Ship and vehicle hydrodynamic models and automatic control
Calculations of the behavior of ships and marine vehicles in a sea environment requires knowledge about the hydrodynamic models of the vessels as well as accurate models of propulsion systems, rudders and other means of controlling the vessel. This knowledge, combined with our automatic control expertise, enables us to offer a wide range of possibilities for development of simulation services and products.
Vessel hydrodynamic models
The hydrodynamic models of the vessel can include the effects related to manouevring of the vessel, including effects of varying topography. For a vessel moving in waves the effects on all 6 degrees of freedom of the vessel must be considered. The models can be established through model tests, theoretical calculations, or combinations of these. Through years of model testing experience and development of computer codes for vessels from zero speed to high speeds, MARINTEK has developed a solid basis for establishing hydrodynamic models.
Control forces
Control forces on a vessel can include effects of rudders, propulsion units such as propellers, thrusters, pods and waterjets, roll stabilizing fins, T-foils, interceptors and so on. In addition, internal devices such as roll damping tanks are important effects to include when modeling the ships behaviour at sea. This is true both for model tests and theoretical calculations. Our calculation tools can include effects from all such devices. During model tests, we can also include these effects, and we have good experience with operating free running models with autopilot steering and active motion control systems.
Automatic control
MARINTEK has developed a real-time control system for our laboratories based on the latest technology in rapid control prototyping. The control software is developed in a graphical environment and is compiled and downloaded into the ship models automatically. The following controllers/functions have been developed:
- Autopilots (course- and track-keeping)
- Ride control
- Motion damping
- Stationkeeping and way-point tracking control
- Joystick control
The control software is first tested in a simulation environment (software-in-the-loop testing) where numerical ship models and sensors models are used to verify the control software. Later on, the actual hardware (hardware-in-the-loop testing) can be used in the simulator to create the correct user interface and finally the control software is either downloaded to a model ship or into a full scale application.