CN112180713A - Method for closed-loop identification of aeration process of sewage plant by taking inverse triangular wave as excitation signal - Google Patents
Method for closed-loop identification of aeration process of sewage plant by taking inverse triangular wave as excitation signal Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 71
- 238000005273 aeration Methods 0.000 title claims abstract description 45
- 230000008569 process Effects 0.000 title claims abstract description 43
- 230000005284 excitation Effects 0.000 title claims abstract description 29
- 239000010865 sewage Substances 0.000 title claims abstract description 14
- 230000006870 function Effects 0.000 claims description 14
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
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Abstract
The invention provides a method for closed-loop identification of an aeration process of a sewage plant by taking inverse triangular waves as excitation signals. The invention provides a method for identifying an aeration process by taking an inverse triangular wave signal as a closed-loop identification excitation value under the condition of ensuring normal aeration quantity of a biological reaction tank, and in the actual engineering, the method for setting a control parameter by using an identified mathematical model can reduce the error influence caused by a human experience value. Compared with the common pseudo-random signal for closed-loop identification, the method is easier to implement in practical engineering and cannot influence the production safety.
Description
Technical Field
The invention relates to a continuous process closed loop excitation signal identification technology in the fields of modeling simulation theory and technology in control science and engineering discipline.
Background
The removal of pollutants in the sewage is mainly completed in the aeration tank, so the whole process is influenced by the good and bad effect of the aeration tank. There are many variables affecting the aeration process, the most important is DO (dissolved oxygen) concentration, and reasonable control of these variables can most directly and effectively improve the treatment efficiency of the aeration tank.
In the actual operation process, the central control personnel adjust the opening of the aeration valve according to the actual operation experience of the central control personnel, so that the DO concentration value is suddenly high and suddenly low, and the fluctuation range is large.
The DO set-point control is a well-established technology, that is, a pid (proportional Integral derivative) controller controls the DO concentration in the aerobic zone to be maintained at a certain set point by adjusting the aeration rate.
The PID control is used as a control mode in a classical control theory, is widely applied to an industrial control process due to the characteristics of simple structure and convenient adjustment, is particularly suitable for a system capable of establishing a mathematical model, and is one of the main technologies of the current industrial control.
The premise for realizing accurate control is the grasp of the process model, so the identification of the process model is a key method for reasonably controlling the DO concentration and improving the treatment efficiency of the aeration tank.
Closed-loop identification is a generally accepted method in engineering and has the advantage that process models can be identified without affecting production. However, the conventional pseudo-random signal requires a professional to provide an empirical value, and has certain difficulties. A simpler excitation signal is needed in engineering.
There is a regulation of the upper and lower limits of the DO concentration during the aeration tank process. If the aerobic zone is aerated excessively, the carbon source substances stored in PAO cells are consumed excessively, and if the DO concentration is too low, denitrification reaction is generated. And the identification process is generally carried out under the condition of not influencing the process production, namely closed-loop identification is carried out while the aeration tank is in operation. Therefore, if the set value is to ensure that the normal process flow is not affected, the inverse triangular wave as the excitation signal has the advantages of being capable of restoring the DO concentration initial value compared with the oblique wave, being more suitable for practical engineering due to the fact that the inverse triangular wave has a gentle rise compared with the step wave, and being capable of reducing the aeration quantity compared with the regular triangular wave under the condition that the nitrification level is met.
Disclosure of Invention
The invention provides a method for identifying the closed loop of the aeration process of a sewage plant by taking an inverse triangular wave as an excitation signal.
In order to achieve the purpose, the technical scheme of the invention is as follows: a method for recognizing the aeration procedure of sewage plant in closed loop mode by using reverse triangular wave as exciting signal includes inputting initial set value to set up desired DO concentration value at PLC, outputting control signal to valve control box to control valve opening degree by PID controller to control DO concentration value in aerobic zone, feeding back the output value of control procedure, inputting the difference between set value and feedback value to PID controller, and calculating control signal to control valve opening degree again.
Further, the triangle wave excitation signal function may be defined as:
in the formula, the parameter a is the slope width of the inverse triangular wave; the parameter k is the slope gradient of the reverse triangular wave slope;
parameter setting principle of inverse triangular wave slope width a:
the parameter a influences the magnitude of the change in the excitation value. The setting principle is that the limit value of the parameter a cannot exceed x% of the full range of the set value, then:
in the formula, rmaxIs the full-scale range value of the set value;
and for the gradient k of the inverse triangular wave slope, according to a parameter setting principle of the parameter k, obtaining the slope k through a trial and error test under the condition that the DO concentration is limited in the aeration process, namely the DO concentration output data obtained by excitation is within a limit value.
