Optimization of the carrier tracking loop for GPS high dynamic receivers

A carrier tracking loop which can adjust the loop parameters adaptively is proposed for high dynamic application. Three modules, called the α-β-γT filter model, adaptive loop structure mod- el and adaptive loop bandwidth model respectively, are added in the presented tracking loop com- pared with the traditional carrier tracking loop based on the second-order frequency lock loop （FLL） assisting third-order phase lock loop （PLL） loop filter. And the optimization methods for the track- ing bandwidth and the carrier loop order are analyzed. The real-time estimation methods of the dy- namic parameters, the velocity, acceleration and jerk along the line of sight （LOS） between the sat- ellite and the receiver＇ s antenna, and the measurement parameters are discussed based on the pres- ented α-β-γ filter algorithm. A method is introduced to improve the filter＇ s dynamic response to meet high dynamic application by self-adjusted α-β-γ filter coefficient used in the tracking loop. The performance of three cases with different carrier tracking loop is compared by simulation.

Optimization of the seismic processing phase-shift plus finite-difference migration operator based on a hybrid genetic and simulated annealing algorithm

Although the phase-shift seismic processing method has characteristics of high accuracy, good stability, high efficiency, and high-dip imaging, it is not able to adapt to strong lateral velocity variation. To overcome this defect, a finite-difference method in the frequency-space domain is introduced in the migration process, because it can adapt to strong lateral velocity variation and the coefficient is optimized by a hybrid genetic and simulated annealing algorithm. The two measures improve the precision of the approximation dispersion equation. Thus, the imaging effect is improved for areas of high-dip structure and strong lateral velocity variation. The migration imaging of a 2-D SEG/EAGE salt dome model proves that a better imaging effect in these areas is achieved by optimized phase-shift migration operator plus a finite-difference method based on a hybrid genetic and simulated annealing algorithm. The method proposed in this paper is better than conventional methods in imaging of areas of high-dip angle and strong lateral velocity variation.

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.

Optimal control based coordinated taxiing path planning and tracking for multiple carrier aircraft on flight deck

Coordinated taxiing planning for multiple aircraft on flight deck is of vital importance which can dramatically improve the dispatching efficiency.In this paper,first,the coordinated taxiing path planning problem is transformed into a centralized optimal control problem where collision-free conditions and mechanical limits are considered.Since the formulated optimal control problem is of large state space and highly nonlinear,an efficient hierarchical initialization technique based on the Dubins-curve method is proposed.Then,a model predictive controller is designed to track the obtained reference trajectory in the presence of initial state error and external disturbances.Numerical experiments demonstrate that the proposed“offline planningþonline tracking”framework can achieve efficient and robust coordinated taxiing planning and tracking even in the presence of initial state error and continuous external disturbances.

Enabling a Viable Technique for the Optimization of LNG Carrier Cargo Operations

In this study, we optimize the loading and discharging operations of the Liquefied Natural Gas(LNG) carrier. First, we identify the required precautions for LNG carrier cargo operations. Next, we prioritize these precautions using the analytic hierarchy process(AHP) and experts' judgments, in order to optimize the operational loading and discharging exercises of the LNG carrier, prevent system failure and human error, and reduce the risk of marine accidents. Thus, the objective of our study is to increase the level of safety during cargo operations.

Parameter Optimization of Nose Landing Gear Considering Both Take-off and Landing Performance of Catapult Take-off Carrier-Based Aircraft

Optimization of the parameters of landing gear systems with double-stage air springs of catapult take-off carrier-based aircraft is here studied based on the mathematical equations of the classic dual mass spring-damper dynamic model.Certain standards for both take-off and landing performance are put forward.The contradictory factors between take-off and landing processes are analyzed.The optimization of oil in the pin area and the area near the rear oil hole is performed.Then these optimized parameters are used to assess the influence of the initial pressure of the low chamber,the ratio of the high chamber to the low chamber,and the tire inflation pressure on the performance of arresting landing and catapult take-off.The influences of these parameters on carrier-based aircraft and the aircraft-carrier on aircraft catapult take-off is also assessed.Based on the results of the simulation,respective take-off criteria must be drafted considering different types of aircraft and different take-off load cases,all of which must be matched to parameters relevant to catapult take-off.

