# Design of a Hand-Launched Solar-Powered Unmanned Aerial Vehicle (UAV) System for Plateau
## 6 Conclusions  
This paper proposed a complete research process of a hand-launched solar-powered UAV for plateau, from conceptual design method, detailed design, dynamics modeling, control scheme design, numerical simulation, and hardware in the loop simulation experiment to field experiments.  
In order to achieve perpetual flight in the plateau region, this paper proposed a conceptual design method of solar-powered UAV based on energy balance and the optimal parameter solution was found for the plateau region as the mission environment. The main conceptual parameters indicate that it is feasible for small, solar-powered UAV to fly day and night (perpetual flight) at high altitudes during the summer. In the design model, the solar irradiance model took latitude, altitude, date, and other parameters as input, which can more accurately reflect the sunshine conditions at different geographical locations and time compared with the simplified model. In this paper, real irradiance data were collected by the total irradiance meter to modify the model and the main parameters of the modified model, such as maximum illumination and sunshine duration, were in good agreement with the experimental data.  
In view of the low-temperature flight environment of the UAV, the temperature influence factor was introduced into the traditional battery model, and the battery weight model considering the low-temperature influence was proposed. Among them, the temperature influence factor was measured by the low-temperature discharge test of the battery.  
To validate the design methodology, a full-system, hand-launched, solar-powered UAV was designed and fabricated, including configuration, structure, payload selection, and whole avionics.  
Based on the six-degrees-of-freedom equation of motion, this paper analyzed the changes in the stability and maneuverability of aileron-free UAV at high altitude. At high altitude, the stability of both spiral mode and roll mode were worse, and the speed sensitivity of Dutch roll mode increased. At high altitude, the damping of UAV was reduced and the oscillation convergence after disturbance was slower. According to the flight conditions of the plateau, the longitudinal height tracking control law with continuous closed loop and the lateral-directional trajectory tracking control law based on \(L_{1}\) method were designed, respectively.  
Finally, the flight test was conducted at an altitude of 4600 m in Qiangtang (31.988\({}^{\circ}\) E, 87.317\({}^{\circ}\) N), Tibet, and the feasibility of the design method and control system was verified. The cruise power data of the UAV with different loads indicate that it is feasible for the UAV to achieve perpetual flight at an altitude of 4600 m during summer. Less ideal seasons and more stringent mission requirements will prevent the UAV from achieving perpetual flight, but it still has better endurance, which is the unique advantage of solar-powered UAV. The design method and verification method can be extended to other similar UAV platform.  
[PERSON]. ([PERSON]) and [PERSON] conducted the whole design method and system modeling. [PERSON]. ([PERSON]) and [PERSON] contributed the designing and manufacture of hardware system of prototype. [PERSON]. ([PERSON]) analyzed the experiment result. [PERSON]. ([PERSON]) and [PERSON] wrote the paper. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Innovation plan of the Institute grant number TC2018 DYDS24 and Key R&D Projects in Shaanxi Province of China grant number 2018 ZDCXL-GY-03-04.  
The authors declare no conflict of interest.