Advances in the Research Application of Ultrasound Non-Invasive Stress-Strain Loop Technology in Cardiovascular Diseases

The ultrasound pressure-strain loop (PSL) technique is a non-invasive method of examining myocardial work, which takes into account the effect of cardiac afterload on deformation and combines the overall longitudinal strain force of the left ventricle with the changes in the left ventricular pressure, allowing earlier detection of possible subclinical cardiac damage in patients, and a more accurate and non-invasive assessment of the patient’s myocardial work performance. In this article, we will discuss the progress of PSL applications in cardiovascular diseases.

A New Particle Filter for Nonlinear Tracking Problems

A new particle filter is presented for nonlinear tracking problems. Inpractice, maneuvering target-tracking systems are usually nonlinear and incompletely observed, andthe main difficulty of maneuvering target-tracking problem lies in the fact that the maneuverabilityat every step is of high uncertainties. Here a new smoothing particle filter algorithm is proposed,which combines the particle filter to tackle the non-linear and non-Gaussian peculiarities of theproblem, together with smoothing of the PDF of system modes and thus settles the estimate problem ofthe target maneuverability. The simulation comparison with the auxiliary particle filters showsthat the approach has superiority and yields performance improvements in solving nonlinear trackingproblems.

Non-linear controllers in ship tracking control system

The cascade systems which stabilize the transverse deviation of the ship in relation to the set path is presented. The ship's path is determined as a broken line with specified coordinates of way points. Three controllers are used in the system. The main primary controller is the trajectory controller. The set value of heading for the course control system or angular velocity for the turning control system is generated. The course control system is used on the straight line of the set trajectory while the turning controller is used during a change of the set trajectory segment. The characteristics of the non-linear controllers are selected in such a way that the properties of the control system with the rate of turn controller are modelled by the first-order inertia, while the system with the course keeping controller is modelled by a second-order linear term. The presented control system is tested in computer simulation. Some results of simulation tests are presented and discussed.

Statistic PID Tracking Control for Non-Gaussian Stochastic Systems Based on T-S Fuzzy Model

A new robust proportional-integral-derivative （PID） tracking control framework is considered for stochastic systems with non-Gaussian variable based on B-spline neural network approximation and T-S fuzzy model identification. The tracked object is the statistical information of a given target probability density function （PDF）, rather than a deterministic signal. Following B-spline approximation to the integrated performance function, the concerned problem is transferred into the tracking of given weights. Different from the previous related works, the time delay T-S fuzzy models with the exogenous disturbances are applied to identify the nonlinear weighting dynamics. Meanwhile, the generalized PID controller structure and the improved convex linear matrix inequalities （LMI） algorithms are proposed to fulfil the tracking problem. Furthermore, in order to enhance the robust performance, the peak-to-peak measure index is applied to optimize the tracking performance. Simulations are given to demonstrate the efficiency of the proposed approach.

Adaptive Human Tracking Across Non-overlapping Cameras in Depression Angles

To track human across non-overlapping cameras in depression angles for applications such as multi-airplane visual human tracking and urban multi-camera surveillance,an adaptive human tracking method is proposed,focusing on both feature representation and human tracking mechanism.Feature representation describes individual by using both improved local appearance descriptors and statistical geometric parameters.The improved feature descriptors can be extracted quickly and make the human feature more discriminative.Adaptive human tracking mechanism is based on feature representation and it arranges the human image blobs in field of view into matrix.Primary appearance models are created to include the maximum inter-camera appearance information captured from different visual angles.The persons appeared in camera are first filtered by statistical geometric parameters.Then the one among the filtered persons who has the maximum matching scale with the primary models is determined to be the target person.Subsequently,the image blobs of the target person are used to update and generate new primary appearance models for the next camera,thus being robust to visual angle changes.Experimental results prove the excellence of the feature representation and show the good generalization capability of tracking mechanism as well as its robustness to condition variables.

