JP2008102743A - Automatic tuning device and automatic tuning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine whether or not upper and lower limit value settings of a manipulated variable are appropriate in the execution of limit cycle automatic tuning. <P>SOLUTION: An automatic tuning device comprises a limit cycle automatic tuning computation part 6 for outputting a manipulated variable of a fixed amplitude to a controlled object and calculating control parameters of a controller from a control response to the manipulated variable output, in the execution of limit cycle automatic tuning, a time measurement part 8 for measuring an upper limit manipulated variable output time for which the manipulated variable output is an upper limit value and a lower limit manipulated variable output time for which the manipulated variable output is a lower limit value, in the execution of limit cycle automatic tuning, a ratio calculation part 9 for calculating a ratio RT of the upper limit manipulated variable output time to the lower limit manipulated variable output time, and a determination part 10 for determining whether or not the upper and lower limit value settings of the manipulated variable are appropriate in accordance with the ratio RT. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for adjusting a parameter of a controller such as a PID, and in particular, a limit cycle auto that outputs an operation amount having a constant amplitude to a controlled object and adjusts a parameter of the controller based on a control response according to the operation amount output. It is about tuning.

  A PID controller mounted on a general-purpose temperature controller or the like has an auto-tuning function for adjusting the PID parameter, and the PID parameter can be easily adjusted by the auto-tuning function. . As a typical method of this auto-tuning function, an upper limit value and a lower limit value are set in advance for the operation amount MV output to the controlled object, a limit cycle with a constant operation amount amplitude is generated, and a PID parameter is adjusted. There is a cycle system (see, for example, Patent Document 1).

The limit cycle method will be briefly described below. FIG. 9 is a waveform diagram for explaining a conventional limit cycle method, and FIG. 10 is a flowchart showing a process flow of the conventional limit cycle method. First, a lower limit value OL_AT and an upper limit value OH_AT of the operation amount MV that is output to the control target when auto-tuning is executed are set in advance.
When auto-tuning is executed, the control amount PV is compared with the set value SP (step 401 in FIG. 10). If the control amount PV is larger than the set value SP, the lower limit value OL_AT of the manipulated variable MV is output to the control target (step 402) When the control amount PV is equal to or smaller than the set value SP, the upper limit value OH_AT of the operation amount MV is output to the control target (step 403).

Next, vertical movement extreme value detection processing for detecting the extreme value of the control amount PV is performed (step 404). When the processing of steps 401 to 404 is performed for each control period and four extreme values of the control amount PV are detected, the detection of the vertical movement extreme value is completed. Here, the deviation Er between the set value SP and the control amount PV is obtained by the following equation.
Er = SP-PV (1)

  Then, as shown in FIG. 9, among the detected four extreme values, the deviation in the latest extreme value is the first extreme value deviation Er1, the deviation in the second new extreme value is the second extreme value deviation Er2, The deviation at the third new extreme value is defined as a third extreme value deviation Er3. Further, the time from the time t5 when the sign of the deviation Er is reversed immediately before the first extreme value deviation Er1 to the time t6 when the first extreme value deviation Er1 is obtained is defined as a first manipulated variable switching elapsed time Th1. Further, the time from the time t3 when the sign of the deviation Er is reversed immediately before the second extreme value deviation Er2 to the time t4 when the second extreme value deviation Er2 is obtained is defined as a second manipulated variable switching elapsed time Th2. .

Finally, a PID parameter composed of the proportional band Pb, the integration time Ti, and the differentiation time Td is calculated as follows, and the calculated PID parameter is set in the control calculation unit of the control device (step 405).
Pb = 250 | Er2-Er1 | / (OH_AT-OL_AT) (2)
Ti = 6 (Th1 + Th2) (3)
Td = 1.2 (Th1 + Th2) (4)
This completes the auto tuning.

JP 2003-330504 A

  Many of the commercially available controllers use the output upper limit value OH and output lower limit value OL of the operation amount MV output to the control target during actual control as the operation amount upper limit value OH_AT and operation amount lower limit value OL_AT at the time of auto-tuning. Use. Normally, OH = 100% and OL = 0% are often set. Therefore, the upper limit value of the operation amount during auto tuning is OH_AT = 100%, and the lower limit value of the operation amount is OL_AT = 0%. Many.

  In a control object having high heat retention in temperature control, the operation amount MV necessary for maintaining the control amount PV in the vicinity of the set value SP is substantially low, such as approximately MV = 20% or less. In this situation, if auto tuning with MV = 0% to 100% is executed with OH_AT = 100% setting, the temperature rise is high and the temperature drop is slow (high heat retention and difficult to cool), so it takes a lot of time for auto tuning. Problem arises (FIG. 11). In the example shown in FIG. 11, since the heat retaining property of the controlled object is high and it is difficult to cool, the time T_OL at which the operation amount lower limit value OL_AT is output is shorter than the time T_OH at which the operation amount upper limit value OH_AT is output during auto tuning. I understand that it is long.

  Such a problem is not limited to the case where the operation amount output upper limit value OH and the operation amount output lower limit value OL used during actual control are used as the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT during auto-tuning. If the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT set internally in advance correspond to those giving an inappropriate waveform as shown in FIG. As a countermeasure for the problem, an expert who can determine that auto-tuning is inappropriate uses a recorder or the like to observe the movement of the control amount PV at the time of auto-tuning. There was no choice but to change the output lower limit OL to an appropriate value and re-execute auto-tuning. Therefore, in many cases, it may be overlooked that auto-tuning is inappropriate.

The present invention has been made to solve the above-described problem, and an auto-tuning apparatus and auto-tuning that can determine whether or not the setting of the upper and lower limit values of an operation amount when performing auto-tuning by a limit cycle method is appropriate It aims to provide a method.
Another object of the present invention is to provide an auto-tuning device and an auto-tuning method that can automatically calculate appropriate correction values for the upper and lower limits of the manipulated variable when auto-tuning is executed.
Another object of the present invention is to provide an auto-tuning device and an auto-tuning method that can automatically re-execute auto-tuning after correcting the upper and lower limit values of the manipulated variable to an appropriate value.