Further, only considering the influence of the DO concentration, the aeration process is simplified as a first-order inertia link connected in series with a first-order lag link, and then the transfer function is:
the PID controller general transfer function is:
calculating K according to ZN-PID setting formulap，Ti，TdSubstituting the general transfer function into a general transfer function of the PID controller;
and carrying out a closed-loop identification experiment by using the inverse triangular wave parameters obtained by the previous setting, and substituting identification model parameters K, T and tau obtained by the particle swarm identification program into the transfer function of the transfer function controlled model to obtain a final identification model.
Further, the inverse triangular wave excitation signal should be applied at the set value of the controller, namely at the solenoid valve control cabinet PLC of the aeration system.
The aeration process of the sewage plant can be simplified into a first-order inertia link with time delay under the condition of only considering the concentration of dissolved oxygen, and the invention provides a method for identifying the aeration process by taking an inverse triangular wave signal as a closed-loop identification excitation value under the condition of ensuring the normal aeration amount of a biological reaction tank. In engineering practice, the method for setting the control parameters by identifying the obtained mathematical model can reduce the error influence caused by artificial empirical values. Compared with the common pseudo-random signal for closed-loop identification, the method is easier to implement in practical engineering and cannot influence the production safety. The invention is a research on the identification method of the sewage treatment aeration process model, which is different from the control of the model, and the mathematical model obtained by identification enables the accurate control to be more reasonable.
Drawings
Fig. 1 is a block diagram of an aeration process model identification process based on anti-triangular wave excitation.
Detailed Description
The process of the present invention will be briefly described with reference to specific examples.
The specific implementation process of the invention is as follows:
as shown in the figure, the PID control of the aeration process comprises the steps that firstly, an input value is arranged at a PLC (circle in the figure), namely, an initial set value sets a desired DO (dissolved oxygen) concentration value, a concentration value signal outputs a control signal to a valve control box through a PID controller to control the opening of a valve so as to control the DO concentration value of an aerobic zone, a control process output value, namely, the DO concentration value is fed back to the set value, the difference between the set value and the feedback value is input into the PID controller, the recalculated control signal controls the opening of the valve again, and the final output value of the system is stabilized near the set value.
The mathematical model of the controlled object can be identified through the known PID controller model and the input and output data. In the actual process, the excitation value is applied for identification, and the input and output values are always kept unchanged under the condition that the system runs stably, the controlled object model cannot be identified, the reverse triangular wave cannot influence the production process, and the excitation applied at the set value is easy to implement in engineering. Therefore, in order to avoid the influence on the production and the requirement of the upper limit and the lower limit of the concentration of the dissolved oxygen in the aeration process of the sewage plant, the excitation waveform of the closed-loop identification is set to be an inverse triangular wave.
After the triangular wave excitation signal is applied, namely the set value linearly drops to the limit value of the aeration process and then linearly rises back to the initial set value, and the opening degree of the valve of the output value is changed. And optimizing and identifying the mathematical model of the controlled aeration process by using a PSO algorithm through data generated by system oscillation, so as to calculate optimal PID control parameters according to the mathematical model and optimize the control method.
The inverse triangle wave excitation signal function of the present invention can be defined as:
in the formula, the parameter a is the slope width of the inverse triangular wave; the parameter k is the inverse triangle wave slope gradient.
The invention relates to a parameter setting principle of a reverse triangular wave slope gradient k:
the parameter k determines the rate at which the set point rises (falls) within the limits. Under the condition that the output quantity is within the set limit value, the larger k is, the faster the set value rises (falls), otherwise, the slower k is, in order to ensure the normal operation of the aeration process, the overlarge k value is not suitable to be selected, and the k value can be determined through trial and error tests as long as the influence of the control quantity output by the controller on the aeration process is within the set limit value.
The invention discloses a parameter setting principle of an inverse triangular wave slope width a:
the parameter a influences the magnitude of the change in the excitation value. The setting principle is that the limit value of the parameter a cannot exceed x% of the full range of the set value, then:
in the formula, rmaxIs the full scale value of the set point.
The sewage treatment aeration process belongs to a complex dynamic engineering system and cannot be described by an accurate mathematical model.
In order to simplify the aeration process model, under the condition of only considering the influence of DO concentration, the aeration process can be simplified into a first-order inertia link connected with a first-order lag link in series, and then the transfer function of the controlled model is as follows:
the actual model of the aeration process is not set as
The PID controller general transfer function is:
according to ZN-PID tuning formula:
Ti(integration time constant) 2 τ 20
Td(differential time constant) 0.5 τ 5
The controller is modeled as
The inverse triangular wave parameters need to be set before the closed loop identification experiment is carried out.
