Arduino components and a basic introduction to flight.

Getting the arduino components was the next step. Before we get into what components are needed, we need to discuss how quadcopters actually fly.

Quadcopters have four rotors (quad=4, copter=flying thingy). Two of the rotors rotate clockwise, and the other two rotate counterclockwise (we'll need this later). The quadcopter is controlled by changing the speed of one or more of the motors.

There are four basic ways that a quadcopter can be controlled.

Throttle:

Throttle is exactly like your car's gas pedal. The more throttle, the faster all four motors will turn, and the higher the quadcopter will go. Think throttle = elevation.

Pitch:

Pitch is the rotation front to rear. If you are hovering at a specific height, and want to go forward, you pitch forward. This decreases the front motors speed and increases the rear speed. This causes a moment about the center of mass. Now, the thrust vector is not pointing straight down, bu rather at an angle. The quadcopter will move forward.

Roll:

Roll is like pitch, but in the left, right direction. Think of a plane. When a plane rolls left, the left wing drops down. The same is true of a quadcopter, but the left propeller dips.

Yaw:

Yaw is the rotation about the relative z-axis. A merry-go-round spinning is an example of yaw. With quadcopter's, the yaw comes from decreasing the spin of either the clockwise or counteclockwise propellers.

Image showing pitch, roll, and yaw. Image from Purdue.

The angle and magnitude of the thrust vector from the propellers determine the direction and how fast the quadcopter flys. Thrust is a force (kg*m/s^2). If we assume that the mass of the quadcopter does not change throughout flight, we can treat it as a constant. Therefore, the only thing that can change the attitude of the quadcopter is the acceleration vector. If you know the angle of acceleration, you know the angle of thrust. It is for this reason, I am using a three-axis acclerometer. I simply take the acceleration in the x, y, and z direction, and use trig to find the angle of acceleration. In a perfect environment (no wind and at sea level), the quadcopter will hover when the pitch and roll angle are zero, and the acceleration is equal to 9.8m/s^2.

But what about the yaw? Right now, I am using a gyroscope to determine how fast the quadcopter is rotating about the z-axis. If the yaw is zero, the quadcotper is not rotating at all. The problem with this is that you do not know the angle with respect to an origin. It is possible to use a magnometer to get your angle, however I have not done this because I do not have one at the current time.

The sensors I am using are a MPU-6050 6-axis accelerometer/gyro, a sonar for altitude, and 4 IR distance sensors.

Quadcopter Hardware

So I started my project by researching and buying a quadcopter. hobbyking has the best selection of quadcopters and quadcopter parts. They ship from Japan, so be patient when ordering stuff as it has to go through customs. I chose to go with the Turnigy Talon II frame, with 12" propellers, a KK controller board, and four motors. I would suggest you search around their website a lot before buying anything.

Here are some things to keep in mind:

1) How much weight are you planning on trying to lift? The weight you need to lift will determine how big of motors you need. Do an estimated weight and add 20-40% to that value. That way, you will be able to not only lift the weight, but you will have some leeway in your acceleration.

2) Will the battery, electronic speed controls, and motors all work with each other? Each motor has is designed for a specific battery type and voltage. Make sure that they all work together and the amperage of the esc is correct.

3) Make sure you have the correct (and necessary) wires to connect all of the components.

Introduction

Hey everyone.

My name is Evan Kaiser. I am a student at Rensselaer Polytechnic Institute studying Aerospace Engineering. In January, I decided to take the semester off from my studies to do an internship at Dryden Flight Research Center in southern California.

As Dryden is located in the middle of the desert, there is not much fun to do in the evenings (LA is close, but not close enough to go every weekend). So I decided to build an Arduino based quadcopter.

Yes, I should have started documenting this before now, but better late than never. So the original goal of this project was to create an autonomous quadcopter that could bounce around the room and not hit anything. Then, a little while ago, I decided that flying a quadcopter manually with a remote was too hard. So I decided that I needed to build an android app that would be able to control the quadcopter via tilt, with a button to turn autopilot or autohover on.