CN100368048C - Fuzzy-self adjusting PID control method of extraction pot in Chinese medicine production process - Google Patents
Fuzzy-self adjusting PID control method of extraction pot in Chinese medicine production process Download PDFInfo
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Abstract
The present invention discloses a fuzzy and self-regulating PID control method of an extracting tank in the traditional Chinese medicine production process. The present invention comprises the following steps: a sensor checks the temperature and the pressure of the extracting tank; the checked temperature and the given value are compared, when the temperature is greater than the fixed value, a temperature regulating valve and a pressure regulating valve of a fuzzy control extracting tank are selected; otherwise, a temperature regulating valve and a pressure regulating valve of a self-regulating PID control extracting tank are selected. The present invention adopts the fuzzy and self-regulating PID control to control the extracting tank in the traditional Chinese medicine production process, alters the situation that the control on extract is judged by experience of workers in long term, greatly reduces the operation frequency of an actuating mechanism, avoids the frequent operation of the valves, enhances the physic liquor quality, and simultaneously reduces the production cost indirectly.
Description
Technical Field
The invention relates to a fuzzy-self-adjusting PID control method of an extraction tank in the production process of traditional Chinese medicines.
Background
In the traditional Chinese medicine extraction production process, the balance of variables such as temperature, pressure and the like in an extraction tank is difficult to control: the liquid medicine can run out when the pressure in the extraction tank is too high and the foam surface is too high, so that the extraction amount of the liquid medicine is reduced, and the evaporation process of the liquid medicine is slow when the pressure is too low; the opening of the regulating valve for controlling the interlayer pressure of the extraction tank is always too large, which can result in that the regulating time for the liquid medicine temperature to reach the equilibrium point is prolonged.
The control of the extracting tank in the traditional Chinese medicine production, especially in small and medium-sized enterprises, basically stays at the level of manual operation by virtue of the experience of workers, and a single-machine automation or conventional DCS control mode is partially adopted. In terms of a control method, a single machine working mode is only local feedback regulation control, control parameters are single and simple, the whole extraction working section is also subjected to open-loop control, the control mode is backward, errors are large, and the quality of the extracting solution is obviously difficult to ensure; conventional DCS control lacks an accurate and advanced method for detecting and controlling some key parameters, and meanwhile, the flexibility of control parameters is poor, and the overall operation safety coefficient of the system is low.
Most manufacturers who have realized the automation of traditional Chinese medicine production adopt conventional PID control, the PID control algorithm is simple and easy to realize, but the parameters of the PID control algorithm must be well set in advance and cannot be flexibly set along with the change of the parameters of a controlled object, so that the adaptability of the system to the operation working condition is poor. One of the control difficulties of the extraction tank is that: when the variety of medicinal materials in the tank changes, the dynamic characteristics of the system process change, and the PID parameters must be re-set to ensure the control quality, so that the traditional PID control is not suitable.
Disclosure of Invention
The invention aims to provide a fuzzy-self-adjusting PID control method of an extraction tank in the production process of traditional Chinese medicines, so as to solve the defect that the balance of variables such as temperature, pressure and the like in the extraction tank is difficult to control in the traditional Chinese medicine production.
In order to realize the aim, the fuzzy-self-adjusting PID control method of the extraction tank in the production process of the traditional Chinese medicine comprises the following steps:
detecting the temperature and pressure of the extraction tank by using a sensor;
comparing the detected temperature with a given value, and selecting a temperature regulating valve and a pressure regulating valve of the fuzzy control extraction tank when the temperature is greater than the given value; otherwise, selecting a temperature regulating valve and a pressure regulating valve of the self-adjusting PID control extraction tank.
In the fuzzy-self-adjusting PID control method for the extraction tank in the traditional Chinese medicine production process, the fuzzy control adopts a double-input single-output fuzzy controller, the double inputs of the fuzzy controller are the error E and the error change rate EC of temperature or pressure, and the single output is the control decision U.
The invention has the beneficial effects that: the invention adopts fuzzy-self-adjusting PID control to control the extracting tank in the production process of the traditional Chinese medicine, changes the situation that the control of the extracting solution is judged by the experience of workers for a long time, greatly reduces the action times of an actuating mechanism, avoids frequent action of a valve, improves the quality of liquid medicine, and indirectly reduces the production cost. In addition, the PID control parameter can be self-adjusted according to the alpha factor so as to adapt to the requirement of extraction control of different liquid medicines in the extraction tank, and the defect that the PID parameter needs to be re-adjusted when different liquid medicines are extracted in the existing PID control is overcome.
The invention will be further described with reference to the following drawings and specific embodiments
Drawings
Fig. 1 is a control schematic block diagram of the present invention.
Fig. 2 is a block diagram of the fuzzy-self adjusting PID control of the present invention.
