JPS60215207A - Pid controller - Google Patents

Abstract

PURPOSE:To prevent erroneous discrimination between ripple oscillation and threshold oscillation by setting a ripple amplitude in case that oscillation in the threshold sensitivity method is detected on a basis of a response speed and a wasteful time which are obtained in the step response method. CONSTITUTION:First, a set value and a set time are written by a key input part 2. When the operation is started, detected temperature data is read into a RAM9 from a temperature detecting part 5 through a control part 6. Next, a manipulated variable M is set to 100%, and a controlled system 4 is controlled to perform a heating operation, and the wasteful time and the response speed are calculated, and a proportional gain in the threshold sensitivity method is calculated on a basis of calculated wasteful time and response speed, and a ripple width which is an allowable width of variation of the oscillation amplitude in the threshold sensitivity is determined. Thereafter, it is checked whether oscillation occurs or not while changing the value of the proportional gain successively little by little, and the threshold oscillation is caused, and a PID constant at this time is stored in the RAM9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a PID control device that temporally controls a controlled object, and in particular to a PID control device that is characterized by tuning of PID constants.
This relates to an ID control device.

BACKGROUND OF THE INVENTION Various control devices, such as temperature control devices, have a control device or a program function to control the temperature to a single set temperature, and control the temperature over time according to a predetermined control pattern. There is a program control unit. These control devices use PID in advance to perform PLD control of the control target.
It is necessary to determine a constant. Furthermore, if the controlled object is different, it is necessary to change the PID constant to suit the object, and a tuning operation is required to determine the constant. As this tuning method, a step response method and a limit sensitivity method (frequency response method) are used.

As shown in Figure 1, the step response method is 100% when the current value, for example, the current temperature, is sufficiently lower than the set temperature s1.
When the controlled object is controlled by the manipulated variable of The PID constant is calculated from the value of RlL according to a predetermined formula. According to this step response method, the PID constant can be obtained in a short time by simply controlling the controlled object with 100% manipulated variable, but in order to increase the response speed R, there is a certain amount of difference between the set value s1 and the current value. There was a problem that a difference between the two was required.

On the other hand, the limit sensitivity method calculates the PID constant from the limit sensitivity Kc, which is the limit proportional gain that oscillates steadily at a set value, and its period Tc in the response curve of the controlled object shown in FIG. According to this method, the PID near the set value s1
It is possible to set a constant, and since the PID constant can be tuned during control, highly accurate tuning is possible.

However, when detecting vibrations, there is a possibility that vibrations different from those of the actual data to be measured may be determined due to detection accuracy of the control device itself, variations in the device, and the like. In addition, the presence or absence of steady oscillation is confirmed by detecting the controlled object with a sensor and based on the data, but it is difficult to detect the oscillation state especially when the oscillation is small, and it takes a long time to obtain the PID constant. There was a problem that it took time.

OBJECTS OF THE INVENTION The present invention has been made in view of the problems encountered when tuning the PID constant of a PID control device. Focusing on the fact that there is a certain correlation between the response speed and dead time obtained from the method and the oscillation amplitude when implementing the limit sensitivity method, determine the oscillation fluctuation range and calculate the accurate PII) constant. The present invention provides a PID control device that can perform

Structure and Effects of the Invention The present invention provides a detection means for detecting measured information in a controlled object, an output means for performing a control operation on the controlled object, and a PID control device for performing PID control on the controlled object based on a set value. step response means for operating the output means and measuring the response speed and dead time from the step response of the controlled object; frequency response means for measuring the limit sensitivity and vibration period from the frequency response of the controlled object; Calculating means for calculating a fluctuation range of the measured information during frequency response determined based on response speed and dead time, and the frequency response means calculates a frequency response based on vibration exceeding the fluctuation range obtained by the calculating means. It is characterized by determining the limit vibration of.

