Valve positioner setting and control method based on valve position stable value

Abstract

The invention discloses a valve positioner setting and control method based on a valve position stable value. The valve positioner setting and control method comprises a setting mode and a control mode, wherein the setting mode comprises setting of positioner characteristic parameters, PID parameter setting, actuator performance parameters and comprehensive control parameters. And the control mode adopts a subsection control method, and the control of the valve positioner based on the valve position stable value is realized by utilizing parameters set by the setting mode. According to the invention, overshoot in the control process can be effectively suppressed, and the control stability is maintained; and meanwhile, the regulation and control speed of the valve position can be increased in the rapid area.

Description

Technical Field

[0001] The invention belongs to the field of intelligent valve positioners or intelligent instruments, and in particular relates to a valve positioner setting and control method based on a valve position stability value. Background Art

[0002] In production process control, the regulating valve is the key execution unit for adjusting process parameters such as medium flow, pressure, temperature and liquid level. Its performance directly affects the stability and efficiency of the entire system. According to different control methods, regulating valves can be divided into three types: pneumatic, electric and hydraulic. These valves are widely used in many fields such as petrochemical, water conservancy, metallurgy, electricity and construction.

[0003] As the core component of pneumatic control valves, intelligent valve positioners play a vital role in the precise positioning of valves. The positioner is equipped with advanced control algorithms to ensure accurate control of valve opening, which is one of the core technologies for achieving efficient regulation. The technological advancement and response speed of the valve positioner directly affect the overall performance level of the control valve, thereby determining the regulation accuracy and response capability of the system. Therefore, the development of high-performance intelligent valve positioners is of great significance to improving the level of industrial automation and optimizing production efficiency.

[0004] The intelligent valve positioner consists of a development board, an I / P module and a pneumatic amplifier. The I / P module converts the electrical signal given by the development board into a pneumatic signal. The pneumatic amplifier amplifies the pneumatic signal output by the I / P module into a pneumatic signal sufficient to regulate the pneumatic control valve. The I / P module and the pneumatic amplifier module are collectively referred to as EPM ("Electropneumatic Positioner Module") modules. The flow characteristics of the EPM module will directly affect the control effect.

[0005] At the same time, the traditional valve positioner algorithm only roughly adjusts the characteristics of the intelligent valve positioner, ignoring the influence of the EPM module inside the positioner on the control effect. Due to the production and assembly of the EPM module and other issues, different positioners of the same model have differences in the filling and exhaust flow characteristics. If the characteristic parameters of the EPM module of the positioner are adjusted, they are relatively rough. Therefore, this paper proposes a valve positioner adjustment and control method based on the valve position stability value, which can be applied to the development and application of nozzle baffle valve positioner products. This method combines the EPM module characteristics inside the valve positioner and the control valve characteristics to improve the accuracy and stability of valve position control. Summary of the invention

[0006] In view of the technical problems existing in the background technology, the present invention proposes a valve positioner setting and control method based on the valve position stability value. It mainly includes setting mode and control mode: the setting mode includes the setting of the positioner characteristic parameters (maximum output PWM max 、Minimum output PWM min , output start value PWM begin And 0%, 10%, 20%...100% every 10% valve position stable control value size), PID parameter tuning (K P , K i , K d )、Actuator performance parameters (Actuator stroke parameters: Maximum stroke D max , minimum stroke D min ; Actuator direction parameters: positive stroke, reverse stroke) and comprehensive control parameters (maximum overimpulse). The control mode uses the parameters adjusted by the setting mode to achieve control of the valve positioner based on the stable value of the valve position.

[0007] The specific steps include: Step A1: Install the smart valve positioner on the regulating valve that needs to be regulated, and select a position sensor with a suitable travel range according to the usage requirements, and pass the appropriate air source pressure. The smart valve positioner is powered by a 4ma-20ma signal.

[0008] Step A2: The intelligent valve positioner enters the setting mode and performs exhaust operation. When the valve position change amplitude is less than the set threshold, it is considered that the valve position has reached the zero position. The valve position ADC value at this time is sampled as the minimum valve position stroke D. min .

[0009] Step A3: Set the initial value of PWM output, increase the output value of the set ratio every second, and monitor the valve position feedback ADC value sent back by the displacement sensor in real time; when the valve position starts to move, record the output value at this time as the output start value PWM begin ; Then reduce the output value by the set value. When the valve position reaches D min When the PWM output value is recorded as the minimum output PWM min .

[0010] Step A4: Instruct the microcontroller to output the maximum duty cycle PWM signal to the EPM module, and monitor the valve position feedback ADC value sent back by the displacement sensor in real time. When the ADC valve position remains unchanged, start timing for 2-6 seconds. When the timing ends, record the current ADC feedback value as the maximum valve position travel D max , after which the valve position begins to exhaust.

