Digital control system

- Jul 18, 2018 -

The numerical control system consists of an information carrier, a numerical control device, a servo system and a controlled device. The information carrier uses paper tape, magnetic tape, magnetic card or magnetic disk to store processing information such as processing parameters, motion sequence, stroke and speed. The numerical control device, also known as an interpolator, sends a pulse sequence based on the input machining information. Each pulse represents a displacement increment. The interpolator is actually a dedicated computer with a simple function, or it can be directly used as a microcomputer. The incremental pulses output by the interpolator act on the corresponding drive mechanism or system to control the movement of the table or tool. If a stepper motor is used as the drive mechanism, the numerical control system is open loop control. For precision machine tools, closed-loop control is required, and the servo system is used as the drive system.

The digital control system is composed of a computer, an external device, an operation console, an input channel, an output channel, a detection device, an actuator, a controlled object, and corresponding software.


The computer is the core of the digital control system. Through the interface, various control commands can be issued to various parts of the system, and the controlled parameters of the controlled object can be detected and processed in real time. Its function is to complete program storage, numerical calculation, logic judgment, and data processing.

2. Process input and output channels

The process input and output channels are connection channels for information transfer and conversion set between the computer and the controlled object. The input channel converts the controlled parameters of the controlled object into digital codes that the computer can recognize, which generally requires three steps of sampling, quantization, and encoding. The output channel converts the control commands and data output by the computer into control signals that can control the controlled object. The input and output channels generally include: an analog input channel, an analog output channel, a digital input channel, and a digital output channel.

3. External equipment

An external device is a device that exchanges information between a computer and the outside world, referred to as a peripheral device. External devices include human-machine communication devices, input and output devices, and external memory.

Input devices: keyboards, scanners, optoelectronic input devices, etc., used to enter programs and data.

Output devices: printers, recorders, monitors, etc., mainly used to provide information and data to operators to keep abreast of the control process.

External storage: Includes tapes, disks, etc. to store system programs and data.

4. Detection device

In order to control the controlled object, it is necessary to first collect data on the controlled parameters of the controlled object, such as temperature, pressure, liquid level, speed, etc., which is performed by the detecting device, and the detecting device is a sensor, which can be non- The power parameter is converted into a power parameter and sent to the computer.

5. Execution agency

The actuator is an important part of the computer control system, it is the executor of the control task, such as the motor.

6. Console

The console is a device for dialogue between the operator and the computer control system, and mainly includes:

(1) Display device: display screen, fluorescent digital display, display content and alarm signal requested by the operator.

(2) Function keys: reset button, start button, print button, display button, interrupt button.

(3) Number keys: Enter some data or modify some parameters of the control system.

7. Software

Software is a program that can perform various functions of a computer control system. It is the central nervous system of computer control systems. Under the command of the software, the entire system is coordinated. The software includes system software and application software.

1. System software. It is a general term for improving the efficiency of computer use, expanding functions, and providing convenient programs for users to use, maintain, and manage computers. The system software includes an operating system, a language processing system, and a diagnostic system, which have certain versatility and are generally provided by computer manufacturers along with the hardware.

2. Application software. Various programs written by the user based on the actual problem to be solved. In a computer control system, it refers to a program that performs various tasks of the system. Examples include control programs, data acquisition and processing programs, and polling and alarm programs.