Fixed wing unmanned aerial vehicles typically have longer running (flight) time than multicopers, but runways are needed. Because it is difficult to expect a wide runway in the city area, the great need is there to de...Fixed wing unmanned aerial vehicles typically have longer running (flight) time than multicopers, but runways are needed. Because it is difficult to expect a wide runway in the city area, the great need is there to develop a vertical takeoff and landing (VTOL) type fixed-wing UAV that does not require any runway. In addition, our goal was to develop a VTOL plane that contains a stable transit flight characteristic. To achieve this goal, we have designed and developed a test plane and the flight parameters have been extensively tested. For the airframe design, the carbon-bar method was selected for vertical takeoff and landing, and the 11-way method was adopted through dynamics analysis. We assembled the airframe and made a prototype using the Pixhawk flight computer. The developed VTOL plane shows a very smooth transition flight. It is expected that the VOTL UAV will be widely used in the city area in the future for various purposes, such as cargo delivery and emergency medical supply delivery.展开更多
As an attractive transition approach,the altitude-hold transition is a special type of super-maneuvering and the vertical/horizontal flight mode transition that an agile aircraft conducts at fixed altitude.However,it ...As an attractive transition approach,the altitude-hold transition is a special type of super-maneuvering and the vertical/horizontal flight mode transition that an agile aircraft conducts at fixed altitude.However,it is still challenging to implement an autonomous control of the altitude-hold transition while the existing optimal transition planning methods cannot avoid an evident altitude change during the transition process.This paper proposes a corridor-based flight mode transition strategy and presents a successful flight demonstration of the altitude-hold transition on a small ducted-fan tail-sitter unmanned aerial vehicle.In the proposed corridor-based methodology,we model and analyze the transition corridor,concentrate on the dynamic characteristics of the altitude-hold transition,and emphasize that a valid transition trajectory should be governed by its transition corridor.The identified transition corridor reveals that for a given velocity trajectory,the solution for the corresponding trajectories of pitch angle and thrust is unique.Based on this,the transition trajectory generation problem is addressed simply on the velocity-acceleration plane.Furthermore,a proper flight control scheme is devised to track the generated transition trajectories.Finally,the effectiveness of the proposed method is verified through practical flight tests,in which the altitude change is less than 1.1 m during the entire transition course.展开更多
在民机自动飞行过程中,飞行导引系统的模式转换是影响安全的重要因素,应对其进行充分的安全性分析。传统安全分析方法主要关注各个组件的失效因素,忽略了由组件间非线性交互产生的安全问题。为此,采用系统理论过程分析(System Theory Pr...在民机自动飞行过程中,飞行导引系统的模式转换是影响安全的重要因素,应对其进行充分的安全性分析。传统安全分析方法主要关注各个组件的失效因素,忽略了由组件间非线性交互产生的安全问题。为此,采用系统理论过程分析(System Theory Process Analysis,STPA)方法,对飞行导引系统模式转换进行系统且完整的分析。同时,鉴于STPA方法中存在需人工分析的部分,引入了基于时间自动机理论的形式化模型检查工具UPPAAL对系统进行建模与验证,以确保控制结构图的正确性,并识别真正不安全控制行为(Unsafe Control Action,UCA),从而避免资源的浪费。最后,提出规范化的致因因素分析框架对通过验证的UCA进行逐一分析。实例证明,所提方法对航空类复杂系统安全性分析具有较好的效果。展开更多
As an improved guidance method,the attitude head pursuit guidance （AHPG） law enables the attitude pursuit guidance （APG） law to be more suited to transition guidance of air-to-ground missiles. By adding a head ang...As an improved guidance method,the attitude head pursuit guidance （AHPG） law enables the attitude pursuit guidance （APG） law to be more suited to transition guidance of air-to-ground missiles. By adding a head angle into the attitude angle of APG,AHPG directs the missile axis onto the line of sight （LOS）. The maximum range trajectory simulation shows that the elevator deflection angle reaches the saturated value of 10° at the outset and the impact angle is less than 60° when APG is used as transi-tion guidance law. However,the elevator deflection angle on the whole trajectory is reduced to under 5° and the impact angle increased to over 60° when AHPG is used. The formulae to calculate head angles are derived for different target distributions. The simulation of multiple trajectories shows that with the help of the formulae based on AHPG law,the same performance could be achieved.展开更多
Experimental techniques for imaging laminar-turbulent transition of boundary layers using IR thermography are presented for both flight and wind tunnel test environments. A brief overview of other transition detection...Experimental techniques for imaging laminar-turbulent transition of boundary layers using IR thermography are presented for both flight and wind tunnel test environments. A brief overview of other transition detection techniques is discussed as motivation. A direct comparison is made between IR thermography and naphthalene flow visualization. A technique for obtaining quantitative transition location is presented.展开更多
文摘Fixed wing unmanned aerial vehicles typically have longer running (flight) time than multicopers, but runways are needed. Because it is difficult to expect a wide runway in the city area, the great need is there to develop a vertical takeoff and landing (VTOL) type fixed-wing UAV that does not require any runway. In addition, our goal was to develop a VTOL plane that contains a stable transit flight characteristic. To achieve this goal, we have designed and developed a test plane and the flight parameters have been extensively tested. For the airframe design, the carbon-bar method was selected for vertical takeoff and landing, and the 11-way method was adopted through dynamics analysis. We assembled the airframe and made a prototype using the Pixhawk flight computer. The developed VTOL plane shows a very smooth transition flight. It is expected that the VOTL UAV will be widely used in the city area in the future for various purposes, such as cargo delivery and emergency medical supply delivery.
