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A Simplified Flexible Multibody Dynamics for a Main Landing Gear with Flexible Leaf Spring  [PDF]
Zhi-Peng Xue,Ming Li,Yan-Hui Li,Hong-Guang Jia
Shock and Vibration , 2014, DOI: 10.1155/2014/595964
Abstract: The dynamics of multibody systems with deformable components has been a subject of interest in many different fields such as machine design and aerospace. Traditional rigid-flexible systems often take a lot of computer resources to get accurate results. Accuracy and efficiency of computation have been the focus of this research in satisfying the coupling of rigid body and flex body. The method is based on modal analysis and linear theory of elastodynamics: reduced modal datum was used to describe the elastic deformation which was a linear approximate of the flexible part. Then rigid-flexible multibody system was built and the highly nonlinearity of the mass matrix caused by the limited rotation of the deformation part was approximated using the linear theory of elastodynamics. The above methods were used to establish the drop system of the leaf spring type landing gear of a small UAV. Comparisons of the drop test and simulation were applied. Results show that the errors caused by the linear approximation are acceptable, and the simulation process is fast and stable. 1. Introduction Automatic takeoff, landing, and taxiing are very important parts of completely autonomous flight of UAV, and taxiing tests on UAVs are obviously expensive and risky as it is easy to bring about accidents under high-speed taxiing. Simulation on the other hand is particularly important before the prototype taxiing experiment. During the development of control systems, real-time simulations such as man-in-the-loop (MIL) and hardware-in-the-loop (HIL) are also used to take place between design level simulations and costly experiments with the real plant [1–3]. Obviously accurate and efficient computer simulations of UAV on-ground models play an important role in the control system design, performance evaluations, and dynamics analysis of such vehicle systems. Meanwhile research on ground dynamics in the past decades has achieved significant results, and the design of these dynamics traditionally relies on mathematical model. Ro [4] has studied aircraft-runway dynamics in detail. In general mathematical equations of ground dynamics are complex, highly coupled, and nonlinear; their derivation and numerical implementation demand considerable time and computer cost. In recent years, the accuracy and computational efficiency of flexible multibody has been the focus of research [5, 6]. The simplified flexible multibody method enables the dynamic response to simulate effectively, even be used in many real-time simulations [7–9]. Nonretractable type landing gear has been widely used in
Problems and Barriers Impeding the Implementation of MagLev Assisted Aircraft Take-Off and Landing Concept  [PDF]
Jozsef Rohacs, Daniel Rohacs
Journal of Transportation Technologies (JTTs) , 2018, DOI: 10.4236/jtts.2018.82006
Abstract: Nowadays, the success of the new technology development and deployment process depends not only on technical, technological solutions, but also on solving the non-technological problems and crossing the societal and psychological barriers. A large international European projects, GABRIEL1 had developed a maglev assisted aircraft take-off and landing, that was applied to conceptual design of aircraft and required on-board and ground systems, had analysed all impacts (effects of concept deployment on effectiveness, safety, security, noise, emissions) and had demonstrated the safe applicability by concept validation. The applied methodology, used methods and the results of the Gabriel projects had been described and discussed by 55 project deliverables. This paper has a special goal: investigating the problems and barriers of possible implementing of the radically new technology, aircraft MagLev assisted take-off and landing. The study was started by identification and classification of the problems and barriers. After it, the problems were systematically analysed by use of special methodology containing the understanding (description) of the problems, investigation of the possible solutions and discussing their applicability (mainly by use of the Gabriel project results). The paper has three major sections: 1) description of the Gabriel concept and project results, 2) introducing some related thoughts on general aspects of new technology developments, and 3) discussion on the problems and their solutions. The major classes of the problems are the 1) technical, technological problems as developing a radically new solution, landing the undercarriage-less aircraft on the magnetic tracks, 2) stakeholders’ problems as decision makers kicking against supporting the developments of so radically new technologies and 3) society barriers like society worrying on and fear of future passengers on flying by aircraft have not conventional undercarriage systems. The paper will show that these problems have safe and cost-effective solutions.
Control design for planar vertical takeoff-and-landing aircraft based on controlled Lagrangians

