CN116047893A - Feedforward control method and device for valve - Google Patents

Abstract

A method of feedforward control of a valve, the method comprising: taking the first preset time length as the length of a first period, and periodically performing the following operations: according to the regulating stage of the valve, adopting a control strategy corresponding to the regulating stage to carry out first correction on a control instruction to be sent to the valve; acquiring 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 subjected to the first correction according to the deviation reference value; determining an actual control instruction according to the control instruction after the second correction; and regulating the valve according to the actual control instruction. The embodiment of the invention 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

Feedforward control method and device for valve

Technical Field

The present disclosure relates to the field of automatic control technologies, and in particular, to a method and an apparatus for feedforward control of a valve.

Background

In the conventional control scheme of the existing pulverized coal boiler, circulating fluidized bed boiler and gas boiler, a feedback control method based on PID is generally adopted for control strategies of parameters such as negative pressure, oxygen amount, load, drum water level and steam temperature. The idea of changing the control signal according to the error is applicable in most cases, however, in practical applications, due to the problems of manufacturing accuracy and post-maintenance of the valve devices involved in the adjustment, there is an execution error inevitably existing in the adjustment process of the upper and lower courses of the different opening degrees of the valve.

Because the precision of the parameters of boiler load, pressure, oxygen content and negative pressure is required to be very high under the actual operation working condition, if PID parameters in a control scheme are set based on theoretical values, the on-site valve can vibrate periodically at an indefinite time, thereby influencing the operation parameters of the boiler, causing the increase of the tangible abrasion of the valve and even causing the furnace shutdown accident in extreme cases. If the deviation between the control instruction of the valve and the actual opening feedback of the valve is too large, the control system often executes the operation of cutting off automatic control, and the on-site operator manually operates the valve to avoid the deterioration of the boiler parameters, and the valve is switched back to automatic control after the boiler parameters are stable, so that the automatic control rate of the valve cannot be effectively improved.

To address this problem, the control scheme of the related art typically selects parameters that relatively weaken the PID. Although the above problems are improved, the response speed of the PID parameters is reduced, and the parameters are out of standard when serious. In another related art, the output of the PID is regulated by introducing a command correction coefficient, however, since the correction coefficient of the valve in the opening range of 0-100% is often not linear in the regulation process, the correction coefficient of the conventional valve with the opening below 40% and above 70% is relatively large, and the middle area is relatively small. The variable working condition cannot be well adapted only by simply introducing the instruction correction coefficient, and certain limitations exist. Therefore, a method is needed that can reasonably modify valve control commands.

Disclosure of Invention

The application provides a feedforward control method and a feedforward control device for a valve, which can accurately correct a control instruction of the valve and can solve the problems of poor control stability and low self-control rate of the valve.

In one aspect, the present application provides a feedforward control method of a valve, including:

taking the first preset time length as a first period length, and periodically performing the following operations:

according to the regulating stage of the valve, adopting a control strategy corresponding to the regulating stage to carry out first correction on a control instruction to be sent to the valve;

acquiring 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 subjected to the first correction according to the deviation reference value;

determining an actual control instruction according to the control instruction after the second correction; and regulating the valve according to the actual control instruction.

Optionally, the adjusting stage includes four of: a forward growth phase, a forward callback phase, a reverse reduction phase, and a reverse callback phase;

the forward growth stage is a stage in which the process value is larger than a set value and the process value shows a growth trend;

the forward callback phase is a phase in which the process value is larger than the set value and the process value shows a decreasing trend;

the reverse reduction stage is a stage in which the process value is smaller than the set value and the process value shows a reduction trend;

the reverse callback stage is a stage in which the process value is smaller than the set value and the process value shows a growing trend;

the process value refers to a measured value of a system parameter controlled by adjusting the opening of the valve;

the set value refers to a target value of the system parameter.

Optionally, the control strategies corresponding to the forward increasing phase and the reverse decreasing phase are:

and performing deviation feedforward compensation on the control command.

Optionally, the performing offset feedforward compensation on the control command includes:

and superposing the control instruction and a first preset correction amount to obtain a control instruction after the first correction.

Optionally, the control policies corresponding to the reverse reduction stage and the reverse callback stage are:

and carrying out callback feedforward compensation on the control instruction.

