How Does the HONPINE JRM Planetary Robot Joint Module Address Temperature Rise in Continuous Operation?

As robots are increasingly deployed in smart factories, automated logistics, unmanned inspection, and specialized operations, 24/7 continuous operation is becoming a common requirement. Expectations for robots are also evolving from simply completing basic movements to maintaining stable and reliable performance over extended operating periods.

As a core motion component, the thermal performance of a robot joint module directly affects the operating stability of the entire robotic system. Increasing demands for long-duration and high-load operation therefore place higher requirements on joint temperature control.

To address the common challenge of temperature rise in robot joints, HONPINE focuses on the underlying design of the joint module rather than relying primarily on external cooling as a corrective measure. With high energy conversion efficiency and low-loss operation as key design objectives, HONPINE develops integrated robot joint modules (JRM Planetary Joint Module) designed for low temperature rise, high reliability, and scalable production, providing core motion components for robotic systems operating under demanding conditions.

During long-duration, high-load operation, losses from the motor, transmission, and drive unit are major sources of heat accumulation within a robot joint. The compact structure of a joint module also limits available heat dissipation space, making thermal management particularly challenging during continuous operation.

To address this challenge, HONPINE has developed a self-developed thermal management approach based on reducing losses throughout the joint module and controlling heat generation at its sources. Starting from the underlying design of the module, the approach aims to reduce heat generation and improve thermal stability during continuous operation.

1. Design Strategy: Control Temperature Rise at the Source

HONPINE focuses on optimizing the primary heat-generating components of the robot joint module rather than relying solely on downstream cooling measures.

Through efficiency improvements across the motor, planetary gearbox, and drive unit, HONPINE reduces electromagnetic losses, mechanical friction losses, and power-device switching losses during operation. By reducing heat generation at the source, the joint module can maintain lower heat accumulation within its compact integrated structure.

This system-level low-loss design is intended to support stable thermal performance under long-duration continuous operation.

2. Motor Optimization: Multi-Dimensional Electromagnetic Design

The motor is one of the primary heat-generating components in a robot joint module. Copper loss and iron loss have a direct impact on the basic temperature-rise characteristics of the module. HONPINE therefore optimizes the motor from multiple aspects, including magnetic circuit design, material selection, and winding processes, to improve electromagnetic energy conversion efficiency.

Electromagnetic Design

HONPINE optimizes the pole-slot combination to improve the winding factor while refining the magnetic circuit and air-gap structure.

For low-speed operation, cogging torque is controlled to within 1% of rated torque, helping maintain smooth motion and stable low-speed operation.

For high-speed operation, the back-EMF harmonic distortion rate is controlled to within 1%, helping reduce iron losses and improve efficiency during high-speed operation.

High-Performance Materials

The stator and rotor use 0.2 mm high-grade non-oriented electrical steel, helping reduce eddy-current losses and improve magnetic saturation characteristics.

The motor also uses UH-series high-grade high-temperature-resistant permanent magnets, providing high residual flux density and high coercivity to reduce the risk of demagnetization under high-load operating conditions.

Key materials, including the electromagnetic wire, insulation components, and bonding adhesive, are selected in high-temperature specifications. The core components can withstand temperatures of up to 180°C, supporting long-duration continuous operation.

Winding Process

The motor uses an automated multi-slot continuous winding process, increasing the slot fill factor to 80%.

Under the same torque output conditions, a higher slot fill factor can help reduce current-related heat generation. The winding process also reduces the number of solder joints, improving overall operational reliability.

With these combined optimizations, the motor achieves an overall efficiency of up to 92%, helping reduce heat generation at one of the primary heat sources within the joint module.

3. Transmission and Drive Efficiency: Reducing Losses Across the Powertrain

In addition to motor losses, mechanical friction in the planetary gearbox and switching losses in the drive unit can also affect the thermal performance of a robot joint module during continuous operation.

Planetary Transmission Efficiency

On the transmission side, HONPINE optimizes the structure and matching precision of the planetary gearbox.

The efficiency of the single-stage planetary gearbox can reach up to 97%, while the efficiency of the two-stage planetary gearbox remains around 95% under the specified operating conditions.

Higher transmission efficiency helps reduce mechanical losses and the associated heat generated by gear meshing and friction.

Drive Efficiency

On the drive side, the joint module uses third-generation gallium nitride (GaN) power devices.

Compared with conventional power devices, GaN devices can significantly reduce conduction and switching losses. The drive unit achieves an overall operating efficiency of more than 95%, helping reduce heat generation associated with high-frequency electrical switching.

Through coordinated optimization of the transmission and drive systems, the joint module is designed to achieve efficient operation across the entire powertrain.

4. Full-Load Validation: Temperature Rise Below 1 K After 30 Minutes

The low-loss and low-temperature-rise characteristics achieved through theoretical design must ultimately be verified under actual load conditions.

To simulate the continuous operating conditions of robots working under demanding loads, HONPINE conducted a full-load back-to-back test on the C6345 planetary robot joint module.

The C6345 module has a rated torque of 12 N·m and a rated speed of 120 rpm. A servo back-to-back test setup was used to reproduce continuous loaded operation.

After 90 minutes of continuous full-load operation, the joint module reached a stable thermal equilibrium.

Under an ambient temperature of 25°C, the temperature-rise difference after 30 minutes was below 1 K, while the final equilibrium temperature stabilized at 61.42°C.

Even under full-load operating conditions, the joint module maintained a stable thermal equilibrium, helping prevent continuous temperature escalation during prolonged operation.

5. Underlying Performance for Long-Duration Continuous Robot Operation

From multi-dimensional motor optimization and source-level reduction of electromagnetic losses to efficiency improvements across the transmission and drive systems, HONPINE approaches thermal management by reducing heat generation throughout the joint module.

The full-load test of the C6345 planetary robot joint module further demonstrates its thermal behavior under continuous operating conditions.

By combining high motor efficiency, efficient planetary transmission, high-efficiency GaN drive technology, and system-level low-loss design, HONPINE develops planetary robot joint modules designed to reduce thermal management challenges for robotic system integrators.

This approach is intended to support robots operating under long-duration, high-load, and continuous-duty conditions, while providing a stable thermal foundation for reliable robotic motion.