JPS6324301A - Process control device - Google Patents

Abstract

PURPOSE:To easily execute an optimum mode control even at the time of changing a desired value, by executing a control operation, based on a deviation of the desired value and a controlled variable by a control operation part in accordance with a set transfer function, and also, providing a desired value input filter which can set freely a necessary time constant. CONSTITUTION:A deviation of a desired value and a controlled variable, which passes through a desired value input part filter 11 is operated by a deviation computing element 12, and based on this deviation value, a control operation part 14 executes a control operation and calculates a manipulated variable for operating a control object process 13 for allowing the controlled variable to coincide with the desired value. A result of this calculation and a disturbance are supplied through an input terminal 15 and the controlled variable is outputted from the process 13. To these operation part 14 and filter part 11, respectively, a necessary transfer function and a necessary delay time constant calculated by a parameter operation part 17 with respect to setting of a response waveform time constant setting part 16 corresponding to a disturbance and a target change are supplied, and an optimum mode control can be executed by an easy setting operation, not only against the disturbance but also even at the time of changing the desired value.

Description

[Detailed Description of the Invention] [Object of the Invention] (First industrial field) The present invention provides a process control device (system) suitable for process control, particularly for controlling a controlled object including dead time characteristics. Regarding.

(Prior art) In conventional process control, if there is a long dead time with respect to the delay time constant of the process, the feedback control system using the normal P I Did moderator as shown in Fig. 2 cannot control the process. It becomes difficult. For this reason, Smith's control system (1) is equipped with a minor loop around the main controller that has a model that simulates the process dynamic characteristics.
(Fig. 3) or a control device having the control calculation characteristics shown in Fig. 3 may be used.

However, the symbol in these figures is the following υ.

Gpe-LPS: Transfer function Gp representing the dynamic characteristics of the controlled process: Process transfer function Lp excluding dead time:
Process dead time S: Laplace operator Go: Transfer function Gcs that represents the characteristics of the control calculation section
Transfer function G of the principal density meter in Smith's ftjli controller, i%f: Transfer function of the model simulating the process characteristic Gp, +'vI: 7' Simulated value of process dead time Gck' 4th Transfer function of the main controller of the controller shown in the figure However, when using these control devices, if control parameters are determined with focus on controllability against target value changes, controllability against disturbances will deteriorate (recovery may be slow). 1.-
．． ).

On the other hand, if control parameters are determined with attention to controllability against disturbances, controllability deteriorates when the target value is changed (overshooting occurs and vibrations tend to occur).

For this reason, conventional measures are being taken.

(1) Determine control parameters by focusing on either target value change or disturbance, and ignore deterioration of controllability in the other case.

(2) By using a value intermediate between the optimal parameter value when changing the target value and the optimal parameter value for disturbance, it is not optimal for either changing the target value or for disturbance, but it achieves controllability that is a compromise between the two. .

(3) Normally, control parameters are set so that optimal control can be obtained against disturbances, and when it becomes necessary to change the target value, the target value is changed by resetting the parameters to the optimal parameters for target value change control. I do. After the process has settled to the new target value, the control parameter values for disturbance control are returned again.

In this case, there are disadvantages in that the operation requires manpower, operation errors are likely to occur, and it is not possible to deal with disturbances when changing the target value.

(4) It is equipped with two types of control calculation units, one for target value change control and one for disturbance control, or is equipped with two types of control parameter sets, and is always controlled in disturbance control mode,
A controller is used that automatically switches to a calculation section for target value change control when detecting the occurrence of a change in target value, and switches to a calculation section for disturbance control when it is determined that the process has settled to a new target value. In this case, two types of arithmetic control units are required, and the bumpless switching between them and the automatic determination mechanism for the target value change control period are complicated and expensive. As in item (3) above, there is a drawback that it cannot be dealt with when disturbances are added during target value change control.

Furthermore, when PIDID adjustment is used in a normal control system as shown in FIG. 2, it is known how to determine and adjust the values of the control parameters (proportional gain; integral time; differential time). However, when a PID controller is used as the main controller for the Smith controller in Figure 3, the desirable values of the control parameters are different from those in the system in Figure 2, and the relationship between the parameter values and the response waveform of the control system is different from that of the system in Figure 2. Physical correspondence is no longer clear,
The situation was extremely difficult to adjust parameters.

It is an object of the present invention to eliminate the drawbacks of the prior art described above, and to control a controlled object including dead time in a ride-through mode even when the target value is changed or when the target value is kept constant and controlled against disturbances. We are planning to obtain a process control device (system).

In addition, by simply setting the time constant of the waveform, which defines the control response waveform due to target value changes and disturbances, as an adjustment parameter, the control parameter automatically controls the controlled variable response waveform of the controlled process to the desired shape. The objective is to obtain a process control device (system) that is easy to set up and adjust.

