PLC liquid level control anti-disturbance device and operation method

Abstract

The invention discloses a PLC liquid level control anti-disturbance device and an operation method, and belongs to the technical field of industrial automation control. The PLC liquid level control anti-disturbance device comprises a programmable logic controller, a liquid level sensor, a plurality of water pumps, a man-machine interface and a main and auxiliary detection module, and the PLC controls start and stop of the water pumps by setting upper and lower limit values of different water level intervals and combining operation logic of an SR trigger. The problem that when an existing industrial field device achieves automatic start-stop control by means of an external signal, the device cannot operate stably due to interference of the external signal is solved. According to the method, the operation accuracy of the equipment can be effectively ensured, and the problem of continuous start and stop of the equipment due to disturbance of the sensor or frequent environment change is avoided, so that the service life loss of the equipment is reduced, and the method is verified in actual production.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial automation control, and in particular to a PLC liquid level control anti-disturbance device and an operation method thereof. Background Art

[0002] It is a basic requirement of modern industrial production to automatically start and stop equipment according to the actual situation on site (such as liquid level, temperature and other factors). For different production scenarios, timely starting and shutting down equipment is a necessary condition to ensure safe production and normal production.

[0003] Traditional industrial control PLCs use a delay method to avoid interference from on-site factors, that is, when the start or stop condition signal is transmitted from the site to the PLC, the CPU issues a command to start (or stop) the device and maintain this state for a period of time (3-5s), at which time an anti-interference judgment is completed. This method assumes that when the device starts or stops, it will have a significant impact on the water level, and the water level scale will not rebound, which is an ideal assumption. However, in reality, due to various reasons, the start and stop signals will fluctuate after the holding time, causing the device to start and stop continuously with external conditions, causing damage to the life of the device. Traditional algorithms cannot effectively address this problem. Summary of the invention

[0004] The purpose of the present invention is to provide a PLC liquid level control anti-disturbance device and operation method, which fully integrates the external signal elements of the production site by combining the characteristics of PLC programming itself, and solves the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A PLC liquid level control anti-disturbance device, comprising:

[0007] A programmable logic controller for receiving and processing signals from the liquid level sensor;

[0008] Liquid level sensor, installed in the container, is used to monitor the liquid level changes in the container and send signals to the PLC;

[0009] Several water pumps are connected to the PLC and are used to start and stop according to the instructions issued by the PLC;

[0010] Human-machine interface, connected to the PLC, to allow operators to set high, medium and low water level ranges and other parameters;

[0011] The main and auxiliary detection module is integrated in the PLC program and is used to monitor the working status of each water pump and switch to the standby pump when the main pump fails; wherein, the PLC controls the start and stop of the water pump by setting the upper and lower limits of different water level intervals and combining the operating logic of the SR trigger.

[0012] Preferably, the liquid level sensor adopts a high-precision analog sensor to monitor the liquid level changes in real time and transmit the data to the PLC for processing.

[0013] Preferably, the PLC has built-in judgment logic for high, medium and low water level signals, and uses an SR trigger to determine the interval in which the current liquid level is located and whether the corresponding water pump needs to be started or stopped.

[0014] Preferably, the main-auxiliary detection module includes an abnormal signal feedback mechanism for quickly identifying the main pump failure and transferring control to the standby pump.

[0015] Preferably, the HMI interface directly sets or modifies the values ​​of the high, medium and low water level intervals through the screen.

[0016] Preferably, the PLC has a function of switching between automatic mode and manual mode.

[0017] A method for operating a PLC liquid level control anti-disturbance device is implemented based on a PLC liquid level control anti-disturbance device, comprising the following steps:

[0018] Step 1: Set the high, medium and low water level warning line values ​​and corresponding intervals;

[0019] Step 2: Data input: Use the HMI screen to input the set value into the PLC control program, or directly write into the fixed program;

[0020] Step 3: Status monitoring: The status of all water pumps is monitored in real time through the main and auxiliary detection program built into the PLC to ensure that when any water pump fails, it can be quickly switched to another normally working water pump;

[0021] Step 4, interval determination: Based on the SR trigger logic, decide whether to start or stop the water pump according to the current liquid level interval. If the liquid level is in the high water level interval, start both water pumps; if it is in the middle water level interval, only start one water pump; and when the liquid level is lower than the low water level interval, all water pumps stop.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention can effectively ensure the accuracy of equipment operation and avoid the problem of continuous start and stop of equipment due to disturbance of the sensor itself or frequent environmental changes, thereby reducing the life loss of equipment, and has been verified in actual production.

