Multi-rotor

A multi-rotor helicopter is a flying vehicle with more than one rotor.

The nice people at http://www.quadheli.com/ have asked for our help designing and building a multi-rotor helicopter.

Several people are using small unmanned helicopters with 4 rotors ("quadheli" or "quadcopter").

BLDC

It appears that most modern small electric aircraft use so-called "brushless DC motors", each one driven by its own "BLDC ESC". (These are easily recognized -- BLDC motors have exactly 3 equally-fat wires that go into them, which come from the BLDC ESC -- as opposed to most electric aircraft a few years ago, which used brushed DC motors with exactly 2 equally-fat wires).

While it is probably not cost-effective to build your own BLDC motor or BLDC ESC, many of us are insatiably curious about what goes on inside these things, and so build one anyway:

• Wikipedia: brushless DC electric motor
• Atmel AVR444: Sensorless control of 3-phase brushless DC motors using ATmega48 (also works without change for ATmega88 and ATmega168). Assumes you've already read Atmel AVR443: Sensor-based control of three phase Brushless DC motor
• AVR194: Brushless DC Motor Control using ATmega32M1: BLDC motor control application using Hall effect position sensors to control commutation sequence.
• MikroKopter: brushless motor controller was designed to give lower latency than off-the-shelf PWM ESCs.
• OpenServo: Brushless DC Servo "The thing that will make our board different from other ESC's is that we are closing the feedback loop with a ... outside position reference."

unsorted

way too many links here. Please delete the ones not relevant to multi-rotor helicopters.

• Wikipedia: quadrotor is a nice introduction. But what are these "three rotor craft" it mentions? (TriCopter? Tri-copter?)
• The Gluonpilot wiki (autopilot) mentions "Quadrocopter" [1]
• MikroKopter wiki [2] semi-open-source "for noncommercial use"
• QC-Copter Wiki [3] : updates all motor speeds at 500 Hz.
• QuadroCopter Wikia [4]
• ARM-o-Kopter wiki [5]
• DIYdrones: "There are a zillion quad- and tri-copters out there" [6]
• DIYdrones: Quadcopters discussion forum [7]
• DIYdrones: Return to Home Quadrocopter (UAVX) [8]
• DIYdrones: "There are loads of open source quadcopters out there, but they're all ..." [9] Is it possible to design a helicopter that avoids this problem?
• the "ChRoMicro - Cheap Robotic Microhelicopter HOWTO" [10], [11] describes "how to build a 300 g helicopter with embedded Linux and Bluetooth datalink from off-the shelf components for less than 500 EUR." Can these ideas be adapted to helicopters with more rotors?
• Quadrotto: Project Quadcopter [12], [13]. Is there any way to avoid making the same mistakes all over again, and instead make fresh new mistakes? :-).
• RCgroups: Multi Rotor Helis discussion forum [14]
• microdrones [15]
• whatnick blog: "quadcopter taking shape"; and other quadcopter posts ... he apparently has a Gumstix Verdex and a BeagleBoard -- are either one of these going on the quadcopter?
• WSN wiki: wireless sensor node platforms -- perhaps we could use one of these boards for our wireless communication, or perhaps make incremental improvements, rather than designing yet another one from scratch?
• Dr. Igor Bensen designed the eight rotor helicopter on the front page of Popular Mechanics 1982 September.
• "Real-time+stabilization+of+an+eight-rotor+UAV+using+optical+flow" Google: "Real-time stabilization of an eight-rotor UAV using optical flow"

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