A feedforward control method and apparatus for a valve

Abstract

The application discloses a feedforward control method of a valve, and the method comprises the following steps: periodically performing the following operations with a first preset time length as the length of a first period: according to an adjustment stage in which the valve is located, adopting a control strategy corresponding to the adjustment stage to perform first correction on a control instruction to be sent to the valve; obtaining historical data of the valve; the historical data is a deviation reference value obtained according to a plurality of historical control instructions and respective corresponding control results; performing second correction on the control instruction after the first correction according to the deviation reference value; determining an actual control instruction according to the control instruction after the second correction; and adjusting the valve according to the actual control instruction. The embodiment of the application can accurately correct the control instruction of the valve, and can solve the problems of poor control stability and low automatic control rate of the valve.

Description

Technical Field

[0001] This article relates to the field of automatic control technology, and in particular to a valve feedforward control method and device. Background Art

[0002] Conventional control schemes for pulverized coal-fired boilers, circulating fluidized bed boilers, and gas-fired boilers typically employ PID-based feedback control strategies for parameters such as negative pressure, oxygen content, load, drum water level, and steam temperature. While this approach of adjusting control signals based on errors is generally applicable, in practice, due to manufacturing precision and subsequent maintenance issues with the valves involved in the regulation, errors are unavoidable during the adjustment of valves at various opening ranges.

[0003] Because actual operating conditions require very high precision for boiler load, pressure, oxygen content, and negative pressure, setting the PID parameters in the control solution based on theoretical values ​​can cause irregular periodic oscillations in the on-site valves, affecting boiler operating parameters, increasing tangible wear on the valves, and even causing boiler shutdowns in extreme cases. If the deviation between the valve control command and the actual valve opening feedback is too large, the control system will often execute the automatic control cutoff operation, requiring on-site operators to manually operate the valve to prevent deterioration of boiler parameters. Only after the boiler parameters stabilize can the valve be switched back to automatic control, which fails to effectively improve the valve's automatic control rate.

[0004] To address this issue, the control schemes of related technologies usually select relatively weakened PID parameters. Although this will improve the above-mentioned problem, it will also reduce the response speed of the PID parameters, and in severe cases, cause the parameters to exceed the standard. In another related technology, the output of the PID is adjusted by introducing an instruction correction coefficient. However, since the correction coefficient of the valve in the 0-100% opening range is often not linear during the adjustment process, the correction coefficient of the conventional valve opening below 40% and above 70% will be relatively large, and the correction coefficient in the middle area will be relatively small. Simply introducing an instruction correction coefficient cannot adapt well to changing working conditions and has certain limitations. Therefore, there is a need for a method that can reasonably correct the valve control instruction. Summary of the Invention

[0005] The present application provides a valve feedforward control method and device, which can accurately correct the control instructions of the valve and solve the problems of poor valve control stability and low self-control rate.

[0006] In one aspect, the present application provides a valve feedforward control method, comprising:

[0007] The first preset time length is used as the first cycle length, and the following operations are performed periodically:

[0008] According to the regulation stage of the valve, a control strategy corresponding to the regulation stage is used to perform a first correction on the control instruction to be sent to the valve;

[0009] Acquire historical data of the valve; the historical data is a deviation reference value obtained based on a plurality of historical control instructions and their corresponding control results; perform a second correction on the control instruction after the first correction based on the deviation reference value;

[0010] According to the control instruction after the second correction, an actual control instruction is determined; and the valve is adjusted according to the actual control instruction.

[0011] Optionally, the adjustment phase includes the following four: a positive growth phase, a positive callback phase, a reverse reduction phase, and a reverse callback phase;

[0012] Among them, the positive growth stage refers to the stage where the process value is greater than the set value and the process value shows an increasing trend;

[0013] The positive callback stage refers to the stage when the process value is greater than the set value and the process value shows a decreasing trend;

[0014] The reverse decrease stage refers to the stage where the process value is less than the set value and the process value shows a decreasing trend;

[0015] The reverse callback stage refers to the stage when the process value is less than the set value and the process value shows an increasing trend;

[0016] The process value refers to the measured value of the system parameter controlled by adjusting the opening of the valve;

[0017] The set value refers to the target value of the system parameter.

[0018] Optionally, the control strategies corresponding to the positive growth phase and the reverse decrease phase are:

[0019] Deviation feedforward compensation is performed on the control instruction.

