Android Controlled, Path Following Vehicle

This Instructable will guide you through the building of Alice, the path following vehicle.

It consists of an Android application and an inexpensive miniature vehicle, that you can build using common parts found online or at your local electronics shop.

Alice, was built during the DIT524 course in the University of Gothenburg by the first year students Kai Salmon, Martina Freiholtz, Tobias Lindell, Rachele Mello and Linhang Nie. I was supervising them and provided them with the hardware platform and two Arduino libraries ([1], [2]), which enabled them to easily work with it.

They built a system, that allows the user to draw a path directly on the phone's screen and then the vehicle to follow it. Their product, is a proof of concept, which could be utilized to dynamically draw a path over a predetermined area, in a user friendly way, for a robot or a vehicle to follow the sketched route and possibly execute some tasks. Some real life cases where this could be used, include a factory floor or a warehouse, where a robot should move to a specific location, pick something and move it to another spot. Alternatively, another use case could involve the system in an emergency situation, where a robot would be tasked to visit specific locations and deliver supplies or provide assistance.

Before moving on to the specifics, check this demo video out.

Step 1: Building the Car - Hardware

In order to build, or rather assemble, the car you will need the following components:

  1. Car chassis (you can find the ones displayed here, on Ebay or AliExpress, by searching for "smart robot car")
  2. Two (or four) DC motors
  3. Wheels (for easiness, buy a kit that contains all the above)
  4. Arduino Mega
  5. L293D motor shield (used to be made by Adafruit, but now you can find them sold by Chinese resellers)
  6. L3G4200D Gyroscope (used in order to rotate the car at specific degrees)
  7. Speed encoders (this or this will suit the car kit I suggested above)
  8. HC-SR04 ultrasonic sensor (used in order to detect obstacles in the front of the vehicle)
  9. HC-06 Bluetooth module (used to communicate with the Android phone)
  10. Battery pack (we use a 12 Volt one, with 8 AA batteries)

Of course you do not have to use these specific components. I am just mentioning the ones found on "Alice" and with which, the software referenced here should work mostly out of the box. The cost of "Alice" is approximately 40$ if everything is bought from China.

Refer to the schema in order to understand how the various connections are made.

In brief, the motors get attached to the motor shield as does the battery pack. The gyroscope gets connected to the I2C bus and don't forget to connect the SD0 pin to the 5V. Connect the wheel encoder to pin 19 (or any other pin that supports external interrupt) and the Bluetooth module to a Serial port (RX to TX and TX to RX). Finally, connect the ultrasonic sensor to any two input pins.

Step 2: Building the Car - Software - Arduino

The Arduino Mega, found on the path following vehicle, runs the Arduino sketch found here. After the user draws a path, it receives all the necessary commands and stores them in a custom made buffer, where each command is executed sequentially.

If an obstacle is found, then the vehicle stops and sends back to the Android phone, the index of the command that was being executed, while the obstacle was met. Therefore, the application can determine and visualize, where on the path the obstacle was encountered.

In order to run this sketch, you have to download and install two Arduino libraries. The Smartcar Core and the Smartcar Sensors. If you do not know how to do this, check this out.
Also, take a look in the Wikis of the two libraries. You will find extensive information regarding their usage and especially how to apply them in different settings, i.e. if you are not using exactly the same components as we did.

Ultimately, you should be able to make the car rotate clockwise by 90 degrees, by typing alice.rotateClockwise(90) or instruct it to travel 100 centimeters to the front with alice.goForward(100).

Step 3: Building the Car - Software - Android

The Android application used to draw the path and send the instructions to the vehicle, via Bluetooth, can be found here.

You can download the already built APK that I have attached below. However since you generally should NOT install APK's from unknown sources over the internet, I strongly advise you to download the source, review it, then build it yourselves and install it.

