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.

Performance analysis of a novel chip tracking loop used for regenerative pseudo-noise ranging clock recovery

To improve the performance of composite pseudo-noise （PN） code clock recovery in a regenerative PN ranging system at a low symbol signal-to-noise ratio （SNR）, a novel chip tracking loop （CTL） used for regenerative PN ranging clock recovery is adopted. The CTL is a modified data transition tracking loop （DTTL）. The difference between them is that the Q channel output of the CTL is directly multiplied by a clock component, while that of the DTTL is multiplied by the Ⅰ channel transition detector output. Under the condition of a quasi-squareware PN ranging code, the tracking （ mean square timing jitter） performance of the CTL is analyzed. The tracking performances of the CTL and the DTTL, are compared over a wide range of symbol SNRs. The result shows that the CTL and the DTTL have the same performance at a large symbol SNR, while at a low symbol SNR, the former offers a noticeable enhancement.

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.

Adaptively Robust Phase Lock Loop for Low C/N Carrier Tracking in a GPS Software Receiver

在 GPS 应用程序的一个重要问题是怎么追踪 GPS (全球放系统) 在低 carrier-to-noise 比率(C/N ) 下面精确并且连续地发信号。在这份报纸，一个适应地柔韧的过滤器基于低 C/N 搬运人阶段锁循环(PLL ) 在一个 GPS 软件接收装置平台下面被开发。就传统的追踪循环上的低 C/N 搬运人信号的效果而言，追踪循环的平行关联被建立。一个线性最佳的评估者被设计在 kinematics 模型和大小处理依赖噪音。而且，一个适应地柔韧的过滤器基于三片断功能被设计调整因素。当收到的信号在有利条件下面时，新过滤器的表演很类似于一个标准 Kalman 过滤器。为追踪的一个实际弱搬运人，这新提高的 PLL 聪明地根据全部的阶段神经质分析调节循环参数。它成功地由适应地平衡更新的动态模型状态和大小的影响抵抗孤立点和动态模型错误。新过滤器的坚韧性和效率被测试实验的一些真实数据表明。结果证实有追踪循环的这个适应地柔韧的阶段的阶段错误的标准差能在 24 dB-Hz 附近与卫星 C/N 比率到达 0.01 个周期，它显著地改进表演。

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.

Minimum Error Entropy Based EKF for GPS Code Tracking Loop

This paper investigates the minimum error entropy based extended Kalman filter(MEEKF)for multipath parameter estimation of the Global Positioning System(GPS).The extended Kalman filter(EKF)is designed to give a preliminary estimation of the state.The scheme is designed by introducing an additional term,which is tuned according to the higher order moment of the estimation error.The minimum error entropy criterion is introduced for updating the entropy of the innovation at each time step.According to the stochastic information gradient method,an optimal filer gain matrix is obtained.The mean square error criterion is limited to the assumption of linearity and Gaussianity.However,non-Gaussian noise is often encountered in many practical environments and their performances degrade dramatically in non-Gaussian cases.Most of the existing multipath estimation algorithms are usually designed for Gaussian noise.The I(in-phase)and Q(quadrature)accumulator outputs from the GPS correlators are used as the observational measurements of the EKF to estimate the multipath parameters such as amplitude,code delay,phase,and carrier Doppler.One reasonable way to obtain an optimal estimation is based on the minimum error entropy criterion.The MEEKF algorithm provides better estimation accuracy since the error entropy involved can characterize all the randomness of the residual.Performance assessment is presented to evaluate the effectivity of the system designs for GPS code tracking loop with multipath parameter estimation using the minimum error entropy based extended Kalman filter.

状态受限机械臂的固定时间收敛双环自适应控制方法

针对机械臂轨迹跟踪控制中存在状态有界、参数摄动和跟踪时间不能预知的实际工程问题,提出一种固定时间收敛的双环自适应跟踪控制算法。该算法可根据控制参数预估机械臂轨迹跟踪时间,保证轨迹跟踪误差在预设有界范围内变化,且对系统内部参数摄动和外部干扰具有较强鲁棒性。数值仿真结果表明,该算法结构简单,具有较好的控制效果和工程应用前景。

Digital implementation and analysis of a high dynamic frequency tracking loop

In the wireless guidance system, the signals that receiver received has obvious Doppler shift for the high dynamic characteristic of the carrier. A new solution of carrier frequency tracking loop with frequency modifying system is put forward. The characteristic of cross product auto frequency control and the second order loop filter in this loop are analyzed. The simulation shows that this loop can accomplish frequency tracking well in high dynamic circumstance.