[0024] 2. After use, the present invention only requires image data and related computer equipment transmitted back in real time by the on-site camera for on-site maintenance, which can ensure the automatic operation of the equipment, thereby providing necessary guarantees for normal production, reducing labor costs and manual job settings to a certain extent, reducing costs and increasing efficiency for enterprises, and will not increase equipment costs and labor costs. However, it can ensure that the corresponding functions of the system are complete. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the first high liquid level trigger condition of the present invention;

[0026] Figure 2 It is a schematic diagram of the second high liquid level triggering condition of the present invention;

[0027] Figure 3 This is a schematic diagram of the third high liquid level trigger condition of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In order to solve the problem that the existing industrial field equipment cannot operate stably due to external signal interference when it relies on external signals to realize automatic start and stop control, please refer to Figure 1-3 , this embodiment provides the following technical solutions:

[0030] A PLC liquid level control anti-disturbance device, comprising:

[0031] A programmable logic controller for receiving and processing signals from the liquid level sensor;

[0032] The liquid level sensor is installed in the container to monitor the liquid level changes in the container and send the signal to the PLC. The liquid level sensor uses a high-precision analog sensor, which can accurately monitor the liquid level changes in real time and transmit the data to the PLC for processing;

[0033] Several water pumps are connected to the PLC and are used to start and stop according to the instructions issued by the PLC;

[0034] Human-machine interface, connected to the PLC, to allow operators to set high, medium and low water level ranges and other parameters;

[0035] The main and auxiliary detection module is integrated in the PLC program to monitor the working status of each water pump and switch to the backup pump when the main pump fails. The PLC sets the upper and lower limits of different water level intervals and combines the SR trigger logic to accurately control the start and stop of the water pump. The main and auxiliary detection module includes an abnormal signal feedback mechanism. When the main pump fails, it can quickly identify and transfer control to the backup pump to ensure the continuity and reliability of the system.

[0036] The PLC has built-in judgment logic for high, medium and low water level signals, and uses the SR trigger to determine the current liquid level range and whether the corresponding water pump needs to be started or stopped.

[0037] The HMI interface directly sets or modifies the values ​​of high, medium and low water levels through the screen, providing a flexible data input method to adapt to different production needs.

[0038] PLC has the function of switching between automatic mode and manual mode, ensuring that manual intervention in the operation of the equipment can be made when necessary.

[0039] In order to better demonstrate the operation process of the PLC liquid level control anti-disturbance device, this embodiment proposes an operation method of the PLC liquid level control anti-disturbance device, including the following steps:

[0040] Step 1. Data preparation: Set the high, medium and low water level warning line values ​​and the corresponding intervals according to on-site needs. Specifically, they are divided into high liquid level interval, medium liquid level interval and low liquid level interval. In the corresponding interval, the equipment will start or stop according to actual needs; there are enough buffers between the intervals. The data can be input through the HMI screen that interacts with the PLC. This method is more flexible and can be modified more conveniently if there are any subsequent changes; or write the program in advance according to actual production needs. In addition, set high, medium and low water level signals. The high, medium and low water level signals here refer to the high water level signal response when the actual water level falls in the high water level interval; the medium water level signal response when the actual water level falls in the medium water level interval; and the low water level signal response when the actual water level falls in the low water level interval.

[0041] Step 2: Data input: Use the HMI screen to input the set value into the PLC control program, or directly write into the fixed program;

[0042] Step 3. Status monitoring: The status of all water pumps is monitored in real time through the main and auxiliary detection program built into the PLC to ensure that when any water pump fails, it can be quickly switched to another normally working water pump. When one of the water pumps is in an abnormal working state, the other will be operated as the main water pump to avoid the whole system from not being able to work properly due to the inability of some equipment to start and stop normally.