The present invention provides an auto-tuning apparatus having a limit cycle auto-tuning function for setting a control parameter of a controller. When the limit cycle auto-tuning is executed, an operation amount having a constant amplitude is output to a control target. The control parameter of the controller is calculated based on the control response in accordance with the control cycle, the limit cycle auto-tuning calculating means for setting the calculated control parameter in the controller, and the manipulated variable output during the execution of the limit cycle auto-tuning. And an operation amount upper / lower limit value setting determination unit for determining whether the setting of the upper and lower limit values of the operation amount is appropriate based on an output time.
Further, in one configuration example of the auto-tuning device of the present invention, the operation amount upper / lower limit value setting determination means is an operation amount upper limit value output time during which the upper limit value of the operation amount is output during execution of the limit cycle auto-tuning. A time measurement unit that measures an operation amount lower limit value output time at which the lower limit value of the operation amount is output, and a ratio calculation unit that calculates a ratio between the operation amount upper limit value output time and the operation amount lower limit value output time; The determination unit determines whether or not the setting of the upper and lower limit values of the operation amount is appropriate based on the ratio.

The auto-tuning device of the present invention outputs a manipulated variable having a constant amplitude to the control target when the limit cycle auto-tuning is executed, and calculates a control parameter of the controller based on a control response according to the manipulated variable output. Limit cycle auto-tuning calculating means for setting the calculated control parameter in the controller, and whether the upper and lower limit values of the manipulated variable are appropriate based on the deviation of the controlled variable detected during the execution of the limit cycle auto-tuning And an operation amount upper / lower limit value setting determination means for determining whether or not.
Further, in one configuration example of the auto-tuning device of the present invention, the manipulated variable upper / lower limit value setting determination means is an extreme value deviation when the controlled variable reaches a maximum value or a minimum value during execution of the limit cycle auto-tuning. A ratio calculation unit that calculates a ratio between the absolute value of the latest first extreme value deviation and the absolute value of the second extreme value deviation detected immediately before the first extreme value deviation, and the ratio And a determination unit that determines whether or not the setting of the upper and lower limit values of the operation amount is appropriate.

Further, in one configuration example of the auto-tuning device of the present invention, when the operation amount upper / lower limit value setting determination unit determines that the setting of the upper / lower limit values of the operation amount is inappropriate, the upper limit of the operation amount A manipulated variable that calculates a correction value estimated to be appropriate for at least one of the value and the lower limit value, and updates the upper limit value or lower limit value of the manipulated variable output from the limit cycle auto-tuning calculating means to the corrected value Correction means are provided.
Further, in one configuration example of the auto-tuning device of the present invention, the limit cycle auto-tuning calculating unit is restarted after the processing of the operation amount correcting unit is completed, and the limit cycle auto-tuning calculating unit and the operation A restart instructing unit for causing the amount upper / lower limit value setting determining unit and the operation amount correcting unit to re-execute processing is provided.

Further, the present invention provides an auto-tuning method for setting a control parameter of a controller by a limit cycle auto-tuning method, and outputs an operation amount having a constant amplitude to a control target when the limit cycle auto-tuning is executed. A limit cycle auto-tuning calculation procedure for calculating a control parameter of the controller based on a control response according to the control response and setting the calculated control parameter in the controller;
An operation amount upper / lower limit value setting determination procedure for determining whether the setting of the upper and lower limit values of the operation amount is appropriate based on an output time of the operation amount output during execution of the limit cycle auto-tuning. is there.
In the auto tuning method of the present invention, when the limit cycle auto tuning is executed, an operation amount having a constant amplitude is output to the controlled object, and a control parameter of the controller is calculated based on a control response according to the operation amount output. Whether the setting of the upper and lower limit values of the manipulated variable is appropriate based on the limit cycle auto-tuning calculation procedure for setting the calculated control parameter in the controller and the deviation of the controlled variable detected during the execution of the limit cycle auto-tuning And a manipulated variable upper / lower limit value setting determination procedure.

  According to the present invention, it is possible to automatically determine whether or not the setting of the upper and lower limit values of the operation amount is appropriate based on the determination based on the output time of the operation amount output during execution of limit cycle auto-tuning. As a result, it is possible to greatly reduce the possibility of overlooking that the controller auto-tuning is inappropriate.

  Further, according to the present invention, it is possible to automatically determine whether or not the setting of the upper and lower limit values of the manipulated variable is appropriate based on the determination based on the deviation of the control amount detected during the execution of limit cycle auto-tuning.

  Further, in the present invention, when it is determined that the upper and lower limit values of the operation amount are inappropriate, the limit value is calculated by calculating a correction value that is estimated to be appropriate for at least one of the upper limit value and the lower limit value of the operation amount. The upper limit value or lower limit value of the manipulated variable output from the cycle auto-tuning calculating means can be automatically updated to the correction value.

  In the present invention, after the processing of the manipulated variable correcting means is completed, the limit cycle auto-tuning calculating means is restarted, so that the auto-tuning is automatically restarted after correcting the upper and lower limit values of the manipulated variable to appropriate values. Can be executed. As a result, it is possible to appropriately set the control parameters of the controller.

[Principle of the Invention]
The imbalance between the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT during auto tuning is the balance between the time during which the manipulated variable upper limit value OH_AT is output and the time during which the manipulated variable lower limit value OL_AT is output during auto tuning. Appear in the evil of. Therefore, when the operation amount upper limit value OH_AT is output and when the operation amount lower limit value OL_AT is output, the operation amount upper limit value OH_AT and the operation amount upper limit value OH_AT are compared with each other. It is possible to automatically determine that the setting of the amount lower limit value OL_AT is inappropriate. A method based on the time when the manipulated variable upper and lower limit values are output is referred to as a first method.

  As another determination index, the determination can also be made based on the absolute value of the extreme value deviation described in FIG. That is, when the ratio between the absolute value of the first extreme value deviation Er1 and the absolute value of the second extreme value deviation Er2 is out of a specific threshold range, the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT are set. It is possible to automatically determine that it is inappropriate. This technique based on the extreme value deviation is referred to as a second technique.

