Auswahl der wissenschaftlichen Literatur zum Thema „Real time performance“

Real-time collaborative programming enables a group of programmers to edit shared source code at the same time, which significantly complements the traditional non-real-time collaborative programming supported by version control systems. However, one critical issue with this emerging technique is the lack of integration with non-real-time collaboration. Specifically, contributions from multiple programmers in a real-time collaboration session cannot be distinguished and accurately recorded in the version control system. In this study, we propose a scheme that integrates real-time and non-real-time collaborative programming with a novel workflow, and contribute enabling techniques to realize such integration. As a proof-of-concept, we have successfully implemented two prototype systems named CoEclipse and CoIDEA, which allow programmers to closely collaborate in a real-time fashion while preserving the work's compatibility with traditional non-real-time collaboration. User evaluation and performance experiments have confirmed the feasibility of the approach and techniques, demonstrated the good system performance, and presented the satisfactory usability of the prototypes.

Thesis (M.S.) -- University of Maryland, College Park, 2006.
Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Embedded control systems are gaining an increasing amount of responsibility in today's vehicles and industrial machines. As mechanical components are replaced by software, the complexity of control systems and the amount of data they are responsible for greatly increase. Generally there are two approaches to dealing with this huge amount of information, but both have flaws which can reduce system performance, or in the worst case scenario cause fatal system failures with potential to cause loss of human lives.

The two approaches are creation of large purpose-built data structures with shared variables, and implementation of a database. The first is often not scalable, becomes tremendously complex, and has high development costs, while the latter has the common downside that many databases are simply too slow. This study will explore the possibilities of using a real-time database to overcome these issues.

As part of one of their control systems, CC Systems have developed the Diagnostic Runtime Engine (DRE) which keeps track of the state of the system. The database currently used in the DRE is too slow and this thesis project aims to replace it with a Mimer SQL Real-time Edition database. This real-time database utilises a unique concept called database pointers to access data in hard real-time. Although the real-time database comes with some issues and limitations of its own, this study shows that most of them can be worked around rather easily. Implementation of the real-time database would allow the DRE to handle incoming signals more than 50 times faster than the demands, as well as heavily decrease the complexity of the DRE's source code. Mimer SQL Real-time Edition works entirely with in-memory copies of database tables, and the tables must be explicitly saved, or flushed, to the disk. In order to optimise the flush we need to know roughly how often we can expect incoming signals, but such information is currently not available. Instead this thesis draws up some important criteria that should be considered when optimising the flush performance.

The conclusion of this thesis is that implementation of Mimer SQL Real-time Edition would be beneficial for the Diagnostic Runtime Engine.

This thesis is a proof-of-concept project that aims at modify and reuse existing communication protocols of wireless vehicle to vehicle communication in order to build a prototype of a real time graphical application that runs in an embedded environment. The application is a 2D visualization of the flow of material at a quarry and is built on top of existing communication protocols that enable wireless vehicle to vehicle communication according to the 802.11p standard for intelligent transport solutions. These communication protocols have already been used within the Volvo group in other research rojects, but not in a context of a real-time graphical 2D visualization. The application runs on an ALIX embedded motherboard and combined with the necessary hardware represent one node that makes the communication network. The visualization monitors the position of every active node in the network and the flow of material between material locations and crusher that process the material at the quarry. The visualization is implemented in C/C++ using Qt 4.6.2 Graphics View framework.

International Telemetering Conference Proceedings / October 29-November 02, 1990 / Riviera Hotel and Convention Center, Las Vegas, Nevada
The performance of general purpose computers is typically measured in terms of Millions of Instructions per Second (MIPS) or Millions of Floating-Point Operations per Second (MFLOPS). Standard benchmark programs such as Whetstone, Dhrystone, and Linpack typically measure CPU speed in a single-task environment. However, a computer may have high CPU performance, but poor real-time capabilities. Therefore there is a need for performance measures specifically intended for real-time computer systems. This paper presents four methodologies, related metrics and benchmarks for objectively measuring real-time performance: (a) Tri-Dimensional Measure, (b) Process Dispatch Latency Time, (c) Rhealstone Metric, and (d) Vanada Benchmark. This proposed methodologies and related measures are applied in the performance evaluation of several real-time computer systems, and the results obtained are presented.

