1. EV3 Software EV3 Robot Workshop
Instructor:
Assistants:
Lawrence Technological University

2. Course Overview 2015 Robofest competition RoboGolf SPbot introduction
Using the SPbot to solve the RoboGolf challenge

3. 2016 Robofest competition Video overview Key tasks
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

4. 2016 Robofest competition
Please note that putting the golf balls is beyond the scope of this workshop

5. LEGO EV3 robot used – SPbot
Right Motor: C
Touch Sensor
EV3 Computer
Sonar Sensor
Color Sensor 1
Left Motor: B
Color Sensor 2

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

7. EV3 Versions Used
Examples use EV3 Educational Version 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

8. Other EV3 Versions 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

9. Find the edge of the table
Task 0
Find the edge of the table

10. Task 0: Example Solutions
Using wait block
Using loop block

11. Brick Overview

12. Follow the edge of the table
Task 1
Follow the edge of the table

13. 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
Right Edge
Left Edge
Table

14. Follow The Edge Of The 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)
Color
Sensor
Readings

15. Follow The Edge Of The Table
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.

16. Simple Line Following Algorithm
Right side
Program: LineFollowZZ.ev3 YouTube:

17. How to improve our line following algorithm
Zig-zag method can cause a bumpy response
To improve the response, you can use a 3-level line follower (concept shown below)
Off Table
On Table
Off Table
On Table

18. Task 2
Find a putting green

19. 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

20. Find A Putting Green Recall our line following program LineFollowZZ
Let’s modify the program to stop when the robot reaches the putting green
Using this program, the robot will line follow continuously. How can we make the robot stop when it reaches a putting green?

21. Find A Putting Green
Right side
Program: LineFollowZZStop.ev3 YouTube:

22. Task 3
Find the golf ball

23. 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?

24. Find The Golf Ball Example Robot
Follow the edge of the putting green a distance “m”
This will position the robot in line with the golf ball
Robot m
m = 11 cm for the Junior Division. What about the Senior Division?

25. Find The Golf Ball 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
𝑛+𝑚=22 cm
𝑛 𝑚 =𝑋 → 𝑛=𝑚∗𝑋
𝑛+𝑚=𝑚∗𝑋+𝑚=𝑚 𝑋+1 =22 cm
𝑚= 22 cm 𝑋+1

26. Find The Golf Ball One solution Approach Tools needed
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

27. Measure Distances
Determine how far the robot travels moving forward for 2 seconds
Compute distance traveled by measuring the number of rotations of the wheel
Distance

28. Measure Distances Use the wheel geometry PI = 3.14
Circumference = Dia × PI
Diameter = 2 × Radius
Radius
How can use this information?

29. Measure Distances
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)
Program: MeasureDistance.ev3 YouTube:

30. Aligning The Robot With The Golf Ball
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

31. Aligning The Robot With The Golf Ball
Example
Putting green dimensions
m = 11 cm, n = 11 cm
Number of rotations
Distance = (Wheel Diameter) x (PI) x (# Rotations)
Solve for (# Rotations)
Distance
(# Rotations) =
(Wheel Diameter) x (PI)
11 cm
(# Rotations) =
= 0.64 rotations
(5.5 cm) x (PI)

32. Aligning The Robot With The Golf Ball
Line follow a desired distance
Program: LineFollowDistance.ev3 YouTube:

33. Task 4
Aim for the hole

34. 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

35. Method 1: Scan For Hole
Here we are going to have the robot spin until it “sees” the center hole flag with the sonar sensor
Program: SpinSearch.ev3 YouTube:

36. Method 2: Mathematical Approach
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

37. Determine The Rotation Angle
We can use geometry to determine the location of the hole r s t
Robot

38. Determine The Rotation Angle
We can use trigonometry to determine the location of the hole and aim the robot r
si𝑛 𝜃= 𝑟 𝑡 s
𝑐𝑜𝑠 𝜃= 𝑠 𝑡 θ t
Robot
tan 𝜃= 𝑟 𝑠
𝜃=atan 𝑟 𝑠

39. Determine The Rotation Angle
Use an advanced math block to compute the necessary rotation angle
Assume the following
r = 40 cm
s = 30 cm 40
36.87° 30 50
53.13°
Program: TrigMath.ev3 YouTube:

40. Rotate The Robot To Putt
We need to rotate the robot θ degrees to aim the robot at the golf hole
Starting Position
Rotated Position
Robot
Robot θ

41. Rotate The Robot To Putt
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
Robot
Robot
Robot

42. Rotate The Robot To Putt
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 = cm
The circumference of the robot’s wheel
C = PI * D = 3.14 x 5.5 cm = cm
90 degrees is ¼ of the circle. The robot travels
D = ¼ x cm = cm
How rotations to travel cm?
# Rot = Distance / (Wheel Circumference)
# Rot = cm / cm = 0.74

43. Rotate The Robot To Putt
Spinning robot example
Robot width = 16.2 cm
Wheel Diameter = 5.5 cm
Circumference = 17.27cm
Number of rotations
# 𝑅𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛𝑠 = 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑇𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑊ℎ𝑒𝑒𝑙 𝐶𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒
# 𝑅𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛𝑠 = 𝑐𝑚 𝑐𝑚 =0.74 𝑟𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑠

44. Rotate The Robot To Putt
We can use one block to spin the robot
Program: Spin90.ev3 YouTube:

45. Task 5
Putt the golf ball

46. 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

47. My Blocks
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

48. 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

49. My Blocks Creating a My Block Select the section to convert
Go to Tools -> My Block Builder
Enter the block name, description and select icon
Hit Finish 3
This creates a My Block called FindEdge that will be located in the My Blocks Pallet 4

50. Putting It All Together
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

51. Little Robots, Big Missions
Questions?