PID (Proportion Integration Differentiation) regulating loop, industrial control system and constant-pressure water supply regulating method

Abstract

The invention provides a PID adjusting loop, an industrial control system and a constant-pressure water supply adjusting method, and relates to the technical field of industrial control. The circuit comprises a selection circuit, an operation circuit and a switching circuit. The operational circuit calculates a deviation absolute value of an input process variable and a set value and transmits the deviation absolute value to the selection circuit; the selection circuit outputs a high level when the deviation absolute value is greater than the upper limit value of the first dead zone, and outputs a low level when the deviation absolute value belongs to the second dead zone; when the input of the switching circuit is a high level, the connection between the PID controller and the execution unit of the controlled equipment is conducted, and the process variable is adjusted to approach a set value, and when the input of the switching circuit is a low level, the self-circulation loop is conducted, and the adjustment instruction is kept unchanged. By introducing a variable dead zone mechanism, frequent adjustment actions are reduced, abrasion of the controlled equipment is reduced, and meanwhile it is ensured that the adjustment deviation is controlled within a small range, so that the contradiction between high-precision adjustment and low equipment abrasion is balanced.

Description

Technical Field

[0001] This application relates to the field of industrial control technology, and particularly to a PID regulation loop, an industrial control system, and a constant pressure water supply regulation method. Background Art

[0002] A Proportional-Integral-Derivative (PID) controller adjusts the process variable to quickly and stably approach the set value by regulating three links: proportional, integral, and derivative. Due to its simple structure and excellent regulation performance, it is widely used in the field of industrial control, such as in process control of liquid level, pressure, temperature, and flow rate.

[0003] In related technologies, in order to reduce the repeated fluctuations of the process variable near the set value, a "dead zone" mechanism is usually introduced into the PID regulation loop. The dead zone is a range symmetric about 0. When the absolute value of the deviation between the process variable and the set value is less than the dead zone value, the proportional and derivative links of the PID controller are disabled, and only the integral link is relied on to maintain the current output value. However, it is difficult to simultaneously meet the requirements of high-precision regulation and low equipment wear. Summary of the Invention

[0004] The PID regulation loop, industrial control system, and constant pressure water supply regulation method provided by this application are used to simultaneously meet the requirements of high-precision regulation and low equipment wear.

[0005] In a first aspect, this application provides a PID regulation loop, including: a selection circuit, an arithmetic circuit, and a switching circuit connected to the selection circuit; where:

[0006] The arithmetic circuit is used to calculate the absolute value of the deviation between the input process variable and the set value, and transmit the absolute value of the deviation to the selection circuit;

[0007] The selection circuit is used to output a high level when the absolute value of the deviation is greater than the upper limit value of the first dead zone interval; and output a low level when the absolute value of the deviation belongs to the second dead zone interval, where the upper limit value of the first dead zone interval is greater than the upper limit value of the second dead zone interval;

[0008] The switching circuit is used to conduct the connection between the PID controller included therein and the execution unit of the controlled device when the input is a high level, so as to transmit the operation result of the PID controller to the execution unit. The execution unit is used to adjust the process variable based on the operation result, so that the process variable approaches the set value; when the input is a low level, the self-circulation loop is conducted, and the self-circulation loop is used to keep the adjustment instruction of the controlled device unchanged.

[0009] In a possible implementation, the arithmetic circuit includes a subtraction operation unit and an absolute value operation unit, where: the input end of the subtraction operation unit serves as the input end of the arithmetic circuit, the output end of the subtraction operation unit is connected to the input end of the absolute value operation unit, and the output end of the absolute value operation unit is connected to the input end of the selection circuit; the subtraction operation unit is used to calculate the deviation between the process variable and the set value; the absolute value operation unit is used to take the absolute value of the deviation to obtain the absolute deviation value.

[0010] In a possible implementation, the selection circuit includes a first signal monitoring unit, a second signal monitoring unit, and a reset-set flip-flop; the input ends of both the first signal monitoring unit and the second signal monitoring unit are connected to the output end of the arithmetic circuit; the first signal monitoring unit is connected to the set end of the reset-set flip-flop and is used to set the reset-set flip-flop to output a high level when the absolute deviation value is greater than the upper limit value of the first dead zone interval; the second signal monitoring unit is connected to the reset end of the reset-set flip-flop and is used to set the reset-set flip-flop to output a low level when the absolute deviation value is greater than the lower limit value of the second dead zone interval and less than the upper limit value of the second dead zone interval.

[0011] In a possible implementation, the first signal monitoring unit adopts a high-value monitoring algorithm; the second signal monitoring unit adopts a high-low value monitoring algorithm.

[0012] In a possible implementation, the switching circuit further includes a switching unit, and the input of the PID controller includes a process variable and a set value; the control end of the switching unit is connected to the output end of the selection circuit, the input end of the switching unit is connected to the output end of the PID controller, and when the input end of the switching unit is connected to the output end of the switching unit, a self-loop is formed; where: the PID controller is used to generate an adjustment instruction according to the deviation between the process variable and the set value; the switching unit is used to conduct the connection between the input end of the switching unit and the output end of the PID controller when the output of the selection circuit is high, and transmit the adjustment instruction to the execution unit; and when the output of the selection circuit is low, trigger the switching unit to self-loop and keep the current adjustment instruction of the controlled device unchanged.

[0013] In a possible implementation, the switching unit is a TRANSFER unit.

[0014] In a possible implementation, the upper limit value of the first dead zone interval is set according to the dynamic response characteristics of the controlled device; and / or, the lower limit value and the upper limit value of the second dead zone interval are set according to the adjustment accuracy requirements of the controlled device.

