Introduction to Robotics

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Introduction to Robotics

• Monica LaPoint
• http//www-users.cs.umn.edu/mlapoint
• University of Minnesota Computer Science
• BDPA Youth Conference 2002

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Presentation Objectives

• Overview of Robotics
• Robot components
• Our Demobot's features
• Demobot programming
• Demonstration of obstacle avoidance program
• Next Steps and Wrap up

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OverviewWhat is a robot?
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OverviewWhat is a robot?

• "A reprogrammable, multifunctional manipulator
  designed to move material, parts, tools, or
  specialized devices through various programmed
  motions for the performance of a variety of
  tasks" - Robot Institute of America, 1979

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OverviewWhat is a robot?

• "A reprogrammable, multifunctional manipulator
  designed to move material, parts, tools, or
  specialized devices through various programmed
  motions for the performance of a variety of
  tasks" - Robot Institute of America, 1979
• An automatic device that performs functions
  normally ascribed to humans or a machine in the
  form of a human. - Webster's Dictionary

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Overview What is a robot? (cont'd)

• Robots are a collection of systems that work
  together to accomplish a common function
• Robotics is the study of partially or completely
  autonomous machines (means with little or no
  human interaction)
• Typical systems include controller, actuators,
  sensors and tools for communicating and
  programming

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OverviewHow are robots used?

• Industrial robots do tasks that are hazardous or
  menial

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OverviewHow are robots used?

• Industrial robots do tasks that are hazardous or
  menial
• Exploratory robots explore environments that are
  inhospitable to humans such as space, military
  targets or areas of search and rescue operations

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OverviewHow are robots used?

• Industrial robots do tasks that are hazardous or
  menial
• Exploratory robots explore environments that are
  inhospitable to humans such as space, military
  targets or areas of search and rescue operations
• Assistive robots help handicapped individuals by
  assisting with daily tasks including wheelchair
  navigation and feeding

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Example robots
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Robot componentsController

• Central processing unit (CPU) is the brains of
  the robot
• Includes
• Actual microprocessor chip
• Memory
• Inputs and outputs for motor and sensor control
• Generally understands machine language, much like
  assembly

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Robot componentsActuators and effecters

• Actuators and effecters are physical components
  that act on the environment
• Actuators and effecters create
• Manipulators move objects in the environment
  (robotic arms)
• Locomotors move the robot in the environment
  (wheels and legs)
• Motors and gears drive the manipulators and
  locomotors

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Robot componentsSensors

• Sensors gather and feed information about the
  world back to the CPU to make decisions
• Sensors are usually analog or digital
• Sensors
• Sonar detects obstacles before touching them
• Temperature and light can orient the robot to
  the type of environment or impending failures
• GPS global positioning systems
• Vision camera that feeds images to robot for
  processing

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Robot componentsCommunications/programming tools

• Programs executed by robots must be downloaded
  to memory.

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Robot componentsCommunications/programming tools

• Programs executed by robots must be downloaded
  to memory.
• The tools
• Compile programs from a programming language into
  machine language, a format that CPUs understand
• Communicate instructions to robot

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Robot componentsCommunications/programming tools

• Programs executed by robots must be downloaded
  to memory.
• The tools
• Compile programs from a programming language into
  machine language, a format that CPUs understand
• Communicate instructions to robot
• Often communication takes place via a serial or
  IR connection

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Meet Demobot

• Component Overview
• CPU Handyboard from MIT
• Mechanics and sensors Lego Mindstorms from Lego
• Communication Interactive C from Newton Labs

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Demobot's CPU

• Handyboard developed by MIT
• Contains
• Motorola 68HC11 8-bit micro processor
• 32K of system memory
• Outputs for 4 motors numbered 0 through
• Inputs for analog and digital sensors
• LCD screen
• Popular for competitions and research

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MIT Handyboard
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Demobot's mechanics