入射偏角对非跟踪复合抛物面聚光器性能影响

为了降低复合抛物面聚光器对跟踪精度的要求,提高其在集热过程中的光热转化能力,探究入射偏角对新型复合抛物面聚光器非跟踪工况时光热性能的影响机制。理论分析该聚光器在集热过程中的能量转化关系,并利用光学仿真软件TracePro研究入射偏角对聚光器光学性能的影响规律;在此基础上搭建非跟踪复合抛物面聚光器性能测试试验台,在实际天气条件下测试分析聚光器光热性能随径向入射偏角的变化规律。结果表明:当光线正入射时,聚光器的光线接收率与聚光效率分别为100%和83.42%;当径向入射偏角α为16°时,该聚光器的光线接收率与聚光效率分别为53.00%和44.82%;当轴向入射偏角β为30°时,光线接收率与聚光效率分别为88.74%和74.42%;在空气流速为3.7 m/s时,聚光器的最高出口温度与瞬时集热量分别为31.3℃和782.8 W,分别比聚光器接收上偏10°和下偏10°入射辐射时提高了3.7、6.1℃和131.0、217.9 W;该聚光器接收正入射辐射时的平均光热转化效率为77.45%,比接收上偏10°和下偏10°入射辐射的平均光热转化效率高42.14%和52.97%。

基于漏斗函数双电机伺服系统跟踪与同步控制

针对双电机驱动伺服系统具有未知非线性的问题,提出一种基于漏斗函数的跟踪与同步控制方案。首先,利用神经网络逼近和补偿复杂的非线性,在此基础上,引入滤波技术解决传统反步控制的“计算爆炸”问题,同时引入非光滑漏斗误差面确保系统的状态量被约束在预定义的漏斗边界内,结合改进的漏斗函数和反步设计技术设计了一种自适应量化漏斗跟踪控制方案。为了同时保证双电机的同步运行,同步控制器采用了平均偏差耦合策略,实现了双电机伺服系统的跟踪与同步控制。仿真结果表明,该方法可以实现对负载的跟踪以及双电机的同步。

自动泊车前轮转角闭环的分层控制方案

为提高自动泊车系统中控制器的抗扰动能力,优化控制律执行效果,提出了前轮转角闭环的分层控制方案.设计了以行驶距离为非时间参考量的fal函数非光滑控制律,输出前轮转角控制量.以阿克曼转向模型为基础,建立了前轮转角观测器,并使用模糊滑模控制器实现前轮转角闭环的横向控制.搭建Carsim/Simulink联合仿真系统,在典型泊车场景下验证所设计控制器的有效性、跟踪效果及鲁棒性.使用实车测试平台开展了试验.结果表明:所设计的前轮转角闭环分层控制方案能够快速准确地跟踪目标路径,提高了泊车系统的横向控制精度,并在未知转向非线性扰动下也具有良好的跟踪控制效果.

永磁直驱风力发电机非奇异终端滑模控制

为提高永磁直驱风力发电系统的抗扰能力和控制精度,提出了一种扰动观测器与非奇异快速终端滑模控制相结合的最大功率跟踪控制策略。利用扰动观测器得到风力发电机的转矩变化,对控制器进行前馈补偿;采用非奇异快速终端滑模面提高控制器的动态性能,实现系统快速收敛,减少因扰动引起的抖振。仿真结果表明,所提策略在随机风速的情况下可以准确估计转矩变化,提高最大功率跟踪过程中的转速跟踪精度和风能利用率。

脊柱无创示踪装置在静态和术中动态环境下的临床精度研究

目的本研究旨在探讨新型无创示踪系统在静态和动态环境下的临床精度表现。方法该系统由无创示踪装置和光学导航设备组成。在静态环境下,使用术中C臂电子计算机断层扫描(computed tomography,CT)扫描脊椎模型,通过CT图像空间中的标记点进行实时自动化配准,测量无创示踪装置配准精度和8个体表验证点的配准精度。将无创示踪装置与连接于椎体的刚性示踪装置进行比较,测量椎弓根螺钉导针在体表下3~4 cm处螺钉入点位置误差和体表下8~9 cm处螺钉终点位置误差,以及导针整体规划路径与实际路径的角度误差。本研究中前期构建了呼吸运动下脊柱椎体运动模型以仿真术中椎体的动态环境,通过机械臂进行伺服模拟呼吸运动构建术中动态环境,并在术中同法测量动态环境下的无创示踪器临床精度。结果无创示踪器配准误差较小,静态环境下为(0.483±0.242)mm,动态环境下为(0.524±0.229)mm。无创示踪装置内部区域的配准误差低于外部区域的配准误差,静态环境下为[(0.472±0.202)mm vs(0.954±0.279)mm,P<0.001],动态环境下为[(0.516±0.188)mm vs(1.029±0.252)mm,P<0.001]。8条导针入路的骨表面入点精度高于骨内部终点精度,体表下3~4 cm处位置误差小于8~9 cm处,静态环境下为[(0.018±0.024)mm vs(0.061±0.061)mm,P=0.002],动态环境下为[(0.403±0.275)mm vs(0.938±0.640)mm,P<0.001]。导针入路的角度误差较小,静态环境下<0.25°,动态环境下<1.50°。结论在静态环境下,无创示踪器对体表区域和深部区域均保持较高位置精度和角度精度,在动态环境中,体表区域和深部区域的定位精度和角度精度降低,但仍在可接受的范围内。

