H_∞ Preview Control for Automatic Carrier Landing

This paper focuses on the application of H_∞preview control in automatic carrier landing system(ACLS)for carrier-based aircraft.Due to the mutual movement between aircraft and carrier,the landing process becomes considerably more challenging compared to a conventional runway landing.ACLS systems mitigate this by predicting deck motion and generating ideal glide slope path for tracking.Although,this predicted glide slope information is available in advance,conventional control structures are still unable to use this future information.H_∞preview control has the ability to utilize this future information for improving tracking response and disturbance rejection.The process of incorporating preview information into ACLS framework and synthesizing the H_∞preview controller is presented.The methodology is verified using the example of F/A-18 automatic carrier landing problem and results are presented.

Low Crosstalk Three-Color Infrared Detector by Controlling the Minority Carriers Type of InAs/GaSb Superlattices for Middle-Long and Very-Long Wavelength

We report a type-Ⅱ InAs/GaSb superlattice three-color infrared detector for mid-wave （MW）, long-wave （LW）, and very long-wave （VLW） detections. The detector structure consists of three contacts of NIPIN architecture for MW and LW detections, and hetero-junction NIP architecture for VLW detection. It is found that the spectral crosstalks can be significantly reduced by controlling the minority carriers transport via doping beryllium in the two active regions of NIPIN section. The crosstalk detection at MW, LW, and VLW signals are achieved by selecting the bias voltages on the device. At 77K, the cutoff wavelengths of the three-color detection are 5.3μm （at OmV）, 141μm （at 300mV） and 19μm （at -20mV） with the detectivities of 4.6xlO11 cm.Hzl/ZW-1, 2.3×10^10 cm.Hzl/2W-1, and 1.0×10^10cm.Hzl/2W-1 for MW, LW and VLW. The crosstalks of the MW channel, LW channel, and VLW channel are almost 0, 0.25, and 0.6, respectively.

Automatic Carrier Landing Control for Unmanned Aerial Vehicles Based on Preview Control

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.

Guidance and Control Techniques of Carrier-Based Aircraft for Automatic Carrier Landing

We summarize the guidance and control techniques of automatic carrier landing for carrier-based aircraft.First,we analyze the carrier landing operations of the manned fixed-wing aircraft,unmanned fixed-wing aircraft and helicopters.Second,we look into the navigation and guidance system and the flight control methods for current different aircraft.Finally,we draw several conclusions of the development prospects for aircraft carrier landing,including the precision landing control techniques,precision approach and landing guidance techniques,and adaptive,reconfigurable and intelligent flight control techniques.

Optimal Preview Control for Automatic Carrier Landing System of Carrier-Based Aircraft with Air Wake

Carrier-based aircraft carrier landing is a special kind of tracking control problem and not suitable for classical control methods,which may miss the desired performance or result in overdesign.Therefore,we present an optimal preview control for automatic carrier landing system(ACLS)by using state information of system,as well as future reference information,which can avoid the shortcomings of classical control methods.Since the flight performance of carrier-based aircraft is disturbed by air wake when the aircraft flies near the area of carrier stern,we design a disturbance rejection strategy to ensure that aircraft track the glide path with high precision and robustness.Further,carrier-based aircraft is a complex nonlinear system.However,the nonlinear model of carrier-based aircraft can be linearized at equilibrium landing state and decoupled into the longitudinal model and the lateral model.Therefore,an optimal preview control system is designed.The simulation results of a carrier-based aircraft show that the optimal preview control system can effectively suppress air wake.Tracking accuracy of optimal preview controller is higher than that of the proportional integral differential(PID)control system.

Study of the EAST Fast Control Power Supply Based on Carrier Phase-Shift PWM

EAST （experimental advanced superconducting tokamak） fast control power supply is a high-capacity single-phase AC/DC/AC inverter power supply, which traces the displacement signal of plasma, and excites coils in a vacuum vessel to produce a magnetic field that realizes plasma stabilization. To meet the requirements of a large current and fast response, the multi- ple structure of the carrier phase-shift three-level inverter is presented, which realizes parallelled multi-inverters, raises the equivalent switching frequency of the inverters and improves the per- formance of output waves. In this work the design scheme is analyzed, and the output harmonic characteristic of parallel inverters is studied. The simulation and experimental results confirm that the scheme and control strategy is valid. The power supply system can supply a large current, and has a perfect performance on harmonic features as well as the ability of a fast response.