Furthermore, in both cases of the first and second methods, the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT can be automatically corrected based on the calculated ratio so as to have an appropriate balance. is there.
Furthermore, auto-tuning can be automatically re-executed using the corrected operation amount upper limit value OH_AT and operation amount lower limit value OL_AT.

  Hereinafter, the principle of the present invention will be described in more detail. When the balance between the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT at the time of auto tuning by the limit cycle method is inappropriate, the waveforms of the manipulated variable MV and the controlled variable PV are as shown in FIG. At this time, the set value SP shown in FIG. 11 corresponds to a switching point between the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT, which is called the center point of the limit cycle.

  For example, in the temperature control, when the temperature of the control target is fast and the temperature drop is slow, if the operation amount MV = OH_AT is output while the operation amount MV = OL_AT is decreasing, the temperature rises with a steep slope. The time during which the amount (temperature) PV is lower than the set value SP is short. That is, since the operation amount MV = OL_AT is switched to when the temperature PV exceeds the set value SP, the time T_OH during which the operation amount MV = OH_AT is output is relatively short. Further, the temperature PV greatly exceeds the set value SP as the temperature rises at a steep slope. That is, the absolute value of the amount by which the temperature PV exceeds the set value SP (the first extreme value deviation Er1 in the example of FIG. 11) is relatively large.

On the other hand, since the temperature drop has a gentle slope, it takes time until the temperature PV returns to the set value SP, and the time during which the temperature PV exceeds the set value SP becomes long. That is, during this time, the operation amount MV = OL_AT is established, and the time T_OL for outputting the operation amount MV = OL_AT is relatively long. Further, since the temperature drop is a gentle gradient, the absolute value of the amount by which the temperature PV falls below the set value SP (second extreme value deviation Er2 in the example of FIG. 11) becomes relatively small.
In the example of FIG. 11, the manipulated variable upper limit value OH_AT is relatively higher than the manipulated variable lower limit value OL_AT, so that the positive / negative balance of the control value PV with respect to the set value SP is in an inappropriate state.

  Accordingly, the time T_OH when the operation amount upper limit value OH_AT is output and the time T_OL when the operation amount lower limit value OL_AT is output are measured, respectively, and the ratio RT = T_OH / T_OL is smaller than a specific threshold value, the operation amount upper limit It can be determined that the value OH_AT is relatively high. Conversely, when the ratio RT is greater than another specific threshold, it can be determined that the operation amount lower limit value OL_AT is relatively too low. Needless to say, even when the ratio T_OL / T_OH in which the numerator and the denominator of the ratio RT are replaced is adopted, the equivalent determination can be made by changing the handling of the threshold. When the ratio T_OL / T_OH is adopted, if the ratio T_OL / T_OH is larger than a specific threshold, it can be determined that the operation amount upper limit value OH_AT is relatively too high, and the ratio T_OL / T_OH is smaller than another specific threshold Can be determined that the operation amount lower limit value OL_AT is relatively low.

  Further, when the absolute value ratio RE = | Er2 | / | Er1 | of the extreme value deviation is smaller than a specific threshold value, it can be determined that the operation amount upper limit value OH_AT is relatively too high. Conversely, when the ratio RE is greater than another specific threshold, it can be determined that the operation amount lower limit value OL_AT is relatively too low. In this description, the first extreme value deviation Er1 is a maximum value (a value exceeding the set value SP), and the second extreme value error Er2 is a minimum value (a value below the set value SP). If attention is paid to which of the extreme value deviations Er1 and Er2 is the maximum value and which is the minimum value, it goes without saying that an equivalent determination can be made even if the maximum value and the minimum value are interchanged. When the first extreme value deviation Er1 is a minimum value and the second extreme value deviation Er2 is a maximum value, the ratio RE = | Er1 | / | Er2 | may be adopted.

  Furthermore, it is possible to correct the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT by assuming, for example, a linear relationship (a relationship in which the ratios RT and RE are 1) by an unbalanced ratio RT or ratio RE. Therefore, the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT can be calculated more appropriately. An example of a correction method when it is assumed that the manipulated variable MV and the controlled variable PV have a linear relationship will be described later. However, the correction method of the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT is not limited to a method based on the linear relationship between the operation amount MV and the control amount PV. There are various ways to reflect the imbalance of the ratio RT or the ratio RE in the correction of the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT. Based on this is the basis for effective modifications.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the auto-tuning apparatus according to the first embodiment of the present invention. The present embodiment is based on the first method.
1 includes a set value SP input unit 1 for inputting a set value SP set by an operator of the device, a control amount PV input unit 2 for inputting a control amount PV detected by a sensor (not shown), An operation amount MV output unit 3 that outputs an operation amount MV to a control target (not shown), a two-position operation amount lower setting unit 4 that sets an operation amount lower limit value OL_AT for limit cycle auto tuning, and an operation amount for limit cycle auto tuning The upper position setting unit 5 for setting the upper limit value OH_AT and the processing procedure of limit cycle auto-tuning are executed, the operation amount MV is output to the control target, and based on the control response according to this operation amount output Limit cycle auto-tuning calculation unit 6 for calculating control parameters of a controller (not shown), limit A start instructing unit 7 for inputting a start instruction command for the auto-tuning from the outside and sending it to the limit cycle auto-tuning calculating unit 6; an output time T_OH at which an operation amount upper limit value OH_AT is output during execution of limit cycle auto-tuning; and an operation amount lower limit A time measuring unit 8 that measures the output time T_OL at which the value OL_AT is output, a ratio RT calculating unit 9 that calculates a ratio RT between the operation amount upper limit value output time T_OH and the operation amount lower limit value output time T_OL, and a ratio RT A determination unit 10 for determining whether or not the setting of the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT is appropriate, and when the setting of the operation amount upper limit value OH_AT or the operation amount lower limit value OL_AT is determined to be inappropriate It is estimated that at least one of the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT is appropriate. The correction value is calculated, and at least one of the operation amount upper limit value OH_AT set by the two-position operation amount lower setting unit 4 and the operation amount lower limit value OL_AT set by the two-position operation amount upper setting unit 5 is updated to the correction value. And a restart instruction unit 12 for sending a limit cycle auto-tuning restart instruction command to the limit cycle auto-tuning calculating unit 6 after the processing of the two-position operation amount correcting unit 11 is completed.