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.

基于变载波频率的永磁同步电机驱动系统效率优化控制

为降低永磁同步电机驱动系统的损耗,提高系统效率,提出了一种基于母线电流反馈的变载波频率优化控制方法.首先,建立了系统损耗数学模型,探究了载波频率与系统损耗的关系.然后,针对离线优化方法对于参数敏感的问题,设计了一种基于母线电流反馈的载波频率在线寻优方法.结果表明,在不同转速与负载条件下均存在使系统损耗最小的最优载波频率,其随转速与负载条件变化而变化.在各个工作点,系统损耗的计算值均与实测值基本吻合.在线寻优方法在中高负载情况下能够实现约0.6%的效率优化,并且在负载变化的情况下仍然能够实现损耗优化.

面向电力线通信的基于Mitchell算法的OFDM同步检测方法

为了提高电力线通信系统中OFDM定时同步的准确度,文章基于低压电力线宽带载波通信互联互通技术规范下的物理层通信协议,提出了一种基于Mitchell算法的电力线载波通信符号定时算法。与理论本地互相关同步算法相比,文章的算法不需要进行乘法运算,易于硬件实现。与简化的单比特量化算法相比,该算法同步检测结果更加准确,峰值旁瓣更小,在低信噪比条件下符号定时更加准确。

O-OFDM索引调制的分步优化信号映射方法

【目的】采用随机映射以及传统星座图会导致已有光正交频分复用(O-OFDM)-索引调制(IM)系统的误码率(BER)性能无法达到最优,因此,文章基于激活子载波的最优选择以及星座图的最优旋转提出了一种分步优化信号映射方法,旨在通过分步优化信号映射方法实现O-OFDM-IM系统BER性能的改善。【方法】在发射端,首先依据信道状态信息,采用信道范数最大化准则选择最优激活子载波组合;其次,利用信道状态信息,以∂=0.5°为步长,采用穷举搜索算法得到最优星座图;之后,将通过旋转获得的最优星座图加载到激活的子载波上进行信号传输;最后在接收端利用最大似然(ML)检测算法对原始信号进行恢复来实现最小的系统错误概率。【结果】仿真表明,在强湍流、BER=10-4和调制阶数为16的条件下,采用文章所提方法后,(4,2)O-OFDM-IM系统的信噪比(SNR)降低了约1.45 dB。此外,随着湍流强度的增大,BER性能的改善更明显。如,8正交幅度(QAM)、BER=10-4时,(4,2)O-OFDM-IM系统的SNR在强湍流下降低了约1.35 dB,在弱湍流下则降低了1.2 dB。【结论】由仿真结果可知,在已知信道状态信息的前提下,文章所提方法可有效改善湍流信道下系统的BER性能。

基于教与学优化的舰载机起飞出动动态调度

本文针对弹射器故障情形下的舰载机起飞出动调度,建立了舰载机起飞出动的多约束分布式流水线调度模型;结合基于扩展随机序解的编码和解码策略、动态调整策略,设计了基于教与学优化的舰载机起飞出动动态调度算法;最后,通过对仿真案例分析、故障预测精度对动态调度的影响分析,及动态调度算法的运行时间分析,结果验证了所设计的算法对舰载机起飞出动动态调度的可行性和有效性。

工业水处理中的流化床Fenton工艺技术进展

传统Fenton反应产生大量的铁泥,限制了该技术的推广应用。流化床Fenton是将传统Fenton和载体结晶相融合的一项高级氧化技术,在强化催化氧化废水处理效果的同时可以起到削减铁泥的作用。首先,文章从均相反应、非均相反应、载体结晶和技术机理4个方面,全面阐释了流化床Fenton的基本原理。继而,系统性地从载体特性、反应条件(Fenton试剂、pH、床层膨胀率和水基质)以及反应器结构等方面,全面分析了流化床Fenton工艺在废水处理中的关键影响因素。然后,回顾了近年来流化床Fenton工艺在难生物降解性工业废水等处理领域的工程化应用。最后,拓展性地从高效活性载体与耦合技术(光催化和膜生物处理)两方面详细地阐述了流化床Fenton技术优化,并对未来的研究方向和兴趣提出展望和思考。

