JPS58151603A - Control meter provided with valve characteristic compensation - Google Patents

Abstract

PURPOSE:To linearize an execution flow rate characteristic of a control valve, by using a multiplied value of an output of a generator for generating an inverse function of flow rate gain against an output of a control meter of the control valve, and an output of a reference gain setting devie, as proportional gain of the control meter. CONSTITUTION:An output of a flow rate detector 1 is inputted to an input linearizing circuit 2, and a linearized output PV is inputted to a control meter 3. An output MV of the control meter 3 is inputted to a control valve characteristic compensating circuit 4, in which proportional gain for compensating a nonlinear characteristic of a control valve 5 is outputted to the control meter 3, and one round loop gain containing the control valve 5 is made constant. On the circuit 4, an inverse function generator 11 for generating an inverse function of flow rate gain against the control meter output MV, and a reference gain setting device 12 are provided, and outputs of the generator 11 and the setting device 12 are multiplied by a multiplier 13, and are applied as proportional gain to the control meter 3. In this way, the total gain containing the control meter 3 and the control valve 5 becomes constant against all the operation quantity MV, an execution flow rate characteristic of the control valve 5 is linearized, and the loop gain can be taken greatly, therefore, optimum control of the system can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control side in which a control valve is provided with a valve characteristic compensation circuit to linearize the flow rate characteristics of the control valve.

In a control system including a control valve, it is desirable that the open loop gain of the system be linear and constant over the entire control region. For this reason, while the detection unit linearizes the input, the operating unit does not take active linearization measures other than using an equivalent percentage control valve in consideration of pressure loss in the piping line.

The main cause of hunting in the control system is often due to the nonlinearity of this operating section, especially the nonlinearity of the effective flow rate characteristic of the control valve. The main causes of nonlinearity in the effective flow characteristics of the control valve are as follows.

(1) Since the pressure drop in the piping line is difficult to predict, even if an equivalent percentage control valve is used, the effective flow rate characteristics will not necessarily remain linear.

(2) Due to the rangeability required by the control system, it is not always possible to use an equivalent % control valve (3) Even if the pressure drop in the piping line and the equivalent % control valve are matched, the flow rate is non-linear near the maximum flow rate. Some parts remain.

Cam-type positioners are available to change the effective flow characteristics of control valves, but they have problems with machining accuracy, have complicated mechanisms, are expensive, and can only be attached to specific valves, which limits their usage. It is easy to change the characteristics on-site and tends to cause problems such as leakage.9 It is not necessarily effective for improving the non-linearity of the effective flow characteristics of the control valve.

The present invention has been made in view of these points, and the nonlinearity of the effective flow rate characteristic of the control valve is corrected using an inverse function of the effective flow rate characteristic, thereby improving the effective flow rate characteristic of the control valve. This is a controller with valve characteristic compensation that enables linearization. Hereinafter, the present invention will be described in detail with reference to the drawings.

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

In the figure, 1 is a flow rate detector, and 2 is an input linearization circuit that receives the output of the detector and linearizes the input. Two input linearization circuits may or may not be necessary depending on the type of detector 1. 5 is an adjustment side that receives the output pv of the input linearization circuit. 4 is a control valve characteristic compensation circuit that receives the control n1 output MV and compensates for the nonlinear characteristics of the control valve. The output of the compensation circuit is applied to the regulation side 5. Reference numeral 5 denotes a control valve whose opening degree is adjusted by the output Mv of the controller 3.

In the valve characteristic compensation controller configured in this way,
The compensation circuit 4 receives the adjustment output and sends an output to the controller 3 that compensates for the nonlinearity of the effective flow rate of the control valve as shown in FIG. A linear characteristic is given to the control valve 5. In Figure 2, the horizontal axis is the output MV of controller 3.
The vertical axis shows the flow rate. The circuit shown in FIG. 1 is a flow rate-lift characteristic gain (hereinafter abbreviated as flow rate gain) obtained from the output MV of the controller 3 and the effective flow rate characteristic f of the control valve 5.
By using the inverse function 1/f' of fl to calculate the appropriate proportional gain at that time for the operating output MV that changes from moment to moment, the open loop gain including the control valve 6 is kept constant.

