Fast ferry vertical acceleration reduction using mixed sensitivity approach

Abstract

In the presence of random sea wave disturbances, the vertical motion attitude control has become a new research field in engineering since the ships and passengers safety issues grow with the rise of their speed. This paper deals with the use of a moving T-foil near the bow to counteract the effect of vertical forces induced by waves on pitch movement acceleration suffered by passengers of a fast ferry. A new approach of control law design is investigated using the H-infinity weighted mixed S/KS sensitivity control theory. A systematic design of weighting matrices for the H-infinity mixed sensitivity problem is presented in this paper which allows an appropriate achieving of the closed loop behavior. The success of an optimal mixed sensitivity robust control design mostly depends on the selection of appropriate weights used in the optimization process where rejection of the waves disturbances is the design objective. Thus, avoiding proposing and improving the passengers comfort at high speed. Finally, a mixed sensitivity problem is formulated and the control performance is verified by simulation. The results showed a good disturbance rejection in the presence of plant perturbations and guaranteed the effectiveness of the proposed optimal control approach to satisfy the desired reduction of vertical motions. Hence, the proposed H-infinity weighted mixed sensitivity controller can effectively reduce the affect of waves on the vertical-plane motion of the fast ferry.