What a multirotor is

A machine that balances on air

A multirotor is an aircraft held up by several propellers pointing straight up. It has no wings and no rudder: everything it does, it does by changing how fast each motor spins. The one you build in this course is a quadcopter X: four motors at the corners of an F450 frame, 450 mm from one motor to the motor across the diagonal.

The parts, in one sentence each

• Frame: the F450's arms and plates. Its lower plate is also the power board that shares the battery between the motors.
• Motors: brushless outrunners, one per arm. Each turns a propeller.
• ESCs (electronic speed controllers): one per motor. They turn the battery's steady current into the three switching phases a brushless motor needs, at the speed the flight controller asks for.
• Flight controller: a small computer (a Pixhawk here) with gyroscopes, accelerometers, a barometer and a compass. It reads them hundreds of times a second and sets each motor's speed to keep the drone where you want it.
• Battery: a 3S LiPo, 2200 mAh. Power module: sits between the battery and everything else and tells the flight controller the voltage and current.
• GPS, radio receiver, telemetry radio: where it is, what the pilot wants, and a link to a ground station.

Why it needs a computer at all

A quadcopter is unstable on its own. A gust tips it a little, one side's propellers then push sideways instead of up, and it slides away while it tips further. No human can correct that fast enough. The flight controller can: it measures the tilt, and within milliseconds spins the low side's motors faster until it is level again. Everything you will build in this course is there to let that loop run.

What you will do

You will meet every part in 2D and 3D, learn the STEM Engine as a tool, wire the drone by hand, write its ArduPilot setup, tuck its wires, and fly it in the Physics Sim: first a hover, then a waypoint circuit, then the missions real drones fly (geofencing, parcel drops, search and rescue, auto-charging, reconnaissance).

Parts, pinouts and wiring: the Cognita STEM Engine's drone library (ArduPilot and PX4 hardware pages; board makers' pinouts). Flight numbers: the Physics Sim's model (UIUC propeller database, APC 10x4.7SF). Packs: Gens ace listings. Airframe motor order and spin: ArduPilot's Connect ESCs and Motors diagrams.