[0020] Optionally, performing feedforward compensation for the control instruction includes:

[0021] The control instruction is superimposed on the first preset correction amount to obtain the control instruction after the first correction.

[0022] Optionally, the control strategies corresponding to the reverse reduction phase and the reverse callback phase are:

[0023] Performing callback feedforward compensation on the control instruction.

[0024] Optionally, performing callback feedforward compensation on the control instruction includes:

[0025] The control instruction is superimposed on the second preset correction amount to obtain the control instruction after the first correction.

[0026] Optionally, the historical data is obtained in the following manner:

[0027] Recording a plurality of historical control instructions and their corresponding control results; wherein, for each of the recorded historical control instructions, respectively obtaining and storing the following parameters: a desired opening of the historical control instruction, an adjustment direction of the historical control instruction, and a deviation between the actual opening of the valve after adjustment according to the historical control instruction and the desired opening; wherein the adjustment direction includes increasing the opening and decreasing the opening;

[0028] For each opening interval of a preset size, searching the plurality of historical control instructions for a historical control instruction recorded within a preset time period and having the same adjustment direction as the instruction, where the desired opening belongs to the opening interval, and obtaining a deviation reference value corresponding to the adjustment direction of the instruction for the opening interval based on the deviation value corresponding to the found historical control instruction;

[0029] The performing a second correction on the control instruction after the first correction according to the deviation reference value comprises:

[0030] The control instruction after the first correction is superimposed on the deviation reference value to obtain the control instruction after the second correction.

[0031] Optionally, obtaining the deviation reference value corresponding to the opening range in the instruction adjustment direction according to the deviation value corresponding to the found historical control instruction includes:

[0032] Perform the following operations for each opening interval:

[0033] In the saved parameters, obtain the deviation value corresponding to the historical control instruction found;

[0034] Remove the maximum and minimum values ​​from the deviation values; and calculate the deviation reference value corresponding to the opening range according to the following formula:

[0035]

[0036] ΔEK x =limit(-k×M,ΔEK,+k×M);

[0037] Wherein, △EK is the average value of the deviation; M is the median of the deviation; △EK x is the deviation reference value; k is the preset median multiplier; and N is the number of the deviation values.

[0038] Optionally, determining the actual control instruction according to the second revised control instruction includes:

[0039] In the first cycle, when the absolute value of the difference between the desired opening degree between the second revised control instruction and the actual control instruction of the previous first cycle is greater than a preset first difference, the second revised control instruction is used as the actual control instruction;

[0040] If the absolute value of the difference between the second corrected control instruction and the actual control instruction of the previous first cycle is not greater than the preset first difference, and the second cycle is reached, the following judgment is made:

[0041] If the absolute value of the difference between the current process value and the set value is less than a preset second difference, and the difference between the desired opening degree of the control instruction obtained after the second correction and the actual control instruction of the previous first cycle is greater than a preset third difference, the control instruction after the second correction is used as the actual control instruction;

[0042] If the absolute value of the difference between the current process value and the set value is greater than a preset second difference, and the difference between the desired opening degree of the control instruction obtained after the second correction and the actual control instruction of the previous first cycle is greater than a preset fourth difference, the control instruction after the second correction is used as the actual control instruction;

[0043] If none of the above conditions are met, the actual control instruction of the previous first cycle will be used as the actual control instruction of this cycle;

[0044] The second period is taken as the length of the second preset time, and the second preset time is greater than the first preset time.

[0045] On the other hand, the present application provides a control system, including: one or more valves; and a control unit.

[0046] The control unit is configured to execute the feedforward control method for the valve according to any one of claims 1 to 9, so as to adjust each of the valves respectively.

[0047] Compared with related technologies, the present invention has the following advantages:

[0048] The embodiment of the present application improves the response speed of the valve by performing a first correction on the control instruction in stages according to the adjustment stage of the process value of the control system parameter, and performs a second correction on the control instruction based on the deviation reference value obtained from multiple historical control instructions and their corresponding control results on the basis of the control instruction of the first correction, so as to correct the error of the valve in executing the control instruction. This can effectively improve the accuracy of the valve control instruction, avoid the situation where automatic control is cut off due to poor valve characteristics, and thus improve the self-control rate of the valve.

