Free Robotics Software — ROS, Gazebo, MuJoCo and Where to Start
Robotics may be the engineering field where open source won outright. There is no "free alternative to the commercial package" here — the free tools are the standard, in academia and in companies alike. Here is what people actually install, in the order a system gets built.
The infrastructure
1. ROS — Robot Operating System
Not an operating system but a middleware layer: message passing between components, drivers for sensors and actuators, recording and debugging tools, and a uniform robot description in URDF. Around it sits a huge ecosystem — navigation, perception, manipulation — that saves writing from scratch what everyone writes.
What is missing: a steep learning curve, and the migration between generations (ROS 1 to ROS 2) is still painful in older projects.
ROS (Robot Operating System)
Open Robotics
The standard middleware for building robot software.
Get it from the vendorSimulators — before you touch hardware
2. Gazebo
The classic simulator of the ROS world: a 3D world with physics, simulated sensors (LiDAR, cameras, IMU) and direct ROS integration. The same control code runs in simulation and on the real robot.
3. Webots
A simulator with a large ready-made robot library and a far friendlier interface to start with. Fully open since 2018. The natural choice for teaching and for a first project.
4. MuJoCo
A physics engine that is fast and unusually accurate in contact and articulated bodies, which is why it became the standard for control research and reinforcement learning. Open and free since 2022, including for commercial use.
5. PyBullet
The same family, with a Python API built for research: rigid and soft body dynamics, collision detection, inverse kinematics, and loading of URDF, SDF and MJCF. Fast enough to train a learning policy on an ordinary workstation.
Gazebo
Open Robotics
3D robotics simulator with physics and simulated sensors, integrated with ROS.
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Webots
Cyberbotics
Approachable robot simulator with a library of ready robots and environments, common in teaching.
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MuJoCo
Google DeepMind
A fast physics engine for robotics, biomechanics and machine learning.
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PyBullet
Bullet Physics
A physics engine for robotics and reinforcement learning, driven from Python.
Get it from the vendorMapping and localisation
6. Cartographer
Real-time SLAM in 2D and 3D: it builds a map while moving, fusing laser scans with odometry and IMU and closing loops to keep the map consistent. It integrates with ROS and runs on modest hardware carried on the robot.
For processing the point clouds that mapping produces — registration, comparison and cleaning — the tool is CloudCompare.
Cartographer
Cartographer Project
Real-time SLAM in 2D and 3D for robots and mapping platforms.
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CloudCompare
CloudCompare Project
Point cloud and laser scan processing — registration, cleaning, as-built comparison and measurement.
Get it from the vendorThe mechanics of movement — including human movement
7. OpenSim
From Stanford: musculoskeletal modelling and movement simulation from motion-capture and force-plate data. The standard in biomechanics and rehabilitation engineering research, and relevant to exoskeleton design and soft robotics too.
OpenSim
Stanford University
Musculoskeletal modelling and movement simulation, from Stanford University.
Get it from the vendorWhat you need around it
Three tools that are not robotics but accompany every project: Python — the control, analysis and learning language of the whole system; FreeCAD or CadQuery to design the mechanical parts and export them for printing; and KiCad for the control board. The entire chain from mechanics to code is free.
Python
Python Software Foundation
The language behind most modern engineering computation, and its full ecosystem.
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FreeCAD
FreeCAD Project
Open-source parametric 3D modeller with workbenches for solid modelling, FEM, drafting and BIM.
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CadQuery
CadQuery Project
Parametric CAD scripted in Python, on a proper solid-modelling kernel.
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KiCad
KiCad Development Team
Open-source PCB design suite, from schematic to fabrication files, with no limit on layers or board area.
Get it from the vendorWhere to start
If you are starting today: Webots to see a robot move within an hour, ROS alongside it to learn the right architecture, and then Gazebo as the project approaches hardware. If the goal is control research or reinforcement learning — go straight to MuJoCo or PyBullet without passing through ROS.
More in this area: mechanical engineering · simulation tools.