Simulation of an Unmanned Underwater Vehicle (UUV): A Multi-Rate Simulation
John J. Zenor, Richard Bednar, Dale Word, Roy E. Crosbie, Narian G. Hingorani, Euan McGookin and Roger Dougal
Summer Computer Simulation Conference 2007 (SCSC 2007)
San Diego, California (USA), July 15-18, 2007
Abstract
The problem of developing real-time simulations that include both high-speed (<10 μs frame time) and lower speed components can be alleviated by means of multi-rate simulation. A collaborative project has been established between California State University, Chico, the University of South Carolina, and the University of Glasgow to develop a multi-rate demonstration example that includes a power electronic subsystem that requires high-speed simulation. The selected application is an unmanned underwater vehicle (UUV) that uses a battery as its energy source which feeds 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 three subsystems that are simulated with different frame rates. The converter (5 μs), the motor drive (100 μs) and the vessel and the battery (1 mS). The final goal is a real-time implementation but the initial effort aims to combine the three subsystems within a VTB environment using a new VTB multi-rate solver. Three different programming approaches are used for the three subsystems. The fast component is programmed using C++ code developed for high-speed real-time simulation at Chico. This code uses a wrapper to make it compatible with the VTB solver since the differential equation solver used in the Chico code is not directly compatible with the VTB. The model for the vessel is written in Matlab. The VTB has the capability to incorporate Matlab models into a VTB simulation.