[0049] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. Other advantages of the present application can be realized and obtained through the solutions described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0051] Figure 1 A flow chart of a valve feedforward control method implemented in an embodiment of the present application;

[0052] Figure 2 A schematic diagram of a device for implementing a control system according to an embodiment of the present application;

[0053] Figure 3 This is a schematic diagram of performing the first correction on the control instruction in an embodiment of the present application;

[0054] Figure 4 This is a schematic diagram of adjusting the control instructions in stages in an embodiment of the present application;

[0055] Figure 5 This is a schematic diagram of periodically judging and outputting the modified instructions in an embodiment of the present application.

[0056] Description of reference numerals:

[0057] 300, correction amount; 310, control instruction; 320, control instruction after the first correction; 400, positive growth stage; 410, positive callback stage; 420, reverse reduction stage; 430, reverse callback stage. DETAILED DESCRIPTION

[0058] This application describes multiple embodiments, but this description is exemplary rather than restrictive, and it will be apparent to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described herein. Although many possible feature combinations are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0059] This application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features, and elements disclosed in this application may also be combined with any conventional features or elements to form a unique inventive solution defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other inventive solutions to form another unique inventive solution defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in this application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the appended claims and their equivalents, the embodiments are not subject to other limitations. In addition, various modifications and changes may be made within the scope of protection of the appended claims.

[0060] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps in the specific order described. As will be understood by those skilled in the art, other orders of steps are also possible. Therefore, the specific order of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to performing their steps in the order written, and those skilled in the art can readily understand that these orders can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0061] The feedforward control method of the valve of the present application can be applied to the control instructions calculated by various control methods. The control instructions calculated by the PID control algorithm will be used as an example below. Other control methods can refer to the examples below to use the feedforward control method of the valve of the present application.

[0062] Example 1

[0063] like Figure 1 As shown, this embodiment provides a feedforward control method for a valve, comprising:

[0064] The first preset time length is used as the length of the first cycle, and the following operations are performed periodically:

[0065] S110: According to the adjustment stage of the valve, a control strategy corresponding to the adjustment stage is used to perform a first correction on the control instruction to be sent to the valve;

[0066] S120: Acquire historical data of the valve; the historical data is a deviation reference value obtained based on multiple historical control instructions and their corresponding control results; perform a second correction on the control instruction after the first correction based on the deviation reference value;

[0067] S130: Determine an actual control instruction according to the second corrected control instruction; and adjust the valve according to the actual control instruction.

[0068] The valve to be controlled is usually used in a system including pipelines and / or other equipment. The opening of the valve will affect the system parameters. By adjusting the opening of the valve, the system parameters can be adjusted to ensure the normal operation of the system.

[0069] The historical control instructions refer to the actual control instructions used to adjust the valve previously.

[0070] The control instruction to be sent to the valve may be a control instruction obtained according to any existing solution.

[0071] Among them, in different adjustment stages, the first correction is performed according to different control strategies, and more targeted adjustments can be made according to the stage the valve is in.

[0072] The division of different adjustment stages can be carried out according to pre-set division rules; or the adjustment stage of the valve can be determined directly based on whether the valve itself or system parameters related to the valve meet the conditions of a certain adjustment stage.

[0073] Among them, for different valves, the historical data are different, and the obtained deviation reference values ​​are also different. Therefore, the second correction is closely related to the characteristics of the valve itself, which can improve the accuracy of control.

[0074] In an exemplary embodiment, the adjustment phase includes the following four: a positive growth phase, a positive callback phase, a reverse reduction phase, and a reverse callback phase;

[0075] Among them, the positive growth stage refers to the stage where the process value is greater than the set value and the process value shows an increasing trend;

[0076] The positive callback stage refers to the stage when the process value is greater than the set value and the process value shows a decreasing trend;

[0077] The reverse decrease stage refers to the stage where the process value is less than the set value and the process value shows a decreasing trend;

[0078] The reverse callback stage refers to the stage when the process value is less than the set value and the process value shows an increasing trend;

[0079] The process value refers to the measured value of the system parameter controlled by adjusting the opening of the valve;

[0080] The set value refers to the target value of the system parameter.

[0081] In this embodiment, since the control instructions output by the PID control method have a certain hysteresis, the adjustment hysteresis is serious for the control loop with large system inertia. Therefore, it is necessary to adopt a staged control strategy to perform feedforward compensation on the control instructions according to the stage of the process value of the controlled system parameter.

[0082] In this embodiment, the process value is divided into four stages according to the relationship between the process value and the set value and the change trend of the process value, such as Figure 4 As shown, there are respectively a positive growth phase 400, a positive callback phase 410, a reverse reduction phase 420 and a reverse callback phase 430. The PID output instructions are modified according to the control strategies corresponding to the above four phases.

