Differential-turn maneuvering

Control harmonization for flight controls which are additional to the conventional ones, such as thrust-vectoring and variable-sweep controls, is examined by means of a hodograph device for the case of flight of a single aircraft under manual control, in one version, or optimal control in another. The use of thrust vectoring in a turning duel formulated as a differential game with energy-modelled vehicles is examined in a preliminary qualitative way. For a craft with sufficient thrust to provide hovering capability, the resulting high turn rates attainable at very low energies greatly enhance evasive capability but do not lend themselves well to offensive exploitation with short-range tail-aspect armament.     

Thrust-vectored differential turns

Differential-turning games played with thrust vectoring as an aid to maneuvering are examined in an extension of the research of a companion paper which reports a study of thrust-vectored maneuvering in energy approximation. The benefits are found to be major when there is a sufficient margin of thrust over weight to permit hover. Families of turning duels between a conventional aircraft and a thrust-vectored opponent are described in a computational example.     

一种多旋翼飞行器的设计及实验验证

传统多旋翼机具有欠驱动特性,且平移、旋转运动均存在强耦合,极大地限制了飞行器的机动性能．为此本文设计了一种具备全向运动、推力矢量控制飞行、倾转悬停功能的多旋翼飞行器．该飞行器结构为正四面体,4个倾转旋翼模组分别固定于该四面体的4个顶点．每个倾转旋翼模组能够提供矢量推力,从结构上实现了飞行器姿态控制和位置控制的解耦,使得飞行器能够实现3维空间中全姿态的轨迹跟踪．为避免欧拉角控制产生的奇异性,设计了基于四元数的姿态控制器．利用可控性原理分析了旋翼发生故障时飞行器的可控性,证明了相比传统飞行器它具有更高的容错性．样机实验测试了该飞行器的大角度复杂机动动作以及推力矢量控制飞行能力,可实现最大70°的倾转悬停．实验结果表明,该飞行器相比于传统的四旋翼飞行器具备更高的机动性．     

Manoeuvring target tracking with coordinated-turn motion using stochastic non-linear filter

Allowing for perturbations in speed and turn rate of a target moving in a coordinated turn obeys a non-linear stochastic differential equation. Existing algorithms for coordinated turn tracking avoid this problem by ignoring perturbations in the continuous time model and adding process noise only after discretisation. The dynamic model used here adds small perturbations, modelled as independent Brownian motion processes, to the speed and turn rate. The target state is to be recursively estimated from noisy discrete-time measurements of the target's range and bearing. In particular, this paper examines the effect of the perturbations in speed and turn rate on the coordinated turn motion of the aircraft, and subsequently the stochastic algorithm is developed by deriving the evolutions of conditional means and variances for estimating the state of the aircraft. By linearizing the stochastic differential equations about the mean of the state vector using first-order approximation, the mean trajectory of the resulting first-order approximated stochastic differential model does not preserve the perturbation effect felt by the moving target; only the variance trajectory includes the perturbation effect. For this reason, the effectiveness of the perturbed model is examined on the basis of the second-order approximations of the system non-linearity. The theory of the non-linear filter of this paper is developed using the Kolmogorov forward equation ‘between the observation’ and a functional difference equation for the conditional probability density ‘at the observation’. The effectiveness of the second-order non-linear filter is examined on the basis of its ability to preserve perturbation effect felt by the aircraft. The Kolmogorov forward equation, however, is not appropriate for numerical simulations, since it is the equation for the evolution of the conditional probability density. Instead of the Kolmogorov equation, one derives the evolutions for the moments of the state vector, which in our case consists of positions, velocities and turn rate of the manoeuvring aircraft. Even these equations are not appropriate for the numerical simulations, since they are not closed in the sense that computing the evolution of a given moment involves the knowledge of higher-order moments. Hence we consider the approximations to these moment evolution equations. Simulation results are introduced to demonstrate the usefulness of an analytic theory developed in this paper.     

