JP2009151521A - Pid parameter adjusting device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PID parameter adjusting device and method for surely preventing the generation of hunting. <P>SOLUTION: A PID parameter adjusting device 1 includes: an AT execution part 3 for calculating a PID parameter by a limit cycle type auto-tuning (AT) and setting it to a PID control device 2; a hunting suppression part 5 for correcting the PID parameter in order to suppress hunting when any hunting is generated in controlled variables PV after a PID control device 2 starts control to a control object based on the PID parameter; a setting detection part 6 for ending hunting detection and hunting suppression by the hunting suppression part 5 when the setting state of control is detected; and an AT calculation coefficient correction part 7 for correcting the calculation coefficient of the AT execution part 3 based on the change rate between the PID parameter before correction and the PID parameter after correction of the PID control device 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a process control technique, and more particularly to a PID parameter adjustment device and an adjustment method for adjusting a PID parameter of a PID control device.

  In control devices such as temperature controllers, a limit cycle type auto-tuning (hereinafter referred to as AT) function is widely adopted, and PID parameter values for PID control calculation are automatically determined thereby (for example, Patent Documents). 1). This limit cycle type AT is designed to adjust the PID parameter value by setting an upper limit value and a lower limit value in advance for the manipulated variable MV output to the controlled object, generating a limit cycle with a constant manipulated variable amplitude. It is.

JP 2006-106925 A

  In the conventional AT disclosed in Patent Document 1, the AT is terminated by generating a limit cycle in which the operation amount moves up and down a designated number of times. Then, the PID parameter value is determined based on the control response to the operation amount output, specifically, the information Ah related to the vertical movement width of the control amount PV and the information Th related to time. For this reason, strictly speaking, the “estimated value considered to be the best” based on a small amount of information is calculated. Therefore, depending on the control target, an appropriate PID parameter value may be calculated or an inappropriate PID parameter value may be calculated. A value may be calculated.

  At this time, in the case of the conventional AT, if the PID parameter value that is overly stable although it is inappropriate is calculated, the worst state that the control becomes unstable is avoided, When a PID parameter value that is unstable and has unstable control characteristics is calculated, there is a problem that a state called hunting occurs. Hunting is a state in which the control amount PV such as temperature and pressure does not settle to the set value SP, and may cause adverse effects such as a decrease in yield in the manufacturing process and a shortened life of the control device.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a PID parameter adjusting device and an adjusting method capable of reliably avoiding hunting.

The PID parameter adjusting device of the present invention outputs an operation amount having a constant amplitude to a controlled object, calculates a PID parameter based on a control response corresponding to the operation amount output and a preset calculation coefficient, and sets the PID parameter in the PID control device. Auto-tuning executing means, and when the hunting occurs in the controlled variable after the PID control device starts controlling the control object based on the PID parameter, the PID parameter of the PID control device is to suppress the hunting. And a settling detection means for ending the hunting detection and the hunting suppression by the hunting suppression means when the settling state of the control is detected.
Further, one configuration example of the PID parameter adjusting device according to the present invention is further configured based on a change ratio between the PID parameter before correction of the PID control device and the corrected PID parameter corrected by the hunting suppression unit. Calculation coefficient correction means for correcting the calculation coefficient of the tuning execution means is provided.
In addition, one configuration example of the PID parameter adjusting device of the present invention further includes notification means for notifying the user that the stability of the control has been confirmed when the settling state of the control is detected.

  The PID parameter adjustment method of the present invention outputs a manipulated variable having a constant amplitude to a controlled object, calculates a PID parameter based on a control response corresponding to the manipulated variable output and a preset calculation coefficient, and a PID control device. The auto-tuning execution procedure to be set to, and when the hunting occurs in the controlled variable after the PID control device starts controlling the control object based on the PID parameter, the PID control device A hunting suppression procedure for correcting the PID parameter, and a settling detection procedure for ending hunting detection and hunting suppression by the hunting suppression procedure when the settling state of the control is detected.

  According to the present invention, the hunting detection and the hunting suppression are executed only for a limited time after the auto-tuning operation is completed until the control settling state is detected. Therefore, the PID parameter correction can be appropriately performed without being affected by the control disturbance. As a result, in the present invention, the auto-tuning function and the hunting suppression function can be used together, and the occurrence of hunting can be reliably avoided.

  In the present invention, the calculation coefficient of the auto-tuning executing means is corrected based on the change ratio between the PID parameter before correction of the PID control device and the corrected PID parameter corrected by the hunting suppression means. When it becomes necessary to re-execute auto-tuning for some reason, it becomes possible to calculate the PID parameter that provides stable control characteristics by the auto-tuning executing means without relying on the hunting suppression function.

