A real-time performance improvement method for composite time scale

The composite time scale(CTS)provides a stable,accurate,and reliable time scale for modern society.The improvement of CTS’s real-time performance will improve its stability,which strengths related applications’performance.Aiming at this goal,a method achieved by determining the optimal calculation interval and accelerating adjustment stage is proposed in this paper.The determinants of the CTS’s calculation interval(characteristics of the clock ensemble,the measurement noise,the time and frequency synchronization system’s noise and the auxiliary output generator noise floor)are studied and the optimal calculation interval is obtained.We also investigate the effect of ensemble algorithm’s initial parameters on the CTS’s adjustment stage.A strategy to get the reasonable initial parameters of ensemble algorithm is designed.The results show that the adjustment stage can be finished rapidly or even can be shorten to zero with reasonable initial parameters.On this basis,we experimentally generate a distributed CTS with a calculation interval of 500 s and its stability outperforms those of the member clocks when the averaging time is longer than1700 s.The experimental result proves that the CTS’s real-time performance is significantly improved.

ROS2 Real-time Performance Optimization and Evaluation

Real-time interaction with uncertain and dynamic environments is essential for robotic systems to achieve functions such as visual perception,force interaction,spatial obstacle avoidance,and motion planning.To ensure the reliability and determinism of system execution,a flexible real-time control system architecture and interaction algorithm are required.The ROS framework was designed to improve the reusability of robotic software development by providing a distributed structure,hardware abstraction,message-passing mechanism,and application prototypes.Rich ecosystems for robotic development have been built around ROS1 and ROS2 architectures based on the Linux system.However,because of the fairness scheduling principle of the default Linux system design and the complexity of the kernel,the system does not have real-time computing.To achieve a balance between real-time and non-real-time computing,this paper uses the transmission mechanism of ROS2,combines it with the scheduling mechanism of the Linux operating system,and uses Preempt_RT to enhance the real-time computing of ROS1 and ROS2.The real-time performance evaluation of ROS1 and ROS2 is conducted from multiple perspectives,including throughput,transmission mode,QoS service quality,frequency,number of subscription nodes and EtherCAT master.This paper makes two significant contributions:firstly,it employs Preempt_RT to optimize the native ROS2 system,effectively enhancing the real-time performance of native ROS2 message transmission;secondly,it conducts a comprehensive evaluation of the real-time performance of both native and optimized ROS2 systems.This comparison elucidates the benefits of the optimized ROS2 architecture regarding real-time performance,with results vividly demonstrated through illustrative figures.

Performance analysis model for real-time Ethernet-based computer numerical control system

In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.

Performance evaluation of near real-time condition monitoring in haul trucks

Strategic maintenance plays a key role in ensuring high availability and utilization of the haul trucks,and as equipment began to grow more complex towards the end of the 20th century,there was a need for a proactive maintenance strategy,which led to the development of condition-based maintenance.Realtime condition monitoring(RTCM)is the ability to perform condition monitoring in real-time and has the ability to alert maintenance and operations of abnormal conditions.These alarms can be used as an indication leading to a problem,and if a suitable corrective action is initiated in time,it could result in significant savings of equipment downtime and repair costs.This study aims to compare some maintenance performance indicators prior to and after implementation of RTCM strategy at a mine site using some tests of statistical significance.The study also indicated the presence of seasonality in the data,and thus the data was deseasonalized and detrended prior to being subjected to the statistical tests.Finally,the results indicated that RTCM strategy has proven to be successful in improving the availability for some of the failure categories chosen in this study.

