introducere in sisteme de timp real (real time systems)

8/10/2019 Introducere in Sisteme de timp real (Real Time Systems)

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Tiberiu Leia: Sisteme de T-R/ Real-Time SystemsIntroducere/Introduction- 2014

Occupational skills: system engineering and computer designer, softwengineer, IT project manager, software programmer, IT system designsoftware developer for process control, system analyst

Knowledge/understanding: real-time requirements real-time conceptsPractical skills:specification of real-time applications

design of real-time applicationsimplementation of real-time applicationsverification of real-time applicationsAbilities::operating under UNIX operation systems

implementation using concurrent Java and Real-time Java


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PrerequisitesBasic programmingSoftware engineering

Discrete event systems

Cours Grade:The grade for the midterm exam (M);The grade for the final exam (F);Laboratory verification (L)N=0.33M+0.33F+ 0.33L

Condition to obtain the credits : N>=5; M>=5; F>=5

M??? N= 0.66F + 0.33L

Formal or non-formal

approach?


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Cuprins C1Contents C11. Introducere - Introductiona. Paradigme - Paradigms

b.

Definiii de baz - Basic definitionsc.

Control de T-R - Real-time controli.

Tipuri de sisteme de control de T-R - Types of R-T control systems1.

Sisteme nglobate - Embedded systems2.Sisteme de control industriale - Industrial control systems

ii.

Caracteristicile sistemelor de control nglobate - Embedded contcharacteristicsd. Caractersiticile STR - RTS characteristicse.

Parametrii temporali - Temporal parametersi.

Temporizri nedeterministe -Non-deterministic timing

ii.

Evenimente - Eventsiii.

Variante de implementare a controlului - Types of contimplementations


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a. Paradigme - Paradigms

Sisteme de prelucrare - Processing systems:

batch systemssecvenialeon-line systemscu legtur directreal-time systemssisteme de timp-real

Alt punct de vedere - Another point of view:

sisteme transformaionale -transformational systemstransformational programsthey ta

some input values and process them according to their functionality (functional programmin

sisteme reactive - reactive systemsreactive programsthey react to some events

Programarea secvenial - Sequential programming

Programare paralel - Parallel programming:

Concurrent tasks Concurrent programmingThreads of executionDistributed programming


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Pervasive computing

The idea that technology is moving beyond the personal computer everyday devices with embeddedtechnology and connectivity as computidevices become progressively smaller and more powerful. Also callubiquitous computing, pervasive computing is the result of computechnology advancing at exponential speeds -- a trend toward all man-maand some natural products having hardwareand software.

Pervasive computing goes beyond the realm of personal computers: it is tidea that almost any device, can be imbedded with chips to connect tdevice to an infinite network of other devices. The goal of pervasicomputing, which combines current network technologies with wirelcomputing, voice recognition, Internetcapability and artificial intelligenis to create an environment where the connectivity of devices is embedd

in such a way that the connectivity is unobtrusive and always availab
http://www.webopedia.com/TERM/P/embedded_system.htmlhttp://www.webopedia.com/TERM/P/hardware.htmlhttp://www.webopedia.com/TERM/P/software.htmlhttp://www.webopedia.com/TERM/P/chip.htmlhttp://www.webopedia.com/TERM/P/voice_recognition.htmlhttp://www.webopedia.com/TERM/P/Internet.htmlhttp://www.webopedia.com/TERM/P/artificial_intelligence.htmlhttp://www.webopedia.com/TERM/P/artificial_intelligence.htmlhttp://www.webopedia.com/TERM/P/Internet.htmlhttp://www.webopedia.com/TERM/P/voice_recognition.htmlhttp://www.webopedia.com/TERM/P/chip.htmlhttp://www.webopedia.com/TERM/P/software.htmlhttp://www.webopedia.com/TERM/P/hardware.htmlhttp://www.webopedia.com/TERM/P/embedded_system.html


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Pervasive computing is the next generation computing environments winformation & communication technology everywhere, for everyone, at times.

