Intermodal Competition: Cargo Airships versus Long-Haul Trucking for Perishable Commodities

Intermodal competition changes with changes in technology, economics, and environmental concerns. Trucks and airships are generally considered not to be competitors, but this depends on the distance of haul. The tonne-kilometer cost of trucking rises much more quickly with distance than it does the cost of a cargo airship. At some distance, the two modes are direct substitutes. The costs of the Mexico-Canada refrigerated truck supply chain are compared with the costs of a 100t-lift, electrically-powered airship. The flight characteristics of the Hindenburg Zeppelin are used as a model for a modern cargo airship. The supply chain cost of trucking tomatoes is used to test the theorical proposition. The cost difference works out to about US10￠/kg (5￠/lb) advantage for trucking Mexican tomatoes to Canada. However, this cost disadvantage of the airship could be made up by their vibrationless ride, better air circulation and one-day service versus four days by truck. This alternative form of transportation could have a positive impact on worldwide north-south distribution of food. Airships can overcome trade barriers and distance to open new markets for perishable food exports. In addition, they would reduce the carbon emissions of transport. Canada imports 160,000 refrigerated truckloads of fruits and vegetables by from the southern US and Mexico. With an average driving distance of 3,000 km, these trucks emit 606,000 MT of CO2 annually. Airships powered by hydrogen fuel cells would have zero-carbon emissions. Markets are not yet incorporating the environmental advantage of airships in any freight comparison, but inevitably this will be important.

Robust design of sliding mode control for airship trajectory tracking with uncertainty and disturbance estimation

The robotic airship can provide a promising aerostatic platform for many potential applications.These applications require a precise autonomous trajectory tracking control for airship.Airship has a nonlinear and uncertain dynamics.It is prone to wind disturbances that offer a challenge for a trajectory tracking control design.This paper addresses the airship trajectory tracking problem having time varying reference path.A lumped parameter estimation approach under model uncertainties and wind disturbances is opted against distributed parameters.It uses extended Kalman filter(EKF)for uncertainty and disturbance estimation.The estimated parameters are used by sliding mode controller(SMC)for ultimate control of airship trajectory tracking.This comprehensive algorithm,EKF based SMC(ESMC),is used as a robust solution to track airship trajectory.The proposed estimator provides the estimates of wind disturbances as well as model uncertainty due to the mass matrix variations and aerodynamic model inaccuracies.The stability and convergence of the proposed method are investigated using the Lyapunov stability analysis.The simulation results show that the proposed method efficiently tracks the desired trajectory.The method solves the stability,convergence,and chattering problem of SMC under model uncertainties and wind disturbances.

ADAPTIVE PREDICTIVE CONTROL OF NEAR-SPACE VEHICLE USING FUNCTIONAL LINK NETWORK

A novel nonlinear adaptive control method is presented for a near-space hypersonic vehicle （NHV） in the presence of strong uncertainties and disturbances. The control law consists of the optimal generalized predictive controller （OGPC） and the functional link network （FLN） direct adaptive law. OGPC is a continuous-time nonlinear predictive control law. The FLN adaptive law is used to offset the unknown uncertainties and disturbances in a flight through the online learning. The learning process does not need any offline training phase. The stability analyses of the NHV close-loop system are provided and it is proved that the system error and the weight learning error are uniformly ultimately hounded. Simulation results show the satisfactory performance of the con- troller for the attitude tracking.

Optimal structural design for a certain near-space composite propeller of airship using adaptive region division blending model

Near-space airship is a frontier and hotspot in current military research and development,and the near-space composite propeller is the key technology for its development.In order to obtain higher aerodynamic efficiency at an altitude of 22 km,a certain near-space composite propeller is designed as a long and slender aerodynamic shape with a 10 m diameter,which brings many challenges to the composite structure design.The initial design is obtained by the composite structure variable stiffness design method using based on fixed region division blending model.However,it weighs 23.142 kg,exceeding the required 20 kg.In order to meet the structural design requirements of the propeller,a variable stiffness design method using the adaptive region division blending model is proposed in this paper.Compared with the methods using the fixed region division blending model,this method optimizes region division,stacking thickness and stacking sequence in a single level,considering the coupling effect among them.Through a more refined region division,this method can provide a more optimal design for composite tapered structures.Additionally,to improve the efficiency of optimization subjected to manufacturing constraints,a hierarchical penalty function is proposed to quickly filter out the solutions that do not meet manufacturing constraints.The above methods combined with a Genetic Algorithm(GA)using specific encoding are adopted to optimize the near-space composite propeller.The optimal design of the structure weighs 18.831 kg,with all manufacturing constraints and all structural response constraints being satisfied.Compared with the initial design,the optimal design has a more refined region division,and achieves a weight reduction of 18.6%.This demonstrates that a refined region division can significantly improve the mechanical performance of the composite tapered structure.

