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.

Comparison of delay compensation methods for real-time hybrid simulation using frequency-domain evaluation index

The delay compensation method plays an essential role in maintaining the stability and achieving accurate real-time hybrid simulation results. The effectiveness of various compensation methods in different test scenarios, however, needs to be quantitatively evaluated. In this study, four compensation methods （i.e., the polynomial extrapolation, the linear acceleration extrapolation, the inverse compensation and the adaptive inverse compensation） are selected and compared experimentally using a frequency evaluation index （FEI） method. The effectiveness of the FEI method is first verified through comparison with the discrete transfer fimction approach for compensation methods assuming constant delay. Incomparable advantage is further demonstrated for the FEI method when applied to adaptive compensation methods, where the discrete transfer function approach is difficult to implement. Both numerical simulation and laboratory tests with predefined displacements are conducted using sinusoidal signals and random signals as inputs. Findings from numerical simulation and experimental results demonstrate that the FEI method is an efficient and effective approach to compare the performance of different compensation methods, especially for those requiring adaptation of compensation parameters.

Real-time lane departure warning system based on principal component analysis of grayscale distribution and risk evaluation model

A technology for unintended lane departure warning was proposed. As crucial information, lane boundaries were detected based on principal component analysis of grayscale distribution in search bars of given number and then each search bar was tracked using Kalman filter between frames. The lane detection performance was evaluated and demonstrated in ways of receiver operating characteristic, dice similarity coefficient and real-time performance. For lane departure detection, a lane departure risk evaluation model based on lasting time and frequency was effectively executed on the ARM-based platform. Experimental results indicate that the algorithm generates satisfactory lane detection results under different traffic and lighting conditions, and the proposed warning mechanism sends effective warning signals, avoiding most false warning.

Research on Fuzzy Synthetic Evaluation of Stamping Process Scheme

Stamping process,which is widely used in automobile,aerospace,machine-building industries,and etc.,is a creative process needing time and experiences.The lead time is mainly spent on stamping die design and manufacturing.As the ba- sis of die design,process design is a non-linearity and creative process,which can be solved by using the fuzzy synthetic evaluation. In this paper,the potential o f fuzzy synthetic evaluation for dealing with stamping process design was explored.The influencing factor set,factor weight set,evaluation set,single factor fuzzy evaluation matrix,and fuzzy synthetic evaluation scheme were studied.Finally,the washer part,considering forming equipment,part dimensions and other factors,was selected to testify the evaluation process.

Towards Cache-Assisted Hierarchical Detection for Real-Time Health Data Monitoring in IoHT

Real-time health data monitoring is pivotal for bolstering road services’safety,intelligence,and efficiency within the Internet of Health Things(IoHT)framework.Yet,delays in data retrieval can markedly hinder the efficacy of big data awareness detection systems.We advocate for a collaborative caching approach involving edge devices and cloud networks to combat this.This strategy is devised to streamline the data retrieval path,subsequently diminishing network strain.Crafting an adept cache processing scheme poses its own set of challenges,especially given the transient nature of monitoring data and the imperative for swift data transmission,intertwined with resource allocation tactics.This paper unveils a novel mobile healthcare solution that harnesses the power of our collaborative caching approach,facilitating nuanced health monitoring via edge devices.The system capitalizes on cloud computing for intricate health data analytics,especially in pinpointing health anomalies.Given the dynamic locational shifts and possible connection disruptions,we have architected a hierarchical detection system,particularly during crises.This system caches data efficiently and incorporates a detection utility to assess data freshness and potential lag in response times.Furthermore,we introduce the Cache-Assisted Real-Time Detection(CARD)model,crafted to optimize utility.Addressing the inherent complexity of the NP-hard CARD model,we have championed a greedy algorithm as a solution.Simulations reveal that our collaborative caching technique markedly elevates the Cache Hit Ratio(CHR)and data freshness,outshining its contemporaneous benchmark algorithms.The empirical results underscore the strength and efficiency of our innovative IoHT-based health monitoring solution.To encapsulate,this paper tackles the nuances of real-time health data monitoring in the IoHT landscape,presenting a joint edge-cloud caching strategy paired with a hierarchical detection system.Our methodology yields enhanced cache efficiency and data freshness.The corroborative numerical data accentuates the feasibility and relevance of our model,casting a beacon for the future trajectory of real-time health data monitoring systems.

