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Cleaning Robot
Introduction
Now that we have learned a lot of things about the Sparki, like moving it or using its distance, light and line sensors, gripper, and buzzer, we can try to make a slightly more complex application. So let’s program the Sparki to clean an area where someone has forgotten a few trash receptacles:
What You’ll Need
- A Sparki.
- A convex polygon with its perimeter line printed in black over a white background.
- Some lightweight obstacles, such as cardboard boxes, cylinders, or even balls.
How It Works
The cleaning robot program is easier to be understand if we first think about what the steps are that the robot should actually do. The overall idea is to program the Sparki to do the following steps:- Sparki rotates in its place, searching for an obstacle with its ultrasonic distance sensor (also called ultrasonic range finder).
- Once Sparki finds the obstacle, it advances (moving forward) towards it in order to expel that object outside the perimeter.
- The movement in the forward direction continues until a line sensor (or infrared reflectance sensor) detects the black line. That’s when the robot stops.
- Now, the robot goes backward for a few milliseconds and rotates to the left a bit more to avoid detecting the same object again.
- The program now goes back to step 1.
Coding!
So, let’s start programming one step at a time, in order to better understand the program.
Please remember to check that the batteries are properly connected (and charged!). And as we are going to use the motors here, please check that the On/Off Switch is on. Another important thing to take care of when playing with the robot’s motors is to be careful not to be working over a table. A fall from that table could permanently damage your Sparki.
First, let’s make Sparki rotate until it finds an obstacle:
This can be accomplished using the sparki.moveLeft and sparki.moveRight commands. You can read more about how Sparki moves in the Moving Sparki tutorial. Also, we need to stop the robot (using the sparki.moveStop instruction) when its ultrasonic sensor detects a close object in front of the robot:
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#include <Sparki.h> // include the sparki library void setup() { sparki.servo(SERVO_CENTER); // makes the ultrasonic sensor to point forward } void loop() { while (sparki.ping() > 25) // here we can set different distances to detect objects, //depending on the size of our perimeter { sparki.moveLeft(); // rotates the robot to the left delay(150); // this brief delay is to give enough time to the ultrasonic sensor to work } delay(250); // instead of stopping immediately, rotates a bit more to center the object sparki.moveStop(); // stops all the robot's movements } |
Now we can make the robot move forward in the direction of the detected object, but taking care to not go outside the perimeter: 
Here is the complete code:
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#include <Sparki.h> // include the sparki library void setup() { sparki.servo(SERVO_CENTER); // makes the ultrasonic sensor to point forward } void loop() { while (sparki.ping() > 15) // here we can set different distances to detect objects, //depending on the size of our perimeter { sparki.moveLeft(); // rotates the robot to the left delay(150); // this brief delay is to give enough time to the ultrasonic sensor to work } delay(250); // instead of stopping immediately, rotates a bit more to center the object sparki.moveStop(); // stops all the robot's movements delay(100); //waits a few milliseconds before start moving, just to be nice with the motors while (sparki.lineCenter() > 700) // here we can set different thresholds to detect the line { sparki.moveForward(); // rotates the robot to the left } sparki.moveStop(); // stops all the robot's movements delay(100); //waits a few milliseconds before start moving, just to be nice with the motors sparki.moveBackward(); delay(1000); // the bigger this number is, the bigger the distance that the Sparki goes backward sparki.moveLeft(); // just in case: with this, we prevent Sparki to detect again the same object delay(400); } |
As you can see in the previous code, once the line is detected, the robot stops and goes backward for 1 second (you can change this time to experiment!) and then it moves a bit to the left again, just to avoid detecting the same object that it just expelled a few moments ago.
Extra Activities
- Try to use the right, left and edge infrared reflectance sensors to improve the line detection.
- What about adding line detection to the robot’s rotation also (in the “object detection phase”)? This way, we make sure that it never goes outside the perimeter by error.
- Another possible place to add line detection is when the Sparki is going backward. You can try it!
- If you want to completely change the program, you can also take advantage of the capability of Sparki’s ultrasonic sensor to be moved with the servo. So why not code a new program where you move Sparki’s “head” to find the objects?
Related Lessons
There are other lessons using the edge or line infrared sensors, as well as the ultrasonic rangefinder. If you have not seen them yet, you can take a look at the following activities:Lesson Available for the miniBloq Programming Environment
This lesson is also available for the miniBloq Programming Environment. miniBloq is a graphical programming environment that you can use to easily program your Sparki.
