Self-tuning method for parameters of valve positioner

Abstract

The invention relates to a valve positioner parameter self-tuning method. The method comprises the steps of positioner control parameter calculation, PID parameter calculation and maximum overshoot calculation. For different valves or executing mechanisms, valve position information is collected in real time, and needed valve position control values are determined to serve as positioner control parameters; pID parameters are calculated through a dynamic step setting method according to the positioner control parameters; in the setting process, a valve position feedback value is obtained in real time, the overshoot amount is calculated, the valve positioner controls the valve to be stabilized within the preset precision range through the PID algorithm and the maximum overshoot amount, control parameters, PID parameters and the maximum overshoot amount needed by the positioner can be rapidly calculated, the parameters calculated through the method are substituted into the algorithm, and therefore the control precision of the valve positioner is improved. And the system can be automatically adjusted and controlled when parameters change or external disturbance influences, so that the stability and the control precision of the system are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of intelligent valve positioners, and in particular relates to a method for self-tuning parameters of a valve positioner. Background Art

[0002] Intelligent valve positioner is a remote control positioning device used for the same type of valves with the same actuator. However, it is affected by nonlinear time-varying factors such as single-acting, double-acting, linear travel, angular travel, gas compressibility, friction between cylinder and pipeline media, etc., and requires reasonable self-tuning methods and self-tuning procedures to obtain relevant parameters in order to achieve high-precision static and dynamic control of the positioner. When the positioner is self-tuned, if the method is unreasonable and the calculation of the parameters to be tuned is inaccurate, it will cause the positioner control to oscillate or lag for a long time. The self-tuning of such positioners on the market generally takes about 3-5 minutes, and the accuracy of one-time tuning is difficult to meet the needs of complex sites, resulting in the positioner having to be repeatedly self-tuned after installation on site. This step will cost engineering and technical personnel a lot of debugging time, and will also affect the real-time control accuracy of the positioner.

[0003] For example, the patent with patent number CN103775712B involves actuator type setting, actuator direction setting, travel range setting, maximum speed setting, medium speed setting, and minimum speed setting. However, this setting method still does not involve positioner control parameter calculation, PID parameter calculation, and maximum overshoot calculation. Therefore, a more comprehensive and rapid self-tuning method for valve positioner parameters is urgently needed. Summary of the invention

[0004] The present invention provides a method for self-tuning valve positioner parameters to provide positioner control parameter calculation, PID parameter calculation, and maximum overshoot calculation, thereby solving the technical problems existing in the background technology.

[0005] The technical solution of the present invention is as follows: a method for self-tuning parameters of a valve positioner, wherein the valve positioner has a one-key tuning function for completing all tuning work, and the one-key tuning function includes: positioner control parameter calculation, PID parameter calculation, and maximum overshoot calculation;

[0006] The positioner control parameter calculation includes: the valve positioner controls the valve operation with different valve position control values, collects valve position information in real time, and determines the required valve position control value as the positioner control parameter;

[0007] The PID parameter calculation includes: the valve positioner determines the PID parameters by a dynamic step setting method according to the positioner control parameters;

[0008] The maximum overshoot calculation includes: the valve positioner uses the overshoot to calculate the valve position control value to control the valve operation; when the valve reaches the preset position, the valve positioner uses the valve position control value that controls the valve to stabilize at the preset position to control the valve position stability; the valve positioner detects the farthest valve position feedback value that exceeds the preset position farthest during the valve stabilization process; the maximum overshoot is the absolute value of the difference between the farthest valve position feedback value and the preset position.

[0009] Furthermore, the positioner control parameter calculation includes in sequence: startup control value calculation, exhaust control value calculation, valve position feedback value calculation when the membrane head is full of gas, top impact control value calculation, full closing time calculation and full opening time calculation.

[0010] Further, the startup control value calculation includes:

[0011] The valve positioner controls the valve to exhaust until the valve position is stable, and the valve position feedback value at this time is recorded as the initial valve position feedback value;

[0012] The valve positioner continuously increases the control value in proportion to the initial valve position control value until the valve position starts to change. The control value when the valve position starts to change is recorded as the minimum start control value.

[0013] Furthermore, the exhaust control value calculation includes:

[0014] The valve positioner continuously reduces the control value based on the minimum start-up control value until the valve position is zero, and the control value at this time is recorded as the exhaust control value.