[0011] Step A5: When the valve position is stable at 0 valve position, set the output of the smart valve positioner to the start value PWM begin , and then increase the output at the set time; when approaching the full valve position, in order to prevent the output value from increasing too quickly and causing the maximum output PWM to be obtained max If the valve position is too large, the waiting time for the valve position to be stable will be increased. After the waiting time is over, the output will be increased. When the valve position feedback ADC value transmitted in real time reaches the maximum valve position stroke D max When the PWM output value is recorded, the maximum output PWM max .

[0012] Step A6: Using Maximum Output PWM max 、Minimum output PWM min , full duty cycle PWM signal and 0 duty cycle PWM signal (full duty cycle PWM signal and 0 duty cycle PWM signal are obtained by setting the PWM duty cycle size in the program) through the system tick timer function system_tick of the microcontroller, calculate the full open time T open , Full off time T close , Fastest full opening time T open_fast and the fastest full closing time T close_fast .

[0013] Step A7: The full-open time T obtained in step A6 open , Full off time T close , Fastest full opening time T open_fast And the fastest full shutdown time T close_fast Calculate the ratio of full-open time to the fastest full-open time K open And the ratio of full closing time to the fastest full closing time K close ,in , .

[0014] Step A8: Use the step setting method to obtain three characteristic parameters of the positioner system: gain K, time constant T, and lag time constant L. The specific steps of the step setting method are as follows:

[0015] Step B1: Give the IP module a step size equal to the maximum output value PWM obtained by step A5 max The step signal causes the EPM to start responding and regulating the pneumatic control valve.

[0016] Step B2: During the step setting process, the real-time valve position feedback value cur_actual and the running time time of the regulating valve are sampled for each control, and at the end of each function process, the real-time valve position feedback value cur_actual collected this time is assigned to the previous feedback value pre_actual. The valve position change value actual_error is obtained from the real-time valve position feedback value cur_actual and the previous feedback value pre_actual, and then divided by the execution interval TIME_CYCLE of each control, the change rate slope can be obtained.

[0017] Step B3: Repeat step B2, obtain the maximum change rate slope_max in the process, the valve position value actual_slope_max at this time by judging, and calculate the timestamp at this time and save it in time_slope_max.

[0018] Step B4: Based on the maximum change rate slope_max obtained in step B3, the valve position value actual_slope_max at the maximum change rate, and the timestamp time_slope_max at the maximum change rate, the tangent slope k and intercept b at the maximum change rate are obtained respectively. , Then, we can use the slope k and intercept b to draw the tangent line at slope_max. , the tangent line intersects the final valve position stable value e ss With the x-axis, we can get the time axis time1 and time2 of the two intersection points, and thus get the lag time constant , time constant , since the step size is PWM max , so the gain .

[0019] Step A9: Substitute the three characteristic parameters obtained by step A8: gain K, time constant T, and lag time constant L into the empirical formulas of Ziegler-Nichols tuning rule (ZN rule) and Cohen-Coon tuning rule (CC rule) to obtain two sets of PID parameters: K P_ZN , K I_ZN , K D_ZN and K P_CC , K I_CC , K D_CC .

[0020] Step A10: Introduce the classic position PID algorithm, pass two sets of PID parameters obtained by different tuning methods into the algorithm, evaluate the control effects of the two sets of parameters through the maximum overshoot, rise time and time-weighted absolute error integral ITAE, and select the set of parameters with better control effect as the PID parameter K of the control algorithm. P , K I , K D .

[0021] Step A11: Use the PID control algorithm to obtain the stable control value of the valve position at 0%, 10%, 20%...100% every 10% when going up and down, and obtain the k value of each 10% interval. i With b i The specific steps for obtaining the valve position stability control value are as follows:

[0022] Step C1: Calling a PID control method that can converge to a steady-state error as a control method for obtaining a stable control value.

[0023] Step C2: First, obtain the stable control value of the valve position every 10 percent of the inflation process. Taking the air-open valve as an example, the initial valve position is 0 valve position, and then set the target valve position to 10%.

[0024] Step C3: When the valve position enters When the timer starts to count down, the window average filter function starts to dynamically collect the control value; if the timer has not ended, but the valve position exceeds the steady-state error zone At this time, the timer is reset and the internal data of the window average filter function is cleared; if the timer countdown ends, the value returned by the window average filter function at this time is assigned to the array valvepos_in used to store the stable control value during the inflation process, and then the target valve position is increased by 10%.

[0025] Step C4: Repeat step C3 to obtain the valve position stability control values ​​of 20%, 30%, 40%...100% during the inflation process.

[0026] Step C5: After the inflation stability value is obtained, the valve position is at 100%, and then the target valve position is reduced by 10%.