[0083] In an exemplary embodiment, the control strategies corresponding to the positive growth phase and the reverse decrease phase are:

[0084] Deviation feedforward compensation is performed on the control instruction.

[0085] In an exemplary embodiment, performing feedforward compensation for the control instruction includes:

[0086] The control instruction is superimposed on the first preset correction amount to obtain the control instruction after the first correction.

[0087] In this embodiment, when the process value initially enters the positive growth phase or the negative reduction phase, the control command output by the PID control method experiences significant hysteresis due to the large system inertia of the control loop. Under actual operating conditions, the hysteresis in some loops can reach up to 10 minutes. Therefore, the actual valve adjustment action can cause excessive overshoot due to this hysteresis, and in some cases, even cause oscillation. For these reasons, when entering the positive growth phase or the negative reduction phase, a preset error feedforward (OCB) correction is superimposed on the control command to obtain the first corrected control command, thereby opening or closing the valve in advance. Simultaneously, during the adjustment process, the command is gradually recycled based on the rate of change of the process value, avoiding situations where the valve opening is too large, causing the process value to exceed the set value and resulting in excessive overshoot.

[0088] In this embodiment, a method of weakening the PID proportional integral parameter on the basis of superimposing the error feedforward (OCB) correction amount can be adopted to avoid excessive overshoot of the control command.

[0089] In an exemplary embodiment, the control strategies corresponding to the reverse reduction phase and the reverse callback phase are:

[0090] Performing callback feedforward compensation on the control instruction.

[0091] In an exemplary embodiment, performing callback feedforward compensation on the control instruction includes:

[0092] The control instruction is superimposed on the second preset correction amount to obtain the control instruction after the first correction.

[0093] In this embodiment, when the control enters the reverse reduction and reverse callback phases, the process value begins to decrease due to the large system inertia of the control loop, and hysteresis occurs. It is necessary to accelerate the process value back to near the set value to avoid excessive adjustment of the valve opening once the process value begins to decrease, causing the process value to fall significantly below the set value. For this reason, a preset callback feedforward (OCD) correction is superimposed on the control command during the reverse reduction and reverse callback phases, allowing the control command to be called back in advance. This avoids excessive reduction of the valve opening, which could cause the process value to fall significantly below the set value.

[0094] In this embodiment, a variety of feedforward compensation calculation methods in related technologies can be used to obtain the deviation feedforward (OCB) correction amount and the callback feedforward (OCD) correction amount, and this application does not impose any restrictions on this.

[0095] In this embodiment, for different adjustment stages of the process value, the control strategy corresponding to the adjustment stage is used to correct the valve instructions in segments. In the initial stage of each adjustment stage, the corrected control instructions can be accelerated to move closer to the correct instructions. After stabilization, the compensation instructions can be gradually withdrawn, which can improve the accuracy of the valve control instructions and the response speed of the valve.

[0096] In one embodiment of the present invention, the output instruction of the PID control method is adjusted by using the deviation feedforward (OCB) compensation and the callback feedforward (OCD) compensation, and the superposition result is as follows: Figure 3 When the control instruction 310 is adjusted to increase the opening, the compensation correction amount 300 is added in a positive direction to obtain the first corrected control instruction 320, thereby achieving a fast excitation response of the control valve. When the control instruction is adjusted to decrease the opening, the compensation is added in a negative direction to achieve a better callback response of the control valve.

[0097] In this embodiment, during the correction process of the control instruction, by calculating the periodic change trend of the process value, the control instruction is compensated in both positive and negative directions at each stage according to the adjustment stage of the process value and the change trend of the process value, thereby making the control instruction of the valve opening more accurate and improving the response speed of the valve.

[0098] In an exemplary embodiment, the historical data is obtained by:

[0099] Recording a plurality of historical control instructions and their corresponding control results; wherein, for each of the recorded historical control instructions, respectively obtaining and storing the following parameters: a desired opening of the historical control instruction, an adjustment direction of the historical control instruction, and a deviation between the actual opening of the valve after adjustment according to the historical control instruction and the desired opening; wherein the adjustment direction includes increasing the opening and decreasing the opening;

[0100] For each opening interval of a preset size, searching the plurality of historical control instructions for a historical control instruction recorded within a preset time period and having the same adjustment direction as the instruction, where the desired opening belongs to the opening interval, and obtaining a deviation reference value corresponding to the adjustment direction of the instruction for the opening interval based on the deviation value corresponding to the found historical control instruction;

[0101] The performing a second correction on the control instruction after the first correction according to the deviation reference value comprises:

[0102] The control instruction after the first correction is superimposed on the deviation reference value to obtain the control instruction after the second correction.