[0015] In a second aspect, the present application provides an industrial control system, which is characterized by including the PID adjustment loop described in any item of the first aspect.

[0016] In a possible implementation, the industrial control system further includes a data acquisition component, which is connected to the process variable input end of the PID adjustment loop, and is configured to acquire the process variable adjusted by the PID adjustment loop and transmit the acquired process variable to the process variable input end.

[0017] In a third aspect, the present application provides a constant pressure water supply adjustment method, which is applied to the industrial control system described in any one of the second aspects. The constant pressure water supply adjustment method includes:

[0018] Obtain the water supply pressure;

[0019] Input the water supply pressure into the PID adjustment loop. When the absolute value of the deviation between the water supply pressure and the set value of the water supply pressure exceeds the upper limit value of the first dead zone interval, the connection between the PID controller and the execution unit of the frequency converter is turned on, so that the frequency conversion instruction output by the PID controller is transmitted to the execution unit of the frequency converter to increase the frequency of the frequency converter; when the absolute value of the deviation belongs to the second dead zone interval, the self-circulation loop is turned on to keep the current frequency of the frequency converter unchanged.

[0020] The PID adjustment loop, industrial control system and constant pressure water supply adjustment method provided by the present application include: a selection circuit, an arithmetic circuit and a switching circuit connected to the selection circuit; wherein, the arithmetic circuit is configured to calculate the absolute value of the deviation between the input process variable and the set value and transmit the absolute value of the deviation to the selection circuit; the selection circuit is configured to output a high level when the absolute value of the deviation is greater than the upper limit value of the first dead zone interval and output a low level when the absolute value of the deviation belongs to the second dead zone interval, wherein the upper limit value of the first dead zone interval is greater than the upper limit value of the second dead zone interval; the switching circuit is configured to turn on the connection between the PID controller included therein and the execution unit of the controlled device when the input is a high level, so as to transmit the operation result of the PID controller to the execution unit, and the execution unit is configured to adjust the process variable based on the operation result to make the process variable approach the set value. When the input is a low level, the self-circulation loop is turned on, and the self-circulation loop is used to keep the adjustment instruction of the controlled device unchanged. By introducing a variable dead zone mechanism, the present application adopts a larger dead zone when enabling the PID controller to adjust, effectively reducing frequent adjustment actions, thereby significantly reducing the wear of the controlled device and extending the service life of the controlled device; when adjusting to a smaller deviation range, it automatically switches to a smaller dead zone to ensure that the final adjustment deviation can be controlled within a smaller range, maintaining both the adjustment accuracy of the PID adjustment loop and effectively balancing the contradiction between high-precision adjustment and low device wear; in addition, since the PID controller only starts to adjust when the absolute value of the deviation between the process variable and the set value exceeds the upper limit value of the larger dead zone, the anti-interference ability of the PID adjustment loop is significantly improved, reducing misoperations caused by external noise or disturbances, and further enhancing the stability and reliability of the PID adjustment loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0022] Figure 1 It is a schematic diagram of a PID regulation loop in the related art;

[0023] Figure 2 It is a schematic diagram of the structure of a PID regulation loop provided by an exemplary embodiment of the present application;

[0024] Figure 3 It is a schematic diagram of the structure of an arithmetic circuit provided by an exemplary embodiment of the present application;

[0025] Figure 4 It is a schematic diagram of the structure of a selection circuit provided by an exemplary embodiment of the present application;

[0026] Figure 5 It is another schematic diagram of the structure of a PID regulation loop provided by an exemplary embodiment of the present application;

[0027] Figure 6 It is a schematic diagram of the structure of an industrial control system provided by an exemplary embodiment of the present application;

[0028] Figure 7 It is a schematic diagram of the process of a constant pressure water supply regulation method provided by an exemplary embodiment of the present application;

[0029] Figure 8 It is a schematic diagram of a constant pressure water supply PID regulation loop provided by an exemplary embodiment of the present application.

[0030] Through the above-mentioned accompanying drawings, specific embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These accompanying drawings and written descriptions are not intended to limit the scope of the concept of the present application in any way, but to explain the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0032] The terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of this application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, products, or devices.

[0033] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. And the collection, use, and processing of relevant data need to comply with relevant laws, regulations, and standards, and corresponding operation entrances are provided for users to choose to authorize or refuse.

[0034] Figure 1 It is a schematic diagram of a PID adjustment loop in the related art. As Figure 1 shown, M / A MODE represents a manual / automatic mode adjustment module for controlling the working mode or state of the PID controller; MRE, ARE, LWI, RAI, PLW, PRA, BACT, STRK, MAN, AUTO, LOC, TRK, and MODE are identifiers for different working modes or states corresponding to M / A MODE; among them, MRE (Manual Remote Mode) represents the manual remote mode, ARE (Automatic Remote Mode) represents the automatic remote mode, LWI (Local Manual Mode) represents the local manual mode, RAI (Remote Automatic Mode) represents the remote automatic mode, PLW (Process Low Limit) represents the process low limit, PRA (Process High Limit) represents the process high limit, BACT (Backup Activate) represents backup activation, STRK (Strike Mode) represents the start mode, MAN (Manual Mode) represents the manual mode, AUTO (Automatic Mode) represents the automatic mode, LOC (Local Mode) represents the local mode, TRK (Track Mode) represents the tracking mode, and MODE represents mode selection.

