Design Methodology for State based Embedded Systems Case Study: Robot Controller

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Design Methodology for State based Embedded
SystemsCase Study Robot Controller

• Phaneendra Vanka
• Graduate Student (Masters Program)

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Contents

• Introduction
• Demo
• Design Methodology for Time-Triggered State
  Machine based systems
• Case Study Robot Controller
• Questions

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Introduction
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Behavior Control

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

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LEGO MINDSTORMS

• Robotics Invention System Kit consists of motors,
  touch sensors, light sensors, bricks, gears etc.
• RCX Brick
• - Hitachi H8/3292 series microcontroller.
• - 16 MHz of clock speed.
• - 16Kb ROM.
• - 32 Kb external RAM.

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leJOS

• Java Platform for the RCX Brick.
• leJOS API
• - java.lang, java.util and java.io
• - classes to control motors, sensors,
  buttons, IR communication, navigation etc.

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Behavior Control API

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

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Robot Controller

• A modification of the Navigator robot as given in
  Brian Bagnalls book Core Lego Mindstorms
  Programming.
• Sensors and Inputs Touch sensor, Timer and two
  Rotation Sensors.
• Actuators Three motors.

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Behaviors of Robot Controller

• MOVE (true)
• Travel to a random point
• COMMAND (Input from IR transceiver)
• Travel to a predefined point. If there is an
  obstacle go around that obstacle
• BUMP (Input from touch sensor)
• Travels 20 units in backward direction.
• GO HOME (Timer as input)
• Travel to the starting point
• ARM ROTATE (Timer as input)
• Rotate the arm

.
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Robot Controllers Behavior Model
GO HOME
Timer
S
Touch Sensor
BUMP
S
COMMAND
Command
Motors
Default
MOVE
S
Timer
ARM ROTATE
S
Point of Suppression
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DEMO
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Design Methodology for Time-Triggered State
Machine based systems
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Rational Unified Process
Class Diagrams Use-Case realizations
Actors Use-Cases
Implementation
Use-Case Model (what)
Analysis/Design (how)
Actual code
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Use-Case realizations
WAKEUP
WAIT
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Use-Case realizations with asynchronous waits

• Allocating a thread for each scenario with
  synchronization code
• Finite State Machine based implementation

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Allocating a thread for each scenario
Class Diagrams Use-Case realizations
Actors Use-Cases
Component code
Identify regions in which synchronization is
required
Complete code
Global invariants (patterns)
Coarse-grained solution
Fine-grained code
A Structured Approach to Develop Concurrent
Programs in UML, Masaaki Mizuno, Gurdip Singh,
Mitchell Nielsen
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Finite State Machine based implementation
Revised Class Diagram Scenarios for threads
Actors Use-cases
Class Diagrams Use-case realizations
Original Class Diagram State information
Active Classes
Implementation
Time Triggered
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Event Triggered Systems
Boundary Class
Other Classes
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Time Triggered Systems
Boundary Class
Active Class
Other Classes
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From the above discussion we have the following
combinations

• Time Triggered State Machine based
  implementation
• Event Triggered Thread for each scenario

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Case Study Robot Controller
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Use Cases for Robot Controller

• MOVE (true)
• Pick up a random point (x,y) to reach.
• Calculate the angle and distance to (x,y).
• Rotate for the angle and travel the distance in
  straight line.
• COMMAND (Input from IR transceiver)
• Calculate the angle and distance to (MAXX, MAXY).
• Rotate for the angle and travel the distance in
  straight line.
• BUMP (Input from touch sensor)
• Travel 20 units in backward direction.
• 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.
• ARM ROTATE (Timer as input)
• Rotate the arm in forward direction for 2 seconds
• Rotate the arm in backward direction for 2
  seconds
• 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 Robot Controller
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Class Diagram
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Use Case Realization Example
Robot Controller MOVE Behavior
Wait Until MOVE is triggered Pick a new point
(x, y) 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
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Use Case Realization Example
Robot Controller MOVE Behavior
Asynchronous waits
Wait Until MOVE is triggered Pick a new point
(x, y) 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
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Finite State Machine Method
actions
Behavior Action

• Each behavior is a set of actions.
• After completing one action it goes to the next
  action of the behavior.
• Describe the entire system using finite state
  machine.
• Allocate threads to traverse through the state
  machine.
• Needs only mutual exclusion of shared variables.

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Use Case Realization Example
States
Tippy Senior MOVE Behavior
Wait Until MOVE is triggered Pick a new point
(x, y) 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
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Revised Class Diagram
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Use Case Realization Example
Arbitrator
Tippy Senior MOVE Behavior
Wait Until MOVE is triggered Pick a new point
(x, y) 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
Rotation Sensor Thread
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Arbitrator thread
Action (GO HOME)
takeControl GO HOME
Action (BUMP)
takeControl BUMP
takeControl COMMAND
DONE
takeControl MOVE
Action (COMMAND)
Action (MOVE)
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Rotation Sensor Thread
Action (GO HOME)
takeControl GO HOME
Action (BUMP)
takeControl BUMP
takeControl COMMAND
DONE
takeControl MOVE
Action (COMMAND)
Action (MOVE)
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Acknowledgement

• Dr. Masaaki Mizuno
• Dr. Gurdip Singh
• Dr. Mitchell Nielsen

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Questions ???