[0103] In this embodiment, mechanical errors and variations in installation precision during the control system adjustment process inevitably lead to discrepancies between the desired valve opening indicated by the control command and the actual valve opening obtained through system feedback. In reality, control devices cannot completely accurately execute the commands issued by the controller, and feedback data obtained from the field cannot fully and accurately reflect the actual operating parameters of the controlled device. Therefore, to eliminate the impact of feedback errors caused by mechanical errors and other factors on the control system, the control signal can be further corrected based on historical data on the desired valve opening indicated by the valve control command and the actual valve opening obtained through feedback.

[0104] In this embodiment, historical data on the desired valve openings and actual valve openings obtained through feedback within a preset time period are first obtained. The historical data is then divided into data corresponding to multiple opening intervals based on the valve opening intervals. Furthermore, the data corresponding to each opening is divided into upper-range data and lower-range data based on the control direction of the control command. The deviation reference values ​​corresponding to each opening interval in different command adjustment directions are then calculated for both the upper-range and lower-range data.

[0105] Among them, the valve's upper range data refers to the historical control instruction data corresponding to when the valve's adjustment direction is to increase the opening; the valve's lower range data refers to the historical control instruction data corresponding to when the valve's adjustment direction is to decrease the opening.

[0106] In this embodiment, the compensation values ​​corresponding to different valve opening ranges in both the upward and downward adjustment directions can be recorded. This allows the corresponding compensation value to be determined based on the desired valve opening and adjustment direction of the current control command, compensating the valve control command and proactively addressing errors in the valve's execution of the control command. This reduces the issue of automatic control cutoffs caused by poor valve characteristics and improves the valve's automatic control rate.

[0107] In an exemplary embodiment, obtaining the deviation reference value corresponding to the opening range in the instruction adjustment direction according to the deviation value corresponding to the historical control instruction found includes:

[0108] Perform the following operations for each opening interval:

[0109] In the saved parameters, obtain the deviation value corresponding to the historical control instruction found;

[0110] Remove the maximum and minimum values ​​from the deviation values; and calculate the deviation reference value corresponding to the opening range according to the following formula:

[0111]

[0112] ΔEK x =limit(-k×M,ΔEK,+k×M);

[0113] Wherein, △EK is the average value of the deviation; M is the median of the deviation; △EK x is the deviation reference value; k is the preset median multiplier; and N is the number of the deviation values.

[0114] In the first cycle, when the absolute value of the difference between the desired opening degree between the second revised control instruction and the actual control instruction of the previous first cycle is greater than a preset first difference, the second revised control instruction is used as the actual control instruction;

[0115] If the absolute value of the difference between the second corrected control instruction and the actual control instruction of the previous first cycle is not greater than the preset first difference, and the second cycle is reached, the following judgment is made:

[0116] If the absolute value of the difference between the current process value and the set value is less than a preset second difference, and the difference between the desired opening degree of the control instruction obtained after the second correction and the actual control instruction of the previous first cycle is greater than a preset third difference, the control instruction after the second correction is used as the actual control instruction;

[0117] If the absolute value of the difference between the current process value and the set value is greater than a preset second difference, and the difference between the desired opening degree of the control instruction obtained after the second correction and the actual control instruction of the previous first cycle is greater than a preset fourth difference, the control instruction after the second correction is used as the actual control instruction;

[0118] If none of the above conditions are met, the actual control instruction of the previous first cycle will be used as the actual control instruction of this cycle;

[0119] The second period is taken as the length of the second preset time, and the second preset time is greater than the first preset time.

[0120] In this embodiment, the inventors discovered through research that, in real-world scenarios, control instructions adjust the valve opening in real time as the difference between the process value and the setpoint changes. However, during this adjustment, the feedback parameters obtained by the control system are often derived from steady-state data from the actual on-site control system, which can differ somewhat from the actual operating parameters of the equipment. To prevent this discrepancy from causing system control instructions to oscillate when the process value approaches the setpoint, deadband control can be incorporated into the control algorithm.

