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Robofest 2007 Introduction to RoboLab

Workshop

Feb. 3, 2007

Maurice Tedderwww.Robofest.net

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Student Assistant

• Emily Trudell and Joe Long• Sat. 9AM-12PM

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Agenda• Intro to RCX• Intro to RoboLab • 9 Class Missions (somewhat related

to the Robofest Game 2007)• Programming Tips

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LEGO MindStorms 101

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LEGO MindStorms® Overview – Robot Command Explorer (RCX/Brick)

Hitachi H8 16MHz 8-bit microcontroller with 32K ext. Ram

16K ROM contains power up driver

16K of firmware can be downloaded to extend the on-chip driver

User programs are downloaded to the RCX as byte code in 6K region of memory

Firmware executes and interprets the byte code of programs when instructed

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LEGO MindStorms® Overview – Robot Command Explorer (RCX/Brick)Infra-red (IR) Receiver Is a sensor that accepts the

program being transmitted from the IR tower. Also transmits data.

Sensor Input Ports Input ports 1, 2, & 3 are used to attach sensors to the RCX (0V/0 – 5V/1024 A/D)

View Button Used to obtain feedback from the input and output ports

On-Off Button Manually turn the RCX on and off

Motor (output) Ports Use output ports A-C to connect any combination of motors

LCD Display Display different values and information regarding the RCX and programs

AC/DC Power Input The RCX can be powered by plugging into a 9 Volt adapter (not for recharging batteries)

Program Button Used to switch between programs 1-5

Run Button Press the Run button to activate and run your current program

Speaker (not shown) Internal speaker indicates RCX status and acts as a programmable sound output

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What Is RoboLab?

• A ‘Graphical’ programming language For the RCX based on LabVIEW

• In 1997, LabView was used for Sojourner project

• By designing a flow chart with given icons the programmer can program the RCX

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Writing a new program

Click on the Programmer button.You should then see the Inventor login screen. Double click Inventor 4 to get full RoboLab environment.

Introduction to RoboLab – Programming Environment

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ROBOLAB Environment

• Set up your screen in Inventor 4 so that it looks like the screen to the right.

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ROBOLAB Environment

• There are two major pallets that contain most of the icons and commands you need to build a program.

• If you cannot see these pallets, you can find them under the Window -> Show drop down list.

Tools

Functions

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RoboLab Workspace

Functions Palette – Contains

Icons for all possible

RCX program

commands. Icons vary with Level

Tools Palette – Contains Icons for building a

program diagram in the RoboLab

workspace

Context Help –

When this window is

open it displays

Help information about the Function

Icon under the mouse

cursor

Example Program –

All programs begin with a Green light

and end with a Red light

Icon

Search – Click the Search tab to find a Function

Icon in the Functions palette

Menus

Sub Menu Icons – Icons with the right side black dot have sub

menuIcons

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Tools Palette

Operate Value tool: Change values in the Workspace window

Wire Tool: connect icons in your program from start to

finish

Set/Clear Breakpoint: allows you to suspend the execution of your program

Set Color Tool: allows you to set the colors of objects in the Panel and Diagram windows

Scroll Window Tool: move around in the Title or Workspace windows

Arrow Tool: move, delete, or place icons in workspace window

Automatic Tool Selection: Automatically senses correct

tool to use

Get Color Tool: allows you to copy a color from an image and use it as part of the color palette

Probe Data: allows you to check the program for values

Object Popup Tool: modify settings for

items in the Workspace window

Edit Text Tool: edit or insert text boxes

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RoboLab Programming Elements• Forks – equivalent to if/then selection

structures• Task – run multiple task simultaneously (8

max.)• Wait states – program execution will be

halted until the wait state condition is satisfied

• Loops – to create repetition structures in a program

• Subroutines – a segment of code that can be called repeatedly from another code segment (8 max./program slot)

• Events – jumps to the specific section of code when the specified event occurs

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RoboLab Capabilities I

Read Analog input values Output PWM on the output ports Subroutines Multitasking Event monitoring Multimedia Image/sound processing and

capture Access all RCX Brick input/output

interfaces (buttons, LCD screen, etc.) Music and sound functions

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RoboLab Capabilities II

Data logging (2000 pts. @ 100Hz) and processing functions using G-Code (can compute basic statistics to derivatives and integrals)

