Analog Self-leveling and Hovering Quad-copter

Nowadays, drones can simply be purchased or assembled by plug and play kits. These options run the gamut of affordability and functionality, but are consistent in their obfuscation of the relatively complex control theory implemented by the drones. The computing power of modern microcontrollers and sensors allows drones to hover and remain level so effectively that stability appears to be an inherent trait of quad-copters. This is anything but true; with six degrees of freedom, only four input sources, and minimal motion dampening provided by air, quad-copters are not trivial to keep motionless. There is a reason that all commercial and industrial drones are digital, and it is the same reason that an analog drone is a project worth taking on.

First Attempt

Four DC 12v motors were used in total, one per arm of the quadcopter. The motors were mounted in a 3D printed PLA fixture that connected the motor to a 4" aluminium rod. All four rods were fixed in a 3D printed PLA mount that also held the circuitry and battery. The battery was a 3S LiPo that could deliver roughly 4A at full charge. The circuitry