[0015] Furthermore, the calculation of the valve position feedback value when the membrane head is filled with gas includes:

[0016] The valve positioner controls the operation of the valve with the maximum valve position control value until the valve position is stable. The valve position feedback value at this time is recorded as the valve position feedback value when the membrane head is filled with gas.

[0017] Furthermore, the calculation of the top impact control value includes:

[0018] The valve positioner continuously increases the control value based on the minimum start-up control value until the valve position reaches the maximum, and the control value at this time is used as the top control value.

[0019] Furthermore, the full closing time calculation includes:

[0020] The valve positioner controls the valve operation with the exhaust control value until the valve position feedback value reaches the initial valve position feedback value, and records the exhaust initial time and the exhaust end time respectively, and the difference between the exhaust initial time and the exhaust end time is the full closing time.

[0021] Furthermore, the full-open time calculation includes:

[0022] The valve positioner controls the operation of the valve with the top impact control value until the valve position feedback value reaches the valve position feedback value when the membrane head is filled with air, and records the initial inflation time and the final inflation time respectively, and the difference between the initial inflation time and the final inflation time is the full opening time.

[0023] Further, the valve positioner determines PID parameters according to the positioner control parameters by a dynamic step setting method, including:

[0024] The valve positioner uses the top control value as a step input, controls the valve operation through an open-loop control method, and records the actual valve position, the target valve position and the actual time during the operation time, wherein the difference between the actual valve position and the target valve position is the actual error, and the ratio of the actual error to the actual time is used as the change rate, and the maximum value of the change rate is determined during the operation time;

[0025] In the step response curve, at the coordinate point where the maximum value of the rate of change corresponds to the actual time, a tangent is established with the maximum value of the rate of change as the slope. The intersection of the tangent and the X-axis is the lag time, and the intersection of the tangent and the Y-axis is the gain.

[0026] Determine PID parameters based on gain and lag time.

[0027] Furthermore, the maximum overshoot calculation includes:

[0028] The valve position feedback value is divided into equal unit intervals to determine the stable control value of the maximum value of each unit interval, wherein the preset position is the maximum value of one of the unit intervals, and the valve position control value of the preset position is the stable control value of the corresponding maximum value of the unit interval;

[0029] During the inflation process, the overshoot calculation valve position control value is the product of the top control value and the inflation setting ratio, and the inflation setting ratio is greater than 1;

[0030] During the exhaust process, the overshoot calculation valve position control value is the product of the exhaust control value and the exhaust setting ratio, and the exhaust setting ratio is less than 1.

[0031] Beneficial effects of the present invention: The method of the present invention can quickly adjust the positioner control parameters, PID parameters, and maximum overshoot, which is more comprehensive and fast, and can meet complex working conditions on site. In terms of operation, only one key adjustment function button needs to be pressed to complete all adjustments, and the operation is more convenient. The method of the present invention can quickly calculate the positioner control parameters, PID parameters, and maximum overshoot. The parameters calculated by the method are substituted into the algorithm, which can ensure that the system automatically adjusts the control when the parameters change or are affected by external disturbances, thereby ensuring the stability and control accuracy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The invention discloses an overall flow chart of a method for self-tuning parameters of a valve positioner. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. The described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0034] In the technical solution of the present invention, Figure 1 The following is an overall flow chart of a specific process of a valve positioner parameter self-tuning method according to the present invention. Figure 1 As shown, the present invention is specifically as follows:

[0035] A method for self-tuning parameters of a valve positioner, wherein the valve positioner has a one-key tuning function for completing all parameter calculations used in valve control, wherein the one-key tuning function includes: positioner control parameter calculation, PID parameter calculation, and maximum overshoot calculation. The valve positioner can be a non-contact positioner with valve position feedback and valve position control functions, and its structure is a conventional technical means in the art, so it will not be described in detail here.

[0036] The positioner control parameter calculation includes: the valve positioner controls the valve operation with different valve position control values, collects valve position information in real time, and determines the required valve position control value as the positioner output parameter.

[0037] Specifically, the following are performed in sequence: calculation of the start control value, calculation of the exhaust control value, calculation of the valve position feedback value when the membrane head is filled with gas, calculation of the top control value, calculation of the full-close time and calculation of the full-open time.

[0038] The PID parameter calculation includes: the valve positioner determines the PID parameters by a dynamic step setting method according to the positioner control parameters;

[0039] The maximum overshoot calculation includes: the valve positioner uses the overshoot to calculate the valve position control value to control the valve operation; when the valve reaches a preset position, the valve positioner uses the valve position control value that controls the valve to stabilize at the preset position to control the valve position stability; the valve positioner detects the valve position feedback value when the valve is stopped; the maximum overshoot is the absolute value of the difference between the valve position feedback value and the preset position.