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

and superposing the control instruction and a second preset correction amount to obtain a control instruction after the first correction.

Optionally, the history data is obtained by:

recording a plurality of history control instructions and control results corresponding to the history control instructions; for each recorded history control instruction, the following parameters are respectively acquired and stored: the expected opening of the historical control instruction, the adjusting direction of the historical control instruction and the deviation value between the actual opening of the valve and the expected opening after being adjusted according to the historical control instruction; wherein, adjusting the direction includes adjusting the opening degree and reducing the opening degree;

for each opening interval with preset size, searching a historical control instruction which is recorded in a preset time period and is the same as the instruction adjusting direction in the plurality of historical control instructions, wherein the expected opening belongs to the opening interval, and obtaining a deviation reference value corresponding to the opening interval in the instruction adjusting direction according to the deviation value corresponding to the searched historical control instruction;

the second correcting the control instruction after the first correcting according to the deviation reference value comprises the following steps:

and superposing the control instruction subjected to the first correction with the deviation reference value to obtain a control instruction subjected to the second correction.

Optionally, the obtaining, according to the deviation value corresponding to the found history control instruction, a deviation reference value corresponding to the opening interval in the instruction adjusting direction includes:

the following operations are performed for each opening section:

acquiring a deviation value corresponding to the searched historical control instruction from the stored parameters;

removing the maximum value and the minimum value in the deviation values; and calculating a deviation reference value corresponding to the opening interval according to the following formula:

ΔEK _x ＝limit(-k×M,ΔEK,+k×M)；

wherein Δek is the average of the deviation values; m is the median of the offset values; delta EK _x Is the deviation reference value; k is a preset median multiplying power; n is the number of the deviation values.

Optionally, the determining the actual control instruction according to the control instruction after the second correction includes:

in the first period, when the absolute value of the difference value of the expected opening is larger than a preset first difference value in the second corrected control command and the actual control command of the previous first period, the second corrected control command is used as the actual control command;

in the second corrected control instruction and the actual control instruction of the previous first period, the absolute value of the difference value of the expected opening is not larger than the preset first difference value, and when the second period is reached, the following judgment is carried out:

if the absolute value of the difference between the current process value and the set value is smaller than a preset second difference value, and the difference between the expected opening degree in the control instruction obtained after the second correction and the actual control instruction of the previous first period is larger than a preset third difference value, the control instruction obtained 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 larger than a preset second difference value, and the difference between the expected opening degree in the control instruction obtained after the second correction and the actual control instruction in the previous first period is larger than a preset fourth difference value, the control instruction obtained after the second correction is used as the actual control instruction;

if the conditions are not met, taking the actual control instruction of the previous first period as the actual control instruction of the current time;

and taking a second preset time length as the length of the second period, wherein the second preset time length is larger than the first preset time length.

In another aspect, the present application provides a control system comprising: one or more valves; and a control unit.

The control unit is arranged to perform the feed-forward control method of the valve of any one of claims 1-9 to adjust each of the valves separately.

Compared with the related art, the beneficial effects of the application include:

according to the embodiment of the application, the response speed of the valve is improved by carrying out first correction on the control instruction in stages according to the adjustment stage of the process value of the control system parameter, and the error of the valve execution control instruction is corrected by carrying out second correction on the control instruction according to the deviation reference values obtained by the plurality of historical control instructions and the corresponding control results on the basis of the first corrected control instruction, so that the accuracy of the valve control instruction can be effectively improved, the situation of automatic cutting control caused by poor valve characteristics is avoided, and the automatic control rate of the valve is improved.

Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application. Other advantages of the present application may be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The accompanying drawings are included to provide an understanding of the technical aspects of the present application, and are incorporated in and constitute a part of this specification, illustrate the technical aspects of the present application and together with the examples of the present application, and not constitute a limitation of the technical aspects of the present application.

FIG. 1 is a flow chart of a method for implementing feedforward control of a valve according to an embodiment of the present application;

FIG. 2 is a schematic diagram of an apparatus implementing a control system according to an embodiment of the present application;

FIG. 3 is a schematic diagram illustrating a first modification of a control command according to an embodiment of the present application;

FIG. 4 is a schematic diagram of staged adjustment of control commands in an embodiment of the present application;

fig. 5 is a schematic diagram of periodic determination output of a corrected instruction in the embodiment of the present application.

