JP2007286895A - Pid controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PID controller for shortening a termination time of automatic tuning. <P>SOLUTION: An automatic tuning execution means 13 is provided with a manipulated variable output means outputting a manipulated variable with a fixed amplitude to a control target, an acquisition means acquiring a dead time, as a duration required for a controlled variable to reach a maximum/minimum value after the manipulated variable is changed, and amplitude of the controlled variable as a difference between the maximum/minimum value and a set value, a determination means making the manipulated variable output means finish a limit cycle when the dead time substantially matches its value of a previous cycle and the amplitude of the controlled variable acquired simultaneously with the dead time matches its value of a previous cycle, and a PID parameter calculation means calculating a PID parameter based on the dead time and the amplitude given when the manipulated variable is changed from ON to OFF and those given when the controlled variable is changed from OFF to ON. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a process control technique, and in particular, generates a limit cycle that repeatedly outputs a manipulated variable having a constant amplitude to a controlled object, and sets a PID parameter based on a response of the controlled object according to the output of the manipulated variable. The present invention relates to a PID control device having an auto-tuning function to be calculated.

  Conventionally, an auto-tuning function has been proposed as a technique for setting a PID parameter of a PID control device to an appropriate value (see, for example, Patent Document 1 and Patent Document 2).

JP 2004-13542 A Japanese Patent No. 2588202

  According to auto-tuning, the PID parameter can be set to an optimum value in accordance with the characteristics of the controlled object. However, when the response of the controlled object is slow, such as temperature control of an electric furnace or the like, there is a problem that it takes a long time to finish once auto-tuning is executed. In recent years, energy saving has been emphasized, and even in electric furnaces, etc., heat insulation is high, so there is an increasing number of devices that heat up quickly but have a very slow temperature drop. Was desired to finish early.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a PID control device that can shorten the end time of auto-tuning.

The present invention has an auto-tuning function that generates a limit cycle that repeatedly outputs a manipulated variable having a constant amplitude to a controlled object, and calculates a PID parameter based on the response of the controlled object according to the output of the manipulated variable. In the PID control device, an operation amount output means for outputting an operation amount having a constant amplitude to the controlled object at the time of execution of the auto tuning, and an amount of operation changed by observing the control amount at the time of execution of the auto tuning. Acquisition means for acquiring a dead time that is a time required until the control amount reaches a maximum value or a minimum value from time to time, and an amplitude of the control amount that is a difference between the maximum value or the minimum value and a set value of control; When the dead time substantially coincides with the value one cycle before, and the amplitude of the control amount acquired simultaneously with the dead time substantially coincides with the value one cycle before A determination means for causing the manipulated variable output means to end the limit cycle; and the dead time and amplitude when the manipulated variable changes from on to off when the limit cycle is completed, and the manipulated variable is turned on from off. And a PID parameter calculating means for calculating a PID parameter based on the dead time and amplitude when changed to.
Further, in one configuration example of the PID control device according to the present invention, the acquisition means has the same polarity as that at the first change when the operation amount is changed from an initial value and the operation amount is changed at the first change when the auto tuning is executed. The control unit obtains the slope of the control amount when the change is made, and the determination unit causes the manipulated variable output unit to end the limit cycle when the slope of the control amount substantially coincides with a value one cycle before. Is.

In addition, the PID control device of the present invention includes an operation amount output means for outputting an operation amount having a constant amplitude to the controlled object at the time of execution of the auto tuning, and a control amount at the time of execution of the auto tuning. The slope of the control amount when the manipulated variable changes from the initial value at the time of tuning, the slope of the controlled variable when the manipulated variable has the same polarity as the initial change, and when the manipulated variable changes An acquisition means for acquiring a dead time, which is a time required for the control amount to reach a maximum value or a minimum value, and an amplitude of the control amount, which is a difference between the maximum value or the minimum value and a control set value; and the limit When the number of cycles reaches a predetermined number of cycles, a determination unit that causes the operation amount output unit to end the limit cycle, and a control amount acquired at the end of the limit cycle. And an estimation means for estimating an amplitude of the control amount that should appear after the end time from the dead time when the manipulated variable has changed in the same polarity as the end time in the past, and the limit cycle PID parameters are calculated on the basis of the past dead time, the amplitude of the estimated control amount, and the dead time and amplitude when the manipulated variable has the opposite polarity to that at the end. And a PID parameter calculation means.
Further, in one configuration example of the PID control device of the present invention, the estimation means obtains a tangent line of the control amount at the end from the slope of the control amount acquired at the end of the limit cycle, and from the end A height of the point on the tangent line when the past dead time has elapsed is obtained, and a value obtained by multiplying the height by a predetermined ratio is set as the amplitude of the control amount to be estimated.

