Quadcopter Basics

Hello All -

I'm an avionics systems maintainer in the Air Force. I'm currently stationed at Little Rock AFB in Arkansas. I'm also an electrical engineering student at one of the universities in the area. I've purchased several little RC toys which have ended up in pieces all around my apartment in attempts to understand the "inner workings". I've got some money to play with and I'm ready to start building this stuff from scratch.

My ultimate goal here is to build a quadcopter with a camera -drone-, to fly around and get some high altitude shots. However, I'd first like to get a firm grasp on the basics. I've never attempted to design or construct any RC projects, but I do have an understanding of basic electronics.

I've read some other posts, one I found particularly helpful was:
http://diydrones.com/forum/topics/newbie-quadcopter-questions

I have a few additional questions I couldn't find answered anywhere else:

WARNING: Extreme Newbie here..

-I understand I'll need 4 motors and 4 props, I've seen that these propellers come in a CW and CCW rotation design. Should I use two CW and two CCW? Do these alternating designs assist with stabilization?

-I read that ESC's are essential for RC projects. Is an ESC basically a variable resistor used for throttle control? Do I need one for each motor, or should I just put one in series with the power supply and and branch the 4 parallel motors off from there?

-I dont understand how this craft is steered. Are servos attached to the motors angling the direction of the props? Are quadcopters stable enough to be flown without some form of accelerometer keeping them balanced?

-If someone could break down the basic electrical setup of a qaudcopter, I would appreciate it. Is the RC component in series with the motors and the ESC's?

I would appreciate any patient readers willing to break this stuff down for me. Also if anyone could recommend any books that would help an extreme beginner I would appreciate it. Thanks

-Tyler

An ESC is basically a computer that senses the position of the rotor, computes which coils need to be turned on and off to move the rotor to a new position, and applies the current to them using high-power transistors. All this a couple thousand times per second, so the motors spin. Each motor needs its own ESC.

You talk to the ESC through a flight computer, usually using PWM. The flight computer does its own measurements - it determines the vehicle's state using gyros, accelerometers and other sensors (really required are just the gyros, the rest is just a great help). It then reads your input coming from the RC receiver, computes what needs to be done to get it from the current state to the state you want (e.g. pitch +10°), and commands ESCs accordingly.

Re: steering - go through this wiki article. It explains everything. Good luck with your build :)

Replies

Overwatch May 9, 2010 at 1:50pm

An ESC is basically a computer that senses the position of the rotor, computes which coils need to be turned on and off to move the rotor to a new position, and applies the current to them using high-power transistors. All this a couple thousand times per second, so the motors spin. Each motor needs its own ESC.

You talk to the ESC through a flight computer, usually using PWM. The flight computer does its own measurements - it determines the vehicle's state using gyros, accelerometers and other sensors (really required are just the gyros, the rest is just a great help). It then reads your input coming from the RC receiver, computes what needs to be done to get it from the current state to the state you want (e.g. pitch +10°), and commands ESCs accordingly.

Re: steering - go through this wiki article. It explains everything. Good luck with your build :)
3D Robotics

Chris Anderson May 9, 2010 at 12:55pm

1) Yes, to counter motor torque
2) Yes. You need four
3) All by changing motor speeds. No mechanical angling at all.
4) RC > autopilot/controller board > 4 ESCs

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Quadcopter Basics

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