Real-Time Simulation and Virtual Reality Techniques in the Design Process of Planing Craft Propulsion Systems

摘要

The paper describes the main features of a planing craft simulator, developed by using Real-Time simulation and Virtual Reality techniques. In the last years several studies about the dynamic behaviour of marine propulsion systems have been carried out at Genoa University but now in this study the interaction among ship motions, manoeuvrability aspects and propulsion system dynamics are integrated in one mathematical model. In particular, the presented simulator is referred to a waterjet propelled boat, of which the main propulsive characteristics, as craft velocity, trajectories, trim and heel angle, rise, propulsor thrust, engine power and speed are predicted as consequence of the variation of throttle lever position and waterjet steering device angle. The aim of the work is the realisation of a complete propulsion simulator to be used in the design process of the boat and for training purposes. The latter objective needs a proper visualization in order to extend the capability of the used software (Matlab-Simulink) to the virtual reality world. A 3-D graphics model has been created by using a Virtual Reality Editor, in order to represent the three dimensions viewing of the boat in a virtual scenario; the visualization from the pilot's perspective is also displayed on a large screen. Generally simulation time is not real (watch time) but it depends on computer memory, CPU speed, simulation step, ordinary differential equations solver (ODE) and model stiffness. The dynamic system simulation has to be performed in real time for training purposes but unfortunately the common PC operative systems do not work in real time; therefore, in order to overcome this problem, the Real-Time Windows Target (a MathWorks software package) has been used to ensure the real-time application. The virtual interaction with the dynamic model is obtained by means of a joystick/throttle, linked to the PC in order to power and steer the boat.