[0043] Step 4: Interval determination: Based on the SR trigger logic, decide whether to start or stop the water pump according to the interval where the current liquid level is located. If the liquid level is in the high water level interval, start two water pumps; if it is in the middle water level interval, only start one water pump; and when the liquid level is lower than the low water level interval, all water pumps stop; the specific method is: the high, medium and low water level signals are triggered by the SR trigger, and the zeroing conditions are harsh to avoid continuous start and stop of the equipment due to water level fluctuations;

[0044] Take the high water level signal as an example: when the water level is less than the upper limit of the high water level interval and greater than the lower limit of the high water level interval, the high water level signal trigger condition 1 is met; when the water level meets the middle water level warning line, the high water level trigger condition 2 is met; when the water level is higher than the low water level, the high water level trigger condition 3 is met. When all the trigger conditions are met, the high water level signal is set to 1; the zeroing conditions are: no middle water level signal, no low water level signal, no manual signal, and lower than the upper limit of the middle water level interval. The middle water level signal and the low water level signal are triggered and zeroed in a similar way;

[0045] Step 5: Mode switching: adjust the system operation mode to automatic mode so that the PLC can automatically control the start and stop of the water pump according to the changes in liquid level;

[0046] Step 6. Debugging and monitoring: After completing the above configuration, the system needs to be debugged and the system performance needs to be continuously monitored during the initial use phase to ensure that it works as expected.

[0047] The above embodiment takes the common three-stage water level control of the water pump start and stop as an example, and other complex situations can be expanded accordingly based on the above content.

[0048] Working principle: First, set the high, medium and low water level warning line values ​​and the corresponding intervals, use the HMI screen to input the set values ​​into the PLC control program, or directly write into the fixed program, and monitor the status of all water pumps in real time through the PLC's built-in main and auxiliary detection programs to ensure that when any water pump fails, it can be quickly switched to another normally working water pump. Based on the SR trigger logic, decide whether to start or stop the water pump according to the current liquid level interval. If the liquid level is in the high water level interval, start both water pumps; if it is in the medium water level interval, only start one water pump; and when the liquid level is lower than the low water level interval, all water pumps stop.

[0049] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0050] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A PLC liquid level control anti-disturbance device, characterized in that: include: A programmable logic controller for receiving and processing signals from the liquid level sensor; Liquid level sensor, installed in the container, is used to monitor the liquid level changes in the container and send signals to the PLC; Several water pumps are connected to the PLC and are used to start and stop according to the instructions issued by the PLC; Human-machine interface, connected to the PLC, to allow operators to set high, medium and low water level ranges and other parameters; The main and auxiliary detection module is integrated in the PLC program and is used to monitor the working status of each water pump and switch to the standby pump when the main pump fails; wherein, the PLC controls the start and stop of the water pump by setting the upper and lower limits of different water level intervals and combining the operating logic of the SR trigger.

2. A PLC liquid level control anti-disturbance device according to claim 1, characterized in that: The liquid level sensor adopts a high-precision analog sensor to monitor the liquid level changes in real time and transmit the data to the PLC for processing.

3. A PLC liquid level control anti-disturbance device according to claim 2, characterized in that: The PLC has built-in judgment logic for high, medium and low water level signals, and uses an SR trigger to determine the interval in which the current liquid level is located and whether the corresponding water pump needs to be started or stopped.

4. A PLC liquid level control anti-disturbance device according to claim 3, characterized in that: The main and auxiliary detection module includes an abnormal signal feedback mechanism for quickly identifying the main pump failure and transferring control to the standby pump.

5. A PLC liquid level control anti-disturbance device according to claim 4, characterized in that: The HMI interface directly sets or modifies the values ​​of the high, medium and low water level ranges through the screen.

6. A PLC liquid level control anti-disturbance device according to claim 5, characterized in that: The PLC has the function of switching between automatic mode and manual mode.

7. An operating method of a PLC liquid level control anti-disturbance device, implemented based on a PLC liquid level control anti-disturbance device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Set the high, medium and low water level warning line values ​​and corresponding intervals; Step 2: Data input: Use the HMI screen to input the set value into the PLC control program, or directly write into the fixed program; Step 3: Status monitoring: The status of all water pumps is monitored in real time through the main and auxiliary detection program built into the PLC to ensure that when any water pump fails, it can be quickly switched to another normally working water pump; Step 4, interval determination: Based on the SR trigger logic, decide whether to start or stop the water pump according to the current liquid level interval. If the liquid level is in the high water level interval, start both water pumps; if it is in the middle water level interval, only start one water pump; and when the liquid level is lower than the low water level interval, all water pumps stop.

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