  According to the present invention, when the dead time acquired at the time of execution of auto-tuning substantially matches the value one cycle before, and the amplitude of the control amount acquired simultaneously with the dead time substantially matches the value one cycle before. The PID parameter is calculated based on the dead time and amplitude when the manipulated variable changes from on to off and the dead time and amplitude when the manipulated variable changes from off to on after the limit cycle is completed. Therefore, the time required for auto-tuning can be shortened.

  In the present invention, the limit cycle is terminated when the slope of the control amount acquired at the time of executing the auto-tuning substantially coincides with the value one cycle before, so that the time required for auto-tuning can be further shortened. Can do.

  Further, in the present invention, the limit cycle is terminated when the limit cycle reaches a predetermined number of cycles, and the gradient of the control amount acquired at the end of the limit cycle and the manipulated variable change in the same polarity as at the end of the past. When the amplitude of the controlled variable that should appear after the end is estimated from the dead time at the end of the operation, the amplitude of the estimated amount of control past the dead time, and when the manipulated variable changes in reverse polarity from the end Since the PID parameter is calculated based on the dead time and amplitude, the time required for auto-tuning can be shortened.

  In the present invention, the tangent of the control amount at the end is obtained from the slope of the control amount acquired at the end of the limit cycle, and the height of the point on the tangent when the past dead time has elapsed from the end is obtained. By obtaining the value obtained by multiplying the height by a predetermined ratio as the amplitude of the control amount to be estimated, a PID parameter having no practical problem can be calculated using the estimated amplitude.

[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 PID control apparatus according to the first embodiment of the present invention. The PID control device 1 is used by a subtracting means 10 for calculating a deviation between the control amount PV and the set value SP, a PID calculating means 11 for calculating an operation amount MV so as to make the deviation zero, and a PID calculating means 11. Parameter storage means 12 for storing PID parameters, auto-tuning execution means 13 for storing optimum PID parameters in the parameter storage means 12 by performing auto-tuning, and switching for selecting either normal PID control or auto-tuning , The operation amount conversion means 15 that converts the operation amount output from the switching device 14 into an electrical signal and outputs it to the heater H to be controlled, and the setting for storing the control set value SP set from the outside Value storage means 16.

  The PID control device 1 of the present embodiment controls the temperature in the heating furnace 2 that is a control target. The temperature sensor S measures a control amount PV (temperature in the heating furnace 2) to be controlled. A set value SP (temperature set value) is set in the set value storage means 16 by, for example, an operator of the PID control device 1. The subtracting means 10 calculates the deviation between the control amount PV and the set value SP, and the PID calculating means 11 calculates the manipulated variable MV by performing PID control calculation so that the deviation becomes zero. During normal control, the switch 14 selects the output of the PID calculation means 11. The operation amount conversion means 15 converts the operation amount MV output from the PID calculation means 11 via the switch 14 into an electric signal and outputs it to the heater H. Thus, the heating amount of the heater H is controlled so that the temperature in the heating furnace 2 matches the temperature set value.

  Next, the operation of the PID control device 1 when executing auto-tuning will be described with reference to FIGS. FIG. 2 is a block diagram showing a configuration example of the auto-tuning execution means 13, FIG. 3 is a flowchart showing the operation of the PID control device 1 when auto-tuning is executed, and FIG. 4 is an operation output by the auto-tuning execution means 13 when auto-tuning is executed. It is a wave form diagram showing an example of change of amount of control MV according to amount MV and this amount of operation MV.