Detailed Description
The control of the extraction tank in the production process of the traditional Chinese medicine is typical complex process control and has the characteristics of more variables and large disturbance. As shown in figure 1, the temperature regulating valve and the pressure regulating valve of the extraction tank are controlled by a fuzzy-self-adjusting PID control method according to the main parameters of temperature, pressure and interlayer pressure of the extraction tank so as to achieve the balance of the pressure and the temperature in the extraction tank.
The control process of the extraction tank is described in detail below: the temperature control within the extraction tank is characterized by a large hysteresis, with an equation of state approximating:
in the formula
Is the rate of temperature change, theta is the in-tank temperature, u 1 τ is a delay time for the control action to affect the temperature for the output of the regulating valve mounted on the vapor-liquid separator.
The equation of state of the internal pressure of the extraction tank is approximated as:
in the formulaIs the rate of change of the internal pressure of the tank, p is the internal pressure of the tank, u 2 The output of the valve is adjusted on the steam channel. In the equations of states (1) and (2), a T 、b T 、a P 、b P Is a structural parameter of the extraction tank. Let θ = x 1 ，p ＝x 2 The standard state equation form is written by the formulas (1) and (2):
and (3) performing Laplace transform conversion on the formula (3), and extracting a mathematical model of the temperature and the pressure in the tank as follows:
k in formula (4) a 、K b Temperature and pressure static gains, respectively, temperature delay time, T 1 Is the temperature inertia link time constant, T 2 Is the pressure inertia link time constant. It can be seen that in the extraction tankThe temperature object which is difficult to control can be approximated as a first-order inertia plus pure delay link
The fuzzy controller adopts a double-input single-output model, wherein double inputs are respectively the error E and the error change rate EC of pressure or temperature, and a single output is a control decision U. The control decision U is the control quantity of the pressure regulating valve or the temperature regulating valve, and is closely related to the error E and the error change rate EC: u depends mainly on E, and CE is just to judge the trend. For example, if E is positive, EC > 0, the controlled variable should be maximized to reduce the deviation; if EC < 0 tends to reduce the deviation, the control amount should be reduced.
The dynamic equations of the system are described by { E, EC, U }. E, EC and U are respectively as follows:
E：{PB，PM，PS，PZ，NZ，NS，NM，NB}；
EC：{PB，PM，PS，ZO，NS，NM，NB}；
U：{PB，PM，PS，ZO，NS，NM，NB}。
all the membership functions of the input and output linguistic variables are defined in the range of [ -6,6], and the membership functions of the input and the output adopt bell-shaped functions. By using a nonlinear deblurring algorithm, 8 × 7=56 fuzzy rules are established in the form of if E and EC then U, as shown in table 1.
When E represents the temperature difference in the tank AND EC represents the change rate of the temperature difference, IF the temperature difference E is a large negative value (PB) AND the change rate of the temperature difference EC is a large positive value (NB), the control quantity U of the control switch valve is positive at the moment, but the value is small (NS), AND a fuzzy rule is written, namely IF E = PB AND EC = NB TNEN U = NS
TABLE 1 fuzzy control rules Table
| EC | E | |||||||
| NB | NM | NS | NZ | PZ | PS | PM | PB | |
| NB NM NS ZO PS PM PB | PB PB PB PB PM PM PS | PB PB PM PM PM PS ZO | PM PM PS PS ZO ZO ZO | PS PS PS ZO ZO ZO NS | PS ZO ZO ZO NS NS NS | ZO ZO ZO NS NS NM NM | ZO NS NM NM NM NB NB | NS NM NM NB NB NB NB |
Self-tuning PID control: will be provided with
Discretizing, and writing a PID incremental formula:
Δu(n)＝g 0 e(n)+g 1 e(n-1)+g 2 (n-2)
wherein
In the above formula K p ，T i ，T d Respectively proportional coefficient, integral and differential time. Obtained from formula (5-7)
Considering that the general PID adjustment is adjusted according to the specific object mathematical model, it can be known from the equations (5) - (7) that when the manufacturer changes the kind of the extracted drug to cause the change of the control object, the optimum K must be sought again p ，T i ，T d And thus is rather cumbersome to use. If the PID control parameters can not be intelligently changed, the control effect is influenced. Therefore, the invention introduces an expert PID self-tuning method on the basis of the fuzzy-PID algorithm.
Defining a controllable rate α = τ/T 1 (the ratio of the pure lag time of the object to the time constant of the object is called controllable rate and is expressed by alpha), the smaller alpha is, the easier the object is controlled; the larger α, the less easily the object is controlled. The controllable rate of most controlled objects in the industrial process is less than 1, and the following expert-type PID parameter setting rules are summarized according to the PID control knowledge and by combining the characteristic parameter of the controllable rate:
rule 1 gradually decreases K from small to large according to alpha p The dynamic response speed of the system is improved, and the precision and the stability of the system are not influenced.