According to the present invention having such features, since there is a certain correlation between the response speed and dead time due to step response and the oscillation amplitude when frequency response method is implemented, data when step response is implemented Based on this, the fluctuation range during frequency response implementation is determined, and vibrations that exceed this range are identified as limit vibrations, thereby detecting the presence or absence of oscillation and its period. Therefore, it is possible to accurately detect vibrations and measure the period without detecting erroneous vibrations due to the detection accuracy of the control device itself or variations thereof.

Therefore, accurate PID constants can be determined, allowing precise control of the controlled object.

DESCRIPTION OF EMBODIMENTS FIG. 3 is an overall configuration diagram of a programmable temperature control device showing an embodiment of the present invention. In this figure, a temperature control device 1 is provided with a key manual section 2 for setting temperature control steps, requesting tuning, etc., a display section 3 for displaying step numbers, set temperatures, and current temperature, and a controlled object 4. A temperature detection unit 5 having a sensor that detects the temperature and an A/D converter that converts the data obtained from the sensor into a digital value.
, a control unit 6 that controls the controlled object 4 according to a predetermined processing procedure based on data obtained from the temperature detection unit 5, and an output unit 7 that is connected to the control unit 6 and directly controls the controlled object 4, which is made up of a heater, a motor, etc. is provided. The control unit 6 consists of a central processing unit (hereinafter referred to as CPU), and is connected to a read-only memory (hereinafter referred to as ROM) 8 and a random access memory (hereinafter referred to as RAM) 9 as storage devices.

The ROM 8 stores the arithmetic processing procedures of the control section 6, and the RAM 9 has an area for storing various control data given from the key manual section 2 and data used during tuning.

FIG. 4 is a memory map showing storage areas used when tuning the RAM 9. In this figure, RAM'9 is provided with an area for storing set values, a measured data area for storing current measured information obtained from the temperature detection section 5,
A step response completion flag that is set when step response tuning is performed on a certain controlled object, a tuning in progress flag that is set during tuning, a detection time area that sets a detection time T for detecting vibration in the limit sensitivity method, A detection timer that counts the detection time, a pull width area that stores the ripple width that is the fluctuation range determined by the step response method, an area that stores the response speed R and dead time obtained by the step response, and a limit sensitivity using the limit sensitivity method. Kc.

It has areas for storing the period Tc, proportional constant KP+integral constant Ki, and differential constant Kd determined by these tuning methods. It is preferable to use a memory banked up by a battery or the like as the storage area used for tuning the RAM 9 so that the data can be stored even after the power is turned off.

FIG. 5 shows the front panel surface of the program temperature control device used in the key input section 2 and display section 3. As shown in FIG. rRUNJ, rATJ, rTIME on the top of the panel surface
J is an operation display lamp, an auto tuning lamp, and a time value display lamp, rBJ is a bank display, and rs
TEPJ is a display section for step display, rPVJ is a display section for displaying current values, and rsVJ is a display section for displaying set values. The rcONTROLJ switch at the bottom is an output operation switch that switches between the normal operation mode and a stop mode that stops time progression and stops control output.
DE" switch is a switch that is selected according to the type of change when setting or changing various program contents, rENDJ
The switch is a switch to cancel the operation and return to the current value display mode, rPROGRAMJ switch is a switch that enables and prohibits program writing, r
The ATJ switch is a switch that is pressed when performing tuning during control, ``↑'' and ``↓.''

``←J, r-J switches increase the parameter values,
It is a numerical control switch that lowers, raises and lowers one digit.
The rWRI TE/NEXTJ switch is a switch that sets display data, stores it in the RAM 9, and moves the setting operation to the next step.

Next, the PID constant calculation operation of the program temperature control device of this embodiment will be explained with reference to a flowchart.