多发飞机发动机不对称推力自动补偿方法研究

现有的多发飞机发动机不对称推力自动补偿方法存在着补偿响应速率慢、补偿效果差的弊端,为此提出多发飞机发动机不对称推力自动补偿方法。根据多发飞机发动机失效的实际情况对发动机不对称推力数学模型进行构建,以此为基础,对不对称推力自动补偿控制律进行构造,依据建立的发动机不对称推力数学模型采用不对称推力自动补偿控制律对副翼与方向舵自动补偿增益参数进行计算,实现了多发飞机发动机不对称推力的自动补偿。通过仿真对比实验得到,与现有的多发飞机发动机不对称推力自动补偿方法相比较,提出的多发飞机发动机不对称推力自动补偿方法提升了补偿的响应速率与效果,充分说明提出的多发飞机发动机不对称推力自动补偿方法具备更好的性能。     

逐点线性化后退区间最优控制在飞机非线性控制中的应用

常规线性飞控系统针对推力矢量飞机这样的多控制冗余、非线性MIMO系统,无法实现非线性控制．本文针对推力矢量飞机非线性系统,阐述了一种逐点线性化后退区间最优控制算法满足飞行品质要求．首先将作动器,飞行品质和逐点线性化的飞机线性模型综合实现在线建模,然后以飞行状态与预测状态之间的误差、作动器的位置限制和速率限制作为最优指标,最后以此为基础,根据最优控制原理计算当前时刻飞机最优控制指令,实现飞机非线性控制．采用国内某型号飞机气动数据验证此算法的鲁棒性和稳定性．     

The design of real-time logistics information system for trucking industry

A critical link in the overnight Express Package services is the on-time arrival of trucks at local airport terminals. Truck delays can delay the package sorting process, which can in turn delay aircraft departures from the local terminal, as well as aircraft departures from hub terminals that depend on timely aircraft arrivals. In this paper, the design of a real-time logistics information system (RLIS) for trucking industry was addressed, considering the effects of traffic congestion during rush hour. Two types of forecasting methods, time series models and nonlinear fuzzy reasoning, were created and embedded into the RLIS. The results from practical web services reveal a substantial improvement of the truck scheduling performance and help decision makers determine schedule coordination between ground transportation and aircraft departures at airport cargo terminals.     

一种改进的BP神经网络在飞机燃油系统故障诊断中的应用

将一种改进了的BP神经网络算法应用于飞机燃油系统故障诊断中，仿真验证结果表明，该算法具有诊断速度快、误诊率低的特点；并为开发基于神经网络的飞机燃油故障诊断专家系统奠定了基础。     

Application of solar and wave energies for long-range autonomous underwater vehicles

The solar-powered autonomous underwater vehicle (AUV) may have unlimited autonomous capability in time and be an efficient tool to explore the ocean. The performances of solar powered AUV, evidently, depend on available solar energy. The low efficiency of industrially produced solar panels (10-16%) affords sufficient amounts of energy at low latitudes, but does not at high latitudes of about 60° and more. On the contrary, available wave energy distribution increases with latitude. A similar relation of solar and wave energies occurs regarding their seasonal variations. Hence, the combination of solar and wave energies promises more efficient use of the vehicle at all latitudes over the whole year. Converters of wave energy to electrical energy are usually cumbersome mechanical structures unsuitable for installation on an AUV.In this sense, it is more reasonable to use wave energy to aid the vehicle's motion. In this case a very fortunate situation occurs. It was shown that the best shape for a solar vehicle is a wing. At the same time it is possible to transform wave oscillations to forward movement using three wings, fixed on the hull of the vehicle. In this way, the demands of efficient solar-powered and wave-driven vehicles fully coincide. These relationships are considered in the paper and some resulting data are given.     