Rule 2 gradually increases T from small to large according to alpha i Make the integral gain K p T/2T i The reduction is less, so that the steady-state precision is ensured, and the phenomenon that the dynamic performance is deteriorated due to integral saturation and too strong integral action is avoided.
Rule 3 gradually increases T from small to large according to alpha d On the premise of not influencing the anti-interference capability of the system, the dynamic characteristic of the system can be improved by increasing the differential control action.
To facilitate the processing by the computer, the expert system tuning rules are converted into a queryable table (see table 2). Proportionality coefficient K in the table p From K p ＝K 1 K po Obtaining; k po By the formula K po ＝K 0 /K a Obtaining; t is i From T i ＝K 2 T 1 Obtaining; t is d From T d ＝K 3 τ is obtained. Therefore, only the characteristic parameter K of the controlled object is measured a ，T 1 And tau can set the PID regulator parameters.
TABLE 2PID regulator parameter Table
| α＝τ/T 1 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | 0.9 | 1.0 |
| K 0 K 1 K 2 K 3 | 13.75 0.51 0.69 0.101 | 7.06 0.52 0.695 0.103 | 4.73 0.53 0.7 0.105 | 3.645 0.54 0.71 0.107 | 2.96 0.55 0.715 0.11 | 2.5 0.56 0.716 0.112 | 2.2 0.57 0.717 0.114 | 1.93 0.58 0.718 0.116 | 1.76 0.59 0.719 0.118 | 1.62 0.60 0.72 0.12 |
Taking the temperature of the medicine liquid in the extraction tank as an example of a control object, and adopting fuzzy control when | e | > is more than or equal to 40 ℃; when the | e | is less than 40 ℃, PID control is adopted; when the types of the extracted medicinal materials are changed, only corresponding K is required to be obtained a ，T 1 τ finds the corresponding optimal PID control parameter.
Claims (7)
1. A fuzzy-self-adjusting PID control method for an extraction tank in the production process of traditional Chinese medicines comprises the following steps:
detecting the temperature and pressure of the extraction tank by using a sensor;
comparing the detected temperature with a given value, and selecting a temperature regulating valve and a pressure regulating valve of the fuzzy control extraction tank when the temperature is greater than the given value; otherwise, selecting a temperature regulating valve and a pressure regulating valve of the self-adjusting PID control extraction tank.
2. The fuzzy-self-adjusting PID control method of the extraction pot in the traditional Chinese medicine production process according to claim 1, characterized in that: the stated constant value is 40 ℃.
3. The fuzzy-self-adjusting PID control method of the extraction pot in the traditional Chinese medicine production process according to claim 1, characterized in that: when self-adjusting PID control is adopted, according to the controllable rate alpha = tau/T 1 The parameter is selected, alpha is the ratio of the pure lag time of the object to the time constant of the object, and the selection rule is as follows: gradually decreasing K from small to large according to alpha p (ii) a Gradually increasing T from small to large according to alpha i A step of,; gradually increasing T from small to large according to alpha d ，K p 、T i 、T d Respectively a proportionality coefficient, an integration time and a differentiation time.
4. The fuzzy-self-adjusting PID control method of the extracting pot in the traditional Chinese medicine production process as claimed in claim 3, characterized in that: the PID parameter lookup table is as follows:
。
5. the fuzzy-self-adjusting PID control method of the extraction pot in the traditional Chinese medicine production process as claimed in claim 1, characterized in that: the fuzzy control adopts a double-input single-output fuzzy controller, the double inputs of the fuzzy controller are the error E and the error change rate EC of the temperature or the pressure, and the single output is a control decision U.
6. The fuzzy-self-adjusting PID control method of the extracting pot in the traditional Chinese medicine production process as claimed in claim 5, characterized in that: the fuzzy sets of the E, the EC and the U are respectively as follows:
E：{PB，PM，PS，PZ，NZ，NS，NM，NB}；
EC：{PB，PM，PS，ZO，NS，NM，NB}；
U：{PB，PM，PS，ZO，NS，NM，NB}。
7. the fuzzy-self-adjusting PID control method of the extraction pot in the traditional Chinese medicine production process according to claim 5, characterized in that: the fuzzy controller establishes a fuzzy control rule table according to fuzzy rules, namely IF E = PB AND EC = NB TNEN U = NS as follows:
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| CN102419548B (en) * | 2011-11-11 | 2016-08-10 | 符红 | The medicinal liquid that waste water residual heat recycles extracts concentration automatic control system and method |
| CN103286984B (en) * | 2013-05-29 | 2015-02-25 | 中国工程物理研究院化工材料研究所 | Method for controlling depressurization of warm isostatic press |
| CN104142376B (en) * | 2014-07-17 | 2016-05-11 | 上海冷杉精密仪器有限公司 | The air-channel system control method of gas chromatograph |
| WO2020124357A1 (en) * | 2018-12-18 | 2020-06-25 | 绿烟实业（深圳）有限公司 | Temperature control device, temperature control method, and heating non-burning smoking set |
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