Analysis of Joint Motors Used in Unitree Robots

Humanoid robots and quadruped robots require highly integrated joint actuators to achieve fast movement, balance control, and strong load capacity. One company that has gained significant attention in the robotics industry is Unitree Robotics, known for its quadruped robots and humanoid robots.

A key factor behind the performance of these robots is the joint motor system used in their actuators. In this article, we analyze the types of motors used in Unitree robots, their structure, and why these motors are well suited for advanced robotic systems.

Overview of Unitree Robot Joint Actuators

Most Unitree robots use highly integrated electric actuators that combine multiple components in a compact module.

A typical Unitree joint actuator includes:

  • High-performance electric motor

  • Gear reduction system

  • Encoder sensors

  • Motor driver electronics

  • Structural bearings

This integrated design allows robots to achieve high torque output, precise control, and compact mechanical structure.

For example, the humanoid robot Unitree H1 uses a self-developed M107 joint motor module that can produce up to 360 N·m torque in the knee joint.

1. Permanent Magnet Synchronous Motors (PMSM)

The core motor technology used in many Unitree robots is the permanent magnet synchronous motor (PMSM).

These motors are designed with high-speed internal rotors and low inertia, enabling rapid response and efficient torque generation.

Advantages

  • High power density

  • Fast response speed

  • High efficiency

  • Compact design

Applications in Unitree Robots

PMSM motors are typically used in:

  • Hip joints

  • Knee joints

  • Shoulder joints

  • Waist joints

These joints require high torque and dynamic control.

2. Integrated BLDC Actuator Motors

Many Unitree actuator modules are based on brushless DC motor technology (BLDC) integrated into joint modules.

The motors are combined with advanced motor control methods such as FOC (Field-Oriented Control) to achieve smooth motion and low torque ripple.

Advantages

  • High efficiency

  • Low maintenance

  • Smooth torque output

  • Long lifespan

These motors are ideal for robots that require continuous dynamic motion, such as walking or running.

3. Planetary Gear Motor Systems

To achieve high torque output, Unitree actuators commonly include planetary gear reduction systems.

Planetary gearboxes provide:

  • High torque amplification

  • Compact structure

  • High transmission efficiency

For example, some Unitree joint modules include optimized planetary reducers integrated with the motor to deliver strong output torque while keeping the actuator lightweight.

4. High-Torque Integrated Joint Motors

The humanoid robot Unitree H1 uses an advanced joint motor called M107.

Key features include:

  • Maximum torque up to 360 N·m

  • Hollow shaft design

  • Dual encoder feedback

  • High torque density

These actuators enable the robot to achieve dynamic walking speeds up to 3.3 m/s and maintain stable balance during movement.

Typical Torque Output of Unitree Joint Motors

Different robot joints require different torque levels.

Robot Joint Typical Torque
Hip joint ~220 N·m
Knee joint ~360 N·m
Ankle joint ~59–75 N·m
Arm joint ~75–120 N·m

These torque values allow the robot to support body weight and perform complex dynamic movements.

Structure of a Typical Unitree Robot Joint

A Unitree robot joint actuator usually includes the following components:

  1. High-speed electric motor (PMSM or BLDC)

  2. Planetary gear reduction system

  3. Dual encoder feedback

  4. Crossed-roller bearing for high load capacity

  5. Integrated motor controller

This design allows the actuator to achieve high torque, precise control, and reliable operation.

Why Unitree Actuators Are Efficient

Unitree’s actuator design has several advantages compared with traditional robotic systems.

Integrated Design

Motor, gearbox, and sensors are combined into one module.

High Torque Density

Compact motors can produce very large torque outputs.

Cost Efficiency

Integrated actuator design reduces the number of external components.

High Control Precision

Encoders provide precise position and velocity feedback.

Future Trends in Robot Joint Motors

The design of robot joint motors is evolving rapidly as humanoid robots become more common.

Future actuator systems are expected to include:

  • Higher torque density motors

  • Smaller integrated actuator modules

  • Advanced torque sensors

  • More efficient brushless motor designs

These innovations will allow humanoid robots to become stronger, faster, and more energy efficient.

Conclusion

Unitree robots use advanced integrated joint actuators powered by permanent magnet synchronous motors and brushless motors combined with planetary gear reducers.

These actuators provide:

  • High torque output

  • Compact structure

  • Fast dynamic response

  • Precise motion control

As humanoid robots continue to evolve, integrated motor systems like those used in Unitree robots will play a critical role in enabling high-performance robotic movement.

Back to blog