2.2.2 Single microprocessor architecture system
The numerical control system with single microprocessor structure is composed of microprocessor, bus, memory, I/O interface, MDI interface, CRT or LCD display interface, PLC interface, feed control, spindle control, paper tape reader interface, communication interface, etc.
Table 2-4 describes the basic functional modules of the single microprocessor structure in detail
Serial number | Basic function module | Detailed description |
1 | microprocessor | The microprocessor CPU is the core of the CNC device, which is mainly composed of the arithmetic unit and the controller. The arithmetic unit includes arithmetic and logic operations, registers, stacks and other components to perform arithmetic and logic operations on data. The controller takes out the instructions that compose the program from the memory in turn, and after decoding, sends out the control signals to execute the operation to all parts of the CNC device in order, so that the instructions can be executed. At the same time, the controller receives the feedback information from the executive part, and decides the next command operation according to the command information in the program and the feedback information |
2 | highway | The bus is composed of physical wires with certain signal meaning. According to the physical meaning of the signal, it can be divided into three groups: data bus, address bus and control bus. The data bus is used to transmit data between components. The number of bits of the data bus is equal to the width of the transmitted data, and the two-way transmission is adopted. The address bus transmits the address signal, which is used in combination with the data bus to determine the source or destination of the data transmitted on the data bus. The one-way line transmission is adopted. The control bus transmits some control signals of the management bus, such as the read/write control of data transmission, interrupt reset and various confirmation signals, which are transmitted by one-way line |
3 | storage | Memory is used to store data, parameters, programs, etc. The system control program is stored in the erasable read only memory (EPROM). Even if the system is powered off, the control program will not be lost. The program can only be read by the CPU and cannot be written randomly. If necessary, the EPROM can be erased by ultraviolet light or electricity, and then the monitoring program can be rewritten. The intermediate results of the operation are stored in random access memory (RAM). The data stored in RAM can be read/written randomly, but if appropriate measures are not taken, the stored information will be lost after power failure |
4 | I/O interface | The signal between the CNC device and the machine tool is generally not directly connected, but connected through the/O interface circuit. The main tasks of the interface circuit are as follows: ① Conduct necessary electrical isolation to prevent misoperation caused by interference signal ② Perform level conversion and power amplification |
5 | MDI/CRT interface | MDI manual data input is operated through the keyboard on the NC panel. When a key is scanned and pressed, the data will be sent to the shift register, the attribute and validity of the key will be judged through data processing, and relevant monitoring processing will be carried out. Under the control of CC system, CRT interface realizes character and graphic display on monochrome or color CRT (or LCD), and real-time display of NC code program, parameters, various compensation data, coordinate position, fault information, man-machine conversation programming menu, part graphics and dynamic tool path |
6 | Position control module | The position control module is an important part of the feed servo system. It is the interface module between the CNC device and the servo drive system when realizing the trajectory control. Each feed axis corresponds to a set of position controller. The position controller controls the electric appliance to drive the workbench to move the specified distance at the required speed under the command of the CNC device. Axis control is the most demanding control on CNC machine tools. It not only has strict requirements on the control of the movement and position accuracy of a single axis, but also requires a good cooperation of each moving axis when multi-axis linkage |
7 | Programmable controller | The programmable controller replaces the logic control of the traditional machine tool strong current relay, and uses the logic operation to realize the control of various switching values. The programmable controller receives the relevant signals from the operation panel, the travel switches, sensors, buttons on the machine tool, the relay in the strong current cabinet, the spindle control, and the tool magazine control, and outputs them to control the operation of the corresponding devices after processing. |
8 | communication interface | When the CNC device is used as a device layer and a working layer controller to form a distributed numerical control system (DNC) or flexible manufacturing system, it also needs to carry out digital communication with the superior computer or the direct digital controller DNC |