Dynamical Behavior And Robust Control Strategies Of The Underwater Gliders

The Underwater Gliders are a new kind of Autonomous Underwater Vehicles. They show more and more potential and have important roles in ocean exploring and ocean measurement. This is because these vehicles have long onsite time, a wide cruise range and less power consumption. Nowadays the scientists pay more attention to the Underwater Gliders. Based on the driven power they use, the Underwater Gliders are divided into two kinds: Underwater Gliders are driven by electric power and Underwater Gliders are driven by temperature difference energy. The Underwater Gliders driven by temperature difference energy have less power consumption, longer on site time and are less noisy when operating underwater.A new kind of Underwater Glider driven by temperature difference energy is developed in this dissertation. Lake trials of the Glider show that the functions and performances of the glider are coincident with the design goals. The dynamic model and controller of the Underwater Glider have been developed to the point where they can be used to analyze the behavior and to decide the design parameters of the glider. The following contributions have been made.1. The first underwater glider driven by temperature difference energy in China has been developed. The model harvests energy from the difference of ocean temperature between surface and bottom to change the buoyancy. This enables it to dive and climb in the water. The pose of the glider is adjusted by the rotating of an eccentric column mass and the translation of a coaxial column mass in the pressure hull of the glider.2. Dynamic model of the underwater glider is formulated using the Gibbs– Appell Equations. Considering the simultaneous effects of the eccentric rotating mass and the translation mass, the model can show exactly the dynamic behavior of the glider and can be used to other similar AUV dynamic analysis. The performances of the glider in 3-D and in the vertical plane are studied based on the model. The relationship between design parameters and performance is analyzed. The velocity range, pitch angle range and relative design parameters are decided using the dynamic model.3. The Linear Quadratic Regulator is designed in this dissertation. Simulations in the vertical plane of the feedback control system are analyzed. The noise rejection and tracking ability to the input reference are studied.4. Considering the parameter uncertainty of the glider system, the uncertainty model is derived. The H infinity controller is designed and the nominal stability, nominal performance, robust stability and robust performance of the glider system are analyzed. The range of the parameter perturbations are decided as well. The simulation shows that the underwater glider with the H infinity controller can ride robustly even with the parameter perturbations.