DNV Class Approved Electronic Control System specifically for Wind Farm Support Vessels
29/04/2012 - Category: Rotec-News
Working closely in a partnership with two major British manufacturers, Rotec Hydraulics has developed, manufactured and installed a bespoke electronic propulsion control system for new vessels working in this rapidly developing market.
Ultra Dynamics Ltd are a major manufacturer of water-jet propulsion technology. They were selected to supply water-jets to Southboats Special Projects, on the IOW who themselves are the largest British manufacturer of wind farm support vessels. These vessels are designed to transit to and from off-shore wind farms to transfer maintenance crews onto the towers. As this can be a difficult and often hazardous operation, it is essential that the vessels used must have a high degree of manoeuvrability and are highly responsive to the skipper’s commands in difficult seas. Water-jet propulsion technology is therefore the preferred choice for these vessels.
Rotec were approached by Ultra Dynamics to develop a bespoke electronic control system for the application based on the requirements for a reliable, robust and adaptable system for the working environment. In addition, the finished system had to be easy to install and simple to set up and commission.
With our experience and knowledge gained from extensive use of the hardware and application development software, Parker Hannifin’s ‘Iqan’ modular control equipment was the obvious choice for this application. The equipment was originally designed for the mobile equipment markets (forestry vehicles in Scandinavia) so was easily able to migrate to the marine environment. It is a fully programmable modular networked system using CANbus communication to interconnect the various control elements of the system to the central controller. This greatly reduces the interconnecting cabling types and amounts required and thus the installation costs.
The system was designed and manufactured to a specification agreed between the three parties and essentially controls the water-jets, engines and gearboxes. These vessels are all catamaran design so two propulsion trains are controlled synchronously, fully electronically.
A particular specification for this project was the requirement for the system to comply with DNV class. This essentially requires that the system is fully dual redundant. To comply with this requirement, all hardware and interconnecting CANbus cabling is completely duplicated. Essentially there are two fully independent full control systems either one being selectable by the skipper. The non active system still displays all required data but is only functional at the turn of a selection switch. The identical wheelhouse main controllers feature full colour 6inch TFT screens with function keys selecting the various operating screens developed for the application.
In a traditional water-jet propulsion set-up using three control heads, twin lever control heads are used for the engine speed controls and another set for the water-jet reverse deflectors position control. A single axis joystick is used to control steering. Modern practice is now to control the vessel using only two joysticks, again a single one for steering, but now with a two axis, one to provide control of reversing deflectors and engine speed control from a single unit. Either option can be fitted to either control system at any time of the vessel’s life to enable the user to choose the ideal set-up for his skipper based on their preferred choice and experience. Control heads are fully interchangeable and plugged for simple exchange.
The water-jet steering and direction actuators control valves are fully electronic proportional type giving smooth control of the movements with no excessive harsh banging often seen on non-proportional water-jet set-ups.
The system communicates directly to any engine ECU unit over the standardised J1939 protocol. Once set up, the system controls engines’ speeds demands and measures actual speeds. It is also possible to read and write to any of the engine parameters as an option if required. For non-J1939 enabled engines, CANopen and/or analogue control is used to provide a suitable engine demand from the system.
Additional features of the system include the following: interfacing to the vessel’s autopilot system, trim steering tabs system, and supervisory SCAMS system. Calibration facilities for all controller head and feedback encoders are available to the user via intuitive screens and finally the screens and all operation LED indicators are dimmable for night use.
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