In the flowchart of FIG. 6, numbers indicated using leader lines indicate processing routines or operation steps of the control section 6. First, before tuning, set values and set times are written from the key manual section 2. This is rPROG
After setting the RAMJ key to the cent position and setting the MODEJ key to the program setting, set the value corresponding to the setting step to "↑
”, [↓J, r-J, r-J numerical control switch 7] and write using the rWRITE/NEXTJ key. In the case of a program control device, a series of setting data is written for each control step. Here, it is assumed that each control step and a series of setting values corresponding thereto are written in the step area of the RAM 9 in advance.

Now, when starting the operation in Fig. 6, first step 21
Read the setting value. Then, in step 22, the detected temperature data is read from the temperature detection section 5 into the measured data area of the RAM 9 via the control section 6. Then, the process proceeds to step 23, where it is checked whether the rATJ key is pressed and the tuning flag is set. Since it is necessary to perform tuning when starting control, this flag is automatically set when the power is turned on, so proceed to step 24 and further check whether the step response execution completed flag is set. If this flag is not set, step response has not yet been performed and temperature control is being performed for the first time, so the PID constant of the controlled object is completely unknown.

Therefore, the process proceeds to step 25, where the manipulated variable M is set to 100%, and the controlled object 4 is controlled via the output section 7 to perform a heating operation. Then, the change in temperature data obtained from the controlled object 4 via the temperature detection unit 5 is read, and as shown in FIG. 1, the dead time and the response speed R, which is the maximum slope value of the temperature change, are calculated (step 26). .

Then, in step 27, a step response completion flag is set, and the process proceeds to step 28, where the process waits for the completion of sampling, and then returns to step 21. In this case, since tuning has not yet been completed, the process proceeds to step 24 to check whether step response has already been performed. In this case, since this flag has already been set in step 27, the process proceeds to step 29, and the wasted time lost in step 26 is saved.

A proportional gain is calculated based on the response speed R using the limit sensitivity method. Then, in routine 30, which will be described later, a ripple width, which is the allowable range of oscillation amplitude fluctuation at the limit sensitivity, is determined based on the dead time and the response speed R, and whether or not oscillation occurs is determined by sequentially changing the value of the proportional gain slightly. Check and generate limit vibration. Then, in step 31, the PID constant obtained by the limit vibration is calculated and stored in the RAM 9, and the tuning flag is turned off (step 32). Here, the control equation of the idealized analog PID control device is given by the following equation. .

τ ='KP en +KiΣe1 + K d (e ne +14) −1−−−(1
1 Here, Mn: Manipulated amount + efl” deviation (Ts - Tn
) (T: set temperature, Tn: measured temperature) Kp: proportionality constant, Ki: integral constant, Kd: differential constant, τ
: Sampling period. And the dead time obtained by step response, response speed R,! :P I D has the following relationship with its proportionality constant, integral time, and differential time KP + TI 1 Td.

Ti = 2L Td = 0.5L ---------- (2) Therefore, the proportionality constant Kp can be determined by the step response method, but the PID constant is calculated in more detail by the limit sensitivity method. . In Figure 2, if the proportional band at the limit sensitivity Kc is Pc (%), then Kc and Pc are inversely proportional, and from the proportional band Pc (%) obtained there, the following formula % formula % (31) holds true. , the proportionality constant Kp is expressed by the following formula: K p = A / P ------- (4) (A is a constant determined by the characteristics of the control device).Furthermore, from the oscillation period Tc, Ti -0,5Tc Td = 0. 125Tc −−−−−・− (5) is used to calculate the PID constant using the limit sensitivity method.

The process then proceeds from step 32 to step 28 and waits for the completion of sampling. Predetermined A/D from controlled object 4
The temperature detection unit 5 detects the temperature in the conversion cycle, and when the sampling is completed, steps 28 to 21 are performed.
Return to , read the setpoints and temperature input, and check whether tuning is in progress.

In this case, since tuning has already been completed, the process jumps to step 33 and reads the PID constant held in the RAM 9, and in step 34, the controlled object 4 is PID-controlled and set via the output unit 7 based on the value. Keep at temperature.

