Acquisition,Pointing and Tracking System for Shipborne Space Laser Communication without Prior Information

A space laser communication acquisition,pointing and tracking(APT)system based on the beacon laser is designed without prior information.And then,a new target scanning method and a pointing and tracking algorithm are proposed.The target scanning mode is the round-trip triangular wave scanning,and it means that scanning track of the PAN-TILT platform follows the triangular wave repeatedly.For the pointing and tracking algorithm,the beacon laser is used as the auxiliary aiming light source.The position of the beacon laser in the viewfield of the complementary metal oxide semiconductor(CMOS)camera is calculated by the centroid algorithm.In order to realize the target tracking,the joint control method of the angle control and the angular velocity control is used.The simulation and experimental results show that the APT system can achieve full coverage scanning in the scanning area and capture the target in one scanning cycle successfully.After capturing the PAN-TILT platform,the pointing and tracking algorithm can track the PAN-TILT platform quickly and accurately,and the tracking accuracy is up to 0.22 mrad.

Method of Carrier Acquisition and Track for HAPS

This paper emphasizes on the characteristics and schemes of carrier acquisition and track in high dynamic and high information-rate situation. Carrier acquisition model is analyzed theoretically and the design princi-ple of carrier acquisition is deduced and described clearly. An algorithm for carrier acquisition in high dy-namic and high information-rate situation is provided. This paper also proves the validity of the algorithm and design scheme in high dynamic and high information-rate situation.

Machine-vision-based acquisition,pointing,and tracking system for underwater wireless optical communications

Due to the proliferation of underwater vehicles and sensors,underwater wireless optical communication(UWOC)is a key enabler for ocean exploration with a strong reliance on short-range bandwidth-intensive communications.A stable optical link is of primary importance for UWOC.A compact,low-power,and low-cost acquisition,pointing,and tracking(APT)system is proposed and experimentally demonstrated to realign the optical link within 0.04 s,even when the UWOC transmitter and receiver are in relative motion.The system successfully achieves rapid auto-alignment through a 4 m tap water channel with a relatively large number of bubbles.Furthermore,the required minimum illumination value is measured to be as low as7.1 lx,implying that the proposed APT scheme is robust to dim underwater environments.Meanwhile,mobility experiments are performed to verify the performance of the APT system.The proposed system can rapidly and automatically align moving targets in complex and unstable underwater environments,which can potentially boost the practical applications of UWOC.

Continuous-Wave Interference Mitigation for Acquisition Method in Unified Carrier TT&C Systems

An interference mitigation for acquisition method,based on both energy center and spectrum symmetry detection,has been proposed as a possible solution to the problem of signal acquisition susceptibility to continuous-wave interference(CWI)in unified carrier telemetry,tracking,and command(TT&C)systems.With subcarrier modulation index as a priori condition,the existence of CWI is determined by comparing the energy center with the symmetric center.In the presence of interference,the interference frequency point is assumed and culled;sequentially,the spectral symmetry is used to verify whether the signal acquisition is realized.Theoretical analysis,simulations,and experimental results demonstrate that the method can realize the acquisition of the main carrier target signal with an interference-to-signal ratio of 31 dB,which represents an improvement over the existing continuous-wave interference mitigation for acquisition methods.

Neutron Flux Signal Acquisition from Plant Instrumentation Channel of Research Reactor for Reactivity Calculation

A design for instantaneous neutron flux signal acquisition system is being carried out for reactivity measurement of the nuclear research reactor. It is a computer-based digital data acquisition system that can perform continuous monitor and measurement of reactivity inserted into or removed from the research reactor. The acquisition system accomplishes with two major parts. The first part is an interfacing PCI based data acquisition card and the corresponding driver software intending to on-line acquisition of neutron flux signals from plant instrumentation channel. The second part incorporates the high-level Visual Basic real time program, indigenously developed for computation of reactivity by the solution of neutron point kinetic equations and other relevant functional modules like input file logging, reactivity calculation, graphics demonstration etc.