[0035] Accordingly, in the above PID control loop, when the absolute value of the deviation between the process variable and the set value is less than the preset dead zone value, the control deviation output is 0. At this time, the proportional and derivative links of the PID controller are disabled, and only the integral link is relied on to maintain the current output value. Since the preset dead zone value is a fixed value, once the absolute value of the deviation enters the dead zone, the adjustment function of the PID controller will be limited. If the dead zone value is set too small, frequent adjustments cannot be effectively prevented. If the dead zone value is set too large, the adjustment accuracy of the PID control loop will be reduced, and it can only be applied to scenarios with low requirements for adjustment accuracy, making it difficult to balance the needs of high-precision adjustment and low equipment wear at the same time. In addition, when the absolute value of the deviation enters the dead zone, the output will immediately remain unchanged. If the absolute value of the deviation is at the edge of the dead zone, external noise interference may cause the absolute value of the deviation to frequently leave or re-enter the dead zone, resulting in frequent adjustment actions of the controlled device and low anti-interference ability of the PID control loop.

[0036] In view of the problems existing in the related art, the present application proposes a PID control loop. By introducing a variable dead zone mechanism, a larger dead zone is adopted when the PID controller is enabled for adjustment, effectively reducing frequent adjustment actions, thereby significantly reducing the wear of the controlled device. When adjusting to a smaller deviation range, it automatically switches to a smaller dead zone, ensuring the adjustment accuracy of the PID control loop. Through the automatic variable dead zone, it is possible to effectively balance the contradiction between high-precision adjustment and low equipment wear while ensuring the adjustment accuracy of the controlled device. At the same time, it also significantly improves the anti-interference ability of the PID control loop, further enhancing the stability and reliability of the PID control loop.

[0037] The following uses specific embodiments to elaborate in detail on the technical solutions of the present application and how the technical solutions of the present application solve the above technical problems. These several specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the drawings.

[0038] Figure 2 FIG. [ID number] is a schematic structural diagram of a PID control loop provided by an exemplary embodiment of the present application. As Figure 2 shown, the PID control loop 20 provided by the embodiment of the present application includes an arithmetic circuit 21, a selection circuit 22, and a switching circuit 23. The selection circuit 22 is respectively connected to the arithmetic circuit 21 and the switching circuit 23; wherein:

[0039] The arithmetic circuit 21 is configured to calculate the absolute value of the deviation between the input process variable and the set value, and transmit the absolute value of the deviation to the selection circuit.

[0040] Exemplarily, in one implementation, the operating state of the controlled device is monitored in real time by sensors installed at key positions of the controlled device, and the monitored process variables are transmitted to the input end of the arithmetic circuit 21. Among them, common sensors include but are not limited to temperature sensors, pressure sensors, flow sensors, liquid level sensors, speed sensors, humidity sensors, or photoelectric sensors, etc.

[0041] In another implementation, the values of the process variables are directly displayed or output by instruments. These instruments usually integrate sensors and signal processing circuits, can provide standardized output signals, and transmit the output process variables to the input end of the arithmetic circuit 21. Among them, common instruments include but are not limited to temperature transmitters, pressure transmitters, flow meters, or liquid level gauges, etc.

[0042] Correspondingly, the arithmetic circuit 21 calculates the absolute value of the deviation between the process variable PV and the preset set value SP, |PV - SP|, based on the input process variable PV and the set value SP, and transmits this value to the selection circuit 22.

[0043] The selection circuit 22 is used to output a high level when the absolute value of the deviation is greater than the upper limit value of the first dead zone interval; and output a low level when the absolute value of the deviation belongs to the second dead zone interval, where the upper limit value of the first dead zone interval is greater than the upper limit value of the second dead zone interval.

[0044] Among them, the first dead zone interval refers to the larger dead zone interval, and the second dead zone interval refers to the smaller dead zone interval. Correspondingly, the selection circuit 22 makes a judgment based on the magnitude of the absolute value of the deviation. Exemplarily, if the absolute value of the deviation is greater than the upper limit value of the first dead zone interval (for example, |PV - SP| > 10), a high level is output; if the absolute value of the deviation is within the second dead zone interval (for example, 1 < |PV - SP| ≤ 5), a low level is output; if the absolute value of the deviation is less than the upper limit value of the second dead zone interval (for example, |PV - SP| ≤ 5), a low level is output.

[0045] The switching circuit 23 is used to connect the PID controller and the execution unit of the controlled device when the input is a high level, so as to transmit the operation result of the PID controller to the execution unit. The execution unit is used to adjust the process variable based on the operation result, so that the process variable approaches the set value; when the input is a low level, the self - circulation loop is connected, and the self - circulation loop is used to keep the adjustment instruction of the controlled device unchanged.

[0046] Among them, the PID controller is used to perform proportional, integral, and derivative operations based on the deviation between the process variable and the set value to generate a regulation instruction; the execution unit is used to receive the regulation instruction of the PID controller and regulate the process variable; the switching circuit 23 is used to switch the connection between the PID controller and the execution unit according to the level of the input signal, or conduct the self-loop; the self-loop is used to keep the current regulation instruction unchanged when the input of the switching circuit is at a low level.

[0047] Exemplarily, when the input of the switching circuit 23 is at a high level, the switching circuit 23 conducts the connection between the PID controller it includes and the execution unit of the controlled device. The PID controller receives the process variable PV and the set value SP, calculates the deviation between the process variable and the set value, i.e., e = SP - PV, and performs proportional, integral, and derivative operations to generate a regulation instruction. The regulation instruction is transmitted to the execution unit of the controlled device through the switching circuit 23, and the execution unit regulates the process variable (such as adjusting the valve opening or motor speed, etc.) according to the regulation instruction to make the process variable approach the set value. Correspondingly, when the input of the switching circuit 23 is at a low level, the switching circuit disconnects the connection between the PID controller and the execution unit and conducts the self-loop. The self-loop feeds back the current regulation instruction to the execution unit of the controlled device and keeps the regulation instruction unchanged. The execution unit continues to execute the previous regulation instruction, and the process variable remains stable to avoid frequent regulation actions.