[Structure of the invention]

In order to achieve the above object, the present invention provides a deviation calculation means for calculating a deviation between a controlled variable obtained from a controlled object including dead time characteristics and its target value, and a response of the controlled variable to a disturbance to achieve a desired damping characteristic. control calculation means for calculating a manipulated variable for making the control amount match the target value by performing a control calculation for the deviation based on a transfer function set to make the change in the target value; and target value input filter means, in which a delay time constant of a transfer function having at least -order lag characteristics is set so that the response of the controlled variable has an exponential rise characteristic including the dead time. It is something.

(Function) With the above configuration, the present invention can make the response of the controlled variable to a desired damping characteristic based on the transfer function of the control calculation means to fluctuations in disturbance, and can also respond to changes in the target value. However, the response of the controlled variable can be made to have an exponential rise characteristic including a desired dead time based on the transfer function of the target value input filter means.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual block diagram of an embodiment of the present invention.

11 is a target value input section filter for inputting a target value signal;
2 is a deviation calculation circuit that compares the output of the target value input section filter with the control amount of the target process 13 and outputs a deviation; 14 is a circuit that operates the controlled process to make the controller match the target value from the deviation signal; 15 is an operating terminal that inputs disturbance and operation amount to operate the controlled process, and calculates the target value signal of the controller consisting of a deviation calculation circuit and a control calculation section. This is a control device (system) having a configuration in which a target value input section filter 11 with a transfer function G is added to the input section.

Here, the target value input section filter 11 has a transfer function such as 1+TF3S1+TF2S, and is realized by an analog circuit or digital calculation.

That is, in a control system using this control device (system), the transmission relationship of the control amount with respect to disturbance is as follows. When controlling against disturbance with a constant target value, the target value input section filter 11 is dynamically is not involved in any control. For this reason, the transfer function G that defines the configuration and characteristics of the control calculation section 14 is
c can be arbitrarily determined so as to achieve optimal control against disturbances.

Next, when Gc is determined as described above, the transfer function of the control amount to be applied to change the target value is as follows. Therefore, the target value input section filter 11 is designed so that its characteristics (transfer function OF) optimize the response of this control system when changing the target value.

As a result, this controller! The (system) operates in the optimal control mode even when changing the target value.

Furthermore, to facilitate the parameter setting of the control calculation section 14 and the target value input section filter 11, as shown in FIG. 5, analog setting devices such as potentiometers, pulse generators; digital switches; keyboard: typewriter ;
Digital setting device such as GRT light pen. Alternatively, when signals corresponding to time constants are sent from an external host control device, etc., the response waveform time constant setting section 16 of a retainer, etc. that holds those signals and the control calculation are performed from the set time constants. A parameter calculation conversion section 17 is provided to convert the control parameters of the section 14 (e.g., proportional gain; integral time; differential time) and the filter time constant of the target value input section filter 11, and fully defines the response waveform to a target value change or disturbance. As long as the time constant is set, the parameters of the arithmetic control section 14 and the target value input section filter 11 are automatically adjusted.

Furthermore, if the process dynamic characteristics fluctuate and you want to automatically deal with these fluctuations, the configuration shown in Figure 6 can also be adopted. In this case, the process dynamic characteristic identification unit 18
A process dynamic characteristic identification calculation is performed by inputting the state quantities of the process and the control device output.

The resulting process parameters (process gain process delay time constant; dead time, etc.) are received by the parameter calculation conversion unit 17 and control calculation unit 14, and the internal process model parameters are automatically converted into the state of the actual process. It is now possible to match the

The construction of the device of the present application having such a circuit configuration will be described in detail with reference to the drawings.

Assume that the dynamic characteristics of the controlled process are "first order delay + dead time", that is, the transfer function can be approximated by the formula c3) or this form.

Here, KP is a process gain, TP is a process delay time constant, and LP is a process dead time. (S nira plus operator) This controlled object is controlled by a controller such as the Smith controller type controller GC in FIG. 3, and this main controller section (Gas)
If a PID controller or PID calculation unit with the transfer function shown in equation (4) is adopted, its control parameters are calculated using the following equation (TD will be described later), and if the PID calculation characteristics are Then, when a step disturbance is added to the process, the controlled variable response waveform becomes as shown in FIG.

In FIG. 7, the feedback control system cannot control the period when time t<2LP due to process dead time, and the control amount response waveform during this period is uniquely determined by the process characteristics. Therefore, [>Determine the desired exponential function waveform of the waveform after 2LP, substitute the time constant TD that defines that waveform into equation (5) or (7), and calculate the PI
If all D parameter values are calculated and set to these values, and a controller using a PID controller with the configuration shown in Figure 3 is used, the transfer function of the controlled variable to the disturbance is Txz=(1-e '') Tp+e+・Tn−・・−・−
(9) T, P, and a response waveform with a damping characteristic as shown in FIG. 7 is realized in response to a step-like disturbance. In addition, GPM (1-e LP
M8) is a process model calculation unit having characteristics obtained by subtracting process characteristics from process characteristics excluding dead time.

That is, this control device (system) controls the controlled object against the disturbance in a response waveform mode designated as the most desirable even against a step-like disturbance.