基于自回归小波神经网络的机械臂自适应滑模控制

针对机械臂存在模型不确定和未知扰动的问题,提出一种动力学模型参数分块逼近的神经网络非奇异终端滑模(nonsingular terminal sliding mode, NTSM)控制方法.为加快系统跟踪误差的收敛速度,避免传统终端滑模存在的奇异性问题,采用一种非奇异终端滑模面.利用多组自回归小波神经网络(self-recurrent wavelet neural network, SRWNN)分块逼近系统未知的动力学模型参数,并采用自适应更新律调整权重.通过积分控制项补偿SRWNN的逼近误差,并使用Lyapunov稳定性理论证明了系统稳定性.使用MATLAB进行仿真分析,分块SRWNN滑模控制与滑模控制、整体SRWNN滑模控制相比,关节角度跟踪误差的平均稳态误差分别降低了31.9%、76.5%,表明此方法是一种可靠、有效的轨迹跟踪控制方法.

顾及运动特征的轨道不平顺测量精度分析

针对运动特征方程标准差和量测频率对轨道不平顺测量精度的影响进行研究,结合GNSS/INS与NHC的算法建立模型,利用协方差法进行定量分析。仿真实验表明加入运动特征方程提高了轨道不平顺的测量精度。运动特征方程标准差不变时,随着频率的增加,精度提高;频率不变时,运动特征方程标准差越小则轨道测量精度越高;给定适当的运动特征方程标准差可以满足轨道不平顺测量精度的要求。现场实验结果与仿真实验结果基本一致,证明所提方法的正确性。研究结论为提高轨道不平顺测量精度提供参考。

Gaussian Sum PHD Filtering Algorithm for Nonlinear Non-Gaussian Models

A new multi-target filtering algorithm, termed as the Gaussian sum probability hypothesis density （GSPHD） filter, is proposed for nonlinear non-Gaussian tracking models. Provided that the initial prior intensity of the states is Gaussian or can be identified as a Gaussian sum, the analytical results of the algorithm show that the posterior intensity at any subsequent time step remains a Gaussian sum under the assumption that the state noise, the measurement noise, target spawn intensity, new target birth intensity, target survival probability, and detection probability are all Gaussian sums. The analysis also shows that the existing Gaussian mixture probability hypothesis density （GMPHD） filter, which is unsuitable for handling the non-Gaussian noise cases, is no more than a special case of the proposed algorithm, which fills the shortage of incapability of treating non-Gaussian noise. The multi-target tracking simulation results verify the effectiveness of the proposed GSPHD.

基于U^(2)-Net的高精度多套层位追踪方法及应用

层位追踪是地震资料解释中一项基础且重要的工作,常规智能层位追踪方法的精度难以满足实际生产需求。为此,提出了一种基于U^(2)-Net的高精度多套层位追踪方法。首先,设计一种充填标签的制作方法,遍历地震数据每个像素点,判断当前像素点所在位置并为其划分一个层位区域;对于穿过断层的层位,则自动搜寻相邻层位,实现非全区层位、断层等复杂条件下的地震反射层位及不整合面的充填标签的制作;然后,利用充填标签,采用U^(2)-Net网络模型对F3数据体和M工区地震资料进行训练。与U-Net+PPM网络模型相比,U^(2)-Net网络模型的预测精度更高,稳定性更好,泛化性更强,训练时间更短,且预测复杂地区的地震反射层位的准确率和平均交并比都大于95%。该方法可以较好地适应低信噪比地震资料的层位追踪。