Reference numerals illustrate:

300. correction amount; 310. a control instruction; 320. a first corrected control instruction; 400. a forward growth phase; 410. a forward callback phase; 420. a reverse reduction phase; 430. and (5) a reverse callback stage.

Detailed Description

The present application describes a number of embodiments, but the description is illustrative and not limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are possible. Any feature or element of any embodiment may be used in combination with or in place of any other feature or element of any other embodiment unless specifically limited.

The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements of the present disclosure may also be combined with any conventional features or elements to form a unique inventive arrangement as defined in the claims. Any feature or element of any embodiment may also be combined with features or elements from other inventive arrangements to form another unique inventive arrangement as defined in the claims. Thus, it should be understood that any of the features shown and/or discussed in this application may be implemented alone or in any suitable combination. Accordingly, the embodiments are not to be restricted except in light of the attached claims and their equivalents. Further, various modifications and changes may be made within the scope of the appended claims.

Furthermore, in describing representative embodiments, the specification may have presented the method and/or process as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. Other sequences of steps are possible as will be appreciated by those of ordinary skill in the art. Accordingly, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. Furthermore, the claims directed to the method and/or process should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the embodiments of the present application.

The feedforward control method of the valve of the present application may be applied to control instructions calculated by various control methods, and the control instructions calculated by a PID control algorithm will be described below as an example.

Embodiment 1,

As shown in fig. 1, the present embodiment provides a feedforward control method of a valve, including:

taking the first preset time length as the length of a first period, and periodically performing the following operations:

s110: according to the regulating stage of the valve, adopting a control strategy corresponding to the regulating stage to carry out first correction on a control instruction to be sent to the valve;

s120: acquiring 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 subjected to the first correction according to the deviation reference value;

s130: determining an actual control instruction according to the control instruction after the second correction; and regulating the valve according to the actual control instruction.

Wherein the valve to be controlled is generally applied to a system comprising a pipeline and/or other equipment, and the opening degree of the valve can influence system parameters; the system parameters can be regulated by regulating the opening of the valve, so that the system can normally run.

Wherein, the historical control command refers to the actual control command used for adjusting the valve before.

The control command to be sent to the valve may be a control command obtained according to any one of the existing schemes.

The first correction is performed according to different control strategies in different adjusting stages, and the valve can be adjusted more specifically according to the stage in which the valve is located.

The division of different adjustment stages can be performed according to preset division rules; or directly on whether the valve itself or a system parameter associated with the valve meets the conditions of a certain regulation phase.

The historical data are different for different valves, and the obtained deviation reference values are also different, so that the second correction is closely related to the characteristics of the valves, and the control accuracy can be improved.

In an exemplary embodiment, the conditioning phase includes four of: a forward growth phase, a forward callback phase, a reverse reduction phase, and a reverse callback phase;

the forward growth stage is a stage in which the process value is larger than a set value and the process value shows a growth trend;

the forward callback phase is a phase in which the process value is larger than the set value and the process value shows a decreasing trend;

the reverse reduction stage is a stage in which the process value is smaller than the set value and the process value shows a reduction trend;

the reverse callback stage is a stage in which the process value is smaller than the set value and the process value shows a growing trend;

the process value refers to a measured value of a system parameter controlled by adjusting the opening of the valve;

the set value refers to a target value of the system parameter.

In this embodiment, since there is a certain hysteresis in the control command output by the PID control method, and the adjustment hysteresis is serious for the control loop with a large system inertia, it is necessary to perform feedforward compensation on the control command by adopting a phased control strategy according to the stage where the process value of the controlled system parameter is located.

In this embodiment, the process value is divided into 4 stages according to the relationship between the process value and the set value and the trend of the change of the process value, as shown in fig. 4, which are a forward growth stage 400, a forward callback stage 410, a reverse reduction stage 420 and a reverse callback stage 430. And correcting the PID output instructions according to the control strategies corresponding to the 4 stages.

In an exemplary embodiment, the control strategies corresponding to the forward increasing phase and the reverse decreasing phase are:

and performing deviation feedforward compensation on the control command.

