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154 results on '"Li, Daochun"'

1. An Efficient Trajectory Generation for Bi-copter Flight in Tight Space

Author

Dong, Xin, Cui, Yangjie, Xiang, Jingwu, Li, Daochun, and Tu, Zhan

Subjects
Computer Science - Robotics
Abstract

Unlike squared (or alike) quadrotors, elongated bi-copters leverage natural superiority in crossing tight spaces. To date, extensive works have focused on the design, modeling, and control of bi-copters. Besides, a proper motion planner utilizing bi-copters' shape characteristics is essential to efficiently and safely traverse tight spaces, yet it has rarely been studied. Current motion planning methods will significantly compromise their ability to traverse narrow spaces if the map is inflated based on the long dimension of the bi-copter. In this paper, we propose an efficient motion planning method that enables the safe navigation of bi-copters through narrow spaces. We first adapt a dynamic, feasible path-finding algorithm with whole-body collision checks to generate a collision-free path. Subsequently, we jointly optimize the position and rotation of the bi-copter to produce a trajectory that is safe, dynamically feasible, and smooth. Extensive simulations and real-world experiments have been conducted to verify the reliability and robustness of the proposed method., Comment: 8 pages,8 figures

Published
2024

6. Composite Adaptive Control for Anti-Unwinding Attitude Maneuvers: An Exponential Stability Result Without Persistent Excitation

Author

Shao, Xiaodong, Hu, Qinglei, Li, Daochun, Shi, Yang, and Yi, Bowen

Subjects
Electrical Engineering and Systems Science - Systems and Control
Abstract

This paper provides an exponential stability result for the adaptive anti-unwinding attitude tracking control problem of a rigid body with uncertain but constant inertia parameters, without requiring the satisfaction of persistent excitation (PE) condition. Specifically, a composite immersion and invariance (I&I) adaptive controller is derived by integrating a prediction-error-driven learning law into the dynamically scaled I&I adaptive control framework, wherein we modify the scaling factor so that the algorithm design does not involve any dynamic gains. To avoid the unwinding problem, a barrier function is introduced as the attitude error function, along with the tactful establishment of two crucial algebra properties for exponential stability analysis. The regressor filtering method is adopted in combination with the dynamic regressor extension and mixing (DREM) procedure to acquire the prediction error using only easily obtainable signals. In particular, aiding by a constructive liner time-varying filter, the scalar regressor of DREM is extended to generate a new exciting counterpart. In this way, the derived controller is shown to permit closed-loop exponential stability without PE, in the sense that both output-tracking and parameter estimation errors exponentially converge to zero. Further, the composite learning law is augmented with a power term to achieve synchronized finite/fixed-time parameter convergence. Numerical simulations are performed to verify the theoretical findings., Comment: 15 pages

Published
2021

22. Discrete Adjoint Optimization Method for Low-Boom Aircraft Design Using Equivalent Area Distribution.

Author

Ma, Chuang, Huang, Jiangtao, Li, Daochun, Deng, Jun, Liu, Gang, Zhou, Lin, and Chen, Cheng

Subjects
AERODYNAMIC load, DRAG coefficient, DRAG force, AIRPLANE motors, EQUATIONS
Abstract

This paper introduces a low-boom aircraft optimization design method guided by equivalent area distribution, which effectively improves the intuitiveness and refinement of inverse design. A gradient optimization method based on discrete adjoint equations is proposed to achieve the fast solution of the gradient information of target equivalent area distribution relative to design variables and to drive the aerodynamic shape update to the optimal solution. An optimization experiment is carried out based on a self-developed supersonic civil aircraft configuration with engines. The results show that the equivalent area distribution adjoint equation can accurately solve the gradient information. After optimization, the sonic boom level of the aircraft was reduced by 13.2 PLdB, and the drag coefficient was reduced by 60.75 counts. Moreover, the equivalent area distribution adjoint optimization method has outstanding advantages, such as high sensitivity and fast convergence speed, and can take both the low sonic boom and the low drag force of the aircraft into account, providing a powerful tool for the comprehensive optimization design of supersonic civil aircraft by considering sonic boom and aerodynamic force. [ABSTRACT FROM AUTHOR]