Simulation and performance analysis of wired and wireless Time-Critical Real-Time(TCRT) LANs is the subject of this research work. Special emphasis has been placed on deterministic Medium Access Control (MAC) method as defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.4 Token Passing Bus. Another very popular MAC method based on the IEEE 802.11 wireless LAN standard has also been investigated. The demands imposed by TCRT LANs are of a time-bounded nature which require messages to be delivered on time or within allowable delay defined by the applications they serve. A number of metrics for measuring network performance have been proposed for use throughout the thesis, specific important parameters, such as response time, waiting time, access time, and delay which greatly influence the performance of TCRT LANs have been analysed and examined in great detail. Fine tuning of these parameters was carried out to observe the influence they have on networks performance. Distinct approaches for measuring network performance are proposed and analysed. An analytical approach using mathematical models to determine network performance for different real-time process control applications is analysed and tested. The advantages and limitations of this approach are identified and evaluated for real-time applications. The second approach is modelling by simulation employing industry standards simulation tools, namely Network II.S and COMNET III. These simulation tools provide an effective platform for studying time-critical applications. Simulation models representing process control applications were created. A number of practical simulation models characterising real-time manufacturing cells have been modelled, analysed, and tested. Both simulation tools are used to model different network scenanos utilising the strengths and advantages of each. Simulation results and comparison of specific models were carried out. Network II.S is used to simulate IEEE 802.4 and COMNET III is used to simulate IEEE 802.11. A third approach based on an empirical network is investigated. Real data were collected and fed into a simulationmodel representing this practical network. Results from the simulation models were analysed and compared to evaluate the performance of the practical network and verify the simulation model. This cross-approach concept is found to be a very important way of studying performance of real-time LANs. A number of real-time network applications and scenarios representing process control applications were modelled using the various techniques. A generic network application was modelled to permit a comparison of the three methods. Most of the analyses are modelled using the simulation approach alone. This is due to the complexity and limitations involved in mathematically modelling dynamically changing situations in real-time applications. However, this approach was adopted only after having verified the correctness of the simulation models by cross referencing the results obtained from the mathematical and simulation approaches as applied to the generic (base) model. The simulation models enabled the analysis of the performance of IEEE 802.4 and IEEE 802.11 media access networks protocols used in real-time environments. Hypothetical and actual network scenarios were considered to fully investigate the effects of varying the various parameters on network performance. This research has clearly demonstrated that real-time networks impose different timing restrictions based on the applications they serve. Type of carried traffic by the real-time network plays a major role in influencing the choice of network protocols. Use of wireless network in real-time environment based on IEEE 802.11 under heavy load is ruled out under the current available proposals, however, they could be used in situation under low loading conditions serving small process control and manufacturing cells with limited number of processing elements. On the other hand, Real-time deterministic networks using access protocol based on IEEE 802.4 are found to be suitable for the most demanding network loading conditions and configurations. Simplifying the management functions of the IEEE 802.4 protocol reduces its complexity and costs of deployment without undermining its performance. This in tum will encourage more vendors to adopt the IEEE 802.4 standard for implementation in TCRT applications

This thesis presents techniques for improving building HVAC system performance in existing buildings generated using simulation-based tools and real data. Therefore, one of the aims has been to research the needs and possibilities to assess and improve building HVAC system performance. In addition, this thesis aims at an advanced utilization of building energy management system (BEMS) and the provision of useful information to building operators using simulation tools.

Buildings are becoming more complex systems with many elements, while BEMS provide many data about the building systems. There are, however, many faults and issues in building performance, but there are legislative and cost-benefit forces induced by energy savings. Therefore, both BEMS and the computer-based tools have to be utilized more efficiently to improve building performance.

The thesis consists of four main parts that can be read separately. The first part explains the term commissioning and the commissioning tool work principal based on literature reviews. The second part presents practical experiences and issues introduced through the work on this study. The third part deals with the computer-based tools application in design and operation. This part is divided into two chapters. The first deals with improvement in the design, and the second deals with the improvement in the control strategies. The last part of the thesis gives several rules for fault diagnosis developed using simulation tools. In addition, this part aims at the practical explanation of the faults in the building HVAC systems.

The practical background for the thesis was obtained though two surveys. The first survey was carried out with the aim to find the commissioning targets in Norwegian building facilities. In that way, an overview of the most typical buildings, HVAC equipment, and their related problems was obtained. An on-site survey was carried out on an example building, which was beneficial for introducing the building maintenance structure and the real hydronic heating system faults.

