# Design of a Hand-Launched Solar-Powered Unmanned Aerial Vehicle (UAV) System for Plateau
## 1 Introduction  
With the development of the world economy, energy crisis and environmental pollution are becoming a serious problem. In recent years, with the rapid improvement of technology of solar cell and secondary battery, solar-powered aircraft, due to the advantages of environmental protection and long endurance, following the 'Pathfinder' [1] and 'Helios' [2], the world set off a research upsurge of solar-powered UAV once again. Solar-powered UAV, which converts solar energy into electricity and stores it in secondary batteries during daytime flight, has better endurance than conventional aircraft and may even be able to fly permanently. The long-endurance capability of the solar-powered UAV platform is particularly important in rescue missions, forest fire prevention, communication coverage, and protection of endangered animals. In view of the extreme flight environment in the plateau region, this paper proposes a design method of small, solar-powered UAV suitable for low-temperature and high altitude areas, including a solar irradiance model that can reflect the geography and time and abattery weight model that considers the impact of low temperature on battery performance. Based on this, a small aileron-free UAV was developed for ecological monitoring and animal protection in plateau areas. This paper also developed the dynamics model of aileron-free UAV, analyzed the characteristics of UAV's stability and maneuverability in high-altitude flight, and designed the control and tracking system for high-altitude flight. Finally, in Qiangtang, Tibet, China's first solar-powered UAV took off and landed at an altitude of more than 4500 m. The experiment verified the correctness of the design method and the control method, and analyzed the feasibility of the perpetual flight with different loads according to the flight energy consumption data (Figure 1). In recent years, solar-powered aircraft have been developed in both manned and unmanned aircraft. In terms of manned solar aircraft, 'Solar Impulse 2', the world's largest solar-powered airplane, successfully completed the world's first solar-powered flight around the world on 26 July 2016 [3]. On the other hand, many researchers focus on employing large-scale solar-powered high-altitude long-endurance (HALE) UAVs as atmospheric satellites. Typical examples are 'Solara' [4] and 'Zephyr S', the latter of which has broken the previous record of 14 days set by the 'Zephyr 7' prototype [5] with approximately 25 days and 23 h of flight on 11 July 2018 [6]. In contrast, smaller-scale, solar-powered UAVs are mostly designed for low-altitude long-endurance (LALE) applications. In 2008,'sky sailor', a small solar-powered UAV from Switzerland, flew for 27 h. The structural design of the UAV referred to the glider for competition and it weighed only 780 g [7]. The 'AtlanticiSolar' small UAV from the Swiss Federal Institute of Technology Zurich completed a flight of 81.5 h in July 2015, setting an endurance record for an aircraft under 50 kg. Compared with large solar-powered aircraft, small solar-powered UAV have higher structural weight coefficient and lower load capacity, so they are suited for low-altitude and long-endurance missions. [PERSON] proposed a matching parameter model of energy and power for perpetual flight [7] of small solar UAV in 2008. Based on the energy system model, [PERSON] proposed an energy-robust design method that allows design of solar-powered UAVs for energetically robust perpetual flight in sub-optimal meteorological conditions [8]. In both methods, the solar irradiance model was a simplified sinusoidal model. Small solar-powered UAVs fly mostly at low altitudes, so most previous studies did not consider the effect of low temperatures on battery performance.