[0027] Step C6: When the valve position enters When the timer starts to count down, the window average filter function starts to dynamically collect the control value; if the timer has not ended, but the valve position exceeds the steady-state error zone At this time, the timer is reset and the internal data of the window average filter function is cleared; if the timer countdown ends, the value returned by the window average filter function at this time is assigned to the array valvepos_de used to save the stable control value during the inflation process, and then the target valve position is reduced by 10%.

[0028] Step C7: Repeat step C6 to obtain the valve position stability control values ​​of 80%, 70%, 60%...0% during the inflation process.

[0029] Step A12: Use the 50% valve position stability control value obtained in step A11 to obtain the maximum overshoot of the charging process Overimpulse_in and the maximum overshoot of the exhaust process Overimpulse_down.

[0030] Taking the air-open type regulating valve as an example, the specific steps for obtaining the maximum overshoot during the inflation process and the maximum overshoot during the exhaust process are as follows: Step D1: Set the target valve position to 50%, and the given initial control value is , where ratio is the set ratio, and when ratio is greater than 1, the regulating valve will be inflated and the valve position will rise.

[0031] Step D2: When the valve position reaches 50%, the control value is changed from PWM max Reduced to the stable value of 50% valve position during the inflation process. And the maximum value of the valve position max is updated in real time. When the real-time valve position value cur_actual is less than the maximum value of the valve position max, the timer starts counting down. When the countdown ends, the maximum overshoot of the inflation process is obtained. max-50. Then jump to step D3.

[0032] Step D3: Given the positioner size as PWM max The signal enables it to maintain the full valve position, and then the control value is set to , where ratio is the set value. When ratio is less than 1, the regulating valve will exhaust air and the valve position will drop.

[0033] Step D4: When the valve position reaches 50%, the control value is changed from PWM min It becomes the stable value of 50% valve position in the exhaust process. And the minimum valve position min is updated in real time. When the real-time valve position value cur_actual is greater than the minimum valve position min, the timer starts counting down. When the countdown ends, the maximum overshoot of the exhaust process is obtained. .

[0034] Step A13: Assign the adjusted parameters to the parameters under the control mode handle and store them in the positioner EEPROM. After saving, change the positioner mode from the adjustment mode to the control mode.

[0035] Step A14: The positioner enters the control mode and uses the control parameters obtained by setting to control the valve position through segmented PID control based on the valve position stability control value. The specific execution steps of the segmented PID control based on the valve position stability control value are as follows:

[0036] Step E1: Subtract the target valve position value calibrated by the current loop from the real-time valve position value sent back by the position sensor to obtain the valve position deviation err(n). The PID algorithm is used for control, and the output is obtained based on the error err(k). * ,in is the output of the PID algorithm, is the proportional gain of the PID controller, K I is the integral gain of the PID controller, K D is the differential gain of the PID controller, is the valve position deviation at time n, is the integral of the valve position deviation, is the differential of the valve position deviation. Then calibrate the output, the output .

[0037] Step E2: When or When the control valve actuator moves in the fast approach range, the upper limit of the control is The lower limit of control is , the value of ratio is the same as that in step D1, so that the pneumatic valve actuator can approach the target valve position as quickly as possible.

[0038] Step E3: When 1% or When the control valve actuator moves in the normal speed area, the upper limit of the control is The lower limit of control is The upper and lower control limits are smaller than those in step E2.

[0039] Step E4: When 1% When the regulating valve actuator moves into the stable value calculation interval, after entering this interval, the stable control value of each valve position in the charging and discharging process obtained in step A11 and the linearization parameter k of each interval are obtained. i and b i , we can get the stable control value of each valve position during the charging and exhausting process. The specific solution is:

[0040] The valve position value that the control algorithm needs to approach is the target valve position value target_actual. It is understood that it is necessary to solve the stable control value valvepos_stable that can maintain the valve position at the target valve position value target_actual, and obtain a stable value upper and lower limits stable_max and stable_min. Stable_max and stable_min are stable control values ​​of the target valve position value target_actual and 5% of the valve position above and below. According to the reduction of the valve position error err, the upper and lower limits of the stable value also approach the stable control value valvepos_stable of the target valve position. The approach formula is as well as .

[0041] Compared with the prior art, the present invention adopts a segmented control method, and uses the maximum overshoot obtained by setting as the demarcation basis of the fast zone to improve the versatility of the algorithm. In the fast zone, the valve position can be adjusted to quickly approach the target position; in the normal speed zone, the valve position control speed is slowed down, and at the same time, sufficient air pressure is ensured to drive the pneumatic control valve to operate during small step control; in the stable value calculation interval, the control stable value range can be quickly located, and the valve position stable value can be gradually approached according to the size of the valve position error value err(n), which can effectively suppress overshoot in the control process. Compared with the traditional control valve control method, the present invention can effectively reduce the overshoot and maintain the stability of control. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart for setting the valve positioner based on the stable value of the valve position; Figure 2 This is a schematic diagram of the step setting method; Figure 3 It is a control flow chart of the valve positioner based on the stable value of the valve position; Figure 4 This is a comparison chart of the control effect of the regulating valve position from 25% to 50%; Figure 5 This is a comparison chart of the control effect of the regulating valve position from 50% to 75%; Figure 6 This is a comparison chart of the control effect of the regulating valve position from 75% to 50%; Figure 7 This is a comparison chart of the control effects when the regulating valve position changes from 50% to 25%. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings.