双回路控制下拖拉机发动机管理系统的设计

随着拖拉机发动机控制系统的复杂性在不断增加,拖拉机发动机扭矩管理系统需要满足多种工况需求,配备多种传感器和执行器,同时具备高效能和燃油经济性。为此,设计了基于双回路速度跟踪控制的拖拉机发动机扭矩管理系统,通过两个回路实现对发动机扭矩的精确控制,其中一个回路用于速度跟踪,另一个回路用于调节发动机扭矩。通过精确的速度控制和扭矩管理,系统可以在不同工况下实现高效的能量利用和优化的运行性能。试验结果表明:系统能够有效地实现发动机扭矩的准确控制,提高了拖拉机的整体性能和燃油经济性。研究结果旨在改进拖拉机发动机控制系统的性能,提高其适应多种工况的能力,并实现更高的燃油经济性。

双闭环PID应用下投篮机器人路径跟踪控制研究

投篮机器人路径图像噪声会影响机器人路径跟踪控制效果,导致投篮机器人偏离正常轨迹,为此提出双闭环PID应用下投篮机器人路径跟踪控制方法。分析投篮机器人架构,利用OpenMv视觉识别方法采集投篮机器人路径图像,结合小波阈值算法对采集到的图像实施去噪处理,从而获取清晰的投篮机器人路径图像。根据图像去噪处理结果,将曲线拟合法与特征点检测法相结合,实现投篮机器人路径识别。根据投篮机器人路径识别结果确定路径实际偏移量,结合推动器实现位置、移动速度建立的双闭环PID控制器,从而实现投篮机器人路径跟踪控制。实验结果表明,该方法的投篮机器人路径图像去噪熊效果好、跟踪控制效果好,充分验证了该方法的有效性。

基于双环自适应滑模的移动机器人轨迹跟踪控制

为了提升移动机器人轨迹跟踪精度,针对传统双环控制内外环协调性差、抗扰性弱的问题,文章提出双环自适应滑模的控制方法。为消除传统滑模控制(sliding mode control, SMC)方法中的趋近阶段,设计新型时变积分终端滑模控制器以保证系统状态始终位于滑模面,并通过控制器参数调节实现内环姿态误差和外环位置误差的快速收敛;构建基于势垒函数的增益调控方法,保证在扰动上界未知的情况下有效地抑制状态抖振,提高轨迹跟踪系统的抗干扰能力。对所提方法进行的验证分析结果表明,相较于现有的双环控制方法,该文轨迹跟踪控制方法精度更高、鲁棒性更强。

智能采摘机器人路径规划的设计与研究

以四足轮式采摘机器人为研究载体,将采集的果园图像经过灰度化、阈值分割、几何校正、比例尺寸划分等处理,然后进行栅格化;在此基础上,对采摘机器人在作业时的路径进行全局规划,通过蚁群算法寻找出一条无障碍、短距离的行驶路线;同时,结合运动学模型和PID闭环等现代控制理论,将得到的路径信息转化为控制信号,输出占空比变化的PWM波,从而控制电机运转,使得采摘机器人以规定的速度跟踪已规划好的行驶路线;最后,将此理论以嵌入式方式进行软硬件开发,设计出一款路径规划-跟踪控制系统。实验结果表明,利用路径规划-跟踪控制系统的采摘机器人按规划的路径到达目标点的平均概率为94.5%,能够准确、有效地辅助采摘机器人进行采摘作业。

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.

酸轧活套基础崩塌原因分析及改进方案

针对邯钢一冷酸轧线入口活套基础出现的崩塌现象进行了详细的原因分析,根据不同的原因采取了相应的改进措施,并且设计一种酸轧线活套内轨道基础维修装置。此装置加工简单,安装省时,且安装时可以分阶段完成。解决了传统的重新浇筑、灌浆方法恢复损坏轨道基础时间过长的限制,实现快速完成对损坏轨道基础的维修,减少酸轧线的日常检维修时间,确保了酸轧线的正常高效生产节奏。