Research and Implementation of Beidou-3 Satellite Multi-Band Signal Acquisition and Tracking Method

A new acquisition and tracking method is proposed for signal processing under the new signal system structure of Beidou-3 navigation satellite system(BDS-3). By starting with the analysis of the characteristics and signal structure of the new signal, the local replica of the ranging code and the study of the characteristics of the ranging code are completed, which proves that the method in this paper can be used in the subsequent acquisition and tracking process. The fast Fourier transformation(FFT) search based on longer coherence time and the adaptive phase-frequency switching carrier tracking loop are proposed for signals in different modulation modes. The actual signal of Beidou-3 satellite is sampled by local experiment, and the acquisition and tracking of the Beidou-3 satellite multi-band signal is finally completed. The tracking results verify the feasibility of the proposed acquisition and tracking method.

Research on the MPPT of Photovoltaic Power Generation Based on Improved WOA and P&O under Partial Shading Conditions

Partial shading conditions(PSCs)caused by uneven illumination become one of the most common problems in photovoltaic(PV)systems,which can make the PV power-voltage(P-V)characteristics curve show multi-peaks.Traditional maximum power point tracking(MPPT)methods have shortcomings in tracking to the global maximum power point(GMPP),resulting in a dramatic decrease in output power.In order to solve the above problems,intelligent algorithms are used in MPPT.However,the existing intelligent algorithms have some disadvantages,such as slow convergence speed and large search oscillation.Therefore,an improved whale algorithm(IWOA)combined with the P&O(IWOA-P&O)is proposed for the MPPT of PV power generation in this paper.Firstly,IWOA is used to track the range interval of the GMPP,and then P&O is used to accurately find the MPP in that interval.Compared with other algorithms,simulation results show that this method has an average tracking efficiency of 99.79%and an average tracking time of 0.16 s when tracking GMPP.Finally,experimental verification is conducted,and the results show that the proposed algorithm has better MPPT performance compared to popular particle swarm optimization(PSO)and PSO-P&O algorithms.

Probabilistic Global Maximum Power Point Tracking Algorithm for Continuously Varying Partial Shading Conditions on Autonomous PV Systems

A photovoltaic (PV) string with multiple modules with bypass diodes frequently deployed on a variety of autonomous PV systems may present multiple power peaks under uneven shading. For optimal solar harvesting, there is a need for a control schema to force the PV string to operate at global maximum power point (GMPP). While a lot of tracking methods have been proposed in the literature, they are usually complex and do not fully take advantage of the available characteristics of the PV array. This work highlights how the voltage at operating point and the forward voltage of the bypass diode are considered to design a global maximum power point tracking (GMPPT) algorithm with a very limited global search phase called Fast GMPPT. This algorithm successfully tracks GMPP between 94% and 98% of the time under a theoretical evaluation. It is then compared against Perturb and Observe, Deterministic Particle Swarm Optimization, and Grey Wolf Optimization under a sequence of irradiance steps as well as a power-over-voltage characteristics profile that mimics the electrical characteristics of a PV string under varying partial shading conditions. Overall, the simulation with the sequence of irradiance steps shows that while Fast GMPPT does not have the best convergence time, it has an excellent convergence rate as well as causes the least amount of power loss during the global search phase. Experimental test under varying partial shading conditions shows that while the GMPPT proposal is simple and lightweight, it is very performant under a wide range of dynamically varying partial shading conditions and boasts the best energy efficiency (94.74%) out of the 4 tested algorithms.

Comprehensive review and performance evaluation of maximum power point tracking algorithms for photovoltaic system

A photovoltaic array is environmentally friendly and a source of unlimited energy generation.However,it is presently a costlier energy generation system than other non-renewable energy sources.The main reasons are seasonal variations and continuously changing weather conditions,which affect the amount of solar energy received by the solar panels.In addition,the non-linear characteristics of the voltage and current outputs along with the operating environment temperature and variation in the solar radiation decrease the energy conversion capability of the photovoltaic arrays.To address this problem,the global maxima of the PV arrays can be tracked using a maximum power point tracking algorithm(MPPT)and the operating point of the photovoltaic system can be forced to its optimum value.This technique increases the efficiency of the photovoltaic array and minimizes the cost of the system by reducing the number of solar modules required to obtain the desired power.However,the tracking algorithms are not equally effective in all areas of application.Therefore,selecting the correct MPPT is very critical.This paper presents a detailed review and comparison of the MPPT techniques for photovoltaic systems,with consideration of the following key parameters:photovoltaic array dependence,type of system(analog or digital),need for periodic tuning,convergence speed,complexity of the system,global maxima,implemented capacity,and sensed parameter(s).In addition,based on real meteorological data(irradiance and temperature at a site located in Addis Ababa,Ethiopia),a simulation is performed to evaluate the performance of tracking algorithms suitable for the application being studied.Finally,the study clearly validates the considerable energy saving achieved by using these algorithms.

