Abstract

This paper describes work involving the further development and refinement of a mathematical model of an unmanned underwater vehicle (UUV), together with the development of an associated real-time multi-rate simulation that includes both high-speed power electronic subsystems and slower components. The chosen vehicle uses a battery as its energy source and this feeds an a.c. motor drive through a d.c. to a.c. converter. The drive powers the vessel which is modelled as a six-degree of freedom vehicle with control surfaces. Tests carried out indicate that a careful choice of frame rates can increase the speed of solution by factors of several hundred over solution times when the shortest frame rate is used throughout. These multi-rate solutions were executed faster than real time on a typical laptop even when using 3-D graphical output for visualisation of vehicle motion. The conclusions of the paper are that the modelling and simulation of the UUV has provided a useful test-bed for ideas on multi-rate simulation and has demonstrated that multi-rate real-time simulation is feasible and useful for an application of this kind that includes very fast power electronic subsystems and relatively slow systems such as the vehicle and battery.