EV3 Software EV3 Robot Workshop

EV3 SoftwareEV3 RobotWorkshop

Lawrence Technological University

Instructor:Assistants:

• 2015 Robofest competition RoboGolf

• SPbot introduction

• Using the SPbot to solve the RoboGolf challenge

Course Overview

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• Video overview• https://www.youtube.com/watch?v=bgDL4n1xs3U&feature=youtu.be

• Key tasks– Find the edge of the table– Follow the edge of the table– Find a putting green– Find the golf ball– Aim for the hole

– Mathematics to locate the center hole– Rotate the robot to putt

– Putt the golf ball

2016 Robofest competition

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• Please note that putting the golf balls is beyond the scope of this workshop

2016 Robofest competition

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LEGO EV3 robot used – SPbot

Color Sensor 1

EV3 Computer

Left Motor: B

Right Motor: C Touch Sensor

Sonar Sensor

Color Sensor 2

• Left Motor connects to B• Right Motor connects to C

– If your motors are upside down forward will be backwards in your program

• Color sensor 1 connects to port no. 1• Color sensor 2 connects to port no. 2• Touch sensor connects to port no. 3• Sonar sensor connects to port no. 4

Remember the connections!

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Please note that the retail version of EV3 comes with an infrared sensor, not a sonar sensor.

• Examples use EV3 Educational Version 1.1.1 or Home Edition Version 1.1.1

• EV3 Firmware version: V1.06H

• PowerPoint and all example programs are available at robofest.net under Tech Resources

EV3 Versions Used

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• LEGO offers a home edition of the EV3 software

• It is free to download and use– Limited sensors enabled

• You can download blocks for additional sensors

• Download at

Other EV3 Versions

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http://www.lego.com/en-us/mindstorms/downloads/download-software/

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Task 0

Find the edge of the table

• Using wait block

• Using loop block

Task 0: Example Solutions

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Brick Overview

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Task 1

Follow the edge of the table

• Use the zig-zag method to follow the edge of the table

• Edge following is also referred to as line following

• We need to determine when the robot is on or off the table

Follow The Edge Of The Table

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Rig

ht E

dge

Left

Edge

Table

• Get color sensor values to determine when the robot is on or off the table and putting green. We will use the color sensor in Reflective Light Intensity mode.

• Color Sensor 1 Color Sensor 2– Off table = ______ (10) On green = ______

(20)– On table = ______ (60) On table = ______

(60)

Follow The Edge Of The Table

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ColorSensor

Readings

• Light sensor settings example– Off table = 10– On table = 60– Median threshold = (10+60)/2 = 35

• Two cases– Light sensor reading > 35. On table.– Light sensor reading < 35. Off table.

Follow The Edge Of The Table

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Simple Line Following Algorithm

16Program: LineFollowZZ.ev3 YouTube: https://youtu.be/3UIdveO7fT4

• Zig-zag method can cause a bumpy response• To improve the response, you can use a 3-level

line follower (concept shown below)

How to improve our line following algorithm

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Off Table Off TableOn Table On Table

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Task 2

Find a putting green

• One method of finding a putting green requires two color sensors– Sensor 1 used to follow the edge of the table– Sensor 2 used to locate the putting green

• General idea– Follow the edge of the table until the second color

sensor detects a putting green

Find A Putting Green

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• Recall our line following program LineFollowZZ– Let’s modify the program to stop when the robot

reaches the putting green

Find A Putting Green

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Using this program, the robot will line follow continuously. How can we make the robot stop when it reaches a putting green?

Find A Putting Green

21Program: LineFollowZZStop.ev3 YouTube: https://youtu.be/7uajAXAZjqo

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Task 3

Find the golf ball

• General idea– Let’s assume we located the putting green and we

know where the golf ball is on the green relative to the edge of the green

– How can we begin to position our robot to putt?

Find The Golf Ball

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• Example

Find The Golf Ball

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Robotm

• Follow the edge of the putting green a distance “m”

• This will position the robot in line with the golf ball

m = 11 cm for the Junior Division. What about the Senior Division?

• How to find “m” given n/m– From the diagram of the putting green we have

– Let’s assume that n/m = X (X is known)– Now we can solve for m

Find The Golf Ball

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𝑛+𝑚=22cm

𝑛𝑚=𝑋→𝑛=𝑚∗ 𝑋

𝑛+𝑚=𝑚∗𝑋+𝑚=𝑚 ( 𝑋+1 )=22cm

𝑚=22cm(𝑋+1 )

• One solution– Follow the edge of the putting green until we

reach the position of the ball• Approach

– Let’s modify LineFollowZZStop.ev3 to stop at the location of the ball

• Tools needed– Line following– Measure distance traveled

Find The Golf Ball

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• Determine how far the robot travels moving forward for 2 seconds

Measure Distances

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Distance

Compute distance traveled by measuring the number of rotations of the wheel

• Use the wheel geometry

Measure Distances

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PI = 3.14

Circ

umfe

renc

e =

Dia

× PI

Radius

Diamet

er =

2 ×

Rad

iusHow can use this information?

