What Kind of Robot Joint Module Should You Choose for High-Precision Humanoid Robot Control?

In 2026, after technical discussions with dozens of humanoid robot manufacturers, one thing has become increasingly clear to me: many companies are not simply developing humanoid robots that can walk or perform basic movements. They are working toward a much more ambitious goal — building humanoid robots capable of performing delicate, practical tasks that genuinely help people in everyday life and industrial environments.

Hello everyone, I'm Theodore Li, Technical Director at HONPINE.

Today, I'd like to introduce a harmonic joint module designed for humanoid robots that need to do more than just move. For robots expected to perform real-world tasks requiring precise positioning, accurate force control, and stable motion, I'd like to recommend the HONPINE HAG Harmonic Joint Module.

Five Key Advantages of the HONPINE HAG Harmonic Joint Module

1. High Positioning Accuracy and Excellent Torque Control

The foundation for human-like and precise movements

Humanoid robots need to perform complex tasks such as assembly, object manipulation, grasping, and walking. These applications place extremely high demands on joint positioning accuracy and motion control.

The HONPINE HAG harmonic joint module offers several features to support high-precision motion control:

Dual Absolute Encoders: All models are equipped with a 20-bit single-turn absolute encoder (1,048,576 counts per revolution) and a 12-bit multi-turn absolute encoder, supporting the BiSS-C communication protocol.

High Positioning Accuracy: Unidirectional positioning accuracy can reach ≤45 arcsec, with repeatability of ≤10 arcsec. These specifications help humanoid robots achieve fine motion adjustments and more consistent positioning during complex operations.

Optional Torque Sensor: According to the product specifications, the HAG series supports an optional integrated torque sensor (T suffix), with measurement ranges covering 25 N·m to 500 N·m and nonlinearity as low as 0.5%.

This enables torque-based control strategies such as compliant interaction, force feedback, and collision detection, which are essential for safer human-robot collaboration and delicate manipulation tasks.

High Torsional Stiffness: Larger models, such as the HAG-40, offer torsional stiffness of up to 18.6 × 10⁴ N·m/rad. High torsional stiffness helps reduce deformation under load, suppress unwanted vibration, and maintain motion stability and end-effector positioning accuracy.

2. High Torque Density and Powerful Overload Capacity

Meeting the demanding power requirements of humanoid robots

Hip and knee joints need sufficient torque to support demanding movements such as jumping, climbing stairs, standing up, and recovering from a fall. At the same time, the limited installation space and battery capacity of humanoid robots make torque density and overall weight critical design considerations.

The HONPINE HAG series provides a broad torque range to accommodate different joint requirements.

A Wide Torque Range: From the HAG-11, with peak torque ranging from 11.4 to 18 N·m, to the HAG-40, which delivers up to 800 N·m of peak torque and 557 N·m of rated torque, the HAG series covers a wide range of humanoid robot joint applications.

Smaller models can be considered for applications such as wrist and arm joints, while larger models are suitable for higher-load joints such as the shoulders, hips, and knees, depending on the robot's mechanical design and load requirements.

Strong Short-Term Overload Capacity: Humanoid robots frequently encounter transient high-load conditions during dynamic movements. For example, the HAG-25 has a rated torque range of 48–115 N·m and a peak torque range of 86–203 N·m.

This additional short-term torque capacity helps support demanding movements such as jumping, rapid acceleration, and fall recovery.

3. Compact, Lightweight Design with Hollow-Bore Cable Routing

Optimized for the limited internal space of humanoid robots

Humanoid robots have highly constrained internal layouts. Every component must be carefully arranged, while excess weight directly affects battery life, dynamic performance, and overall energy efficiency.

The HAG harmonic joint module addresses these challenges through its integrated architecture and hollow-bore design.

Hollow-Bore Cable Routing: The HAG series features a central through-hole for internal cable routing. For example, the HAG-20 has a central bore diameter of Φ16.8 mm, while the HAG-40 provides a Φ28 mm bore.

Power cables, communication lines, and other necessary wiring can pass through the center of the joint, helping simplify internal cable management and reduce interference, bending, and wear caused by external cable routing.

Lightweight and Highly Integrated Structure: The HAG integrates a frameless torque motor, harmonic reducer, driver board, and optional electromagnetic brake into a compact joint assembly.

Taking the HAG-20 as an example, its total weight is only 1.63 kg with the brake installed. This compact structure makes it suitable for humanoid robot designs where installation space and weight are major constraints.

4. Excellent Dynamic Response and Communication Compatibility

Supporting responsive motion and seamless system integration

Humanoid robots must continuously adjust their joint movements in response to changing commands, external forces, and environmental conditions. This requires joint modules with responsive motion performance and reliable communication interfaces.

High-Speed Operation: Smaller models, such as the HAG-14, can reach a maximum speed of 98 rpm, supporting applications that require relatively fast joint movements, including walking and rapid arm movements.

Industrial Communication Protocols: The HAG series supports CANopen and EtherCAT communication protocols, making it easier to integrate the joint module into different robot control architectures.

Built-in STO Safety Function: The HAG also incorporates a Safe Torque Off (STO) function. When triggered by an appropriate safety control system, STO disables the generation of motor torque, helping reduce risks during emergency situations and system faults.

It is important to note that STO does not provide mechanical braking or mechanically lock the joint. Applications requiring position holding after power loss should also consider the optional electromagnetic brake.

5. High Structural Rigidity and Reliable Mechanical Design

Maintaining joint stability under demanding operating conditions

Humanoid robot joints are exposed to complex forces during walking, standing, lifting, and other dynamic movements. In addition to transmitting torque, the joint module must withstand external bending moments and maintain structural stability.

High Tilting Stiffness: Larger HAG models provide high tilting stiffness. For example, the HAG-40 reaches 175 × 10⁴ N·m/rad, helping the joint withstand bending moments generated during robot movement and external loading.

This is particularly important for load-bearing joints such as the hips and knees, where structural deformation can affect the robot's motion accuracy and stability.

Optional Electromagnetic Brake: The HAG series offers an optional brake configuration. For humanoid robots that need to maintain a standing posture or hold a joint position when the motor is not actively driving, an electromagnetic brake can provide additional mechanical holding capability.

This is especially valuable for applications where maintaining joint position during power interruptions or idle periods is an important design requirement.

Is the HONPINE HAG Harmonic Joint Module Right for Your Humanoid Robot?

If your company is developing humanoid robots designed to perform real-world tasks rather than simply demonstrate basic movements, joint module selection deserves careful consideration.

Positioning accuracy, torque control, overload capacity, structural stiffness, dynamic response, and system integration all influence the robot's ability to perform complex tasks reliably.

The HONPINE HAG Harmonic Joint Module combines a harmonic reducer, frameless torque motor, integrated drive electronics, absolute encoders, and optional torque sensing and braking functions in a compact joint solution.

If you are developing humanoid robots that require high-precision motion control and reliable joint performance, contact HONPINE to request the HAG Harmonic Joint Module datasheet and discuss your application requirements with our engineering team.