In an exemplary embodiment, the performing bias feedforward compensation on the control command includes:

and superposing the control instruction and a first preset correction amount to obtain a control instruction after the first correction.

In this embodiment, at the initial stage when the process value enters the forward increasing stage or the reverse decreasing stage, because the system inertia of the control loop is large, the control command output by the PID control method has a large hysteresis, and the hysteresis of the individual loop can reach 10 minutes under the actual working condition, so that the actual door-adjusting action can be excessively adjusted due to the hysteresis, and even vibration can be caused under the individual condition. For the above reasons, a preset offset feedforward (OCB) correction amount is superimposed with the control command to obtain a first corrected control command when entering the forward increasing phase or the reverse decreasing phase, so as to open or close the valve in advance. Meanwhile, instructions are gradually recovered according to the change rate of the process value in the adjusting process, so that the condition that the process value exceeds a set value and the overshoot is caused due to the fact that the valve opening is too large is avoided.

In this embodiment, a method of weakening PID proportional integral parameters may be further used to avoid excessive overshoot of the control command based on an overlay deviation feedforward (OCB) correction.

In an exemplary embodiment, the control policies corresponding to the reverse reduction phase and the reverse callback phase are:

and carrying out callback feedforward compensation on the control instruction.

In an exemplary embodiment, the callback feedforward compensation to the control instruction includes:

and superposing the control instruction and a second preset correction amount to obtain a control instruction after the first correction.

In this embodiment, when the adjustment is performed to enter the reverse decreasing stage and the reverse callback stage, the hysteresis exists due to the large system inertia of the control loop, and the process value is already decreased, so that the process value needs to be accelerated to return to the vicinity of the set value, so as to avoid that the valve opening is excessively adjusted once the process value begins to decrease when the valve opening is continuously at the high position, so that the process value is much lower than the set value. Based on the above reasons, the preset callback feedforward (OCD) correction amount is overlapped with the control instruction in the reverse reduction stage and the reverse callback stage, and the control instruction callback is performed in advance, so that the situation that the process value is lower than the set value due to excessively small valve opening is avoided.

In this embodiment, the offset feedforward (OCB) correction amount and the callback feedforward (OCD) correction amount may be obtained by using various feedforward compensation calculation methods in the related art, which is not limited in this application.

In this embodiment, for different adjustment stages where the process value is located, the valve instruction is corrected by adopting the control strategy segment corresponding to the adjustment stage, so that the corrected control instruction can be accelerated to be close to the correct instruction in the initial stage of each adjustment stage, and the compensation instruction can be gradually retracted after the correction instruction is stabilized, so that the effects of improving the accuracy of the valve control instruction and improving the response speed of the valve can be achieved.

In one implementation of this embodiment, the output command of the PID control method is adjusted by offset feedforward (OCB) compensation and callback feedforward (OCD) compensation, and the superposition result is shown in fig. 3. When the adjustment direction of the control command 310 is the opening degree, the compensation correction amount 300 is positively overlapped to obtain a first corrected control command 320, so as to realize the quick excitation response of the control valve; when the adjustment direction of the control instruction is the opening degree reduction, reverse superposition compensation is realized, and better callback response of the control valve is realized.

In the embodiment, in the correction process of the control instruction, the periodic variation trend of the process value is calculated, and the compensation in the forward direction and the reverse direction is respectively carried out on the control instruction in each stage according to the adjustment stage where the process value is and the variation trend of the process value, so that the control instruction of the valve opening is more accurate, and the response speed of the valve can be improved.

In an exemplary embodiment, the history data is obtained by:

recording a plurality of history control instructions and control results corresponding to the history control instructions; for each recorded history control instruction, the following parameters are respectively acquired and stored: the expected opening of the historical control instruction, the adjusting direction of the historical control instruction and the deviation value between the actual opening of the valve and the expected opening after being adjusted according to the historical control instruction; wherein, adjusting the direction includes adjusting the opening degree and reducing the opening degree;

for each opening interval with preset size, searching a historical control instruction which is recorded in a preset time period and is the same as the instruction adjusting direction in the plurality of historical control instructions, wherein the expected opening belongs to the opening interval, and obtaining a deviation reference value corresponding to the opening interval in the instruction adjusting direction according to the deviation value corresponding to the searched historical control instruction;

the second correcting the control instruction after the first correcting according to the deviation reference value comprises the following steps:

and superposing the control instruction subjected to the first correction with the deviation reference value to obtain a control instruction subjected to the second correction.