FIG. 2 is a block diagram showing a configuration of a controller to be tuned by the auto-tuning apparatus of FIG.
The controller has a set value SP input unit 20, a control amount PV input unit 21, an operation amount MV output unit 22, and a deviation between the set value SP and the control amount PV during a normal control operation after auto-tuning. And a control calculation unit 23 for calculating an operation amount MV by performing a feedback control calculation based on the control parameter.

Next, the limit cycle auto-tuning function of the auto-tuning device of this embodiment will be described. FIG. 3 is a flowchart showing the operation of the auto tuning device when limit cycle auto tuning is executed.
First, the activation instructing unit 7 sends an activation instruction command to the limit cycle auto-tuning calculating unit 6 when receiving an activation instruction for limit cycle auto-tuning from an operator, for example. Thereby, the limit cycle auto-tuning calculation unit 6 is activated, and limit cycle auto-tuning is started (step S100 in FIG. 3).

  The activated limit cycle auto-tuning calculation unit 6 compares the control amount PV with the set value SP (step S101). The set value SP is set by the operator of the apparatus, and is input to the limit cycle auto-tuning calculating unit 6 via the set value SP input unit 1. The control amount PV is detected by a sensor (not shown) and input to the limit cycle auto-tuning calculation unit 6 via the control amount PV input unit 2. In the limit cycle auto-tuning calculation unit 6, initial values of the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT are set in advance.

  When the control amount PV is larger than the set value SP, the limit cycle auto-tuning calculation unit 6 outputs the operation amount lower limit value OL_AT set by the two-position operation amount lower setting unit 4 to the operation amount MV output unit 3 (step S102) When the control amount PV is equal to or smaller than the set value SP, the operation amount upper limit value OH_AT set by the two-position operation amount upper setting unit 5 is output to the operation amount MV output unit 3 (step S103). The operation amount MV output unit 3 outputs the operation amount MV = OL_AT or MV = OH_AT to the control target.

  Next, the limit cycle auto-tuning calculation unit 6 performs a vertical movement extreme value detection process (step S104). FIG. 4 is a flowchart showing the vertical movement extreme value detection process of the limit cycle auto-tuning calculation unit 6. Since the control response in limit cycle auto-tuning is the same as the conventional one, the vertical movement extreme value detection process will be described with reference to FIG.

First, the limit cycle auto-tuning calculating unit 6 calculates the deviation Er of the current control cycle based on the set value SP and the control amount PV using the equation (1) (step S200 in FIG. 4). Subsequently, the limit cycle auto-tuning calculation unit 6 determines whether or not the following equation is satisfied (step S201).
| Er |> | Ermax | (5)

  In Equation (5), Ermax is the maximum deviation value, and the initial value is 0. When the formula (5) is satisfied, the limit cycle auto-tuning calculation unit 6 sets Ermax = Er, that is, the deviation Er of the current control cycle as the maximum deviation Ermax (step S202).

Next, the limit cycle auto-tuning calculation unit 6 determines whether the sign of the deviation Er has been switched using the following equation (step S203).
ErEr0 <0 (6)
Here, Er0 is a deviation before one control cycle. Equation (6) is used to determine that the sign of the deviation Er is reversed when the multiplication result of the current deviation Er and the deviation Er0 one control cycle before is negative. If the expression (6) is not established, it is determined that the vertical motion extreme value detection is not completed, and the process returns to step S101.

  When the processes of steps S101 to S103 and S104 (steps S200 to S203) are repeated for each control cycle, the maximum deviation Ermax is updated as the deviation Er increases. Then, at time t1 in FIG. 9, Equation (6) is established.

  When Expression (6) is satisfied, the limit cycle auto-tuning calculation unit 6 sets Er1 = Ermax, that is, the maximum deviation Ermax as the first extreme value deviation Er1. Further, the limit cycle auto-tuning calculation unit 6 sets the time from the time when the previous equation (6) is established to the latest time when the maximum deviation Ermax is updated as the first manipulated variable switching elapsed time Th1 (step S204). In addition, when Formula (6) is materialized for the first time, the 1st operation amount switching elapsed time Th1 is set to 0.

  Further, switching of the sign of the deviation Er means that the manipulated variable MV is switched from the upper limit value OH_AT to the lower limit value OL_AT, or from the lower limit value OL_AT to the upper limit value OH_AT. The time measuring unit 8 sets the operation amount MV output from the operation amount MV output unit 3 from the previous switching time to the current switching time as the operation amount upper / lower limit value output time (step S204). When the manipulated variable MV is switched from the lower limit value OL_AT to the upper limit value OH_AT by this switching, the measured output time is the manipulated variable lower limit value output time T_OL, and the manipulated variable MV is changed from the upper limit value OH_AT to the lower limit value OL_AT. Needless to say, the output time measured is the manipulated variable upper limit value output time T_OH. It should be noted that the operation amount upper and lower limit value output time cannot be measured when Equation (6) is established for the first time.

  Next, the limit cycle auto-tuning calculation unit 6 determines whether or not the vertical movement extreme value detection completion condition is satisfied (step S205). In the present embodiment, the detection of four extreme values of the controlled variable PV is set as the vertical movement extreme value detection completion condition. Here, since only one extreme value of the control amount PV is detected, it is determined that the vertical movement extreme value detection is not completed, the maximum deviation Ermax is initialized to 0 (step S206), and the process returns to step S101.

