Core Driving Forces of Robots: Frameless Torque Motors and Coreless Cup Motors
I. Market Trends of Robot Motors
In recent years, the robot industry has been developing rapidly, with a continuous stream of good news. The field of humanoid robots, in particular, has witnessed numerous breakthroughs. Elon Musk, the CEO of Tesla, revealed that the goal for 2025 is to manufacture thousands of Optimus humanoid robots, and the production is planned to increase to 50,000 to 100,000 units in 2026. In the future, the annual growth could even reach a tenfold increase. Jensen Huang, the founder of NVIDIA, also stated that the robot field will experience a moment of explosive growth similar to ChatGPT.
At the 2025 Consumer Electronics Show, Unitree Robotics showcased various models of robots, including humanoid and quadruped robots. Its G1 humanoid robot is equipped with 23 to 43 joint motors, demonstrating remarkable flexibility and attracting widespread attention in the market.
The rapid development of the robot market has led to a significant increase in the demand for motors. Among various types of motors, frameless torque motors and coreless cup motors have emerged as the core power components of robots. Frameless torque motors, with their high torque output, high-precision control, and compact structural design, are widely used in the joints and arms of robots. Currently, the total demand for frameless torque motors in the industrial robot and service robot industries accounts for approximately 80%. With the rise of the humanoid robot industry, it is estimated that the global market size of frameless torque motors required for humanoid robots will reach 6 billion yuan in 2025 and is expected to climb to 28.2 billion yuan in 2030. Coreless cup motors, on the other hand, with their small size, fast response speed, high operating efficiency, and low noise, play a crucial role in parts of robots that have high requirements for space and performance, such as dexterous hands, heads, and feet. Although coreless cup motors account for only about 5% of the entire robot industry chain, they are irreplaceable in enhancing the flexibility and precise operation capabilities of robots. It is estimated that by 2028, the global market size of coreless cup motors will increase from 810 million US dollars in 2023 to 1.19 billion US dollars, and the market size in China will grow from 290 million US dollars to 470 million US dollars.
II. Frameless Torque Motors: The Core of Robots
(I) Working Principle
Frameless torque motors are special frameless brushless permanent magnet synchronous motors, mainly consisting of a stator and a rotor. They do not have the shaft, bearings, housing, or end covers of traditional motors. Their working principle is based on electromagnetic induction. When the stator windings are energized, a rotating magnetic field is generated. Under the action of this magnetic field, the rotor, by virtue of the characteristics of permanent magnets, efficiently converts electrical energy into mechanical energy, thereby enabling the flexible rotation of robot joints. This direct drive method reduces the energy loss and transmission errors caused by intermediate transmission links during the movement of the robot, resulting in higher control accuracy and response speed.
(II) Applications in Robots
Frameless torque motors can be found everywhere in the field of robots. In humanoid robots, they are widely used in joints such as shoulders, elbows, and wrists, providing powerful power support for various complex movements of the robot’s upper limbs, such as precise grasping and flexible object manipulation. In collaborative robots, frameless torque motors assist robots in working safely and efficiently with humans. For example, in scenarios such as 3C product assembly and logistics sorting, collaborative robots can achieve fast and precise movements with the help of frameless torque motors, improving production efficiency. Take the Tesla Optimus humanoid robot as an example. All 28 joints of its body are equipped with frameless torque motors, enabling Optimus to perform a series of complex and smooth movements such as walking, running, bending over, and grasping objects, demonstrating a high degree of flexibility and mobility.
III. Coreless Cup Motors: Important “Joints” of Robots
(I) Unique Structure and Principle
Coreless cup motors are DC permanent magnet servo control motors, belonging to the category of micro special motors. Their uniqueness lies in the use of a coreless rotor, that is, a hollow cup-shaped rotor. This rotor is directly wound into a cup shape by wires, without additional structural support for winding. This special structural design completely eliminates the electrical energy loss caused by eddy currents in the iron core, and at the same time greatly reduces the weight and moment of inertia of the rotor, reducing mechanical energy loss.
In terms of the operating principle, the stator of a coreless cup motor is usually composed of permanent magnets. When current passes through the hollow cup winding of the rotor, a magnetic field is generated. This magnetic field interacts with the magnetic field of the stator permanent magnets to generate an electromagnetic torque, thereby driving the rotor to rotate. Due to the absence of the obstruction of the iron core, the response speed of the coreless cup motor is extremely fast, capable of achieving rapid start-up, stop, and precise speed control.