单相级联型多电平变换器直流纹波电压分析及抑制策略

级联H桥型多电平变换器采用移相变压器+整流供电时具有功率因数高、输出电压谐波含量低等优点,在大功率工业领域范围内得到了广泛应用。传统的调制算法都以假设直流母线电压恒定为前提,然而在直流侧会出现低频纹波并被调制和传输到负载,导致输出电压波形畸变。目的为了探讨级联H桥单元供电侧存在大量直流纹波电压导致输出负载电压波形畸变的问题,方法本文首先采用双重傅里叶理论分析直流纹波电压,在此基础上引入一种直流纹波前馈补偿策略,通过测量每个级联H桥的直流侧实际输入电压除以电压基准值并与传统载波信号相乘,进而与调制电压进行载波移相调制;同时采用矢量控制,通过FFT变换虚拟出无功电压,以获得更快的收敛速度、更高的稳定性和更小的振荡。结果仿真和实验结果表明,所提调制算法和控制策略可有效抑制负载电压中的低次谐波,减小输出电压波形畸变,实现逆变电源的快速动态响应和无稳态误差控制。结论实验结果验证了本文所采用的调制策略和控制策略的可行性与合理性。

不同海况条件下舰载无人机着舰安全分析

针对无人机上舰的使用需求,本文对舰载无人机着舰开展了系统的研究。建立了机-舰-环境综合模型和舰载无人机全自动着舰引导控制系统;基于建立的舰载无人机着舰综合模型对不同海况下的着舰过程进行仿真分析,研究不同海况条件以及航母不同航速和遭遇角对着舰安全的影响。仿真研究表明:在复杂海况下,航母可通过适当提高航速以获得更高的着舰成功率,但过高的航速会导致舰尾流扰动加剧,使得着舰成功率显著下降;通过对仿真结果进行统计分析,给出了不同海况下的着舰安全范围,为无人机着舰辅助决策提供参考。

基于PolM的微波光子线性优化链路

文中提出一种利用偏振调制器(PolM)提高系统无杂散动态范围(SFDR)的方案,并进行了仿真验证。实现线性优化的原理是通过对微波光子链路中上下两路光载波进行完全抑制和部分抑制,使生成不同来源的三阶交调失真(IMD3)在电域实现自抵消。仿真结果表明,IMD3的抑制比可达到61.9 dB,系统的三阶无杂散动态范围可达到107 dB·Hz^(2∕3)。该方案具有结构简单、实施难度低、大工作带宽和大动态范围的优势,在宽带无线通信、雷达、电子战系统中具有较大的应用潜力。

室内VLC-WiFi异构网络中多色载波资源分配

可见光通信接入点(VLC AP)在室内密集部署的方式在扩大VLC-WiFi系统容量的同时,增加了覆盖的小区间干扰。为了降低小区间干扰,提高系统的吞吐量和平均用户满意度,本文设计了多色载波分配与功率控制(MCAPC)的资源分配方法。该方法依据VLC AP的部署位置和信道特性,采用软频率复用方法确定各VLC AP的无干扰的主载波和多色副载波,并设计基于匹配博弈的载波和子频带分配算法为用户分配异构网络的频带资源;最后,设计基于功率控制效用值的干扰抑制的载波功率控制算法进一步抑制小区间干扰。研究结果表明,所提MCAPC方法能够提高室内多色VLC-WiFi异构网的系统吞吐量和用户的平均满意度。

高速低载频比传感信号下的逆变器有源阻尼自适应控制

逆变器工作在高频运行和控制载波比低的情况下,存在谐振尖峰抑制,提出了高速低载频比传感信号下的逆变器有源阻尼自适应控制技术。在高速低载频比传感信号下,构建逆变器数学模型。输出电流到电容电压与定子电流之间的传递函数,将逆变器的有源阻尼等效成一个控制电压环。调整有源阻尼自适应控制回路的参数,制定逆变器有源阻尼自适应控制策略。实验结果表明:文中技术的稳定裕度由2.46 dB下降至1.18 dB,可以保证逆变器的稳定运行;在不同采样频率下,可以控制逆变器输出与电网电压相同相位和频率的并网电流,其中在采样频率为5.9f时,输出并网电流和电压均表现为正弦状态,波动范围分别为[35 A,58 A]和[185 V,225 V],具有较好的控制效果。

功能化纳米农药载药系统研究进展

纳米材料因其粒径小、尺寸易调节、种类丰富以及良好的移动性等优势,作为有效载体,在农药载药系统及农业病虫害防治方面受到了广泛关注。纳米材料与技术在提升农药生物利用度、溶解性和缓控释特性等方面展现出巨大的潜力。本文总结了利用纳米材料与技术开发具有功能化纳米农药载药系统的研究进展,系统综述了精准释放农药活性成分的智能响应型农药控释制剂、叶面亲和型、土壤用药型及农药双载体系等不同功能化纳米农药载药系统,概述了其在农药减量增效和精准施用方面的作用效果,并对功能化纳米农药载药系统的应用场景与产业化潜力进行了展望。

机载多载频频控阵非均匀距离模糊杂波抑制方法

机载雷达下视工作面临严重的地海杂波,雷达平台运动造成杂波多普勒频率严重扩散,将微弱目标完全淹没。空时自适应处理(space time adaptive processing,STAP)技术通过联合多天线脉冲的接收信号,能够有效地抑制杂波,实现运动目标检测。对于非正侧视阵列高速平台雷达,杂波距离依赖和距离模糊严重制约着目标检测性能。基于多载频频控阵,通过发射一组载频不同的正交信号,在杂波回波中,获得新的发射维自由度,并根据不同模糊在发射维的差异分离各模糊区域。此外,通过进一步对分离后的近程进行杂波补偿,利用降维STAP实现杂波抑制。仿真结果验证了所提方法的有效性。

