[Abstract] Mechatronic micromotors are high-tech products formed by the integration of multiple technologies, involving many modern scientific fields. This paper introduces the current development status and prospects of mechatronic micromotors, and illustrates their applications in the industrial field with examples. 【Keywords】mechatronics, micromotor, status, application, development 1 Introduction With the continuous application of electronic technology, especially microelectronics, computer technology, new material technology, automatic control technology and bioengineering technology in micromotors, modern micromotors have developed into a new generation of servo drive systems with electronic computers and other microelectronic software and hardware products as the central nervous system, sensors as the eyes and ears, electric motors as the hands and feet, mechanical bodies as the driving force, and power electronic devices as the life source. This is what is commonly referred to as mechatronics[1] micromotors. This article introduces the current development status and prospects of mechatronic micromotors, and illustrates their application in the industrial field with examples. 2. Current Development Status of Mechatronic Micromotors As a crucial component of mechatronic systems, micromotors are the most commonly used drive and actuator elements. Since the 1970s, with the rapid development of large-scale and very large-scale integrated circuits and microcomputers, as well as the widespread application of power electronic devices in micromotors, the spatial integration of motors and mechanical components has become increasingly tight. This allows motors to be combined with power supplies, drive systems, and control systems, greatly improving the overall performance and efficiency of the system. Traditional induction motors have expanded their application areas, and AC speed control systems are replacing DC speed control systems in many aspects. In the late 1970s, permanent magnet AC servo motors were successfully developed abroad, and their high efficiency, small size, light weight, and good operating performance have led to their rapid promotion and application in CNC machine tools and industrial robots. Professor BK Bose of the National Power Electronics Applications Center (PEAC) in the United States calls this brushless motor, made with permanent magnet materials, an advanced motor. Its speed ratio can be precisely controlled to the level of 1 ÷ 100,000. These precision speed control systems employ new power electronic devices such as IGBTs and MCTs, along with digital signal processors (DSPs), and expert systems for software. Currently, DC servo motor drive systems have been largely phased out in some high-precision CNC machine tools and machining centers abroad. Switched reluctance motors have also seen rapid development in recent years. These are stepless speed control systems powered by electronic controllers, possessing excellent speed control performance comparable to DC motor speed control systems. They are a typical mechatronics product and have been widely adopted in many industrial and household appliance sectors. Switched reluctance motors (SRMs) have a simpler structure than DC motors, and even simpler than squirrel-cage motors. They lack commutators and brushes, and have no windings on the rotor core. They have the potential to compete with squirrel-cage motors in the low-to-medium power range and capture a portion of the market. This trend has attracted attention in Europe and America. Integrating control and protection circuits directly into the motor, making the control circuit and motor a single unit, is not uncommon. The micro-motor developed in the early 1980s is a typical example. This type of motor lacks commutators and brushes; instead, it uses Hall effect sensors to detect rotor position and a frequency generator (FG) to detect rotor speed within the gaps in the coils. This eliminates the need for a separate tachogenerator structure and includes electronic circuitry for controlling armature current and receiving and processing signals. Figure 1 shows the drive circuit diagram of this type of brushless micro-motor, which basically consists of two parts: one is the speed control circuit based on the speed signal obtained from the frequency generator (FG), i.e., the torque feedback circuit generated by the armature current. Second, there is a phase control circuit that processes the rotor position signal obtained from the Hall element and appropriately distributes the armature current. Chip micromotors are currently widely used in the OA, FA, HA, and FDD markets. Mechatronics technology has greatly expanded the application areas and accelerated the pace of upgrades for micromotors. [align=center] Figure 1 Chip brushless motor drive circuit[/align] 3 Development Prospects of Mechatronic Micromotors 3.1 Ultramicromotors Ultramicromotors refer to mechatronic transmission devices that are extremely small (less than 1mm), lightweight, and manufactured on the same substrate (silicon or other materials) using microelectronics and microfabrication technologies. Ultramicromotors fall under the research scope of Micro-Electro-Mechanical Systems (MEMS). Their development benefited from the so-called sacrificial layer technology developed by Roger Howe of the Bakurei Institute at the University of California in 1983. This technology not only makes it easier to manufacture micro-components on silicon wafers but also allows them to be directly assembled onto the substrate to form a whole. In July 1988, researchers at the University of California fabricated an ultramicro motor with a thickness of only 1–1.5 μm and a diameter of 100 μm. The entire motor was designed on an integrated circuit chip, driven by electrostatic force, and made of silicon phosphate. Several institutions in my country are currently conducting research on this technology. Southeast University was the first to begin research, but the first motor to actually operate was the electrostatic synchronous motor reported three years ago by Sun Xiqing et al. of Tsinghua University. This motor had a rotor diameter of 120 μm and a speed of 1200 rpm, monitored online using photoelectric devices on the chip. The ultramicro electrostatic motor developed by the Shanghai Institute of Metallurgy, Chinese Academy of Sciences, has a rotor diameter of 100 μm, a continuously adjustable speed within 0.001–20 rpm, and is driven by radial force with a minimum driving voltage of 20V. It exhibits a larger output torque than the earlier reported tangential force-driven electrostatic motors. These advancements demonstrate that my country has achieved a certain level of international advancement in the research and development of ultramicro motors. Surface micromachining technology is a key technology for manufacturing micromotors. It involves using specific devices and structural components as sacrificial layers during the manufacturing process, and then obtaining movable and rotatable micro-mechanical structures