7.4 Development of Ride Control System for JETPIERCER4)
Kawasaki Heavy Industries, Ltd. Have developed the Ride Control System (RCS) in order to enhance excellent seakeeping performance for JETPIERCER, a wave piercing catamaran highspeed car ferry. The first vessel of her was named "Hayabusa" (falcon) with length of 99.78 m, width of 19.98 m, depth of 7.30 m, weight of 2,282 ton, cargo weight of 570 ton, maximum speed of 35.5 knots, and carrying capacity of 460 passengers with either 94 cars or 32 eight-ton trucks. She has 4 water jet propulsion systems driven by 4 high speed diesel engines of total 25,780 PS (18,961 kW).
RCS decreases a ship motion which is introduced by wave making force because of high speed vessel herself, by the fins installed on the bow and the trim tabs on the stem of her catamaran. It enhances excellent seakeeping performance for her. The lifting power produced by these fins and trim tabs is used actively as force to control pitch and roll motion of her. RCS consists of ship motion sensors (rate-gyroscope), a main microcomputer-based controller, hydraulic power units and driving units for the fins and the trim tabs. Fig. 7.4 shows the arrangement of the system.
The rate gyroscope detects rolling and pitching acceleration of the vessel. Under the results of detection, the main controller calculates angle of the fins and the trim tabs to produce lifting power which prevents the vessel from leaning over. It gives instructions to each actuator of the driving unit to reduce wave-induced pitch and roll motion. As a result of numerical simulation of RCS and model experiment in a water tank, the following was known.
If the fins and the trim tabs would be controlled as mentioned above under wave length in which the oscillation of the vessel becomes the maximum, the oscillation will decrease about 20%. RCS modified on basis of this result was installed on actual vessel, and anti-motion effects was examined. As a result, under head sea pitch rate decreases about 65% and up-and-down acceleration decreases about 57% in operation of RCS than in no operation. When the vessel was running commercially, under beam sea pitching rate decreases about 47% and up-and-down acceleration decreases about 36% in operation of RCS than in no operation.
Fig. 7.4 Arrangement of RCS Components