[0044] A valve positioner setting and control method based on valve position stability value, mainly including setting mode and control mode: the setting mode includes setting of positioner characteristic parameters (maximum output PWM max 、Minimum output PWM min , output start value PWM begin And 0%, 10%, 20%...100% every 10% valve position stable control value size), PID parameter tuning (K P , K i , K d )、Actuator performance parameters (Actuator stroke parameters: Maximum stroke D max , minimum stroke D min ; Actuator direction parameters: positive stroke, reverse stroke) and comprehensive control parameters (maximum overimpulse). The control mode uses the parameters adjusted by the setting mode to achieve control of the valve positioner based on the stable value of the valve position.

[0045] like Figure 1 As shown, the specific steps include: Step A1: Install the smart valve positioner on the regulating valve that needs to be regulated, select a position sensor with a suitable travel range, and pass the appropriate air source pressure. The smart valve positioner is powered by a 4ma-20ma signal.

[0046] Step A2: The intelligent valve positioner enters the setting mode and performs exhaust operation. When the valve position is at a certain ADC value and the change amplitude is less than 6, it is considered that the valve position has reached the zero position. The valve position ADC value at this time is sampled as the minimum valve position stroke D. min .

[0047] Step A3: Set the initial value of PWM output, increase the output value of the set ratio every second, and monitor the valve position feedback ADC value sent back by the displacement sensor in real time; when the valve position starts to move, record the output value at this time as the output start value PWM begin ; Then reduce the output value by a certain value, when the valve position reaches D min When the PWM output value is recorded as the minimum output PWM min .

[0048] Step A4: Output the full duty cycle PWM signal and monitor the valve position feedback ADC value sent back by the displacement sensor in real time; when the ADC valve position remains unchanged, start timing for 3 seconds, and when the timing ends, record the current ADC feedback value as the maximum valve position travel D max , after which the valve position begins to exhaust.

[0049] Step A5: When the valve position is stable at 0 valve position, set the output of the smart valve positioner to the start value PWM begin ; Then, the output is increased at the set time. When the valve is close to the full valve position, in order to prevent the output value from increasing too quickly, the maximum output PWM max If the valve position is too large, the waiting time for the valve position to be stable will be increased. After the waiting time, the output will be increased. When the ADC value of the valve position feedback sent back in real time reaches the maximum valve position stroke D max When the PWM output value is recorded, the maximum output PWM max .

[0050] Step A6: Using the upper control limit PWM max , control lower limit PWM min , full duty cycle PWM signal and 0 duty cycle PWM signal (full duty cycle PWM signal and 0 duty cycle PWM signal are obtained by setting the PWM duty cycle size in the program), and the full-on time T is calculated through the system tick timer function system_tick of the microcontroller open , Full off time T close , Fastest full opening time T open_fast And the fastest full shutdown time T close_fast .

[0051] Step A7: The full-open time T obtained in step A6 open , Full off time T close , Fastest full opening time T open_fast And the fastest full shutdown time T close_fast Calculate the ratio of full-open time to the fastest full-open time K open And the ratio of full closing time to the fastest full closing time K close ,in , .

[0052] Step A8: Use the step setting method to obtain the three characteristic parameters of the positioner system: gain K, time constant T, and lag time constant L. Figure 2 As shown, the specific steps of the step setting method are as follows:

[0053] Step B1: Give the IP module a step size equal to the maximum output value PWM obtained by step A5 max A step signal (in this embodiment, the step signal size is 1) causes the EPM to start responding to regulate the pneumatic control valve.

[0054] Step B2: During the step setting process, the real-time valve position feedback value cur_actual and the running time time of the regulating valve are sampled for each control, and at the end of each function process, the real-time valve position feedback value cur_actual collected this time is assigned to the previous feedback value pre_actual. The valve position change value actual_error is obtained from the real-time valve position feedback value cur_actual and the previous feedback value pre_actual, and then divided by the execution interval TIME_CYCLE of each control, the change rate slope can be obtained.

[0055] Step B3: Repeat step B2, obtain the maximum change rate slope_max in the process, the valve position value actual_slope_max at this time by judging, and calculate the timestamp at this time and save it in time_slope_max.