[0040] like Figure 1 As shown, the steps of the specific embodiment of the present invention are as follows:

[0041] Step 1: The valve positioner controls the valve to exhaust until the valve position is stable, and the valve position feedback value at this time is recorded as the initial valve position feedback value.

[0042] First, the regulating valve is exhausted. When the valve position of the regulating valve is stable, the feedback value of the initial valve position of the regulating valve is obtained by sampling and recorded as the initial valve position feedback value.

[0043] Step 2: The valve positioner continuously increases the control value in proportion to the initial valve position control value until the valve position starts to change. The control value when the valve position starts to change is recorded as the minimum start control value.

[0044] On the basis of the stable position of the valve position in the first step, the positioner gives an initial valve position control value DAC value, increases the initial valve position control value in a proportional manner, and quickly obtains the minimum starting value DAC that can push the valve begin .

[0045] Step 3: The valve positioner continuously reduces the control value based on the minimum start-up control value until the valve position is zero. The control value at this time is recorded as the exhaust control value.

[0046] The exhaust control value is the minimum output DAC min Perform adjustment, reduce the output value based on the minimum starting value, monitor the valve position in real time, and when the valve position is reduced to 0, obtain the control value at this time as the exhaust value.

[0047] Step 4: The valve positioner controls the valve operation with the maximum valve position control value until the valve position is stable. The valve position feedback value at this time is recorded as the valve position feedback value when the membrane head is filled with gas.

[0048] On the basis of reaching the zero position in the third step, the maximum valve position control value of the positioner is given, specifically the DAC output signal, which is 4095 at 12 bits, and the valve position is monitored in real time. When the valve position does not change within five seconds, the valve position is deemed to be stable, and the valve position feedback value when the membrane head is filled with air is considered to be obtained.

[0049] Step 5: The valve positioner continuously increases the control value based on the minimum start-up control value until the valve position reaches the maximum, and the control value at this time is used as the top control value.

[0050] This step is used to calculate the peak value, i.e. the maximum output DAC max During this process, the positioner gives a minimum starting value DAC begin , continuously increase the control output, when the valve position reaches the maximum endpoint value, record the control value of the current valve position as the top value, where the preset maximum value is the valve position feedback value when the valve position reaches the maximum endpoint.

[0051] Step 6: The valve positioner controls the valve operation with the exhaust control value until the valve position feedback value reaches the initial valve position feedback value, and records the exhaust initial time and the exhaust end time respectively. The difference between the exhaust initial time and the exhaust end time is the full closing time.

[0052] On the basis that the valve position reaches the full valve position in the fifth step, the positioner gives the exhaust control value obtained in the third step, that is, the minimum output DAC min , and record the initial time. When the valve position reaches the initial valve position, record the end time. The end time minus the initial time is the full closing time.

[0053] Step 7: The valve positioner controls the valve operation with the top control value until the valve position feedback value reaches the valve position feedback value when the membrane head is filled with gas, and the initial inflation time and the final inflation time are recorded respectively. The difference between the initial inflation time and the final inflation time is the full opening time.

[0054] On the basis of reaching the initial valve position in the sixth step, the positioner controls the valve position to the zero position, and then gives the maximum output obtained in the fifth step, and records the initial time. When the valve position reaches the valve position feedback value when the membrane head is full of gas, the end time is recorded. The end time minus the initial time is the full opening time.

[0055] In the eighth step, the valve positioner determines the PID parameters according to the positioner control parameters by a dynamic step setting method, including:

[0056] The valve positioner uses the top control value as a step input, controls the valve operation through an open-loop control method, and records the actual valve position, the target valve position and the actual time during the operation time, wherein the difference between the actual valve position and the target valve position is the actual error, and the ratio of the actual error to the actual time is used as the change rate, and the maximum change rate slope_max is determined during the operation time;

[0057] In the step response curve, at the coordinate point where the maximum value of the rate of change corresponds to the actual time, a tangent is established with the maximum value of the rate of change as the slope. The intersection of the tangent and the X-axis is the lag time, and the intersection of the tangent and the Y-axis is the gain.

[0058] Determine PID parameters based on gain and lag time.

