Robust Control System Design for a Towed Underwater Vehicle

A0088 Hiroyuki Kajiwara Department of Maritime Engineering, Kyushu University

A0089 W. Koterayama RIAM, Kyushu University

A0090 S. Yamaguchi RIAM, Kyushu University

A0111 T. Yokobiki RIAM, Kyushu University

We are concerned with a towed underwater vehicle named Flying Fish,

which has several kinds of instruments to measure environmental data

in the sea. We need to design a control system of Flying Fish in

order to change the depth regulating the pitch against the disturbance

due to the mother ship oscillation. Flying Fish equips with a main

blade and a tail blade, which should be manipulated to control the

depth and the pitch respectively. A simple control strategy is using

two PID controllers for the main-blade-to-depth loop and the tail-

blade-to-pitch loop independently. But the mother ship would adjust

its forward velocity for collision avoidance. In that case, the PID

control strategy would not be successful because of variations in

hydrodynamic forces. Therefore there is a strong motivation to design

multivariable controllers of Flying Fish taking account of its

velocity variation.

We will apply an LPV control strategy to the above problem. Firstly,

in order to capture the dynamics variation, we construct a LPV (Linear

Parameter Varying) model of Flying Fish given a range of velocity

variation. Secondly, we design its LPV controller solving an

optimization problem subject to LMIs (Linear Matrix Inequalities)

constraints corresponding to closed-loop specifications. Thirdly, we

show experimental results of LPV controls designed. Finally we

conclude with several remarks.