1. ROBOTC 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 uses an infrared sensor, not a sonar sensor.

7. ROBOTC Versions Used ROBOTC Version 4.5 Build Date Sept 1, 2015
PowerPoint and all example programs are available at robofest.net under Tech Resources

8. Setting Up The ROBOTC Environment
Opening the source codes files for the workshop will assist in setting up the ROBOTC environment
Once the source files are loaded the EV3 motors and sensors should be assigned

9. Setting Up The ROBOTC Environment
The first step in using ROBOTC is connecting to your EV3 robot
Robot -> LEGO Brick -> Communication Link Setup
Select your EV3
Hit the Close button

10. Setting Up The ROBOTC Environment
The first time you use an EV3 robot with ROBOTC, you need to download the ROBOTC kernel
Robot -> Download EV3 Linux Kernel -> Standard Kernel

11. Setting Up The ROBOTC Environment
Under Robot Menu
Compiler Target
Physical Robot
Platform Type
LEGO Mindstroms EV3
Uncheck Natural Language
Motors and Sensor Setup
Reviewed on the next slide
Firmware Download

12. Motors and Sensors Setup
Select Custom Configuration

13. Motors and Sensors Setup
Set left and right motors

14. Motors and Sensors Setup
Set up sensors

15. Code generation
Once the motors and sensors at set up, ROBOTC will generate code to configure them
We will use this code in all programs we write in this course

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

17. Task 0: Example Solution
Turn on motors forward.
Wait until the edge of the table is detected.
Stop the robot.
Program: findTableEdge.c YouTube:

18. Brick Overview

19. Reading sensors values
One method of monitor the sensor values is to use the ROBOTC debugger window
Download program to your robot
This opens the Debugger and Debugger windows

20. Debugger Windows
ROBOTC offers many debugging options

21. Reading sensors values
We can write a program to display the sensor values on the EV3 LCD screen as well
Program: sensorValues.c YouTube:

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

23. 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

24. 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.
We can use the sensorValues.c program to assist or use the Sensor debugging window.
Color Sensor 1 Color Sensor 2
Off table = ______ (10) On green = ______ (20)
On table = ______ (60) On table = ______ (60)
Color
Sensor
Readings

25. 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.

26. Simple Line Following Algorithm
Set the threshold value.
Loop forever – the robot will not stop.
Based on color senor reading, determine which direction to travel to line follow.
Right side
Program: LineFollowZZ.c YouTube:

27. 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

28. Task 2
Find a putting green

29. 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

30. Find A Putting Green
Let’s modify the previous program to stop when the robot reaches the putting green
Currently the program will line follow until we stop the robot.
Let’s change the outer loop to stop when the green is reached.

31. Find A Putting Green
Here we modify the while loop conditional statement to use the second color sensor to detect when the putting green is reached.
Once putting green is reached, we exit while loop and stop the robot.
Right side
Program: LineFollowZZStop.c YouTube:

32. Task 3
Find the golf ball

33. 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?

34. 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?

35. 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

36. 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.c to stop at the location of the ball
Tools needed
Line following
Measure distance traveled

37. 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

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

39. 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)

40. Measure Distances Here we reset the a motor encoder.
The encoder outputs the rotation of the motor in degrees so we convert the output to rotations.
Code added to wait until the touch sensor is pressed to keep the information visible on the robot screen.
Program: measureDistance.c YouTube:

41. 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

42. 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)

43. Aligning The Robot With The Golf Ball
Here we define some variables.
Loop until the desired distance is traveled.
Compute the distance traveled.
Program: lineFollowDistance.c
YouTube:

44. Task 4
Aim for the hole

45. 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

46. 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
This empty loop with allow the robot to spin until an object is detected by the ultrasonic sensor.
Program: spinSearch.c YouTube:

47. 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

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

49. 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

50. 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.c
YouTube:

51. 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
90° - θ

52. 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

53. 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

54. 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

55. Rotate The Robot To Putt
We can use one block to spin the robot
Loop until the desired distance is traveled.
Program: spin90.c YouTube:

56. Task 5
Putt the golf ball

57. 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

58. Functions
Solving the Robofest Game challenge will typically require a fairly large EV3 program
Very large programs can be difficult to understand, navigate and use
To alleviate this issue, ROBOTC allows the use of functions group and reuse sections of your program

59. Functions
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
Here is an example…

60. Functions Let’s create a function called findEdgeAndTurn
Now can call the function from our main task program

61. 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

62. Little Robots, Big Missions
Questions?