Study On Motion Characteristics And Path Planning Of Underwater Glider

Underwater gliders are efficient underwater vehicles that can be used as an ocean observation platform for carrying various sensors to realize multi-target detection underwater.It is an important application for value in the field of marine research and military.The hull design and theoretical research of underwater gliders are of great significance.The underwater glider travels far in a large working range but its velocity is slow with a poor stability of the body.In addition,external environment distance such as the current will influence the stability and motion performance of gliders via the hydrodynamic action.Great control and path planning will further improve the motion performance of gliders and guarantee a stable operation for a long time.Discussing the hydrodynamic characteristics of gliders and revealing the impact of hydrodynamic force on glider motion can optimize the shape design of gliders and improve the control efficiency of motion.The dissertation aims to solve problems of stable motion and efficient path planning for gliders.Based on establishing a 6DOFs(six degrees of freedom)dynamic model,a stable switching on controlling glider attitudes by linear and nonlinear controllers has been designed;in terms of energy consumption in changing the heading,the optimal path of energy efficiency in three dimensional space has been reached based on the optimization theory;based on experimental studies on hydrodynamic characteristics of gliders,the impacts of hydrodynamic force on gliders have been analyzed;based on mathematical models,the design procedure for gliders has been obtained and an glider have been designed.In addition,the performance of gliders has been verified through theories and experiments.Through the work of this paper,stability control and path planning of low energy consumption for underwater gliders have been preliminarily achieved,providing reference for the research,development and practical application of glider models.Main researches have been completed as follows:Based on the Newton-Euler method,a 6DOFs dynamic model using an internal rotary mechanism to regulate the heading has been established with complete expressions.The equilibrium equations of three-dimensional steady-state spiral motion are obtained by restricting the system states to the steady values,and the two-dimensional steady state equations of motion in the vertical plane are further obtained by restricting the motion states in the vertical plane.The exact solution of the model is obtained by Particle Swarm Optimization(PSO),which can obtain the globally optimal solution,so as to overcome the defect that the ordinary numerical method is easy to fall into the local optimal solution when it is solved.Based on the acquired stable solutions,preliminary analyses have been carried out in two steady gliding states as zigzagging motion of vertical pitch and three-dimensional spiraling motion.Multiple program design of the motion controller is studied.Firstly,the LQR controller is designed to control the attitude switching process of the glider and the all states of the system is observed by a Kalman observer.Secondly,by using the input-output feedback linearization method,a pseudo-linear system with linear behavior between input and output is obtained,select the glide angle and velocity as the controlled target,a PID controller is designed to control the stability of controlled target changes.Thirdly,considering the complex internal dynamics of the underwater glider,it is easy to cause instability of motion.The nonlinear controller is designed based on the Lyapunov stability criterion to control the pitching angle switching process of the glider.Finally,considering the motion characteristics of the actuator,a position controller with time delay is designed,the controller takes the adjusting angle of the body as the control target,the position of the attitude adjusting mechanism as the control object,and the acceleration of the actuator as the direct control quantity,the control signal can be calculated without dynamic model,so that the black box control without the dynamics model is realized.The simulation results show that the control effect of each controller on glider angle and actuator position.Refer to the orbital transfer of satellites and based on the optimization theory,the optimal path of two-dimensional energy efficiency has been deduced for gliders when the range of movement for actuators has been restricted.The achieved optimal path consists of two types of arcs,namely the arc of minimum turning radius as well as the one of maximum turning radius.Geometric construction methods for the optimal path have been provided on the basis of theoretical research.Subsequently,the optimal path has been expanded to three-dimensional space when reasonable three-dimensional expansion methods have been respectively offered for low,moderate and high depths.Through simulation experiments,the differences between the optimal path and the traditional three-dimensional Dubins path have been comparatively analyzed and advantages of the optimal path for energy efficiency have been probed into.Experimental researches have been carried out on the hydrodynamic characteristics of gliders separately in terms of numerical calculation and tests.Based on the similarity theory,the force and moment of the 6DOFs dynamic model for an underwater glider have been tested in a wind tunnel.Test results thus have been used to study the hydrodynamic change regulations of gliders and to calibrate the numerical calculation results acquired by RNG k-?.In comparison with the numerical calculation results,the consistency of hydrodynamic force coefficient is preferable.Motion simulation results suggest that CFD calculation results can be applied to design prototypes and to study motion performance.Moreover,the impacts of CTD unit and propeller unit on the drag of glider have been studied through contrast tests whose analytic results have provided a reference for glider design and motion analysis.In order to quickly estimate the drag coefficient of the glider,based on the test data,the empirical formula for estimation the drag coefficient of the glider containing the Reynolds number is fitted.The empirical formula is suitable for the fast estimation of the drag in the design stage of the glider.Tacking the glider dynamic model as the design basis,using the glider experience parameters as the design assistant,a set of glider design method combined theory and experience is summarized,and the characteristics of parts of glider are analyzed and studied.First,based on the glider theory model,the design parameters of the buoyancy system and the attitude adjustment system are obtained from the steady-state motion.Second,from the perspective of airfoil design,the forms and characteristics of airfoils fitting for underwater gliders have been analyzed.Combined with the main hull shape of the classic glider,the shape of the glider with the best cost performance is obtained by numerical calculation and analysis of the shape of the three gliders.Third,based on the analysis,an underwater glider is developed,and the performance of the glider is verified by experimental studies in a lake.