I nformation and communication technologywill be an integrated part our environments: from toys, milk cartons and desktops to cars, factorand whole city areas - with integrated processors, sensors, and actuatoconnected via high-speed networks and combined with new visualizati

devices ranging from projections directly into the eye to large panoramdisplays.


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Control PanelPort1

P2

Port1

P2

User

Control ComputerP1 P2

P3

P1 P2

P3

Power UnitP1

P2

P1

P2

Plant (Technical Process)

Actuators

P2

Actuators

P2Sensors, transducers

P1

P2

P1

P2

Real Time ApplicationGeneral Structure


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b. Definiii - Basic definitions

Definitions of RTS:

STR = un sistem de prelucrare care rspunde la evenimente generate extern sau intern ntr-o

perioad de timp finit i specificat (apriori).RTS = An information processing system which has to respond to externally or internallygenerated input stimuli within a finite and specified period.

RTS= Real-time systems are those in which the correctness of the system depends not only on tlogical results of the computation but also on the time at which the results are produced (and

provided).

Source:WikipediaIn computer science, real-time computing(RToC) is the study of hardwareand softwaresystewhich are subject to a real-time constrainti.e., operational deadlines from event to systemresponse.

A non-real-t ime systemis one for which there is no deadline specified and verified, even if fast

response or high performance is desired or even preferred.
http://en.wikipedia.org/wiki/Computer_sciencehttp://en.wikipedia.org/w/index.php?title=RToC&action=edithttp://en.wikipedia.org/wiki/Computer_hardwarehttp://en.wikipedia.org/wiki/Computer_softwarehttp://en.wikipedia.org/wiki/Computer_softwarehttp://en.wikipedia.org/wiki/Computer_hardwarehttp://en.wikipedia.org/w/index.php?title=RToC&action=edithttp://en.wikipedia.org/wiki/Computer_science


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The needs of real-time software are often addressed in the context of real-time operating systemand synchronous programming languages, which provide frameworks on which to build real-timapplication software.

A real time system may be one where its application can be considered (within context) to be

mission critical.

Embedded systems

An embedded systemis a computer system designed to perform dedicated

functions with real-time computing constraints. It is embedded as part of acomplete device, which often includes hardware and mechanical parts.

Source: I 3E
http://en.wikipedia.org/wiki/Real-time_operating_systemhttp://en.wikipedia.org/wiki/Synchronous_programming_languagehttp://en.wikipedia.org/wiki/Mission_criticalhttp://en.wikipedia.org/wiki/Mission_criticalhttp://en.wikipedia.org/wiki/Synchronous_programming_languagehttp://en.wikipedia.org/wiki/Real-time_operating_system


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Tipuri de STR - Types of RTSs:

Sisteme de timp-real hard --- Hard real-time systems= systems where it isabsolutely imperative that the responses occur within the required deadline. Ex.:o

Control de timp-real --- Control Real-Time (System, Computer)o

Sisteme inginereti -- Engineering Systemso

Aplicaii critice d.p.d.v. al siguranei --- Safety-critical applicationsSisteme de T-R soft --- Soft r eal-time systems= systems where deadlines

important but the systems still functions if the deadlines are occasionally missed. E.g.:multimedia applications.

Sisteme de T-R ferme --- F irm real-time systems= systems where if some

responses (reactions) are missing the deadlines they are not necessary (usefully) any more, bthe consequences are not disastrous.

Most of control systems are real-time systems.

Many people consider only the hard real-time systems as real-time systems.Constrngeri de timp-real - Real-time constraints:

constrngeri de T-R hard --- hard real-time constraints

constrngeri de T-R soft --- soft real-time constraints


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c. Control de T-R - Real-Time Control

Real-Time

Systems

Computer

EngineeringControl

Engineering


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Tipuri - Types of Real-Time Control Systems1. Sisteme nglobate (ncorporate) - Embedded Systems

dedicated control systemsthe computer is an embedded part of some piece ofequipment

they contain microprocessors (microcontrollers), real-time kernels, RTOSE.g.: aerospace, industrial robots, vehicular systems (cars, automotive), washing machinhealth, home applications, etc.

