JPS6111803A - Process control device - Google Patents

Abstract

PURPOSE:To prevent an apparatus to be controlled from damage at the sudden change of control status by arranging output signal grade limiting blocks between a control operation block and pumps. CONSTITUTION:A process control device controls a flow rate and the control operation block 3 calculates a control output signal R for a deviation (e) between an objective value P and a flow rate signal Q outputted from a flow rate detector 1 and sends the signal R to the output signal grade limiting blocks 4. The limitation blocks 4 output 0% control output signals R1-Rn for driving motors for the pumps 2 at the stop of the pumps 2 or outputs control output signals R1-Rn corresponding to the difference between bumpless signals U1-Un and the control output signal R outputted from the block 3 at the time of operating status. Consequently, the pumps 2 are prevented from sudden change to rapid operation or the like due to the increase of the deviation (e) at a transient time such as the start of the pump and the change of the objective value and the motors or the like can be prevented from damage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a process control device that performs analog control of a plurality of devices to be controlled using a single analog feedback signal.

Configuration of conventional example and its problems For example, a conventional process control device that performs flow rate control is
As shown in the figure, a target value P and a plurality of pumps 2-1, 2-2. ..., the adjustment calculation program 3 calculates the equation (1) based on the deviation e from the flow rate signal Q from the flow rate detector 1 which detects the flow rate sent by 2-n. A control output signal R is obtained, and this control output signal R is transmitted to a plurality of pumps 2-1.2-2. ...
, 2-n drive motors.

However, PB biproportional band T□: Integral time TD; Differential time The open loop transfer function G (S) of the above process control device is as shown in equation (2).

In such a process control device, the stopped pumps 2-1, 2-2. ..., 2-n, the calculation results of the adjustment calculation block 3 are output as they are, and the pumps 2-1, 2-2, . ....

2-n, the drive motor would be operated at high speed at the same time as the drive motor, and there was a risk that the drive motor would be in an overtorque state and be damaged.

OBJECTS OF THE INVENTION An object of the present invention is to provide a process control device that can completely prevent damage to a controlled device when the control state of the controlled device suddenly changes.

Structure of the Invention As shown in FIG. 1, the process control device of the present invention includes:
an adjustment calculation block (3) that calculates and outputs a control output signal by performing a predetermined calculation on the deviation (e) between the target value (P) and the detection signal (Q) from the detector (1); When the difference between the value of the control output signal (R) of this adjustment calculation block (3) and the value of its previous output signal (R1) is less than the allowable maximum gradient value, the adjustment calculation block (3) The control output signal (R) is given to the controlled device (2-1) as its own current output signal (R1), and the value of the control output signal (R) of the adjustment calculation block (3) and its previous output are When the difference with the value of the signal (R1) exceeds the allowable maximum slope value, the current output signal (R1) is the value of the previous output signal (R1) plus the maximum allowable slope value. and an output signal gradient restriction block (t-1) which is applied to the controlled device (2-1).

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 2 to 4. This process control device d performs flow/volume control, and as shown in FIG.
The control output signal R is obtained by calculating the formula (11), and this is applied to the output signal gradient limiting block 4-1.4-2.
．． ..., 4 is set so that it is sent to 4-n. .

The output signal gradient restriction block 4-1 outputs a 0% signal as the control output signal R1 when the pump 2-1 connected to the main station is in a stopped state, and when the pump 2-1 is in an operating state. When, bunchless signal (previous control output signal)
A control output signal R1 is output as shown in equation (3) according to the difference between Ul and the control output signal R from the adjustment calculation block 3, and is applied to the drive motor of the pump 2-1. .

IZs-Zk' When 1≦ΔZ, Zk=ZsZs-Zk
'<ΔZ then Zk=Zk'-ΔZZs-Zk'>ΔZ
When Zk=Zk'+ΔZ...(3) Where, Zk': Value of bumpless signal U1 Zs:g
The value of the control output signal R of the four-node calculation block 3 is 2 to 2 The value of the control output signal R1 ΔZ DO): Maximum permissible slope In this way, the output signal slope limiting block is placed between the adjustment calculation block 3 and the pump 2-1. Pump 2- by providing 4-1
Since the slope of the control output signal R1 applied to the pump 2-1 is limited to a predetermined value or less, the deviation e between the target value P and the flow rate signal Q is Even if the pump 2-1 becomes extremely large, it is possible to prevent the pump 2-1 from suddenly starting high-speed operation or suddenly stopping its operation, thereby preventing the pump 2-1 or the motor that drives it from being damaged.

Here, the effect of slope restriction will be explained in more detail.

There are two effects of gradient restriction: (1) and (2) below.

■Overtorque protection for pumps that have started operating: If a high-speed rotation command (analog signal) is suddenly given to a pump that has started operating, the starting torque will exceed the required starting torque, resulting in an overtorque condition. Therefore, even if the motor is to be rotated at a high speed, a signal with a slope limit that gently increases the rotational speed is provided to prevent an overtorque state of the motor.