Energy-efficient micromolding and in-mold compounding using ultrasonic vibration energy with enhanced material flow

Injection molding is the most widely used polymer processing technology, and uses thermal energy to plasticize thermoplastic polymer pellets. In this study, ultrasonic vibration energy was used to plasticize polymer pellets in micro-injection molding, instead of using conventional thermal energy. An auxiliary flow unit was used to enhance the ultrasonic plasticizing effect and the relevant flow rate. Two rotor types, flat and blade-type rotors, were investigated in terms of flow enhancement capability and the resulting improvement in the quality of the molded parts. As a result, the blade-type rotor showed improvements in flow rate (by 66%) and filling length (by 26.5%). This enhanced material flow in ultrasonic micromolding was then further applied to in-mold compounding and molding by dispersing short carbon fibers (CFs) into polypropylene (PP) pellets during ultrasonic plasticizing. The resulting CF composites showed a 38% improvement in tensile strength compared to pure PP specimens. Considering that this ultrasonic micromolding was performed by a desktop-scale machine with low energy consumption, this process is more efficient for micromolding than the conventional injection molding process.

     

飞机纵向飞行轨迹的优化与实现*

本文研究了飞机纵向飞行轨迹的优化技术,选用质点运动能量状态方程为飞机运动模型,直接操作成本为优化指标函数;飞机纵向飞行剖面被假定分为三个飞行段:爬升、巡航和下降;将能量状态引入指标函数,使其成为哈密顿函数中的独立变量,则由动态变分法和极小值原理得到对各飞行轨迹段的优化算法;尔后用Fibonacci单参数搜索法来予以实现。文中给出了部分仿真结果。     

基于单步最优方法的推力矢量垂直短距飞机过渡过程控制

推力矢量垂直短距起降飞机(V/STOL)具有巡航速度快和起降灵活的特点,近年来受到了广泛的关注.然而,该型飞机需要经历悬停转平飞和平飞转悬停的过渡过程阶段,期间飞机会面临强耦合、强非线性等控制难题,使得传统控制器难以胜任.针对上述问题,通过充分考虑执行器的执行能力,提出一种基于单步最优方法的过渡过程控制策略.所提方法结合推力矢量V/STOL飞机的特点,在确保飞机姿态可控的前提下使飞机水平加速度最大,同时使三轴承推力矢量喷管转角向目标转角不断靠近,从而以最快的速度完成过渡过程,并进行控制器切换.仿真实验验证了所提方法具有过渡过程时间短、姿态平稳的优点.     

倾转旋翼飞行器最优推力矢量控制

最优控制中的线性状态调节器对于一个易受外界扰动的系统来说具有十分重要的作用。飞行器在飞行过程中经常会受到风之类的外界扰动,使其偏离正常运行轨道,因此在设计飞行器的时候,考虑滚动通道和偏行通道的状态反馈调节器对于飞行器的正常飞行来说具有十分重要的意义。基于此,该文对最新发展的双发倾转旋翼飞行器进行了研究,通过建立其数学模型,分析设计了旋翼飞行器的滚动通道和偏行通道的线性状态控制器,最优飞行控制给出了倾转旋翼飞行器的最优矢茸推力控制。分析结果表明：该飞行器具有节省动力能源,机动性能好以及抗干扰能力强等优点。计算机仿真证实丁飞行控制系统的最优性和有效性。     

Variable thrust directional control technique for plateau unmanned aerial vehicles高原型无人机变推力轴线控制技术研究

In order to increase the lift force of the unmanned aerial vehicles (UAV) in plateau areas, the UAV is commonly equipped with high span chord ratio wings. However, it may decrease the maneuverability of the aircraft, and thus increasing the risk of flight in complex terrain regions. Thrust vector control is a direct force flight control technique, which enhances the maneuverability and introduces the residual of the flight control system. In this paper, we develop a novel variable thrust direction mechanism, which provides the normal propeller UAV with the capability of directional force control. We propose a combinational flight control strategy for the newly developed UAV. Simulations and real flight test demonstrate the performance of the proposed technique in increasing the maneuverability of the conventional propeller UAV.     

纵置双涵道式飞行器悬停控制系统设计

涵道风扇较同样直径的螺旋桨能产生更大的升力,且结构紧凑、安全性高、噪音低.以此为推力装置的可垂直起降飞行器具有良好发展前景.但其系统动力学特性是属于多变量、强耦合的非线性系统,在控制系统的设计中必须进行良好的解耦设计纵置双涵道式飞行器的飞行控制系统的控制特征进行了分析,建立基本的控制系统动力学模型,利用模型跟踪解耦自适...     

