Slide 1

Flight Simulation – Ch 8

A Case Study in an Architecture for “Integrability”

Boeing 747 flight simulator in action – from http://www.bornrich.org/entry/plane-fanatic-builds-30k-boeing-747-flight-simulator-in-his-bedroom/.

Before software - the Wallingford Improved Flight Trainer, 1942. From www.janusmuseum.org/flight/flight.htm .

Slide 2

Coming Up

• Today…– Term paper - Intro– Ch 08 – Flight Simulation – this

• Intro – see for example YouTube vids: http://www.youtube.com/watch?v=JGyJqXJWkuY .

• Thursday– Present outcomes for Project 2– Turn in Thurs night (and HW 3 -

Yikes!)

“How to clean the Gherkin”

Slide 3

Overview

• Structural Model– Minimize modules

• N-Square charts

• Requirements and Qualities– Three roles– Lots of constraints

• Architectural Solution– Treatment of time (real-

time)

Slide 4

Pattern - Structural Model

• Simplicity and similarity of the system’s substructures

• Decoupling of data- and control-passing strategies from computation

• Minimizing module types

• A small number of system-wide coordination strategies

• Transparency of design

Slide 5

Structural Model

Slide 6

Roles

• The Crew– The people being trained

• The Simulator Instructor– Monitors crew performance– Initiates training situations

• The Environment– Atmosphere, threats,

weapons, other aircraft

“Maybe that one’s not one of ours?

Modern simulator from the outside.

Slide 7

Requirements and Qualities

• Real-time performance constraints

• Continuous development and modification– Maintains “verisimilitude” =

realism, as the airplanes changed specs

• Large size and high complexity

• Developed in geographically distributed areas

Slide 8

Problems

• Expensive to debug, test, and modify– Increased cost of integration

• Unclear mapping between software structure and aircraft structure– Many coupling effects to be considered

• E.g., pilot moves the rudder and aileron controls, which move the control surfaces, which affects the aerodynamics and causes the aircraft to turn.

– Performance “fidelity” is # 1 goal

Slide 9

Architectural Solution

Treatment of Time• Periodic time management

– A fixed time quantum based on frame rate– Non-preemptive cycle scheduling –

invokes each process for a fixed time quantum

• Event-based time management– “Interrupt” based– Adds new events into event queue– Does in order of soonest needed

• But all messages from a single source must be done in order!

• Mixed-time systems– The two above systems must interact

Slide 10

Architectural Solution, cntd

Structural Model Architectural Pattern

• Executive– Handles the coordination issues

• Application– Handles computation of the simulation– Functions are implemented by subsystems

Slide 11

Modules

• Executive– Timeline Synchronizer– Periodic Sequencer– Event handler– Surrogate

• Connects air vehicle model to environment model

• Application– Subsystem controller– Controller children

Slide 12

Allocation of Functionalityto controller children

Based on OO modeling of the “objects” of the real airplane:

• Kinetics – the physics

• Aircraft systems – distribution of energy within the airframe

• Avionics – ancillary support

• Environment

Slide 13

Decomposition

• n-Square Charts– What “Partition 2” communicates with…

Partition 1 Inputs

Outputs Partition 2 Outputs

InputsPartition 3

Slide 14

Air Vehicle Model Domain

• An example…

Kinetics Group LoadsVehicle State

VectorVehicle Position

PowerAircraft

Systems GroupPower

Inertial State Loads Avionics GroupOwnship

Emissions

Atmosphere, Terrain, and

Weather

Environment Emitter Data

Environment Group

Slide 15

SummaryHow the architecture achieves…• Performance

– Executive with time budgets, and – Periodic scheduling strategy

• Integrability– All data and control pass through a subsystem controller

as an intermediary– Each partition was restricted in inputs and outputs

• Modifiability– Few base module configurations for the designer and

maintainer to understand

Slide 16

Questions?