采煤机搬运车制动系统同步性优化设计

为提高采煤机搬运车制动系统的响应速度,并解决前后车制动同步性差的问题,结合仿真分析对制动系统进行了优化设计。通过计算搬运车制动效能,得出在可优化的参数中,影响制动系统响应速度的主要因素为消除制动器间隙所用时间和制动器制动力增长所用时间;建立制动系统数学模型,通过Simulink仿真计算可知,通过减小非制动工况下制动器摩擦片的间隙,可有效提高制动系统的响应速度。提出背压控制阀组以最大限度地减小摩擦片间隙,通过计算确定背压值最大为1.29 MPa,并通过试验得知背压小于0.9 MPa时,背压控制阀组几乎不起作用,同时为防止搬运车正常行驶时出现制动拖滞现象,将背压值设定为1.2 MPa。通过试验确定背压控制阀组,提高了前后车制动器响应的同步性,试验结果表明:相较于优化前,前后车制动时间差减小为0.24 s,保证了搬运车制动系统的安全运行。最后,通过试验验证了制动系统响应速度的提升,结果表明:常规制动中制动距离为5.2 m,紧急制动中制动距离为3.2 m,均符合MT/T 989—2006《矿用防爆柴油机无轨胶轮车通用技术条件》的技术要求。

甘草酸、姜黄素和羟基喜树碱自组装纳米粒递药系统的工艺优化研究

目的:以两亲性药物分子甘草酸(GA)、疏水性药物姜黄素(CUR)和羟基喜树碱(HCPT)为材料,通过自组装形式构建GA、CUR和HCPT纳米粒递药系统(GA/CUR/HCPT-NPs),考察其制备工艺并进行质量评价。方法:采用反溶剂沉淀法和透析法相结合制备GA/CUR/HCPT-NPs,利用响应面Box-Behnken法对制备工艺进行优化,最终获得尺寸合适,稳定电荷,高载药量的GA/CUR/HCPT-NPs;并对优化出来的GA/CUR/HCPT-NPs进行核磁共振氢谱(1HNMR)、差示扫描量热法(DSC)、高分辨X射线衍射法(XRD)、傅里叶红外分光光度法(FTIR)、紫外分光光度法(UV)等表征和微观形态观察,并测定GA/CUR/HCPT-NPs中GA、CUR和HCPT含量大小。结果:得到的最优处方为去离子水体积30 mL,二甲基亚砜(DMSO)1 min内滴入去离子水,制备温度为40℃,确定GA、CUR、HCPT投药量分别为6.00 mg、10.03 mg、5.01 mg;测量GA/CUR/HCPT-NPs粒径为(146.37±0.15)nm,且带较高的稳定电荷-(34.43±0.77)mV,PDI为0.157±0.01,透射电子显微镜(TEM)和扫描电子显微镜(SEM)可观察到GA/CUR/HCPT-NPs是类球形或球形,并且均匀分布;1HNMR、DSC、XRD等证明了成功自组装成稳定的GA/CUR/HCPT-NPs,并且在7 d内4℃保存条件下稳定性良好;高效液相色谱(HPLC)测定GA/CUR/HCPT-NPs中GA、CUR、HCPT的载药量分别为57.19%、39.17%和3.07%。结论:本研究通过优化的反溶剂沉淀法结合透析法成功制备尺寸合适、均匀分布的GA/CUR/HCPT-NPs,为进一步实验奠定了基础。

