With the development of information, communication and automation technology, a wide variety of automatic control devices have gradually entered People's Daily life. Network communication technology not only provides a convenient means of communication for people, but also provides a simple and reliable communication channel for all kinds of electronic devices. With the help of new network communication technology and digital signal processor chip (DSP) with powerful computing function, a variety of information home appliances with basic intelligence can be developed. Examples include robots that can help with cleaning, electronic pets for entertainment, and so on. The core part of these integrated mechanical, electronic, communication, control and information technology devices is the servo system controller with a network interface. Servo technology has been widely used in our daily life, such as the servo control of optical reader head of optical disc drive, the wing control of remote control aircraft, the automatic focus control of digital camera, the network camera monitoring system with image tracking function, the auto driving and so on, the servo system covers a wide range, multi-disciplinary cross color.
Servo system - Key technology of mechatronics
The term "servomechanism system" is derived from the Servomechanism system and refers to a system in which the position, speed, or acceleration of a mechanical system is controlled by means of closed-loop control. A servo system usually consists of several parts, such as the plant, the driver, and the controller, and the controlled object refers to the controlled object, such as a mechanical arm or a mechanical working platform. The function of the driver is to mainly provide the power of the controlled object, which may be presented in the way of pneumatic, hydraulic, or electric drive, if the hydraulic drive is used, it is generally called a hydraulic servo system. At present, most servo systems use electric drive, the driver contains the motor and power amplifier, the motor specially designed for the servo system is called servo motor (servo motor), which usually contains a position feedback device. Such as optical encoder (optical encoder) or rotary transformer (resolver), the servo motors mainly used in the industry include DC servo motors, permanent magnet AC servo motors and induction AC servo motors, of which permanent magnet AC servo motors account for the majority. The function of the controller is to provide closed-loop control of the whole servo system, such as torque control, speed control and position control. At present, the general industrial servo drive (servo drive) usually includes a controller and a power amplifier.
The composition of a traditional servo system is shown in Figure 1, the servo driver mainly includes power amplifier and servo controller, servo controller usually includes speed controller and torque controller, motor usually provides analog speed feedback signal, control interface adopts ±10V analog signal, through the analog command of the external loop, can directly control the speed or torque of the motor. With this kind of servo drive, it is usually necessary to add a position controller to complete the position control. Figure 2 shows the structure of a modern servo system, where the servo driver contains the servo controller and power amplifier, and the servo motor provides high-resolution photoelectric encoder feedback signals.
Multi-axis motion control system
Precision servo system is widely used in multi-axis motion control systems, such as industrial robots, CNC machine tools, electronic parts assembly systems, PCB automatic insertion machines and so on. Figure 3 shows a block diagram of a motion control platform, the position control of the working object can be realized through the movement of the platform. There are two ways to detect the position of the platform, one is the photoelectric encoder installed by the servo motor itself, because the position of the working object is fed back indirectly, and the purpose of position control is achieved through closed-loop control. Therefore, it is also called indirect position control. Another way is to directly install the position sensing component on the platform, such as optical ruler, laser position detector, etc., directly feedback the position of the working object, and then achieve the purpose of position control through closed-loop control, called direct position control.