through photolithography of the sacrificial layers. In the manufacturing process of micromotors, polycrystalline silicon is typically used as the structural material, silicon nitride thin film as the electrical insulation material, and SiO2 as the sacrificial material. Figure 2 shows a schematic diagram of a micro-electrostatic motor manufactured using polycrystalline silicon as the structural substrate and photolithography. [align=center]Figure 2 Structural diagram of a micro-electrostatic motor[/align] The application prospects of micromotors are very broad, especially in micro-environments that are not yet fully understood, and there is much room for further development. Micromachines made using micromachining technology can enter the human body to explore lesions and perform surgery; micromotors can be used to cool the surface temperature of computer chips and correct laser beams and optical fibers; microrobots can travel to planets for exploration and enter areas of submarines inaccessible to humans to troubleshoot problems, etc. 3.2 Flagellar Motor A flagellar motor is a molecular machine (a machine formed of protein molecules) used by bacteria to move in water. It is the only rotating electric motor in the biological world and also the smallest electric motor currently existing (50 nm in diameter). According to foreign research, flagella are produced in bacterial cells several μm in size (depending on the type of bacteria, several flagella can be produced). Flagella are helical, slender fibers, with lengths generally ranging from several μm to 10 μm and diameters of only about 20 nm. Figure 3 shows a model of a flagellar motor, composed of about 10 types of proteins. The motor is enclosed within a membrane, and the rotation is driven by the proteins in each component. For example, it can be inferred that the L-ring and P-ring complex acts as a bearing, and the Mott complex acts as a stator. The energy of the flagellar motor is supplied by the ion flow from the outside to the inside of the cell. [align=center]Figure 3 Flagellar motor model[/align] 4 Examples of mechatronic micro-motor applications 4.1 Industrial sewing machine drive system Starting in the 1980s, foreign countries began to study AC servo motor drive systems for industrial sewing machines. Japanese companies such as JUKI, Brother, Mitsubishi, and Panasonic successively applied AC servo motors to various industrial sewing machines, realizing the electronicization of industrial sewing machines. Typically, the motor and control device used in industrial sewing machine drives are integrated. Figure 4 shows an AC servo drive system produced by Mitsubishi. The operator issues speed commands through the pedal operation on the lever section, changing the frequency and voltage of the motor to obtain the required motor speed, thereby driving the sewing machine. The encoder and current detector in the control loop continuously feed back the motor speed and current, and use this for vector control. To stop the operation, the motor must decelerate. The position loop is controlled based on the received position detector signal and the signal on the encoder, thus stopping the sewing machine needle in the normal position. Figure 5 shows another AC servo drive system manufactured by Panasonic. The system is characterized by a simplified and miniaturized power control circuit, as well as a smaller, lighter, and microcontroller-based control power supply. The microcomputer used for control is a high-speed dual-mode microcomputer MN 18982 (manufactured by Panasonic Electronics Industry, 8-bit, 8K ROM) with two built-in CPUs. The difference between the two drive systems is that the former uses an IM (induction motor) servo method, while the latter uses an SM (synchronous motor) servo method. [align=center] Figure 4 IM-type AC servo drive system Figure 5 SM-type AC servo drive system[/align] 4.2 Electric spindle control system In recent years, a new type of control system has emerged abroad: an electric spindle (magnetic bearing high-speed spindle component) that uses a magnetic shaft pump (linear suspension motor) to control the spindle position accuracy. It uses modern electronic adjustment technology to maintain high rotational accuracy of the rotor (spindle), possessing high static and dynamic stiffness and electrical attenuation characteristics. This overcomes the problems of sintering and damage that occur when rolling bearings exceed a certain speed limit (20,000 rpm), with speeds reaching 25,000–120,000 rpm. Currently, a certain number of high-speed cutting machine tools abroad are equipped with such electric spindle control systems. [align=center] Figure 6 Block diagram of grinding machine and magnetic bearing control system[/align] Figure 6 shows the block diagram of the magnetic shaft pump control system developed by Nippon Seiki for use on an internal grinding machine. No matter which direction the rotor approaches the stator, the current in the electromagnet on the side with the larger gap increases, thus generating a pulling action on the rotor. The displacement sensor signal can be continuously compared with the reference signal to detect the displacement amount deviating from the equilibrium position. The control system operates in a manner where this displacement amount is zero. 5 Conclusion AC servo drive systems are high-performance mechatronic products with great development potential. From the current development perspective of the machine tool industry, the mainstream is still CNC machine tools. The servo system is the execution part of the CNC system, and its performance directly affects the machining accuracy and productivity of CNC machine tools. Therefore, developing high-quality AC servo drive motors is a goal that needs to be pursued in the future. The future development of mechatronic micromotors will focus on integration and optimization to form so-called intelligent motors. The rise of micromechanical technology is a development direction worth paying attention to. People expect to use this new technology to continuously develop complex actuators and even micro-robots. Although research on flagellated motors is still ongoing, it indicates that mechatronic micromotors will lead people into a new application field in the future development of mechatronic micromotors—the microscopic world. It also marks the beginning of the molecular era for mechatronic micromotors. References 1 Mao Kan. On Mechatronics. Mechatronics, 1994 (3) 2 Wan Yuliang. Electrical Engineering Technology and Mechatronics. Collection of Papers on the Development of Contemporary Electrical Engineering Technology, China Electrotechnical Society, Beijing: 1995 (4) 3 Tang Suya. Overview of the Development of Chip Micromotors. Micromotors, 1993 (4) 4 Tang Suya. Research Dynamics and Application Prospects of Micromechanical Systems. Micromotors, 1995 (4) 5 M. neh regary. ¾„ Í Â - Ÿ Technology I to IV Current Status and Topic I. Mechanical Design, 1991 (14) 6 Tang Suya. 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