You can do that by cloning the repository, or just downloading it as a .zip file. Then, import it in Android Studio or whatever IDE you are using. The application has just one dependency, the appcompat library, which you might have if you are already working with Android. Don't worry about this anyway, if you are missing it, you can easily install it through the IDE after being notified of its absence.

The Android application is composed of three screens.

  1. The path drawer, which is the application's backbone, where the user is able to draw the path on the screen, connect to the vehicle, send the instructions, drive it manually or access the settings menu. You will get notified if the vehicle has met an obstacle, so you can either change the course, order it to continue if the "threat" is not valid or even drive it manually to avoid the obstruction.
  2. The settings menu, where the user can define various parameters such as the sensitivity of how the path is drawn or the size of the actual area where the robot should drive. Moreover, you can choose to add a picture to draw the path over. In this case, this picture could be the blueprints of a floor, or a map of an area in which you want to navigate your vehicle.
  3. The manual control window, where the user can steer the car manually, using a joystick.

Step 4: That's About It!

It wasn't so hard, was it? Now all you have to do is try it out and why not, try to improve things! I believe this concept has the potential to be used in a non hobbyist environment, in order to improve or even save lives.

I did not provide extensive details on how to build the vehicle, since you should not feel confined in using the exact one we did. If you have any questions regarding the assembly or programming, do not hesitate to leave a comment below.

3 People Made This Project!


  • Faux-Real Contest

    Faux-Real Contest
  • PCB Contest

    PCB Contest
  • Epilog X Contest

    Epilog X Contest

52 Discussions

Mahedi HasanJ

2 years ago

what is the purpose speed encoder here? can anyone please explain it to me? I am having trouble with this one.

4 replies
Mahedi HasanJDimitris Platis

Reply 2 years ago

Can I complete this project without speed
In my area it's not available and I am beginner also. Can you
tell me what I can do instead using speed encoder please?

Thanks in Advance

Dimitris PlatisMahedi HasanJ

Reply 2 years ago

Hmmm, as the speed encoder measures distances it is crucial for the general functionality of the vehicle.

A work around would be to experimentally determine how much time the car needs to move X centimeters. Therefore when the car needs to move 50 centimeters, instead of using the encoder to get the travelled distance you would move the car for a specified amount of time.


7 weeks ago

hello sir,
This project is very helpful but the range of bluetooth is been problem.Can i use esp8266 or HC 12 Bluetooth module

2 replies

Question 10 months ago on Step 3

Hi i need a report but there is no region of my country how can i get a report or PDF

1 answer

2 years ago

I made it, but I can't figure out why the APK isn't working. I try the download on this page, I try as well via android studio. If the app is installed on the phone and I press on "connect", stopt the app immedialtly.

5 replies
SimonsmachineDimitris Platis

Reply 2 years ago

Thanks to reply. I really like your project.
I fixed the Bluetooth problem (wrong password) :\
Now it's working: the app connect to the car but when I press on "send" the car go straight on en never stop. I need to reset the car to stop it. It doesn't follow the path and the manual mode does nothing.


Reply 1 year ago

i am facing the same problem you mention in the above unfortualty stop.

how do you solve it?

Dimitris PlatisSimonsmachine

Reply 2 years ago

Many things could be wrong, it is really hard to tell. The two most probable reasons I can think of are:
1) The car does not receive the appropriate commands
2) The car cannot execute the "going forward until specific distance command" appropriately.

To see if it's (1) try printing out through serial the various commands that the car receives and to see if it's (2), try making the car just to move forward for a specific distance.

h samy

1 year ago

hi Dimitris

i want to know if this app can be made on the MIT app inventor or not ?

3 replies
Dimitris Platish samy

Reply 1 year ago

I haven't used the MIT App Inventor a lot, but unless there is a way to "draw" stuff on the screen and be able to process the drawn path, no.

h samyDimitris Platis

Reply 1 year ago

there is a way to draw and what do you mean by process ??

h samyh samy

Reply 1 year ago

i can send the coordinates of x and y on screen