[0048] It should be noted that the upper limit value of the first dead zone interval, the upper limit value of the second dead zone interval, and the lower limit value of the second dead zone interval are only examples. In actual applications, they can be flexibly adjusted according to actual needs or application scenarios, etc., and are not limited here.

[0049] The PID regulation loop provided by the embodiments of the present application introduces a variable dead zone mechanism. When the PID controller is enabled for regulation, a larger dead zone is adopted, which effectively reduces frequent regulation actions, thereby significantly reducing the wear of the controlled device and extending the service life of the controlled device. When the regulation reaches a smaller deviation range, it automatically switches to a smaller dead zone to ensure that the final regulation deviation can be controlled within a smaller range, which not only maintains the regulation accuracy of the PID regulation loop but also effectively balances the contradiction between high-precision regulation and low device wear. In addition, since the PID controller only starts regulation when the absolute value of the deviation between the process variable and the set value exceeds the upper limit value of the larger dead zone, the anti-interference ability of the PID regulation loop is significantly improved, the misoperation caused by external noise or disturbance is reduced, and the stability and reliability of the PID regulation loop are further enhanced.

[0050] In some embodiments, the arithmetic circuit includes a subtraction operation unit and an absolute value operation unit, where: the input terminal of the subtraction operation unit serves as the input terminal of the arithmetic circuit, the output terminal of the subtraction operation unit is connected to the input terminal of the absolute value operation unit, and the output terminal of the absolute value operation unit is connected to the input terminal of the selection circuit; the subtraction operation unit is used to calculate the deviation between the process variable and the set value; the absolute value operation unit is used to take the absolute value of the deviation to obtain the absolute deviation value.

[0051] Exemplarily, Figure 3 is a schematic structural diagram of the arithmetic circuit provided by an exemplary embodiment of the present application. As Figure 3 shown, the arithmetic circuit includes a subtraction operation unit and an absolute value operation unit. Among them, the subtraction operation unit can use an operational amplifier (such as LM741) and resistors (such as R1 = R2 = R3 = R4 = 10 kΩ) to build a differential amplifier circuit. When inputting PV and SP, its output is e = PV – SP; the absolute value operation unit can use two operational amplifiers (such as LM741) and diodes (such as 1N4148) to build a precision full-wave rectifier circuit. When inputting e, the corresponding output is |e|.

[0052] Correspondingly, the process variable PV and the set value SP are input into the subtraction operation unit. The subtraction operation unit calculates the deviation e = PV - SP and outputs the result to the absolute value operation unit; the absolute value operation unit receives the deviation e, calculates its absolute value |e|, and outputs the absolute deviation value |e| to the input terminal of the selection circuit.

[0053] It can be understood that the above construction of the subtraction operation unit and the absolute value operation unit is only an example. In actual applications, other circuit designs or digital calculation methods can also be used to achieve the same function. For example, in a microcontroller-based system, the deviation and absolute value can be directly calculated through software programming without using a hardware circuit. In addition, according to the requirements of specific application scenarios, the circuit parameters can also be adjusted to adapt to different input ranges and precision requirements.

[0054] In the embodiment of the present application, through the collaborative work of the subtraction operation unit and the absolute value operation unit, the accurate calculation of the absolute deviation between the process variable and the set value is realized. The circuit design is simple, the response is fast, and the precision is high. It can be applied to a variety of industrial control scenarios, which helps to provide reliable data support for the control decision of the controlled device.

[0055] In some embodiments, the selection circuit includes a first signal monitoring unit, a second signal monitoring unit, and a reset-set flip-flop. The input ends of the first signal monitoring unit and the second signal monitoring unit are both connected to the output end of the arithmetic circuit. The first signal monitoring unit is connected to the set end of the reset-set flip-flop and is configured to set the reset-set flip-flop to output a high level when the absolute value of the deviation is greater than the upper limit value of the first dead zone interval. The second signal monitoring unit is connected to the reset end of the reset-set flip-flop and is configured to reset the reset-set flip-flop to output a low level when the absolute value of the deviation is greater than the lower limit value and less than the upper limit value of the second dead zone interval.

[0056] Exemplarily, Figure 4 FIG. is a schematic structural diagram of a selection circuit provided by an exemplary embodiment of the present application. As Figure 4 shown, the selection circuit includes a first signal monitoring unit, a second signal monitoring unit, and a reset-set (RS for short) flip-flop. Correspondingly, the absolute value of the deviation calculated by the arithmetic circuit is simultaneously input to the first signal monitoring unit and the second signal monitoring unit. The first signal monitoring unit is configured to determine whether the absolute value of the deviation exceeds the upper limit value of a preset first dead zone interval. If the absolute value of the deviation exceeds the upper limit value, the reset-set flip-flop connected to the output end of the first signal monitoring unit is set (i.e., S = 1, R = 0), and the reset-set flip-flop outputs a high level. At the same time, the second signal monitoring unit is configured to determine whether the absolute value of the deviation enters the second dead zone interval. If the absolute value of the deviation is greater than the lower limit value and less than the upper limit value of the second dead zone interval, the reset-set flip-flop connected to the output end of the second signal monitoring unit is reset (i.e., S = 0, R = 1), and the reset-set flip-flop outputs a low level.