  The auto-tuning execution means 13 includes an operation amount output means 130 for generating a limit cycle for repeatedly outputting an operation amount MV having a constant amplitude to the controlled object when auto-tuning is executed, and the slope and dead time of the control amount PV when executing auto-tuning. And the acquisition means 131 for acquiring the amplitude, the determination means (acquisition means) 132 for ending the limit cycle when the limit cycle end condition is satisfied, and the slope, dead time and amplitude of the control amount PV acquired by the determination means 132 And a PID parameter calculation unit 134 for calculating a PID parameter based on the dead time and amplitude stored in the storage unit 133 when the limit cycle is completed.

The auto-tuning executing unit 13 starts auto-tuning in accordance with, for example, an operator instruction.
The operation amount output means 130 compares the control amount PV measured by the sensor S with the set value SP set in the set value storage means 16 during execution of auto-tuning (step S100 in FIG. 3), and the control amount PV is set. When the value is equal to or less than the value SP, a preset operation amount upper limit value MVH (for example, 100%) is output as the operation amount MV (step S101), and when the control amount PV is greater than the set value SP, a preset operation amount lower limit The value MVL (for example, 0%) is output as the manipulated variable MV (step S102). In the example of FIG. 4, since the control amount PV is equal to or less than the set value SP at the auto tuning start time t1, the operation amount output means 130 outputs the operation amount MV = MVH.

  When executing the auto tuning, the switcher 14 selects the output of the auto tuning executing means 13. As a result, the operation amount MV output from the operation amount output means 130 is output to the operation amount conversion means 15 via the switch 14.

Next, the determination unit 132 determines whether or not an inclination acquisition condition for obtaining the inclination of the control amount PV is satisfied (step S103). The inclination acquisition condition is satisfied when the manipulated variable MV changes from the initial value (MVH in the example of FIG. 4) after the start of auto-tuning and when the manipulated variable MV changes in the same polarity as the first changed value. To do. In the example of FIG. 4, since the manipulated variable MV changes from MVH to MVL (on to off) at time t2 after the start of auto-tuning, the slope acquisition condition is satisfied. Similarly, the inclination acquisition condition is satisfied at time t6.
The obtaining unit 131 obtains the slope of the control amount PV when the slope obtaining condition is satisfied, and stores the obtained slope value in the storage unit 133 (step S104).

In addition, the determination unit 132 determines whether a dead time acquisition condition for obtaining the dead time L of the control target and an amplitude acquisition condition for obtaining the amplitude A of the control amount PV are satisfied (step S105). The dead time acquisition condition and the amplitude acquisition condition are satisfied when the control amount PV takes a maximum value or a minimum value. However, these conditions are not satisfied for the first extreme value after the start of auto-tuning. The reason for excluding the first extreme value is that the first extreme value may be an inappropriate value for parameter calculation.
The acquisition unit 131 obtains the dead time L and the amplitude A of the control amount PV when the dead time acquisition condition and the amplitude acquisition condition are satisfied, and stores the obtained dead time L and the amplitude A in the storage unit 133 ( Step S106).

  In the example of FIG. 4, since the control amount PV reaches the maximum value at time t3, the acquisition unit 131 performs the operation from time t2 when the operation amount MV shifts from on to off to time t3 when the control amount PV reaches the maximum value. The required time is acquired as the dead time L1, and the amplitude A1 of the control amount PV at the time t3 is obtained, and the dead time L1 and the amplitude A1 are stored in the storage unit 133.

  Subsequently, the determination unit 132 determines whether or not the limit cycle end condition is satisfied (step S107). The limit cycle end condition is that the dead time L acquired in step S106 substantially coincides with the dead time L acquired one cycle before, and the amplitude A acquired in step S106 is substantially the same as the amplitude A acquired one cycle ago. It is established when they match. The limit cycle end condition is satisfied when the slope of the control amount PV acquired in step S104 substantially coincides with the slope of the control amount PV acquired one cycle before. Note that the determination unit 132 determines that the dead time substantially matches when the absolute value of the difference between the dead time acquired in step S106 and the dead time acquired one cycle before is within a predetermined range, and step S106. When the absolute value of the difference between the amplitude acquired in step 1 and the amplitude acquired one cycle before is within a predetermined range, it is determined that the amplitudes are substantially the same, and the slope of the control amount PV acquired in step S104 is one cycle before When the absolute value of the difference from the acquired control amount PV is within a predetermined range, it is determined that the inclinations are substantially the same.

