About RoboSim Tools — who built this and why

RoboSim Tools is built and maintained by Rahul Rajelli, a robotics R&D engineer, on the principle that free tools should be correct enough to bet real work on — not just correct enough to demo.

By Rahul Rajelli · updated 2026-07-10 · RSS

RoboSim Tools exists because of a repeated annoyance: every time a robot description needed converting between formats — URDF, SDF, MJCF, CAD — the free options online were either missing, or silently wrong in ways that only showed up after an hour of debugging a physics engine. So each tool here started the same way: a real conversion problem, solved once carefully, then published so nobody else has to solve it badly.

The one rule

Every tool is verified against a ground truth before it ships — not just tested against hand-written examples. The URDF→MJCF converter's output is compile-checked in real MuJoCo. The SDF pose-transform math is cross-checked against an independent NumPy implementation. The mesh inertia integration matches the analytic solution for a solid cube to floating-point precision. The CRA compliance checker cites the actual regulation text, article by article — not a paraphrase of a paraphrase. Where a claim couldn't be verified this way, the tool says so, out loud, in a warning.

This is also why files never leave your browser: every tool runs as JavaScript and WebAssembly on your machine. Nothing is uploaded, so there's nothing to leak — a proprietary CAD file or an unreleased firmware lockfile stays exactly where it started.

Who's behind it

Rahul Rajelli is an R&D engineer working in robotics and autonomous systems. This site is where that work's byproducts — the format-conversion scripts, the validation checks, the "wait, why does this explode in Gazebo" debugging sessions — get cleaned up and given away. He's available for freelance projects and open to full-time robotics R&D roles — work with him.

Found something wrong?

Every page has a bug-report form in the footer — use it. Correctness is the entire premise of this site, and a wrong output reported is worth more than ten right ones nobody checked.

See what's changed recently on the changelog, or start with the wiki if you're new to robotics simulation.