Abstract: This paper proposes an intelligent processing unit for CNC machine tools based on 89C51/52 single-chip microcomputer. It introduces its working principle and system software and hardware, and designs a new software to eliminate key jitter algorithm. The processing unit exchanges information with the numerical control system through the standard serial port, and has been controlled by the manual operation panel of the three-axis numerical control milling machine, and the software and hardware can work reliably.
1 Introduction
In the CNC machine tool, the manual operation panel is always indispensable. Its characteristics are: 1. Some input quantities are mutually exclusive, no misoperation is allowed, and the mechanical interlocking relationship is used to ensure the requirements; 2. Key on/off Trigger different states with levels instead of triggering different states with edges; 3. Allow multiple states to input simultaneously and reliably respond accordingly; 4. Can make necessary prompts for the current state of the device, such as using signal lights, lighting two Tube or LCD display. Most of the existing designs use the input/output of the manual operation panel as part of the switch I/O, and are controlled by a built-in or external programmable controller (PLC). CNC machine tool manufacturers purchase CNC systems according to the process characteristics of their own machine tools. After secondary development, they form CNC machine tools with different process performance and operation. The majority of the secondary development workload is in the design of switching I/O, and more than 60% of the work is based on process performance and operation design of the manual operation panel [1]. In fact, the input/output of the manual operation panel is only the control signal switching I/O, and its driving capability is very low. It is a special type of CNC machine tool switching I/O. If the input/output of the manual operation panel is not distinguished from other switch I/O of the CNC machine tool, the workload of the secondary development of the numerical control system will be greatly increased. The manual operation panel of the numerical control machine tool cannot be standardized and modularized, and its economy will also be Greatly affected.
This paper proposes an intelligent processing unit for CNC machine tool panel based on 89C51/52 single-chip microcomputer. The processing unit exchanges information with the numerical control system through the standard serial port, which can display the basic state of the CNC machine tool and manually operate it. This work is part of the research work of the National 863 Program "PC Peripheral Complete Digital Machine Tool and Its Key Technologies", which has been used in three-axis CNC milling machines.
2 Working principle
The 89C51/52 microcontroller has on-chip ROM, 16-bit counter and standard serial port [2]. In the 89C51/52 MCU constitutes the intelligent processing unit of the CNC machine tool panel, generally no external expansion ROM and RAM are required. One bit of the I/O port of the MCU corresponds to one input/output quantity. If the I/O port of the MCU is not enough, it can be expanded. The MCU detects the input with a timer interrupt. Once the input level changes, the corresponding new status is sent from the serial port to the CNC system. On the other hand, the numerical control system sends the information to be displayed to the single chip microcomputer through the serial port. Since the serial communication is adopted, the interface between the numerical control system and the panel intelligent processing unit is standard, the information processing of the operation panel basically does not occupy the time of the numerical control system CPU, and the panel intelligent processing unit itself becomes a standardized module. Figure 1 is a schematic diagram of the intelligent processing unit of the CNC milling machine panel. In the figure, the input/output information of the manual operation panel of the CNC milling machine has the following categories:
Figure 1 Schematic diagram of intelligent processing unit of CNC milling machine panel
1) Working mode selection: manual / automatic / homing 2) single step feeding selection 3) continuous feed speed selection 4) feed speed override selection 5) feed coordinate selection 6) spindle motor, pump, electromagnetic clutch brake On/off control, etc. 7) Emergency stop 8) Pause and display 9) Feed coordinate overtravel display 10) Fault display Among them, the selection of working mode, single step feed amount and continuous feed speed, and feed rate override It is selected to switch between different states by using the changeover switch 1 and the changeover switch 2, respectively. The state controlled by the same transfer switch has a mechanical interlock, which can prevent two or more states having an interlocking relationship from being simultaneously turned on due to a misoperation. The remaining input/output quantities in Figure 1 are directly controlled by the I/O port of the microcontroller, ensuring multiple states and reliable input/output at the same time.
3 system software
89C51/52 single-chip CNC machine tool panel intelligent processing unit power-on reset initialization, enter the interrupt working state, allowing timer interrupt and serial interrupt. In the timed interrupt, the input state is detected to be changed, and the changed input state is sent from the serial port to the numerical control system; the numerical control system needs to send the information displayed by the manual operation panel from the serial port to the single chip microcomputer, and the serial interrupt service is provided by the single chip microcomputer. The program is processed accordingly. The block diagram is shown in Figure 2. Figure 2(a) is the main block diagram, Figure 2(b) is the block diagram of the timer interrupt service, and Figure 2(c) is the block diagram of the serial interrupt service. .
Figure 2 block diagram
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