基金supported by Scientific Instruments Development Program of National Natural Science Foundation of China(No.61527810)the Fundamental Research Funds for the Central Universities,Chinathe Key Laboratory of Autonomous Systems and Networked Control,Ministry of Education and the Unmanned Aerial Vehicle Systems Engineering Technology Research Center of Guangdong(China)for supporting this research.
文摘As an attractive transition approach,the altitude-hold transition is a special type of super-maneuvering and the vertical/horizontal flight mode transition that an agile aircraft conducts at fixed altitude.However,it is still challenging to implement an autonomous control of the altitude-hold transition while the existing optimal transition planning methods cannot avoid an evident altitude change during the transition process.This paper proposes a corridor-based flight mode transition strategy and presents a successful flight demonstration of the altitude-hold transition on a small ducted-fan tail-sitter unmanned aerial vehicle.In the proposed corridor-based methodology,we model and analyze the transition corridor,concentrate on the dynamic characteristics of the altitude-hold transition,and emphasize that a valid transition trajectory should be governed by its transition corridor.The identified transition corridor reveals that for a given velocity trajectory,the solution for the corresponding trajectories of pitch angle and thrust is unique.Based on this,the transition trajectory generation problem is addressed simply on the velocity-acceleration plane.Furthermore,a proper flight control scheme is devised to track the generated transition trajectories.Finally,the effectiveness of the proposed method is verified through practical flight tests,in which the altitude change is less than 1.1 m during the entire transition course.
文摘在民机自动飞行过程中,飞行导引系统的模式转换是影响安全的重要因素,应对其进行充分的安全性分析。传统安全分析方法主要关注各个组件的失效因素,忽略了由组件间非线性交互产生的安全问题。为此,采用系统理论过程分析(System Theory Process Analysis,STPA)方法,对飞行导引系统模式转换进行系统且完整的分析。同时,鉴于STPA方法中存在需人工分析的部分,引入了基于时间自动机理论的形式化模型检查工具UPPAAL对系统进行建模与验证,以确保控制结构图的正确性,并识别真正不安全控制行为(Unsafe Control Action,UCA),从而避免资源的浪费。最后,提出规范化的致因因素分析框架对通过验证的UCA进行逐一分析。实例证明,所提方法对航空类复杂系统安全性分析具有较好的效果。
文摘As an improved guidance method,the attitude head pursuit guidance （AHPG） law enables the attitude pursuit guidance （APG） law to be more suited to transition guidance of air-to-ground missiles. By adding a head angle into the attitude angle of APG,AHPG directs the missile axis onto the line of sight （LOS）. The maximum range trajectory simulation shows that the elevator deflection angle reaches the saturated value of 10° at the outset and the impact angle is less than 60° when APG is used as transi-tion guidance law. However,the elevator deflection angle on the whole trajectory is reduced to under 5° and the impact angle increased to over 60° when AHPG is used. The formulae to calculate head angles are derived for different target distributions. The simulation of multiple trajectories shows that with the help of the formulae based on AHPG law,the same performance could be achieved.
文摘Experimental techniques for imaging laminar-turbulent transition of boundary layers using IR thermography are presented for both flight and wind tunnel test environments. A brief overview of other transition detection techniques is discussed as motivation. A direct comparison is made between IR thermography and naphthalene flow visualization. A technique for obtaining quantitative transition location is presented.
