Longitudinal Control for Balloon-Borne Launched Solar Powered UAVs in Near-Space

Aiming to improve the pull-up control performance in the process of releasing balloonborne solar powered UAVs(Unmanned Aerial Vehicles),this paper establishes the full flight mechanics equations with flexible modes,and proposes the control method suitable for engineering application.To be specific,the authors first calculate the real aerodynamic force on horizontal stabilizer by comparing the fuselage deformation in ballooning test with that in static loading test.Furthermore,considering fuselage elastic deformation,the pitching moment coefficient is obtained and the influence of airspeed and elevator angle on pitching moment coefficient and control surface efficiency are analysed.Second,the authors establish a complete flight mechanics model,including elastic structural dynamic model and rigid flight dynamic model,by comprehensively considering the aerodynamic data,the relationship between fuselage deformation and load,as well as the ballooning test.Third,the authors perform the numerical simulation and comparison study on control performance between rigid model and flexible model.Moreover,the authors implement model modification based on the low altitude flight test and steady-state point analysing.Finally,a scaled UAV is used to complete the balloon-borne launching test.The results show that the longitudinal control method can analyse the longitudinal aerodynamics and control characteristics accurately,and could be effectively utilized in the pull-up control of the balloon-borne solar powered UAV.

3D Path Planning of the Solar Powered UAV in the Urban-Mountainous Environment with Multi-Objective and Multi-Constraint Based on the Enhanced Sparrow Search Algorithm Incorporating the Levy Flight Strategy

In response to practical application challenges in utilizing solar-powered unmanned aerial vehicle(UAV)for remote sensing,this study presents a three-dimensional path planning method tailored for urban-mountainous environment.Taking into account constraints related to the solar-powered UAV,terrain,and mission objectives,a multi-objective trajectory optimization model is transferred into a single-objective optimization problem with weight factors and multiconstraint and is developed with a focus on three key indicators:minimizing trajectory length,maximizing energy flow efficiency,and minimizing regional risk levels.Additionally,an enhanced sparrow search algorithm incorporating the Levy flight strategy(SSA-Levy)is introduced to address trajectory planning challenges in such complex environments.Through simulation,the proposed algorithm is compared with particle swarm optimization(PSO)and the regular sparrow search algorithm(SSA)across 17 standard test functions and a simplified simulation of urban-mountainous environments.The results of the simulation demonstrate the superior effectiveness of the designed improved SSA based on the Levy flight strategy for solving the established single-objective trajectory optimization model.