Permanent magnet brushless motors are a general term encompassing permanent magnet brushless DC motors, permanent magnet brushless AC synchronous motors, permanent magnet brushless linear motors, and permanent magnet brushless torque motors. Permanent magnet brushless motors possess numerous advantages, making them the mainstream technology in the development of micro-motors. Reasons for the rapid development of permanent magnet brushless motors: 1. Technological advancements drive the development of permanent magnet brushless motors. Looking towards the 21st century, micro-motors, designed to coexist with the Earth's environment, integrate with networks, and meet the requirements of robotics, will experience rapid development, ushering in a "new era for micro-motors." Coexistence with the Earth's environment requires motors that are highly efficient and energy-saving, high-output, material-saving, quiet and comfortable, and harmless and pollution-free. Integration with networks requires miniaturization, flatness, high speed, lightweight, high precision, and high performance. Meeting the requirements for robotic motors demands high output, low inertia, low-speed high torque, and intelligence. To meet these requirements, foreign micro-motor manufacturers place great emphasis on the research and development of permanent magnet brushless motors and drive control technologies. The motor is optimized and parameters are reasonably selected to reduce torque pulsation and noise and expand the speed range; multi-pole concentrated winding reduces the winding end length, and the block or hinged armature lamination improves the slot fill factor. The research on high-efficiency and high-performance drive control technology and the adoption of high-performance permanent magnet materials make permanent magnet brushless motors have the advantages of high efficiency and energy saving, high output and material saving, high reliability and high performance, small size and light weight. 2. Market pull accelerates the development of permanent magnet brushless motors (1) The number of micro motors used in the network field accounts for about 38% of the total number of micro motors. HDD spindle motors, printer spindle motors, copier spindle motors, computer fans and high-end DVD spindle motors all use permanent magnet brushless motors. Moreover, they are precision permanent magnet brushless motors. Due to the high precision requirements, they all use bonded neodymium iron boron. 83% of the bonded neodymium iron boron in Japan is used in this type of permanent magnet brushless motor; whole armature lamination, multi-pole concentrated winding, external rotor structure. The vibration motors used in mobile phones, whether cylindrical or button-type, are mostly brushed DC motors, but there are also brushless vibration motors, which are not widely used at present. (2) Motors used in the home appliance field account for about 15% of the entire micro motor. Air conditioners, washing machines, refrigerators and other major home appliances initially used single-phase asynchronous motors. Due to their low efficiency and low utilization rate, in order to save energy, variable frequency speed control asynchronous motors were adopted in the early 1990s. At present, more than 90% of air conditioners in Japan use permanent magnet brushless DC motors to replace the variable frequency speed control of asynchronous motors. Air conditioner manufacturers in my country have also begun to use permanent magnet brushless DC motors to obtain better energy-saving effects and save materials. Under the same rated power and rated speed, if the volume and weight of the single-phase asynchronous motor are 100%, then the volume of the permanent magnet brushless DC motor is 38%, the weight is 34.8%, the copper content is 20.9%, the iron content is 36.5%, and the efficiency is increased by more than 10%. In order to maximize efficiency, the permanent magnet of the motor is made of sintered neodymium iron boron, the armature lamination is made of block type or hinge type, and the multi-pole concentrated winding is used. According to the user's requirements, the motor can be made into an external rotor or internal rotor structure. The trend is that more and more household appliances, such as air conditioners, washing machines, and refrigerators, will adopt permanent magnet brushless motors. (3) In the field of electric vehicles, my country produced 6.7571 million electric bicycles in 2004, an increase of 69.05% year-on-year. Most of them used brushed DC motors. However, due to the inherent disadvantages of brushed DC motors, such as short life and difficult maintenance, as the price of permanent magnet brushless DC motors decreases and the reliability of controllers improves, more and more permanent magnet brushless motors are being used. With energy shortages and increasing environmental pollution, electric vehicles (EVs) are showing strong vitality and are favored by both automakers and consumers. Data shows that by 2010, EVs will account for a quarter of global car demand, reaching a total of 20 million vehicles. Major automakers such as General Motors (USA), Toyota (Japan), and Citroën (France) have all made EVs a development direction. my country also attaches great importance to EVs, listing them as a major national research project during the "10th Five-Year Plan" period and a key component of the "11th Five-Year Plan" for developing green transportation. EV drive motors include brushed DC motors, variable frequency asynchronous motors, and permanent magnet brushless motors, but the trend is towards permanent magnet brushless motors, especially among Japanese automakers. The drive motors in electric power steering systems also include brushed DC motors and permanent magnet brushless motors, but the trend is again towards permanent magnet brushless motors. It will be a trend for permanent magnet brushless motors to replace brushed DC motors in all safety-related systems in electric vehicles. The permanent magnets in these motors use sintered neodymium iron boron, and the winding forms include concentrated windings and distributed windings. The motor structures include external rotors and internal rotors. As for the general motors used in automobiles, brushed DC motors are still the main type. Micro motors used in automatic cars account for about 17% of the total micro motors. (4) After the elevator adopts the permanent magnet brushless synchronous motor servo control system, it not only has small size, energy saving, and good control performance, but also makes it easy to realize direct drive to eliminate gear reduction devices. The low noise, leveling accuracy and comfort are better than the previous brushed DC motor speed regulation and asynchronous motor frequency conversion speed regulation. It is suitable for use in machine room-less elevators. Therefore, permanent magnet brushless synchronous motor drive has been favored by major elevator companies. (5) The feed drive of high-speed and high-precision machining tools is currently mainly based on the traditional rotary servo motor plus