Current control system for fully-submerged hydrofoil based on optimal feedback control has several problems, such as it has no good performance of contouring waves and it cannot reduce the effect of wave disturbance. In this paper, the longitudinal control system for fully-submerged hydrofoil based on optimal preview servo system was proposed to settle the problems of current control system. The proposed control system is composed of feedback control input and feedforward control input which are calculated by using future information of reference input and wave disturbance. And also, in order to design the proposed control system, the necessary prediction range of future information and the weight function in performance index are determined. Finally the validity of the proposed control system is confirmed by simulation. The research results show that the proposed control system has good performance of contouring waves in the follow sea and reduce the effect of wave disturbance. And also the research results show that the proposed control system is effective to settle the problems of current control system for fully-submerged hydrofoil.
Fully-submerged hydrofoil is essentially configured to provide good ride quality and speed performance since it is free from water (Weist and Mitchell, 1976). And the control system is efficient to stabilize or to argument stability of the hydrofoil. The current automatic control system (ACS) of hydrofoil is designed by optimal feedback gain theory, inertial sensor signals and ultrasonic sensor signals. And this includes platform and contour mode selection and manual input of fore foil depth by human operator. The contour mode is to keep foil depth in waves to avoid cresting and exposing of foil. And the manual input of fore foil depth is performed to strengthen contouring waves (Saito and Kuroi, 1989; Saito and Ikebuchi, 1990).