A more extensive and systematic new unified theory of magnetic field modulation motors —the theory of dual-working magnetic field harmonic motors—breaks through the traditional motor theory that has been around for more than a century, ushering in a new era for motor theory.
Nearly two centuries ago, the renowned British physicist Michael Faraday, based on the "magnetic effect of electric current" discovered by physicist Oersted, created the first experimental model of an electric motor, bringing the concept of the motor into the public eye. Especially in the last century or so, with the development of various new technologies and the emergence of new materials, the mechanism and form of electric motors have continuously evolved, faithfully fulfilling their duty of converting electrical energy into mechanical energy with ever-increasing efficiency, driving machines to perform precise operations. Today, from children's electric toy cars to robots, CNC machine tools, and electric cars, electric motors play an irreplaceable role.
As a core drive component of high-end manufacturing equipment, electric motors are developing towards higher precision, higher efficiency, and higher torque density. With the introduction of development plans such as Germany's Industry 4.0 and China's Made in China 2025, intelligent manufacturing has become an inevitable trend. Therefore, the industrial sector is placing increasingly higher demands on the power density of electric motors. However, with the continuous improvement of traditional motor analysis theories, design methods, and design tools, the power density of electric motors has reached its limit, making it extremely difficult to further increase the power density of traditional motors. To address this, leading manufacturing countries worldwide have invested heavily in research and development, but progress has been very slow. China's servo motor industry, constrained by its early weak industrial base, lags significantly behind international advanced technologies in terms of material properties, processing technology, and manufacturing levels. This results in a pressing need to improve key indicators such as servo motor torque density, control accuracy, and product consistency, presenting even greater challenges.
Faced with this predicament, the research team at Huazhong University of Science and Technology, after years of dedicated research, found a unique solution: they innovatively discovered a new mechanism for magnetic field modulation, established a more extensive and systematic unified new theory for magnetic field-modulated motors—the theory of dual-working magnetic field harmonic servo motors—and proved that traditional motor theory is a special case of the unified new theory of magnetic field-modulated motors. It is no exaggeration to say that this new theory breaks through the more than 100-year-old traditional motor theory and ushers in a new era for motor theory.
Specifically, the new unified theory of magnetic field modulation motors has made new breakthroughs in mechanism, structure, and process, and can effectively solve problems such as low torque density, large cogging torque, and poor product consistency in servo motors.
From a mechanistic perspective, based on the internationally pioneering dual-working-magnetic-field harmonic servo motor theory, the research team developed a magnetic field-modulated non-overlapping winding servo motor topology and analytical analysis and design technology for magnetic field-modulated non-overlapping winding servo motors. The team's proposed general motor design principles have increased the torque density of related products by nearly 10% and improved efficiency by 3%. From an architecture perspective, the team established a consistency evaluation system for key indicators of high-end servo motors, revealed the impact of servo motor component machining errors on overall performance, and proposed a robust design method for servo motors that integrates electrical, magnetic, thermal, mechanical, and material characteristics, providing a solution to the problem of poor product consistency in mass production. From a process perspective, by revealing the influence and mechanism of servo motor machining errors and material dispersion on cogging torque, the team proposed a cogging torque reduction method involving spatial magnitude differences, breaking the high dependence of existing cogging torque reduction methods on machining accuracy and material consistency. Actual results show that the product cogging torque ratio has been reduced to 0.59 %, reaching the international advanced level.
Based on a new theory of magnetic field modulation motors, Professor Qu Ronghai's research team won the first prize of Hubei Provincial Science and Technology Progress Award in 2017, obtained 5 authorized invention patents, and developed more than 70 specifications of high-end servo motor products. As a result, Professor Qu Ronghai was elected as an IEEE Fellow (IEEE Fellow is the highest level of membership in IEEE, which is recognized as an authoritative honor and important professional achievement in the academic and scientific community. It is selected annually by peer experts from members who have made outstanding contributions, and the number of elected members does not exceed 0.1 % of the total number of IEEE members).
The research team invented several novel magnetic field modulation motor topologies that can significantly (even multiply) increase the power density of motors and improve their performance, providing an excellent power source for industries that are sensitive to motor size and weight (such as industrial robots, new energy vehicles, aerospace, new energy power generation, servo systems, etc.). At the same time, it also provides a good means for energy conservation and consumption reduction in the motor industry. The research results have been successfully applied to high-precision fields such as 3C processing, robotics, aerospace, and military industry.
Taking the robotics industry, where AC servo motors are widely used, as an example, the current pace of industrial restructuring and transformation has greatly boosted the demand in China's robotics market and the rapid development of the robotics industry. Data shows that China imported 23,400 robots in 2010, a year-on-year increase of 130%; and 38,000 robots in 2011, a year-on-year increase of 62%. Subsequently, a series of planning policies conducive to the development of the robotics industry, such as industrial transformation and upgrading, and the development of high-end manufacturing equipment and intelligent manufacturing equipment, were introduced during this period, creating an unprecedentedly favorable environment for the development of China's robotics industry. Since each industrial robot typically has multiple degrees of freedom and often requires more than five motors, the research team's findings will have a significant application.
In addition, the packaging, textile, printing, military, automation, electronic information equipment, light industry, food, railway and locomotive and rolling stock industry, and power industry have also shown strong demand for AC servo motors.
For example, in packaging equipment, servo control can increase output per unit time, improve resource utilization, enhance product adaptability, and improve product quality. Therefore, the application scale of AC servo motors in packaging machinery is gradually expanding. In the textile industry, many textile machines such as rapier machines, warp knitting machines, winding machines, embroidery machines, circular knitting machines, flat knitting machines, and rotor spinning machines often use servo motors to complete high-speed, high-frequency reciprocating motion and achieve rapid and smooth reversing during high-speed motion. The characteristics of low current impact and high energy conversion efficiency have led to a gradual expansion of the application of servo motors in the textile industry. With the increasingly widespread application of shaftless (electronic shaft, i.e., using multiple individual servo motors to replace the traditional mechanical transmission chain) transmission technology in printing presses, the printing industry has become a major consumer of servo motors with high requirements. AC servo motors are also widely used in the military field, and can be used in the drive control of moving parts in radar, various artillery, aircraft, tanks, and ships, replacing current manual or hydraulic servo motors, greatly improving system response speed and control accuracy, and significantly enhancing the performance of weapons and equipment. Furthermore, the automation transformation and upgrading of the manufacturing industry in the face of the gradual disappearance of the demographic dividend, as well as the energy-saving trend under the dual pressure of energy shortage and environmental pollution, have made the motor, the main actuator that converts electrical energy into mechanical energy, an important foundation for various industries to achieve automation and green development.
The research team's novel theory of magnetic field-modulated motors has ushered in a new era for permanent magnet motor theory and has already benefited multiple industries. Meanwhile, the enormous demand in these fields indicates the broad prospects of this groundbreaking theory. As theory and practical application continue to spark new ideas, perhaps right now, revolutionary new applications of motors are already in the works.
