Flight Simulation Case Study

1
Flight Simulation Case Study

• SE540 Software Architecture
• Mark Ardis, Rochester Institute of Technology
• Fall 2007

2
Acknowledgements

• Some of the material in these slides is taken
  from Software Architecture in Practice, 2nd
  edition by Bass, Clements and Kazman.

3
Outline

• Integrability
• Simulator Problems
• Time
• Structural Model
• Summary

4
Integrability

• Integrability ease with which separately
  developed elements, including those developed by
  third parties, can be made to work together to
  fulfill the softwares requirements.
• Tactics
• keep interfaces small, simple and stable
• loose coupling
• component framework

5
Flight Simulator Problems

• Real-time performance constraints
• Continuous development and modification
• Large size and complexity
• Geographically distributed development

6
More Problems

• Becoming too complicated to manage schedules and
  costs
• Debugging and testing exceeding schedules
• Integration costs exceeded
• Unclear mapping between software structure and
  aircraft structure

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Time

• Periodic - real-time performance
• Event-based - scheduling of interaction events

8
Periodic Time Management

• Used for all components that need to maintain
  real-time performance (e.g., air vehicle)
• Fixed frame rate
• Algorithm
• Set initial time
• Iterate until session complete
• Invoke each process
• Increment simulated time by one frame

9
Event-Based Time Management

• Used for scheduling interaction events
  (instructor station)
• Algorithm
• While there are events in the event queue
• choose event with soonest time
• set simulated time to time of chosen event
• invoke process for chosen event

10
Cartoon of the Day
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Structural Model

• Executive
• Real-time scheduling of subsystems
• Synchronization between processors
• Event management
• Data sharing
• Application
• model the air vehicle

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Executive Modules

• Timeline Synchronizer - schedules and controls
  other executive modules
• Periodic Synchronizer - invokes subsystems to
  perform periodic operations
• Event Handler - invokes aperiodic operations
• Surrogate - hides details of instructor station
  and computation platform from periodic scheduler
  and event handler

13
Application Modules

• Subsystem Controller
• Control their children
• Communicate with other subsystems
• Controller Children
• Communicate only with their parents
• Simulate an individual part
• May
• update
• malfunction
• set parameters

14
Allocating Functionality

• Kinetics - forces on airframe
• Aircraft Systems - common systems for power and
  energy
• Avionics - ancillary support not related to
  kinetics
• Environment

15
n-Square Charts
16
Decomposition
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Tactics

• Performance
• Static scheduling
• Concurrency
• Integrability
• Minimized connections
• Modifiability
• Minimized connections
• Decomposition follows physical structure