Multi-constraint nonlinear self-adaptive method and system for control valve positioner

Abstract

The invention discloses a multi-constraint nonlinear self-adaptive method and system for a control valve positioner, relates to the technical field of automatic control, and solves the problems that the existing PID algorithm depends on fixed parameters, so that the control precision of a complex nonlinear system is insufficient, the change rate of proportional parameters is too large during rapid adjustment, overshoot is easily caused, and the control precision is poor. And the system stability is influenced. A current signal of a signal generator is obtained; the microprocessor analyzes the current signal to obtain a target position value of the valve; the position of the valve is monitored in real time through a valve position sensor, and the opening degree deviation of the valve is obtained through analysis according to the target position value and the position signal of the valve; the control current of the magnet coil is calculated according to the opening degree deviation; the magnet controls the valve to move to a target position according to the control current; overlarge overshoot caused by too fast increase of a proportional link can be prevented; the system is more stable in a small deviation range; and the reasonability of proportional control parameters and the stability of the system are ensured.

Description

Technical Field

[0001] The present invention belongs to the field of automatic control, and relates to multi-constraint nonlinear adaptive technology of a control valve positioner. Specifically, it is a multi-constraint nonlinear adaptive method and system for a control valve positioner. Background Art

[0002] A control valve positioner is an important accessory of a pneumatic control valve. By receiving an input signal and converting it into corresponding actions, it ensures that the valve stops precisely at the required position. It plays a crucial role in industrial production, chemical industry, oil and gas, water supply systems, etc., and helps to ensure the stable operation of the pipeline system and the fluid control effect. Multi-constraint nonlinear adaptive control can adjust and optimize the control strategy in real time according to the actual working conditions and valve characteristics, thereby significantly improving the control accuracy of the control valve positioner. It helps to reduce the fluctuations and deviations of the fluid medium, improve the stability and reliability of the pipeline system. Multi-constraint nonlinear adaptive control can achieve more efficient and energy-saving control, help to reduce unnecessary energy consumption and waste, and improve the energy efficiency level of the entire pipeline system. At the same time, the optimized control system can better meet the control requirements in the production process, improve production efficiency and product quality.

[0003] In the prior art, when adjusting the valve positioner, the PID algorithm is generally used for adjustment control. By comprehensively considering the current error, historical error accumulation, and future error change trend to adjust the output, the controlled object can be quickly stabilized near the target value. However, the PID algorithm depends on fixed parameters, resulting in insufficient control accuracy in complex nonlinear systems, and the proportional parameter change rate is too large during rapid adjustment, which is prone to overshoot and affects the stability of the system.

[0004] The present invention provides a multi-constraint nonlinear adaptive method and system for a control valve positioner to solve the above technical problems. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention proposes a multi-constraint nonlinear adaptive method and system for a control valve positioner to solve the technical problems that the existing PID algorithm depends on fixed parameters, resulting in insufficient control accuracy in complex nonlinear systems, and the proportional parameter change rate is too large during rapid adjustment, which is prone to overshoot and affects the system stability.

[0006] To achieve the above object, the first aspect of the present invention provides a multi-constraint nonlinear adaptive method for a control valve positioner, including:

[0007] Step S1: Obtain the current signal of the signal generator; the microprocessor analyzes the current signal to obtain the target position value of the valve;

[0008] Step S2: Monitor the valve position in real time through a valve position sensor, and analyze the opening deviation of the valve based on the target position value and the position signal of the valve;

[0009] Step S3: Calculate the control current of the magnet coil according to the opening deviation;

[0010] Step S4: The magnet controls the valve to move to the target position according to the control current.

[0011] Preferably, the microprocessor analyzes the control signal to obtain the target position value of the valve, including:

[0012] When the signal generator inputs a current signal at time t, the data acquisition card in the valve positioner converts the current signal into a digital signal;

[0013] The microprocessor performs normalization processing on the digital signal to obtain the target position value of the valve. The formula expression is: Among them, V aim (t) represents the target position value of the valve at time t; I(t) represents the current signal at time t; I min is the minimum current of the current signal input by the signal generator at time t; I max is the maximum current of the current signal input by the signal generator at time t.

[0014] The present invention calculates the target position value of the valve according to the current signal input by the signal generator, laying a foundation for subsequent control of the valve, enabling the valve to finally move to the target position, and facilitating precise control of the valve position.