Coupled simulation and optimization programs (EnergyPlus and GenOpt) were utilized for improving the building performances. These tools were used for improving the design and the control strategies in the HVAC systems. Buildings with a hydronic heating system were analyzed for the purpose of improving the design. Since there are issues in using the optimization tool, GenOpt, a few procedures for different practical problems have been suggested. The optimization results show that the choice of the optimization functions influences significantly the design parameters for the hydronic heating system.

Since building construction and equipment characteristics are changing over time, there is a need to find new control strategies which can meet the actual building demand. This problem has been also elaborated on by using EnergyPlus and GenOpt. The control strategies in two different HVAC systems were analyzed, including the hydronic heating system and the ventilation system with the recovery wheel. The developed approach for the strategy optimization includes: involving the optimization variables and the objective function and developing information flow for handling the optimization process.

The real data obtained from BEMS and the additional measurements have been utilized to explain faults in the hydronic heating system. To couple real data and the simple heat balance model, the procedure for the model calibration by use of an optimization algorithm has been developed. Using this model, three operating faults in the hydronic heating system have been elaborated.

Using the simulation tools EnergyPlus and TRNSYS, several fault detection and diagnosis (FDD) rules have been generated. The FDD rules were established in three steps: testing different faults, calculating the performance indices (PI), and classifying the observed PIs. These rules have been established for the air cooling system and the hydronic heating system. The rules can diagnose the control and the component faults. Finally, analyzing the causes and the effects of the tested faults, useful information for the building maintenance has been descriptively explained.

The most important conclusions are related to a practical connection of the real data and simulation-based tools. For a complete understanding of system faults, it is necessary to provide real-life information. Even though BEMS provides many building data, it was proven that BEMS is not completely utilized. Therefore, the control strategies can always be improved and tuned to the actual building demands using the simulation and optimization tools. It was proven that many different FDD rules for HVAC systems can be generated using the simulation tools. Therefore, these FDD rules can be used as manual instructions for the building operators or as a framework for the automated FDD algorithms.

Denne avhandlingen presenterer noen fremgangsmåter for forbedring av ytelser for VVS-tekniske anlegg i eksisterende bygninger basert på bruk av simuleringsverktøy og virkelige måledata. Ett av målene har vært å undersøke behov og muligheter for vurdering og forbedring av ytelser for VVS-anlegg i bygninger. I tillegg har denne avhandlingen hatt som mål å fremme bruk av SD-anlegg samt å fremskaffe nyttig informasjon til driftspersonalet.

Bygninger blir stadig mer kompliserte systemer som inneholder flere og flere komponenter mens SD-anlegg håndterer en stadig større mengde data fra bygningsinstallasjoner. På den ene siden registreres det ofte feil og problemer med hensyn til ytelsene til de VVS-tekniske installasjonene. På den andre siden innføres det stadig strengere lovmessige pålegg og kost-nyttekrav motivert i energieffektiviseringen. SD-anlegg og databaserte verktøy bør derfor brukes mer effektivt for forbedring av ytelsene.

Avhandlingen består av fire hoveddeler hvor hver del kan leses separat. Den første delen, som er basert på literatturstudie, forklarer funksjonskontroll som begrep og prinsipper for oppbygging av verktøy for funksjonskontroll. Den andre delen presenterer praktisk erfaring og problemstillinger utviklet og behandlet i løpet av arbeidet med avhandlingen. Den tredje delen handler om anvendelse av databaserte verktøy for forbedring av ytelsen for VVS-tekniske installasjoner. Den tredje delen er delt opp i to kapitler, hvorav et handler om forbedring av systemløsninger og et om forbedring av styringsstrategier. Den siste delen presenterer flere regler for feilsøking og diagnostisering utviklet gjennom bruk av simuleringsverktøy. I tillegg gir denne delen en praktisk forklaring av feilene i de VVS-anleggene som er behandlet i undersøkelsen.

Det praktiske grunnlaget for avhandlingen er etablert gjennom to undersøkelser. Den første var en spørreundersøkelse som hadde til hensikt å kartlegge målsetninger for funksjonskontroll i norske bygninger. Gjennom dette ble det etablert en oversikt over de mest typiske bygninger med tilhørende VVS-anlegg og de mest forekommende problemene. En dypere undersøkelse ble utført på ett casebygg. Denne undersøkelsen viste seg å være nyttig både for kartlegging av betydningen av organisering av driften av bygningen og for avdekking av de virkelige feilene i det vannbårne oppvarmingssystemet.