  Further, according to the present invention, when the settling state of PID control is detected, the user can recognize that the control target may be put into a production state by notifying the user that the stability of the control has been confirmed.

[Principle of Invention 1]
Japanese Patent Application Laid-Open Nos. 9-160604 and 10-105201 disclose a hunting suppression function (vibration determination function and suppression function) that can be mounted on a control device such as a temperature controller. This hunting suppression function is a function that automatically detects hunting and automatically corrects the PID parameter value when hunting occurs due to a change in the characteristics of the controlled object during execution of control. With this function, the problems of the conventional AT are solved. However, in many control systems, when a control amount disturbance is continuously applied during control execution and a situation that is difficult to distinguish from hunting occurs, automatic correction of the PID parameter value due to malfunction of the hunting suppression function results. Because of this possibility, the combined use of the AT and the hunting suppression function is not practical.

  The inventor grasped and considered this situation. In addition, the inventor of the present invention has focused on the fact that many operators of control devices such as a temperature controller start the AT in a state where no control amount disturbance is applied. That is, when the AT is activated, the manipulated variable MV is forcibly moved up and down, and the control amount PV is forcibly moved up and down accordingly, so that it is clear that an adverse effect in the manufacturing process occurs. Since the operator is aware of this, the AT is not activated during the production process. When the manufacturing process is not in full operation, there is no related operation such as peripheral devices, so that no disturbance is applied as a result. The inventor pays attention to this and executes the hunting suppression function only for a limited time until the automatic confirmation that hunting is not detected (settling detection) after the AT is started and the AT is terminated, thereby causing a disturbance. It was thought that it would be effective to solve the problem if appropriate hunting suppression that was not affected by the problem was made as needed.

[Principle of Invention 2]
The PID parameter value calculated by the AT is calculated using a specific calculation coefficient as disclosed in Patent Document 1, for example. On the other hand, in the correction of the PID parameter value by the hunting suppression function, it is possible to give the change ratio of the PID parameter value before and after the correction. Therefore, if this change ratio is reflected in the calculated coefficient, the calculated coefficient itself can be automatically corrected. In that case, when AT has to be re-executed for some reason, it is possible to calculate a PID parameter value that provides stable control characteristics without relying on the hunting suppression function basically.

[Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a PID parameter adjusting apparatus according to an embodiment of the present invention.
The PID parameter adjusting device 1 calculates a PID parameter by a limit cycle type AT, an AT execution unit 3 that sets the calculated PID parameter in the PID control device 2, an AT completion processing unit 4 that outputs an AT completion notification, After the PID control device 2 starts control of the controlled object based on the PID parameter, when hunting occurs in the control amount PV, the hunting suppression unit 5 that corrects the PID parameter to suppress this hunting, and control stabilization When the state is detected, the hunting detection unit 6 terminates hunting detection and hunting suppression, the PID parameter before correction of the PID control device 2 and the corrected PID corrected by the hunting suppression unit 5 A for correcting the calculation coefficient of the AT execution unit 3 based on the change ratio with the parameter A And a calculation coefficient modification unit 7. The settling detection unit 6 constitutes notification means for notifying the user that the stability of the control has been confirmed when the settling state of the control is detected.

  FIG. 2 is a diagram showing an example of a temperature control system to which the PID parameter adjusting device 1 and the PID control device 2 of the present embodiment are applied. In the example of FIG. 2, a heater 12 and a temperature sensor 13 are installed inside the heat treatment furnace 11. The temperature sensor 13 measures the temperature PV of the air heated by the heater 12. The temperature controller 10 calculates the manipulated variable MV so that the temperature PV matches the set value SP. The power adjuster 14 determines power according to the operation amount MV, and supplies the determined power to the heater 12 through the power supply circuit 15. Thus, the temperature controller 10 controls the temperature in the heat treatment furnace 11. The PID parameter adjusting device 1 and the PID control device 2 are provided inside the temperature controller 10.

Hereinafter, operations of the PID parameter adjusting device 1 and the PID control device 2 will be described. FIG. 3 is a flowchart showing the operation of the PID parameter adjusting device 1 and the PID control device 2, and FIG. 4 is a waveform diagram for explaining the limit cycle type AT used in the present embodiment.
The set value SP is set by the operator and input to the PID parameter adjusting device 1 and the PID control device 2. The control amount PV is detected by a sensor (not shown) and input to the PID parameter adjusting device 1 and the PID control device 2.

