1. NET 424: REAL-TIME SYSTEMS (Practical Part)
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Tutorial 3 : on lecture 2 & lecture 3

2. Soft real time system application
your iPhone or your Andriod phone is an electronic device whose goal is to operate in real time. When you browse for an appointment or phone number, you expect the device to respond to your finger gestures in a timely manner. However, if a particular gesture requires several seconds to respond rather than the fraction of a second normally required, nothing catastrophic will occur. You may be a little annoyed but you’ll assume something important is going on behind the scenes.  Perhaps you’ll shut down some apps that might be stealing computational power in the background.  This type of device is an example of a “soft real-time” embedded device. The term “soft” indicates that there is some flexibility in the real-time requirement.
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3. hard real-time application
The fly-by-wire Flight Control Computer (FCC) uses electronic signals to measure the pilot control motions and to control the aircraft’s control surfaces. The FCC must transmit the pilot’s intentions at a predetermined frequency. If the fly-by-wire system cannot communicate information with sufficient determinism, the aircraft can become unstable — resulting in a crash.
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4. Control systems Control system:
A control system consists of subsystems and process assembled for the purpose of controlling the output of the process.
Controlling internal inputs to have desired output.
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5. Classification Man made control system. Biological control system.
Combinational (Man made + Biological) control system.
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6. Classification (Cont.)
Classification by nature:
Linear and non linear.
Time variant and time invariant.
Open loop and closed loop.
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7. Open loop Controlling action independent of the output of system.
No feedback.
Two components:
1)Controller.
2)System.
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8. Example – open loop On/off switch
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9. Open loop Advantages: Disadvantages: Simple to design.
Less maintenance required.
Disadvantages:
Inaccurate.
Internal noise and parameter variation affects system performance.
Not reliable.
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10. Closed loop system Feedback id present. Consists of 1) controller.
3)Feedback system.
4)Error detector or comparator.
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11. Example- closed loop system
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12. Closed loop system Advantages: Disadvantages: Accurate and reliable.
Faster.
Reduced effect of parameter variation.
Disadvantages:
Complicated to design.
Costly.
Can become unstable under certain condition.
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13. The End
Any Questions ?
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