Research On Modeling And Homing Control Of Parafoil Systems In Complex Environments

Parafoil systems are a special type of flexible winged aircraft,which uses the ramair parafoil to provide the lift force.The perfect control and glide performance of the vehicle give rise to a wide application prospect in military,civil,aerospace and etc.The precise modeling and control of parafoil systems involves a number of areas and disciplines such as mathematics,mechanics,computer,and control.Thus,it is a very challenging task.The paper mainly focus on modeling and homing control of parafoil systems in wind and rain environments.Some new ideas and methods for dynamic modeling,homing trajectory planning,path following have been put forward and validated by the combination method of theoretical analysis,numerical simulation and airdrop experiment.The main innovations of this paper are shown as follows:(1)A novel modeling method,based on computational fluid dynamics to simulate a parafoil flying in rain and wind environments,is proposed.In this method,wind field is simulated by mesh velocity,rainfall is simulated by multiphase flow,and the attitude of parafoil is simulated by dynamic mesh.Then,the impacts of rain film,wind load,rain load and equivalent action points of wind and rain are introduced to fix the aerodynamic equations of the parafoil.Furthermore,an eight degree of freedom dynamic model of the parafoil system in the rain and wind environment is established on the basis of the revised aerodynamic equations.Altogether,our numerical results and air-drop experiments demonstrate that the established model is meaningful and efficient.(2)The optimal homing trajectory planning problem of parafoil systems is formulated into a class of optimal control problem.After a series of solutions such as normalization and parameterization of the control rate,the optimal control problem is solved by two different approaches.One is to treat the optimal homing trajectory planning problem as a kind of optimal control problem with constraints,and use a kind of genetic algorithm with elite strategy to solve it.The other is to regard the problem as a multi-objective optimization problem,and applies an improved non-dominated sorting genetic algorithm II to solve it directly by means of optimizing multi-objective functions simultaneously.Simulation results verify the feasibility of the two methods.(3)The classical multiphase homing trajectory design method of parafoil airdrop system is extended to the powered parafoil system.A multiphase homing trajectory planning scheme for parafoil systems in feasible and infeasible regions is proposed.The homing trajectory is divided into several stages according to the flight characteristics.Then,an improved quantum genetic algorithm is applied as a tool to optimize the design parameters of the homing trajectory.At last,the feasibility of the method is verified by simulation experiments.(4)According to the guidance-based path following concept,a two-dimentional trajectory tracking guidance law for parafoil airdrop systems and a three-dimentional trajectory tracking guidance law for powered parafoil system are proposed.Further,a horizontal trajectory tracking controller and altitude controller are designed based on active disturbance rejection control.In addition,the stability of the trajectory tracking controller for parafoil systems is analyzed.Furthermore,the Monte Carlo simulation technique is introduced for the robustness analysis with model parameter uncertainties and complex environmental interferences.Finally,we utilize the simulation method and airdrop experiments to evaluate the trajectory tracking control method in complex enviroments.(5)The fixed-point homing control of parafoil systems is regarded as a complete mission.Fixed-point homing is to control the parafoil system track the designed homing path and realize fixed-point and upwind landing.For fixed-point homing of powered parafoil systems in any airspace,we put forward a control method enables the vehicle complete the fixed-point homing mission in both feasible and infeasible regions.Aiming at fixed-point homing control of parafoil airdrop systems in large wind environments,we propose a homing control method,which is of great importance to improve homing accuracy and anti-wind ability for homing control of the parafoil airdrop system in a large wind environment.For fixed-point homing control of parafoil airdrop systems in unknown wind enviroments,a wind identification method using GPS information is proposed to the estimate unknown wind disturbances.Further,homing trajectory planning and trajectory tracking control are conducted according to the identified wind to realize accurate fixed-point homing of the vehicle in an unknown wind environment.