Basic Logic and Math functions Variables (47 total, 22 user variables) IR Communication functions Direct program control functions Internet functions User defined libraries LASM functions (LEGO assembly language) Control lab interface functions

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Pros to Using RoboLab

• Easy to see control structure• Visual interface is simple• Exactly like LabVIEW• Data gathering and visualization

(investigator)

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Cons to Using RoboLab

• Spaghetti code• Hard to wire icons…• No edge triggering supported

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For More Information

• LEGO’s Pagewww.lego.com/dacta/robolab

• National Instruments Pagewww.ni.com/robolab

• Tufts Universitywww.ceeo.tufts.edu/graphics/robolab

• www.lego.com/education/mindstorms/images/eng/downloads/compare.doc

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What is a computer program?

A list of instructions created by a computer programmer (you) that tell a computer what to do next

Your job as a computer programmer is to: Decide how to get from point A

to point B using a bag of tricks (instructions)

For the LEGO Robot, instructions = Picture Icons connected together to form a program

•A (what I want the program to do)

•B(program doing what I want it to do)

LEGO RoboLab Function Icon

Palette

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An Introduction to Structured Programming(or How to get from point A to point B) Structured programming philosophy states that all

programs can written using only three single entry/single exit control structures

1. Sequence structure: is built into RoboLab and means that statements are executed sequentially one after another as along the chain of connected icons

2. Selection structure: chooses between alternative courses of action (makes yes or no decisions)

3. Repetition structure: tells which actions are to be repeated while some condition is true

Programs are built in structured programming by stacking and/or nesting as many control structure building blocks as needed to solve the problem

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RoboLab Control Structures

SequenceLoop/Repetition : Decision: Fork

Subroutines:Multitasking:

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Ex 1: Go forward 2 seconds and come back by reversing motors

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Making Turns

• Turn left:

• Spin left: (point turn)

• Face left:Left wheel

Left wheel

Right wheel

Right wheel

Left wheel Right wheel

stop

stop

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Ex 2: Go forward 1.5 seconds and come back by spinning left

• Spinning 180 degrees?• Is it accurate?

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Tips• How to insert icons?• How delete icons?• How to save programs?• How to use the Icon search feature?• Cover the tower and RCX when

downloading, if more than one robot in a room!

• Use Meaningful file names• Add Comments using “A: edit text”

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Sensors•Light•Touch• Rotation • Temperature• Timer – Internal sensor• RCX buttons

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Light Sensor

• Percent mode 5% - lowest dark 100% - very bright

• Reflected light mode: shines a red light

• Use View Button

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Light Sensor Readings

Source: HighTechKids.org

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Attach a Light Sensor

• Facing down• Gap: around 1 cm (What will be the

problem if less than 1 cm to solve the Miner Rescue problem?)

• Port No. 1

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Ex 3. Go straight until the edge of the table is detected. Then stop the robot

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Stop when it sees the black line on the Miner Rescue field• Measure and record the following

values White shelf Black line Foil Outside Edge Start of the ramp from the miner field

and the home base: why? The big gap!

• Suggested to lower the power level move down slowly

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The gap between the Light sensor and the floor!!!• Both Reflected and Ambient light

values are affected by the distance between the sensor and the floor!

• The light sensor value is in inverse proportion to the gap

Lightsensor

Lightsensor

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Stop when it sees the black line on the Miner Rescue field

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Ex 4. Stop when it sees the 2nd black line on the Miner Rescue field

What went wrong?

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How about stopping at the 4th line?• Loop (Repeat)

Block

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Touch Sensor

• If released (not pressed): 0• If pressed: 1• Is it very sensitive?

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Attach a Touch Sensor

• Port No. 2

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Ex. 5 Loop until a touch sensor is pressed

Display seconds until touch sensor is pressed.

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Line following - Zigzag methods

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Ex 6. Follow the black line until a touch sensor is pressed

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Ex 7. Follow the line until it detects the foil

• Need max power to climb

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Ex 8. Follow the line until it climbs back to the home base

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Ex 9. Follow the line until it climbs back to the home base – Use Subroutines

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Not covered advanced topics

• Variables

• Multiple tasks & Synchronization of multiple tasks

• …

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Tips for Robofest 2007 Game

•Line following may be needed for RCX

• Light sensor needed for detecting balls in the tunnel or edge

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Tips for RoboSumo

• Light Sensor to detect the ring edge

• Touch sensor to detect the opponent

• Theories in physics