• For each rotation of the wheel, the robot will travel (Wheel Diameter) x (PI)

• Distance = (Wheel Diameter) x (PI) x (# Rotations)• Distance = (5.5 cm) x (PI) x (# Rotations)• Distance = (17.28 cm) x (# Rotations)

Measure Distances

29Program: MeasureDistance.ev3 YouTube: https://youtu.be/g-8ocEIlxPQ

• Proposed method:– Compute the distance to travel along the edge of

the putting green– Compute the number of rotations required to

travel that distance– Find the edge of the putting green– Reset motor rotation sensor– Follow the edge of the putting green– Stop the robot when the desired number of

rotations is reached

Aligning The Robot With The Golf Ball

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• Example– Putting green dimensions

• m = 11 cm, n = 11 cm– Number of rotations

• Distance = (Wheel Diameter) x (PI) x (# Rotations)• Solve for (# Rotations)

Aligning The Robot With The Golf Ball

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(# Rotations) = (Wheel Diameter) x (PI)

Distance

(# Rotations) = (5.5 cm) x (PI)

11 cm= 0.64 rotations

• Line follow a desired distance

Aligning The Robot With The Golf Ball

32Program: LineFollowDistance.ev3 YouTube: https://youtu.be/BfzXMNbnC_k

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Task 4

Aim for the hole

• We will review a few methods to aim for the hole

• Method 1: Search for the flag pole– Scan using the sonar senor

• Method 2: Compute the location of the hole– Mathematically determine the location of the hole

• Step 1– Determine the angle we must rotate to aim the robot towards the golf hole

• Step 2– Rotate the robot the determined amount

• Method 3: Determine the location using trial and error– Here we find the hole by rotating the robot different amounts in an attempt to

find the correct orientation

Aim for the hole

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• Here we are going to have the robot spin until it “sees” the center hole flag with the sonar sensor

Method 1: Scan For Hole

35Program: SpinSearch.ev3 YouTube: https://youtu.be/GQg6tLZamsE

• Using this approach we can calculate how far to rotate the robot to face the center hole

• We complete this in two steps– Step 1

• Determine the angle we must rotate to aim the robot towards the golf hole

– Step 2• Rotate the robot the determined amount

Method 2: Mathematical Approach

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• We can use geometry to determine the location of the hole

Determine The Rotation Angle

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r

st

Robot

• We can use trigonometry to determine the location of the hole and aim the robot

Determine The Rotation Angle

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tan𝜃=𝑟𝑠

si𝑛𝜃=𝑟𝑡

𝑐𝑜𝑠𝜃=𝑠𝑡

𝜃=a tan( 𝑟𝑠 )

r

stθ

Robot

• Use an advanced math block to compute the necessary rotation angle– Assume the following

• r = 40 cm• s = 30 cm

Determine The Rotation Angle

39Program: TrigMath.ev3 YouTube: https://youtu.be/DVFz0_Sf8tg

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30 5053.13°

36.87°

• We need to rotate the robot θ degrees to aim the robot at the golf hole

Rotate The Robot To Putt

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RobotRobot

Starting Position Rotated Position

θ

• We will use the spin feature to turn the robot θ degrees

• When the robot spins, the wheel path is a circle centered between the wheels

• The diameter is the track width of the robot

Rotate The Robot To Putt

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Robo

t

Robo

t

Robot

• For an example, let’s spin the robot 90 deg– Robot track width = 16.2 cm– The circumference of the robot’s path

• C = PI * D = 3.14 x 16.2 cm = 50.87 cm– The circumference of the robot’s wheel

• C = PI * D = 3.14 x 5.5 cm = 17.27 cm

• 90 degrees is ¼ of the circle. The robot travels– D = ¼ x 50.87 cm = 12.72 cm

• How rotations to travel 12.72 cm?– # Rot = Distance / (Wheel Circumference)– # Rot = 12.72 cm / 17.27 cm = 0.74

Rotate The Robot To Putt

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• Spinning robot example– Robot width = 16.2 cm– Wheel Diameter = 5.5 cm

• Circumference = 17.27cm

• Number of rotations

Rotate The Robot To Putt

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(¿𝑅𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛𝑠 )=12.72𝑐𝑚17.27𝑐𝑚=0.74 𝑟𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑠

(¿𝑅𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛𝑠 )= 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒𝑇𝑟𝑎𝑣𝑒𝑙𝑒𝑑h𝑊 𝑒𝑒𝑙𝐶𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒

• We can use one block to spin the robot

Rotate The Robot To Putt

44Program: Spin90.ev3 YouTube: https://youtu.be/mIBylTRqA9Y

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Task 5

Putt the golf ball

• Again, this task is beyond the scope of this course

• However, your robot should be in position to putt the ball in the center hole

• Remember, you can only hit the golf ball once and only with the wooden block putter

Putt The Golf Ball

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• Solving the Robofest Game challenge will typically require a fairly large EV3 program (around 100 blocks is not unreasonable)

• Very large programs can be difficult to understand, navigate and use

• To alleviate this issue, the EV3 software has a My Block Builder to create custom blocks that can replace sections of your program

My Blocks

• For example, let’s assume you have a section code that completes the following:– Move forward until the edge of the table is found with

color sensor 1, then stop– After stopping, rotate the robot 90 degrees

• The code may look like this

• My blocks will allow us to convert this to a single block

My Blocks

• Creating a My Block1. Select the section to convert2. Go to Tools -> My Block Builder3. Enter the block name, description and select icon4. Hit Finish

My Blocks

This creates a My Block called FindEdge that will be located in the My Blocks Pallet

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• In this course we learned how to– Find the edge of the table– Follow the edge of the table– Find a putting green– Find the golf ball– Aim for the hole– Putt the golf ball

Putting It All Together

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chung@LTU.edu

Little Robots, Big Missions

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Questions?