[0015] Preferably, the analysis of the opening deviation of the valve based on the target position value and the position signal of the valve includes:

[0016] Retrieve the position signal V obj (t) of the valve, and send the position signal to the microprocessor;

[0017] Retrieve the target position value V aim (t), compare the position signal with the target position value to obtain the difference between the two; use the difference as the opening deviation e(t).

[0018] The present invention obtains the real-time position signal of the valve, analyzes the opening deviation of the valve based on the real-time position signal and the target position value of the valve, laying a foundation for subsequent determination of the proportional control parameter according to the opening deviation, and facilitating precise control of the valve.

[0019] Preferably, the calculation of the control current of the magnet coil according to the opening deviation includes:

[0020] Retrieve the opening deviation, and through the formula Pa The proportional control parameter at time t is calculated as (t)=θ×e(t); where θ is a proportionality coefficient greater than 0.

[0021] The proportional control parameter is subjected to an upward constraint to obtain the proportional control parameter P b (t); the proportional control parameter after the upward constraint is subjected to a maximum and minimum value constraint to obtain the proportional control parameter P c (t); the proportional control parameter after the maximum and minimum value constraint is subjected to a convergence constraint to obtain the proportional control parameter P(t); the proportional control parameter P(t) is marked as the control current.

[0022] In the present invention, the upward constraint and the maximum and minimum value constraint on the proportional control parameter can prevent the excessive increase of the proportional link from causing excessive overshoot; the convergence constraint on the proportional control parameter can make the system more stable within a small deviation range; it is beneficial to ensure the rationality of the proportional control parameter and the stability of the system.

[0023] Preferably, the upward constraint on the proportional control parameter to obtain the proportional control parameter P b (t) includes:

[0024] Retrieve the proportional control parameter P a (t); obtain the rising rate of the proportional control parameter; calculate the proportional control parameter P b (t) after the upward constraint according to the rising rate; the formula expression is as follows:

[0025]

[0026] where P′ max is the maximum value of the rising rate; α is the asymmetric constraint proportionality coefficient; P a (t - 1) is the proportional control parameter at time t - 1; Δt is the time step.

[0027] Preferably, the maximum and minimum value constraint on the proportional control parameter after the upward constraint to obtain the proportional control parameter P c (t) includes:

[0028] Retrieve the proportional control parameter P b (t) after the upward constraint; calculate the proportional control parameter P c (t) using the maximum and minimum value constraint; the formula expression is as follows:

[0029]

[0030] where P max is the maximum value of the proportional control parameter; ε is the threshold value for the non - linear processing of the maximum and minimum value constraint of the proportional control parameter.

[0031] It should be noted that when the input proportional control parameter does not exceed the threshold value, the output is the same as the input; when the input proportional control parameter exceeds the threshold value, between the threshold and the limit value, the output and the input show a non-linear change, and the larger the input, the stronger the constraint on the output.

[0032] Preferably, obtaining the proportional control parameter P(t) by performing a convergence constraint on the proportional control parameter after the extreme value constraint includes:

[0033] Retrieving the proportional control parameter P c (t); calculating the proportional control parameter P(t) using the convergence constraint;

[0034]

[0035] where P aim is the set target proportional control parameter, and β is the inertia coefficient.

[0036] Preferably, the magnet controls the valve to move to the target position according to the control current, including:

[0037] Retrieving the control current, and the magnet adjusts the distance between the nozzle and the baffle according to the control current, changes the pressure difference on both sides of the spool valve, thereby controlling the movement of the spool valve;

[0038] The movement of the spool valve changes the air pressure in the pneumatic actuator, thereby generating a corresponding thrust or pull force, and finally driving the valve to move to the target position.

[0039] According to the control current, the magnet of the present invention adjusts the distance between the nozzle and the baffle, changes the pressure difference, and finally drives the valve to move to the target position; it can achieve precise control of the valve, which is beneficial to ensuring the normal operation of the system and improving product quality.

[0040] The second aspect of the present invention provides a multi-constraint non-linear adaptive system for a control valve positioner, including: a signal analysis module, a signal acquisition module connected thereto, and a terminal processing module;

[0041] Signal acquisition module: used to acquire the current signal of the signal generator;

[0042] Signal analysis module: used to analyze the current signal to obtain the target position value of the valve; real-time monitor the valve position through a valve position sensor, and analyze the opening deviation of the valve according to the target position value and the position signal of the valve; calculate the control current of the magnet coil according to the opening deviation;

[0043] Terminal processing module: used to control the valve to move to the target position according to the control current using the magnet.

