Spare a thought for the well-heeled owners of luxury yachts. Their lifestyle may look idyllic, but add choppy water to all that gin and rich food – and the dream can soon turn into an ugly appointment with a toilet bowl.
However, thanks to an innovative anti-rolling mechanism based on the operating principle of the gyroscope, passengers may soon be enjoying unprecedented levels of comfort.
Developed by engineers at Japan’s Mitsubishi Heavy Industries (MHI), the ARG (anti-rolling gyro) system applies the operating principle of the control momentum gyroscope (CMG) to suppress a boat’s rolling motion – the main cause of seasickness – by more than 50 per cent. The system, soon to make its debut on vessels designed by Italian luxury yacht-maker Ferretti, is based on technology developed by MHI for the Japanese space programme for use on the International Space Station, said a company spokesman.
ARG is essentially a large gyroscope consisting of a motor-driven flywheel supported by a gimbal mechanism. The high-speed rotation of the flywheel produces force to counter rolling motion. The flywheel spins at high speed around a vertical axis, and is mounted so that it has to roll from side to side at the same rate as the boat. When the boat starts to roll the spinning flywheel converts the motion into torque, causing the flywheel mechanism to spin on its gimbals. The rotation of the flywheel about its gimbals creates an anti-rolling torque, which reduces the boat’s rolling motion.
Although other devices that reduce rolling do exist – fin stabilisers, for example – ARG is the first system in the world capable of reducing the rolling of a small boat even when anchored, said the spokesman. This, coupled with its quiet operation, means that the device can be used during the night to give passengers a comfortable night’s sleep. It is thought that the system’s stability may also lead to its uptake by coastguards and police for sea-based surveillance operations.
The system does have its limitations, however. In particularly extreme conditions it automatically switches off to prevent damage to the motors. Plus, while the effect can be scaled up for larger vessels by installing multiple units, the system is ineffective on ships with a natural roll period of more than seven seconds.
This is a measurement of the time it takes for a boat to rock from one extreme to another and back. The measurement is roughly equivalent to a boat’s beam length in yards. So a cruise ship with beam length of 30 yards will have a natural period of 30 seconds and will be an unsuitable candidate for the ARG system.
The technology upon which ARG is based is yet to make its appearance on the ISS, and when it does it won’t be the first time gyroscopes have been used in space applications. For instance, CMGs manufactured by Honeywell are frequently used on satellites, where the tendency of the gyroscope to remain in a fixed orientation in space allows it to hold the satellite in the correct position.
MHI’s spokesman explained that while the operating principles of such systems are similar to the ARG, the zero gravity and vacuum conditions experienced by satellites mean that CMGs don’t have to be as large as on a boat to control a satellite’s position.