[0057] In some embodiments, the first signal monitoring unit adopts a high-value monitoring algorithm; the second signal monitoring unit adopts a high-low value monitoring algorithm.

[0058] Exemplarily, the first signal monitoring unit adopts a high-value monitoring algorithm, that is, the HIGHMON algorithm; the second signal monitoring unit adopts a high-low value monitoring algorithm, that is, the HIGHLOWMON algorithm. Among them, the high-value monitoring algorithm is a high-signal monitor with a reset dead zone and fixed / variable limits. If the input value (IN) exceeds the preset upper limit value, the digital output flag (OUT) is set to TRUE. The high-low value monitoring algorithm is a high and low signal monitor with a reset dead zone and fixed / variable limits. If the input value (IN) is greater than the preset upper limit value or less than the preset lower limit value, the digital output flag (OUT) is set to TRUE.

[0059] Correspondingly, the first signal monitoring unit is used to determine whether the absolute value of the deviation exceeds the upper limit value of a preset first dead zone interval. If the absolute value of the deviation exceeds this upper limit value, the digital output flag (OUT) of the first signal monitoring unit is set to TRUE, and the reset - set flip - flop connected to the output terminal of the first signal monitoring unit is set (i.e., S = 1, R = 0), and the reset - set flip - flop outputs a high level. At the same time, the second signal monitoring unit is used to determine whether the absolute value of the deviation enters a second dead zone interval. If the absolute value of the deviation is greater than the lower limit value of the second dead zone interval and less than the upper limit value of the second dead zone interval, the digital output flag (such as OUT) of the second signal monitoring unit is set to TRUE, and the reset - set flip - flop connected to the output terminal of the second signal monitoring unit is reset (i.e., S = 0, R = 1), and the reset - set flip - flop outputs a low level.

[0060] In some embodiments, the switching circuit further includes a switching unit. The input of the PID controller includes a process variable and a set value. The control end of the switching unit is connected to the output end of the selection circuit, and the input end of the switching unit is connected to the output end of the PID controller. When the input end of the switching unit is connected to the output end of the switching unit, a self - loop circuit is formed. Among them: The PID controller is used to generate an adjustment instruction according to the deviation between the process variable and the set value. The switching unit is used to, when the output of the selection circuit is at a high level, conduct the connection between the input end of the switching unit and the output end of the PID controller, and transmit the adjustment instruction to the execution unit; and, when the output of the selection circuit is at a low level, trigger the switching unit to self - loop and maintain the current adjustment instruction of the controlled device unchanged.

[0061] Exemplarily, Figure 5 Another structural schematic diagram of the PID adjustment loop provided by an exemplary embodiment of the present application is shown in Figure 5 As shown, FLAG represents the control - end mark of the switching unit, SUB represents the subtraction operation unit, ABS represents the absolute - value operation unit, HIGHMON represents the first signal monitoring unit, HIGHLOWMON represents the second signal monitoring unit algorithm, and FLIPFLOP represents the reset - set flip - flop.

[0062] Correspondingly, the switching unit is used to switch two inputs. When the absolute value of the deviation exceeds the upper limit of the preset first dead zone range, the reset-set flip-flop outputs a high level, FLAG is set to 1, and the connection between the input end of the switching unit and the output end of the PID controller is turned on. The adjustment instruction generated by the PID controller according to the deviation between the process variable and the set value is transmitted to the execution unit of the controlled device through the switching unit. The execution unit of the controlled device executes the adjustment instruction for adjustment, so that the process variable continuously approaches the set value. When the absolute value of the deviation enters a smaller dead zone range, it indicates that the adjustment accuracy has met the operation requirements. At this time, the reset-set flip-flop is reset, FLAG is set to 0, the switching unit has a self-loop, the adjustment instruction remains unchanged, and the execution unit of the controlled device remains at the current level.

[0063] In the embodiment of the present application, through the design of the switching unit, it can be flexibly switched between different control modes according to the output state of the selection circuit. When the output of the selection circuit is high, it can respond in real time to the adjustment instruction of the PID controller to achieve dynamic adjustment of the controlled device. When the output is low, the current adjustment instruction of the controlled device remains unchanged, avoiding unnecessary adjustments, effectively preventing system instability caused by frequent switching or unnecessary adjustments, thereby improving the stability of the system. At the same time, it can also effectively reduce energy consumption and mechanical wear, and help extend the service life of the device. In addition, the self-loop function of the switching unit keeps the system state unchanged when the output of the selection circuit is low, thereby improving the robustness of the system to external disturbances and ensuring stable operation under abnormal or unstable conditions. By integrating the switching unit and the PID controller, the design and implementation are more simplified, reducing additional hardware requirements and complex control logic, which is of positive significance for reducing the overall cost and maintenance difficulty of the system.

[0064] In some embodiments, the switching unit is a TRANSFER unit.

[0065] Exemplarily, as Figure 5 shown, the TRANSFER unit performs the switching between two inputs. If the digital input FLAG is TRUE, the output is equal to the input of Y (i.e., the first input end of the TRANSFER unit); if the digital input FLAG is FALSE, the output is equal to the input of N (i.e., the second input end of the TRANSFER unit). In addition, the TRANSFER unit also has the functions of output ramp-up during tracking switching and output limiting, which can achieve smooth transition of the output during input switching, avoid sudden changes in the output, and can control the amplitude of the output signal according to the preset limit value.