[0056] Step B4: Based on the maximum change rate slope_max obtained in step B3, the valve position value actual_slope_max at the maximum change rate, and the timestamp time_slope_max at the maximum change rate, the tangent slope k and intercept b at the maximum change rate are obtained respectively: , Then use the slope k and intercept b to draw a tangent line at slope_max , the tangent line intersects the final valve position stable value e ss With the x-axis, we can get the time axis time1 and time2 of the two intersection points, and thus get the lag time constant , time constant , since the step size is PWM max , so the gain .

[0057] Step A9: Substitute the three characteristic parameters obtained by step A8: gain K, time constant T, and lag time constant L into the empirical formula of Ziegler-Nichols tuning law (ZN law) and Cohen-Coon tuning law (CC law) to obtain two sets of PID parameters: K P_ZN , K I_ZN , K D_ZN and K P_CC , K I_CC , K D_CC .

[0058] Step A10: Introduce the classic position PID algorithm, pass two sets of PID parameters obtained by different tuning methods into the algorithm, evaluate the control effects of the two sets of parameters through the maximum overshoot, rise time and time-weighted absolute error integral ITAE, and select the set of parameters with better control effect as the PID parameter K of the control algorithm. P , K I , K D .

[0059] Step A11: Use the PID control algorithm to obtain the stable control value of the valve position at 0%, 10%, 20%...100% every 10% when going up and down, and obtain the k value of each 10% interval. i With b i The specific steps of obtaining the stable control value are as follows:

[0060] Step C1: Calling a control method that can converge to a steady-state error as a control method for obtaining a stable control value.

[0061] Step C2: First, obtain the stable control value of the valve position every 10 percent of the inflation process. Taking the air-open valve as an example, the initial valve position is 0 valve position, and then set the target valve position to 10%.

[0062] Step C3: When the valve position enters When the timer starts to count down, the window average filter function starts to dynamically collect the control value. If the timer has not ended, but the valve position exceeds the steady-state error zone At this time, the timer is reset and the internal data of the window average filter function is cleared. If the timer countdown ends, the value returned by the window average filter function at this time is assigned to the array valvepos_in used to store the stable control value during the inflation process, and then the target valve position is increased by 10%.

[0063] Step C4: Repeat step C3 to obtain the valve position stability control values ​​of 20%, 30%, 40%...100% during the inflation process.

[0064] Step C5: After the inflation stability value is obtained, the valve position is at 100%, and then the target valve position is reduced by 10%.

[0065] Step C6: When the valve position enters When the timer starts to count down, the window average filter function starts to dynamically collect the control value. If the timer has not ended, but the valve position exceeds the steady-state error zone At this time, the timer is reset and the internal data of the window average filter function is cleared. If the timer countdown ends, the value returned by the window average filter function at this time is assigned to the array valvepos_de used to save the stable control value during the inflation process, and then the target valve position is reduced by 10%.

[0066] Step C7: Repeat step C6 to obtain the valve position stability control values ​​of 80%, 70%, 60%...0% during the inflation process.

[0067] Step A12: Use the 50% valve position stability control value obtained in step A11 to obtain the maximum overshoot of the charging process Overimpulse_in and the maximum overshoot of the exhaust process Overimpulse_down.

[0068] Taking the air-open type regulating valve as an example, the specific steps for obtaining the maximum overshoot during the inflation process and the maximum overshoot during the exhaust process are as follows: Step D1: Set the target valve position to 50%, and the given initial control value is , where ratio is the set ratio, and when ratio is greater than 1, the regulating valve will be inflated and the valve position will rise.

[0069] Step D2: When the valve position reaches 50%, the control value is changed from PWM max Reduced to the stable value of 50% valve position during the inflation process. And the maximum value of the valve position max is updated in real time. When the real-time valve position value cur_actual is less than the maximum value of the valve position max, the timer starts counting down. When the countdown ends, the maximum overshoot of the inflation process is obtained. max-50. Then jump to step D3.

[0070] Step D3: Given the locator locator size as PWM max The signal enables it to maintain the full valve position, and then the control value is set to , where ratio is the set ratio, and when ratio is less than 1, the regulating valve will exhaust air and the valve position will drop.

[0071] Step D4: When the valve position reaches 50%, the control value is changed from PWM min It becomes the stable value of 50% valve position in the exhaust process. And the minimum valve position min is updated in real time. When the real-time valve position value cur_actual is greater than the minimum valve position min, the timer starts counting down. When the countdown ends, the maximum overshoot of the exhaust process is obtained. .

[0072] Step A13: Assign the adjusted parameters to the parameters under the control mode handle and store them in the positioner EEPROM. After saving, change the positioner mode from the adjustment mode to the control mode.

[0073] Step A14: The positioner enters the control mode and uses the regulated control parameters to control the valve position through segmented PID control based on the valve position stable control value.

