Design Methodology for State based Embedded Systems Case Study: Maze Navigator

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Design Methodology for State based Embedded
SystemsCase Study Maze Navigator

• Vivek Subramaniam
• Graduate Student (Masters Program)

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Contents

• Introduction
• Design methodology for state based time triggered
  systems
• Case Study Maze Navigator
• Demo
• Questions

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Introduction
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Behavior Control

• Behavior tasks that process external/internal
  sensory information and issues an action.
• Complex behavior series of alternations of
  simple behaviors.
• Hierarchical Model.
• Reactive robot control architecture.

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Behavior Control API

• Behavior
• boolean takeControl( )
• void action( )
• void suppress( )
• Arbitrator
• public Arbitrator (Behavior behaviors)

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Time triggered Architecture

• Initiated at predetermined instances of
  real-time.
• Event inputs or interrupts are queued and polled
  periodically.
• Relatively easy to validate, test and certify.

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Maze Navigator

• A modification of the Navigator robot as given in
  Brian Bagnalls book Core Lego Mindstorms
  Programming.
• Sensors and Inputs Touch sensor, Light Sensor,
  Timer and two Rotation Sensors.
• Actuators Two motors.
• Due to limitations of system, a simulation was
  developed

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Maze Navigators Behavior Model
Light Sensor
HOME
S
BUMP
Touch Sensor
Motors
True
MOVE
S
S
Point of Suppression
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Design Methodology For State based Time Triggered
systems
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Definition

• Rational Unified Process (RUP) is a framework
  that can be used to describe specific development
  process
• - Grady Booch

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Rational Unified Process
Actors Use-Cases
Class Diagrams Use-Case Realizations
Implementation
Use-Case Model (what)
Actual Code
Analysis/Design Models (how)
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Use-Case Realization
WAKEUP
WAIT
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Use-case realizations with asynchronous waits

• Allocating a thread per scenario with
  Synchronization
• Finite State Machine based Implementation

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RUP for Concurrent Programs using Synchronization
RUP
Component Code
Actors Use-cases
Class Diagram Scenarios
Specify global invariant
Scenarios identify synchronization regions in
which synchronization is required
Complete code
Global invariants (patterns)
Coarse-grained solution
Fine-grained code
Synchronization aspect code development
(A structured approach to develop concurrent
programs in UML)
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RUP for time triggered systems using FSM
Actors Use-Cases
Class Diagrams Use-Case realizations
Revised Class Diagrams Scenarios for threads
Use-Case Model (what)
Analysis/Design Models (how)
Implementation
Original Class Diagram State information
Active Classes
Actual Code
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Event Triggered Systems
Boundary Classes
Other Classes
The flow of control is from the Boundary Classes
to other classes
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Time Triggered System
Boundary Classes
Active Classes
Other Classes
The flow of control is from Active class to
boundary and other classes.
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From this discussion we can see that we have
these four options.
Event Triggered
Finite State Machine
Time Triggered
Allocating thread Per scenario
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Methodology

• Identify the Use Cases
• Describe the Use Case realizations and class
  diagrams
• Identify states and thread scenarios
• Revise Class Diagram and use-case realization
• Form the Finite State Machine
• Translate to code

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Case Study Maze Navigator
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Use Cases for Maze Navigator

• MOVE (true)
• Scan for an unvisited/ least visited cell.
• Determine random No. of steps in the direction of
  picked cell.
• Travel the required No. of steps in that
  direction.
• BUMP (Input from touch sensor)
• Travels back to the last cell location.
• GO HOME (Timer as input)
• Calculate the angle and distance for initial
  point (0,0).
• Rotate for the angle and travel the distance in
  straight line.
• STEER (Inputs from Rotation Sensors)
• Uses rotation sensor to find angle rotated and
  distance traveled.
• Keeps the travel in straight line.

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Use Case Model for Maze Navigator
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Class Diagram
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Use Case Realization Example
Maze Navigator MOVE Behavior
Scan for a unvisited or least visited
cell Calculate random No. of steps to take in
that direction Calculate angle and
distance Start the motors Wait Until required
angle is rotated. Stop motors Update
geometry Start the motors Wait Until required
distance is traveled Stop motors Update geometry
Asynchronous waits
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Revised Use Case Realization Example
States
Wait until input trigger Move Behavior Scan
for unvisited/ least visited cell Calculate
random steps in that cells direction Calculate
angle and distance Start the motors Wait Until
required angle is rotated. Stop motors Update
geometry Start the motors Wait Until required
distance is traveled Stop motors Update geometry
Arbitrator thread
Rotation Sensor thread
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Finite State Machine Method Action Call
actionC
takeControlC
actionB
takeControlB
takeControlA
DONE
Legend
Arbitrator thread
actionA
Rotation sensor thread
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Revised Class Diagram
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Demo
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Acknowledgement

• Dr. Masaaki Mizuno
• Dr. Rodney R. Howell
• Dr. Mitchell L. Nielsen

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Questions ???