Chapter 10. A Quadcopter

You've built robots that can roll, walk, sail, and even go under the water. In this chapter, you'll build a robot that can fly. This project will guide you through the process of creating your own quadcopter based on the BeagleBone Black.

In this chapter, we will learn the following:

• Building a quadcopter

• Connecting the BeagleBone Black to the quadcopter

• Controlling the quadcopter using the BeagleBone Black

Basics of quadcopter flight

Now you'll build robots that can fly by relying on the BeagleBone Black to control their flight. There are several possible ways to incorporate the BeagleBone Black into a flying robotic project; in this case, a quadcopter.

Quadcopters are unique flying platforms that have become popular in the last few years. They are flying platforms that utilize the same vertical lift concept as helicopters. However, they employ not one but four motor/propeller combinations to provide an enhanced level of stability. Here is an image of such a platform:

The quadcopter has two sets of counter-rotating propellers, which simply means that two of the propellers rotate one way and the other two rotate the other way to provide thrust in the same direction. This provides a platform that is inherently stable. By controlling the thrust, all the four motors allow you to change pitch, roll, and yaw the device. Here is a diagram that might be helpful:

As you can see, controlling the relative...

Building the quadcopter

The first thing you'll need is the quadcopter itself. The most important component of the quadcopter is the flight controller board. There are several choices that can work, but this example is based on the Hobby King KK2.1.5 flight control board. Here is an image of the board:

The flight control board takes its flight inputs via a set of input signals that would normally come from an RC receiver to control the quadcopter, and then sends out control signals to the four motor controllers. You'll want a flight controller as it has built-in flight sensors, so it can handle the feedback control for the motors. The inputs from the BeagleBone Black will come in as electric commands to turn, bank, go forward, or increase/decrease the motor speed.

You can buy either an assembled quadcopter that uses the HobbyKing 2.1.5 board from HobbyKing at www.hobbyking.com, or you can buy the parts and assemble your own.

Note

If you'd like to assemble your own quadcopter, then there are a...

Connecting the BeagleBone Black to the quadcopter

A nice thing about the KK 2.1.5 flight controller is that it has built-in flight sensors, so it can handle the feedback control for the motors. The other feature is that it has a screen and input buttons that will allow you to control the board manually during setup.

The control inputs come in as electric commands to turn, bank, go forward, or increase the altitude. Normally, these would come from your RC radio receiver. For this project, you'll disconnect these signals and insert the BeagleBone Black and the maestro servo controller to send the proper control signals. Here is a diagram that shows how you have to connect the BeagleBone Black, the servo controller, and the flight controller:

The following is a close-up image of the connections between the servo controller and the flight controller board:

Note that you need to use the foam that came with the flight controller as this will dampen the vibrations inherent in the system so that the...

Controlling the quadcopter using the BeagleBone Black

Now you will use the BeagleBone Black to send commands to the servo controller, which will in turn control the flight controller board. To start this procedure, you'll need to add the RC battery to the quadcopter. This will power up the flight controller board. Connecting your battery should result in the following power-up screen on the flight controller board:

For this procedure, you'll start as if you are setting up a new flight controller board. If you have already set up the flight controller board with your radio, you will be able to skip down to step 7.

Here are the steps to set up your flight controller board to work with the BeagleBone Black:

1. To start with, you'll need to set up the board to control your four-motor quadcopter. To do this, press the MENU key, press the DOWN button, and then the Load Motor Layout configuration button, as shown here:

   

2. Now you'll select the QuadroCopter + mode option, as shown in the following image:

   

3. After...

Summary

Now you have a quadcopter that can be controlled by the BeagleBone Black. However, your BeagleBone Black is still controlled via wired connection. In the next chapter, you'll use some of the techniques that you learned in the previous chapters to connect with the BeagleBone Black wirelessly and fly your quadcopter. Finally, you'll use a webcam to allow your BeagleBone Black to know about its world so that it can level and fly itself. You'll also use your knowledge of path planning and a GPS to fly the quadcopter autonomously.