In this embodiment, due to the mechanical error and the difference in installation accuracy in the adjustment process of the control system, a certain difference exists between the desired valve opening of the control command and the actual valve opening obtained by the feedback of the system. In reality, the control device cannot completely and accurately execute the instruction sent by the controller, and meanwhile, the feedback data obtained from the field cannot completely and accurately reflect the actual operation parameters of the controlled device. Therefore, in order to eliminate the influence of feedback errors caused by mechanical errors and the like on the control system, the control signal can be further corrected according to the expected opening of the valve control command and the historical data of the actual opening of the valve obtained through feedback.

In this embodiment, first, the historical data of the expected opening of the valve control command and the actual opening of the valve obtained by feedback in a preset time period are obtained, the historical data of the control command is divided into data corresponding to a plurality of opening intervals according to the intervals of the valve opening, and then the data corresponding to each opening is divided into the uplink data and the downlink data according to the adjustment direction of the control command. And then respectively calculating the up-stroke data and the down-stroke data to obtain corresponding deviation reference values of each opening interval in different instruction adjusting directions.

The up-stroke data of the valve refer to historical control instruction data corresponding to the valve when the adjusting direction of the valve is the opening degree; the valve descending data refers to historical control instruction data corresponding to the valve adjusting direction when the opening degree is reduced.

In this embodiment, compensation values corresponding to different opening intervals in the adjustment directions of the valve in the up-stroke and the down-stroke directions can be recorded. Therefore, according to the expected valve opening of the current control instruction and the adjusting direction of the control instruction, the corresponding compensation value can be determined, the control instruction of the valve is compensated, the error of the valve executing the control instruction is actively compensated, the problem of automatic control cutting caused by poor valve characteristics is solved, and the automatic control rate of the valve is improved.

In an exemplary embodiment, the obtaining, according to the deviation value corresponding to the found historical control instruction, a deviation reference value corresponding to the opening interval in the instruction adjusting direction includes:

the following operations are performed for each opening section:

acquiring a deviation value corresponding to the searched historical control instruction from the stored parameters;

removing the maximum value and the minimum value in the deviation values; and calculating a deviation reference value corresponding to the opening interval according to the following formula:

ΔEK _x ＝limit(-k×M,ΔEK,+k×M)；

wherein Δek is the average of the deviation values; m is the median of the offset values; delta EK _x Is the deviation reference value; k is a preset median multiplying power; n is the number of the deviation values.

In the first period, when the absolute value of the difference value of the expected opening is larger than a preset first difference value in the second corrected control command and the actual control command of the previous first period, the second corrected control command is used as the actual control command;

in the second corrected control instruction and the actual control instruction of the previous first period, the absolute value of the difference value of the expected opening is not larger than the preset first difference value, and when the second period is reached, the following judgment is carried out:

if the absolute value of the difference between the current process value and the set value is smaller than a preset second difference value, and the difference between the expected opening degree in the control instruction obtained after the second correction and the actual control instruction of the previous first period is larger than a preset third difference value, the control instruction obtained 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 larger than a preset second difference value, and the difference between the expected opening degree in the control instruction obtained after the second correction and the actual control instruction in the previous first period is larger than a preset fourth difference value, the control instruction obtained after the second correction is used as the actual control instruction;

if the conditions are not met, taking the actual control instruction of the previous first period as the actual control instruction of the current time;

and taking a second preset time length as the length of the second period, wherein the second preset time length is larger than the first preset time length.

In this embodiment, the inventor finds that in an actual scene, the control command adjusts the opening of the valve in real time along with the change of the difference between the process value and the set value, and the feedback parameter obtained by the control system in the adjustment process is often obtained according to the steady-state data in the actual field control system, and has a certain difference with the operation parameter of the actual equipment. To avoid such differences causing oscillations in the system control commands as the process value approaches the set point, dead zone control may be added to the control algorithm.

In this embodiment, the obtained control instruction is corrected twice in each first period to obtain a second corrected control instruction, and then whether the second corrected control instruction is output to the actual control instruction is determined by three conditions.