• Uses two motors for rear left and right wheel
• Motors receive power via connections to the
  handyboard
• When power is applied to the motor, the motor
  spins forward
• The motor is moved backwards by reversing the
  power
• When power is turned off, the motor stops

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Connecting motors to handyboard
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Demobot's sensors

• Two touch sensors on the front that will tell us
  when we have hit something
• Touch sensors are located in the front left and
  right (Why?)
• Each have digital output, either a 1 or a 0
• Connect to digital ports 7 and 8

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Touch sensors
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Demobot's communicationInteractive C

• Interactive C is an interpreted version of C
• Handyboard languages
• Compiles C and assembly languages
• Java version is available
• Compiles and runs C commands or functions on the
  handyboard immediately
• Compiles and downloads programs to the handyboard
  for later execution

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Demobot programmingGetting Demobot ready for
programs

• The handyboard must be initialized every time it
  is powered up
• Initialization includes
• Setting up memory
• Loading basic routines called libraries

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Interactive C
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Demobot programmingUseful Interactive C functions

• When the power is turned on, if a function named
  main has been downloaded, it will automatically
  run
• Other useful C functions
• start_button() tells us when the start button has
  been pressed
• printf(hello) will print the string hello to
  the LCD screen
• Sleep(float) will pause the program for an
  indicated number of seconds

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Demobot programmingMoving the robot

• How can we start the motor via the handyboard?
• Special Interactive C commands for motors
• fd(motor number) moves motor forward
• bk(motor number) moves motor backward
• off(motor number) turns motor off

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Demobot programmingSample code

• void main()
• printf(Press start\n) lt what do these two
  lines do?
• while (!start_button())
• fd(0) fd(1)
• printf(Forward\n)
• sleep(2.)
• bk(0) bk(1)
• printf(Backwards\n)
• sleep(2.)
• off(0) off(1)
• printf(Stopping\n)

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Demonstration of motor
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Demobot programmingGetting sensor information

• Special Interactive C commands for digital
  sensors
• digital(digital port number) returns integer
• For touch sensors
• 0 means no pressure (switch is open)
• 1 means we have bumped against something (switch
  is closed)

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Demobot programmingSample codes

• void main()
• printf(Press start\n)
• while (!start_button())
• printf(Waiting for a bump\n)
• while (digital(7) 0
• digital(8) 0)
• printf(I've been bumped\n)

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Demonstration of sensors
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Example application Overview

• Goal Translate the sensor information into
  movement commands
• Program
• Move the robot forward until an object is sensed
  in its path
• Once an obstacle has sensed, move backwards and
  turn for 2 seconds to move away from the object
  and continue moving forward
• Stop when the stop button is pressed

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Example application code

• void main()
• printf(Press start\n)
• while (!start_button())
• while (!stop_button())
• if (!stop_button())
• fd(0) fd (1)
• printf(Looking...\n)
• while (digital(7) 0
• digital(8) 0
• !stop_button())
• printf(I hit something...backing up\n)
• bk(0) fd(1)
• sleep(2.)
• fd(0) fd (1)
• / if not stop button /
• / while not stop button /

/ stop button has been pushed /
printf(Stopping\n) off(0) off(1) / end
of main /
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DemonstrationObstacle avoidance program
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Resources for experimentation

• Programming robots via freely available
  simulators
• www.robocup.com - can be used from Windows or
  Unix
• Low and mid cost robotics kits that can get you
  started
• Lego Invention System 2 - www.mindstorms.com(200)
  
• Fischertechnik building system -
  www.techeducation.com
• Handyboard - www.handyboard.com (200-300)
• Robotics Kits - www.acroname.com

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Resources for further study

• Organizations
• www.firstlegoleague.org
• http//www.aaai.org/AITopics/html/robots.html
• http//www.robotmag.com/robotics/t-mini-faq.html
• Books
• Robotic Explorations by Fred G Martin (ISBN
  0-13-089568-7)

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Questions

• Presentation and resources available at
  http//www-users.cs.umn.edu/mlapoint