Demagnetization Analysis and Velocity Tracking Control of In-wheel Motor

The error caused by irreversible demagnetization damages the accurate velocity tracking of an in-wheel motor in a mobile robot.A current feedforward vector control system based on ESO is proposed to compensate it for the demagnetization motor.A demagnetization mathematical model is established to describe a permanent magnet synchronous motor,which took the change of permanent magnet flux linkage parameters as a factor to count the demagnetization error in velocity tracking.The uncertain disturbance estimation model of the control system is built based on ESO,which eliminates the system error by the feedforward current compensation.It is compared with the vector control method in terms of control accuracy.The simulation results show that the current feedforward vector control method based on ESO reduces the velocity tracking error greatly in conditions of motor demagnetization less than 30%.It is effective to improve the operation accuracy of the mobile robot.

Evaluation of a laying-hen tracking algorithm based on a hybrid support vector machine

Background： Behavior is an important indicator reflecting the welfare of animals. Manual analysis of video is the most commonly used method to study animal behavior. However, this approach is tedious and depends on a subjective judgment of the analysts. There is an urgent need for automatic identification of individual animals and automatic tracking is a fundamental part of the solution to this problem.Results： In this study, an algorithm based on a Hybrid Support Vector Machine（HSVM） was developed for the automated tracking of individual laying hens in a layer group. More than 500 h of video was conducted with laying hens raised under a floor system by using an experimental platform. The experimental results demonstrated that the HSVM tracker outperformed the Frag（fragment-based tracking method）, the TLD（Tracking-Learning-Detection）,the PLS（object tracking via partial least squares analysis）, the Mean Shift Algorithm, and the Particle Filter Algorithm based on their overlap rate and the average overlap rate.Conclusions： The experimental results indicate that the HSVM tracker achieved better robustness and state-of-theart performance in its ability to track individual laying hens than the other algorithms tested. It has potential for use in monitoring animal behavior under practical rearing conditions.

Novel Real-Time Seam Tracking Algorithm Based on Vector Angle and Least Square Method

Real-time seam tracking can improve welding quality and enhance welding efficiency during the welding process in automobile manufacturing.However,the teaching-playing welding process,an off-line seam tracking method,is still dominant in automobile industry,which is less flexible when welding objects or situation change.A novel real-time algorithm consisting of seam detection and generation is proposed to track seam.Using captured 3D points,space vectors were created between two adjacent points along each laser line and then a vector angle based algorithm was developed to detect target points on the seam.Least square method was used to fit target points to a welding trajectory for seam tracking.Furthermore,the real-time seam tracking process was simulated in MATLAB/Simulink.The trend of joint angles vs.time was logged and a comparison between the off-line and the proposed seam tracking algorithm was conducted.Results show that the proposed real-time seam tracking algorithm can work in a real-time scenario and have high accuracy in welding point positioning.

GPS Vector Tracking Loop with Fault Detection and Exclusion

In this paper,both the integrity monitoring and fault detection and exclusion(FDE)mechanisms are incorporated into the vector tracking loop(VTL)architecture of the Global Positioning System(GPS)receiver for reliability enhancement.For the VTL,the tasks of signal tracking and navigation state estimation no longer process separately and a single extended Kalman filter(EKF)is employed to simultaneously track the received signals and estimate the receiver’s position,velocity,etc.In contrast to the scalar tracking loop(STL)which utilizes the independent parallel tracking loop approach,the VTL technique is beneficial from the correlation of each satellite signal and user dynamics.The VTL approach provides several important advantages.One of the merits is that the tracking loop can be assisted for overcoming the problem of signal blockage.Although the VTL architectures provide several important advantages,they suffer some fundamental drawbacks.For example,the errors in the navigation solutions may degrade the tracking accuracy.The most significant drawback is that failure of tracking in one channel may affect the entire tracking loop and possibly lead to loss of lock.For reliability enhancement,the EKF based integrity monitoring and FDE algorithms are developed to prevent the error from spreading into the entire tracking loop.The integrity monitoring is utilized to check the possible fault in the pseudorange and the pseudorange rate,followed by the FDE mechanism employed to exclude the abnormal satellite signals.Performance assessment and evaluation for the proposed approach will be presented.

