I wrote a drone simulator from scratch

A force balance, a quaternion and three checks make the first build inspectable.

Read the companion now. The recording is forthcoming; “Free” identifies its planned release track.

A drone simulator begins with a state and a frame contract. Four motor thrusts add to a force; their lever arms and rotor reactions create torques. Newton–Euler equations advance linear and angular motion, while a quaternion carries orientation without the singularity of Euler angles.

The persuasive demonstration is not a rendered hover. It is a force check showing total thrust equals weight, a free-fall trajectory matching the analytic solution, and a short matched open-loop comparison of position and attitude with an independent model. Add motor lag, the firmware rate loop and battery limits only after the simple cases are understandable.

For your companion build, save both successful and failed check plots with the parameter file and simulator revision. Explain one bug that a simple analytic test revealed. The useful artifact is a simulator whose assumptions you can defend, ready to become the controlled world for later experiments.

Take this into your next build

A plausible animation is not validation; start with quantities you can calculate by hand.

Put the idea to work

Write your own quadrotor sim

Build the physics you will later ask a network to understand. Validate simple cases before introducing feedback, then compare a short trajectory with an independent simulator.

Build module 01