[0059] Among them, the slope is the ratio of the actual error of the stroke to the actual time. Among them, actual_error = cur_actual-pre_actual, cur_actual is the actual valve position, and pre_actual is the target valve position.

[0060] The gain is Among them, actual_stable is the valve position when stable, and step_signal is the step signal.

[0061] In the ninth step, the maximum overshoot calculation includes:

[0062] The valve position feedback value is divided into equal unit intervals to determine the stable control value of the maximum value of each unit interval, the preset position is one of the maximum values ​​of the unit intervals, and the valve position control value of the preset position is the stable control value of the corresponding maximum value of the unit interval.

[0063] The valve position feedback value is split, with 10% as the unit interval, and 0-100% is divided into 10%, 20%, and so on, to obtain the stable control value for every 10% of the valve position.

[0064] The valve positioner uses overshoot to calculate the valve position control value to control the valve operation. When the valve reaches the preset position, the valve positioner uses the valve position control value to control the valve to stabilize at the preset position to control the valve position stability. The valve positioner detects the farthest valve position feedback value that exceeds the preset position the farthest during the valve stabilization process. The maximum overshoot is the absolute value of the difference between the farthest valve position feedback value and the preset position.

[0065] During the inflation process, the overshoot calculation valve position control value is the product of the top control value and the inflation setting ratio, and the inflation setting ratio is greater than 1;

[0066] During the exhaust process, the overshoot calculation valve position control value is the product of the exhaust control value and the exhaust setting ratio, and the exhaust setting ratio is less than 1.

[0067] The specific process is as follows:

[0068] During the inflation process, the target valve position is set to 50%, and the positioner controls the valve position to reach the zero position. The given overshoot value is calculated as DACmax*ratio1, where ratio1 is the set ratio, and ratio1 is greater than 1. At this time, the regulating valve will be inflated and the valve position will rise. When the valve position value reaches 50% of the valve position, the control value is changed to the stable value of 50% of the valve position. In addition, the farthest valve position feedback value that exceeds the preset position is detected and updated in real time. In the inflation process, it is the maximum value of the valve position max. When the actual valve position cur_actual is less than the maximum value of the valve position max, the timer starts to count down. When the countdown ends, the maximum overshoot of the inflation process overimpulse_in=max-50 is obtained.

[0069] During the exhaust process, the target valve position is set to 50%, and the positioner controls the valve to keep it at the full valve position. Then, the control value is set to DACmin * ratio2, where ratio2 is a set ratio and ratio2 < 1. At this time, the regulating valve will exhaust and the valve position will decrease. When the valve position reaches 50% of the valve position, the control value becomes the stable value at 50% of the valve position during the exhaust process. And the feedback value of the farthest valve position that exceeds the preset position is detected and updated. During the exhaust process, it is the minimum value min of the valve position. When the actual valve position cur_actual is greater than the minimum value min of the valve position, the timer starts to count down. When the countdown ends, the maximum overshoot during the exhaust process overimpulse_down = 50 - min.

[0070] Finally, the above tuning parameters are saved.至此, the tuning process state machine ends, and the tuning program proceeds according to the above state machine.

[0071] During the final control, the valve positioner controls the valve to be stable within the preset accuracy range through the PID algorithm and the maximum overshoot. The control program of the positioner uses the positional PID for control, and the control program realizes the求取 of the stable point. The control part divides the control area into four parts according to the error interval. When in different intervals, different control methods are adopted and corresponding ranges of output are output. The following is an explanation:

[0072] When the actual error > the maximum overshoot, at this time, it is in the fast control area, quickly narrowing the range and outputting a larger value.

[0073] When the absolute value of the actual error > 5.7 and the actual error is less than the maximum overshoot, at this time, it is in the constant speed interval. In order to further narrow the range, the output is still relatively large, but smaller than the output in 1.

[0074] When 1 < real_error < 5.7 (selecting 5.7 as the boundary is considered to require sufficient output for small step control), at this time, it is considered that it is about to enter the slow speed interval and the output is further reduced.

[0075] When the absolute value of the actual error ≤ 1, at this time, it is considered to enter the stable interval, and the output adopts the stable control value output tending to the target valve position to achieve the stable purpose.