FIG. 3 is an electrical connection diagram showing a specific configuration of the control valve characteristic compensation circuit 5. As shown in FIG. In the figure, the same parts as in FIG. 1 are designated by the same numbers. In the figure, 11 indicates the output MV of the control valve 5, and 11 indicates the effective flow rate characteristic (flow rate gain) of the control valve 5.
This is an inverse function generator that outputs a value 1/f' that has a reciprocal relationship with fl. 12 is a reference gain setter that determines the proportional gain of the system. The setter outputs a reference gain Kpo, and its value can be changed arbitrarily. 13ke,
The output Kpo of the setting device and the output 1/f of the inverse function generator 11
This is a multiplier that multiplies by 1. The output of the multiplier is configured to be the proportional (5) gain of the controller 3.

Now, assume that the reference gain setter 12 is not provided, and consider the case where the inverse function 1/f' of the flow rate gain f1 is selected as the proportional gain of the controller 3. At this time, the total gain G including the controller 3 and the control valve 5 in the case of the "adjustment" output MV is expressed by the following equation.

Therefore, it is always constant for all operations i'Mv.

However, in this case, the total gain including the controller and control valve is always 1, and the optimal control of the specific system (for example, 1
It is not possible to obtain the open loop gain for performing the /4 damping control a1). Therefore, as shown in the figure, the reference gain setter 12
A reference gain value of Kpoik is provided, and the value obtained by multiplying this by the output 1/f1 of the inverse function generator 11, that is, Kp
Let ox (1,/f') be selected as the proportional gain Kp. In this way, the total gain G including the controller and the control valve becomes as shown in the following equation.

(4) Therefore, since it is always constant for all manipulated variables Mv and the loop gain can be made large, it is possible to perform optimal control of a specific system. Note that the reference gain K
The PO can be tuned in the field if necessary. The features of the present invention are listed below.

(1) By linearizing the operating end that has nonlinear elements, it is possible to contribute to stabilization of the control system.

(2) On-site tuning can be easily performed.

(3) It is possible to realize operating end characteristics that match the process characteristics.

(4) The applicable range of the control valve and the operating end can be expanded.

(5) There are no restrictions on how it can be used, and the mechanism is simple and inexpensive.

(6) By separately providing the inverse function generator output 1/f1 for valve characteristic compensation and the reference gain setter output Kpo, valve characteristic compensation and proportional gain operation are independent, allowing on-site controller tuning and valve Characteristics can be easily adjusted. or,
Modifications and changes to the control valve can be easily accommodated.

In the above description, the inverse function generator, the reference gain setter, and the multiplier are constructed using hardware, but they can also be implemented using software using a microcomputer. Further, the inverse function generator 11VC may be approximated using a broken line function. The present invention is not limited to compensation of the characteristics of the control valve described above, but can also be applied to the improvement of the characteristics of other operating devices, or to cases in which nonlinear characteristics are intentionally imparted. Furthermore, the compensation target is not limited to the operating end, but can also be applied to the primary side adjustment of cascade control to give characteristics to the set value of the secondary side adjustment. Furthermore, by using the measured value input to the adjustment word as the compensation circuit input, the measured value input can be linearized using the same principle.

For example, linearization of pI measurement can be achieved.

As described above in detail, according to the present invention, it is possible to linearize the effective flow rate characteristic of the control valve by correcting the nonlinearity of the effective flow rate characteristic of the control valve using an inverse function of the effective flow rate characteristic. It is possible to realize the control valve 1 with valve characteristic compensation, which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a conceptual configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing flow characteristics, and FIG. 3 is an electrical connection diagram showing a specific configuration of a control valve characteristic compensation circuit. 1...Flow rate detector, 2...Input linearization circuit, 3...
- Adjustment puller, 4... Control valve characteristic compensation circuit, 5... Control valve, 11... Inverse function generator, 12... Reference gain setter, 13... Multiplier. (7) Whistle/Kantaku Z Hat Cθ,ノ
(17) (8)

Claims (1)

[Claims] A generator that generates an inverse function of flow rate gain with respect to the controller output of the control valve, and a reference gain setter for determining the proportional gain of the system are provided, and the output of the inverse function generator and the output of the reference gain setter are provided. A controller with valve characteristic compensation configured so that the multiplied value of is used as the proportional gain of the controller.