  Steps S101 to S103 and S104 (steps S200 to S203) are repeated for each control cycle, and when time t3 in FIG. 9 is reached, equation (6) is established again. When the equation (6) is established, the limit cycle auto-tuning calculation unit 6 assigns Er2 = Er1, Er1 = Ermax, Th2 = Th1, that is, the value of the first extreme value deviation Er1 to the second extreme value deviation Er2. Then, the maximum deviation Ermax is set as a new first extreme value deviation Er1, and the value of the first manipulated variable switching elapsed time Th1 is substituted into the second manipulated variable switching elapsed time Th2. Further, the limit cycle auto-tuning calculation unit 6 sets the time from the time t1 when the previous equation (6) is established to the latest time t2 when the maximum deviation Ermax is updated as a new first manipulated variable switching elapsed time Th1 ( Step S204).

Further, the time measuring unit 8 sets the time from the previous switching time t1 of the operation amount MV to the current switching time t3 as the operation amount lower limit value output time T_OL (step S204).
Next, the limit cycle auto-tuning calculation unit 6 determines whether or not the vertical movement extreme value detection completion condition is satisfied (step S205). Here, since only two extreme values of the control amount PV are detected, it is determined that the vertical movement extreme value detection is not completed, the maximum deviation Ermax is initialized to 0 (step S206), and the process returns to step S101.

  When the processing of steps S101 to S104 is repeated for each control cycle and time t5 in FIG. 9 is reached, equation (6) is established again. When Expression (6) is established, the limit cycle auto-tuning calculation unit 6 determines that the third extreme value is the value of the second extreme value deviation Er2, that is, Er3 = Er2, Er2 = Er1, Er1 = Ermax, Th2 = Th1. The first manipulated variable switching elapsed time is assigned to the deviation Er3, the value of the first extreme value deviation Er1 is assigned to the second extreme value deviation Er2, and the maximum deviation Ermax is set as the new first extreme value deviation Er1. The value of Th1 is substituted for the second manipulated variable switching elapsed time Th2. Further, the limit cycle auto-tuning calculation unit 6 sets the time from the time t3 when the previous equation (6) is established to the latest time t4 when the maximum deviation Ermax is updated as a new first manipulated variable switching elapsed time Th1 ( Step S204).

The time measuring unit 8 sets the operation amount MV from the previous switching time t3 to the current switching time t5 as the operation amount upper limit output time T_OH (step S204).
Next, the limit cycle auto-tuning calculation unit 6 determines whether or not the vertical movement extreme value detection completion condition is satisfied (step S205). Here, since only three extreme values of the control amount PV are detected, it is determined that the vertical movement extreme value detection is not completed, the maximum deviation Ermax is initialized to 0 (step S206), and the process returns to step S101.

  When the processes of steps S101 to S104 are repeated for each control cycle and time t7 in FIG. 9 is reached, equation (6) is established again. When Expression (6) is satisfied, the limit cycle auto-tuning calculation unit 6 sets Er3 = Er2, Er2 = Er1, Er1 = Ermax, Th2 = Th1, and the maximum deviation Ermax from the time t5 when Expression (6) is satisfied last time. The time until the updated latest time t6 is set as a new first operation amount switching elapsed time Th1 (step S204).

  The time measuring unit 8 sets the operation amount MV from the previous switching time t5 to the current switching time t7 as the operation amount lower limit output time T_OL (step S204). Note that when the manipulated variable lower limit value output time T_OL or the manipulated variable upper limit value output time T_OH has already been measured, the current value is adopted as the measured value.

  Next, the limit cycle auto-tuning calculation unit 6 determines whether or not the vertical movement extreme value detection completion condition is satisfied (step S205). Here, since four extreme values of the control amount PV have been detected, it is determined that the vertical movement extreme value detection has been completed, the maximum deviation Ermax is initialized to 0 (step S207), and the process proceeds to step S105. Although the extreme value of the control amount PV necessary for calculating the PID parameter is originally three, the first extreme value may be an inappropriate value for the parameter calculation. Are detected.

  After the detection of the vertical movement extreme value is completed, the limit cycle auto-tuning calculation unit 6 calculates a control parameter (PID parameter in the present embodiment) of the control calculation unit 23 of the controller (step S105). The limit cycle auto-tuning calculation unit 6 calculates the proportional band Pb, the integration time Ti, and the differentiation time Td according to the above formulas (2), (3), and (4), respectively. Then, the limit cycle auto-tuning calculation unit 6 sets the calculated proportional band Pb, integration time Ti, and differentiation time Td in the control calculation unit 23. The PID parameter calculation process is thus completed. The limit cycle auto-tuning calculation unit 6 temporarily stops operation until the next restart.

Next, the ratio RT calculation unit 9 calculates a ratio RT = T_OH / T_OL between the operation amount upper limit value output time T_OH and the operation amount lower limit value output time T_OL (step S106).
The determination unit 10 determines whether or not the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT are appropriately set (step S107). When the ratio RT is larger than the preset threshold C1 (YES in step S108), the determination unit 10 determines that the operation amount lower limit value OL_AT is too low and determines the operation amount lower limit value with respect to the two-position operation amount correction unit 11. Instructs modification of OL_AT. Further, when the ratio RT is smaller than the preset threshold C2 (YES in step S109), the determination unit 10 determines that the operation amount upper limit value OH_AT is too high, and determines the operation amount with respect to the two-position operation amount correction unit 11. The correction of the upper limit value OH_AT is instructed. The threshold values C1 and C2 are, for example, C1 = 2 and C2 = 0.5.

  When the ratio RT is equal to or less than the threshold value C1 and equal to or greater than the threshold value C2, the determination unit 10 determines that the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT are appropriately set, and ends limit cycle auto-tuning.