[0074] like Figure 3 As shown in the figure, the specific execution steps of the segmented PID control based on the valve position stable control value are as follows: Step E1: Subtract the target valve position value calibrated by the current loop from the real-time valve position value sent back by the position sensor to obtain the valve position deviation err(n). The PID algorithm is used for control, and the output is obtained based on the error err(k). * ,in is the output of the PID algorithm, is the proportional gain of the PID controller, K I is the integral gain of the PID controller, K D is the differential gain of the PID controller, is the valve position deviation at time n, is the integral of the valve position deviation, is the differential of the valve position deviation. Then calibrate the output, the output .

[0075] Step E2: When or When the control valve actuator moves in the fast approach range, the upper limit of the control is The lower limit of control is , the value of ratio is the same as that in step D1, so that the pneumatic valve actuator can approach the target valve position as quickly as possible.

[0076] Step E3: When 1% or When the control valve actuator moves in the normal speed area, the upper limit of the control is The lower limit of control is The upper and lower control limits are smaller than those in step E2.

[0077] Step E4: When 1% When the control enters the stable value calculation interval, after entering this interval, the stable control value of each valve position in the charging and discharging process obtained in step A11 and the linearization parameter k of each interval are obtained. i and b i , the stable control value of each valve position in the charging and exhausting process can be obtained.

[0078] The specific solution is: the valve position value that the control algorithm needs to approach is the target valve position value target_actual. It can be understood that it is necessary to solve the stable control value valvepos_stable that can maintain the valve position at the target valve position value target_actual. However, the stable control value inevitably has errors. Therefore, in the stable value calculation interval, a stable value upper and lower limits (stable_max and stable_min) are obtained. Stable_max and stable_min are stable control values ​​of 5% valve position above and below the target valve position value target_actual. According to the reduction of the valve position error err, the upper and lower limits of the stable value also approach the stable control value valvepos_stable of the target valve position. The approach formula is as well as .

[0079] The above method adopts the segmented control method, and uses the maximum overshoot obtained by tuning as the demarcation basis of the fast zone to improve the versatility of the algorithm. In the fast zone, the valve position can be adjusted to quickly approach the target position; in the normal speed zone, the valve position control speed is slowed down, and at the same time, sufficient air pressure is ensured to drive the pneumatic control valve to operate during small step control; in the stable value calculation interval, the control stable value range can be quickly located, and the valve position stable value can be gradually approached according to the size of the valve position error value err(n), which can effectively suppress overshoot in the control process. It can realize the one-button self-tuning of the intelligent valve positioner to obtain the control parameters and realize the function of precise control of the pneumatic control valve position.

[0080] In order to demonstrate the accuracy of the valve position control method described above, two sets of experimental data are used to evaluate the performance of the tuning and control method described in the present invention from the perspective of maximum overshoot, adjustment time, and ITAE performance indicators. ITAE (Integral of Time-weighted Absolute Error) is one of the important indicators for measuring the performance of a control system. It is the integral of the absolute error between the system output and the expected output, and each error value is weighted according to time, which is particularly suitable for tuning and optimizing the system. The formula for ITAE is: ,in is the system error and t is the time.

[0081] For specific experimental data, see Figure 4~Figure 7 ,Depend on Figure 4~Figure 7 The following table can be obtained: ; In the table, HLPID is the control algorithm designed by the present invention, and PID is the traditional PID control algorithm; it can be seen from the table that: the adjustment time of the HLPID control algorithm is shorter than that of the traditional PID control algorithm, which can explain that the control algorithm designed by the present invention improves the rapidity of control; the maximum overshoot of HLPID is smaller than that of the traditional PID control algorithm, which can explain that the control algorithm designed by the present invention improves the stability of control; the ITAE values ​​of the control of each stage of HLPID are smaller than the ITAE values ​​of the traditional PID control algorithm, and a smaller ITAE value means that the system has better performance, smaller error and faster response when tracking the set value.

[0082] In actual control, the method of the present invention can achieve the control effect of quickly approaching the target position, small overshoot, and no oscillation, and the steady-state error can reach , to meet the needs of regulating valve control.