Quantitative analysis of the performance of vector tracking algorithms

Vector tracking changes the classical structure of receivers. Combining signal tracking and navigation solution,vector tracking can realize powerful processing capabilities by the fusion technique of receiving channel and feedback correction. In this paper,we try to break through the complicated details of numerical analysis,consider the overall influencing factors of the residual in observed data,and use the intrinsic link between a conventional receiver and a vector receiver. A simple method for performance analysis of the vector tracking algorithm is proposed. Kalman filter has the same steady performance with the classic digital lock loop through the analysis of the relation between gain and band width. The theoretical analysis by the least squares model shows that the reduction of range error is the basis for the superior performance realized by vector tracking. Thus,the bounds of its performance enhancement under weak signal and highly dynamic conditions can be deduced. Simulation results verify the effectiveness of the analysis presented here.

Influence of B1 code correlation loop for vector tracking structures under complicated environment

The code tracking loop is a key component for user positioning. The pseudorange information of Bei Dou B1 signals has been fused and changed for vector tracking, so a correlation output model for complex scenarios is designed to prevent the propagation of error and valuate the signal performance. The relevant software and hardware factors that affect the output are analyzed.A single channel time-division multiplexing(TDM) method for multicorrelation data extraction is proposed. Statistical characteristics of the correlation output data for both vector and scalar structures are evaluated. Simulation results show that correlation outputs for both structures follow normal or Chi-squared distributions in normal conditions, and the Gamma distribution in harsh conditions. It is shown that a tracking model based on the multi-channel fusion hardly changes the probability distribution of the correlation output in the normal case, but it reduces the ranging error of the code loop, and hence the tracking ability of the code loop for weak signals is improved. Furthermore, vector tracking changes the pseudorange characteristics of channels anytime, and affects the mutual correlation outputs of the code loops in the abnormal case. This study provides a basis for the subsequent design of autonomous integrity algorithms for vector tracking.

GPS Vector Tracking Receivers with Rate Detector for Integrity Monitoring

In this paper,the integrity monitoring algorithm based on a Kalman filter(KF)based rate detector is employed in the vector tracking loop(VTL)of the Global Positioning System(GPS)receiver.In the VTL approach,the extended Kalman filter(EKF)simultaneously tracks the received signals and estimates the receiver’s position,velocity,etc.In contrast to the scalar tracking loop(STL)that uses the independent parallel tracking loop approach,the VTL technique uses the correlation of each satellite signal and user dynamics and thus reduces the risk of loss lock of signals.Although the VTL scheme provides several important advantages,the failure of tracking in one channel may affect the entire system and lead to loss of lock on all satellites.The integrity monitoring algorithm can be adopted for robustness enhancement.In general,the standard integrity monitoring algorithm can timely detect the step type erroneous signals.However,in the presence of ramp type slowly growing erroneous signals,detection of such type of error takes much more time since the error cannot be detected until the cumulative exceeds the specified threshold.The integrity monitoring based on the rate detector possesses good potential for resolving such problem.The test statistic based on the pseudorange residual in association with the EKF is applied for determination of whether the test statistic exceeds the allowable threshold values.The fault detection and exclusion(FDE)mechanism can then be employed to exclude the hazardous erroneous signals for the abnormal satellites to assure normal operation of GPS receivers.Feasibility of the integrity monitoring algorithm based on the EKF based rate detector will be demonstrated.Performance assessment and evaluation will be presented.