[0044] A third aspect of the present invention provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor for performing the above method.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. The present invention calculates the target position value of the valve according to the current signal input by the signal generator, laying a foundation for subsequent control of the valve; enabling the valve to finally move to the target position, which is beneficial to accurately controlling the position of the valve; obtaining the real-time position signal of the valve, and analyzing the opening deviation of the valve based on the real-time position signal and the target position value, laying a foundation for subsequent determination of the proportional control parameter according to the opening deviation, which is beneficial to accurately controlling the valve.

[0047] 2. The present invention performs upward constraint and maximum value constraint on the proportional control parameter, which can prevent excessive overshoot caused by too rapid increase of the proportional link; performs convergence constraint on the proportional control parameter, which can make the system more stable within a small deviation range; is beneficial to ensuring the rationality of the proportional control parameter and the stability of the system; according to the control current, the magnet adjusts the distance between the nozzle and the baffle, changes the pressure difference, and finally drives the valve to move towards the target position; can accurately control the valve, which is beneficial to ensuring the normal operation of the system and improving the product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0049] Figure 1 It is a schematic diagram of the overall steps of the method of the present invention;

[0050] Figure 2 It is a schematic diagram of the multi-constraint non-linear self-adaptation acquisition of the method of the present invention;

[0051] Figure 3 It is a flowchart of the constraint control steps of the method of the present invention;

[0052] Figure 4 It is a comparison diagram before and after the constraint of the present invention;

[0053] Figure 5 It is a schematic diagram of the functions of the system modules of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0055] Please refer to Figure 1 , an embodiment of the first aspect of the present invention provides a multi-constrained non-linear adaptive method for a control valve positioner, including:

[0056] Step S1: Obtain the current signal (4-20 mA) of the signal generator; the microprocessor analyzes the current signal to obtain the target position value of the valve;

[0057] Step S2: Real-time monitor the valve position through the valve position sensor, and analyze the opening deviation of the valve based on the target position value and the position signal of the valve;

[0058] Step S3: Calculate the control current of the magnet coil according to the opening deviation;

[0059] Step S4: The magnet controls the valve to move to the target position according to the control current.

[0060] Please refer to Figures 2 - 4 , when the signal generator inputs a current signal at time t, the data acquisition card in the valve positioner is used to convert the current signal into a digital signal; the microprocessor normalizes the digital signal to obtain the target position value of the valve, and the formula expression is: Where, V aim (t) represents the target position value of the valve at time t; I(t) represents the current signal at time t; I min is the minimum current of the current signal input by the signal generator at time t; I max is the maximum current of the current signal input by the signal generator at time t.

[0061] Retrieve the position signal V obj (t) of the valve, and send the position signal to the microprocessor; retrieve the target position value V aim (t), compare the position signal with the target position value to obtain the difference between the two; use the difference as the opening deviation e(t);

[0062] Retrieve the opening deviation, and calculate the proportional control parameter at time t through the formula P a (t)=θ×e(t); where, θ is a proportionality coefficient greater than 0; perform an upward constraint on the proportional control parameter to obtain the proportional control parameter P b (t); perform a maximum and minimum constraint on the proportionally controlled parameter after the upward constraint to obtain the proportionally controlled parameter Pc (t); The ratio control parameter after the maximum and minimum constraints is subjected to a convergence constraint to obtain the ratio control parameter P(t); The ratio control parameter P(t) is marked as the control current.

[0063] It should be noted that the range of the input current signal is 4 - 20 mA. At the same time, the target signal and the position signal of the valve are obtained, and the opening deviation is analyzed based on the difference between the two. The ratio control parameter at time t can be calculated according to the opening deviation; The value of the ratio coefficient θ is set according to actual engineering experience.