The first case in this embodiment includes: and when the absolute value of the difference value of the expected opening is larger than a preset first difference value (namely, when the condition 1 is met) in the control instruction after the second correction and the actual control instruction output in the previous first period, taking the control instruction after the second correction as the actual control instruction. At this time, the variation of the control command exceeds the first difference value, which means that the variation of the control command is very large and the valve opening needs to be adjusted in time, so that the control command after the second correction is directly determined as the actual control command to be output. And after the control instruction is determined, the adjustment of the first period is finished.

In this embodiment, when the amount of change of the control command is small and the second period is triggered, the second case and the third case are determined. At this time, as shown in fig. 5, since the system has been stabilized and the process value of the system parameter has been close to the set value, the amount of change in the control command is small. In order to avoid frequent action heating of the valve motor and the possibility of increasing valve abrasion, a control strategy for maintaining the output command as unchanged as possible can be adopted to periodically judge and output the corrected control command. And the length of the second period can be set longer than that of the first period, so that the adjusting frequency of the valve can be reduced.

The second case in this embodiment includes: and if the absolute value of the difference between the process value and the set value is smaller than a preset second difference (namely, the process value is in a dead zone) and the variation of the control command is larger than a preset third difference (namely, when the condition 2 is met), taking the control command after the second correction as an actual control command.

In this embodiment, the second difference is set to be relatively larger, so that the output change is relatively slow, the adjustment times of the valve are reduced, and excessive abrasion of the valve is avoided.

The third case in this embodiment includes: and if the absolute value of the difference between the process value and the set value is larger than a preset second difference (namely, the process value is out of the dead zone) and the variation of the control command is larger than a preset fourth difference (namely, when the condition 3 is met), taking the control command after the second correction as an actual control command.

In this embodiment, the fourth difference is set to be relatively smaller, so that the output change is more timely, and a better response speed of the valve is ensured.

In this embodiment, if none of the above conditions is satisfied, that is, if none of the conditions 1 to 3 is satisfied, the actual control instruction of the previous first cycle is output as the actual control instruction of this time.

In the second and third cases of the present embodiment, it is periodically determined whether or not to output the control instruction after the second correction as an actual control instruction. The output instruction is periodically judged and output, so that the opening of the valve is not adjusted when the change range of the control instruction and the process value is very small, the problem of motor overheating possibly caused by too frequent valve adjustment can be avoided, and the abrasion of the valve can be effectively relieved.

One implementation of this embodiment may be implemented by code.

The variables in the code are first described below:

IN refers to the control instruction after the second correction;

OUT refers to an actual control instruction output in the last first cycle;

EKSP1 refers to a first difference;

EKSP2 refers to the third difference;

EKSP3 refers to the fourth difference;

t1FG refers to a second periodic cycle trigger flag;

DIFG refers to a judgment flag that the process value is in a dead zone;

t1 is a second predetermined length of time.

In this embodiment, the first preset time length is set to 1 second, and the following codes are periodically executed:

t1 =10; (the second preset time period is set to 10 seconds.)

IF i1>T1 THEN

i1:＝1；

T1FG: =true; (second period trigger flag is set every 10 seconds)

ELSE

i1:＝i1+1；

END_IF

EK =abs (IN-OUT); (EK is the absolute value of the control instruction variation.)

IF EK > ABS (EKSP 1) THEN (when the instruction change amount has exceeded the first difference value, trigger the first case, output the control instruction after the second correction as the actual control instruction.)

OUT:＝IN；

ELSIF T1FG THEN (second cycle triggered.)

IF difg=true AND EK > ABS (EKSP 2) th (when the process value is in the dead zone AND the absolute value EK of the control instruction variation is greater than the third difference value, the second case is triggered AND the control instruction after the second correction is output as the actual control instruction.)

OUT:＝IN；

ELSIF DIFG = FALSE AND EK > ABS (EKSP 3) THEN (when the process value is outside the dead zone and the absolute value EK of the control instruction variation is greater than the fourth deviation, the control instruction after the second correction is output as the actual control instruction.)

