Features of active sidestick controllers

This paper discusses the advantages of incorporating active sidesticks into a modern aircraft cockpit. Active sidestick controllers for manual pilot inputs in pitch and roll are examined for commercial transport aircraft. Options and requirements for sidesticks are reviewed. The recommendation of an active sidestick controller is developed providing both cross-cockpit coupling and autopilot backdrive capability. These characteristics provide pilot cues identical to traditional cable-linked column/yoke configurations     

采用被动侧杆的民机设计中的人为因素考虑

与中央杆/盘或主动侧杆相比,被动侧杆的最大缺陷在于缺乏反驱装置,进而产生人-机交互信息以及主/副驾交互信息的缺失,增加了人为差错的出现概率;被动侧杆由于缺乏力反馈,会造成飞行员对触觉这一最直接信息的缺失,进而影响人-机操纵权限的分配。在民机设计中,可以考虑在被动侧杆上添加模式切换按钮,从而在保持飞行员超控权限和提供有效包线保护这两者间找到最佳平衡点。被动侧杆由于缺乏反驱装置,无法实现左、右侧杆的联动,因此更容易出现叠加操纵。在民机设计中,应当从视觉、听觉、触觉全方位对叠加操纵进行提示,同时借鉴已有的接替操纵操作程序,以提高飞行员的适应性。     

微扰法配合网络分析仪测试材料的电磁参数

利用网络分析仪连接矩形谐振腔组成材料电磁参数的微扰法测试系统。并根据谐振腔微扰理论,得到小样品装载在样品托中进行电磁参数测试的复介电常数和复磁导率计算公式。对聚四氟乙烯的电磁参数进行了测试,所得结果较为精确,可重复性好,证明此测试系统测试结果稳定可靠。对本测试装置的误差进行了简要分析,指出该测试装置能够满足一般电介质材料,尤其是吸波材料电磁参数的测试需求。     

Variable frequency switching in power supply EMI-control: an overview

Spreading the signal spectrum is a widely used technique in telecommunication applications. Variable-frequency and spread spectrum modulation methods can also be utilized in power electronic applications to improve electro-magnetic compatibility (EMC). This paper gives an overview to variable-frequency techniques in power electronics with experimental results.     

电（磁）涡流技术在振动疲劳试验中的应用

根据电（磁）涡流技术研制出一种新型振动疲劳试验设备,其工作频带宽、高频特性好。系统中引进串联电容谐振方案,显著地提高了能量利用,大大降低了功率消耗。在疫劳试验技术方面开创了一种新的激振方法。 本文阐明了电（磁）,涡流激振的工作原理,性能特点,叙述了磁路分析与结构设计、电容谐振方案、振幅自动挂制与遥控监测等。最后,介绍了用该设备对发动机叶片进行振动疲劳试验,其结果是令人满意的。     

称重仪表电磁兼容性能的改进

针对称重仪表中出现的电磁兼容性问题进行讨论，并采取了相应的措施，对其进行了改进。     

采用微扰法测试碳泡沫的电磁参数

利用网络分析仪连接矩形谐振腔组成材料电磁参数微扰法测试系统。由谐振腔微扰理论出发,得到以托管装载小样品测试时复介电常数和复磁导率的计算公式。对碳泡沫进行电磁参数测试。结果表明,随着碳泡沫电导率的增加,其介电常数缓慢增加,电损耗先增加后减小,而磁损耗不断增加。碳泡沫具有介电常数小、电损耗大、随电导率增加而增加的非本征磁损耗,这种独特的电磁损耗特征使得碳泡沫有用作宽频带高温结构吸波材料的可能性。     

Random signal radar - a winner in both the military and civilian operating environments

Besides some general requirements, modern military radars should possess excellent LPI (low probability of intercept) properties. And civilian radars should satisfy the rigorous requirement of EMC (electro-magnetic compatibility) performance. The special features of random signal radar are analyzed here based on the different requirements for military and civilian use. Results show that random signal radar has excellent LPI property and EMC performance simultaneously, which can satisfy both military and civilian requirements.     