Published
2024
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28. Advances and Challenges of Crosswind Mode Airborne Wind Energy Aircrafts

Author

Wang Ruoqin, Yan De, Li Liuqing, Wan Zhiqiang, and Li Daochun

Subjects
high-altitude wind energy, wind power generation, airborne wind energy systems, crosswind mode, aircraft design, Motor vehicles. Aeronautics. Astronautics, TL1-4050
Abstract

Wind energy is one of the mainstream types of renewable energy. At present, the majority of the traditional wind turbines could only make use of the near-earth wind energy. However, the high-altitude wind energy has a greater value and potential for its high stability and large storage of energy. The research of exploiting high-altitude wind energy is starting up in China while there are studies about the usage of high-altitude wind energy across the world and some are in the process of flight test. The research on the variation and development of the altitude wind energy system(AWES) is conducted which contains an analysis of crosswind mode, an introduction of typical AWES abroad in last decade, a discussion of critical points including tether, accuracy control, multifunctional ground station and comprehensive optimization as a foundation for future development and further research on this direction.

Published
2018
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45. Design and experimental study of a new flapping wing rotor micro aerial vehicle

Author

Jinwu Xiang, Ziyu Wang, Dong Xin, and Li Daochun

Subjects
Computer science, Flapping wing rotor, Mechanical Engineering, Flight control, Rotation around a fixed axis, Aerospace Engineering, Forward flight, TL1-4050, Change control board, Flight test, Flapping wing, Attitude control, Attitude estimation, Control theory, Flapping, Flight tests, Control parameters, Micro aerial vehicle (MAV), Motor vehicles. Aeronautics. Astronautics
Abstract

A three-wing Flapping Wing Rotor Micro Aerial Vehicle (FWR-MAV) which can perform controlled flight is introduced and an experimental study on this vehicle is presented. A mechanically driven flapping rotary mechanism is designed to drive the three flapping wings and generate lift, and control mechanisms are designed to control the pose of the FWR-MAV. A flight control board for attitude control with robust onboard attitude estimation and a control algorithm is also developed to perform stable hovering flight and forward flight. A series of flight tests was conducted, with hovering flight and forward flight tests performed to optimize the control parameters and assess the performance of the FWR-MAV. The hovering flight test shows the ability of the FWR-MAV to counteract the moment generated by rotary motion and maintain the attitude of the FWR-MAV in space; the experiment of forward flight shows that the FWR-MAV can track the desired attitude.

Published
2020

47. Gust Response of Spanwise Morphing Wing by Simulation and Wind Tunnel Testing.

Author

Yao, Zhuoer, Kan, Zi, and Li, Daochun

Subjects
WIND tunnel testing, ORNITHOPTERS, SPACE suits, COMPUTATIONAL fluid dynamics, UNSTEADY flow (Aerodynamics)
Abstract

The spanwise morphing wing can change its aerodynamic shape to suit its flight environment, thereby having the potential to improve the flight performance of the aircraft, especially in gusty conditions. To investigate the potential of morphing wings, the aerodynamic performance of a spanwise morphing wing with a flapping wingtip in a gust environment was analyzed in this paper. The aerodynamic characteristics of the morphing wing are hard to measure accurately, and thus a wind tunnel test was carried out to study the influences of morphing parameters, such as the morphing length, amplitude and frequency on the gust alleviation effect. The flow mechanism of the designed spanwise morphing wing was analyzed in detail by the instantaneous lift results of the wind tunnel test and the flow field results of the CFD method. The results have shown that with appropriate morphing parameters, the spanwise morphing wing designed in this paper can effectively achieve gust alleviation during flight. The conclusions obtained in this paper can be useful guidance for the design of morphing aircraft. [ABSTRACT FROM AUTHOR]