OUT:＝IN；

END_IF

END_IF

In the actual execution of the present embodiment, the actual control command to be output should be kept as constant as possible. When the three conditions appear, the control instruction after the second correction is output as an actual control instruction. If none of the above conditions is satisfied, the actual control command of the previous first cycle is outputted as the actual control command of the present time.

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

In the second 1 st second after power-on, the expected opening is 1 in the obtained control instruction a after the second correction; at this time, there is no previous first cycle, and a is taken as an actual control command of the 1 st second without judgment.

In the second corrected control command b, the expected opening is 3.5, the absolute value of the difference between the expected openings of a and b is |3.5-1|=2.5, and the absolute value is larger than the first difference 2, and b is taken as the actual control command of the second 2.

And in the control command c after the second correction, wherein the obtained control command c after the second correction has the expected opening degree of 7, the absolute value of the difference between the expected opening degrees of b and c is |7-3.5|=3.5, and the absolute value is larger than the first difference value of 2, and c is taken as an actual control command of the 3 rd second.

And 4 seconds after power-on, in the obtained second corrected control instruction d, the absolute value of the difference between the expected opening degrees of 8.5, c and d is 8.5-7|=1.5, which is smaller than the first difference value of 2, and the second period is not reached at this time, and the actual control instruction c of the previous first period is taken as the actual control instruction of this time.

……

In the second corrected control command j obtained at 9 seconds after power-up, the desired opening is 9, and the absolute value of the difference from the desired opening of the previous second control command is assumed to be greater than the first difference 2, where j is taken as the actual control command at 9 seconds.

In the second corrected control command k obtained 10 seconds after power-on, the expected opening is 9.5, at this time, the second period arrives, the absolute value of the difference between j and k, which is the expected opening, is |9.5-9|=0.5, and is smaller than the first difference 2, and then the judgment is continued. Assume that the process value is 15.8, the set value is 16, |15.8-16|=0.2 is smaller than the second difference value 1, and the absolute value of the difference value 0.5 of the desired opening degrees of j and k is larger than the third difference value 0.3, and k is taken as an actual control command of 10 th seconds.

……

In the second corrected control command m obtained at 19 seconds after power-up, the desired opening is 8, and the absolute value of the difference from the desired opening of the previous second control command is assumed to be greater than the first difference 2, where m is taken as the actual control command at 19 seconds.

In the second corrected control instruction n obtained 20 seconds after power-on, the expected opening is 9, at this time, the second period arrives, the absolute value of the difference between the expected opening of m and n is |8-9|=1, and is smaller than the first difference 2, and then the judgment is continued. Assume that the process value is 17.5, the set value is 16, |17.5-16|=1.5 is larger than the second difference 1, and the absolute value 1 of the difference of the desired opening degrees of m and n is larger than the third difference 0.3, and n is taken as an actual control command of 20 th second.

Compared with the control method of the valve in the related art, the control instruction of the valve is corrected according to the feedforward control method of the valve in the embodiment of the application, so that the accuracy of the control instruction of the valve can be effectively improved, the response speed of the valve can be improved, and the automatic control rate of the valve is improved.

Embodiment II,

As shown in fig. 2, the present embodiment further provides a control system, including:

one or more valves 200; and a control unit 210.

The control unit 210 is arranged to perform the feed forward control of the valves 200 in any of the embodiments described above to adjust each of the valves separately.

Those of ordinary skill in the art will appreciate that all or some of the steps, systems, functional modules/units in the apparatus, and methods disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between the functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed cooperatively by several physical components. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as known to those skilled in the art. Computer storage media includes, but is 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 which can be used to store the desired information and which can be accessed by a computer. Furthermore, as is well known to those of ordinary skill in the art, communication media typically 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 includes any information delivery media.

Claims (10)

1. A method of feedforward control of a valve, the method comprising:

taking the first preset time length as the length of a first period, and periodically performing the following operations:

according to the regulating stage of the valve, adopting a control strategy corresponding to the regulating stage to carry out first correction on a control instruction to be sent to the valve;

acquiring 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 subjected to the first correction according to the deviation reference value;

determining an actual control instruction according to the control instruction after the second correction; and regulating the valve according to the actual control instruction.

