D =diag{ 12, 12, 5 , 2 , 2 , 8 } ,
k p =1,
k o =1,
K θ =blockdiag { 0 . 01, 0 . 3 I 3 }
In Figure 5.3 the time history of the position of the vehicle in the inertial
frame and the attitude of the vehicle and the orientation error interms of
the Euler angles is shown. Notice that, due totechnical characteristics of the
horizontal sonars [215], the x and y position data for the first 100s are not
available.The vehicle is notcontrolled in those directions andsubjectedtothe
pool’scurrent. At t =100 s, it recovers the desiredposition andstarts tracking
the trajectory. Inthe first seconds the vehicle does not track the desired
depth. This is based on the assumption that all the dynamic parameters
are unknown; at the beginning, thus, the action ofthe adaptation has tobe
waited. From this plots it is also possible to appreciate the different noise
characteristics of the two position sensors: the sonar for the horizontal plane
and the pressure sensor for the depth. It can be noticed that the desired
attitude is kept for the overall length of the experiment and that asmall
coupling can be seen when, at t = 100 sthe vehicle recovers the desired
position in the horizontal plane.