This chapter mainly focuses on the composition and classification of the servo system, as well as the stepping, DC, AC, and linear servo systems, and a brief introduction to the detection devices such as gratings, resolvers, and pulse encoders.
2.1 Overview of Servo System
The servo system is an electric drive automatic control system composed of mechanically moving chicken wings, electric motors as the control object, controller as the core, power electronic power conversion device as the actuator, and the guidance of automatic control theory. This type of system controls the torque, speed and angle of the motor, converts electrical energy into mechanical energy, and realizes the motion requirements of the sports machinery. Specifically in CNC machine tools, the servo system receives the displacement and speed commands issued by the CNC system. After being transformed, amplified and connected to Jinzhong City, the motor and mechanical transmission mechanism drive the machine tool coordinate axes, spindles, etc., drive the workbench and the tool post, and pass The combined transportation of the axis makes the tool produce various complicated mechanical movements relative to the workpiece, thereby processing the workpiece with the complex switch required by the user.
As the actuator of CNC machine tools, the servo system integrates power electronics, control, chicken wings and protection. With the advancement of digital pulse width modulation technology, special motor material technology, microelectronic technology and modern control technology, it has experienced Stepping to DC, into the development process of AC. There are many types of servo systems in CNC machining tools. This chapter briefly introduces its technical status by analyzing its structure and simple classification.
From the basic structure, the servo system is mainly composed of four parts: the controller, the power drive device, the feedback device and the motor. The controller adjusts the control quantity according to the difference between the given value of the numerical control system and the actual operating value detected by the feedback device; As the main circuit of the system, the power drive device, on the one hand, converts the electric energy in the power grid into the swimming power or direct current required by the motor according to the magnitude of the control amount; the motor drives the machinery to operate according to the power supply.
The main components of the structure of the servo system vary, and any part of the changes can constitute different types of servo systems, such as according to the type of driving motor, or divided into DC servo and AC servo; according to the different implementation methods of the controller, It can be divided into simulation and numerical control servo; according to the number of closed loops in the device, it can be divided into open loop cnc numerical control system, single loop control system, and double loop control system.