In addition, when using the controller of the third figure instead of the controller of the second figure, 1 is used as the main control calculation section (()c K ).
It is sufficient to use a filter having next-order filter characteristics. In addition, 1/()PM is a process characteristic and is the inverse characteristic of the characteristic excluding dead time? In this case, it is the next calculation unit that has this characteristic sound. Also e-L
PMS is a simulator of process dead time characteristics, and it is assumed that LPM=Lp.

In this way, the controller 1jI shown in FIG. What has been described in the case where the controller 2 shown in the figure is incorporated also applies to '1'.

Above, we have described two types of controllers to be incorporated into this control device (system), as shown in Figures 3 and 4. However, the controller is not limited to these types, and can realize a specified response waveform in response to a disturbance. Any controller or calculation algorithm with control characteristics may be used.

Next, the case of changing the target value will be explained.

As the control arithmetic unit (Gc), all those configured to be optimal against the above-mentioned disturbances are used.

Further, as the target value input section filter 11, the following one having the characteristic of the following formula is used.5 (Tn: will be described later) In this case, the transfer function of the controlled variable with respect to the target value change of the control system in FIG. 1 is as follows. That is, with respect to the target value change, the delay time constant T and the dead time Lp have a "first-order delay+dead time" rise characteristic. FIG. 8 shows the response waveform of the control amount to the scoop-like change in the target value.

Therefore, the desired shape of this response waveform is determined, and the time constant T that defines this waveform is set as the value of the filter time constant T22 of the target value input section filter. As a result, the control device (system) controls the controlled object at the time of the change in the target value in the response waveform mode specified as the most desirable for the step change in the target value, and causes the process to settle to the new target value. In this case, the control characteristics of this control system against disturbances remain in equation (8) and are not affected by the target value input section filter, so the control characteristics can be maintained at the optimal control state even against disturbances. There is.

In addition, if the time constant TD that defines the response waveform to a step-like disturbance and the time constant T that defines the response waveform to the step-like change of the target casing are both specified as the same value, the target value input section filter is used. may be a first-order filter with the following characteristics.

(Tyl is given by 0 → formula) Furthermore, in order to make the controlled variable rise smoothly when changing the target value, or to shorten the settling time, it is necessary to If it is desired to specify a response waveform with "dead time" characteristics, a filter with characteristics as a target value long filter is used. Here, TR and A,
is a time constant that completely defines the response waveform, and TFI and TF3 are given by the equation 0→.

Next, the parameter settings of this control device (system) will be described.

When using this control device t (system), if the characteristics of the controlled object are constant, the parameters determined and adjusted by the operator are TD and TR (or TR
There are two types (3 types): and AR). this! (5)
; (7) ; (9) ; tll) ; Q4)
By substituting into the formula etc., KS of the control calculation section, T112.
It is sufficient to calculate T0n or 'rK1°TK2 and the filter constant TFI of the target value input section filter, and set these values in the parameter adjustment section or recording section within the control device (system).

Also, if the values of TD and TR (or T, and AR) are set with the response waveform time constant setter 16, (5);σ);
9) The next Harameter calculation converter 17, which has calculation characteristics such as ;uv;04 formula, automatically converts KS+T31+Tl
Calculate 1D+ TK 1+ TJC2JTF1 etc.,
Automatically set at a predetermined location within the control device. Therefore, manual calculation of parameters can be omitted.

However, when the process dynamic characteristics change, the parameter calculation conversion section converts xP, TP+ from the process characteristic identification section.
After receiving the value of Lp, (5), (7), (9)
, uv, update the values of Kp, Tp, Lp of 04 formula and 81 T8!4 TlID, TKI.

Calculate all values such as TK 2 + 'r, 3, etc.

[Effect of invention answer]

As described above, the present invention inserts a simple filter into the target value input section and determines and sets the parameters of the control device (system) using the above-mentioned method. The controller fl! also controls in the optimal control response waveform mode specified. (system) was realized.

In addition, in such control systems, each parameter of the controller can be uniquely and automatically adjusted as long as a clear time constant of the desired response waveform is determined and set. We have created a control device (system) that reduces the burden on operators who make decisions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the process control device of the present invention, FIG. 2 is a block diagram of a conventional process control device, and FIGS. 3 and 4 are used in the process control device. FIGS. 5 and 6 are diagrams showing other embodiments of the present invention in a block configuration, and FIGS. 7 and 8 are detailed explanations of the present invention. This is the ninth diagram. 1... Target value input section filter, 12... Deviation computing section, 13... Controlled process, 14... Control computing section, 16... Response waveform time constant setting section, 17... Parameter calculation conversion section. Agent Patent Attorney Nori Ken Chika Yudo Yamashita - Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] Based on a deviation calculating means for calculating a deviation between a controlled variable obtained from a controlled object including dead time characteristics and its target value, and a transfer function set so that the response of the controlled variable to a disturbance has a desired damping characteristic, control calculation means for calculating a manipulated variable that makes the controlled variable match the target value by performing a control calculation on the deviation; and target value input filter means in which a delay time constant of a transfer function having at least first-order lag characteristics is set so as to have an exponential rise characteristic.