Core Concepts & Architecture

Understanding how Reachy Mini works under the hood will help you build robust applications and debug issues.

Software Architecture

Reachy Mini uses a Client-Server architecture:

1. The Daemon (Server):

   • Runs on the computer connected to the robot (or the simulation).
   • Handles hardware I/O (USB/Serial), safety checks, and sensor reading.
   • Exposes a REST API (localhost:8000) and WebSocket.

2. The SDK (Client):

   • Your Python code (reachy_mini package).
   • Connects to the Daemon over the network.
   • Advantage: You can run your AI code on a powerful server while the Daemon runs on a Raspberry Pi connected to the robot.

Coordinate Systems

When moving the robot, you will work with two main reference frames:

1. Head Frame

Located at the base of the head. Used for goto_target and set_target commands.

2. World Frame

Fixed relative to the robot's base. Used for look_at_world commands.

Safety Limits ⚠️

Reachy Mini has physical and software limits to prevent self-collision and damage. The SDK will automatically clamp values to the closest valid position.

Joint / Axis	Limit Range
Head Pitch/Roll	[-40°, +40°]
Head Yaw	[-180°, +180°]
Body Yaw	[-160°, +160°]
Yaw Delta	Max 65° difference between Head and Body Yaw

Motor Modes

You can change how the motors behave:

• mini.enable_motors(): Stiff. Holds position.
• mini.disable_motors(): Limp. No power.
• mini.enable_gravity_compensation(): "Soft" mode. You can move the head by hand, and it will stay where you leave it. (Only works with the Placo kinematics backend.)

Next Steps

• Quickstart Guide: Run your first behavior on Reachy Mini
• Python SDK: Learn to move, see, speak, and hear.
• AI Integrations: Connect LLMs, build Apps, and publish to Hugging Face.