Adaptive functional link network control of near-space vehicles with dynamical uncertainties

The control law design for a near-space hypersonic vehicle（NHV） is highly challenging due to its inherent nonlinearity,plant uncertainties and sensitivity to disturbances.This paper presents a novel functional link network（FLN） control method for an NHV with dynamical thrust and parameter uncertainties.The approach devises a new partially-feedback-functional-link-network（PFFLN） adaptive law and combines it with the nonlinear generalized predictive control（NGPC） algorithm.The PFFLN is employed for approximating uncertainties in flight.Its weights are online tuned based on Lyapunov stability theorem for the first time.The learning process does not need any offline training phase.Additionally,a robust controller with an adaptive gain is designed to offset the approximation error.Finally,simulation results show a satisfactory performance for the NHV attitude tracking,and also illustrate the controller＇s robustness.

Prospect of Near-Space Exploration and Scientific Experiment Carrier Platform Demand

It is an important scientific research activity in China to carry out near-space exploration and scientific experiments via aerospace carriers.Early near-space exploration projects mainly used aircraft,balloons,sounding rockets and Earth satellites to carry out space environment exploration.With the development of China’s space science and technology,microgravity science has become a frontier science that has developed rapidly in the past 20 years.With the continuous progress of national space science and technology,the demand for near-space exploration and scientific experiments is increasing year by year.In the next 2 to 3 years,many advanced science activities and the associated technologies need to conduct corresponding experimental research work.This paper mainly analyzes the significance of scientific research and the ways to realize near-space exploration at home and abroad,and analyzes the directions and innovations that can be carried out in the future.

Biaxial tensile properties and elastic constants evaluation of envelope material for airship

This paper presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216L under biaxial cyclic loading.First the biaxial cyclic tests were carefully carried out on the envelope material to obtain the stress-strain data and the corresponding nonlinearity and orthotropy of the material were analyzed. Then for some determination options with different stress ratios the least squares method minimizing the strain terms was used to calculate the elastic constants from the experimental data.Finally the influences of the determination options with different stress ratios and the reciprocal relationship on the elastic constants were discussed.Results show that the orthotropy of the envelope material can be attributed to the unbalanced crimp of their constitutive yarns in warp and weft directions and the elastic constants vary noticeably with the determination options as well as the normalized stress ratios.In real design practice it is more reasonable to use constants determined for specific stress states in particular stress ratios depending on the project＆#39;s needs.Also calculating the structures with two limitative sets of elastic constants instead of using only one set is recommendable in light of the great variety of the constant＆#39;s values.

平流层飞艇载荷舱电子设备散热仿真分析

飞艇载荷舱电子设备的温度极大地影响了其工作可靠性,随着飞艇载荷舱应用途径的拓展,载荷总功率不断增长,设备设计功耗及热流密度显著提升,但平流层气体密度仅为地面的1/18,对流散热能力差,散热问题逐渐成为制约技术发展的关键问题。文章为了解决高载荷功率下的散热痛点,引入了两相流体回路散热方法,探究其与风扇强迫散热的散热能力,在分析载荷舱电子设备传热特性的基础上,基于计算流体力学,设计了风扇强迫对流散热系统,同时提出一种采用1,1,1,2-四氟乙烷(R134a)流体回路对平流层载荷舱电子设备散热的方法,并使用表观热容法对其进行仿真,计算了两种散热方式下飞艇载荷舱的温度场和流场,得到了两种方式的散热能力。仿真结果表明,风扇的散热极限工率约为591 W,两相流体回路方式散热可以解决700 W的散热需求,使用风扇散热可以满足基本散热需求;使用两相流体回路方式散热可以对平流层飞艇载荷舱电子设备进行有效热控,为平流层大功率电子设备散热的设计和计算提供思路。