Maximum Power Point Tracking Control Using Neural Networks for Stand-Alone Photovoltaic Systems

The employment of maximum power point tracking techniques in the photovoltaic power systems is well known and even of immense importance. There are various techniques to track the maximum power point reported in several literatures. In such context, there is an increasing interest in developing a more appropriate and effective maximum power point tracking control methodology to ensure that the photovoltaic arrays guarantee as much of their available output power as possible to the load for any temperature and solar radiation levels. In this paper, theoretical details of the work, carried out to develop and implement a maximum power point tracking controller using neural networks for a stand-alone photovoltaic system, are presented. Attention has been also paid to the command of the power converter to achieve maximum power point tracking. Simulations results, using Matlab/Simulink software, presented for this approach under rapid variation of insolation and temperature conditions, confirm the effectiveness of the proposed method both in terms of efficiency and fast response time. Negligible oscillations around the maximum power point and easy implementation are the main advantages of the proposed maximum power point tracking (MPPT) control method.

Quadrature Kalman Filter(QKF) and Reduced Quadrature Kalman Filter(R-QKF)in Ballistic Target Tracking

Recently there have been researches about new efficient nonlinear filtering techniques in which the nonlinear filters generalize elegantly to nonlinear systems without the burdensome lineafization steps. Thus, truncation errors due to linearization can be compensated. These filters include the unscented Kalman filter （UKF）, the central difference filter （CDF） and the divided difference filter （DDF）, and they are also called Sigma Point Filters （SPFs） in a unified way. For higher order approximation of the nonlinear function. Ito and Xiong introduced an algorithm called the Gauss Hermite Filter, which is revisited in [5]. The Gauss Hermite Filter gives better approximation at the expense of higher computation burden, although it＇s less than the particle filter. The Gauss Hermite Filter is used as introduced in [5] with additional pruning step by adding threshold for the weights to reduce the quadrature points.

Modeling and small-signal stability analysis of doubly-fed induction generator integrated system

Owing to their stability,doubly-fed induction generator(DFIG)integrated systems have gained considerable interest and are the most widely implemented type of wind turbines and due to the increasing escalation of the wind generation penetration rate in power systems.In this study,we investigate a DFIG integrated system comprising four modules:(1)a wind turbine that considers the maximum power point tracking and pitch-angle control,(2)induction generator,(3)rotor/grid-side converter with the corresponding control strategy,and(4)AC power grid.The detailed small-signal modeling of the entire system is performed by linearizing the dynamic characteristic equation at the steady-state value.Furthermore,a dichotomy method is proposed based on the maximum eigenvalue real part function to obtain the critical value of the parameters.Root-locus analysis is employed to analyze the impact of changes in the phase-locked loop,short-circuit ratio,and blade inertia on the system stability.Lastly,the accuracy of the small-signal model and the real and imaginary parts of the calculated dominant poles in the theoretical analysis are verified using PSCAD/EMTDC.

Verification of Dosimetric and Positional Accuracy of Dynamic Tumor Tracking Intensity Modulated Radiation Therapy

Purpose: We performed both, dosimetric and positional accuracy verification of dynamic tumor tracking (DTT) intensity modulated radiation therapy (IMRT), with the Vero4DRT system using a moving phantom (QUASAR respiratory motion platform;QUASAR phantom) and system log files. Methods: The QUASAR phantom was placed on a treatment couch. Measurement of the point dose and dose distribution was performed for conventional IMRT, with the QUASAR phantom static and moving;for DTT IMRT, this was performed with the phantom moving for pyramid shaped, prostate, paranasal sinus, and pancreas targets. The QUASAR phantom was driven by a sinusoidal signal in the superior-inferior direction. Furthermore, predicted positional errors induced by the Vero4DRT system and mechanical positional errors of the gimbal head, were calculated using the system log files. Results and Conclusion: For DTT IMRT, the dose at the evaluation point was within 3% compared with the verification plan, and the dose distribution in the passing rates of γ was 97.9%, with the criteria of 3% dose and 3 mm distance to agreement. The position error calculated from the log files was within 2 mm, suggesting the feasibility of employing DTT IMRT with high accuracy using the Vero4DRT system.

