1. Principle: A Revolutionary Electromagnetic Power Source
The Frameless Torque Motor is a groundbreaking motor design that completely abandons traditional mechanical structures such as housing, bearings, and shafts, retaining only the core electromagnetic drive components-the stator and rotor.
1.1 Core Component Analysis
Stator: Composed of a ring-shaped laminated iron core made of high-precision silicon steel sheets, with precisely wound copper coils embedded inside. When a three-phase current is applied, the coils generate a rotating magnetic field, whose strength is directly related to the current frequency and winding topology (as shown in Figure 1, the stator cross-section of a motor from Shenzhen QH Motor).
Rotor: Uses high-performance rare-earth permanent magnets (such as neodymium-iron-boron) to form a circular magnetic pole array, directly mounted onto the main shaft of the equipment through an interference fit. The air gap between the rotor and stator is typically controlled between 0.3-0.8mm to maximize magnetic energy utilization.
1.2 Working Principle
When current flows through the stator windings, the generated rotating magnetic field interacts with the static magnetic field of the rotor's permanent magnets. According to Maxwell's stress tensor principle, continuous torque is produced in the tangential direction. Since mechanical transmission components are eliminated, energy conversion efficiency exceeds 95%, achieving zero-backlash precision control.
2. Features: Redefining the Performance Boundaries of Drive Systems
2.1 Extreme Compactness and Lightweight Design
The frameless design reduces motor volume by 40%-60%. For example, the KBM-40 series from Kinco features an outer diameter of just 40mm, weighs less than 300g, yet delivers a 15Nm peak torque, making it ideal for applications with tight space constraints, such as humanoid robot finger joints.
2.2 Breakthrough in Dynamic Performance
Millisecond-Level Response: Rotor inertia is 1/5 of that of traditional motors, with a command response time of <3ms (data source: Allied Motion test report), meeting the bionic joint movement frequency requirement of 10+ actions per second.
Enhanced Torque Density: Using Halbach magnet arrays to optimize the magnetic field distribution, the latest products, such as the TBM series from Kollmorgen, achieve a torque density of 40Nm/kg, which is three times higher than that of conventional servo motors.
2.3 A Revolution in System Integration
The motor can be directly embedded into robotic arm joints, rotating frames of medical CT scanners, etc. Encapsulation with epoxy resin ensures an IP67 protection rating, eliminating the need for couplings and reducers, thereby reducing system complexity and failure rates.
3. Applications: From Precision Manufacturing to Humanoid Robots
3.1 Humanoid Robot Joint Drives
Tesla Optimus: Among its 28 joints, 14 use frameless torque motors, enabling 11 degrees of freedom for hand gripping (individual finger joint motors are ≤25mm in diameter).
Domestic Breakthroughs: The Walker X robot co-developed by Hechuan Technology and UBTech features knee joint motors with a continuous torque of 180Nm, weighing only 1.2kg, supporting dynamic walking with a 70kg load.
3.2 High-End Equipment Applications
Semiconductor Lithography Machines: Used for nanometer-level wafer stage positioning, achieving ±0.1μm repeatability (e.g., ASML equipment configurations).
Satellite Pointing Mechanisms: Designed to withstand extreme space temperatures (-150°C to +120°C), with samarium-cobalt magnets to prevent demagnetization.
3.3 Emerging Market Boom
In 2023, demand for frameless torque motors in the humanoid robotics industry surged, with 28-40 units per robot. The global market is expected to exceed ¥8 billion (approx. $1.1 billion) by 2025 (source: Humanoid Robotics Industry Report).
4. Competitive Landscape: The Path to Domestic Market Penetration
4.1 Foreign Brands Dominating the High-End Market
Kollmorgen: Holds over 60% of the global high-end market. The TBM series supports customized magnetic field designs, enabling applications requiring over 2000Nm of torque.
Parker Hannifin: The Aries series integrates intelligent sensors, capable of real-time temperature and vibration monitoring, preventing unexpected shutdowns.
4.2 Rapid Growth of Domestic Manufacturers
Kinco: The third-generation frameless motor features a "segmented skewed pole" technology, reducing torque ripple to below 0.5%, breaking foreign dominance in the collaborative robot sector.
Hechuan Technology: Co-developed a "magneto-thermal-mechanical coupling simulation platform" with universities, halving the motor design cycle. Their product lineup covers sizes from Φ15mm to Φ250mm, meeting diverse application needs.
5. Future Trends: Advancements in Materials and Intelligence
Superconducting Materials: Low-temperature superconducting windings could increase torque density to 60Nm/kg, with laboratory breakthroughs already achieved.
Self-Sensing Motors: Embedded MEMS sensors provide real-time feedback on load variations, enabling Boston Dynamics' Atlas robot to perform high-difficulty backflips.
Green Manufacturing: The use of water-based insulation coatings and recyclable magnets reduces carbon emissions by 35% compared to traditional motors.