A robust vector tracking loop structure based on potential bias analysis

This paper proposes a robust vector tracking loop structure based on potential bias analysis. The influence of four kinds of biases on the existing two implementations of Vector Tracking Loops(VTLs) is illustrated by theoretical analysis and numerical simulations, and the following findings are obtained. Firstly, the initial user state bias leads to steady navigation solution bias in the relative VTL, while new measurements can eliminate it in the absolute VTL. Secondly, the initial code phase bias is transferred to the following navigation solutions in the relative VTL, while new measurements can eliminate it in the absolute VTL. Thirdly, the user state bias induced by erroneous navigation solution of VTLs can be eliminated by both of the two VTLs. Fourthly,the multipath/NLOS likely affects the two VTLs, and the induced tracking bias in the duration of the multipath/NLOS would decrease the performance of VTLs. Based on the above analysis,a robust VTL structure is proposed, where the absolute VTL is selected for its robustness to the two kinds of initialization biases;meanwhile, the instant bias detection and correction method is used to improve the performance of VTLs in the duration of the multipath/NLOS. Numerical simulations and experimental results verify the effectiveness of the proposed robust VTL structure.

Vector modeling and track simulation in axial turn-milling motion

Through vector analysis the kinetic vector model is built in a machining cylinder surface through axial turn-milling. When building a kinetic vector model in the machining field, machining through axial turn-milling and using equilateral triangles and square prism surfaces, the kinetic vector model is given any equilateral polygon prismic surface. Kinetic tracks are simulated through these kinetic models respectively, thus it can be seen that the axial turn-milling is a very effective method in manufacturing any equilateral, polygon, prismic surface.

Envelop Tracking and Measurement

Power consumption is a vital issue for communication systems,especially for those which powered by batteries.In wireless communication system,the power consumption of PA(power amplifier)consumes a large portion of power compared with another component.How to reduce the power consumption of PA is always one of the big topics in the R&D and application of PA.Modern communication systems which have the high Peak to Average Power Ratio(PAPR).Envelope tracking technology can effectively reduce the power consumption of PA,especially for the high PAPR system.In the meantime,ET does not affect the performance of PA and communication system.This paper introduces the principle of ET,and gives the test method of ET performance.An ET test system has been built using R&S SMW 200A vector signal generator and FSW vector signal analyzer.The measurement result shows 20%of power saving by the application of ET.

Continuous Tracking of GPS Signals with Data Wipe-Off Method

The decentralized pre-filter based vector tracking loop(VTL)configuration with data wipe-off(DWO)method of the Global Positioning System(GPS)receiver is proposed for performance enhancement.It is a challenging task to continuously track the satellites’signals in weak signal environment for the GPS receiver.VTL is a very attractive technique as it can provide tracking capability in signal-challenged environments.In the VTL,each channel will not form a loop independently.On the contrary,the signals in the channels of VTL are shared with each other;the navigation processor in turn predicts the code phases.Thus,the receiver can successfully track signals even the signal strength from individual satellite is weak.The tracking loop based on the pre-filter provides more flexible adjustment to specific environments to reduce noise interference.Therefore,even if the signals from some satellites are very weak the receiver can track them from the navigation results based on the other satellites.The navigation data,which contains information necessary to perform navigation computations,are binary phase-shift keying(BPSK)modulated onto the GPS carrier phase with the bit duration of 20 ms(i.e.,50 bits per second)for the GPS L1 C/A signals.The coherent integration interval can be extended for improved tracking performance in signal-challenged environment.However,tracking accuracy is decreased by possible data bit sign reversal.The DWO algorithm can be employed to remove the data bit in I and Q correlation values so as to avoid energy loss due to bit transitions when the integration interval of the correlator is extended over 20 ms under the low carrier-to-noise ratio(C/No)environments.The proposed method has an advantage to provide continuous tracking of signals and obtain improved navigation performance.Performance evaluation of the tracking capability as well as positioning accuracy will be presented.

