07-04-2012, 03:13 PM
Real-Time Systems
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. Simple Control System
• Sampling Periods
• Quality of the Control vs. Processing Cost
• Protection of Resources in Integrated Systems
• Multimedia / Real-Time Communication
• Synchronization of Activities:
– Example: Stream Synchronization
• Anomalies in Asynchronous Systems
– Example: Advanced Fighter Technology Integration (AFTI) F16
Quality of Control vs. Processing Cost Example: Open-Loop Temperature Control
• System: Temperature of a unit is controlled by a burner.
• Dynamic equation:
– x difference between unit and ambient temperature, x(0) = 0
– u control input, rate of heat
• Problem: change temperature of unit to xd within time tf;
consume minimum amount of fuel. Allow for a tolerance δ.
Asynchronous Design of Digital Flight Control Systems
‘‘... The asynchronous design of the [AFTI-F16] DFCS introduced a random,
unpredictable characteristic into the system. The system became untestable
in that testing for each of the possible time relationships between the
computers was impossible. This random time relationship was a major
contributor to the flight test anomalies. Adversely affecting testability and
having only postulated benefits, asynchronous operation of the DFCS
demonstrated the need to avoid random, unpredictable, and uncompensated
design characteristics.’’