临近空间飞艇囊体材料性能研究

简述了临近空间飞艇囊体研究概况,提出了临近空间飞艇囊体技术要求。对临近空间高空飞艇囊体材料进行了综合测试和试验分析。最后针对临近空间飞艇囊体研制目前存在的问题,结合囊体测试数据分析,提出了一些建议。

基于载重飞艇的整体立塔技术仿真研究

在输电铁塔的施工中,悬浮抱杆组塔和整体起吊组塔是目前应用广泛的两种组塔方式。针对这些组塔方式存在人员高空作业风险和大重型装备无法到达山区施工现场等问题,提出一种基于载重飞艇的整体立塔方案。该方案在地面完成整个输电铁塔的组装后,利用载重飞艇提供牵引力,使输电铁塔绕铰接式结构旋转直至竖立。针对立塔全过程,根据飞艇的牵引方式、飞行速度、飞艇牵引力与铁塔所形成的夹角对铁塔应力和应变的影响等,分为三种方案进行仿真研究。仿真结果表明,该整体立塔技术方案安全可靠,避免了人员高空作业的危险性,且能使大重型设备到达山区作业现场。

大型重载飞艇复合材料骨架结构设计及其力学分析

大型重载飞艇具有较为广阔的应用前景,但大尺寸、空间大跨度先进复合材料骨架结构设计与分析技术一直是制约大型重载飞艇发展的关键技术之一。以某型重载飞艇骨架为研究对象,以总体设计给出的相关要求作为设计输入条件,选择较成熟的材料体系和结构连接形式,完成了飞艇复合材料骨架结构设计。骨架的主要结构单元为三角桁架梁,开发了一种基于Python的飞艇骨架结构参数化建模方法。该方法基于刚度等效原理,将三角桁架转化成空间梁单元,可自动生成骨架整体有限元模型和定义连接关系,实现了飞艇骨架结构的参数化快速建模。针对飞艇悬停装卸载这一实际典型载荷工况,开展了骨架整体应力和变形计算,并运用“整体-局部”方法,将整体有限元分析中应力承载严重的等效梁单元还原成精细化三角桁架模型。基于Hashin失效准则,对复合材料圆管、接头等结构元件进行了强度计算和校核,结果验证了方法的有效性。

附有集中质量的飞艇囊体材料动力特性

针对平流层飞艇刚柔一体大型复杂结构系统设计与分析,开展了附有集中质量的飞艇囊体材料动力特性仿真分析研究,将刚度大、质量相对集中的结构零部件简化为集中质量,飞艇囊体简化为双向拉伸的十字形囊体材料试样,分析预张力大小、集中质量的质量和尺寸对囊体材料试样的动力特性影响.结果表明,试样的固有频率随着预张力增大而增大,随着集中质量的质量增大而减小,随着集中质量与试样连接的边长增加而增大;试样的基频与集中质量的高度无关,但第2,3阶频率随着集中质量的高度增加而减小.研究结论为飞艇结构的总体设计与分析以及进一步开展附有集中质量的飞艇囊体材料动力试验提供了理论依据.

基于MBSE的对流层飞艇运行概念研究

面向对流层飞艇起降过程复杂、气象适应能力弱等特殊性,传统基于文本的运行概念分析方法具有设计一致性较差、设计无法有效追溯、验证困难等局限性。基于此,提出了基于模型的系统工程的对流层飞艇运行概念设计方法。首先,建立系统用例与利益攸关者需求的关联关系,保证了设计可追溯性。然后,基于活动图、时序图与内部块图建立对流层飞艇运行场景模型,详细梳理了飞艇运行的执行逻辑与外部交互关系。通过执行状态机对飞艇运行概念模型进行验证,并进一步补充完善利益攸关者需求。最后,通过执行状态机验证了该无人飞艇系统能够满足任务飞行、飞行控制和应急情况响应等利益攸关者的需求。

平流层飞艇囊体材料老化测试研究概述

基于对国内外有关囊体材料老化测试研究文献的充分调研,综述了囊体材料老化机理、老化试验方法、试验对象的选取、性能影响表征与评价等方面的研究现状,老化后的囊体材料常用形貌表征、拉伸测试、透氦率表征及化学结构表征等4种表征方法。鉴于当前对平流层飞艇囊体老化研究缺乏统一的评价指标,且大多研究在囊体材料老化性能验证方面存在不足,提出了后续研究的手段和方向,为浮空器囊体材料的可靠性测试研究和发展提供参考。

