General steps for the design and commissioning of PLC control systems - News - Global IC Trade Starts Here Free Products

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The general steps for designing and debugging the plc control system are shown in the figure.

General steps for designing and debugging PLC control systems
1. Analyze the controlled object and propose control. It is required to analyze the process and working characteristics of the controlled object in detail, understand the cooperation between the controlled object, electricity and liquid, and put forward the control requirements of the controlled object to the PLC control system, and determine the control. Plan, draw up a design task book.
2. Determine the input/output device to determine all the input devices (such as buttons, position switches, transfer switches, and various sensors) and output devices (such as contactors, solenoid valves, etc.) required by the system according to the control requirements of the system. Signal indicators and other actuators, etc.) to determine the input/output devices associated with the PLC to determine the number of I/O points for the PLC.
3. Select PLC
PLC selection includes selection of PLC model, capacity, I/O module, power supply, etc.
4. Assign I/O points and design PLC peripheral hardware lines
1. Assign I/O points to draw the connection diagram or correspondence table of the I/O points of the PLC and the input/output devices. This part can also be performed in step 2.
2. Design the PLC peripheral hardware circuit to draw the electrical circuit diagram of other parts of the system, including the main circuit and the control circuit that has not entered the PLC.
The electrical schematic of the system is composed of the I/O connection diagram of the PLC and the peripheral electrical circuit diagram of the PLC. The hardware electrical circuit of the system has been determined so far.
5. Programming
1. Programming According to the control requirements of the system, the PLC design is designed using appropriate design methods. The program should meet the system control requirements as the main line, and write the programs that realize the various control functions or sub-tasks one by one, and gradually improve the functions specified by the system. In addition to this, the program should usually include the following:
1) Initialization procedure. After the PLC is powered on, some initialization operations are generally required to make necessary preparations for startup to avoid system malfunction. The main contents of the initialization program are: clearing certain data areas, counters, etc., restoring the data required in some data areas, setting or resetting certain relays, displaying some initial states, and so on.
2) Procedures such as detection, fault diagnosis and display. These programs are relatively independent and are usually added when the programming is almost complete.
3) Protection and chain procedures. Protection and chaining are indispensable parts of the process and must be carefully considered. It can avoid control logic confusion caused by illegal operations.
2. Program simulation debugging program The basic idea of ​​simulation debugging is to simulate the actual state of the scene in a convenient form and create the necessary environmental conditions for the operation of the program. According to the way of generating the on-site signal, the analog debugging has two forms: hardware simulation method and software simulation method.
1) The hardware simulation method uses some hardware devices (such as using another PLC or some input devices, etc.) to simulate the signals generated at the scene, and connects these signals to the input of the PLC system in a hard-wired manner. Strong.
2) The software simulation method is to write another set of simulation program in the PLC, and the simulation provides the on-site signal, which is simple and easy, but the timeliness is not easy to guarantee. In the process of simulation debugging, the method of segmentation debugging can be used, and the monitoring function of the programmer can be utilized.
6. Hardware implementation The hardware implementation mainly involves the design and on-site construction of hardware such as control cabinets (stages). The main contents are:
1) Design the electrical layout and installation wiring diagram of the control cabinet and console.
2) Design an electrical interconnection diagram between the various parts of the system.
3) Perform on-site wiring according to the construction drawings and conduct detailed inspection.
Since the programming and hardware implementation can be performed simultaneously, the design cycle of the PLC control system can be greatly shortened.
7. Online debugging Online debugging is to further adjust the online debugging through the program of simulation debugging. The online debugging process should be carried out step by step. The PLC is only connected to the input device, connected to the output device, and then connected to the actual load. If the requirements are not met, the hardware and program are adjusted. Usually you only need to modify some programs.
After all debugging is completed, the test run is delivered. After a period of operation, if the work is normal and the program does not need to be modified, the program should be cured into the EPROM to prevent the program from being lost.
8. Finishing and writing technical documents Technical documents include design specifications, hardware schematics, installation wiring diagrams, electrical component schedules, PLC programs, and instruction manuals.