[0064] Retrieve the ratio control parameter P a (t); Obtain the rising rate of the ratio control parameter; Calculate the ratio control parameter P b (t) after the rising constraint; The formula expression is as follows:

[0065]

[0066] Among them, P′ max is the maximum value of the rising rate; α is the asymmetric constraint ratio coefficient; P a (t - 1) is the ratio control parameter at time t - 1; Δt is the time step;

[0067] Retrieve the ratio control parameter P b (t) after the rising constraint; Calculate the ratio control parameter P c (t) using the maximum and minimum constraints; The formula expression is as follows:

[0068]

[0069] Among them, P max is the maximum value of the ratio control parameter; ε is the threshold value for the non - linear processing of the maximum and minimum constraints of the ratio control parameter;

[0070] Retrieve the ratio control parameter P c (t) after the convergence constraint; Calculate the ratio control parameter P(t) using the convergence constraint;

[0071]

[0072] Among them, P aim is the set target ratio control parameter, and β is the inertia coefficient.

[0073] It should be noted that Figure 4Before the constraint in Figure (a), the proportional control parameter showed a linear increase. After the constraint, the proportional control parameter converged; it can prevent the overshoot caused by the too rapid increase of the proportional link. In Figure (b), before the constraint, the proportional control parameter showed a linear increase. After the constraint, it can limit the parameter change rate and avoid mutation; it can enhance the stability of the adjustment control system.

[0074] For example: Figure 4 Taking Figure (a) in... as an example; when receiving a 4 - 20 mA input signal, the data acquisition card in the valve positioner converts the current signal into a digital signal; the microprocessor normalizes the digital signal to obtain the target position value V aim (t) of the valve; retrieve the position signal V obj (t) of the valve and send the position signal to the microprocessor; retrieve the target position value V aim (t), compare the position signal with the target position value to obtain the difference between the two; use the difference as the opening deviation e(t);

[0075] Calculate the proportional control parameter at time t through the formula P a (t) = θ × e(t); perform the maximum - minimum constraint on the proportional control parameter after the rising constraint to obtain the proportional control parameter P c (t); perform the convergence constraint on the proportional control parameter after the maximum - minimum constraint to obtain the proportional control parameter P(t); mark the proportional control parameter P(t) as the control current; after multi - constraint non - linear adaptation, the proportional control parameter P(t) converges, and adjust the control current according to the proportional control parameter to move the valve towards the target position.

[0076] Retrieve the control current, and the magnet adjusts the distance between the nozzle and the baffle according to the control current, changes the pressure difference on both sides of the spool valve, thereby controlling the movement of the spool valve; the movement of the spool valve changes the air pressure in the pneumatic actuator, thereby generating the corresponding thrust or pull force, and finally driving the valve to move towards the target position.

[0077] Please refer to Figure 5 , the second - aspect embodiment of the present invention provides a multi - constraint non - linear adaptive system for a control valve positioner, including: a signal analysis module, a signal acquisition module connected thereto, and a terminal processing module;

[0078] The signal acquisition module: is used to acquire the current signal of the signal generator;

[0079] Signal analysis module: used to analyze the current signal to obtain the target position value of the valve; monitor the valve position in real time through a valve position sensor, and analyze the opening deviation of the valve based on the target position value and position signal of the valve; calculate the control current of the magnet coil according to the opening deviation;

[0080] Terminal processing module: used to control the valve to move to the target position according to the control current by using the magnet.

[0081] The third aspect embodiment of the present invention provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, for executing the above method.

[0082] Some data in the above formula is calculated by removing the dimension and taking its numerical value. The formula is obtained by software simulation of a large amount of collected data to get a formula closest to the actual situation; the preset parameters and preset thresholds in the formula are set by those skilled in the art according to the actual situation or obtained through simulation of a large amount of data.

[0083] The working principle of the present invention: The present invention obtains the current signal of the signal generator; the microprocessor analyzes the current signal to obtain the target position value of the valve; monitors the valve position in real time through a valve position sensor, and analyzes the opening deviation of the valve based on the target position value and position signal of the valve; calculates the control current of the magnet coil according to the opening deviation; the magnet controls the valve to move to the target position according to the control current.

[0084] The above embodiments are only used to illustrate the technical method of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical method of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A multi-constraint nonlinear adaptive method for a control valve positioner, characterized in that, Including: Obtain the current signal of the signal generator; The microprocessor analyzes the current signal to obtain the target position value of the valve; The valve position is monitored in real time through a valve position sensor, and the opening deviation of the valve is analyzed based on the target position value and the position signal of the valve; Calculate the control current of the magnet coil according to the opening deviation; the magnet controls the valve to move to the target position according to the control current.