precision high-speed ball screw structure. Since the early 1990s, linear motor direct drive has been applied. Compared with the traditional structure, it has a series of advantages, with a speed increase of 30 times, an acceleration increase of 10 times, a maximum of 10g, and a stiffness increase of 7 times. Of course, there are also some disadvantages and problems with linear motor direct drive, such as high control difficulty, magnetic interference, and high cost. However, the general trend is that the proportion of linear motor drive will become larger and larger, and it is very likely to become the main body of machine tool feed drive in the future. Due to its high efficiency, high thrust density, and good controllability, permanent magnet brushless synchronous linear servo motors have become the mainstream linear motors for machine tools, despite their high requirements for magnetic shielding and dust prevention and the difficulty of assembly. (6) Other fields include micro motors for armed equipment, robots, and aerospace. These application fields use various types of motors with a wide variety of specifications. For example, the US military has more than 5,000 types of micro motors, with an annual production of only 3 million units. With the development of robotics and aerospace, the demand for micro motors will increase, and the requirements will also be raised. Servo drive motors in these fields are also developing towards permanent magnet brushless motors. For example, Kollmorgen, a key company in the United States that researches and produces micromotors for military and aerospace use, has two series of permanent magnet AC servo motors. The M series has 5 frame sizes and 47 models, with power ranging from 0.54 to 15.7 kW, speed from 900 to 1200 r/min, continuous torque from 0.89 to 115 N·m, and peak torque from 2.41 to 326.8 N·m. The MT series has 4 frame sizes and 24 models, with power ranging from 0.231 to 6.7 kW, speed from 1500 to 6000 r/min, continuous torque from 0.44 to 46.8 N·m, and peak torque from 1.25 to 115.4 N·m. The MT series products are smaller, more efficient, and have lower moment of inertia than the M series products. Their rotatable connectors further improve the speed, miniaturization, reliability, and maintainability of weaponry, meeting the requirements of weaponry servo control systems. They are widely used in radar, aerospace, and other fields. The United States has already used permanent magnet brushless motors as drive sources in armored vehicles, replacing brushed DC motors and improving vehicle performance. Motors with a rated power of 3820kW, a rated voltage of 2800V, and a rated speed of 135r/min, produced by Siemens (Germany) and ABB (Finland), are used in podded propulsion systems of luxury cruise ships, icebreakers, and engineering vessels. They are now being promoted for submarines, replacing brushed DC motors and improving submarine performance. 3. Technological advancements in related industries have provided the foundation for the development of permanent magnet brushless motors. Permanent magnet brushless motors are products integrating new permanent magnet materials, power electronics, integrated circuits, computer technology, and motor technology. Technological development in related industries is the foundation for the development of permanent magnet brushless motors. The emergence and rapid development of neodymium iron boron (NdFeB) rare-earth permanent magnet materials in the early 1980s provided permanent magnets with high remanence, high coercivity, and high energy product for permanent magnet brushless motors. Its shortcomings, such as large temperature coefficient, low Curie point, and susceptibility to oxidation and rust, have been continuously improved. Currently, the highest operating temperature of NdFeB permanent magnet materials can reach 180℃, and it can generally reach 150℃. The oxidation and rust problems are solved through coating treatment. Most permanent magnet brushless motors use bonded or sintered NdFeB. Global production of NdFeB permanent magnet materials reached 23,000 tons in 2005, with my country producing 14,000 tons. It is projected that global production will reach 90,000 tons in 2010, with my country producing 50,000 tons. With the continuous upgrading of power electronics technology and products, the performance of semiconductor switching devices is constantly improving, their capacity is increasing, and their cost is decreasing. The rapid development of large-scale integrated circuits and computer technology has led to the emergence of many dedicated integrated circuits for motors. In recent years, high-performance, low-cost digital signal processors (DSPs) specifically designed for motor control have emerged. The rapid development of integrated circuits and computer technology has played a powerful role in promoting the control technology of permanent magnet brushless motors, providing a foundation for the development of permanent magnet brushless motors. II. my country should attach importance to the research, development and industrialization of permanent magnet brushless motors. (1) After my country's reform and opening up, its economy has developed rapidly. However, it is a high-consumption, extensive economic development. my country has proposed the goal of reducing energy consumption per unit of GDP by about 20% by the end of the "Eleventh Five-Year Plan" period. It has also proposed building a conservation-oriented society. The National Development and Reform Commission has included permanent magnet motors as an energy-saving promotion product in its medium-term energy conservation plan, because about 60% of electricity is consumed in motors. Therefore, we should actively accelerate the research, development and industrialization of various types of permanent magnet brushless motors. (2) my country is a major country in the reserves of rare earth materials. We should strengthen the application research of rare earth permanent magnet materials and improve the performance of rare earth materials. (3) In addition to the advantage of abundant rare earth permanent magnet materials, my country also has talent resources in permanent magnet brushless motors. The government should formulate corresponding preferential policies to realize the integration of industry, academia and research under the government's promotion, give full play to the advantages of talents in all aspects, carry out joint development and joint research, realize industrialization, and create various permanent magnet brushless motor brands with independent intellectual property rights. (4) Most of the precision permanent magnet AC servo drive control systems used in my country are imported. According to incomplete statistics, the import cost is about US$200 million per year. We have a responsibility to quickly realize the industrialization of various permanent magnet brushless motors, form real commodities, replace imports, change the situation of dependence on imports, and make my country not only a major producer of micro motors, but also a technological powerhouse in micro motors.