En kobling mellom et simulerings- og et optimaliseringsprogram (EnergyPlus og GenOpt) har vært benyttet for forbedring av ytelsene for de VVS-tekniske installasjonene. Disse verktøyene har vært brukt for forbedring av både systemløsningene og styringsstrategiene for VVS-anlegg. Bygninger med vannbåren oppvarmingssystem har vært analysert for å forbedre systemløsningen. På grunn av begrensninger i bruken av optimaliseringsverktøyet GenOpt, har det blitt utviklet egne prosedyrer for håndtering av visse typer problemstillinger hvor denne begrensningen opptrer. Resultatene for optimaliseringen viser at valg av objektfunksjoner påvirker betydelig parametrene i det vannbårne oppvarmingssystemet.

Endringer i egenskapene til både bygningskonstruksjoner og utstyr som skjer på grunn av aldring over tiden, gjør det nødvendig med tilpassning av styringsstrategier slik at det virkelige behovet kan bli dekket. Denne problemstillingen har vært analysert ved bruk av EnergyPlus og GenOpt. Styringsstrategiene for to forskjellige VVS-anlegg, et vannbåret oppvarmingssystem og et ventilasjonsanlegg med varmegjenvinner har blitt behandlet. Den utviklete prosedyren for optimalisering av styringsstrategien består av følgende steg: innføring av optimaliseringsvariabler og objektfunksjon, samt utvikling av informasjonsflyt for behandling av optimaliseringsprosessen.

De virkelige data, både fra SD-anlegg og tilleggsmålinger, har vært benyttet for praktisk forklaring av feilene i oppvarmingssystemet. En prosedyre for modellkalibrering basert på bruk av en optimaliseringsalgoritme som kobler sammen de virkelige data og en enkel varmebalansemodell har blitt foreslått. Tre konkrete driftsfeil i oppvarmingssystemet har blitt belyst gjennom bruk av denne varmebalansemodellen.

Flere regler for feilsøking og diagnostisering har blitt utviklet ved hjelp av simuleringsverktøyene EnergyPlus and TRNSYS. Denne utviklingen har bestått av tre ulike steg: testing av bestemte feil, beregning av ytelsesindikatorer og til slutt klassifisering av de observerte ytelsesindikatorer. Reglene har blitt utviklet for et system av aggregater for luftkjøling og for et vannbåret oppvarmingssystem. Reglene kan diagnostisere både styringsfeil og komponentfeil. Til slutt presenteres informasjon som er nyttig for drift av VVS-tekniske installasjoner i bygninger basert på en analyse av årsakene for og virkningene av de feil som er behandlet.

De viktigste konklusjonene er knyttet til praktisk kombinasjon av virkelige måleverdier og simuleringsverktøy. Informasjon fra det virkelig liv er helt nødvendig for å få en god forståelse av feil som oppstår i anlegg. Det er også vist at potensialet som ligger i alle de data som er tilgjengelige gjennom SD-anlegg, ikke er fullt utnyttet. Gjennom bruk av simuleringsverktøy kan styringsstrategiene alltid bli bedre tilpasset og innjustert til de virkelige behov i bygningen. Simuleringsverktøy kan også brukes for utvikling av prosedyrer for feilsøking og diagnostisering i VVS-tekniske anlegg. Disse prosedyrene kan brukes enten som en veileder for manuell feilsøking og detektering eller som grunnlag for utvikling av automatiserte algoritmer.

Paper II, VI and VII are reprinted with kind permission from Elsevier, sciencedirect.com

In this report is documented the research, tests and conclusions of a thesis work with the aim of investigating the possibilities of running real-time tasks in a virtualization environment. First we introduce the reader to the concepts and technology we will be touching on, and then we investigate the available solutions. We find that most of these are merely in a theoretical or development stage, and so we evaluate them theoretically. We also attempt to test one of the solutions that are fully developed and available, but fail because of issues related to the design of the solution. Based on our experiences and evaluations we come to the conclusion that the solutions available are lacking, and we give a suggestion of our own that we think should address the issues we have found.