铝铜点焊的研究

提出了铝铜过渡接头的点焊新方法,用交流焊机点焊铝铜,解决了Al2O3氧化膜层的破碎问题。从而可利用热活化、压力、电磁搅拌力,使铝铜固溶,扩散和铝液面移动,完成铝铜点焊,获得比铝强度高的焊接接头,为铝代铜的运用提供了一种特殊的途径。     

具有电磁约束阻尼层梁的振动主动控制研究计算(英文)

This paper investigates vibration control of beam through electro-magnetic constrained layer damping （EMCLD） which consists of electromagnet layer, permanent magnet layer and viscoelastic damping layer. When the coil of the electromagnet is electrified with proper control strategy, the electromagnet can exert magnetic force opposite to the direction of structural deformation so that the structural vibration is attenuated. A mathematical model is developed based on the equivalent current method to calculate the electromagnetic control force produced by EMCLD. The governing equations of the system are obtained using Hamilton＇s Principle and then reduced with the assumed-mode method. A simulation on vibration control of a cantilever beam is conducted under the velocity proportional feedback to demonstrate the energy dissipation capability of EMCLD, and the beam system with the same parameter is experimented. The results of experiment and simulation are compared and the results show that the EMCLD is an effective means for suppressing modal vibration. The results also indicate that the beam system has better control performance for larger control current. The EMCLD method presented in this paper provides an applicable and efficient tool for the vibration control of structures.     

Identification of Voltage Transients on Aircraft Cabling under LTA Excitation

Lightning and electro-magnetic pluse-induced fuselage skin currents can magnetically or electrically flux couple onto air-craft cabling through dielectric "holes" or apertures in the aircraft fuselage. Using lightning transient analysis (LTA) input-output waveform records, frequency domain techniques are presented that locate the exact point of excitation. The techniques are demonstrated using an RG-58 cable simulation and are then applied to the yaw damper circuit of a USAF F-111.     

一种新型激振设备的设计与试验研究一对无限宽板的激振

 根据电(磁)涡流技术研制出一种新的非接触式激振设备。其测试精度高、噪音低,结构简单。为航空、航天,船舶,汽车等工程中无限宽板或周边固持板类构件的测振试验提供了一种新的激振方法。 本文介绍了导电(磁性或非磁性)试件激振的工作原理和性能特点及该激振器的结构设计和磁路分析。用该设备对圆板和方板进行的实际激振,效果良好。     

电磁控制涡激振荡的实验研究

利用电介质溶液中圆柱体侧表面附近分布的电磁场产生电磁力可有效改变流体边界层及尾涡结构。本文以减振为目标,对电磁力控制涡激振荡进行了实验研究。实验在转动水槽中进行,通过吊杆将装有电磁激活板的圆柱插在槽内液体中。吊杆上的应变片用于测试圆柱的升力,注入适当的染料用来显示流场。结果表明：对称电磁力作用下,脱体涡被抑制,从而使升力的振荡受到有效抑制,进而抑制圆柱的振动,双排方向相反的涡变为单排正负交错的涡。当电磁力足够大时,圆柱的振荡被完全消除,流场达到定常。     

压气机叶片的振动疲劳特性

首次报道了关于采用11CrNi2MoVA材料制造的某型航空发动机压气机第3级叶片振动疲劳特性的研究。结果发现:(1)叶片振动疲劳破坏模式随使用寿命增加而变化。新叶片的破坏位置在叶背最大应力点附近处,而随着使用寿命的增加,叶片破坏位置转向进排气边缘。(2)叶片振动疲劳强度随使用寿命增加而逐渐下降。采用升降法对新叶片、200小时、400小时叶片的实验结果证实了这一点。(3)采用现行方法对叶片的维修有利于叶片疲劳强度的恢复。对使用寿命为400小时的未维修叶片和已完成维修叶片的对比实验表明,维修可使叶片疲劳强度提高,但叶片破坏位置仍在叶片的进排气边缘。      

一种模块化航空有源滤波器的研究

 航空有源滤波器(AAPF)是解决飞机供电系统中电能质量问题的一种先进方案,而模块化设计对航空有源滤波器灵活性、可维护性和可靠性的提升作用巨大。首先提出并研究了一种新型模块化航空有源滤波器,分析了主电路数学模型及其混合载波PWM(CH-PWM)调制方式;其次基于损耗对比分析进行了主电路拓扑优化,推导了模块均压控制律并给出了系统控制策略;最后进行了仿真和实验验证。结果表明,模块化航空有源滤波器能够有效补偿航空电网中由典型非线性负载产生的谐波和无功电流分量,三相电网电流的总谐波畸变率(THD)均在5%以下,补偿效果显著。     

