Study On Homing Strategy For Parafoil System Under Wind Field

Parafoil has become a research focus of accurate airdrop due to its advantages of light weight,small size and controllable operation.By some certain navigation,guidance and control implementation,parafoil can land accurately.While unlike normalaircraft,the parafoil system has the complex aerodynamic characteristics that make it difficult to establish anaccurate dynamic model.At the same time,due to the complexity and uncertainty of the flight environment of parafoil,it is easy for parafoil systems to deviate from the target point under the influence of wind field.In this paper,the author studied a high-fidelity dynamics modeling,homing trajectory design and optimization with wind field prediction and uncertainty study of flight progress for the parafoil system.The content includes:(1)The aerodynamic characteristics of parafoil were analyzed,and a polynomial aerodynamic model of parafoil was established.The six and nine-degree-of-freedom dynamic model of parafoil system were established by absolute coordinate method.(2)The wind field model was built,and the simulation data of the nine-degree-offreedom model of the parafoil system was taken as the parafoil’s real flight data.The wind field was recognized by a wind field identification method which fusing approximate dynamic model,as a result,the robustness of the traditional homing method was enhanced.In the initialization stage,the wind field in the landing zone was clustered to get the initial prediction results.In the flight control stage,on the basis of the real-time identification of wind field,the homing trajectory of the parafoil system was planned in real time with the method of three-segment homing.Then homing trajectory of the parafoil system under variable wind field was obtained.Lastly,planed by the five-stage homing method,the homing trajectory was optimized by using pseudo-spectral method.As a consequence,the control variables on every stage were all constant,which made the method easy to be implemented to engineering applications.(3)The parafoil homing path in hybrid environment was studied using the RapidlyExploring Random Tree(RRT)method.New nodes were fined by the fourth-order RungeKutta method.Moreover,a case study was conducted by using both the RRT-Connect and the single RRT,whose results which included planned trajectories and searching time were compared with each other to analyse advantages and disadvantages of these two methods.(4)The uncertainty of control quantity,wind field and other factors in parafoil homing process were studied by using GPC(Generalized Polynomial Chaos)method to obtain the influence of control variable and wind wield on the system output.The content of this study can provide an useful reference for the dynamics modeling of the parafoil system,the airdrop wind field identification for airdrop and the homing trajectory design and optimization.