LI Mao-qing,

控制理论与应用 , 2010,
Abstract: The controller design technique based on controlled Lagrangians(CL) for the mechanical systems with underactuation degree one is applied to control a planar vertical takeoff-and-landing (PVTOL) aircraft system with input coupling. Under the matching condition between the explicit gyroscopic forces, we develop a smooth feedback control law which ensures almost globally asymptotic stabilization for the system. Compared with the results obtained with existing similar methods, this matching controller is simpler in construction while retaining the same convergence performance.
Design and control of aircraft of vertical take-off-and-landing and high-speed forward flight

FAN Peng-hui,WANG Xin-hua,CAI Kai-yuan,

控制理论与应用 , 2010,
Abstract: We design a new aircraft with the ability of vertical take-off-and-landing(VTOL), like a four-rotor aircraft; and the ability of flying forward with high speed, like an aircraft with fixed-wings. The flight-mode transition from hovering to forward flight and the reverse process are achieved. A flight-mode transition control law is designed. Both the designscheme and the proposed control law are verified by simulation.
Design and simulation of controllable aircraft main landing gear operating actuator

- , 2016, DOI: 10.13700/j.bh.1001-5965.2015.0034
Abstract: 摘要 传统的起落架收放液压系统在使用中缺乏可控性,按照起落架收起时飞机极限过载设计的起落架收放液压作动器在常见的小过载工况下可能产生较大的冲击。提出了一种用于主起落架的可控变速收放作动器的概念设计,使用双向比例节流阀根据过载大小调节阻尼作用。结合起落架收放机构多体模型和收放作动器液压模型,对不同过载工况下主起落架收起的动力学过程进行了仿真分析。与常规设计相比,在一定的设计约束下降低了支柱终止速度、回油压力峰值和结构冲击。研究了变速收放作动器输入压力和进回油油路阻尼相对大小对仿真结果的影响。提出了一种改进的可控变速收放作动器设计,利用惯性力的作用进一步降低了起落架收起时的作动筒载荷峰值和冲击。
Abstract:Conventional aircraft landing gear hydraulic system has little controllability during operation. Landing gear hydraulic operating actuator designed to operate under maximum aircraft load factor during landing gear retraction may lead to more serious impact under common load factors. Conceptual design of a controllable operating actuator applied to aircraft main landing gear was raised, which employs 2-way proportional throttle valves to adjust hydraulic damping according to load factor. Multibody model of landing gear retracting device and hydraulic model of operating actuator were combined in main landing gear retraction simulation under different load factors. Controllable design generates lower strut ending speed, actuator back pressure and structural impact compared with conventional design under certain design constrains. Effects of actuator input pressure and damping relation between the input and output throttle valves on simulation results were studied. Improved design of controllable operating actuator was raised, which further lessened maximum actuator load and impact of landing gear retraction by using the effect of inertia force.
Automatic Carrier Landing Control for Unmanned Aerial Vehicles Based on Preview Control  [PDF]
Zhen Ziyang, Ma Kun, Bhatia Ajeet Kumar
- , 2017, DOI: 10.16356/j.1005-1120.2017.04.413
Abstract: For carrier-based unmanned aerial vehicles (UAVs), one of the important problems is the design of an automatic carrier landing system (ACLS) that would enable the UAVs to accomplish autolanding on the aircraft carrier. However, due to the movements of the flight deck with six degree-of-freedom, the autolanding becomes sophisticated. To solve this problem, an accurate and effective ACLS is developed, which is composed of an optimal preview control based flight control system and a Kalman filter based deck motion predictor. The preview control fuses the future information of the reference glide slope to improve landing precision. The reference glide slope is normally a straight line. However, the deck motion will change the position of the ideal landing point, and tracking the ideal straight glide slope may cause landing failure. Therefore, the predictive deck motion information from the deck motion predictor is used to correct the reference glide slope, which decreases the dispersion around the desired landing point. Finally, simulations are carried out to verify the performance of the designed ACLS based on a nonlinear UAV model.
СПОСОБИ П ДВИЩЕННЯ БЕЗПЕКИ ВИКОНАННЯ ПОСАДКИ Л ТАКА В УМОВАХ НЕВИЗНАЧЕНОСТ Ways to improve the safety of landing aircraft in conditions of uncertainty Способы повышения безопасности выполнения посадки самолета в условиях неопределенности  [cached]
В.М. Казак,М.П. Кравчук,Т.В. Будзинська,В.Ю. М?щерякова
Proceedings of National Aviation University , 2008,
Abstract: Проанал зовано концепц необх дних нав гац йних характеристик для етапу зниження посадки л така. Наведено алгоритм керування л тальним апаратом в умовах невизначеност , оснований на тунельн й концепц виконання посадки з використанням нтелектуально системи керування на основ нейронеч ткого регулятора. An analysis of RNP concept at the stage of an aircraft descent and landing was made. Control algorithm of an aircraft under the conditions of uncertainty, based on the tunnel concept of landing performance using an intelligent control system, based on the neural fuzzy-logic regulator, was presented. Проанализированы концепции необходимых навигационных характеристик для этапа снижения и посадки самолета. Привела алгоритм управления летательным аппаратом в условиях неопределенности, основанный на туннельной концепции выполнения посадки с использованием интеллектуальной системы управления на основе нейронечеткой регулятора.
Autonomous take-off and landing of a tethered aircraft: a simulation study  [PDF]
Eric Nguyen Van,Lorenzo Fagiano,Stephan Schnez
Mathematics , 2015,
Abstract: The problem of autonomous launch and landing of a tethered rigid aircraft for airborne wind energy generation is addressed. The system operates with ground-based power conversion and pumping cycles, where the tether is repeatedly reeled in and out of a winch installed on the ground and linked to an electric motor/generator. In order to accelerate the aircraft to take-off speed, the ground station is augmented with a linear motion system composed by a slide translating on rails and controlled by a second motor. An onboard propeller is used to sustain the forward velocity during the ascend of the aircraft. During landing, a slight tension on the line is kept, while the onboard control surfaces are used to align the aircraft with the rails and to land again on them. A model-based, decentralized control approach is proposed, capable to carry out a full cycle of launch, low-tension flight, and landing again on the rails. The derived controller is tested via numerical simulations with a realistic dynamical model of the system, in presence of different wind speeds and turbulence, and its performance in terms of landing accuracy is assessed. This study is part of a project aimed to experimentally verify the launch and landing approach on a small-scale prototype.

