A simply Swedish ship movement sensor

Simplicity is a virtue when designing a new product. It is of particular importance when trying to correlate the complex movements of a ship at sea with the resultant data this produces in a user-friendly manner. Transformator, based in Varberg, Sweden, has developed a simple and low-cost dynamic ship movement controller system to do just this. The system is able to measure and monitor the motion of a ship. It measures the amount of pitch and roll. It also keeps track of the rate of acceleration in three directions, i.e. pitch, roll and vertical motion. In addition, it can measure torsion and deflection of the hull. Mental pressure and stress are increasing as modern ships become larger and faster, turnarounds get faster and crew numbers shrink. The result is more mistakes and more accidents. Technology has come to the aid of seafarers in the shape of hardware and software for navigation and engine room performance monitoring. But there are relatively few systems available giving information on the effect weather and sea conditions have on ships and their cargoes. Transformator?s solution consists of six gravitational field sensors in a single Aqua Control sensor unit. Analysis of angle changes and the time taken for the angle changes makes it possible to establish the movement speed and angles in all co-ordinates. The sensor unit is usually mounted in the forepart of the vessel. It is linked by cable to a computer on the bridge. This gives a visual real-time display and provides analysis of the ship?s motions at sea or in port. This can be used to calculate the relationship between the centre of gravity and the metacenter. At least two sensor units are required if a shipowner wants to measure the torsion and hull stresses, one mounted in the bow and the other towards the stern. It is possible to estimate the forces on containers and their lashings by measuring the angle and period of roll and pitch together with 3D acceleration. Graphic analysis of all historic movements can be recorded over a period of up to 30 days. But the primary function of the sensor unit is to give predictive sea-state information. The data from the movement sensors is transformed into easily understandable graphics that the ship?s officer of the watch can use to optimise vessel performance in terms of speed and course. This ensures improved sea keeping in all weather conditions. An audible and visual alarm is triggered when pre-set alarm levels are reached. The sensor units measure about 6cm across and 5cm high. They are cast in epoxy plastic while the housing is made from stainless steel to prevent water damage. Tranformator recommends the units should be further encased in a splash-proof box. Installation involves mounting the sensor unit on a horizontal steel plate close to the centre-line of the ship. The unit is connected to an IBM compatible PC via a leaded cable. It is subsequently calibrated to obtain the zero position. Competing companies and products include the UK-based HR Wallingford Ship Movement Measurement System, which uses laser displacement sensors, StressAlert II hull stress monitoring system supplied by Strainstall in the UK and SAJ Instrument AB in Mariehamn, Finland. Tranformator has already supplied some 25 units to European shipowners. Those looking to follow these companies lead will have to invest about $15,000 per unit. This includes software, cabling and fitting. The company says the system is relatively easy to maintain and service.