Research On Underwater Glider Dynamic Modeling, Motion Analysis And Controller Design In Currents

Due to their low-noise, low-cost and durable-endurance, underwater gliders working as efficient mobile sensor platforms, have broad application prospects in ocean monitoring, exploring and detection, for both civilian and military purposes. The theory and application study on underwater glider has important significance.In order to understand the dynamics of underwater glider comprehensively, this dissertation researches on the dynamic modeling of underwater glider. Based on the model, the relationship between geometric characteristics and performance and stability is analyzed, which can provide guidelines for the design work. Considering that glider motion suffers in currents, glider dynamics in currents is modeled here, based on which, the effects of currents on glider motion are investigated; controller and observer for motion control and flow estimation are also designed, respectively. Field and simulation trials are carried on the prototype of ZJU Glider, which validate the theoretical studies in this dissertation preliminarily. The research points are concluded as follows:Based on Newton-Euler equations, the multi-body dynamic model for a glider with a cylindrically actuated moving mass has been fully derived by establishing a particle frame. Besides, the multi-body dynamic model for a glider with rectilinearly actuated moving mass and a rudder has also been presented, which is prepared for the perfoemance and stability analysis of ZJU Glider. Based on Lagrange equations and the concept of ’quasicoordinates’, this dissertation has also derived the multi-body dynamic model for a glider in currents, which is used for glider motion prediction, controller and observer design.Referring to aircraft theory, the geometric characteristics of glider has been defined parametrically. The dissertation has discussed the hydrodynamic model of underwater glider. The viscous and inviscid coefficients of ZJU Glider have been obtained by computational fluid dynamics (CFD) method and analytical method, respectively. Using glider dynamic model and hydrodynamic model, this dissertation has analyzed the steady motions of glider longitudinal and turning flight and investigated the effects of geometric parameters on the performance and stability of glider motion, aiming to provide guidelines for vehicle design. To illustrate the utility of glider dynamic model in currents, numerical motion predictions are compared with those of simpler models for a variety of nonuniform flow fields.The feedback/feedforward controller for glider attitude control has been designed. These feedforward parameter values are determined using a numerical trim solver. The performance of motion controller for glider attitude control both in still water and specific currents has been validated numerically. Furthermore, the effective downstream motion control method has been presented, thus the range of the glider flight can be increased highly with the help of currents. Taken the flow gradient as disturbance, Luenberger state observer has been designed based on the augmented linearized model, which achieves effective estimation of flow gradient.Taken theoretical analysis results as reference, the200m-depth prototype of ZJU Glider has been developed. The trial results indicate that ZJU Glider functions well in water and it is capable of serving as a sensor platform for ocean sampling. Simulation trial has also been carried on ZJU Glider to validate the presented downstream motion control method preliminarily.In summary, the dissertation carries out systematic study on glider dynamic modeling, performance and stability analysis. The research on glider dynamics in currents, motion controller and flow characteristics observer design are also explored, which lays a solid foundation for the further theoretical and applied study.