FIG. 7 is a flowchart detailing the operation of the limit sensitivity method of routine 30. When entering this routine, first, limit vibration is started using the proportional gain calculated in step 40. Then, in step 41, the response speed R obtained from the step response and the pull width calculated from the dead time are calculated. This means that the proportional band P is R from equations (2) and (3).
, L, but a predetermined width within the proportional band,
For example, a width of 1/10 is determined as a ripple width that is not considered to be a limit vibration and is written in the ripple width area of the RAM 9. Then, the process proceeds to step 42, where the temperature detection section 5 detects the process state, and in step 43, it is checked whether vibration is occurring. If no vibration is occurring, the process proceeds to step 45 and the detection timer is incremented, and even if vibration is occurring, if it is within the ripple width, the process proceeds to step 45 via step 44 and the detection timer is incremented. Then, in step 46, it is checked whether the timer has reached the detection time T. If the timer has not reached the detection time T, the process returns to step 42 and the same process is repeated. If time amplification is performed in step 46, step 47
The process proceeds to step 42, where the proportional gain is changed, and the value of the ripple width corresponding to the gain at that time is determined again (step 48).The process returns to step 42, where the ripple width is newly calculated and the same process is repeated. Now, if vibration exceeding the ripple width is detected in step 44, the loop is exited and the process proceeds to step 49, where the vibration period Tc at that time is measured, the execution of the limit sensitivity method is completed, and the process returns to step 31. . Based on the proportional gain Kc and vibration period Tc at this time, (3
)2 ~ The PID constant can be calculated from equation (5).

In this way, in the present invention, when the step response method is executed for a new controlled object whose PID constant is completely unknown, oscillation is detected using the limit sensitivity method based on the response speed and dead time obtained from the step response method. The process value of the ripple amplitude width is set and used to detect the vibration period. In this way, ripple vibrations will not be mistaken for limit vibrations even for unknown control targets, and vibrations can be detected and appropriate control can be performed quickly.

Although this embodiment describes a program temperature control device, the present invention can be applied not only to this cram school but also to a single setting type PID control device, and the present invention can be applied to various PID control devices other than temperature control devices. It is also possible to do so.

[Brief explanation of the drawing]

Figure 1 is a graph showing the process values that follow the operation when determining the PID constant using the step response method, Figure 2 is a graph showing the relationship between set values and process values using the limit sensitivity method, and Figure 3 is the invention of the present invention. FIG. 4 is a memory map showing the contents of the memory used for tuning operations, and FIG. 5 is a diagram showing the front panel of the setting section 2 and display section 3. , FIG. 6 is a flowchart showing the operation of the program temperature control device according to this embodiment, and FIG. 7 is a flowchart showing the operation when implementing the limit sensitivity method. 1-----1 Temperature control device 2-----Key human power section 3
---------1 display section 4--------1 control object 5
---------1 Temperature detection section 6-----Control section ?
---------One output section 8=-ROM 9-・-RA
M Patent Applicant Tateishi Electric Co., Ltd. Agent Patent Attorney Yoshiki Okamoto (1 person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (3)

[Claims] (1) A PID control device that includes a detection means for detecting measured information in a controlled object, an output means for performing a control operation on the controlled object, and a PID control for the controlled object based on a set value. step response means for operating the output means and measuring response speed and dead time from the step response of the controlled object; frequency response means for measuring the limit sensitivity and vibration period from the frequency response of the controlled object; and frequency response means for measuring the limit sensitivity and vibration period from the frequency response of the controlled object; calculation means for calculating a fluctuation range of the measured information at the time of frequency response determined based on response speed and dead time; PI characterized by determining the limit vibration of frequency response
D control device. (2) The PID according to claim 1, wherein the calculation means calculates a width proportional to the product of the response speed obtained by the step response means and dead time as the fluctuation width. Control device. (3) The PID control device according to claim 1, wherein the PID control device is a program temperature control device.
D control device.