A lateral-immobilization zebrafish microfluidic chip-based system for in vivo real-time evaluation of antithrombotic agents

Thrombosis remains a major global health concern mainly characterized by high rates of morbidity and mortality.Animal models serve as an indispensable tool to understand the underlying pathogenesis of thrombosis and assess the efficacy of novel antithrombotic drugs.Currently,zebrafish has emerged as a valuable model organism for thrombosis research.However,the traditional method of studying zebrafish thrombosis requires a laborious and time-consuming procedure,including anesthesia and manual immobilization of zebrafish.In this study,based on hydrodynamic force,a lateral-immobilization zebrafish microfluidic chip(LIZMC)was designed to evaluate the cardiovascular system of multiple larvae within a single microscope field of view.Specifically,coupling with microscope imaging,real-time monitoring of the peripheral blood circulation in the tail of phenylhydrazine(PHZ)-induced zebrafish thrombosis was enabled.Furthermore,the reliability of LIZMC for in vivo evaluation of antithrombotic agents in zebrafish was verified using aspirin.Collectively,this novel LIZMC-based system can be used for in vivo zebrafish thrombosis studies and rapid screening of antithrombotic agents.

Deployment Dynamic Modeling and Driving Schemes for a Ring-Truss Deployable Antenna

Mesh reflector antennas are widely used in space tasks owing to their light weight,high surface accuracy,and large folding ratio.They are stowed during launch and then fully deployed in orbit to form a mesh reflector that transmits signals.Smooth deployment is essential for duty services;therefore,accurate and efficient dynamic modeling and analysis of the deployment process are essential.One major challenge is depicting time-varying resistance of the cable network and capturing the cable-truss coupling behavior during the deployment process.This paper proposes a general dynamic analysis methodology for cable-truss coupling.Considering the topological diversity and geometric nonlinearity,the cable network's equilibrium equation is derived,and an explicit expression of the time-varying tension of the boundary cables,which provides the main resistance in truss deployment,is obtained.The deployment dynamic model is established,which considers the coupling effect between the soft cables and deployable truss.The effects of the antenna's driving modes and parameters on the dynamic deployment performance were investigated.A scaled prototype was manufactured,and the deployment experiment was conducted to verify the accuracy of the proposed modeling method.The proposed methodology is suitable for general cable antennas with arbitrary topologies and parameters,providing theoretical guidance for the dynamic performance evaluation of antenna driving schemes.

Neural Network Based Multi-level Fuzzy Evaluation Model for Mechanical Kinematic Scheme

To implement a quantificational evaluation for mechanical kinematic scheme more effectively,a multi-level and multi-objective evaluation model is presented using neural network and fuzzy theory. Firstly,the structure of evaluation model is constructed according to evaluation indicator system. Then evaluation samples are generated and provided to train this model. Thus it can reflect the relation between attributive value and evaluation result,as well as the weight of evaluation indicator. Once evaluation indicators of each candidate are fuzzily quantified and fed into the trained network model,the corresponding evaluation result is outputted and the best alternative can be selected. Under this model,expert knowledge can be effectively acquired and expressed,and the quantificational evaluation can be implemented for kinematic scheme with multi-level evaluation indicator system. Several key problems on this model are discussed and an illustration has demonstrated that this model is feasible and can be regarded as a new idea for solving kinematic scheme evaluation.

Overall Evaluation of the Control Schemes of Automobile Pollution and Its Multi-Target Decision

Various control schemes of automobile pollution are comprehensively evaluated by using the weighting and feyzzy methods, from which several feasible schemes are selected, and then mulit-target decision is made by using the minimum distance and hierarcby analysis methods, for determining the optimal control methods of automobile pollution.

Construction scheme comparison with comprehensive evaluation of independent perspectives

Considering both the characteristics of construction scheme evaluation and the lack of consideration of index proportionality after introducing comprehensive evaluation of independent perspectives into construction scheme evaluation, a construction scheme evaluation model of independent perspectives was put forward through the study and optimization of comprehensive evaluation of independent perspectives. The feasibility and rationality of the optimized method were illustrated through a case study and the evaluation results were compared between the optimized method and non-optimized method. The optimized method has the practical value in construction scheme comparison.