Claims

1. A valve positioner setting and control method based on valve position stability value, characterized in that: It includes setting mode and control mode: the setting mode includes setting of positioner characteristic parameters, PID parameter setting, actuator performance parameters and comprehensive control parameters; the control mode uses the parameters set by the setting mode to realize the control of the valve positioner based on the valve position stability value; The specific steps include: Step A1: Install the smart valve positioner on the regulating valve that needs to be regulated, and select a position sensor with a suitable travel range according to the use requirements, and pass the appropriate air source pressure. The smart valve positioner is powered by a 4ma-20ma signal; Step A2: The intelligent valve positioner enters the setting mode and performs exhaust operation. When the valve position change amplitude is less than the set threshold, it is considered that the valve position has reached the zero position. The valve position ADC value at this time is sampled as the minimum valve position stroke D. min ; Step A3: Set the initial value of PWM output, increase the output value of the set ratio every second, and monitor the valve position feedback ADC value sent back by the displacement sensor in real time; when the valve position starts to move, record the output value at this time as the output start value PWM begin ; Then reduce the output value by the set value. When the valve position reaches D min When the PWM output value is recorded as the minimum output PWM min ; Step A4: Instruct the microcontroller to output the maximum duty cycle PWM signal to the EPM module, and monitor the valve position feedback ADC value sent back by the displacement sensor in real time. When the ADC valve position remains unchanged, start timing for 2-6 seconds. When the timing ends, record the current ADC feedback value as the maximum valve position travel D max , after which the valve position begins to exhaust; Step A5: When the valve position is stable at 0 valve position, set the output of the smart valve positioner to the start value PWM begin , and then increase the output at the set time; when approaching the full valve position, in order to prevent the output value from increasing too quickly and causing the maximum output PWM to be obtained max If the valve position is too large, the waiting time for the valve position to be stable will be increased. After the waiting time is over, the output will be increased. When the valve position feedback ADC value transmitted in real time reaches the maximum valve position stroke D max When the PWM output value is recorded, the maximum output PWM max ; Step A6: Using Maximum Output PWM max 、Minimum output PWM min The full duty cycle PWM signal and the zero duty cycle PWM signal are passed through the system tick timer function system_tick of the microcontroller to calculate the full-on time T open , Full off time T close , Fastest full opening time T open_fast and the fastest full closing time T close_fast ; Step A7: The full-open time T obtained in step A6 open , Full off time T close , Fastest full opening time T open_fast And the fastest full shutdown time T close_fast Calculate the ratio of full-open time to the fastest full-open time K open And the ratio of full closing time to the fastest full closing time K close ,in , ; Step A8: Use the step setting method to obtain three characteristic parameters of the positioner system: gain K, time constant T, and lag time constant L; Step A9: Substitute the three characteristic parameters obtained in step A8: gain K, time constant T, and lag time constant L into the Ziegler-Nichols tuning rule and the Cohen-Coon tuning rule to obtain two sets of PID parameters: K P_ZN , K I_ZN , K D_ZN and K P_CC , K I_CC , K D_CC ; Step A10: Introduce the classic position PID algorithm, pass two sets of PID parameters obtained by different tuning methods into the algorithm, evaluate the control effects of the two sets of parameters through the maximum overshoot, rise time and time-weighted absolute error integral ITAE, and select the set of parameters with better control effect as the PID parameter K of the control algorithm. P , K I , K D ; Step A11: Use the PID control algorithm to obtain the stable control value of the valve position at 0%, 10%, 20%...100% every 10% when going up and down, and obtain the k value of each 10% interval. i With b i ; Step A12: using the 50% valve position stability control value obtained in step A11, the maximum overshoot value Overimpulse_in of the charging process and the maximum overshoot value Overimpulse_down of the exhaust process are obtained; Step A13: Assign the parameters obtained by setting to the parameters under the control mode handle and store them in the positioner EEPROM. After saving, change the positioner mode from setting mode to control mode. Step A14: The positioner enters the control mode, and uses the control parameters obtained by setting to control the valve position through segmented PID control based on the valve position stability control value; the specific execution steps of the segmented PID control based on the valve position stability control value are as follows: Step E1: Subtract the real-time valve position value sent back by the position sensor from the target valve position value calibrated by the current loop to obtain the valve position deviation err(n); use the PID algorithm for control, and according to the obtained error err(k), the output is * ,in is the output of the PID algorithm, is the proportional gain of the PID controller, K I is the integral gain of the PID controller, K D is the differential gain of the PID controller, is the valve position deviation at time n, is the integral of the valve position deviation, is the differential of the valve position deviation; then calibrate the output, the output ; Step E2: When or When the control valve actuator moves in the fast approach range, the upper limit of the control is The lower limit of control is , the value of ratio is the same as that in step D1, so that the pneumatic valve actuator can approach the target valve position as quickly as possible; Step E3: When 1% or When the control valve actuator moves in the normal speed area, the upper limit of the control is The lower limit of control is ; The upper and lower limits of control are smaller than those in step E2; Step E4: When 1% When the regulating valve actuator moves into the stable value calculation interval, after entering this interval, the stable control value of each valve position in the charging and discharging process obtained in step A11 and the linearization parameter k of each interval are obtained. i and b i , and obtain the stable control value of each valve position during the charging and exhausting process; the specific solution is: The valve position value that the control algorithm needs to approach is the target valve position value target_actual. It is understood that it is necessary to solve the stable control value valvepos_stable that can maintain the valve position at the target valve position value target_actual, and obtain a stable value upper and lower limits stable_max and stable_min. Stable_max and stable_min take the stable control value of the target valve position value target_actual above and below 5% of the valve position. According to the reduction of the valve position error err, the upper and lower limits of the stable value also approach the stable control value valvepos_stable of the target valve position. The approach formula is as well as .