2. The feed forward control method of claim 1, wherein the conditioning phase comprises four of: a forward growth phase, a forward callback phase, a reverse reduction phase, and a reverse callback phase;

the forward growth stage is a stage in which the process value is larger than a set value and the process value shows a growth trend;

the forward callback phase is a phase in which the process value is larger than the set value and the process value shows a decreasing trend;

the reverse reduction stage is a stage in which the process value is smaller than the set value and the process value shows a reduction trend;

the reverse callback stage is a stage in which the process value is smaller than the set value and the process value shows a growing trend;

the process value refers to a measured value of a system parameter controlled by adjusting the opening of the valve;

the set value refers to a target value of the system parameter.

3. The feed forward control method of claim 2, wherein the control strategies for the forward increasing phase and the reverse decreasing phase are:

and performing deviation feedforward compensation on the control command.

4. A feed-forward control method according to claim 3, wherein said performing offset feed-forward compensation on said control command comprises:

and superposing the control instruction and a first preset correction amount to obtain a control instruction after the first correction.

5. The feed-forward control method of claim 2, wherein the control strategies corresponding to the reverse reduction phase and the reverse callback phase are:

and carrying out callback feedforward compensation on the control instruction.

6. The feedforward control method of claim 5, wherein the callback feedforward compensation of the control instruction includes:

and superposing the control instruction and a second preset correction amount to obtain a control instruction after the first correction.

7. The feedforward control method according to claim 1, wherein the history data is obtained by:

recording a plurality of history control instructions and control results corresponding to the history control instructions; for each recorded history control instruction, the following parameters are respectively acquired and stored: the expected opening of the historical control instruction, the adjusting direction of the historical control instruction and the deviation value between the actual opening of the valve and the expected opening after being adjusted according to the historical control instruction; wherein, adjusting the direction includes adjusting the opening degree and reducing the opening degree;

for each opening interval with preset size, searching a historical control instruction which is recorded in a preset time period and is the same as the instruction adjusting direction in the plurality of historical control instructions, wherein the expected opening belongs to the opening interval, and obtaining a deviation reference value corresponding to the opening interval in the instruction adjusting direction according to the deviation value corresponding to the searched historical control instruction;

the second correcting the control instruction after the first correcting according to the deviation reference value comprises the following steps:

and superposing the control instruction subjected to the first correction with the deviation reference value to obtain a control instruction subjected to the second correction.

8. The feedforward control method according to claim 7, wherein the obtaining a deviation reference value corresponding to the opening interval in the instruction adjustment direction according to the deviation value corresponding to the found history control instruction includes:

the following operations are performed for each opening section:

acquiring a deviation value corresponding to the searched historical control instruction from the stored parameters;

removing the maximum value and the minimum value in the deviation values; and calculating a deviation reference value corresponding to the opening interval according to the following formula:

ΔEK _x ＝limit(-k×M,ΔEK,+k×M)；

wherein Δek is the average of the deviation values; m is the median of the offset values; delta EK _x Is the deviation reference value; k is a preset median multiplying power; n is the number of the deviation values.

9. The feedforward control method according to claim 1, wherein the determining the actual control command based on the second corrected control command includes:

in the first period, when the absolute value of the difference value of the expected opening is larger than a preset first difference value in the second corrected control command and the actual control command of the previous first period, the second corrected control command is used as the actual control command;

in the second corrected control instruction and the actual control instruction of the previous first period, the absolute value of the difference value of the expected opening is not larger than the preset first difference value, and when the second period is reached, the following judgment is carried out:

if the absolute value of the difference between the current process value and the set value is smaller than a preset second difference value, and the difference between the expected opening degree in the control instruction obtained after the second correction and the actual control instruction of the previous first period is larger than a preset third difference value, the control instruction obtained 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 larger than a preset second difference value, and the difference between the expected opening degree in the control instruction obtained after the second correction and the actual control instruction in the previous first period is larger than a preset fourth difference value, the control instruction obtained after the second correction is used as the actual control instruction;

if the conditions are not met, taking the actual control instruction of the previous first period as the actual control instruction of the current time;

and taking a second preset time length as the length of the second period, wherein the second preset time length is larger than the first preset time length.

10. A control system, comprising: one or more valves; control unit, its characterized in that:

the control unit is arranged to perform the feed-forward control method of the valve of any one of claims 1-9 to adjust each of the valves separately.

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