TRACKING DEFORMABLE AND OCCLUDED OBJECTS USING PARTICLE FILTERING AND GVF-SNAKE

An adaptive object tracking algorithm based on particle filtering and a modified Gradient Vector Flow (GVF) Snake is proposed for tracking moving and deforming objects. The original contours of objects are obtained by using the background differencing method,and the true contours of objects can be converged by means of the powerful searching ability of a modified GVF-Snake. Finally,an Energetic Particle Filtering (EPF) algorithm is obtained by combining particle filtering and a modified GVF-Snake,and by using K-means and the EPF algorithm,multiple objects can be tracked. The proposed tracking tactic for partially occluded objects can effectively improve its anti-occlusion ability. Experiments show that this algorithm can obtain better tracking effect even though the tracked object is occluded.

An Integrated Face Tracking and Facial Expression Recognition System

This article proposes a feature extraction method for an integrated face tracking and facial expression recognition in real time video. The method proposed by Viola and Jones [1] is used to detect the face region in the first frame of the video. A rectangular bounding box is fitted over for the face region and the detected face is tracked in the successive frames using the cascaded Support vector machine (SVM) and cascaded Radial basis function neural network (RBFNN). The haar-like features are extracted from the detected face region and they are used to create a cascaded SVM and RBFNN classifiers. Each stage of the SVM classifier and RBFNN classifier rejects the non-face regions and pass the face regions to the next stage in the cascade thereby efficiently tracking the face. The performance of tracking is evaluated using one hour video data. The performance of the cascaded SVM is compared with the cascaded RBFNN. The experiment results show that the proposed cascaded SVM classifier method gives better performance over the RBFNN and also the methods described in the literature using single SVM classifier [2]. While the face is being tracked, features are extracted from the mouth region for expression recognition. The features are modelled using a multi-class SVM. The SVM finds an optimal hyperplane to distinguish different facial expressions with an accuracy of 96.0%.

Study on Mobile Object Tracking and Intercept Technology Research

Background difference method[l] is one of the effective paths of improving robot＇ s vision reaction ability, and robots use background difference method to find the moving object in vision range and conduct tracking monitoring of moving objects. Then it uses support vector to conduct learning fitting of moving object, which can effectively predict the moving trend of moving object, and then it fabricates corresponding decision programs to conduct intercept capture of moving objects.

Unobservable Problem of Target Tracking with Bearing-only Measurements in 3-dimensional Space

The bearings-only tracking (BOT) system is said to be observability if and only if the target motion parameters can be uniquely determined by noise-free bearing measurements. By utilizing the method of orthogonal vectors and characteristic of linear matrix equation, the problem of observability for BOT in noise-free bearings measurements from single observer is discussed based on the target and observer traveling in the 3-dimensional space. A proposition that BOT for target and observer traveling in the 3-dimensional space with constant acceleration remains unsolvable is presented and proved. By proving the proposition, it is also shown that some motion parameter ratios of target can be estimated under certain condition satisfied by measurements and time samples. The proposition is extended to arbitrary rank of manoeuvre for the observer and the target, which BOT remains unobservable property while the rank of target manoeuvre is higher than that of the observer manoeuvre. The theoretical analysis of this paper provides the guidelines for how the observer trajectory should be formulated to avoid unobservable state for BOT in practice application.

基于状态可观测性和多模态数据PF的移动目标跟踪

为了实现对移动目标的跟踪,提出了一种新颖的基于目标状态可观测性和多模态数据粒子滤波(Particle Filter,PF)的跟踪方案。通过部署在目标移动区域中的传感器获得跟踪目标的距离和到达方向测量值,对接收到的数据进行预处理来计算PF的观测值,以形成一个临时距离图像。通过利用状态更新函数和形成的候选图像模板确定目标状态向量;在PF器中加入额外的加权阶段,使得PF器可自适应地同步多模态数据流,以实现鲁棒的目标跟踪。仿真实验结果验证了所提方案能够有效地跟踪移动目标。