2 position operation amount correcting unit 11, if the determination unit 10 receives the correction instruction of the operating amount lower limit OL_AT, calculates a correction value OL_AT _{new new} manipulated variable lower limit as in the following equation, the correction value OL_AT _{new new} Output to the 2-position operation amount lower setting unit 4. The two-position manipulated variable lower setting unit 4 sets the correction value OL_AT _new in the limit cycle auto-tuning calculating unit 6 as a new value of the manipulated variable lower limit value OL_AT (step S110).
OL_AT _new = OL_AT + (OH_AT-OL_AT) (RT-1)
/ (RT + 1) (7)

When the manipulated variable lower limit value OL_AT is relatively too low, an appropriate average value of the manipulated variable lower limit value OL_AT and the manipulated variable upper limit value OH_AT is, as shown in FIG. 5, the distance from the average value to the manipulated variable lower limit value OL_AT. The ratio between the average value and the distance from the operation amount upper limit value OH_AT to the distance is RT: 1. Therefore, if the difference between the manipulated variable upper limit value OH_AT and the manipulated variable lower limit value OL_AT is divided into (RT + 1) divided by (RT + 1) and multiplied by (RT-1), the manipulated variable change is added to the manipulated variable lower limit value OL_AT. The value OL_AT _new is obtained. Equation (7) is based on the principle of such correction. Equation (7) is an approximate correction equation obtained assuming that the manipulated variable MV and the control amount PV are in a linear relationship. When nonlinearity or a correction margin is taken into consideration, the equation (7) is appropriately changed. Reflect it. The coefficient portion (RT-1) / (RT + 1) for determining the correction amount in the equation (7) is a theoretically optimal positive value, but in the equation (7), (RT-1) / (RT + 1) An arbitrary positive value β1 may be used instead of (). At this time, 0 <β1 ≦ (RT−1) / (RT + 1) is a theoretically appropriate range.

Further, when receiving a correction instruction for the operation amount upper limit value OH_AT from the determination unit 10, the two-position operation amount correction unit 11 calculates a correction value OH_AT _new of the operation amount upper limit value as in the following equation, and this correction value OH_AT _New is output to the 2-position manipulated variable upper setting unit 5. The two-position manipulated variable upper setting unit 5 sets the correction value OH_AT _new as a new value of the manipulated variable upper limit value OH_AT in the limit cycle auto-tuning calculating unit 6 (step S111).
OH_AT _new = OH_AT + (OH_AT-OL_AT) (RT-1)
/ (RT + 1) (8)

When the manipulated variable upper limit value OH_AT is relatively too high, an appropriate average value of the manipulated variable lower limit value OL_AT and the manipulated variable upper limit value OH_AT is, as shown in FIG. 6, the distance from the average value to the manipulated variable lower limit value OL_AT. The ratio between the average value and the distance from the operation amount upper limit value OH_AT is 1: 1 / RT. Therefore, the operation amount change amount obtained by dividing the difference OH_AT−OL_AT between the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT into (1 / RT + 1) and multiplying by (1 / RT−1) is calculated from the operation amount upper limit value OH_AT. By subtracting, the corrected value OH_AT _new is obtained. Expression (8) is a modification of the following expression (9). Equations (8) and (9) are approximate correction equations obtained assuming that the manipulated variable MV and the control amount PV are in a linear relationship, and when nonlinearity and a correction margin are considered. May be appropriately reflected in the correction formula. The coefficient portion (RT-1) / (RT + 1) for determining the correction amount in the equation (8) is a theoretically optimal negative value, but in the equation (8), (RT-1) / (RT + 1) Any negative value β2 may be used instead of (). At this time, (RT-1) / (RT + 1) ≦ β2 <0 is a theoretically appropriate range.
OH_AT _new = OH_AT- (OH_AT-OL_AT) (1 / RT-1)
/ (1 / RT + 1) (9)

  After step S110 or S111 ends, the restart instruction unit 12 sends a limit cycle auto-tuning restart instruction command to the limit cycle auto-tuning calculation unit 6. Thereby, it returns to step S100 and the limit cycle auto-tuning calculating part 6 restarts. In this way, the processes in steps S100 to S111 are repeated until the determination in step S109 is NO and the correction of the operation amount lower limit value OL_AT and the operation amount upper limit value OH_AT is completed.

  It should be noted that the number of restarts is limited to a pre-specified number, and after restarting a predetermined number of times regardless of whether or not the correction of the operation amount lower limit value OL_AT and the operation amount upper limit value OH_AT has been completed, restart the operation. Instead, the process of FIG. 3 may be terminated in step S110 or S111.

In a normal control operation after the end of limit cycle auto-tuning, the control / control calculation unit 23 of the controller uses the set value SP input from the set value SP input unit 20 and the control amount PV input from the control amount PV input unit 21. Based on this, a feedback control calculation such as the following equation is performed to calculate the manipulated variable MV for each control cycle. That is, the control calculation unit 23 calculates the operation amount MV so that the control amount PV matches the set value SP.
MV = (α / Pb) {1+ (1 / Tis) + Tds} (SP−PV) (10)
In Expression (10), s is a Laplace operator, α is a constant, for example, α = 100. The operation amount MV calculated by the control calculation unit 23 is output to the control target via the operation amount output unit 22.

  As described above, in this embodiment, the operation amount lower limit value OL_AT and the operation amount upper limit value are determined based on the output time of the operation amount lower limit value OL_AT and the operation amount upper limit value OH_AT that are output during the execution of limit cycle auto-tuning. It can be automatically determined whether or not the value OH_AT is set appropriately. As a result, it is possible to greatly reduce the possibility of overlooking that the controller auto-tuning is inappropriate.