For the gradient k of the inverse triangular wave slope, according to the parameter setting principle of the parameter k, under the condition that the limitation of the aeration process on the DO concentration is met, that is, DO concentration output data obtained by excitation is within the limit value (the limit value is suggested to be 2-3 mg/l), an overlarge k value is not taken, and through a trial and error test, the following steps are not taken:
according to the setting principle of the width parameter a of the inverse triangle wave slope, assuming that the change range of the set value is limited not to exceed the full range (assuming the original set DO concentration is 2.5mg/l, the minimum value of the inverse triangle wave is 2mg/l, then r ismax0.5) is 50%, then
Under the noisy anti-triangular wave set value excitation closed loop identification simulation test, 300-point process output response (y) can be obtained1(k) 1, 2, 300, input data { u }1(k)，k＝1，2，...，300}。
The identification model parameters obtained by the Particle Swarm Optimization (PSO) identification procedure are
K＝101.2
T＝1007
τ＝10.7
Namely, it is
K-gain, T-inertia time, tau-lag time.
Thus, the resulting model G is identified1The method is very close to the parameters of the actual model G, and proves that the method for setting the parameters of the inverse triangular wave excitation signal is very effective in closed-loop identification of the aeration model of the sewage plant.
Claims (4)
1. A method for recognizing the aeration procedure of sewage plant in closed loop by inverse triangular wave as exciting signal includes such steps as inputting initial setting value to PID controller, setting up the desired DO concentration value, outputting control signal to valve control box via PID controller to control the opening of valve, feeding back the output value of control procedure to the setting value, inputting the difference between the setting value and feedback value to PID controller, and calculating the control signal to control the opening of valve again, applying inverse triangular wave exciting signal to the setting value of PID controller to make the linear value decrease to the limit value of aeration procedure and then increase back to initial setting value, changing the DO concentration of output value, and setting the parameters of inverse triangular wave according to the limit value of dissolved oxygen concentration in aeration procedure, and performing a closed-loop identification experiment by using the set inverse triangular wave parameters to obtain a final identification model.
2. A method for closed-loop identification of a sewage plant aeration process using an inverted triangle wave as an excitation signal according to claim 1 wherein the triangle wave excitation signal function is defined as:
in the formula, the parameter a is the slope width of the inverse triangular wave; the parameter k is the slope gradient of the reverse triangular wave slope;
parameter setting principle of inverse triangular wave slope width a:
the parameter a influences the magnitude of the change in the excitation value. The setting principle is that the limit value of the parameter a cannot exceed x% of the full range of the set value, then:
in the formula, rmaxIs the full-scale range value of the set value;
and for the gradient k of the inverse triangular wave slope, according to a parameter setting principle of the parameter k, obtaining the slope k through a trial and error test under the condition that the DO concentration is limited in the aeration process, namely the DO concentration output data obtained by excitation is within a limit value.
3. The method of claim 1, wherein the aeration process is simplified as a first-order inertia element connected in series with a first-order lag element with a transfer function of:
the PID controller general transfer function is:
calculating K according to ZN-PID setting formulap，Ti，TdSubstituting the general transfer function into a general transfer function of the PID controller;
and carrying out a closed-loop identification experiment by using the inverse triangular wave parameters obtained by the previous setting, and substituting identification model parameters K, T and tau obtained by the particle swarm identification program into the transfer function of the transfer function controlled model to obtain a final identification model.
4. The method for closed-loop identification of aeration process of sewage plants using inverse triangular wave as excitation signal according to claim 1, wherein the inverse triangular wave excitation signal is applied at controller set value, i.e. at the solenoid valve control cabinet PLC of the aeration system.
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|---|---|---|---|---|
| JP2013110909A (en) * | 2011-11-24 | 2013-06-06 | Nissan Motor Co Ltd | Motor drive and control method for the same |
| CN106054600A (en) * | 2016-05-30 | 2016-10-26 | 上海电力学院 | Trapezoidal wave signal parameter setting method of setting value excitation closed loop identification |
| CN107450310A (en) * | 2016-05-30 | 2017-12-08 | 上海明华电力技术工程有限公司 | A kind of setting value excitation closed-loop identification method of continuous process model |
| CN107565877A (en) * | 2016-06-30 | 2018-01-09 | 施耐德电气工业公司 | Method and apparatus for controlled motor |
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Application publication date: 20210105 |