Seismic performance evaluation of VCFPB isolated storage tank using real-time hybrid simulation

Variable curvature friction pendulum bearings(VCFPB)effectively reduce the dynamic response of storage tanks induced by earthquakes.Shaking table testing is used to assess the seismic performance of VCFPB isolated storage tanks.However,the vertical pressure and friction coefficient of the scaled VCFPB in the shaking table tests cannot match the equivalent values of these parameters in the prototype.To avoid this drawback,a real-time hybrid simulation(RTHS)test was developed.Using RTHS testing,a 1/8 scaled tank isolated by VCFPB was tested.The experimental results showed that the displacement dynamic magnification factor of VCFPB,peak reduction factors of the acceleration,shear force,and overturning moment at bottom of the tank,were negative exponential functions of the ratio of peak ground acceleration(PGA)and friction coefficient.The peak reduction factors of displacement,acceleration,force and overturning moment,which were obtained from the experimental results,are compared with those calculated by the Housner model.It can be concluded that the Housner model is applicable in estimation of the acceleration,shear force,and overturning moment of liquid storage tank,but not for the sliding displacement of VCFPBs.

Optimizing Real-Time Performance of 3D Virtual Mining Environment with MultiGen Creator

System optimization plays a crucial role in developing VR system after 3D modeling, affecting the system's Immersion and Interaction performance enormously. In this article, several key techniques of optimizing a virtual mining system were discussed: optimizing 3D models to keep the polygon number in VR system within target hardware's processing ability; optimizing texture database to save texture memory with perfect visual effect; optimizing database hierarchy structure to accelerate model retrieval; and optimizing LOD hierarchy structure to speed up rendering.

Real-time performance of periodic data transmission in EPA industrial Ethernet

To evaluate and improve the real-time performance of Ethernet for plant automation（EPA） industrial Ethernet,the real-time performance of EPA periodic data transmission was theoretically and experimentally studied.By analyzing information transmission regularity and EPA deterministic scheduling mechanism,periodic messages were categorized as different modes according to their entering-queue time.The scheduling characteristics and delivery time of each mode and their interacting relations were studied,during which the models of real-time performance of periodic information transmission in EPA system were established.On this basis,an experimental platform is developed to test the delivery time of periodic messages transmission in EPA system.According to the analysis and the experiment,the main factors that limit the real-time performance of EPA periodic data transmission and the improvement methods were proposed.

Real-time hybrid simulation of structures equipped with viscoelastic-plastic dampers using a user-programmable computational platform

A user-programmable computational/control platform was developed at the University of Toronto that offers real-time hybrid simulation （RTHS） capabilities. The platform was verified previously using several linear physical substructures. The study presented in this paper is focused on further validating the RTHS platform using a nonlinear viscoelastic-plastic damper that has displacement, frequency and temperature-dependent properties. The validation study includes damper component characterization tests, as well as RTHS of a series of single-degree-of-freedom （SDOF） systems equipped with viscoelastic-plastic dampers that represent different structural designs. From the component characterization tests, it was found that for a wide range of excitation frequencies and friction slip loads, the tracking errors are comparable to the errors in RTHS of linear spring systems. The hybrid SDOF results are compared to an independently validated thermal- mechanical viscoelastic model to further validate the ability for the platform to test nonlinear systems. After the validation, as an application study, nonlinear SDOF hybrid tests were used to develop performance spectra to predict the response of structures equipped with damping systems that are more challenging to model analytically. The use of the experimental performance spectra is illustrated by comparing the predicted response to the hybrid test response of 2DOF systems equipped with viscoelastic-plastic dampers.

Performance verification and comparison of TianLong automatic hypersensitive hepatitis B virus DNA quantification system with Roche CAP/CTM system