Enhanced Perturb and Observe Control Algorithm for a Standalone Domestic Renewable Energy System

The generation of electricity,considering environmental and eco-nomic factors is one of the most important challenges of recent years.In this article,a thermoelectric generator(TEG)is proposed to use the thermal energy of an electric water heater(EWH)to generate electricity independently.To improve the energy conversion efficiency of the TEG,a fuzzy logic con-troller(FLC)-based perturb&observe(P&O)type maximum power point tracking(MPPT)control algorithm is used in this study.An EWH is one of the major electricity consuming household appliances which causes a higher electricity price for consumers.Also,a significant amount of thermal energy generated by EWH is wasted every day,especially during the winter season.In recent years,TEGs have been widely developed to convert surplus or unused thermal energy into usable electricity.In this context,the proposed model is designed to use the thermal energy stored in the EWH to generate electricity.In addition,the generated electricity can be easily stored in a battery storage system to supply electricity to various household appliances with low-power-consumption.The proposed MPPT control algorithm helps the system to quickly reach the optimal point corresponding to the maximum power output and maintains the system operating point at the maximum power output level.To validate the usefulness of the proposed scheme,a study model was developed in the MATLAB Simulink environment and its performance was investigated by simulation under steady state and transient conditions.The results of the study confirmed that the system is capable of generating adequate power from the available thermal energy of EWH.It was also found that the output power and efficiency of the system can be improved by maintaining a higher temperature difference at the input terminals of the TEG.Moreover,the real-time temperature data of Abha city in Saudi Arabia is considered to analyze the feasibility of the proposed system for practical implementation.

面向对海监视的舰船目标跟踪与航迹融合数据集

对海监视中航迹实时关联与轨迹融合任务是安全防控、区域态势监视、远程精确打击等军民应用领域的热点和难点问题,高质量的数据集对推动目标跟踪与融合技术在该领域的研究有重要作用。本研究针对目标跟踪与融合领域技术研究的数据需求以及目前公开数据集所存在的数据缺乏、场景设计针对性差、数据格式单一、数据描述不全等问题,通过仿真软件对复杂场景中多传感器多目标探测数据进行仿真,提供了一套面向典型对海监视场景(以舰船为探测对象的2D雷达与侦察传感器﹝ESM﹞)的目标跟踪与航迹融合数据集。其中仿真软件包括剧情发生器和传感器模拟器两部分,是一套成熟的目标跟踪场景仿真环境,提供逼真的探测数据模拟能力。本数据集涵盖的传感器对象包括2D雷达与侦察传感器,目标包括典型的海上舰船类别,并支持携带辐射源配置,设计了高速运动、密集交通、多传感器数据融合、特定舰船侦测和交叉定位等多种典型场景。本数据集中共包含368155条目标点迹,舰船数量为101条,时间范围15000秒,数据格式符合实际设备上报情景、探测误差模型符合实际。本数据集通过对数据误差进行正态性检验、对检测率、虚警率的场景检验以及实地调研,完成了对数据的准确性评估与数据完备性控制,可为舰船目标跟踪、轨迹融合等算法研究与验证提供基础数据。

农田灌溉光伏水泵系统性能测试分析

【目的】探究农田灌溉光伏水泵系统综合用能需求特性,提高该系统性能可靠性和实用性。【方法】基于高效水泵和研发的逆变器,构建了农田灌溉光伏水泵系统,结合系统装置构成与运行特点,对不同扬程运行工况下的电性能参数和扬水效率特性及水泵流量与功率特性等进行测试分析。【结果】在一定太阳辐射强度范围内,调速运行的水泵流量与输出频率有较好一致性;稳定运行时段的水泵流量可达到2 m^(3)·h^(-1);定扬程24.8 m下,系统最大扬水效率达12.7%,日平均扬水效率11.6%,日扬水量13.1 m^(3);当扬程降低到14.0 m时,最大扬水效率和日平均效率分别比前者低3.2%和3.6%,表明减低扬程并不一定能提高系统扬水效率,但对输出流量有影响。【结论】该农田灌溉光伏水泵系统配置稳态和动态性能良好,扬水能力可满足省水微灌和植被绿化等基本农业生产需要。