  At time t3, only one can be acquired for each of the slope of the control amount PV, the dead time L, and the amplitude A. That is, at the time t3, it is not certain whether the dead time L and the amplitude A that are sufficient for reliability have been obtained. Therefore, the determination unit 132 determines in step S107 that the limit cycle end condition is not satisfied, and returns to step S100 to move to the next cycle. In this way, the processing of steps S100 to S107 is repeatedly executed at regular intervals until the limit cycle end condition is satisfied.

  Next, since the control amount PV reaches the minimum value at time t5, the acquisition unit 131 performs time t5 when the control amount PV reaches the minimum value from time t4 when the operation amount MV shifts from MVL to MVH (off to on). The time required up to is acquired as the dead time L2, and the amplitude A2 of the control amount PV at the time t5 is obtained, and the dead time L2 and the amplitude A2 are stored in the storage means 133 (step S106). Since the dead time L2 and the amplitude A2 obtained at time t5 are generally stable, they can be adopted as the measurement results of the limit cycle. At time t5, the dead time L and amplitude A one cycle before are not acquired, and the slope of the control amount PV is only the value obtained at time t2, so the limit cycle end condition is not satisfied.

  When the time t6 is reached, the manipulated variable MV shifts from on to off, and the inclination acquisition condition is satisfied. The obtaining unit 131 obtains the slope of the control amount PV at time t6, and stores the obtained slope value in the storage unit 133 (step S104). The determination unit 132 compares the slope of the control amount PV acquired at time t6 with the slope of the control amount PV acquired at time t2 one cycle before, and determines whether or not the limit cycle end condition is satisfied ( Step S107), here, it is assumed that the inclinations do not match.

  Next, since the control amount PV reaches the maximum value at time t7, the acquisition unit 131 calculates the required time from time t6 when the operation amount MV shifts from on to off to time t7 when the control amount PV reaches the maximum value. The dead time L3 is acquired, and the amplitude A3 of the control amount PV at the time t7 is obtained, and the dead time L3 and the amplitude A3 are stored in the storage means 133 (step S106). Then, the determination unit 132 substantially matches the dead time L3 acquired at time t7 with the dead time L1 acquired at time t3 one cycle before, and the amplitude A3 acquired at time t7 and the amplitude A1 acquired at time t3. Are substantially the same, it is determined that the limit cycle end condition is satisfied (YES in step S107), and the operation amount output means 130 and the PID parameter calculation means 134 are instructed to end the limit cycle.

When the limit cycle is completed, the PID parameter calculation unit 134 calculates the PID parameter using the dead time L1 or L3, the dead time L2, the amplitude A1 or A3, and the amplitude A2 stored in the storage unit 133. Then, this PID parameter is stored in the parameter storage means 12 (step S108). PID parameters include gain, integration time, and differentiation time. This completes the auto tuning.
When the dead times L1 and L3 substantially coincide with each other and the amplitudes A1 and A3 substantially coincide with each other in step S107, either one of the dead times L1 and L3 may be used. Can be used. A method for calculating the PID parameter from the dead time L and the amplitude A is disclosed in, for example, Patent Document 2 described above.

  The dead time L1 and L3 substantially coincide with each other and the amplitudes A1 and A3 substantially coincide with each other means that the control response is stable, and that a reliable measurement result is obtained. is there. That is, even if a limit cycle after time t7 is executed, the same result is obtained, and even if the limit cycle is repeated more than that, only a waste of time is wasted. Therefore, in the present embodiment, when the limit cycle end condition is satisfied at time t7, the limit cycle is ended, and the PID parameter is calculated using the measurement results obtained in the previous limit cycle, thereby performing auto tuning. Can be shortened. Therefore, for example, even when the number of limit cycles of 2.5 cycles or 3 cycles is specified in advance, when the dead time L and the amplitude A with clearly high reproducibility are obtained, the subsequent limit cycles are changed. Auto-tuning can be terminated by omitting it. When the limit cycle is completed at time t7, the auto-tuning can be completed in the shortest two cycles.