[0076] Finally, it should be noted that the above specific implementation manners are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for self-tuning valve positioner parameters, characterized in that: The valve positioner has a one-key setting function for completing all parameter calculations used in valve control. The one-key setting function includes: positioner control parameter calculation, PID parameter calculation, and maximum overshoot calculation; The positioner control parameter calculation includes: the valve positioner controls the valve operation with different valve position control values, collects valve position information in real time, and determines the required valve position control value as the positioner control parameter; The PID parameter calculation includes: the valve positioner determines the PID parameters by a dynamic step setting method according to the positioner control parameters; The maximum overshoot calculation includes: the valve positioner uses the overshoot to calculate the valve position control value to control the valve operation; when the valve reaches the preset position, the valve positioner uses the valve position control value that controls the valve to stabilize at the preset position to control the valve position stability; the valve positioner detects the farthest valve position feedback value that exceeds the preset position farthest during the valve stabilization process; the maximum overshoot is the absolute value of the difference between the farthest valve position feedback value and the preset position.

2. The method for self-tuning valve positioner parameters according to claim 1, characterized in that: The positioner control parameter calculation includes: start control value calculation, exhaust control value calculation, valve position feedback value calculation when the membrane head is full of gas, top impact control value calculation, full closing time calculation and full opening time calculation.

3. The method for self-tuning valve positioner parameters according to claim 2, characterized in that: The startup control value calculation includes: The valve positioner controls the valve to exhaust until the valve position is stable, and the valve position feedback value at this time is recorded as the initial valve position feedback value; The valve positioner continuously increases the control value in proportion to the initial valve position control value until the valve position starts to change. The control value when the valve position starts to change is recorded as the minimum start control value.

4. The method for self-tuning valve positioner parameters according to claim 3, characterized in that: The exhaust control value calculation includes: The valve positioner continuously reduces the control value based on the minimum start-up control value until the valve position is zero, and the control value at this time is recorded as the exhaust control value.

5. The method for self-tuning valve positioner parameters according to claim 4, characterized in that: The valve position feedback value calculation in the state where the membrane head is filled with gas includes: The valve positioner controls the operation of the valve with the maximum valve position control value until the valve position is stable. The valve position feedback value at this time is recorded as the valve position feedback value when the membrane head is filled with gas.

6. The method for self-tuning valve positioner parameters according to claim 5, characterized in that: The calculation of the top impact control value includes: The valve positioner continuously increases the control value based on the minimum start-up control value until the valve position reaches the maximum, and the control value at this time is used as the top control value.

7. The method for self-tuning valve positioner parameters according to claim 6, characterized in that: The full closing time calculation includes: The valve positioner controls the valve operation with the exhaust control value until the valve position feedback value reaches the initial valve position feedback value, and records the exhaust initial time and the exhaust end time respectively, and the difference between the exhaust initial time and the exhaust end time is the full closing time.

8. The method for self-tuning valve positioner parameters according to claim 7, characterized in that: The full-open time calculation includes: The valve positioner controls the operation of the valve with the top impact control value until the valve position feedback value reaches the valve position feedback value when the membrane head is filled with air, and records the initial inflation time and the final inflation time respectively, and the difference between the initial inflation time and the final inflation time is the full opening time.

9. The method for self-tuning valve positioner parameters according to claim 8, characterized in that: The valve positioner determines the PID parameters according to the positioner control parameters by a dynamic step setting method, including: The valve positioner uses the top control value as a step input, controls the valve operation through an open-loop control method, and records the actual valve position, the target valve position and the actual time during the operation time, wherein the difference between the actual valve position and the target valve position is the actual error, and the ratio of the actual error to the actual time is used as the change rate, and the maximum value of the change rate is determined during the operation time; In the step response curve, at the coordinate point where the maximum value of the rate of change corresponds to the actual time, a tangent is established with the maximum value of the rate of change as the slope. The intersection of the tangent and the X-axis is the lag time, and the intersection of the tangent and the Y-axis is the gain. Determine PID parameters based on gain and lag time.

10. The method for self-tuning valve positioner parameters according to claim 9, characterized in that: The maximum overshoot calculation includes: The valve position feedback value is divided into equal unit intervals to determine the stable control value of the maximum value of each unit interval, wherein the preset position is the maximum value of one of the unit intervals, and the valve position control value of the preset position is the stable control value of the corresponding maximum value of the unit interval; During the inflation process, the overshoot calculation valve position control value is the product of the top control value and the inflation setting ratio, and the inflation setting ratio is greater than 1; During the exhaust process, the overshoot calculation valve position control value is the product of the exhaust control value and the exhaust setting ratio, and the exhaust setting ratio is less than 1.

Images