[0066] In the embodiments of the present application, through the control of the digital input FLAG, the TRANSFER unit can flexibly switch between two inputs, adapt to different control requirements and operating conditions, and improve the flexibility and adaptability of the system. In addition, the output ramp function of the TRANSFER unit ensures that when the input signal switches, the output can smoothly transition, avoiding system instability or damage to the controlled device that may be caused by output mutations. Moreover, the output limiting function ensures that the output signal is within a safe range, preventing system failures or performance degradation caused by excessive or too small signals, and enhancing the safety and reliability of the system.

[0067] In some embodiments, the upper limit value of the first dead zone interval is set according to the dynamic response characteristics of the controlled device; and / or, the lower limit value and the upper limit value of the second dead zone interval are set according to the adjustment accuracy requirements of the controlled device.

[0068] Exemplarily, in one implementation, the upper limit value of the first dead zone interval is set according to the dynamic response characteristics of the controlled device such as a motor. Specifically, the dynamic response characteristics of the motor can be measured through experiments, including parameters such as the inertia, damping coefficient, and response time of the motor. By analyzing these parameters, the response speed and stability of the motor under different input signals can be determined. In order to reduce system instability caused by overly frequent adjustment of the control signal, the upper limit value of the first dead zone interval is set to a maximum tolerable deviation value, such that within this deviation range, the dynamic response of the motor remains within an acceptable range.

[0069] In another implementation, the lower limit value and the upper limit value of the second dead zone interval are set according to the adjustment accuracy requirements of the controlled device such as a motor, where the adjustment accuracy requirements are usually determined by the specific application scenario. For example, in a high-precision manufacturing process, the speed of the motor needs to be maintained within a very precise range. Therefore, the lower limit value of the second dead zone interval is set to the minimum acceptable value of the motor speed deviation, and the upper limit value is to prevent system oscillation caused by over-adjustment. In this way, unnecessary adjustment of the control signal can be reduced while ensuring the adjustment accuracy.

[0070] In yet another implementation, the upper limit value of the first dead zone interval is set according to the dynamic response characteristics of the controlled device such as a motor, and the lower limit value and the upper limit value of the second dead zone interval are set according to the adjustment accuracy requirements of the controlled device such as a motor, where the dynamic response characteristics of the motor can be measured through experiments, including parameters such as the inertia, damping coefficient, and response time of the motor, and the adjustment accuracy requirements are usually determined by the specific application scenario.

[0071] It can be understood that in practical applications, the specific upper limit value or lower limit value of the above dead zone interval can be obtained through experimental calibration and simulation analysis to ensure the best performance of the system under different working conditions. Therefore, the upper limit value of the first dead zone interval, the lower limit value of the second dead zone interval, and the upper limit value of the second dead zone interval are not limited here.

[0072] In the embodiment of the present application, by setting the upper limit value of the first dead zone interval according to the dynamic response characteristics of the controlled device, the oscillation and instability phenomena under rapidly changing conditions can be effectively reduced, and the overall stability is improved; by setting the limit value of the second dead zone interval according to the regulation accuracy requirements of the controlled device, the best balance between accuracy and stability can be achieved. This flexible setting method ensures that while meeting the accuracy requirements, the adverse effects caused by over-regulation are avoided; in addition, by flexibly setting the dead zone interval according to the specific device characteristics and application requirements, it can better adapt to different operating environments and conditions, and effectively improve the adaptability and flexibility of the PID regulation loop.

[0073] In summary, the present application has at least the following advantages:

[0074] First, by introducing a variable dead zone mechanism, a larger dead zone is adopted when the PID controller is enabled for regulation, which effectively reduces frequent regulation actions, thereby significantly reducing the wear of the controlled device and extending the service life of the controlled device; when the regulation reaches a smaller deviation range, it automatically switches to a smaller dead zone to ensure that the final regulation deviation can be controlled within a smaller range, which not only maintains the regulation accuracy of the PID regulation loop but also effectively balances the contradiction between high-precision regulation and low device wear; in addition, since the PID controller only starts to regulate when the absolute value of the deviation between the process variable and the set value exceeds the larger dead zone upper limit value, the anti-interference ability of the PID regulation loop is significantly improved, the misoperation caused by external noise or disturbance is reduced, and the stability and reliability of the PID regulation loop are further enhanced.

[0075] II. Through the design of the switching unit, it is possible to flexibly switch between different control modes according to the output state of the selection circuit. When the output of the selection circuit is high, it can respond in real time to the adjustment instructions of the PID controller to achieve dynamic adjustment of the controlled device; while when the output is low, the current adjustment instruction of the controlled device is maintained unchanged, avoiding unnecessary adjustments, effectively preventing system instability caused by frequent switching or unnecessary adjustments, thereby improving the system stability. At the same time, it can also effectively reduce energy consumption and mechanical wear, contributing to the extension of the service life of the device; in addition, the self-loop function of the switching unit keeps the system state unchanged when the output of the selection circuit is low, thus improving the robustness of the system to external disturbances and ensuring stable operation under abnormal or unstable conditions; by integrating the switching unit and the PID controller, the design and implementation are simplified, reducing additional hardware requirements and complex control logic, which is of positive significance for reducing the overall cost and maintenance difficulty of the system.

[0076] III. By setting the upper limit value of the first dead zone interval according to the dynamic response characteristics of the controlled device, it is possible to effectively reduce oscillations and instability phenomena under rapidly changing conditions, improving the overall stability; by setting the limit value of the second dead zone interval according to the adjustment accuracy requirements of the controlled device, it is possible to achieve the best balance between accuracy and stability. This flexible setting method ensures that while meeting the accuracy requirements, it avoids the adverse effects of over-regulation; in addition, flexibly setting the dead zone interval according to the specific device characteristics and application requirements can better adapt to different operating environments and conditions, effectively enhancing the adaptability and flexibility of the PID adjustment loop.

