Research On Cooperative Airdrop For Multiple Autonomous Parafoil Systems

In large-scale earthquake relief,battlefield supplies and other occasions,the rapid and precise airdrop of emergency supplies is crucial to timely meet the requirements of mission,which has aroused the interest of researchers from the United States,Europe and other countries.Existing parafoils equipped with GPS,INS and other on-board sensors,have the autonomous homing ability,which can follow the planned trajectory to the target area,so the parafoils can be viewed as intelligence agent.The current study mainly focused on the system modeling,trajectory planning and trajectory tracking for single parafoil system,but multiple autonomous parafoil systems can better meet the needs of the mission in many practical tasks.Under the background that the Y-20 transport plane has been delivered into service in 2016,the problem of insufficient delivery capacity of airdrop has been alleviated,the research on the cooperative airdrop of multiple parafoils is of more strategic significance and has a greater application prospect in the defense industry,so it has become a new important direction in the field of airdrop.Compared with single parafoil drop,multiple parafoils drop will face more difficulties and challenges.It must ensure that all the parafoils can be precisely dropped to the target area.Meanwhile,the landing should be upwind to reduce the landing impact.The parafoils dropped from different positions and heading angles need to be gradually drawn closer from the scatter state to reduce the landing dispersion and reduce the collection difficulty of supplies.The seperation distance between the parafoils should be larger than the safe distance,so as to minimize the possibility of collision and ensure the safety of all the parafoil.All parafoils need to fly in a more organized manner,that is,the parafoil should fly in a formation to the target area,so that the supplies can be regrouped as soon as possible after landing,improving their effectiveness and survivability.In this paper,the combination of theoretical analysis and numerical simulation is used to study the system modelling,trajectory planning and trajectory tracking for multiple parafoil systems.Further,the trajectories planning and the formation problem for multiple parafoil systems are studied systematically.This thesis established the parafoil 9 DOF model,6 DOF model,the reduced order model in inertial coordinate system and in the wind fixed coordinates,respectively.The relative motion characteristics between the canapy and the load are analyzed in detail,and the models with different complexity are compared.The research shows that different models have different complexity,and the suitable model can be choosed according to the needs of the application scene.The aerodynamic parameters of the 9DOF model were identified based on the experimental measuring and test data of air drop,which improved the reliability of the model.The overall trajectory planning problem for multiple parafoil systems is studied,the overall trajectory planning from the computed air release point to the landing target point is planned.Firstly,the optimal control homing trajectory is planned based on the Gauss pseudo-spectral method,and then the multiphase homing trajectory is planned based on the genetic algorithm.The two kinds of planned trajectory are compared.The optimal control homing method takes into account the requirements of the lowest energy consumption,and multiphase homing method considers the parafoil flight characteristics of the gliding and turning movement,it is simple and easy to implement in engineering.The cooperative multiple trajectories planning problem for mult-parafoil systems is studied,which satisfies the requirement of precise airdrop and upwind landing,and the spacing between each other is greater than the safe distance,each parafoil only needs to track their own planned trajectory to achieve the goal of the cooperative airdrop.However,formation problem is not considered in this chapter.This thesis further studied the formation guidance problem of multi-parafoil systems.A leader-follower consensus-based guidance algorithm was designed for multiple parafoils formation airdrop.The pilot parafoil tracks the overall planned trajectory,other follower parafoils track the pilot parafoil and consensus with the pilot parafoil,and then the cooperative formation airdrop can be achieved.The guidance algorithm designed in this thesis only requires local communication between the follower parafoils,which reduces the communication load.The leader-follower cooperative formation airdrop has the possibility of single point of failure.This thesis further designs a cooperative formation guidance algorithm based on virtual structure.This guidance algorithm has no actual leader,and all parafoils are followers.The virtual structure moves along the aforementioned the overall trajectory,and each parafoil follows the corresponding point on the virtual structure,the cooperative airdrop can be realized.The results in this thesis provide a reference for the cooperative airdrop of multi-parafoil systems,which have important theoretical value to realize the rapid and precise airdrop for a large number of goods and materials.