  In the present embodiment, when it is determined that the upper and lower limit values of the operation amount are inappropriate, at least one of the operation amount lower limit value OL_AT and the operation amount upper limit value OH_AT can be automatically corrected. Furthermore, in the present embodiment, auto-tuning can be automatically re-executed by restarting the limit cycle auto-tuning calculation unit 6 after correcting the manipulated variable lower limit value OL_AT and the manipulated variable upper limit value OH_AT. As a result, it is possible to appropriately set the control parameters of the controller, and further modification of the operation amount lower limit value OL_AT and the operation amount upper limit value OH_AT is possible.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 7 is a block diagram showing the configuration of the auto-tuning apparatus according to the second embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals. The present embodiment is based on the second method.
7 includes a set value SP input unit 1, a control amount PV input unit 2, an operation amount MV output unit 3, a two-position operation amount lower setting unit 4, and a two-position operation amount upper setting unit. 5, the absolute value of the latest first extreme value deviation Er1 among the extreme value deviations detected during the execution of the limit cycle autotuning, the start instruction unit 7, and the limit cycle autotuning A ratio RE calculation unit 9a that calculates a ratio RE to the absolute value of the second extreme value deviation Er2 detected immediately before the first extreme value deviation Er1, and an operation amount upper limit value OH_AT and an operation amount lower limit based on the ratio RE A determination unit 10a for determining whether or not the setting of the value OL_AT is appropriate; and when the setting of the operation amount upper limit value OH_AT or the operation amount lower limit value OL_AT is determined to be inappropriate, the operation amount upper limit value OH_AT and the operation amount lower limit value OL A correction value estimated to be appropriate for at least one of the ATs is calculated, and an operation amount upper limit value OH_AT set by the two-position operation amount lower setting unit 4 and an operation amount lower limit set by the two-position operation amount upper setting unit 5 A two-position operation amount correction unit 11a that updates at least one of the values OL_AT to a correction value, and a restart instruction unit 12 are provided.

The configuration of the controller to be tuned by the auto tuning apparatus of the present embodiment is as shown in FIG.
Next, the limit cycle auto-tuning function of the auto-tuning device of this embodiment will be described. FIG. 8 is a flowchart showing an operation of the auto tuning device when limit cycle auto tuning is executed. The same reference numerals are given to the same processes as those in FIG.

The processes in steps S100 to S105 are the same as those in the first embodiment. After step S105 is completed, the ratio RE calculation unit 9a calculates a ratio RE between the absolute value of the first extreme value deviation Er1 and the absolute value of the second extreme value deviation Er2 (step S112). At this time, when the first extreme value deviation Er1 is the maximum value and the second extreme value deviation Er2 is the minimum value, the ratio RE calculation unit 9a becomes the denominator as shown in the following equation. The ratio RE is calculated so that the deviation on the minimum value side becomes a numerator.
RE = | Er2 | / | Er1 | (11)

Further, the ratio RE calculating unit 9a replaces the denominator and the numerator of the equation (11) when the first extreme value deviation Er1 is the minimum value and the second extreme value deviation Er2 is the maximum value. The ratio RE is calculated as follows.
RE = | Er1 | / | Er2 | (12)

  The determination unit 10a determines whether or not the operation amount upper limit value OH_AT and the operation amount lower limit value OL_AT are appropriately set (step S113). When the ratio RE is larger than the preset threshold C3 (YES in step S114), the determination unit 10a determines that the operation amount lower limit value OL_AT is too low, and determines the operation amount lower limit value with respect to the two-position operation amount correction unit 11a. Instructs modification of OL_AT. Further, when the ratio RE is smaller than the preset threshold C4 (YES in step S115), the determination unit 10a determines that the operation amount upper limit value OH_AT is too high, and determines the operation amount with respect to the two-position operation amount correction unit 11a. Instructs the correction of the upper limit value OH_AT. The threshold values C3 and C4 are, for example, C3 = 2 and C4 = 0.5.

When the two-position operation amount correction unit 11a receives a correction instruction for the operation amount lower limit value OL_AT from the determination unit 10a, the two-position operation amount correction unit 11a calculates a correction value OL_AT _new of the operation amount lower limit value as in the following equation, and uses this correction value OL_AT _new . Output to the 2-position operation amount lower setting unit 4. The two-position manipulated variable lower setting unit 4 sets the correction value OL_AT _new in the limit cycle auto-tuning calculating unit 6 as a new value of the manipulated variable lower limit value OL_AT (step S116).
OL_AT _new = OL_AT + (OH_AT-OL_AT) (RE-1)
/ (RE + 1) (13)
Expression (13) is based on the same principle of correction of the manipulated variable lower limit value OL_AT as in the first embodiment, and is obtained as a result of replacing RT: 1 with RE: 1 in FIG. The coefficient portion (RE-1) / (RE + 1) for determining the correction amount in the equation (13) is a theoretically optimal positive value, but in the equation (13), (RE-1) / (RE + 1) ) May be used as an arbitrary positive value β3. At this time, 0 <β3 ≦ (RE−1) / (RE + 1) is a theoretically appropriate range.

When the two-position operation amount correction unit 11a receives a correction instruction for the operation amount upper limit value OH_AT from the determination unit 10a, the two-position operation amount correction unit 11a calculates a correction value OH_AT _new for the operation amount upper limit value as shown in the following equation. _New is output to the 2-position manipulated variable upper setting unit 5. The 2-position manipulated variable upper side setting unit 5 sets the correction value OH_AT _new as a new value of the manipulated variable upper limit value OH_AT in the limit cycle auto-tuning calculating unit 6 (step S117).
OH_AT _new = OH_AT + (OH_AT-OL_AT) (RE-1)
/ (RE + 1) (14)
Expression (14) is based on the same principle of correction of the manipulated variable upper limit value OH_AT as in the first embodiment, and is obtained as a result of replacing 1: 1 / RT with 1: 1 / RE in FIG. It is. The coefficient part (RE-1) / (RE + 1) for determining the correction amount in the equation (14) is a theoretically optimal negative value, but in the equation (14), (RE-1) / (RE + 1) Any negative value β4 may be used instead of (). At this time, (RE-1) / (RE + 1) ≦ β4 <0 is a theoretically appropriate range.

The operation of the restart instruction unit 12 after the end of step S116 or S117 is as described in the first embodiment.
Thus, in this embodiment, the same effect as that of the first embodiment can be obtained.

  The present invention can be applied to controller parameter adjustment such as PID.

