#simulation

vsim_d is the physics daemon that flies Vayu's real firmware in software. A field report from the seam where Newton–Euler rigid-body mechanics meets RK4, quaternion drift, impulse contact, and a hard-real-time loop — including the cleanest way I know to turn a triangle mesh into an inertia tensor, and the bugs where the physics was right but the numerics (or the systems) lied.

We built a closed-loop PID autotuner that flies its own experiments in simulation and searches the gain space — eight optimizers, a chatter-aware cost, and two failure modes that looked solved but weren't. A deep dive into the system, the algorithms, and the fixes.