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S t u d i e n g a n g S o f t w a r e E n g i n e e r i n g - R e a l t i m e S y s t e m s Realtime- (Operating)- Systems
Studiengang Software Engineering - Realtime Systems
Realtime-(Operating)-
Systems
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Studiengang Software Engineering - Realtime Systems
What is a real-time system?
• DIN-Norm:• To respond in a nameable and guaranteed
time • To random and external signals• the exact size of this time is deliberately not stated .
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Studiengang Software Engineering - Realtime Systems
Hard Realtimesystem
• The system should under no circumstances miss thedeadline.
• Results are useless if they arrive too late.
• Catastrophic consequences if a deadline is notrespected.
• Very high cost of missed deadlines.
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Studiengang Software Engineering - Realtime Systems
Soft Realtimesystems
• Deadlines can be missed
• Low costs when late arrival of results.
• Accepting a lower performance for a delay
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Studiengang Software Engineering - Realtime Systems
Realtime-Operating-Systems
• Often there is confusion about the meaning of Real-Time-System and Real-Time-OperatingSystem:
• A special real-time OS allows us to buil a hard real-time system.
• Examples of RT-OS: QNX, RTOS, OS-9, Lynx-OS (NT), etc.
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Studiengang Software Engineering - Realtime Systems
Requirements
1st It must be multithreaded and preemtive. 2nd Thread priorities must be present. 3rd The OS must support predictable threadsynchronization algorithms. 4th Priority inheritance must exist. 5th The operating system behavior must be known.
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Studiengang Software Engineering - Realtime Systems
Examples
• Chorus / ClassiX 3.1• Chorus / JaZZ• Softworks für WinNT• Softworks für UNIX• RTOS-UH• LynxOS• OSEKplus• Adwin-System• RDE/2• WinNT + DIAdem 6
Studiengang Software Engineering - Realtime Systems
An overview for the RealtimeOS
QNX
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Studiengang Software Engineering - Realtime Systems
QNX
• QNX Software Systems Company founded in 1980 QNX currently in over 100 countries usedApplications: Medical technology (such as blood donor system Rx: QNX) Automotive technology (such as autonomous driving by VW) Air & Space (such as 3D positioning cargo for the spaceshuttle's) Process control (such as real-time visualization) Telecommunications (eg multimedia phone cards of British Telecom) Consumer Electronics (z.B WebPad of Cyrix)
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Studiengang Software Engineering - Realtime Systems
Functions and Characteristics of QNX
• General: Management of the resources of a computer
QNX: Hard real time by multitasking capability and priority, predatory schedulingMicro-kernel, modular design and message basedcommunication processesGraphical user interface with the "photon microGUIWindowing System
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Studiengang Software Engineering - Realtime Systems
Hard Realtime Scheduling
• Priority, predatory scheduling
Temperatur inside
Realtimsystem
Wheelsensor
ABS
Aircondition
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Studiengang Software Engineering - Realtime Systems
Latency
• The Interrupt-Latency
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Studiengang Software Engineering - Realtime Systems
Aufgaben und Eigenschaftenvon QNX
• Allgemein: – Verwaltung der Ressourcen eines Computers
• QNX:– Harte Echtzeitfähigkeit durch Multitasking und
prioritätsgesteuertes, verdrängendes Scheduling
– Mikrokernel, modularer Aufbau undNachrichten basierte Kommunikation der Prozesse
– Grafische Oberfläche mit dem „Photon microGUI Windowing System“
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Studiengang Software Engineering - Realtime Systems
Der Microkernel
• Modular construction, communication process• Focus on the essentials
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Studiengang Software Engineering - Realtime Systems
Der MikrokernelModularer Aufbau, Prozess-Kommunikation
• Focus on the essentials
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Studiengang Software Engineering - Realtime Systems
Der MikrokernelModularer Aufbau, Prozess-Kommunikation
• Spezialisierung auf das Wesentliche
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Studiengang Software Engineering - Realtime Systems
Der MikrokernelModularer Aufbau, Prozess-Kommunikation
• Spezialisierung auf das Wesentliche
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Studiengang Software Engineering - Realtime Systems
Der MikrokernelModularer Aufbau, Prozess-Kommunikation
• Spezialisierung auf das Wesentliche
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Studiengang Software Engineering - Realtime Systems
Der MikrokernelModularer Aufbau, Prozess-Kommunikation
• Spezialisierung auf das Wesentliche
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Studiengang Software Engineering - Realtime Systems
„Photon microGUI Windowing System“
• Costly surfaces possible
Studiengang Software Engineering - Realtime Systems
Realtime System Test Setup
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Studiengang Software Engineering - Realtime Systems
„Windows NT as a Realtime-System“
At the Technical University of Munich-Windows NT has been used to control a free-floating ball for testing thereal-time capability
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Studiengang Software Engineering - Realtime Systems
Experimental setup
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Studiengang Software Engineering - Realtime Systems
Blockschaltung
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Studiengang Software Engineering - Realtime Systems
Forces on the floating body
FB = F magnet – F weight
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Studiengang Software Engineering - Realtime Systems
The Multimedia-Timers
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Studiengang Software Engineering - Realtime Systems
Histogram halflogharitmic
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Studiengang Software Engineering - Realtime Systems
Result
• 10% Tolerance (1,9 bis 2,1ms)
• meantime 2 ms
• 99% timely call of „Call Back Funktion“
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Studiengang Software Engineering - Realtime Systems
Fazit
• NT disqualified for real real-time applications, since itgives 1% outliers, no safety applications can befulfilled; such as aircraft control during landing.
• Use for robust systems allowed
