The characteristics of servo systems have always been a crucial indicator affecting system machining performance. In recent years, various servo drive technologies have been developed to improve the dynamic and static characteristics of servo systems. It is foreseeable that with the development of advanced manufacturing technologies such as ultra-high-speed cutting, ultra-precision machining, and networked manufacturing, fully digital servo systems with network interfaces, linear motors, and high-speed electric spindles will become hot topics in the CNC machine tool industry and represent the future direction of servo system development.
1. Communication
Servo technology will continue its rapid shift from DC servo systems to AC servo systems. Currently, almost all new products in the international market are AC servo systems. In industrialized countries, the market share of AC servo motors has exceeded 80%. The number of domestic manufacturers producing AC servo motors is also increasing, gradually surpassing the number of manufacturers producing DC servo motors. It is foreseeable that in the near future, except in certain micro-motor applications, AC servo motors will completely replace DC servo motors.
2. Fully digital
Servo control units employing new high-speed microprocessors and dedicated digital signal processors (DSPs) will completely replace those based primarily on analog electronic devices, thus realizing a fully digital servo system. This full digitalization transforms traditional hardware servo control into software servo control, making it possible to apply advanced algorithms from modern control theory (such as optimal control, artificial intelligence, fuzzy control, and neural networks) within the servo system.
3. Employing novel power electronic semiconductor devices
Currently, servo control systems primarily utilize high-frequency power semiconductor devices for their output, including high-power transistors (GTRs), power MOSFETs, and insulated-gate transistors (IGBTs). The application of these advanced devices significantly reduces power consumption in the servo unit's output circuit, improves system response speed, and reduces operating noise. In particular, the latest servo control systems are beginning to use a new type of module that integrates control circuit functions with high-power electronic switching devices, called the Intelligent Power Module (IPM). This device integrates input isolation, energy-saving braking, over-temperature, over-voltage, and over-current protection, as well as fault diagnosis, all within a small module. Its input logic level is fully compatible with TTL signals and can directly interface with microprocessor outputs. Its application significantly simplifies servo unit design and enables the miniaturization and micro-miniaturization of servo systems.
4. High integration
The new servo system products have changed the traditional approach of dividing servo systems into two modules: a speed servo unit and a position servo unit. Instead, they utilize a single, highly integrated, and multifunctional control unit. The performance of this single control unit can be altered simply by setting system parameters through software. It can be used to construct a semi-closed-loop control system using the motor's built-in sensors, or it can be integrated with external position, speed, or torque sensors to form a high-precision fully closed-loop control system. This high level of integration also significantly reduces the overall size of the control system, simplifying installation and commissioning.
5. Intelligentization
Intelligentization is the current trend in all industrial control equipment, and servo drive systems, as advanced industrial control devices, are no exception. The latest digital servo control units are typically designed as intelligent products, and their intelligent features are manifested in:
(1) All have parameter memory function. All operating parameters of the system can be set by software through human-computer dialogue and stored inside the servo unit. Through the communication interface, these parameters can even be modified by the host computer during operation, which is convenient to use.
(2) Both have fault self-diagnosis and analysis functions. Whenever a fault occurs in the system, the fault type and possible causes will be clearly displayed through the user interface, which simplifies the complexity of maintenance and debugging.
(3) Some servo systems also have parameter self-tuning capabilities. As we all know, parameter tuning of a closed-loop control system is a crucial step in ensuring system performance, and it also requires a significant amount of time and effort. Servo units with self-tuning capabilities can automatically tune the system parameters and achieve optimal performance through several trial runs. For users of servo units, this is one of the most attractive features of new servo systems.
6. Modularization and networking
Abroad, factory automation (FA) engineering technology based on industrial local area network (LAN) technology has developed rapidly over the past decade, showing a strong growth momentum. To adapt to this trend, the latest servo systems are equipped with standard serial communication interfaces (such as RS-232C or RS-422 interfaces) and dedicated LAN interfaces. These interfaces significantly enhance the interconnectivity between servo units and other control devices, thus simplifying connections to CNC systems. Several, or even dozens, of servo units can be connected to a host computer to form an entire CNC system with just a single cable or fiber optic cable. They can also be connected to the CNC modules of programmable logic controllers (PLCs) via serial interfaces.