AIM To investigate and compare the analytical and clinical performance of Tian Long automatic hypersensitive hepatitis B virus(HBV) DNA quantification system and Roche CAP/CTM system.METHODS Two hundred blood samples for HBV DNA testing, HBV-DNA negative samples and high-titer HBV-DNA mixture samples were collected and prepared. National standard materials for serum HBV and a worldwide HBV DNA panel were employed for performance verification. The analytical performance, such as limit of detection, limit of quantification, accuracy, precision, reproducibility, linearity, genotype coverage and cross-contamination, was determined using the Tian Long automatic hypersensitive HBV DNA quantification system(TL system). Correlation and Bland-Altman plot analyses were carried out to compare the clinical performance of the TL system assay and the CAP/CTM system. RESULTS The detection limit of the TL system was 10 IU/m L, and its limit of quantification was 30 IU/m L. The differences between the expected and tested concentrations of the national standards were less than ± 0.4 Log10 IU/m L, which showed high accuracy of the system. Results of the precision, reproducibility and linearity tests showed that the multiple test coefficient of variation(CV) of the same sample was less than 5% for 102-106 IU/m L; and for 30-108 IU/m L, the linear correlation coefficient r2 = 0.99. The TL system detected HBV DNA(A-H) genotypes and there was no cross-contamination during the "checkerboard" test. When compared with the CAP/CTM assay, the two assays showed 100% consistency in both negative and positive sample results(15 negative samples and 185 positive samples). No statistical differences between the two assays in the HBV DNA quantification values were observed(P > 0.05). Correlation analysis indicated a significant correlation between the two assays, r2 = 0.9774. The Bland-Altman plot analysis showed that 98.9% of the positive data were within the 95% acceptable range, and the maximum difference was-0.49.CONCLUSION The TL system has good analytical performance, and exhibits good agreement with the CAP/CTM system in clinical performance.

REAL-TIME SOFTWARE SYSTEM FOR PRODUCTION PROCESS SUPERVISION

The real-time software system for production process supervision is a inte-gral system,including on-line function subsystem for supervision and off-line auxiliarysubsystem for development and diagnosis.This paper introduces a real-time software sys-tem which has been used in a power station for monitoring a large capacity thermal gener-ating unit.The subsystems,environment,performance and development of the system areexplained,and the common problems about real-time software system are described.

Design of Intelligent Network Performance Analysis & Forecast Support System

A system designed for supporting the network performance analysis and forecast effort is presented, based on the combination of offline network analysis and online real-time performance forecast. The off-line analysis will perform analysis of specific network node performance, correlation analysis of relative network nodes performance and evolutionary mathematical modeling of long-term network performance measurements. The online real-time network performance forecast will be based on one so-called hybrid prediction modeling approach for short-term network, performance prediction and trend analysis. Based on the module design, the system proposed has good intelligence, scalability and self-adaptability, which will offer highly effective network performance analysis and forecast tools for network managers, and is one ideal support platform for network performance analysis and forecast effort.

基于Telemetry的OTN设备性能采集系统研究

【目的】软件定义网络(SDN)设备规模日益增大,承载的业务越来越多。针对传统光传送网(OTN)设备使用简单网络管理协议(SNMP)采集性能数据不能解决大规模和高性能网络管理的问题,文章提出了基于Telemetry架构的OTN设备性能采集系统。【方法】通过设计分布式数据模型转换和数据编码架构,提高数据转换和编码效率以及采集系统的规模,同时均衡设备算力,设备以秒级周期定时采集并上报性能数据到采集器。【结果】文章对使用SNMP和部署Telemetry系统设备的性能采集能力进行了实验对比分析。【结论】结果表明,系统在数据模型转换和编码、数据传输效率、采集数据的时效性以及数据获取的灵活性方面更有优势,满足SDN对智能运维的要求。

Multiserver Multichannel Real-Time System with Limited Maintenance Facilities under Maximum Load

We consider a multi server and multichannel real-time system with identical servers (e.g. unmanned aerial vehicles, machine controllers, etc.) that provide services for requests of real-time jobs arriving via several different channels (e.g. surveillance regions, assembly lines, etc.) working under maximum load regime. Each channel has its own constant numbers of jobs inside at any instant. Each channel has its own specifications, and therefore different kinds of equipment and inventory are needed to serve different channels. There is a limited number of identical maintenance teams (less than the total number of servers in the system). We compute analytically steady- state probabilities of this system, its availability, loss penalty function and other performance characteristics, when both service and maintenance times are exponentially distributed.