Active Control Law Design for Flutter/LCO Suppression Based on Reduced Order Model Method

 Active stability augmentation system is an attractive and promising technology to suppress flutter and limit cycle oscillation (LCO). In order to design a good active control law, the control plant model with low order and high accuracy must be pro-vided, which is one of the most important key points. The traditional model is based on low fidelity aerodynamics model such as panel method, which is unsuitable for transonic flight regime. The physics-based high fidelity tools, reduced order model (ROM) and CFD/CSD coupled aeroservoelastic solver are used to design the active control law. The Volterra/ROM is applied to constructing the low order state space model for the nonlinear unsteady aerodynamics and static output feedback method is used to active control law design. The detail of the new method is demonstrated by the Goland+ wing/store system. The simu-lation results show that the effectiveness of the designed active augmentation system, which can suppress the flutter and LCO successfully.     

Electromagnetic Effects of Aircraft Wake-Active Feuillet Interaction

A mechanism by which an aircraft wake can interact strongly with the electromagnetic radiation present in an active elevated anomalous refractivity region (active feuillet) is analyzed. The aircraft wake structure, assumed to consist of twin contrarotating vortices plus entrained irrotational gas, trailing behind the wings of typical large aircraft is shown to be capable of descending a distance of approximately 3 wing span distances and attaining a length of the order of 10 km, prior to instability-induced disruption. The parcel of air such a descending coherent wake structure can convey into an active feuillet is demonstrated to alter significantly the local refractive index of the duct and induce substantial radiation spillage. The general characteristics of the electromagnetic radiation produced by this interaction process (i.e., scattering by diaphanous objects) is described.     

Variable structure control and active vibration suppression of flexible spacecraft during attitude maneuver

This paper presents a new approach to vibration reduction of flexible spacecraft during attitude maneuver by using the theory of variable structure control (VSC) to design switching logic for thruster firing and lead zirconate titanate (PZT) as sensor and actuator for active vibration suppression. The spacecraft to be investigated is a hub with a cantilever flexible beam appendage, which can undergo a single axis rotation. The proposed control system includes the attitude controller acting on the rigid hub, designed by variable structure control technique, and the surface-bonded PZT patches for active vibration suppression of flexible appendages, designed by the positive position feedback (PPF) control technique. To avoid chattering, pulse-width pulse-frequency (PWPF) modulation is adopted for the thruster control, which makes the thrusters to be operated in a close to linear manner and also can suppress the relatively large amplitude vibrations excited by, for example, rapid maneuver. However, some residual micro-vibrations still exist due to the switching actions. Upon that, the technique of active vibration control using PZT is turned on to provide further vibration suppression of the residual micro-vibrations and fine tuning of the system performance. By combining the advantages of both these control strategies, an improved performance for vibration control in both the macro-and micro-senses can result. Both analytical and numerical results are presented to show the theoretical and practical merit of this approach.     

Control of a decelerating boundary layer. Part 1: Optimization of passive vortex generators

The control of boundary layer separation on the suction side of an airfoil at high angle of attack has been renewed by the possibilities of active control. Nevertheless, such an active control needs a deep understanding of the flow to manipulate and of the actuating flow, both being 3D and unsteady. For that purpose, a model experiment has been designed in the frame of a coordinated European project called AEROMEMS, with a simpler (2D) geometry and with a dilatation of the scales in order to be able to characterize the actuation flow. This model is a bump in a boundary layer wind tunnel, which mimics the adverse pressure gradient on the suction side of an airfoil at the verge of separation. The present contribution describes preliminary tests done to optimize standard passive devices before testing active systems. The optimization was done with hot film shear stress probes, the characterization with hot wire anemometry and PIV. The results show quantitatively the improvement brought by the passive devices in terms of skin friction. They also show the mechanism which is at the origin of this improvement. The next step of the project is to replace passive devices by synthetic jets.