Experimental investigation on a cabin-suspended catamaran in terms of motion reduction and wave energy harvesting by means of a semi-active motion control system. (February 2019)

• Record Type: Journal Article
• Authors: Han, Jialin; Kitazawa, Daisuke; Kinoshita, Takeshi; Maeda, Teruo; Itakura, Hiroshi
• Is Part Of: Applied ocean research. Volume 83(2019)
• Page Start: 88
• Page End: 102
• Publication Date: 2019-02
• Subjects: Catamaran -- Semi-active motion control -- Suspension system -- Ride comfort -- Wave energy harvesting; Ocean engineering -- Periodicals; 620.416205
• DOI: 10.1016/j.apor.2018.12.003
• Languages: English
• ISSNs: 0141-1187

Abstract

Highlights: A cabin-suspended catamaran is proposed, and a series of model tests is implemented. Owing to the expansion and contraction movement of the suspensions, the motion of the cabin is separated from that of the twin-hull. A semi-active motion control system is developed with the aim of harvesting wave energy under the condition of suppressing the heave and/or pitch of the cabin at the most. The motion reduction ratios of the cabin and the wave energy capture width ratios under five control scenarios and two reference scenarios are analyzed and investigated. Suggestions for the parameter selection of the control system are given to improve the effectiveness of the system. Abstract: A novel concept catamaran equipped with a suspended cabin, named Wave Harmonizer Type 4 (WHzer-4), is proposed and evaluated. The mass-spring-mass system is constructed by mounting four sets of suspensions in-between the cabin and the twin-hull. Two sets of dual motor/generators (M/Gs) are attached on the center beam of the cabin's deck fore and aft. Each shaft-end of the dual M/Gs is connected to the twin-hull through a rack-pinion gear unit. In this way the vertical relative motion between the cabin and the twin-hull can be transferred into the rotational motion of the M/Gs, and vice versa. A semi-active motion control system, which contains a proportional-integral (PI) controller, is designed and applied to each of the dual M/Gs for the aim of absorbing wave energy under the condition of suppressing the local vertical velocity of the cabin as much as possible. A 1/5 scale model ship with a length of 1.6 m is built, and a forced-oscillation bench test is implemented to validate the performance of the control system. Then, a series of towing tank tests is carried out in regular head waves. The heave and pitch responses of the cabin, those of the twin-hull and the corresponding wave energy capture width ratio (CWR) at five control scenarios and two reference scenarios are investigated. Discussion on the results of the tank test shows that the motion reduction of the cabin and the wave energy harvesting can be achieved simultaneously at a few wave conditions. However, at other conditions, although noticeable amount of wave energy is harvested, motion reduction of the heave and pitch of the cabin could not be obtained at the same time. It is suggested that varying the gain settings of the PI controllers according to the location of the controllers may improve the effectiveness of the proposed control system.