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1. DC servo technology The development of servo systems has progressed from hydraulic to electrical systems. Electrical servo systems are divided into DC servo systems and AC servo systems based on the type of motor they drive. In the 1950s, brushless motors and DC motors were put into commercial use and found wide application in computer peripherals and mechanical equipment. The 1970s was the era when DC servo motors were most widely used. 2. AC servo technology: From the late 1970s to the early 1980s, with the development of microprocessor technology, high-power and high-performance semiconductor power device technology, as well as manufacturing processes for motor permanent magnet materials, and the continuous improvement in their performance-to-cost ratio, AC servo technology – including AC servo motors and AC servo control systems – gradually became the dominant products. AC servo drive technology has become one of the fundamental technologies for achieving automation in the industrial sector, and it will gradually replace DC servo systems. Based on the type of drive motor used, AC servo systems can be divided into two main categories: permanent magnet synchronous (SM type) motor AC servo systems and induction asynchronous (IM type) motor AC servo systems. Among them, the AC servo system based on permanent magnet synchronous motors has reached a high level of technical maturity; it features excellent low-speed performance and is capable of weak-field high-speed control, which broadens the system’s speed regulation range and meets the requirements of high-performance servo drives. Furthermore, as the performance of permanent magnet materials improves significantly and their prices decrease, their use in the field of industrial production automation will become increasingly widespread; they have now become the mainstream in AC servo systems. The AC servo system using induction asynchronous motors has excellent development prospects due to the robust structure, ease of manufacturing, and low cost of these motors; it represents the future direction of servo technology. However, since this system uses vector transformation control, its operation is more complex compared to permanent magnet synchronous motor servo systems. Moreover, technical issues such as low efficiency and severe heating when the motor operates at low speeds need to be addressed, which is why it has not been widely adopted to date. The actuating elements of the system are generally ordinary three-phase squirrel-cage asynchronous motors, while the power conversion devices typically use intelligent power modules IPM. To further improve the dynamic and static performance of the system, position and velocity closed-loop control can be employed. Follow-up control of three-phase AC current can effectively improve the current response speed of the inverter and limit transient currents, thereby facilitating the safe operation of the IPM. The speed loop and position loop can be controlled using a microcontroller to enable the control strategy to achieve higher control performance. If the current regulator is of proportional type, all three AC current loops are controlled using proportionally large regulators; the proportional gain should be set as high as possible without causing oscillations in the system. This allows the amplitudes, phases, and frequencies of the three-phase AC currents of the driven asynchronous motor to change rapidly in response to the set values, thereby enabling fast current control in voltage-source inverters. Current is regulated proportionally, offering many advantages such as a simple structure, good current follow-up performance, and the ability to limit the starting and braking currents of the motor in a fast and reliable manner. 3. Comparison of AC and DC servo technologies: DC servo drive technology is constrained in its development due to the limitations of the motors themselves. DC servo motors have disadvantages such as a complex mechanical structure and high maintenance requirements; their rotors tend to overheat during operation, which affects the precision of other mechanical devices connected to them. As a result, they are difficult to use in high-speed or high-capacity applications, and mechanical commutators have become a bottleneck in the development of DC servo drive technology. AC servo motors overcome the various disadvantages associated with mechanical components such as brushes and commutators found in DC servo motors. In particular, the overload capacity and low inertia of AC servo motors further highlight the advantages of AC servo systems. Therefore, AC servo systems are widely used in various fields such as factory automation (FA). Looking at the current applications of servo drive products, DC servo products are gradually decreasing, while AC servo products are on the rise, with their market share expanding steadily. In practical applications, AC servo products that offer higher precision, faster speed, and greater ease of use have become the mainstream products.