2. The valve positioner setting and control method based on valve position stability value according to claim 1, characterized in that: The specific steps of the step setting method described in step A8 are as follows: Step B1: Give the IP module a maximum output value PWM set in step A5 max The step signal causes the EPM to start responding and regulating the pneumatic control valve; Step B2: In the process of step setting, the real-time valve position feedback value cur_actual and the running time time of the regulating valve are sampled for each control, and at the end of each function process, the real-time valve position feedback value cur_actual collected this time is assigned to the previous feedback value pre_actual; and the valve position change value actual_error is obtained from the real-time valve position feedback value cur_actual and the previous feedback value pre_actual, and then divided by the execution interval TIME_CYCLE of each control, the change rate slope can be obtained; Step B3: repeat step B2, determine the maximum change rate slope_max in the process, the valve position value actual_slope_max at this time, and calculate the timestamp at this time and save it in time_slope_max; Step B4: Based on the maximum change rate slope_max obtained in step B3, the valve position value actual_slope_max at the maximum change rate, and the timestamp time_slope_max at the maximum change rate, the tangent slope k and intercept b at the maximum change rate are obtained respectively. , ; Then the slope k and intercept b can be used to draw the tangent line at slope_max , the tangent line intersects the final valve position stable value e ss With the x-axis, we can get the time axis time1 and time2 of the two intersection points, and thus get the lag time constant , time constant , since the step size is PWM max , so the gain .

3. The valve positioner setting and control method based on valve position stability value according to claim 1, characterized in that: The specific steps for obtaining the valve position stability control value described in step A11 are as follows: Step C1: calling a PID control method that can converge to a steady-state error as a control method for obtaining a stable control value; Step C2: First, obtain the stable control value of the valve position every 10% during the inflation process. Taking the air-open valve as an example, the initial valve position is 0 valve position, and then the target valve position is set to 10%; Step C3: When the valve position enters When the timer starts to count down, the window average filter function starts to dynamically collect the control value; if the timer has not ended, but the valve position exceeds the steady-state error zone , at this time, the timer is reset and the internal data of the window average filter function is cleared; if the timer countdown ends, the value returned by the window average filter function at this time is assigned to the array valvepos_in used to save the stable control value during the inflation process, and then the target valve position is increased by 10%; Step C4: Repeat step C3 to obtain the valve position stability control values ​​of 20%, 30%, 40%...100% during the inflation process; Step C5: After the inflation stability value is obtained, the valve position is at 100%, and then the target valve position is reduced by 10%; Step C6: When the valve position enters When the timer starts to count down, the window average filter function starts to dynamically collect the control value; if the timer has not ended, but the valve position exceeds the steady-state error zone , at this time, the timer is reset and the internal data of the window average filter function is cleared; if the timer countdown ends, the value returned by the window average filter function at this time is assigned to the array valvepos_de used to save the stable control value during the inflation process, and then the target valve position is reduced by 10%; Step C7: Repeat step C6 to obtain the valve position stability control values ​​of 80%, 70%, 60%...0% during the inflation process.

4. The valve positioner setting and control method based on valve position stability value according to claim 1, characterized in that: Taking the air-open type regulating valve as an example, the specific steps for obtaining the maximum overshoot of the charging process and the maximum overshoot of the exhaust process described in step A12 are as follows: Step D1: Set the target valve position to 50%, and the given initial control value is , where ratio is the set ratio, and when ratio is greater than 1, the regulating valve will be inflated and the valve position will rise; Step D2: When the valve position reaches 50%, the control value is changed from PWM max Reduced to the stable value of 50% valve position during the inflation process; and the maximum value of the valve position max is updated in real time. When the real-time valve position value cur_actual is less than the maximum value of the valve position max, the timer starts counting down. When the countdown ends, the maximum overshoot of the inflation process is obtained. max-50; then jump to step D3; Step D3: Given the positioner size as PWM max The signal enables it to maintain the full valve position, and then the control value is set to , where ratio is the set value. When ratio is less than 1, the regulating valve will exhaust air and the valve position will drop. Step D4: When the valve position reaches 50%, the control value is changed from PWM min It becomes the stable value of 50% valve position in the exhaust process; and the minimum valve position value min is updated in real time. When the real-time valve position value cur_actual is greater than the minimum valve position value min, the timer starts counting down. When the countdown ends, the maximum overshoot of the exhaust process is obtained. .

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