双用户分组上行多载波非正交多址接入的能耗最小化

为实现边境地区无线传感网长期工作,采用无人机与非正交多址(Non-Orthogonal Multiple Access,NOMA)技术结合的网络对分布在狭长边境线的传感器进行数据采集,以有效降低无线传感网(Wireless Sensor Networks,WSNs)的能耗。传感器用户组以多载波NOMA方式上传数据至无人机,在最大发射功率、用户服务质量(Quality of Service,QoS)及无人机移动性的约束下,通过优化传感器用户调度和分组、发射功率及无人机轨迹最小化所有传感器总能耗。该优化问题为混合整数非线性优化问题,将其分解为3个子问题求解。利用穷举搜索、拉格朗日对偶分解和逐次凸逼近(Successive Convex Approximation,SCA)依次求解各子问题并迭代优化,得到能耗最小值。仿真结果表明,所提方案可以有效降低无线传感网总能耗。

散货船顶边舱横隔板的拓扑优化设计

针对散货船顶边舱横隔板的设计主要靠母型船和工程师经验进行,以横隔板重量最轻为目标,参照原始设计的应力结果进行基于应力约束的拓扑优化。基于原始设计方案,去除顶边舱横隔板上的开孔面板、防倾肘板和屈曲筋,对结构进行细化后获得响应工况的应力作为拓扑优化的应力约束。分别对单个横隔板进行拓扑优化和对货舱内所有横隔板进行拓扑优化。基于拓扑优化结果,设计新的横隔板开孔方式并进行详细设计,并基于三舱段有限元计算对优化设计进行粗网格和细化分析校核。优化后的构型相对原始设计能获得更轻便的重量和更小的应力结果。本文的研究可以为散货船的拓扑优化、顶边舱横隔板的设计提供参考。

基于弹药挂载工作的舰载机保障作业调度

针对弹药挂载工作下舰载机保障作业问题,分析了弹药挂载作业与舰载机其他保障作业的约束关系,并基于保障资源约束,以舰载机保障作业完成时间和负载方差最小化为优化目标,建立了考虑弹药挂载工作下的保障作业调度模型。通过设计基于保障工序优先级的染色体片段编码方式,避免了大量不可行解的产生,提出了一种改进的NSGA-Ⅱ算法。以国外某型航母为例进行仿真分析,验证了模型与算法所得调度方案的可行性。

基于改进遗传算法的舰载机弹药挂载调度

舰载机弹药挂载工作是舰载机弹药保障中的一个重要环节,传统的舰载机弹药挂载调度通常忽略工作中存在的约束。针对该问题,分析了弹药挂载工作中存在的约束条件,以所有舰载机弹药挂载时间之和为优化目标,建立了考虑舰载机起始挂载时间不同和弹药挂载空间约束的舰载机弹药挂载调度模型,并提出了一种基于染色体片段编码的改进遗传算法,避免了大量不可行解的产生,提高了算法求解效率。仿真分析验证了所提模型与算法所得弹药挂载调度方案的可行性。

基于载波重构的CHB多电平逆变器的功率均衡方法

针对级联H桥(cascaded H-bridge,CHB)九电平逆变器在传统载波移幅调制下四个单元输出功率不均衡的弊端,提出了一种基于载波重构改进的功率均衡策略,该策略可以有效减少载波数量,通过二次功率均衡处理,实现了级联H桥九电平逆变器四单元间的输出功率均衡.首先通过载波重构方式实现四单元间两两功率均衡,再通过对开关管的驱动信号进行1/4周期逻辑互换后得到开关管的实际驱动信号,从而实现全调制度下全单元功率均衡.仿真和实验结果表明,该策略能够在有效减少载波数量的基础上实现四个级联H桥单元的功率均衡.

基于IPSO的舰载机出动离场规划研究

针对舰载机机群出动离场效率问题,提出了一种改进的粒子群优化(improved particle swarm optimization, IPSO)算法。首先,基于舰载机的出动离场流程及约束建立了舰载机出动离场数学模型,并根据出动离场问题特点设计了一种连续编码形式以表示出动规划方案。然后,通过在参数自适应粒子群优化算法的基础上引入基于莱维飞行扰动的模拟退火机制,提出了将IPSO用于对出动离场规划问题进行求解。最后,分别针对8、10、12机的出动离场规划场景进行了仿真验证。仿真结果表明,所提算法较已有的优化算法而言具有更好的寻优能力。