(II) Application Demonstration in Robot Scenarios
Coreless cup motors also have a wide range of applications in the field of robots. In the hands of robots, coreless cup motors provide power for the fine movements of fingers. For example, in some robots that need to handle small items, coreless cup motors can achieve high-precision grasping and releasing actions of fingers. Their fast response and precise control characteristics ensure the accuracy and stability of operations.
In small robots or robots that require lightweight design, coreless cup motors have become the first choice for driving. Due to their advantages of small size and light weight, coreless cup motors can effectively reduce the overall weight of the robot, improving the movement flexibility and energy utilization efficiency of the robot. In some small service robots, coreless cup motors are used to drive wheels or joints, enabling the robot to move freely and turn flexibly in narrow spaces.
IV. Stringent Requirements of the Two Types of Motors for Permanent Magnet Materials
(I) Characteristics of Neodymium Iron Boron Permanent Magnet Materials
In frameless torque motors and coreless cup motors, neodymium iron boron permanent magnet materials have become the key choice due to their excellent magnetic properties. Neodymium iron boron permanent magnet materials have the remarkable characteristic of high magnetic energy product, which enables them to generate a strong magnetic field in a small volume, providing efficient energy conversion for motors. Take frameless torque motors as an example. The neodymium iron boron permanent magnets with high magnetic energy product help the motor output greater torque within a limited space, meeting the high torque requirements of robot joints.
It also has high coercive force. High coercive force enables the permanent magnet to resist the interference of external magnetic fields and maintain stable magnetism, thereby ensuring the stability and reliability of motor operation. In coreless cup motors, these characteristics of neodymium iron boron permanent magnets enable the motor to achieve fast response and precise control, meeting the requirements of robots in fine operation scenarios.
(II) Application Characteristics and Difficulties of Permanent Magnet Materials
In robot applications, the requirements for permanent magnet materials are extremely stringent. Since frameless torque motors and coreless cup motors usually face the problem of limited space, especially in devices such as transport robotic dogs, it is necessary to achieve a large torque output within a limited space, which requires the motor to have a sufficiently large torque. To meet this demand, both frameless torque motors and coreless cup motors rely on neodymium iron boron permanent magnet materials with extremely high power density, such as grades 58SH and 54UH. However, many enterprises in the market currently find it difficult to provide these high-performance materials, and the production volume is limited. As a result, many enterprises can only use grades such as 52UH and 54SH as substitutes, which obviously cannot meet the market demand. At present, Hangzhou Magpower Technology Co., Ltd. is mass-producing neodymium iron boron permanent magnet materials of grades 54UH and 54SH, which have received good feedback in the market when applied to motors. The company is also actively developing higher-performance grades such as 58SH and 56UH.
V. Future Development
In the process of the continuous development of robot motor technology, Hangzhou Magnet power Technology Co., Ltd. has demonstrated outstanding strength. As a magnetic material technology company founded by a team of Ph.D.s from the Chinese Academy of Sciences, with outstanding technical capabilities, it has mastered the production technology of high-performance SmCo, high-performance NdFeB, and magnetic device products. The high-performance NdFeB permanent magnet materials it has developed can effectively enhance the performance of frameless torque motors and coreless cup motors, providing stronger support for the application of motors in the field of robots. At the “Overseas Hangzhou” Vietnam Exhibition held in Ho Chi Minh City, Vietnam at the end of March 2024, Hangzhou Magnet power Technology Co., Ltd. exhibited its star product – samarium cobalt one-piece cylindrical magnetic steel. With its leading production process and excellent quality level, it attracted much attention at the exhibition. Numerous buyers asked for the company’s materials and business cards, fully demonstrating its competitiveness in the field of permanent magnet materials.
With the continuous expansion of the robot market, frameless torque motors and coreless cup motors, as the core components of robots, will have broader development space. In the future, Hangzhou Magnet power Technology Co., Ltd. will continue to increase R&D investment, break through technical bottlenecks, and improve product performance and quality to meet the growing market demand. As technology continues to mature, frameless torque motors and coreless cup motors will play a more crucial role in the field of robots, promoting the robot industry to move to a higher level.