Evaluation of the maintenance window scheme using fuzzy soft set theory

The maintenance window scheme(MWS) is one of the most important railway transportation organizational plans and plays an important role in ensuring railway operational safety. However, MWS setting is a very complicated process, and most countries currently do so with the help of a computer-aided decision system. In general, a decision system can generate multiple alternatives for MWS within an acceptable time. Therefore, how to choose the best option from the alternatives is a vital decision. This paper presents a novel framework for MWS evaluation based on the Chinese railway system. Specifically, the requirements of each department related to MWS setting are analysed, and we construct an evaluation indicator system for MWS based on the preferences of different departments. Then, we apply the fuzzy soft set theory to MWS evaluation, a method that not only effectively deals with evaluation of uncertain information, but also gives flexibility for experts to input their subjective judgment.Additionally, using the ‘‘AND’’ operation of soft set theory allows combing evaluation information from multiple evaluators to give comprehensive results. Finally, a case study illustrates the proposed framework, showing that the proposed evaluation indicator system and evaluation method are effective and practical.

An Efficient Crash Recovery Technique for Real-Time Main Memory Database

This paper presents an efficient recovery scheme suitable for real-time mainmemory database. In the recovery scheme, log records are stored in non-volatile RAM which is dividedinto four different partitions based on transaction types. Similarly, a main memory database isdivided into four partitions based data types. When the using ratio of log store area exceeds thethreshold value, checkpoint procedure is triggered. During executing checkpoint procedure, someuseless log records are deleted. During restart recovery after a crash, partition reloading policyis adopted to assure that critical data are reloaded and restored in advance, so that the databasesystem can be brought up before the entire database is reloaded into main memory. Therefore downtime is obvionsly reduced. Simulation experiments show our recovery scheme obviously improves thesystem performance, and does a favor to meet the dtadlints of real-time transactions.

Comprehensive Evaluation of Tahe Medium Gravity Crude

The comprehensive evaluation of Tahe medium gravity crude has demonstrated that this type of crude belongs to a intermediate base sour crude, featuring high vanadium content (103ppm), high carbon residue content, low pour point, and low acid value. Based on the crude processing conditions at SINOPEC Luoyang Petrochemical Branch Company, a proposal on the appropriate process flow scheme for processing Tahe crude oil has been raised with the main ideas presented as follows. The IBP-175 fraction is not an ideal feedstock for catalytic reforming; the 75-250 fraction is a qualified feedstock for zeolite de-waxing; the 140-230 fraction can be used to manufacture the No. 3 jet fuel through appropriate distillation range adjustment and product refining; the 175-350 fraction can be directly used to manufacture No.-10 diesel through proper refining; the atmospheric resid boiling over 350 is not suited to be used as the RFCC feedstock; the 350-520 vacuum distillate oil can be used as the FCC feedstock; and the vacuum residuum boiling over 520 is a good feedstock for manufacture of asphalt.

Evaluations on social network analysis (SNA) research in China's Mainland:A critical assessment of journal literatures

Social network analysis(SNA) has been introduced to China's Mainland since the end of last century. It is often stated that SNA research has experienced rapid growth in China over these years, but few studies have been conducted to prove the statement. This paper aims at exploring the research status and development of SNA in China by a critical assessment of journal articles. Our findings show that SNA is an evolving and diversified research area which has rich themes and topics, and can be applied to those studies on different levels, context and disciplines, and attract researchers and scholars from various fields and domains. In addition, the information community(Library & Information Science and Information Systems) plays a leading role in the SNA related researches. The paper also points out the research on SNA in China has some limitations, so it proposes several implications for the future development of SNA research from perspectives of information science.

Biological Evaluation of Water Quality for Benthos in Typical Rivers of Eastern Jilin Province

Benthos are aquatic organisms living at the bottom of water bodies for all or most of their life history.Apart from the settled and moving living,their forms of habitat are mostly attached to the hard substrate like rocks or soft bases such as mud and sand.In addition,there are benthic species that attach to the plant surfaces or other benthic animals,and inhabit the intertidal zone.In terms of feeding methods,most benthic animals feed on suspended matter and sediment.Most of them are invertebrates and are a complex ecological group.According to the size,they can be divided into macrobenthos and meio-benthos[1].Benthos are an important part of the water ecosystem.Using a typical river(Gaya River)in eastern Jilin Province,this paper analyzed the water quality,the components of benthic organisms and their biological density through sampling surveys of three typical locations in the upper,middle and lower reaches of the Gaya River.In addition,it made a biological evaluation of the water quality of the Gaya River.