[0077] The above embodiments introduce the implementation method of the PID adjustment loop. Next, the application of the PID adjustment loop will be introduced.

[0078] Figure 6 FIG. [X] is a schematic structural diagram of an industrial control system provided by an exemplary embodiment of the present application. As Figure 6 shown, the industrial control system 60 includes the PID adjustment loop described in the above embodiments.

[0079] Exemplarily, the industrial control system is applicable to industrial scenarios that require precise control of process variables, such as including but not limited to temperature control, pressure control, flow control, and liquid level control, etc. Among them, temperature control includes, for example, constant temperature control of heating furnaces and reaction kettles, etc.; pressure control includes, for example, pressure regulation of compressed air systems and hydraulic systems, etc.; flow control includes, for example, flow regulation of water supply systems and chemical processes, etc.; liquid level control includes, for example, liquid level regulation of storage tanks and pools, etc.

[0080] In the embodiments of the present application, by applying the PID adjustment loop to the industrial control system, the industrial control system can dynamically adjust the control strategy according to the deviation between the process variable and the set value, so as to ensure that the process variable quickly and stably approaches the set value, maintaining both the adjustment accuracy of the PID adjustment loop and effectively balancing the contradiction between high-precision adjustment and low equipment wear, and is applicable to a variety of industrial control scenarios, having a broad application prospect.

[0081] Based on the above embodiments, in some embodiments, the industrial control system further includes a data acquisition component, which is connected to the process variable input end of the PID adjustment loop, and is used to acquire the process variable adjusted by the PID adjustment loop and transmit the acquired process variable to the process variable input end.

[0082] Exemplarily, the data acquisition component includes a plurality of sensors and a data acquisition module, which are responsible for real-time monitoring and acquisition of key variable data during the operation of the controlled device; among them, the sensors are installed on, for example, a reaction kettle or a pipeline, and are used to measure process variables such as temperature, pressure or liquid level; the sensors convert the collected physical quantity into an electrical signal and transmit the electrical signal to the data acquisition module; correspondingly, the data acquisition module receives the electrical signal from the sensor and converts it into a digital signal; the converted digital signal is transmitted to the process variable input end of the PID adjustment loop through the data acquisition component; correspondingly, the PID adjustment loop compares the received process variable with the set value, calculates the absolute value of the deviation between the process variable and the set value, and controls the adjustment instruction of the execution unit (such as a control valve) of the controlled device based on the absolute value of the deviation to maintain the process variable within the set range.

[0083] Considering that in engineering and daily life, constant pressure water supply pump groups are widely used, especially in domestic water systems, the water consumption is usually greatly affected by time periods, resulting in frequent speed-up and slow-down operations of variable frequency constant pressure water supply equipment. Such frequent operations may cause the motor current to exceed the rated value, thereby exacerbating the temperature rise of the pump group and further having an adverse impact on the service life of the pump group. Next, the application of the PID adjustment loop in constant pressure water supply adjustment is introduced through specific embodiments.

[0084] Figure 7 It is a schematic flowchart of a constant pressure water supply adjustment method provided for an exemplary embodiment of the present application. As Figure 7 shown, the constant pressure water supply adjustment method includes:

[0085] S701. Obtain the water supply pressure.

[0086] Exemplarily, Figure 8 It is a schematic diagram of a constant pressure water supply PID adjustment loop provided for an exemplary embodiment of the present application. As Figure 8As shown, the set value of the water supply pressure of the water supply pumping station is 1.2 MPa, the upper limit value of the first dead zone interval is 0.2 MPa, that is, the allowable pressure fluctuation of the pump set is ±0.2 MPa, and the upper limit value of the second dead zone interval is 0.02 MPa, that is, to ensure that the final adjustment deviation is controlled within a small range.

[0087] Exemplarily, through a data acquisition component connected to the process variable input end of the constant pressure water supply PID adjustment loop, the water supply pressure is acquired and the acquired water supply pressure is transmitted to the process variable input end.

[0088] S702. Input the water supply pressure into the PID adjustment loop. Among them, when the absolute value of the deviation between the water supply pressure and the set value of the water supply pressure exceeds the upper limit value of the first dead zone interval, the connection between the PID controller and the frequency converter is turned on, so that the frequency conversion instruction output by the PID controller is transmitted to the execution unit of the frequency converter to increase the frequency of the frequency converter; when the absolute value of the deviation belongs to the second dead zone interval, the self-circulation loop is turned on to keep the current frequency of the frequency converter unchanged.

[0089] Exemplarily, when the pump set pressure drops below 1.0 MPa, the absolute value of the deviation between the process variable and the set value will exceed 0.2 MPa. At this time, the output of the reset-set trigger will be set to 1, and the operation result of the PID controller will be transmitted to the execution unit of the frequency converter. The new absolute value of the deviation will generate a new frequency conversion instruction through the operation of the PID controller to increase the frequency of the frequency converter, so that the pump set speeds up, thereby increasing the water supply pressure; when the water supply pressure rises to 1.18 MPa, the output of HIGHLOWMON (i.e., the second signal monitoring unit) is set to 1, the reset-set trigger is reset, and the TRANSFER unit self-circulates to keep the current frequency conversion instruction unchanged, so that the frequency converter maintains the current frequency unchanged and ensures the stable operation of the motor.