[0121] In this embodiment, the obtained control instruction is corrected twice in each first cycle to obtain a second corrected control instruction, and then three conditions are used to determine whether to output the second corrected control instruction to the actual control instruction.

[0122] In the first case of this embodiment, when the absolute value of the difference between the desired valve opening between the second revised control instruction and the actual control instruction output in the previous first cycle is greater than a preset first difference (i.e., condition 1 is satisfied), the second revised control instruction is used as the actual control instruction. At this point, the change in the control instruction has exceeded the first difference, indicating that the change in the control instruction is significant and requires timely adjustment of the valve opening. Therefore, the second revised control instruction is directly determined as the actual control instruction and output. After the control instruction is determined, the adjustment of the first cycle is completed.

[0123] In this embodiment, when the change in the control instruction is very small and the second cycle is triggered, the second and third cases are judged. Figure 5 As shown, at this point, the system has stabilized and the process values ​​of the system parameters are close to the set values, so the control command changes very little. To avoid frequent valve motor operation, which can cause heating and increased valve wear, a control strategy can be used to maintain the output command as unchanged as possible, periodically determining and outputting the corrected control command. Alternatively, the second cycle can be set longer than the first to reduce the frequency of valve adjustments.

[0124] The second situation in this embodiment includes: if the absolute value of the difference between the process value and the set value is less than the preset second difference (that is, the process value is in the dead zone) and the change in the control instruction at this time is greater than the preset third difference (that is, when condition 2 is met), then the control instruction after the second correction is used as the actual control instruction.

[0125] In this embodiment, the second difference is set to be relatively large, which can make the output change relatively slow, reduce the number of valve adjustments, and avoid excessive wear of the valve.

[0126] The third situation in this embodiment includes: if the absolute value of the difference between the process value and the set value is greater than the preset second difference (that is, the process value is outside the dead zone) and the change in the control instruction at this time is greater than the preset fourth difference (that is, when condition 3 is met), then the control instruction after the second correction will be used as the actual control instruction.

[0127] In this embodiment, the fourth difference is set to be relatively small, which can make the output change more timely and ensure that the valve has a better response speed.

[0128] In this embodiment, if none of the above conditions are met, that is, if none of conditions 1-3 are met, the actual control instruction of the previous first cycle is output as the actual control instruction of this time.

[0129] In the second and third cases of this embodiment, a periodic determination is made as to whether the second revised control command should be output as the actual control command. By periodically determining and outputting the output command, the valve opening is not adjusted when the range of variation between the control command and the process value is very small. This prevents motor overheating caused by excessive valve adjustment and effectively reduces valve wear.

[0130] An implementation of this embodiment can be implemented through code.

[0131] The following first explains the variables in the code:

[0132] IN refers to the control instruction after the second revision;

[0133] OUT refers to the actual control instruction output in the previous first cycle;

[0134] EKSP1 refers to the first difference;

[0135] EKSP2 refers to the third difference;

[0136] EKSP3 refers to the fourth difference;

[0137] T1FG refers to the second cycle trigger flag;

[0138] DIFG refers to the judgment sign that the process value is in the dead zone;

[0139] T1 refers to a second preset time length.

[0140] In this embodiment, the first preset time length is set to 1 second, and the following code is executed periodically:

[0141] T1:=10; (The second preset time length is set to 10 seconds.)

[0142] IF i1>T1 THEN

[0143] i1:=1;

[0144] T1FG:=TRUE; (set the second cycle trigger flag every 10 seconds)

[0145] ELSE

[0146] i1:=i1+1;

[0147] END_IF

[0148] EK: = ABS (IN-OUT); (EK is the absolute value of the control instruction change.)

[0149] IF EK>ABS(EKSP1) THEN (When the command change exceeds the first difference, the first condition is triggered and the second corrected control command is output as the actual control command.)

[0150] OUT:=IN;

[0151] ELSIF T1FG THEN (The second cycle loop is triggered.)

[0152] IF DIFG=TRUE AND EK>ABS(EKSP2) THEN (When the process value is within the dead band and the absolute value EK of the control instruction change is greater than the third difference, the second condition is triggered and the second corrected control instruction is output as the actual control instruction.)

[0153] OUT:=IN;

[0154] ELSIF DIFG = FALSE AND EK > ABS(EKSP3) THEN (When the process value is outside the dead band and the absolute value EK of the control command change is greater than the fourth deviation, the control command after the second correction is output as the actual control command.)