基于YOLOv5和状态反馈的内燃机转速自动闭环跟踪控制

为了减少内燃机转速自动闭环跟踪控制时间,提出基于YOLOv5和状态反馈的内燃机转速自动闭环跟踪控制方法。通过传感器采集内燃机的转速信息,并结合对应的下降沿关系分析变化信息;分析内燃机的电机结构图,通过电机参数获得转速上限;基于YOLOv5跟踪闭环信息,建构自动闭环策略,通过状态反馈控制转速闭环流程;结合YOLOv5和状态反馈,实现内燃机转速自动闭环跟踪控制。实验结果表明,本文方法的转速跟踪控制收敛时间为13.7s,具有较快的收敛速度。

基于高动态环境下B2a信号的双通道跟踪算法

在北斗三号B2a信号中,针对在高动态环境下信号多普勒变化较大,导致导航接收机跟踪环路收敛速度较慢、稳定性差等问题,基于北斗B2a信号传统跟踪环路算法设计出基于三阶锁频辅助四阶锁相的双通道联合跟踪载波跟踪环,并对此跟踪算法进行仿真分析。实验结果表明双通道联合跟踪算法对信号的利用率明显提升且环路收敛速度快,在信号较差的情况下也能实现稳定跟踪,并且稳定性和准确度明显提升。

基于负载追踪补偿的大电流LDO设计

提出一种有效提升大电流输出应用的低压差线性稳压器(LDO)环路稳定性的技术,采用负载追踪补偿方式消除电路输出端与负载相关的极点对环路稳定性的影响,且在维持环路低频增益不变的前提下降低高频下环路中节点阻抗,从而达到同时提升输出精度和优化瞬态响应性能的目的。采用TSMC 0.18µm BCD工艺进行仿真验证,结果表明电路最大输出电流6 A,在6 A/6μs的负载突变情况下输出电压下冲为36.6 mV,过冲为35.3 mV,稳定时间小于56.3μs。全负载电流范围内,瞬态性能大幅提升。

多相关器联合功率GNSS欺骗干扰检测方法研究

GNSS民用信号因其公开性和脆弱性易受外界欺骗干扰.作为欺骗干扰检测的有效方法,信号质量监测(signal quality monitoring,SQM)技术通过检测接收机跟踪环路早码、即时码、晚码(early late phase,ELP)的相关结果,与无欺骗时的相关特性对比,判断是否存在欺骗干扰.常规SQM算法仅利用ELP三个信息,检测性能受限,为此提出多相关器联合功率(SQM detection of power combined Multi-correlator groups,SPCM)算法.以ELP之间多个等间隔相关器输出功率的加权为检测量,且取相关时刻与即时码时间差的反比为加权系数;进一步分析检测量的概率分布特性,并基于Neyman-Pearson理论确定最佳检测阈值,通过比较检测量与检测阈值的大小,判断是否存在欺骗干扰.基于美国德克萨斯大学奥斯汀分校公开的场景四数据集进行试验,结果表明:与Ratio和ELP等典型SQM算法相比,在不同虚警率条件下,所提出SPCM算法兼具高检测概率和快速预警响应时间性能.

星基GNSS掩星事件预报方法分析

针对全球卫星导航系统(GNSS)星基掩星观测时长通常仅有几十秒,特别是在升星掩星观测中,需要快速实现负高度角卫星信号的捕获跟踪,才能获得及时有效的掩星观测时长的问题,基于先验轨道信息辅助的开环跟踪技术,提出一种基于切线高度的掩星事件快速预报方法,以辅助掩星接收机快速捕获和跟踪GNSS掩星信号,从而保证掩星观测数据质量和有效观测时长:对地球局部曲率中心进行修正,得到更为精准的切线高度;然后设置掩星事件的判决条件,采用极值的方式快速预报出符合阈值的掩星事件;最后对全球内曲率中心和曲率半径进行分析。实验结果表明,曲率中心的修正距离最大值可至45 km,曲率半径波动范围可达到65 km,足以影响掩星探测的准确预报。基于气象、电离层和气候星座观测系统(COSMIC-2)实测数据的仿真结果表明,掩星预报的全球定位系统(GPS)掩星漏报率低于3%,格洛纳斯卫星导航系统(GLONASS)掩星漏报率约14.5%,且预报掩星开始时间大多提前5~10 s;证明基于切线高度的掩星预报方法能够有效地应用于星基掩星事件的预报,以辅助接收机准确捕获和跟踪信号,提升掩星观测资料的数据量和有效观测时长。