[0090] In the embodiment of the present application, by introducing a PID adjustment loop into the constant pressure water supply system, precise control can be achieved within a small pressure deviation range, ensuring the stability of the water supply pressure. This stability is crucial for the normal operation of the water supply system, effectively avoiding uneven water supply or interruption caused by pressure fluctuations, thereby better meeting the water use needs of users and further improving the user experience. In addition, the PID adjustment loop can effectively filter out minute pressure fluctuations and avoid unnecessary frequent acceleration and deceleration operations. This optimized control strategy significantly reduces the number of acceleration and deceleration operations of the motor, reduces mechanical wear and motor load; due to the reduction of motor acceleration and deceleration operations, the temperature rise phenomenon of the pump set is effectively controlled, reducing the risk of equipment failure caused by overheating. This not only improves the reliability of the pump set, but also extends its service life and reduces maintenance and replacement costs.

[0091] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include common general knowledge or conventional technical means in the technical field not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A PID regulation loop, characterized in that, Comprising: A selection circuit, an arithmetic circuit, and a switching circuit connected to the selection circuit; wherein: The arithmetic circuit is configured to calculate the absolute value of the deviation between the input process variable and the set value, and transmit the absolute value of the deviation to the selection circuit; The selection circuit is configured to output a high level when the absolute value of the deviation is greater than the upper limit value of the first dead zone interval; and output a low level when the absolute value of the deviation belongs to the second dead zone interval, wherein the upper limit value of the first dead zone interval is greater than the upper limit value of the second dead zone interval; The switching circuit is configured to, when the input is a high level, conduct the connection between the PID controller included therein and the execution unit of the controlled device, so as to transmit the operation result of the PID controller to the execution unit, and the execution unit is configured to adjust the process variable based on the operation result, so that the process variable approaches the set value; when the input is a low level, conduct the self-loop, and the self-loop is used to keep the adjustment instruction of the controlled device unchanged.

2. The PID adjustment loop according to claim 1, wherein The arithmetic circuit includes a subtraction operation unit and an absolute value operation unit, wherein: The input end of the subtraction operation unit serves as the input end of the arithmetic circuit, the output end of the subtraction operation unit is connected to the input end of the absolute value operation unit, and the output end of the absolute value operation unit is connected to the input end of the selection circuit; The subtraction operation unit is configured to calculate the deviation between the process variable and the set value; The absolute value operation unit is configured to take the absolute value of the deviation to obtain the absolute value of the deviation.

3. The PID adjustment loop according to claim 1 or 2, characterized in that, The selection circuit includes a first signal monitoring unit, a second signal monitoring unit, and a reset-set flip-flop; The input ends of the first signal monitoring unit and the second signal monitoring unit are both connected to the output end of the arithmetic circuit; The first signal monitoring unit is connected to the set end of the reset-set flip-flop, and is configured to set the reset-set flip-flop to output a high level when the absolute value of the deviation is greater than the upper limit value of the first dead zone interval; The second signal monitoring unit is connected to the reset end of the reset-set flip-flop, and is configured to set the reset-set flip-flop to output a low level when the absolute value of the deviation is greater than the lower limit value of the second dead zone interval and less than the upper limit value of the second dead zone interval.

4. The PID adjustment loop according to claim 3, characterized in that, The first signal monitoring unit adopts a high-value monitoring algorithm; the second signal monitoring unit adopts a high-low value monitoring algorithm.

5. The PID adjustment loop according to claim 1 or 2, characterized in that, The switching circuit further includes a switching unit, and the input of the PID controller includes the process variable and the set value; the control end of the switching unit is connected to the output end of the selection circuit, the input end of the switching unit is connected to the output end of the PID controller, and when the input end and the output end of the switching unit are connected, the self-loop is formed; wherein: The PID controller is configured to generate an adjustment instruction according to the deviation between the process variable and the set value; The switching unit is configured to connect the input end of the switching unit to the output end of the PID controller when the output of the selection circuit is at a high level, and transmit the adjustment instruction to the execution unit; and when the output of the selection circuit is at a low level, trigger the switching unit to self-loop and keep the current adjustment instruction of the controlled device unchanged.

6. The PID adjustment loop according to claim 5, characterized in that, The switching unit is a TRANSFER unit.

7. The PID adjustment loop according to claim 1 or 2, characterized in that, The upper limit value of the first dead zone interval is set according to the dynamic response characteristics of the controlled device; and / or, the lower limit value and the upper limit value of the second dead zone interval are set according to the adjustment accuracy requirements of the controlled device.

8. An industrial control system, characterized in that, It includes the PID adjustment loop according to any one of claims 1 to 7.

9. The industrial control system according to claim 8, wherein It further includes a data acquisition component, which is connected to the process variable input end of the PID adjustment loop, and is configured to acquire the process variable adjusted by the PID adjustment loop and transmit the acquired process variable to the process variable input end.

10. A constant pressure water supply regulation method, characterized in that, Applied to the industrial control system according to claim 8 or 9, the constant pressure water supply adjustment method includes: Obtain the water supply pressure; Input the water supply pressure into the PID adjustment loop. Wherein, when the absolute value of the deviation between the water supply pressure and the set value of the water supply pressure exceeds the upper limit value of the first dead zone interval, the connection between the PID controller and the frequency converter is turned on, so that the frequency conversion instruction output by the PID controller is transmitted to the execution unit of the frequency converter to increase the frequency of the frequency converter; when the absolute value of the deviation belongs to the second dead zone interval, the self-loop circuit is turned on to keep the current frequency of the frequency converter unchanged.

Images