  Further, when the slope of the control amount PV acquired at time t6 and the slope of the control amount PV acquired at time t2 one cycle before are substantially coincident, a limit is obtained until the dead time L3 and the amplitude A3 are obtained at time t7. Obviously, the measurement results will be the same without having to continue the cycle. Therefore, when the slope of the control amount PV acquired at time t6 and the slope of the control amount PV acquired at time t2 substantially coincide with each other, the determination unit 132 determines that the limit cycle end condition is satisfied (YES in step S107). The operation amount output means 130 and the PID parameter calculation means 134 are instructed to end the limit cycle. In this case, the PID parameter calculation unit 134 calculates the PID parameter using the dead times L1 and L2 and the amplitudes A1 and A2.

  Thus, in the present embodiment, the time required for auto-tuning can be further shortened by setting the coincidence of the gradients of the control amount PV as the end condition of the limit cycle. When the limit cycle is completed at time t6, the auto-tuning can be completed in 1.5 cycles at the shortest. When 1.5 cycles is specified as the number of limit cycles to be executed from the beginning, the number of cycles will be the same as the result, but with 1.5 cycles, a reproducible measurement result will be obtained. For safety reasons, it is common to specify 2.5 or 3 cycles. If it is clear that a stable measurement result is obtained in 1.5 to 2 cycles when such designation is made, the minimum number of cycles can be achieved without repeating unnecessary limit cycles thereafter. Auto tuning can be terminated.

  In this embodiment, the time required for auto-tuning can be shortened to greatly reduce the adjustment man-hours, and the number of experiments in which the value of the PID parameter is changed in the same time as the time of conventional auto-tuning can be increased. Therefore, the control quality can be improved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. Also in the present embodiment, the overall configuration of the PID control device 1 is the same as that of the first embodiment, and therefore will be described using the reference numerals in FIG. FIG. 5 is a block diagram showing an example of the configuration of the auto-tuning execution means 13, FIG. 6 is a flowchart showing the operation of the PID control device 1 during execution of auto-tuning, and FIG. 7 shows the operation output by the auto-tuning execution means 13 during execution of auto-tuning. It is a wave form diagram showing an example of change of amount of control MV according to amount MV and this amount of operation MV.
The auto-tuning execution means 13 of the present embodiment is obtained by adding an estimation means 135 that estimates the amplitude of the control amount PV to the configuration of the first embodiment.

Next, the operation at the time of auto tuning execution of the PID control device 1 of the present embodiment will be described. The operations in steps S200 to S206 in FIG. 6 are the same as the operations in steps S100 to S106 described in the first embodiment, respectively.
Subsequently, the determination unit 132 determines whether the limit cycle end condition is satisfied (step S207). The limit cycle end condition of the present embodiment is satisfied when the number of limit cycles reaches 1.5. Therefore, in the example of FIG. 7, the limit cycle end condition is satisfied when time t6 is reached.

When the limit cycle end condition is satisfied, the estimation unit 135 calculates the amplitude A3 of the control amount PV that should appear after the time t6 from the slope of the control amount PV acquired at the time t6 and the dead time L1 acquired at the time t3. The estimated amplitude A3 is stored in the storage means 133 (step S208).
In the present embodiment, the amplitude A1 of the control amount PV acquired at time t3 is an uncertain value as to whether it is a value that can be reliably met. On the other hand, the dead time L1 acquired at time t3 is assumed to be a value that is reliable. The reason why the dead time L1 is a reliable value is that if the controlled variable PV is within a controllable range at the start of auto-tuning, the dead time can be measured regardless of the transient state of the controlled variable PV. It is.

  If the dead time L1 can be correctly measured at the time t3, the time required from the time t6 when the manipulated variable MV shifts from on to off to the time t7 when the controlled variable PV reaches the maximum value, as with the dead time L1. The dead time L3 has the same value as the dead time L1. Therefore, it is possible to estimate the amplitude A3 of the controlled variable PV with high accuracy by using the dead time L1 without measuring the dead time L3 and the amplitude A3.