It is a block diagram which shows the structure of the auto tuning apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the controller made into the tuning object by the auto tuning apparatus of FIG. It is a flowchart which shows the operation | movement at the time of limit cycle auto tuning execution of the auto tuning apparatus of FIG. It is a flowchart which shows the vertical motion extreme value detection process of the limit cycle auto-tuning calculating part of FIG. It is a figure for demonstrating the correction process of the operation amount lower limit in the 1st Embodiment of this invention. It is a figure for demonstrating the correction process of the operation amount upper limit in the 1st Embodiment of this invention. It is a block diagram which shows the structure of the auto tuning apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of limit cycle auto tuning execution of the auto tuning apparatus of FIG. It is a wave form diagram for demonstrating the limit cycle system which is a typical system of the conventional auto tuning function. It is a flowchart which shows the flow of a process of a limit cycle system. It is a wave form diagram for demonstrating the problem of the conventional limit cycle system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,20 ... Set value SP input part, 2, 21 ... Control amount PV input part, 3, 22 ... Operation amount MV output part, 4 ... Two position operation amount lower side setting part, 5 ... Two position operation amount upper side setting part , 6 ... limit cycle auto-tuning calculation unit, 7 ... start instruction unit, 8 ... time measurement unit, 9 ... ratio RT calculation unit, 9a ... ratio RE calculation unit, 10, 10a ... determination unit, 11, 11a ... 2-position operation An amount correction unit, 12... A restart instruction unit, 23.

Claims (10)

In an auto-tuning device with a limit cycle auto-tuning function that sets the control parameters of the controller,
When the limit cycle auto-tuning is executed, an operation amount with a constant amplitude is output to the controlled object, a control parameter of the controller is calculated based on a control response according to the operation amount output, and the calculated control parameter is set in the controller Limit cycle auto-tuning calculation means,
And an operation amount upper / lower limit value setting determination unit for determining whether or not the setting of the upper and lower limit values of the operation amount is appropriate based on an output time of the operation amount output during execution of the limit cycle auto-tuning. Features an auto tuning device. In the auto tuning device according to claim 1,
The operation amount upper / lower limit value setting determination means includes:
A time measurement unit that measures an operation amount upper limit value output time during which the upper limit value of the operation amount is output during execution of the limit cycle auto-tuning and an operation amount lower limit value output time during which the lower limit value of the operation amount is output;
A ratio calculation unit that calculates a ratio between the operation amount upper limit value output time and the operation amount lower limit value output time;
An auto-tuning apparatus comprising: a determination unit that determines whether or not the setting of the upper and lower limit values of the operation amount is appropriate based on the ratio. In an auto-tuning device with a limit cycle auto-tuning function that sets the control parameters of the controller,
When the limit cycle auto-tuning is executed, an operation amount with a constant amplitude is output to the controlled object, a control parameter of the controller is calculated based on a control response according to the operation amount output, and the calculated control parameter is set in the controller Limit cycle auto-tuning calculation means,
And an operation amount upper / lower limit value setting determination means for determining whether or not the setting of the upper and lower limit values of the operation amount is appropriate based on a deviation of the control amount detected during the execution of the limit cycle auto-tuning. Auto tuning device to do. In the auto tuning device according to claim 3,
The operation amount upper / lower limit value setting determination means includes:
Among the extreme value deviations when the controlled variable reaches the maximum value or the minimum value during the execution of the limit cycle auto-tuning, the absolute value of the latest first extreme value deviation and immediately before the first extreme value deviation A ratio calculator that calculates a ratio of the detected absolute value of the second extreme value deviation;
An auto-tuning apparatus comprising: a determination unit that determines whether the setting of the upper and lower limit values of the operation amount is appropriate based on the ratio. In the auto-tuning device according to any one of claims 1 to 4,
Furthermore, when it is determined by the operation amount upper / lower limit value setting determination means that the setting of the upper / lower limit value of the operation amount is inappropriate, it is estimated that at least one of the upper limit value and the lower limit value of the operation amount is appropriate. An auto-tuning apparatus, comprising: an operation amount correction unit that calculates a correction value and updates an upper limit value or a lower limit value of the operation amount output from the limit cycle auto-tuning calculation unit to the correction value. In the auto tuning device according to claim 5,
Further, after the processing of the manipulated variable correcting means is completed, the limit cycle auto-tuning calculating means is restarted, the limit cycle auto-tuning calculating means, the manipulated variable upper / lower limit value setting determining means, the manipulated variable correcting means, An auto-tuning apparatus comprising restart instruction means for re-executing the process. In the auto tuning method that sets the control parameters of the controller by the limit cycle auto tuning method,
When the limit cycle auto-tuning is executed, an operation amount with a constant amplitude is output to the controlled object, a control parameter of the controller is calculated based on a control response according to the operation amount output, and the calculated control parameter is set in the controller Limit cycle auto-tuning calculation procedure,
An operation amount upper / lower limit value setting determination procedure for determining whether the setting of the upper and lower limit values of the operation amount is appropriate based on an output time of the operation amount output during execution of the limit cycle auto-tuning. A characteristic auto-tuning method. In the auto tuning method that sets the control parameters of the controller by the limit cycle auto tuning method,
When the limit cycle auto-tuning is executed, an operation amount with a constant amplitude is output to the controlled object, a control parameter of the controller is calculated based on a control response according to the operation amount output, and the calculated control parameter is set in the controller Limit cycle auto-tuning calculation procedure,
An operation amount upper / lower limit value setting determination procedure for determining whether or not the setting of the upper and lower limit values of the operation amount is appropriate based on a deviation of the control amount detected during the execution of the limit cycle auto-tuning. Auto tuning method to do. In the auto-tuning method according to claim 7 or 8,
Furthermore, when the setting of the upper and lower limit values of the operation amount is determined to be inappropriate by the operation amount upper and lower limit value setting determination procedure, it is estimated that at least one of the upper limit value and the lower limit value of the operation amount is appropriate. An auto-tuning method comprising an operation amount correction procedure for calculating a correction value and updating an upper limit value or a lower limit value of the operation amount to be output in the limit cycle auto-tuning calculation procedure to the correction value. The auto-tuning method according to claim 9, wherein
And a restart instruction procedure for re-executing the limit cycle auto-tuning calculation procedure, the manipulated variable upper / lower limit value setting determination procedure, and the manipulated variable modification procedure after the manipulated variable modification procedure is completed. Auto tuning method.

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