Stability Control And Path Planning For Hybrid-driven Underwater Gliders

Hybrid-driven Underwater Glider(HUG)is a new type of unmanned underwater vehicle which combines the advantages of traditional underwater gliders and autonomous underwater vehicles.Traditional underwater gliders are highlighted by low power consumption,long voyage,long endurance and good stealth characteristics,while autonomous underwater vehicles have good maneuverability and can travel with a high speed.Thus the HUGs have been widely used in marine scientific research and marine environmental observation.The research on the stability control and path planning is of theoretical and practical significance to controlling and mission planning for the HUGs.This dissertation presents dynamic modeling of Petrel HUG,which is developed by Tianjin University,based on multibody theory.Analysis of kinetic stability and estimation of attraction region for Petrel HUG are also presented.Then a linear and a nonlinear controller are respectively designed in the vertical plane for both gliding mode and hybrid-driven mode.Stabilities of the two controllers are proved.Finally,a path planning method for the HUG is proposed for actual tasks in practice.The main contributions of this thesis are summarized as follows:1.A dynamic model of Petrel HUG is established based on multibody theory.This model includes the position and mass of each unit of the HUG,as well as the hydrodynamic characteristics and can be used to other similar underwater vehicles dynamic analysis.As a result,the effect of each unit on the overall dynamic behaviors is reflected more realistically.Simulation results of the spiral motion in the gliding and hybrid-driven modes provide guidance to actual course control.2.Based on singular perturbation theory,the state variables of Petrel HUG are divided into sub-states,namely quick states and slow states.According to the fact that the stability of the two subsystems composed of sub-states is proved,the stability of Petrel HUG in the vertical plane is proved by establishing a composite Lyapunov function.Then the attraction regions of Petrel HUG are also estimated in two different working modes.3.A nonlinear controller of Petrel HUG is designed in the longitudinal plane by combining the nonlinear dynamic inverse method,the backstepping method and the Lyapunov function method.The closed-loop subsystems can be therefore exponentially stabilized.The strategy of mode switching is also studied.Through the simulation analysis,it is proved that the switch between the two modes is feasible and the process can be stable.4.Considering the strength of sea currents,a new path planning method is proposed for Petrel HUG based on the differential evolution algorithm and Zermelo optimal navigation criterion.The problems of path planning are solved for two practical situations as between point to point and in the constrained corridor space.Simulation results show that the proposed path planning method can generate a three-dimensional path for Petrel HUG in the two cases,which is of great guiding significance to practical mission path planning for the HUG.