  In order to estimate the amplitude A3 of the control amount PV, a tangent C that contacts the waveform of the control amount PV at the time t6 is calculated from the slope of the control amount PV acquired at time t6, as shown in FIG. At this time, since the increase in the control amount PV should end after the time L1 from the time t6, the point H on the tangent line C when the dead time L1 has elapsed from the time t6 (set value) If the difference from SP) is calculated, it can be seen that a value smaller than the height H is the amplitude A3 of the control amount PV. The amplitude A3 differs depending on the response characteristics of the controlled object, but is generally 80 to 90% of the height H. For example, even if the amplitude A3 is determined as 80% of the height H and calculated, It has been empirically known that there is no problem with this value in determining a practical PID parameter. In this way, the estimation means 135 can estimate the amplitude A3 of the control amount PV.

  After estimating the amplitude A3 by the estimating unit 135, the PID parameter calculating unit 134 calculates the PID parameter using the dead times L1 and L2 and the amplitudes A2 and A3 stored in the storage unit 133, and this PID parameter is used as the parameter. The data is stored in the storage unit 12 (step S209).

The waveform shown in FIG. 7 is a result of actually measuring the control amount PV, but even if a value of 80% of the height H is adopted as the amplitude A3, there is no practical problem in obtaining the PID parameter. I understand. In the case of the example in FIG. 7, if the response characteristic G (s) to be controlled is expressed by the transfer function expression of Expression (1), the range of the control amount PV = 0 to 600 ° C., the set value SP = 300 ° C., When the control target gain G = 2, the control target time constant T1 = 60 seconds, T2 = 2 seconds, and the dead time L = 3 seconds, when the PID parameter is obtained by the conventional auto-tuning function, the proportional band = 57.6. %, Integration time = 29 seconds, differentiation time = 7 seconds.
G (s) = (Ge− ^Ls ) / {(1 + T1s) (1 + T2s)} (1)

  On the other hand, when the PID parameter is obtained by the PID control device 1 of the present embodiment, the proportional band is 55.0%, the integration time is 29 seconds, and the differentiation time is 7 seconds. It was possible to obtain a value without any problems. In the case of such an error, there is no practical difference in the control result by PID.

  As described above, in the present embodiment, the limit cycle is automatically terminated at 1.5 cycles, the amplitude A3 of the control amount PV that should appear at time t7 after 1.5 cycles is estimated, and PID Since the parameter is calculated, the time required for auto tuning can be further shortened. As a result, the number of cycles is the same as when 1.5 cycles is specified as the number of limit cycles to be executed, but the amplitude A1 of the control amount PV obtained in the first cycle is reliable. Since it is not certain whether the value is sufficient, it is common to specify 2.5 or 3 cycles for safety. On the other hand, in the present embodiment, the amplitude A3 is estimated using the dead time L1 that is considered to be a reliable value and the slope of the control amount PV at the time t6. Regardless of whether or not, auto-tuning can be completed with a minimum number of cycles.

  In this embodiment, the time required for auto-tuning can be shortened to greatly reduce the adjustment man-hours, and the number of experiments in which the value of the PID parameter is changed in the same time as the time of conventional auto-tuning can be increased. Therefore, the control quality can be improved.

In the present embodiment, the ratio applied to the height H when estimating the amplitude A3 is set to 80%, but this ratio is appropriately set from 80% depending on the case where the response characteristic of the control target is extreme. It may be possible to change it.
Further, a typical response waveform of the control amount PV is registered in the estimation unit 135 in advance, and the estimation unit 135 searches for a waveform of the control amount PV that matches the slope of the control amount PV at time t6, and from the searched waveform. The amplitude A3 of the control amount PV may be estimated.
Further, when it is determined that the estimation of the amplitude A3 is difficult (for example, when the measurement of the dead time L1 fails due to the influence of noise or the like), the estimation may be given up and the amplitude A3 may be actually measured.

In the first and second embodiments, the progress of auto-tuning may be displayed, and when the PID parameter can be calculated, a display notifying that the PID parameter has been determined may be performed.
In the first and second embodiments, the manipulated variable MV at the start of auto-tuning starts from MVH (on), but from MVL (off) depending on the relationship between the controlled variable PV and the set value SP. Needless to say, it begins.

  The PID control apparatus described in the first and second embodiments 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 first and second embodiments in accordance with a program stored in the storage device.

  The present invention can be applied to a PID control device having an auto-tuning function.