基于SVM算法的虚假航迹识别

针对云雨杂波和主被动干扰导致多雷达传感器产生虚假目标航迹的问题,利用支持向量机(SVM)算法的自主学习能力,通过构建基于数据驱动的判别模型进行虚假航迹识别。针对航迹起始得到的目标潜在航迹,利用人工智能数据驱动、自学习的特点,设计了SVM算法。通过对已标记真假的目标航迹样本进行离线学习,形成虚假航迹识别的SVM分类器,实现了基于数据驱动的判别模型代替先验知识规则约束的固定模型,并在工程应用中,利用SVM分类器在线识别虚假航迹,完成实时剔除。通过实测雷达数据实验验证,该算法的目标虚假航迹准确率高达95%以上,完全满足实际的工程应用需求。相比基于阈值或规则进行硬性判断的传统虚假航迹识别方法,所提出的算法不仅提高了准确率,还具有较高的实时性,能够适应复杂多变的杂波环境,在实际应用中具有更强的适应性和实用性。因此,提出的基于SVM算法的虚假航迹识别方法对于密集杂波场景下的虚假航迹剔除问题具有显著的实际应用价值。

基于FPGA的PMLSM三矢量模型预测电流控制IP核设计及硬件在环验证

为了提升永磁直线同步电机(PMLSM)电流控制的稳态性能和执行速度,同时降低资源消耗,基于现场可编程门阵列(FPGA)设计了一个三矢量模型预测电流控制(TV-MPCC)知识产权(IP)核,并利用FPGA在环可视化验证方法,建立了一个PMLSM的TV-MPCC IP核验证系统。通过Simulink对TV-MPCC策略进行算法级仿真,并优化了基本电压矢量的作用顺序;采用并行与资源共享硬件优化技术设计并封装了一个TV-MPCC IP核,并对其进行了功能仿真;将设计部署在FPGA芯片XC7Z020CLG400-2上,利用FPGA在环可视化验证平台进行实验研究。结果表明,TV-MPCC策略下d、q轴电流跟踪误差和电流脉动均降低90%以上;FPGA工作在100 MHz下,实现一次算法的时间为0.62μs,仅为软件PyCharm执行时间的0.414%。

气象卫星大气导风研究进展和未来展望

本文主要回顾了气象卫星导风的发展历程并对未来发展方向进行了阐述.引言部分首先回顾发展历程并介绍了导风发展史上的一些里程碑事件,分别对中国、美国、欧洲以及日本的气象卫星导风情况进行了简要介绍.第一节详细总结了多种传统气象卫星导风算法的特点和关键技术,介绍了交叉相关法、形态辨认法以及亚像元法.此外,还描述了五种较为常用的高度指定算法,对传统导风追踪算法以及高度指定算法的原理进行了详细地描述.第二节归纳了最近几年基于计算机视觉和机器学习技术发展起来的多种新体制的气象卫星导风产品,分别介绍了光流法、三维导风以及中尺度导风的优势和研究背景.最后,对比了传统与新型气象卫星各种导风算法的优缺点,展望了未来的发展趋势和应用前景.特别是指出光流法导风有着空间分辨率高、三维导风能得到更多层风场的信息、中尺度导风则能对特殊天气如热带气旋实现高时空分辨率的观测的优势,并提出三维导风与中尺度导风的应用研究将是未来重要发展方向.

牵引式欺骗对矢量跟踪环路的影响

牵引式欺骗能够在不引起跟踪环路失锁的条件下诱使接收机跟踪欺骗信号,是一种隐蔽性很高的欺骗干扰方式。对于标量接收机,由于其跟踪环路相互独立,因此针对单个信号进行牵引式欺骗时,不会受其他信号的影响。而矢量接收机的跟踪环路通过接收机状态耦合,存在相互影响,即牵引式欺骗对矢量和标量跟踪环路的影响存在差异。本文基于无噪声且欺骗信号与真实信号载波频率和载波相位相等的假设条件,分析牵引式欺骗对矢量跟踪环路的影响,推导出欺骗成功条件,并利用信号源模拟器和软件接收机对分析结果进行验证。研究结果表明,对矢量跟踪环路成功实施牵引式欺骗的条件较标量跟踪环路更为严苛,反映出矢量跟踪环路固有的抗欺骗干扰能力。