  For example, when the AT function is activated in accordance with an operator instruction (step S1 in FIG. 3), the AT execution unit 3 generates a limit cycle (step S2). That is, when the control amount PV is larger than the set value SP, the AT execution unit 3 outputs a predetermined operation amount lower limit set value AL to the control target as the operation amount MV, and when the control amount PV is equal to or less than the set value SP. The predetermined operation amount upper limit setting value AU is output as the operation amount MV to the control target until the vertical movement of the operation amount MV reaches a predetermined number of times. Thus, a limit cycle in which the amplitude of the manipulated variable MV is constant as shown in FIG. 4 occurs. In the case of the example in FIG. 2, it goes without saying that the output destination of the manipulated variable MV is the power regulator 14.

  Subsequently, the AT execution unit 3 performs a vertical movement extreme value detection process (step S3). In this vertical movement extreme value detection process, as shown in FIG. 4, the AT execution unit 3 performs a first extreme value deviation that is a deviation (SP−PV) between the set value SP and the latest extreme value of the control amount PV. Er1, the second extreme value deviation Er2, which is the deviation between the set value SP and the second new extreme value of the controlled variable PV, and the first time t5 when the positive and negative deviations are reversed immediately before the first extreme value deviation Er1. The first manipulated variable switching elapsed time Th1, which is the time until the time t6 when the extreme value deviation Er1 is obtained, and the second extreme value from the time t3 when the deviation is reversed immediately before the second extreme value deviation Er2. A second manipulated variable switching elapsed time Th2, which is the time until time t4 when the deviation Er2 is obtained, is obtained.

Next, the AT execution unit 3 calculates the control response result detected in the vertical motion extreme value detection process and the calculation coefficients α0, β0, γ0 (for example, α0 = 1, β0 = 1) predetermined for calculating the PID parameter value. , Γ0 = 1), the PID parameter is calculated as follows (step S4).
Pb0 = 100.0α0 | Er2-Er1 | / {0.9 (AU-AL)} (1)
Ti0 = β0 (Th1 + Th2) (2)
Td0 = 0.21γ0 (Th1 + Th2) (3)
Then, the AT execution unit 3 sets the calculated proportional band Pb0, integration time Ti0, and differentiation time Td0 in the PID control device 2. This completes the AT. Details of the AT are disclosed in, for example, Patent Document 1 and Japanese Patent Application Laid-Open No. 2003-330504.

When the AT is completed, the AT completion processing unit 4 notifies the PID control device 2, the hunting suppression unit 5, and the settling detection unit 6 that the AT has been completed (step S5).
The PID control device 2 that has received the AT completion notification calculates the manipulated variable MV based on the set value SP and the controlled variable PV and outputs the manipulated variable MV to the control target for each control cycle (step S6). ).
MV = (ζ / Pb0) {1+ (1 / Ti0s) + Td0s} (SP−PV)
... (4)
In Expression (4), s is a Laplace operator, and the constant ζ is 100, for example. Like the AT, in the case of the example of FIG. 2, it goes without saying that the output destination of the manipulated variable MV is the power regulator 14.

On the other hand, when an AT completion notification is received from the AT completion processing unit 4, the hunting suppression unit 5 and the settling detection unit 6 are activated.
When the hunting suppression unit 5 detects that hunting (vibration) has occurred in the control amount PV (YES in step S7), the PID parameters (proportional band Pb0, integration time Ti0, differentiation time Td0) of the PID control device 2 are detected. Is corrected to suppress hunting (step S8). Hunting suppression methods are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 9-160604 and 10-105201.

  Next, the settling detection unit 6 determines whether or not the control is set based on the set value SP and the control amount PV (step S9). In this way, the processing of steps S6 to S9 is repeated for each control cycle. The settling determination method is disclosed in, for example, Japanese Patent Laid-Open No. 9-160604.

  When the settling detection unit 6 detects that the control is in a settling state, the settling detection unit 6 terminates the operation of the hunting suppression unit 5 (hunting detection and hunting suppression) (step S10) and confirms that the stability of the control is confirmed. The user is notified (step S11). The notification at this time may be a character display, a voice notification, or a blinking LED. By this notification, the user can confirm that the control target may be put in the actual operation state. That is, in the present embodiment, appropriate hunting suppression that is not affected by disturbance is performed as necessary before the actual operation state is entered.

Finally, the AT calculation coefficient correction unit 7 corrects the calculation coefficients α0, β0, and γ0 set in the AT execution unit 3 (step S12). Of the latest PID parameters corrected by the hunting suppression unit 5 (PID parameters corrected at or immediately before the settling state is detected), the proportional band is Pb1, the integration time is Ti1, and the differential time is Td1. The coefficients are α1, β1, and γ1. At this time, the calculation coefficients α1, β1, and γ1 are calculated as follows.
α1 = α0 (Pb1 / Pb0) (5)
β1 = β0 (Ti1 / Ti0) (6)
γ1 = γ0 (Td1 / Td0) (7)

Then, the AT calculation coefficient correction unit 7 corrects the calculation coefficients α0, β0, and γ0 set in the AT execution unit 3 to α1, β1, and γ1, respectively. Here, Pb1 / Pb0, Ti1 / Ti0, and Td1 / Td0 correspond to the change ratio of the PID parameter value.
Thus, the process of the PID parameter adjusting device 1 is completed. Thereafter, the PID control device 2 performs the same PID control as in step S6.

