JPH0231403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection circuit for a process control device that controls a controlled object whose state changes slowly.

Conventionally, the method of inspecting this type of equipment is to have a skilled worker start the inspection as soon as he/she confirms that the controlled object is stable. It was necessary to supply an alternative process signal in an appropriate manner so as not to cause

In this way, conventional technology is not easy to inspect;
The drawback was that even if new changes occurred in the controlled object during inspection, it was not possible to respond quickly.

This invention was made in order to solve the conventional problems as described above, and it is possible to easily start an inspection, and also to immediately stop the inspection when a change of more than a predetermined value occurs in the process signal during the inspection. It is an object of the present invention to provide a process control inspection circuit that enables bumpless switching when returning to normal operation from inspection.

An embodiment of the present invention will be described below with reference to the drawings. In the figure, a controller 1 is a process control device and is an object to be inspected. The process signal PCI, which is an input to the controller 1, is first supplied to the circuit 2. The circuit 2 has a function of sampling and storing the process signal PCI at an appropriate sampling period, and a function of calculating the difference between the previously stored contents and the current contents of the process signal PCI, and checking that the difference is less than a predetermined value. It is automatically confirmed, and when the start signal TST that commands the start of inspection is input, the inspection permission signal 2a is output, and when this inspection permission signal 2a is not output, the process signal PCI is passed. It has a function of sequentially outputting the internally stored contents when returning to normal operation from the time of inspection, and then passing a process signal. When the inspection permission signal 2a is input to the switching circuit 3 of the switching device constituted by the switching circuit 3 and the switching devices 4-1, 4-2, and 4-3, the switching circuit 3 switches between the switching devices 4-1, 4-2, and 4-3. 4-
It outputs a signal 3a that actually operates 2 and 4-3.

The switch 4-1 outputs the process signal PCI that has passed through the circuit 2 or the inspection signal 5a from the inspection signal generator 5.
is selectively supplied to the controller 1. The control signal 1a output from the controller 1 is transmitted to the switch 4
-2 to the storage circuit 6. Further, the signal 6a of the memory circuit 6 and the control signal 1a of the controller 1 are transmitted to the switching circuit 3 by the output command 3a of the switching circuit 3.
-3 is selected and becomes the process output.

The memory circuit 6 is a circuit that samples the control signal 1a at a predetermined sampling period and stores it while updating it. When the switch 4-2 is closed, it always samples new input and updates it with the stored content.
When the switch 4-2 is opened, the signal 6a is output without updating the stored contents.

During operation, during non-inspection, that is, during normal operation, the switching devices 4-1, 4-2, and 4-3 are in the positions shown in the figure.
Since the start signal TST is not input, the controller 1 receives the process signal via the circuit 2.
The PCI is input, control calculations are performed based on the PCI, and the control signal 1a is output to the process via the switch 4-3.

On the other hand, during inspection, first the start signal TST is set to circuit 2.
is supplied to And circuit 2 is a process signal
When the PCI shows only a change less than a predetermined value, that is, when the process control system is stable, the inspection permission signal 2a is output, the switching circuit 3 outputs the signal 3a, and the switching circuit 4-1, 4- 2, 4-3 in the opposite position as shown.

As a result, the inspection signal 5a of the inspection signal generator 5
is input to the controller 1 via the switch 4-1, and the memory circuit 6 stores a signal 6 consisting of the control signal 1a at the time when the switch 4-2 is opened.
a is output via the switch 4-3.

During such inspections, the process signal PCI
When this changes, the circuit 2 no longer outputs the inspection permission signal 2a, so the switching circuit 3 also no longer outputs the signal 3a, returning the switches 4-1, 4-2, and 4-3 to the illustrated positions. That is, the inspection of the controller 1 is canceled and the controller 1 operates normally.

Further, when returning to normal operation from the time of inspection, the contents stored in the circuit are sequentially outputted, and then the process signal is passed.

As described above, according to the present invention, the inspection is started or continued only when a start signal instructing the start of the inspection is supplied and it is automatically confirmed that the change in the process signal is less than or equal to a predetermined value. In addition, the process control signal that was being supplied to the process equipment at the start of the inspection is memorized and continuously output during the inspection, and the process control signal is checked in series with the process input signal to determine if there is a transient change in the process signal. Since the configuration includes a circuit that detects whether the process control system is stable or not, it is easy to check and confirm that the process control system is stable, and if the process control system becomes unstable, the process control system can be immediately The control device can be returned to normal operation, and when returning to normal operation from the time of inspection, bumpless switching is achieved by sequentially outputting the contents stored in the circuit and then passing the process signal. This has the effect of making it possible to

[Brief explanation of drawings]

FIG. 1 is a block diagram of a process control inspection circuit according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Controller, 2... Circuit, 2a... Inspection permission signal, 3... Switching circuit, 5... Inspection signal generator, 6... Memory circuit.

Claims (1)

[Claims] 1. In a process control inspection circuit that inspects a process control device that performs predetermined processing according to an input process signal and outputs a process control signal, normally the input process signal is passed through and output, and the process signal is It is sampled at sampling intervals and stored sequentially, and during inspection,
a circuit that outputs an inspection permission signal when the difference between the previous stored content and the current process signal is less than a predetermined value and a start signal is input; a switching circuit that operates according to the inspection permission signal output from this circuit; An inspection signal generator that outputs an inspection signal for inspecting the process control device; under normal conditions, it selects the process signal output from the circuit, switches it by the operation of the switching circuit, and outputs it from the inspection signal generator. A first switching device that selects an inspection signal and supplies it to the process control device, which normally stores and updates the output of the process control device, and holds and outputs the stored value through the operation of the switching circuit. The memory circuit normally selects the output of the process control device,
A second switch is provided which is switched by the operation of the switching circuit to select and output the output of the storage circuit, and when returning to normal operation from the operation of the switching circuit, the contents stored in the circuit are A process control inspection circuit characterized in that a process signal is output after being sequentially output to the process control device.