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UBC Theses and Dissertations

The dynamics and control of an underwater towed vehicle Hopkin, David A.


A linear, quadratic optimum control strategy is applied to a non-linear dynamic model of an underwater towed vehicle in an effort to minimize the pitching motion of the vehicle during the tracking of a reference input. The dynamic model is a two-dimensional, coupled pitch/heave model. The cable interactions with the vehicle are simplified to steady state, and formed into a multi-variable look-up table used in the non-linear model. The normal force resulting from the body of the vehicle is non-linear and consists of two components, an invisid slender-body theory component, and a separated crossflow component. In addition, the dynamic model includes the non-linear effect of the front airfoil's downwash acting upon the rear airfoils. Aerodynamic testing of a scaled vehicle provides the expressions for the non-linear normal body force and moment. These tests also verify the finite aspect ratio corrections for the airfoils, and the downwash effects of the front airfoils. The linear control strategy is based on linear, quadratic optimum control. Simulation results show that proper selection of the state and input weighting matrices result in minimizing the pitch angle of the vehicle to within the control objectives. In addition, simulations of various observer designs show how the tracking and attitude control varies with the selected measurements.

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