Published
2023
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48. Aerodynamic characteristics of morphing wing with flexible leading-edge

Author

Zi Kan, Tong Shen, Li Daochun, Lu Zhang, and Jinwu Xiang

Subjects
0209 industrial biotechnology, Lift coefficient, Leading edge, Materials science, Aerospace Engineering, 02 engineering and technology, Computational fluid dynamics, 01 natural sciences, Morphing wings, 010305 fluids & plasmas, Flexible leading-edge, Aerodynamics, 020901 industrial engineering & automation, Deflection (engineering), 0103 physical sciences, Stall angle, Motor vehicles. Aeronautics. Astronautics, Angle of attack, Mechanical Engineering, Stall (fluid mechanics), TL1-4050, Mechanics, Morphing, Physics::Space Physics, Pitching moment
Abstract

The morphing wing can improve the flight performance during different phases. However, research has been subject to limitations in aerodynamic characteristics of the morphing wing with a flexible leading-edge. The computational fluid dynamic method and dynamic mesh were used to simulate the continuous morphing of the flexible leading-edge. After comparing the steady aerodynamic characteristics of morphing and conventional wings, this study examined the unsteady aerodynamic characteristics of morphing wings with upward and downward deflections of the leading-edge at different frequencies. The numerical results show that for the steady aerodynamic, the leading-edge deflection mainly affects the stall characteristic. The downward deflection of the leading-edge increases the stall angle of attack and nose-down pitching moment. The results are opposite for the upward deflection. For the unsteady aerodynamic, at a small angle of attack, the transient lift coefficient of the upward deflection, growing with the increase of deflection frequency, is larger than that of the static case. The transient lift coefficient of the downward deflection, decreasing with the increase of deflection frequency, is smaller than that of the static case. However, at a large angle of attack, an opposite effect of deflection frequency on the transient lift coefficient was demonstrated. The transient lift coefficient is larger than that of the static case when the leading edge is in the nose-up stage, and lower than that of the static one in the nose-down stage.

Published
2020

49. Delaying stall of morphing wing by periodic trailing-edge deflection

Author

Chunxiao Cheng, Zi Kan, Li Daochun, and Jinwu Xiang

Subjects
Physics, 0209 industrial biotechnology, Angle of attack, business.industry, Mechanical Engineering, Aerospace Engineering, Stall (fluid mechanics), TL1-4050, 02 engineering and technology, Aerodynamics, Structural engineering, Hardware_PERFORMANCEANDRELIABILITY, Morphing wing, 01 natural sciences, GeneralLiterature_MISCELLANEOUS, 010305 fluids & plasmas, Morphing, 020901 industrial engineering & automation, Amplitude, Deflection (engineering), 0103 physical sciences, Trailing edge, business, ComputingMethodologies_COMPUTERGRAPHICS, Motor vehicles. Aeronautics. Astronautics
Abstract

Morphing wings can improve aircraft performance during different flight phases. Recently research has focused on steady aerodynamic characteristics of the morphing wing with a flexible trailing-edge, and the unsteady aerodynamic and stall characteristics in the deflection process of the morphing wing are worthy further investigation. The effects of the angle of attack and deflection rate on aerodynamic characteristics were examined, and based on the aerodynamic characteristics of the morphing wing, a method was developed to delay stall by using the flexible periodic trailing-edge deflection. The numerical results show that the lift coefficients in the deflection process are smaller than those in the static situation at small angles of attack, and that the higher the deflection rate is, the smaller the lift coefficients will be. On the contrary, at large angles of attack, the lift coefficients are higher than those in the static case, and they become larger with the increase of the deflection rate. Further, the periodic deflection of the flexible trailing-edge with a small deflection amplitude and high deflection rate can increase lift coefficients at the critical stall angle. Keywords: Aerodynamics, Computational fluid dynamics, Flexible structures, Morphing wings, Stall angle

Published
2020

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