DESIGN OF RIDE CONTROL-SYSTEM FOR SURFACE EFFECT SHIPS USING DISSIPATIVE CONTROL

A ride control system for active damping of heave and pitch accelerati ons of surface effect ships (SES) is presented. It is demonstrated tha t distributed effects that are a result of spatially varying pressure in the air cushion result in significant vertical vibrations in low an d moderate sea states. In order to achieve high quality human comfort and crew workability it is necessary to damp these vibrations using a control system which accounts for distributed effects owing to spatial pressure variations in the air cushion. To develop such a ride contro l system a mathematical model describing the motion of the craft in th e vertical plane is derived. This mathematical model accounts for acce lerations induced by both the dynamic uniform and the spatially varyin g air cushion pressure. Sensor and actuator placement is discussed, an d the stability of the control system is analysed using the theory of passivity. The performance of the ride control system is shown by powe r spectra of the vertical accelerations and the pressure variations ob tained from full-scale experiments with a 35 m SES.