The centrifugal sudden distorted wave method for calculating cross sections for chemical reactions: Angular distributions for Cl + HCl → ClH + Cl

We describe a method for calculating cross sections for atom plus diatom reactive collisions based on the centrifugal sudden distorted wave (CSDW) approximation. This method is nearly exact at low energies where reactive cross sections are small. Representative CPU times are given for applications of the CSDW method to the Cl + HCl → ClH + Cl reaction using CDC 7600, Cyber 176, Cyber 205, Cray X-MP and Cray-2 computers. We also present differential cross sections for the Cl + HCl reaction and apply a simple semiclassical model which relates these cross sections to the partial wave reaction probabilities, and to the energy dependence of the reaction probabilities for zero total angular momentum. This model explains why the differential cross sections are backward peaked, and why the oscillatory cross sections seen in earlier, more approximate infinite order sudden calculations are not found in the present results at low energy.     

基于Flash CS3的B737飞机起落架刹车系统模拟仿真

起落架刹车系统能在飞机着陆时配合扰流板与反推装置增大飞机的阻力,使之迅速减速,减小滑跑所需距离。运用Flash CS3软件对B737飞机液压动力刹车系统工作原理进行模拟仿真,用逐帧动画和补间动画两种方法将液压的流动方向以动画形式直观展现出来。详细分析了在人工刹车的工作方式下正常刹车、备用刹车和蓄压器刹车三种形式的工作过程。将两种仿真方法进行对比,结果表明:逐帧动画制作简单但表现形式欠佳,补间动画虽过程复杂但结果更加直观形象。针对B737飞机起落架刹车系统工作原理的动画模拟仿真,对刹车系统的学习、维修、研究和改进等具有一定的参考价值。     

On the Interplay of Parallelization, Program Performance, and Energy Consumption

This paper derives simple, yet fundamental formulas to describe the interplay between parallelism of an application, program performance, and energy consumption. Given the ratio of serial and parallel portions in an application and the number of processors, we derive optimal frequencies allocated to the serial and parallel regions in an application to either minimize the total energy consumption or minimize the energy-delay product. The impact of static power is revealed by considering the ratio between static and dynamic power and quantifying the advantages of adding to the architecture capability to turn off individual processors and save static energy. We further determine the conditions under which one can obtain both energy and speed improvement, as well as the amount of improvement. While the formulas we obtain use simplifying assumptions, they provide valuable theoretical insights into energy-aware processor resource management. Our results form a basis for several interesting research directions in the area of energy-aware multicore processor architectures.     

Real-time prediction of unsteady aerodynamics: Application foraircraft control and manoeuvrability enhancement

The capability to control unsteady separated flow fields could dramatically enhance aircraft agility. To enable control, however, real-time prediction of these flow fields over a broad parameter range must be realized. The present work describes real-time predictions of three-dimensional unsteady separated flow fields and aerodynamic coefficients using neural networks. Unsteady surface-pressure readings were obtained from an airfoil pitched at a constant rate through the static stall angle. All data sets were comprised of 15 simultaneously acquired pressure records and one pitch angle record. Five such records and the associated pitch angle histories were used to train the neural network using a time-series algorithm. Post-training, the input to the network was the pitch angle (alpha), the angular velocity (dalpha/dt), and the initial 15 recorded surface pressures at time (t (0)). Subsequently, the time (t+Deltat) network predictions, for each of the surface pressures, were fed back as the input to the network throughout the pitch history. The results indicated that the neural network accurately predicted the unsteady separated flow fields as well as the aerodynamic coefficients to within 5% of the experimental data. Consistent results were obtained both for the training set as well as for generalization to both other constant pitch rates and to sinusoidal pitch motions. The results clearly indicated that the neural-network model could predict the unsteady surface-pressure distributions and aerodynamic coefficients based solely on angle of attack information. The capability for real-time prediction of both unsteady separated flow fields and aerodynamic coefficients across a wide range of parameters in turn provides a critical step towards the development of control systems targeted at exploiting unsteady aerodynamics for aircraft manoeuvrability enhancement.