[0155] OUT:=IN;

[0156] END_IF

[0157] END_IF

[0158] During the actual implementation of this embodiment, the actual control instructions output should be maintained as unchanged as possible. When the above three situations occur, the second revised control instructions are output as the actual control instructions. If none of the above conditions are met, the actual control instructions of the previous first cycle are output as the actual control instructions for this time.

[0159] In one implementation of this embodiment, it is assumed that the second period is 10 seconds, the first period is 1 second, and the first difference is 2.

[0160] In the first second after power-on, the second corrected control instruction a is obtained, and the expected opening is 1; at this time, there is no previous first cycle, and no judgment is made, and a is used as the actual control instruction for the first second.

[0161] In the second second after power-on, the second corrected control instruction b is obtained, and the expected opening is 3.5. The absolute value of the difference between the expected openings in a and b is |3.5-1|=2.5, which is greater than the first difference 2. b is used as the actual control instruction for the second second.

[0162] 3 seconds after power-on, the second corrected control instruction c is obtained, the expected opening is 7, the absolute value of the difference between the expected openings in b and c is |7-3.5|=3.5, which is greater than the first difference 2, and c is used as the actual control instruction for the 3rd second.

[0163] 4 seconds after power-on, the second corrected control instruction d is obtained, and the expected opening is 8.5. The absolute value of the difference between the expected openings in c and d is |8.5-7|=1.5, which is less than the first difference 2. At this time, the second cycle has not arrived, and the actual control instruction c of the previous first cycle is used as the actual control instruction this time.

[0164] …

[0165] At 9 seconds after power-on, the second corrected control instruction j is obtained, and the expected opening is 9. Assuming that the absolute value of the difference between the expected opening and the control instruction of the previous second is greater than the first difference 2, j is used as the actual control instruction of the 9th second.

[0166] Ten seconds after power-on, the second corrected control command k indicates a desired opening of 9.5. At this time, the second cycle arrives, and the absolute value of the difference between the desired openings in j and k is |9.5-9| = 0.5, which is less than the first difference of 2. Therefore, the judgment continues. Assuming that the process value is 15.8 and the set value is 16, |15.8-16| = 0.2 is less than the second difference of 1. Furthermore, the absolute value of the difference between the desired openings in j and k, 0.5, is greater than the third difference of 0.3. Therefore, k is used as the actual control command for the 10th second.

[0167] …

[0168] 19 seconds after power-on, the second corrected control instruction m is obtained, and the expected opening is 8. Assuming that the absolute value of the difference between the expected opening and the control instruction of the previous second is greater than the first difference 2, m is used as the actual control instruction of the 19th second.

[0169] At 20 seconds after power-on, the second corrected control command n indicates a desired opening of 9. At this time, the second cycle arrives, and the absolute value of the difference between the desired openings in m and n is |8 - 9| = 1, which is less than the first difference of 2. Therefore, the judgment continues. Assuming that the process value is 17.5 and the set value is 16, |17.5 - 16| = 1.5, which is greater than the second difference of 1. Furthermore, the absolute value of the difference between the desired openings in m and n, 1, is greater than the third difference of 0.3. Therefore, n is used as the actual control command for the 20th second.

[0170] It can be seen that compared with the valve control method in the related art, correcting the valve control instruction according to the valve feedforward control method in the embodiment of the present application can effectively improve the accuracy of the valve control instruction and increase the response speed of the valve, thereby improving the self-control rate of the valve.

[0171] Example 2

[0172] like Figure 2 As shown, this embodiment also provides a control system, including:

[0173] One or more valves 200 ; a control unit 210 .

[0174] The control unit 210 is configured to perform the feedforward control method for the valves 200 in any of the above embodiments to adjust each valve separately.

