Overview

September 23, 2025 / Los Angeles, US. Unitree SDK2 is a CycloneDDS-based communication & control framework for Unitree robots. It works without ROS2 while remaining ROS2-compatible, and provides native C++ APIs plus a Python wrapper (pybind11) for rapid prototyping and production deployments.

Key Characteristics

• Low-latency DDS: direct data exchange with robot hardware
• No ROS2 required: optional ROS2 interoperability via DDS
• Cross-language: C++ APIs, Python wrapper via pybind11

System Requirements

• Ubuntu 20.04 or 22.04 (recommended)
• Python 3.8+
• CMake 3.16+  |  g++ 9.0+

Installation

1. Clone repository

git clone https://github.com/unitreerobotics/unitree_sdk2
cd unitree_sdk2

2. Build the SDK core (C++)

mkdir build && cd build
cmake ..
make -j4

3. Install Python wrapper & dependencies

cd ../python_wrapper
pip install .
pip install pybind11 cyclonedds

If installation fails, ensure python3-dev and DDS runtime libraries are installed.

Quick Start (Python)

from unitree_sdk2 import RobotInterface

robot = RobotInterface()
robot.start()  # establish communication

# Basic motions
robot.move_forward(speed=0.2, duration=3.0)
robot.sit_down()
robot.stand_up()

Accessing Robot State

# Joint states
angles = robot.get_joint_angles()
vels   = robot.get_joint_velocities()

# IMU
imu = robot.get_imu_data()
print(imu.orientation, imu.angular_velocity)

# Foot contact forces
forces = robot.get_foot_forces()

Advanced Motion Control

# Custom trajectory
traj = [
  {"x":0.2, "y":0.0, "z":0.0, "duration":2.0},
  {"x":0.2, "y":0.1, "z":0.0, "duration":2.0},
]
robot.execute_trajectory(traj)

# Mode switching
robot.set_motion_mode("trot")
robot.set_motion_mode("stand")

ROS2 Interoperability

• SDK2 and ROS2 nodes can share topics via DDS
• Publish IMU to /imu/data for RViz while keeping low-latency Python control
• Use a DDS domain bridge in mixed environments

Best Practices

• Run on Ubuntu 20.04/22.04; avoid mixed OS toolchains
• Keep robot & control PC on the same subnet
• Prototype in Python; move performance-critical parts to C++

Troubleshooting

• ImportError: add CycloneDDS path to LD_LIBRARY_PATH
• High latency: check Wi-Fi/Ethernet quality (DDS is sensitive to packet loss)
• No response: ensure robot control lock is released
  

 

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