飞艇在化工园区实时监测预警中的应用

为提升化工园区气体污染物监测能力、降低事故发生率,文章探讨了飞艇作为监测气体污染物平台的可行性。首先,分析化工园区内气体污染物种类,表明监测气体污染物的重要性;其次,指出现有预防监测技术的不足之处;最后,结合飞艇传感器高度集成、体积小巧灵活、续航持久稳定和能耗经济环保等特性,得出飞艇监测的可行性。其结果表明,飞艇作为气体污染物监测平台具有广阔的发展前景,使得化工园区监测范围更加立体、手段更加多元,以期帮助化工园区更好地应对气体污染物泄漏类突发事件,提升应急响应与处置水平。

SINGULAR PERTURBATION APPROACH TO MOVING MASS CONTROL OF BUOYANCY-DRIVEN AIRSHIP IN 3-D SPACE

The attitude control problem and the guidance problem are solved in 3-D for a buoyancy-driven airship actuated by the combined effects of an internal air bladder which modulates the airshiprs net weight and of two moving masses which modulate its center of mass. A simple and clear modeling is introduced to derive the 8 degree of freedom （DOF） mathematical model. Nonlinear control loops are derived through maximal feedback linearization with internal stability for both dynamics in the longitudinal plane and in the lateral plane. Based on a singular perturbation approach, the superposition of these two control actions in the longitudinal plane and in the lateral plane is shown to achieve the control of the dynamics in 3-D space. The simulations of the airship tracking specified attitude, moving direction and speed in 3-D space are presented.

DYNAMIC MODELING FOR AIRSHIP EQUIPPEDWITH BALLONETS AND BALLAST

Total dynamics of an airship is modeled. The body of an airship is taken as a submerged rigid body with neutral buoyancy, i.e., buoyancy with value equal to that of gravity, and the coupled dynamics between the body with ballonets and ballast is considered. The total dynamics of the airship is firstly derived by Newton-Euler laws and Kirchhoff’s equations. Furthermore, by using Hamiltonian and Lagrangian semi-direct product reduction theories, the dynamics is formulated as a Lie-Poisson system, or also an Euler-Poincaré system. These two formulations can be exploited for the control design using energy-based methods for Hamiltonian or Lagrangian system.

Stabilization and trajectory tracking of autonomous airship's planar motion

The stabilization and trajectory tracking problems of autonomous airship＇s planar motion are studied. By defining novel configuration error and velocity error, the dynamics of error systems are derived. By applying Lyapunov stability method, the state feedback control laws are designed and the close-loop error systems are proved to be uniformly asymptotically stable by Matrosov theorem. In particular, the controller does not need knowledge on system parameters in the case of set-point stabilization, which makes the controller robust with respect to parameter uncertainty. Numerical simulations illustrate the effectiveness of the controller designed.

DYNAMIC MODELING FOR AIRSHIP EQUIPPED WITH BALLONETS AND BALLAST

Total dynamics of an airship is modeled. The body of an airship is taken as a submerged rigid body with neutral buoyancy, i. e. , buoyancy with value equal to that of gravity, and the coupled dynamics between the body with ballonets and ballast is considered. The total dynamics of the airship is firstly derived by Newton-Euler laws and Kirchhoff＇ s equations. Furthermore, by using Hamiltonian and Lagrangian semidirect product reduction theories, the dynamics is formulated as a Lie-Poisson system, or also an Euler-Poincare system. These two formulations can be exploited for the control design using energy-based methods for Hamiltonian or Lagrangian system.

Adaptive fuzzy sliding mode control for robotic airship with model uncertainty and external disturbance

An adaptive fuzzy sliding mode control （AFSMC） ap- proach is proposed for a robotic airship. First, the mathematical model of an airship is derived in the form of a nonlinear control system. Second, an AFSMC approach is proposed to design the attitude control system of airship, and the global stability of the closed-loop system is proved by using the Lyapunov stability theorem. Finally, simulation results verify the effectiveness and robustness of the proposed control approach in the presence of model uncertainties and external disturbances.