  As described above, in the present embodiment, hunting detection and hunting suppression are executed only for a limited time after the AT is completed until the control settling state is detected. PID parameter correction for suppression can be appropriately performed without being affected by control disturbance. The reason for not being affected by the disturbance is that the control target at the time of AT execution is generally not in the active state. For example, in the case of the heat treatment furnace 11 of FIG. 2, the product to be heated is carried into the heat treatment furnace 11 in the actual operation state, but the product is not carried in the state before the operation state. As a result, in this embodiment, the AT function and the hunting suppression function can be used together, and the occurrence of hunting can be reliably avoided.

  Further, in the present embodiment, the calculation coefficient of the AT execution unit 3 is corrected based on the change ratio between the PID parameter before correction of the PID control device 2 and the corrected PID parameter corrected by the hunting suppression unit 5. Therefore, when the AT has to be re-executed for some reason, it becomes possible to calculate the PID parameter that provides stable control characteristics by the AT execution means without relying on the hunting suppression function. That is, when AT is re-executed, the hunting suppression function does not have to be re-executed, and the time required for the settling state can be shortened even when hunting suppression is re-executed.

  The PID parameter adjustment device 1 and the PID control device 2 described in the present embodiment can be realized by a computer having a CPU, a storage device, and an interface, and a program for controlling these hardware resources. The CPU executes the processing described in the present embodiment in accordance with a program stored in the storage device.

  The present invention can be applied to parameter adjustment of a PID control device.

It is a block diagram which shows the structure of the PID parameter adjustment apparatus which concerns on embodiment of this invention. It is a figure which shows one example of the temperature control system to which the PID parameter adjustment apparatus and PID control apparatus of FIG. 1 are applied. It is a flowchart which shows operation | movement of the PID parameter adjustment apparatus and PID control apparatus which concern on embodiment of this invention. It is a wave form chart for explaining limit cycle type auto-tuning used in an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... PID parameter adjustment apparatus, 2 ... PID control apparatus, 3 ... AT execution part, 4 ... AT completion process part, 5 ... Hunting suppression part, 6 ... Settling detection part, 7 ... AT calculation coefficient correction part.

Claims (6)

Auto-tuning executing means for outputting an operation amount having a constant amplitude to a control object, calculating a PID parameter based on a control response according to the operation amount output and a preset calculation coefficient, and setting the PID parameter in the PID control device;
Hunting suppression means for correcting the PID parameter of the PID control device to suppress the hunting when the hunting occurs in the control amount after the PID control device starts control of the controlled object based on the PID parameter; ,
A PID parameter adjustment device comprising: a settling detection unit that terminates hunting detection and hunting suppression by the hunting suppression unit when the settling state of the control is detected. The PID parameter adjusting device according to claim 1, wherein
Furthermore, a calculation coefficient correction means for correcting the calculation coefficient of the auto-tuning execution means is provided based on the change ratio between the PID parameter before correction of the PID control device and the corrected PID parameter corrected by the hunting suppression means. A PID parameter adjusting device characterized by the above. The PID parameter adjusting device according to claim 1, wherein
The PID parameter adjusting apparatus further comprising a notification means for notifying a user that the stability of the control has been confirmed when the settling state of the control is detected. An auto-tuning execution procedure for outputting an operation amount having a constant amplitude to a control target, calculating a PID parameter based on a control response according to the operation amount output and a preset calculation coefficient, and setting the PID parameter in the PID control device;
A hunting suppression procedure for correcting the PID parameter of the PID control device to suppress the hunting when the hunting occurs in the control amount after the PID control device starts control of the controlled object based on the PID parameter; ,
A PID parameter adjustment method comprising: a setting detection procedure for ending hunting detection and hunting suppression by the hunting suppression procedure when a settling state of the control is detected. The PID parameter adjustment method according to claim 4, wherein
And a calculation coefficient correction procedure for correcting the calculation coefficient of the auto-tuning execution procedure based on a change ratio between the PID parameter before correction of the PID control device and the corrected PID parameter corrected by the hunting suppression procedure. A PID parameter adjustment method characterized by the above. The PID parameter adjustment method according to claim 4, wherein
The PID parameter adjustment method further comprising a notification procedure for notifying the user that the stability of the control has been confirmed when the settling state of the control is detected.

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