基于MPPT控制的两级式直流孤岛检测方法研究

针对主动式孤岛检测方法存在扰动同步注入、影响电网供电质量等问题,提出了一种基于最大功率点跟踪(MPPT)控制的两级式直流孤岛检测方法。该方法通过检测并网变换器直流侧电流来判断疑似孤岛,然后利用疑似孤岛信号触发电压扰动的注入使得孤岛后的公共耦合点(PCC)电压出现特定频率的波动。由于扰动信号的注入受疑似孤岛信号控制,减少了正常状态下扰动的注入时长,有效降低对系统电能质量的影响。此外建立小信号模型分析了耦合点电压对扰动分量的频域特性,选取扰动信号的最优频率。最后通过仿真与实验验证了所提方法在单机与多机工况下的有效性。

局部阴影下基于GWO-P&O混合算法的光伏最大功率点跟踪

针对局部遮阴环境下传统灰狼优化(Gray wolf optimization,GWO)算法在跟踪最大功率点时P-U特性曲线出现多峰值、后期收敛速度慢、稳态精度低等问题,结合灰狼优化算法和扰动观察法(Perturbation and observation,P&O)各自的优势,提出了基于GWO-P&O的混合优化最大功率点跟踪(Maximum power point tracking,MPPT)算法。首先,采用灰狼优化算法逐渐向光伏的全局最大功率点靠近。其次,在灰狼优化算法收敛后期引入P&O法,既保持了灰狼优化算法较高的稳态精度,又能以较快速度寻找到局部最大功率点。最后,在不同环境工况下,将所提出的GWO-P&O方法与传统GWO算法进行对比。结果表明,改进的GWO-P&O算法在保证良好稳态性能的同时,一定程度上提高了GWO算法后期跟踪最大功率时的收敛速度。

基于指数分布优化器的混合光伏-温差系统最大功率点跟踪

为解决混合光伏-温差(photovoltaic thermoelectric generator,PV-TEG)系统的最大功率点跟踪(maximum power point tracking,MPPT)问题以提高能源转换效率和利用率,提出了一种基于指数分布优化器(exponential distribution optimizer,EDO)的混合PV-TEG系统MPPT技术。EDO通过模拟指数分布的随机变化来搜索潜在的解空间,由于随机性,算法可有效避免在局部遮蔽条件(partial shading condition,PSC)下陷入局部最优,并在搜索空间中广泛探索以找到最优解。算例研究包括启动测试、太阳辐照度阶跃变化、随机变化、香港地区四季实际算例4个部分,并与其他5种算法进行对比分析,以较为全面地验证所提EDO技术在混合系统MPPT应用中的可行性和有效性。仿真结果表明,采用EDO的混合PV-TEG系统在不同运行条件下均能稳定、高效地实现最优越的MPPT性能,尤其是在春季低辐照度的条件下,EDO产生的能量分别超过蜻蜓算法(dragonfly algorithm,DA)、增量电导法(incremental conductance method,INC)、扰动观测法(perturbation observation method,P&O)能量输出的68.85%、66.13%和59.69%。

基于改进布谷鸟搜索算法的光伏MPPT控制

复杂阴影情况下,光伏阵列的P-V特性曲线会出现多个峰值,传统的MPPT算法因不能准确识别局部峰值和全局峰值,而无法进行复杂阴影情况下的最大功率点跟踪。针对传统布谷鸟搜索(Cuckoo Search,CS)算法因鸟窝之间缺乏交流能力导致可能陷入局部最优的问题,提出了一种多策略改进布谷鸟搜索(EGICS)算法。将传统CS算法中发现概率值的选择自适应变化,提高算法的搜索能力;将步长因子自适应化,提高算法的收敛速度;引入高斯扰动和精英反向学习策略,增加种群多样性,避免算法陷入局部最优。对EGICS算法在单峰和多峰函数中进行性能测试,并将其应用于光伏系统MPPT控制中进行仿真验证。仿真结果表明,EGICS算法在收敛速度、跟踪精度以及动态稳定三个方面有更好的效果。