Ship has an automatic pilot linked via a roll motion sensor system to a main upper rudder and a secondary lower rudder

摘要

A ship has an automatic pilot linked via a motion sensor system to a main upper rudder and a secondary lower rudder. The main upper rudder is primarily responsible for maintaining the track while the lower rudder is used primarily to dampen roll. The dampening action is supported by e.g. a jet, a supplementary fin or tab.