民用机场场道工程不停航施工安全管理要点研究

由于民用航空机场的建造水平越来越高,施工作业也越来越复杂,因此需要在施工中完善组织结构与加强安全管理。基于此,文章首先介绍了场道工程不停航施工的特点,研究了其施工方案以及施工安全管理要点,以期促进场工程的可持续发展。

基于雷达和光学传感器的目标状态联合估计研究

针对传统雷达和光学传感器的目标状态联合估计未考虑到不同传感器精度对于联合系统的影响而导致跟踪效果不理想的问题,提出一种基于雷达和光学传感器的目标状态间接联合估计方法,提高了联合系统对目标的跟踪性能。该方法首先建立了雷达和光学传感器的观测模型和基于非合作目标的CA运动模型,然后基于雷达和光学传感器的测量精度结合扩展卡尔曼滤波(Extended Kalman Filter,EKF)设计了一种间接联合估计算法,实验仿真结果表明该方法相比较传统的直接联合估计方法,可以更为准确地估计目标位置、速度和加速度等状态信息,有效提高了对非合作目标的跟踪精度。

基于检测跟踪算法的多分量瞬时频率调频率估计

作为非平稳信号的重要特征,瞬时频率(instantaneous frequency,IF)和瞬时调频率(instantaneous frequency rate,IFR)的准确估计具有重要意义。现有方法在处理存在时频交叠的多分量非平稳信号时易发生关联错误等问题。短时调频傅里叶变换通过将信号在时间频率调频率三维空间中进行表征,使不同分量发生交叠的可能性大幅降低,且基于频率调频率的变化规律可实现分量的时序关联。据此,提出一种基于检测跟踪算法的多分量IF-IFR估计方法。首先,针对传统检测算法在噪声环境下精度不足问题,提出了基于改进YOLOX网络的检测方法,实现了信号瞬时频率调频率的估计和瞬时形状特征的提取。然后,提出基于卡尔曼滤波的瞬时估计值和形状特征时序关联方法,以形成稳定连续的多分量IF和IFR估计。通过仿真及实测实验对所提算法进行了验证,在设置的仿真场景中,-5 dB信噪比条件下最优估计误差小于0.8 Hz,证明了所提方法的有效性。

一种非线性自适应液压系统控制器设计与研究

针对现有电液伺服系统的非线性、参数不确定导致轨迹跟踪精度低的问题,提出了一种非线性自适应输出反馈控制器。分析了液压系统的非线性模型,为控制器设计提供理论基础。非线性自适应输出反馈控制器包含自适应线性扩展状态观测器(Linear Extended State Observer, LESO)和非线性扰动观测器(Nonlinear Disturbance Observer, NDO),用来估计系统中不可策略状态以及惯性载荷动力学中的失配扰动。实验结果表明,所提出的非线性自适应输出反馈鲁棒控制器可有效解决PI控制器存在的谐振问题。

复杂干扰杂波环境下三维目标检测前跟踪算法

针对因随机假目标干扰、强杂波存在的复杂环境中三维目标检测问题,提出一种基于平行线坐标变换的多层次检测前跟踪算法。雷达量测点被先后置于规格化后的径向距离-时间平面、方位角-时间平面和俯仰角-时间平面分层次进行非相参积累和点迹筛选,每次筛选只对上一层的筛选结果进行处理,再根据先验信息进行航迹约束和航迹融合,得到最终检测结果。通过仿真对算法进行性能验证和分析,结果显示,该算法在不同信干杂比、量测误差和杂波密度下均能有效滤除虚假量测点,实现真实航迹的检测。

基于N-EKF的非合作低轨目标双星无源定位跟踪算法

针对两颗天基光学卫星对低轨非合作目标进行无源定位跟踪的问题,提出了一种基于Newton迭代与扩展卡尔曼滤波(Newton iteration and extended Kalman filter,N-EKF)的定位跟踪算法。首先,将基于角度测量信息的双星观测模型转化为双直线公垂线中点问题,并进一步转化为非线性方程问题,使用Newton迭代算法得到非合作目标的初始定位信息。然后,采用扩展卡尔曼滤波(extended Kalman filter,EKF)方法,在初始定位信息基础上,结合近地轨道动力学模型,实现对非合作在轨目标的精确跟踪滤波。最后,通过仿真验证了所提方法的可行性及优势。