■ Stabilization of the rotational speed of a pump that is already in operation: When a pump that has been started is rapidly rotated, the flow rate increases and the flow rate signal Q rapidly increases. As a result, the output signal of the adjustment calculation block 3 suddenly decreases, and a signal that sharply reduces the rotational speed of the pump, which was already operating at a stable speed, is output, causing the control system as a whole to It may become unstable and the pump speed may oscillate up and down until a new stable speed is reached. This problem can be solved by reducing the rate of change of the flow rate signal Q, that is, by gradually changing the rotational speed of the started pump.

FIG. 3 shows the limit output signal R (indicated by a broken line) from the control block 3 before and after starting the pump 2-1, and the corresponding output signal R, and the control output signal from the block 4-1 on the gradient side 7. R1 (indicated by a solid line). Third
In the figure, the control output signal R corresponds to the target value P, and a high level value is outputted as shown by the broken line, and at time t. When the pump 2-1 is started, in the conventional case, a high-level control output signal R is suddenly applied to the motor that drives the pump 2-1, so there is a risk that the motor will be overtorqued and damaged. However, in this embodiment, since the gradient-limited control output signal R1 is applied to the motor, the torque of the motor gradually increases, and damage to the motor can be prevented. Then, as time passes, the level of the control output signal R1 increases at a constant slope, and when it reaches almost the same level as the control output signal R at time t1, the fluctuation of the control output signal R itself is smaller than the limit slope, It is the same as without the output signal slope limiting block 4-1, and normal control operation is performed without changing the transfer function of the feedback control loop and without adversely affecting its control characteristics.

In addition, other output signal slope restriction blocks 4-2,...
, 4 to n are also the same as above, and output the control output signals R2 to Ro and bumpless signals U2 to U, and have the same effect.

On the other hand, in the parameter change calculation block 5, for example, the
1) Proportional band P8 in the formula is p, = NXP8o (4) where N: Proportional band P calculated with the actual number of pumps in operation PBO' constant and given to the adjustment calculation block 3.

is automatically corrected according to the number of operating vehicles N. in this way,
If the value of the proportional band P8 is corrected according to the number of operating units N, even if the transfer function of the controlled device changes depending on the number of operating units N, the open loop transfer function of the entire control system becomes G (S), and the number of operating units N becomes It does not fluctuate even when the flow rate changes, and the flow rate can always be stably adjusted and controlled.

FIG. 4C is a flowchart showing the operation of the process control device described above. The following explanation will be based on this.

Step A1: Input the number N of operating vehicles, the value Zk' of the previous control output signal (Humpless signal), and a constant.

Step A2: Calculate equation (4).

Step A3: Perform the proportional-integral-differential calculation of equation (11).

Step A, : is set to =1.

Chip A5: Determines whether or not the th device to be controlled is currently in operation.

Step A6: When the determination result in step A5 is NO, the current control output signal value ZK is set to Zk=0.

Step A7: When the determination result in step A5 is YES, the value Zs of the control output signal and the value Zk' of the bumpless signal are
It is determined whether lZk'-Zsl≦42.

When the determination result in step A8 and step A7 is YES, the value Zk of the current control output signal is set to Zk'=Zs.

Step A9 When the determination result in step A7 is NO, the value Z's of the control output signal and the value Zk of the bumpless signal are compared to determine whether Zk' - Zs>ΔZ'.

When the determination result of step AIO'step A9'' is YES, set the value Z'k of the current control output signal to Zk=Zk
' −ΔZ.

The determination result in step A12 and step A9 is N.

When , the value Zk of the current control output signal is Zk=Zk'
+ΔZ.

Step A12 Step A6, When any of 'Al09All' is completed, check whether the calculations for all the controlled devices have been completed, that is, whether -M (M is the total number of controlled devices) has been completed. judge.

Step A13 The profit result of step AI2 is N.

When , the value is set to +1 and the process returns to step A5.

When the determination result in step A14 is YES, the value Zk of the control output signal as the calculation result is output, and the process returns to step All.

Note that this invention can be used when controlling the rotation speed of a blower, etc.
Applicable to various controlled devices.

Effects of the Invention According to the process control device of the present invention, it is possible to prevent destruction of the controlled equipment when the control state of the controlled equipment suddenly changes.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a functional block diagram of a process control device according to an embodiment of the present invention, and FIG. 3 is an explanatory diagram showing temporal changes in control output signals.
Figure 4 is a flow chart for explaining the operation, Figure 5 is a flow chart for explaining the operation.
The figure is a block diagram of a conventional example. l...Flow rate detector, 2-1 to 2-n...Pump (control target device), 3...Adjustment calculation block, 4-1 to 4
-n...Output signal slope restriction block, Fig. 1

Claims (1)

[Claims] An adjustment calculation block calculates and outputs a control output signal by performing a predetermined calculation on the deviation between the target value and the detection signal from the detector. When the difference between the output signal value and the value is less than or equal to the allowable maximum gradient value, the control output signal of the adjustment calculation block is given to the controlled device as its own current output signal, and the control output signal of the adjustment calculation block and its previous output signal are an output signal that, when the difference between the output signal of A process control device comprising a slope limit block.