DENG Yangchen,

力学与实践 , 2008,
Abstract: In the light weight design of truss-like landing-gear structure, the related specification on strength is considered. The bars' strength and critical loads are used as constraints and the minimum structural weight design is achieved by shape and size optimization. The data obtained from an example agree with the results of static force test. Theoretical analysis and the flight of model planes carrying load show that the approach is not only feasible but also effective. It can be used to design the landing-gear structure of a small or super light-weighted vehicle. %Finally, three conclusions have been drawn from this paper.
Aircraft Landing Problem: Efficient Algorithm for a Given Landing Sequence  [PDF]
Abhishek Awasthi,Oliver Kramer,J?rg L?ssig
Computer Science , 2013,
Abstract: In this paper, we investigate a special case of the static aircraft landing problem (ALP) with the objective to optimize landing sequences and landing times for a set of air planes. The problem is to land the planes on one or multiple runways within a time window as close as possible to the preferable target landing time, maintaining a safety distance constraint. The objective of this well-known NP-hard optimization problem is to minimize the sum of the total penalty incurred by all the aircraft for arriving earlier or later than their preferred landing times. For a problem variant that optimizes a given feasible landing sequence for the single runway case, we present an exact polynomial algorithm and prove the run-time complexity to lie in $O(N^3)$, where $N$ is the number of aircraft. The proposed algorithm returns the optimal solution for the ALP for a given feasible landing sequence on a single runway for a common practical case of the ALP described in the paper. Furthermore, we propose a strategy for the ALP with multiple runways and present our results for all the benchmark instances with single and multiple runways, while comparing them to previous results in the literature.
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