基于电力载波与云计算的视频监控系统设计

针对目前视频监控系统不断升级改造存在的布线工作量大、布线成本高、无法存储及计算海量视频文件的问题,该文提出基于电力载波技术和云计算框架的视频监控系统。视频数据经过调制解调、振荡、放大、耦合等过程,利用电力线网络传输到各分控点,通过互联网传送到云端,利用云端强大的存储、计算能对视频数据进行各种处理。设计中硬件部分的ARM11微处理器主要负责视频数据的采集、编码并封包传送到PLC调制解调模块,完成数据收发控制和系统任务调度。软件部分主要包括开发系统搭建、USB摄像头驱动、视频数据采集、LCD实时显示、网络传输和双核数据处理等。该文的设计充分结合电力载波和云计算的特点,在视频监控领域中具有较高的应用价值。

MAGIC CARPET着舰控制的稳定性

魔毯(MAGIC CARPET)是美国最近几年非常成功的舰载机着舰控制技术,是未来主要的着舰方式。研究了MAGIC CARPET控制的稳定性。首先,分析MAGIC CARPET着舰和常规着舰的控制结构。然后,进行人在环实时仿真实验,实验有MAGIC CARPET控制和常规控制两组,每组中又分油门不动和自动油门接通两种情况。实验显示稳定能力(轨迹稳定性、轨迹可控性、速度稳定性、迎角稳定性),从高到低的排序是:MAGIC CARPET控制(正常有自动油门情况)?MAGIC CARPET控制(油门不动情况)?常规控制(正常有自动油门)?常规控制(油门不动情况),可见MAGIC CARPET的稳定性能非常优秀。最后,从D-V曲线、信号流图、复域等多角度,综合分析了MAGIC CARPET控制和常规控制的稳定性机理。研究结果可为飞机着舰和直接力控制等方面提供参考。

球形γ-Al_(2)O_(3)孔结构及其水热稳定性调控策略

负载型催化剂广泛应用于石油化工和精细化工等重要领域,其中载体作用极为关键。多孔球形氧化铝载体具有晶型众多、孔结构优异、化学性质稳定等优点,在工业载体中所占份额最大,然而其性能与相应的孔结构及其水热稳定性息息相关。该文总结了国内外在球形γ-Al_(2)O_(3)孔结构及其水热稳定性调控策略方面的研究进展,着重从球形γ-Al_(2)O_(3)前驱体、油氨柱成型过程及其后处理三方面分析了载体孔结构调控规律,从氧化铝孔结构水热稳定性调控机制及其增强手段,如表面羟基钝化和γ-Al_(2)O_(3)含量总结了其调控策略,对国内高端球形氧化铝工业载体的未来发展提出了建议。

地中海贫血携带者筛查及防控专家共识

地中海贫血是一种遗传性血液病,也是我国罕见病中最常见的类型。地中海贫血可以分为α型、β型、δβ型和δ型4种类型,其中以β型和α型地中海贫血较为常见。其遗传模式均为常染色体隐性遗传。通过开展地中海贫血携带者筛查及防控,能够有效降低该病的发生率。因此,制定了该专家共识。该共识重点关注了地中海贫血携带者筛查的筛查方法、筛查流程及防控等内容,旨在指导及规范临床医师和实验室人员的临床实践。

高速磁浮背靠背三电平ANPC变流器中点电压偏移机理与协同控制策略

高速磁浮交通牵引变流器采用24 MVA背靠背三电平有源中点钳位拓扑,其中两台整流器和两台逆变器共用直流母线。该文分析整流侧和逆变侧在不同功率因数下中点电压(neutral point voltage,NPV)偏移机理及不同电压矢量对NPV的具体影响。据此,针对高速磁浮逆变器并联和串联两种模式,建立NPV偏移模型,得到在调制比和功率因数同时变化时NPV的可控区域。为在全速范围保证NPV平衡,提出一种基于平移调制波的协同控制策略。为减轻整流器功率因数和调制比对NPV的影响,采用一种具有相电压半波对称性的载波脉宽调制,并证明其具备NPV自平衡能力。仿真和硬件在环实验表明,所提策略具有NPV恢复到平衡状态所需时间短、可控范围大等优点,可在高速磁浮全速工况下保证NPV平衡。

低载波比下基于状态反馈和大林算法的永磁同步电机高性能电流控制策略

受到功率器件开关频率的限制,高速永磁同步电机驱动系统通常需要低载波比运行,此时系统延时相对很大,对电流环设计要求很高。常规在连续域设计的复矢量PI控制器由于离散化实现存在误差,dq轴解耦不完全,而且扰动传递函数包含电机自身低阻尼比极点,使系统抗干扰能力差,尤其是负基波频率附近的扰动。因此,文中提出状态反馈大林控制算法。首先,利用延时环节电压进行反馈来使系统完全解耦;然后,通过输出电流反馈提升系统阻尼来抑制扰动;最后,对解耦且阻尼后的系统设计大林控制器来提升稳定裕度。实验结果表明,相较于复矢量PI控制器,所提出的状态反馈大林控制器dq轴解耦性能好,电流超调小,系统振荡小,且抗扰能力显著提升。