Contention-Based Beaconless Real-Time Routing Protocol for Wireless Sensor Networks

This paper presents a novel real-time routing protocol, called CBRR, with less energy consumption for wireless sensor networks (WSNs). End-to-End real-time requirements are fulfilled with speed or delay constraint at each hop through integrating the contention and neighbor table mechanisms. More precisely, CBRR maintains a neighbor table via the contention mechanism being dependent on wireless broadcast instead of beacons. Comprehensive simulations show that CBRR can not only achieve higher performance in static networks, but also work well for dynamic networks.

A Mixed Real-time Algorithm for the Forward Kinematics of Stewart Parallel Manipulator

Aimed at the real-time forward kinematics solving problem of Stewart parallel manipulator in the control course, a mixed algorithm combining immune evolutionary algorithm and numerical iterative scheme is proposed. Firstly taking advantage of simpleness of inverse kinematics, the forward kinematics is transformed to an optimal problem. Immune evolutionary algorithm is employed to find approximate solution of this optimal problem in manipulator＇s workspace. Then using above solution as iterative initialization, a speedy numerical iterative scheme is proposed to get more precise solution. In the manipulator running course, the iteration initialization can be selected as the last period position and orientation. Because the initialization is closed to correct solution, solving precision is high and speed is rapid enough to satisfy real-time requirement. This mixed forward kinematics algorithm is applied to real Stewart parallel manipulator in the real-time control course. The examination result shows that the algorithm is very efficient and practical.

国土空间规划的生态服务价值评估和方案优选——基于“土地利用+生态效能”的双维复合视角

生态文明建设是国土空间规划的核心价值观,但当前对于国土空间规划方案的生态效益却缺乏定量评估的相关方法。论文对谢高地等的生态服务价值评估方法做了一定改进,并应用于国土空间规划的多情景评估和优选,定量评估规划干预带来的生态效益。首先,认为生态服务价值受土地利用类型和生态服务效能这两个维度的复合作用,并探索了生态服务效能的修正指标和修正系数。其次,解析了国土空间规划作用于这两个维度的途径,即通过用地布局规划改变土地利用类型、通过生态措施影响生态服务效能,从而提出了国土空间规划多方案的生态服务价值评估方法,以及优选优化思路。最后,结合武汉市法泗街道案例的应用示例,为国土空间规划的编制与决策提供一定参考。

钢筋混凝土拱桥加固施工次序方案及效果评价

为研究钢筋混凝土拱桥最优的加固施工次序,以一座在役4跨箱形拱桥的加固方案为背景,设计了3组针对性的加固方案,并对不同拆除加固施工次序下的主拱圈力学性能进行了分析;采用恒载应力变化率(αD)和荷载效应变化率(αN)评价了施工中拱圈的应力变化规律及加固后原拱圈的荷载效应。研究结果表明:拱上结构的拆建次序对加固后主拱圈的力学性能影响较小,但对加固过程中主拱圈的受力状态影响较大;拱顶对称拆除时αD<0,结构处于“卸载”状态,有利于拱桥施工中的受力;αN随着拱上结构恒载减小而增大,且增速减缓,故加固层材料利用率也随拱上结构恒载减小而增大,且增幅变缓;αN越大,则加固效果越好。

考虑绿色属性的改进原子聚类模块划分方法

针对企业传统模块化设计产品制造或使用时资源消耗高、故障率高、不易维护等问题,提出了一种考虑资源利用性、寿命兼容性、可维护性等绿色属性的改进原子聚类模块划分方法。通过构建多重绿色约束矩阵、价矩阵和距离矩阵,计算各部件间库仑力关系进而提出模块划分方案。利用RAHP、CRITIC和VIKOR法等建立综合评价体系,考虑模块平均聚合度、耦合度和成本均衡度等指标,对模块划分方案进行选择和优化。以工业汽轮机企业产品为例进行绿色模块划分,并与传统模块划分方法进行对比。结果表明,改进后的原子聚类模块划分方法有效提升了产品的绿色性能,满足绿色设计需求。