2. Sisteme de control industrial - Industrial Control Systems

distributed control systems (DCS),programmable logic controllers (PLC),hierarchically organized,

process industry,manufacturing industry,


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Caracteristicile sistemelor de control nglobate - Embedded Control Characteristics 1:

Limited computing and communication resourcesresource efficiencyIncluded in some products, (vehicles, tools, etc.)CPU time is limited,

Lrgimea de band -- Communication bandwidth,Energy,Memory,

Mod autonom de operare -- Autonomous operationNo human operator in the loopAu mai multe cazuri de utilizare i o funcionalitate complex -- Several use-cases and comp

functionalityDeseori au nevoie de programe mari -- Often are necessary large amounts of software

Deseori necesit garanii bazate pe demonstraii formale -- Often are necessary forguarantees


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Caracteristici 2 -- Embedded Control Characteristics 2: Eficien cu resurse limitate -- Limited resources Efficiency

Eficiena dimensiunii codului -- -Code-size efficiencyEficiena n timpului execuiei -- -Run-time efficiencyEficiena utilizrii energiei -- -Energy efficiency

Eficienta greutii i dimensiunii -- -Weight and size efficiencyEficiena costului -- -Cost efficiency

ncredere n operarea autonom -- Autonomous Operation Dependabilityncredere -- -ReliabilityDisponibilitate -- -AvailabilitySiguran -- -Safety

Securitate -- -Securityntreinere -- -Maintainability

It is known that approximately 98%of all processors produced are used in embeddedapplications.

There are more than 16 billion embedded devices employed by 2010.The value added to the final product by embedded software is much higher than the cost of the

embedded device itself.Source: I3E


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d. Caracteristicile STR -- Real-Time System Characteristics:nereversibilitate -- non-reversiblecerine temporale -- timing requirementsdeterministe i predictibile -- must be deterministic and predictable

timpi de rspuns n cazul cel mai defavorabil n loc de durata medie -- worst-case respotimes of interest rather than average-case response timesmari i complexe -- large and complexdistribuite -- distributedinteraciune strns cu hardware --- tight interaction with hardwarecritice d.p.d.v. al siguranei -- safety criticaldependente de timpul de execuie -- execution is time dependenttestarea dificil -- testing is difficultoperarea pe perioade mari de timp -- operating over long time periods


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e.Parametrii temporali --Temporal parameters

tim


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Temporizri nedeterministe -- Non-Deterministic Timing:Utilizarea n comun a resurselor -- Caused by sharing of computing resources - multiple ta

sharing the CPUpreemiunea, blocajul, inversare prioritii, variaia timpilor de execuie

-

preemptions, blocking, priority inversion, varying computation times, ...-Caused by sharing of network bandwidth

bucle de control nchise prin intermediul sistemului de comunicaie -- control loops closed ocommunication networks

ntrzieri ale interfeei de reea, ntrzieri la punerea la coad, ntrzieri de transmisie, propagi retransmisia datelor, confirmarea, pierderea pachetelor -- network interface delay, queudelay, transmission delay, propagation delay, resending delay, ACK delay, ... lost packets

Cum se poate minimiza sau elimina ne-determinismul? Cum afecteaz acesta performana?How can we minimize the non-determinism?How does the non-determinism effect control performance?


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Evenimente --- Events:Real-Time systems must respond to external and/or internal events.Periodic eventsAperiodic events - unbounded arrival frequency

Sporadic events - bounded arrival frequency

The real-time systems react to events after the calculation of the response using a certain amoof processing time. The reaction must be before the specified deadline.Often the RTS must react to more than one event during the same period of time.

Variante de implementare a controlului -- Types of control implementation:antrenate de evenimente -- -Event driven controlantrenate de timp -- -Time driven control


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introducere in sisteme de timp real (real time systems)

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