It is a block diagram which shows the structure of the PID control apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the auto tuning execution means of the PID control apparatus of FIG. It is a flowchart which shows the operation | movement at the time of auto-tuning execution of the PID control apparatus of FIG. It is a wave form diagram which shows an example of the change of the control amount according to the operation amount which an auto tuning execution means outputs at the time of auto tuning execution in the 1st Embodiment of this invention, and this operation amount. It is a block diagram which shows the structural example of the auto tuning execution means of the PID control apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of auto-tuning execution of the PID control apparatus which concerns on the 2nd Embodiment of this invention. It is a wave form diagram which shows one example of the operation amount which an auto tuning execution means outputs at the time of auto tuning execution in the 2nd Embodiment of this invention, and the change of the control amount according to this operation amount.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... PID control apparatus, 2 ... Heating furnace, 10 ... Subtraction means, 11 ... PID calculating means, 12 ... Parameter storage means, 13 ... Auto-tuning execution means, 14 ... Switch, 15 ... Manipulation amount conversion means, 16 ... Setting Value storage means, 130 ... operation amount output means, 131 ... acquisition means, 132 ... determination means, 133 ... storage means, 134 ... PID parameter calculation means, 135 ... estimation means.

Claims (4)

A PID control device having an auto-tuning function for generating a limit cycle for repeatedly outputting a manipulated variable having a constant amplitude to a controlled object and calculating a PID parameter based on the response of the controlled object according to the output of the manipulated variable In
An operation amount output means for outputting an operation amount having a constant amplitude to the controlled object when the auto-tuning is executed;
Observe the control amount at the time of execution of the auto-tuning, the dead time which is the time required for the control amount to reach the maximum value or the minimum value from when the manipulated variable changes, and the maximum value or the minimum value An acquisition means for acquiring an amplitude of the control amount that is a difference from a control set value;
When the dead time substantially coincides with the value one cycle before and the amplitude of the control amount acquired simultaneously with the dead time substantially coincides with the value one cycle before, the limit cycle is sent to the manipulated variable output means. Determining means for terminating;
Based on the dead time and amplitude when the manipulated variable changes from on to off and the dead time and amplitude when the manipulated variable changes from off to on when the limit cycle ends, PID parameters A PID control device comprising: PID parameter calculation means for calculating The PID control device according to claim 1,
The acquisition means acquires an inclination of the control amount when the operation amount changes from an initial value when the auto-tuning is performed and when the operation amount changes in the same polarity as the initial change. ,
The determination means causes the manipulated variable output means to end the limit cycle when the slope of the control amount substantially coincides with the value one cycle before. A PID control device having an auto-tuning function for generating a limit cycle for repeatedly outputting a manipulated variable having a constant amplitude to a controlled object and calculating a PID parameter based on the response of the controlled object according to the output of the manipulated variable In
An operation amount output means for outputting an operation amount having a constant amplitude to the controlled object when the auto-tuning is executed;
When the control amount at the time of execution of the auto-tuning is observed, when the operation amount changes from the initial value when the auto-tuning is executed, and when the operation amount changes in the same polarity as at the time of the initial change Slope of the control amount, dead time that is the time required for the control amount to reach the maximum value or minimum value from when the manipulated variable changes, and the difference between the maximum value or minimum value and the control set value Obtaining means for obtaining the amplitude of the control amount;
When the limit cycle reaches a predetermined number of cycles, a determination unit that causes the operation amount output unit to end the limit cycle;
The control amount that should appear after the end from the slope of the control amount acquired at the end of the limit cycle and the dead time when the manipulated variable has the same polarity as that at the end in the past. Estimating means for estimating the amplitude of
When the limit cycle is finished, based on the past dead time and the amplitude of the estimated control amount, and the dead time and amplitude when the manipulated variable has the opposite polarity to that at the end, PID A PID control device comprising PID parameter calculation means for calculating a parameter. In the PID control device according to claim 3,
The estimation means obtains a tangent of the control amount at the end from the slope of the control amount acquired at the end of the limit cycle, and on the tangent when the past dead time has elapsed from the end. A PID control apparatus characterized in that the height of the point is obtained and a value obtained by multiplying the height by a predetermined ratio is set as the amplitude of the control amount to be estimated.

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