Simulation of an unmanned underwater vehicle (UUV): a multi-rate simulation

The problem of developing real-time simulations that include both high-speed (<10 μS frame time) and slower components can be alleviated using multi-rate simulation. Collaboration between California State University, Chico; the University of South Carolina; and the University of Glasgow, aims to develop a multi-rate demonstration example that includes a power electronic subsystem requiring high-speed simulation. The selected application is an unmanned underwater vehicle (UUV) that uses a battery as its energy source feeding an a.c. motor drive through a d.c. to a.c. converter. The drive powers the vessel which is modeled as a 6-degree of freedom platform with control surfaces. The model separates the system into subsystems that are simulated with different frame rates: the converter (fast), its controller (fast medium) the motor drive (slow medium), and the vessel and the battery (slow). The initial effort aims to combine the subsystems within a VTB environment using a new VTB multi-rate solver. Three different programming approaches have been used for the subsystems. The converter and controller are programmed using C++ code developed for high-speed real-time simulation at Chico. The electric drive uses native VTB models and the model for the vessel is written in Matlab.