Performance Evaluation of Multiple Unmanned Aerial Vehicles Operating in General Regime with Shortage of Maintenance Facilities

We consider a real-world problem of military intelligence unit equipped with multiple identical unmanned aerial vehicles (UAV) responsible for several regions (with requests of real-time jobs arriving from independent sources). We suppose that there are no ample maintenance facilities, allowing simultaneous treatment of all vehicles if necessary. Under certain assumptions, these real-time systems can be treated using a queueing theory methodology and/or as Markov chains. We show how to compute steady-state probabilities of these systems, their performance effectiveness, and various performance parameters (for exponentially distributed service and maintenance times of UAVs, as well as tasks duration and their arrival pattern).

支持多类数据接入的航天器综合测试数据处理方法

针对当前航天器测试多类型数据接入面临瓶颈的问题,介绍了一种多类数据接入的航天器综合测试数据处理方法,主要用于提高遥测实时性、接入卫星载荷数据、处理它星遥测和处理高速率遥测等问题。详细介绍了方法的设计思想、实施方法和应用情况,经实际应用检验,该方法有效缩短了测试所需时间,扩大了测试系统数据接口和极限解码效率,提高了卫星综合测试的自动化水平,具有测试系统解码模块支持可裁剪、低耦合、高效率的数据处理优势。

一种遥测智能终端设备双CPU架构系统软件升级的方案研究

针对双CPU架构的遥测智能终端设备提出了一种基于Inotify机制与NFS文件系统的系统软件升级方案。Inotify是Linux操作系统中一种实时监控文件系统变化的机制,NFS(Network File System)文件系统是一种网络文件系统,允许用户在不同的计算机或者各节点之间共享文件和存储资源。详细介绍了该方案的设计和实现,并对方案的性能进行了分析和评估。实验结果表明,该方案具有较高的实时性和可靠性,可有效提高遥测智能终端设备多CPU架构的升级效率。

基于模型驱动双向主动测量协议的IP网络遥测系统研究与实现

IP层的OAM技术中,双向主动测量协议(TWAMP)通过主动向网络注入测量报文,并根据对测量报文进行采集分析来实现任意2个具备IP可达性网络节点之间的网络层性能监测。文章首先分析了TWAMP测量方案在实际运营部署时存在的主要问题和挑战,然后针对网络的运维管理日益智能化的网络发展趋势下,需要对网络运行状况进行连续实时主动监测的新需求进行了相关分析。基于此,文章提出了一种面向互联网遥测架构的硬探针TWAMP网络监控系统,以此实现IP传送网的性能监测改进,为实现更实时可靠的智能运营提供有力支撑。

基于卫星在轨温度预示热控涂层性能退化的方法

介绍了一种利用卫星在轨温度数据预示热控涂层在轨性能退化情况的方法,建立并推导了适用于研究热控涂层随整数年变化规律的数学模型,该模型利用卫星设备的温度曲线通过反演计算得到设备表面热控涂层的退化数据。为检验本文数学模型的计算效果,构造了一组数值试验,结果表明本文数学模型的计算数据与真实值非常接近,说明本文建立的数学模型能够很好地根据卫星在轨温度计算出热控涂层在轨退化数据。

田间作业机具综合性能遥测系统

针对农机具田间作业性能测试时运行环境恶劣、在线测试距离受限、测试参数有限等问题,设计开发了一种新型的田间作业机具综合性能遥测系统。该系统基于无线通讯技术,采用"PC+PAC"的上下位机方式测试田间作业机具作业性能。其中,上位机采用四通组态开发,提高了系统的可靠性和人机界面的友好性;下位机采用VB2008开发数据采集处理程序,完成作业机具工作性能参数以及拖拉机常规性能参数的采集和处理工作,提高了系统响应的实时性和可靠性。

飞行试验遥测机载测试技术的发展与应用

随着现代飞机的先进性、复杂性和高度综合性的增强,在飞行试验测试中需要测量与记录的参数快速增长。在分析了国内外飞行试验遥测中机载数据采集系统现状之后,描述了我国飞行试验遥测面临的机遇与挑战,指出了飞行试验遥测系统网络化发展方向,最后提出了构建机载网络化采集记录系统的总体思路和研制的主要性能要求。