[0175] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As is well known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable, and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those skilled in the art that communication media generally embodies computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A feedforward control method for a valve, the method comprising: The first preset time length is used as the length of the first cycle, and the following operations are performed periodically: According to the regulation stage of the valve, a control strategy corresponding to the regulation stage is used to perform a first correction on the control instruction to be sent to the valve; Acquire historical data of the valve; the historical data is a deviation reference value obtained based on a plurality of historical control instructions and their corresponding control results; performing a second correction on the control instruction after the first correction according to the deviation reference value; Determine the actual control instructions based on the second revised control instructions; adjusting the valve according to the actual control instruction; Determining the actual control instruction according to the second revised control instruction includes: In the first cycle, when the absolute value of the difference between the desired opening degree between the second revised control instruction and the actual control instruction of the previous first cycle is greater than a preset first difference, the second revised control instruction is used as the actual control instruction; If the absolute value of the difference between the second corrected control instruction and the actual control instruction of the previous first cycle is not greater than the preset first difference, and the second cycle is reached, the following judgment is made: If the absolute value of the difference between the current process value and the set value is less than a preset second difference, and the difference between the desired opening degree of the control instruction obtained after the second correction and the actual control instruction of the previous first cycle is greater than a preset third difference, the control instruction after the second correction is used as the actual control instruction; If the absolute value of the difference between the current process value and the set value is greater than a preset second difference, and the difference between the desired opening degree of the control instruction obtained after the second correction and the actual control instruction of the previous first cycle is greater than a preset fourth difference, the control instruction after the second correction is used as the actual control instruction; If none of the above conditions are met, the actual control instruction of the previous first cycle will be used as the actual control instruction of this cycle; In which, a second preset time length is used as the length of the second cycle, and the second preset time length is greater than the first preset time length; the process value refers to the measured value of the system parameter controlled by adjusting the opening of the valve; and the set value refers to the target value of the system parameter.

2. The feedforward control method according to claim 1, characterized in that: The adjustment phase includes the following four stages: positive growth phase, positive callback phase, reverse reduction phase, and reverse callback phase; Among them, the positive growth stage refers to the stage where the process value is greater than the set value and the process value shows an increasing trend; The positive callback stage refers to the stage when the process value is greater than the set value and the process value shows a decreasing trend; The reverse decrease stage refers to the stage where the process value is less than the set value and the process value shows a decreasing trend; The reverse callback stage refers to the stage when the process value is less than the set value and the process value shows an increasing trend.

3. The feedforward control method according to claim 2, characterized in that: The control strategies corresponding to the positive growth phase and the reverse reduction phase are: Deviation feedforward compensation is performed on the control instruction.

4. The feedforward control method according to claim 3, characterized in that: The performing feedforward compensation for the deviation of the control instruction includes: The control instruction is superimposed on the first preset correction amount to obtain the control instruction after the first correction.

5. The feedforward control method according to claim 2, characterized in that: The control strategies corresponding to the forward callback stage and the reverse callback stage are: Performing callback feedforward compensation on the control instruction.

6. The feedforward control method according to claim 5, characterized in that: The performing callback feedforward compensation on the control instruction includes: The control instruction is superimposed on the second preset correction amount to obtain the control instruction after the first correction.

7. The feedforward control method according to claim 1, characterized in that: The historical data is obtained in the following way: Recording a plurality of historical control instructions and their corresponding control results; wherein, for each of the recorded historical control instructions, respectively obtaining and storing the following parameters: a desired opening of the historical control instruction, an adjustment direction of the historical control instruction, and a deviation between the actual opening of the valve after adjustment according to the historical control instruction and the desired opening; wherein the adjustment direction includes increasing the opening and decreasing the opening; For each opening interval of a preset size, searching the plurality of historical control instructions for a historical control instruction recorded within a preset time period and having the same adjustment direction as the instruction, where the desired opening belongs to the opening interval, and obtaining a deviation reference value corresponding to the adjustment direction of the instruction for the opening interval based on the deviation value corresponding to the found historical control instruction; The performing a second correction on the control instruction after the first correction according to the deviation reference value comprises: The control instruction after the first correction is superimposed on the deviation reference value to obtain the control instruction after the second correction.

8. The feedforward control method according to claim 7, characterized in that: The step of obtaining the deviation reference value corresponding to the opening range in the instruction adjustment direction according to the deviation value corresponding to the historical control instruction found includes: Perform the following operations for each opening interval: In the saved parameters, obtain the deviation value corresponding to the historical control instruction found; Remove the maximum and minimum values ​​from the deviation values; and calculate the deviation reference value corresponding to the opening range according to the following formula: ； ； Wherein, ΔEK is the average value of the deviation value; ΔEK i is the i-th deviation value corresponding to the opening interval; M is the median of the deviation value; △EK x is the deviation reference value; k is the preset median multiplier; and N is the number of the deviation values.

9. A control system comprising: One or more valves; a control unit, characterized in that: The control unit is configured to execute the feedforward control method for the valve according to any one of claims 1 to 8, so as to adjust each of the valves respectively.

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