China's Frameless Torque Motor Suppliers: The Muscles of Humanoid Joints

A humanoid robot is a stack of joints, and every rotating joint is driven by a frameless torque motor — a ring-shaped, ironless-core motor that wraps around the joint itself. UBTECH's Walker X packs 36 of them in high-performance actuators; AgiBot's A2 pairs them with planetary reducers for 52 Nm/kg joint modules. For decades the field belonged to Western names like Kollmorgen and Allied Motion. China now owns the volume.

Why frameless torque motors are the humanoid standard

A frameless motor is a rotor and stator with no housing — it is embedded directly into the joint structure, saving weight and axial space. Its high torque density and low inertia give fast, precise motion with no backlash, exactly what a humanoid needs to balance, walk and grasp. Pair it with a harmonic or planetary reducer and you get the integrated "joint module" that nearly every Chinese humanoid — Unitree, AgiBot, UBTECH, Xiaomi — is built around.

The Chinese lineup

Inovance — the volume leader

Shenzhen-based Inovance (汇川技术, 300124) is China's servo champion and now the country's largest frameless torque motor maker, holding more than half of domestic share. Its fourth-generation TMB frameless motors span the full 25-115mm range, and the company is already developing next-generation axial-flux ultra-thin frameless motors for even denser joints. Because Inovance makes its own encoders, servo drivers and FOC control algorithms, it can ship a complete, tuned joint solution — a moat few rivals can match.

Kinco — the pioneer

Kinco (步科股份, 688160) was the first Chinese company to mass-produce frameless torque motors. Its fourth-generation FMK series, launched in July 2025 alongside a hollow-shaft RD driver, reaches 18.3 Nm/kg torque density — among the highest in China. Kinco has deep ties to Xiaomi and UBTECH, shipped roughly 35,000 units in 2026 Q1, and is now pushing into humanoid-specific platforms after dominating collaborative-robot joints.

The challengers

Leadshine (雷赛智能, 002979) is the most integrated challenger — its 2024-founded robotics arm combines high-density frameless motors, hollow-cup motors, planetary and harmonic joint modules and dexterous hands, and it claims to have entered the supply systems of 80% of China's major humanoid OEMs. MOONS' (鸣志) pairs frameless motors with its leading coreless lineup. Specialists such as Guangzhou Haozhi, Chengdu Weijing, Hangzhou SDM (which also makes magnetic encoders) and Han's Laser-group Han's Motor round out a fast-deepening bench.

Why China dominates

Three structural advantages explain the shift. First, rare-earth magnets: China controls most of the world's NdFeB magnet production, giving domestic motor makers a raw-material cost edge. Second, the servo ecosystem — Inovance, Leadshine and Kinco all built decades of servo expertise for industrial automation and simply ported it to robot joints. Third, integration: the same firms sell the motor, driver, encoder and reducer, so a humanoid maker buys one tuned package instead of stitching five vendors together.

What to watch

• Torque density arms race — axial-flux and ultra-thin designs (Inovance's next move) could push density past 20 Nm/kg.
• QDD integration — motors merged with quasi-direct-drive actuators, as in Unitree's R1, cut BOM cost further.
• Consistency at scale — the real bottleneck is mass-producing low-cogging windings at 1M-unit volumes, not just lab prototypes.

Frequently asked questions

Which Chinese company makes the most frameless torque motors?

Inovance (汇川技术) leads China's frameless torque motor market with more than 50% domestic share — its 4th-gen TMB series spans the full 25-115mm range.

What is a frameless torque motor used for?

Frameless torque motors drive rotating joints in humanoid and collaborative robots. The rotor and stator mount directly inside the joint, giving high torque density with no backlash — UBTECH's Walker X alone packs 36 of them.

How does China's frameless torque motor compare to the West?

Chinese makers such as Inovance, Kinco and Leadshine now match Western torque-density specs — Kinco's FMK hits 18.3 Nm/kg — while undercutting prices via rare-earth advantage and a full in-house servo ecosystem.

Who does Kinco supply frameless motors to?

Kinco (步科股份) ships its 4th-gen FMK frameless motors to Xiaomi and UBTECH, and delivered roughly 35,000 units in 2026 Q1.