2. The multi-constraint non-linear adaptive method for a control valve positioner according to claim 1, wherein, The microprocessor analyzes the control signal to obtain the target position value of the valve, including: When the current signal is input by the signal generator at time t, the data acquisition card in the valve positioner is used to convert the current signal into a digital signal; The microprocessor normalizes the digital signal to obtain the target position value of the valve, and the formula expression is: Among them, V aim (t) represents the target position value of the valve at time t; I(t) represents the current signal at time t; I min is the minimum current of the current signal input by the signal generator at time t; I max is the maximum current of the current signal input by the signal generator at time t.

3. A multi-constraint non-linear adaptive method for a control valve positioner according to claim 1, characterized in that, The analysis of the opening deviation of the valve based on the target position value and the position signal of the valve includes: Retrieve the position signal V obj (t) of the valve and send the position signal to the microprocessor; Retrieve the target position value V aim (t), compare the position signal with the target position value to obtain the difference between the two; use the difference as the opening deviation e(t).

4. A multi-constraint non-linear adaptive method for a control valve positioner according to claim 1, characterized in that, The calculation of the control current of the magnet coil according to the opening deviation includes: Retrieve the opening deviation and calculate the proportional control parameter at time t through the formula P a (t) = θ × e(t); where θ is a proportionality coefficient greater than 0; The proportional control parameter P is obtained by imposing an upward constraint on the proportional control parameter b (t); the proportional control parameter after the upward constraint is subjected to a maximum and minimum constraint to obtain the proportional control parameter c (t); the proportional control parameter after the maximum and minimum constraint is subjected to a convergence constraint to obtain the proportional control parameter P(t); the proportional control parameter P(t) is marked as the control current.

5. The multi-constraint non-linear adaptive method for a control valve positioner according to claim 4, characterized in that, The proportional control parameter P is obtained by imposing an upward constraint on the control parameter of the comparative example b (t), including: Retrieve the proportional control parameter P a (t); Obtain the rising rate of the proportional control parameter; Calculate the proportional control parameter P after the rising constraint according to the rising rate b (t); The formula expression is as follows: Among them, P′ max is the maximum value of the rising rate; α is the asymmetric constraint proportionality coefficient; P a (t - 1) is the proportional control parameter at time t - 1; Δt is the time step.

6. The multi-constraint non-linear adaptive method for a control valve positioner according to claim 4, characterized in that, Performing maximum and minimum constraints on the ratio control parameter after the rising constraint to obtain the ratio control parameter P c (t), including: Retrieve the proportional control parameter P after the upward constraint b (t); Calculate the proportional control parameter P using the extreme value constraint c (t); The formula expression is as follows: where P max is the maximum value of the proportional control parameter; ε is the threshold value for the non-linear processing of the maximum and minimum constraints of the proportional control parameter.

7. A multi-constraint nonlinear adaptive method for a control valve positioner according to claim 4, characterized in that, The convergence constraint of the ratio control parameter after the minimum and maximum value constraint to obtain the ratio control parameter P(t) includes: Retrieve the proportional control parameter P after convergence constraint c (t); Calculate the proportional control parameter P(t) using the convergence constraint; Among them, P aim is the set target ratio control parameter, and β is the inertia coefficient.

8. A multi-constraint non-linear adaptive method for a control valve positioner according to claim 1, characterized in that, The control of the valve to move to the target position by the magnet according to the control current includes: Retrieve the control current, and the magnet adjusts the distance between the nozzle and the baffle according to the control current, changes the pressure difference on both sides of the spool valve, and thus controls the movement of the spool valve; The movement of the spool valve changes the air pressure in the pneumatic actuator, thereby generating a corresponding thrust or pull force, and finally driving the valve to move to the target position.

9. A multi-constraint nonlinear adaptive system for a control valve positioner, which is applied to a multi-constraint nonlinear adaptive method for a control valve positioner according to any one of claims 1-8, characterized in that, Including: A signal analysis module, and a signal acquisition module and a terminal processing module connected thereto; Signal acquisition module: used to obtain the current signal of the signal generator; Signal analysis module: used to analyze the current signal to obtain the target position value of the valve; monitor the valve position in real time through a valve position sensor, and analyze the opening deviation of the valve based on the target position value and the position signal of the valve; calculate the control current of the magnet coil according to the opening deviation; Terminal processing module: used to control the valve to move to the target position by using a magnet according to the control current.

10. An electronic device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor for performing the method according to any one of claims 1-8.

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