JPH07110652A - Noise elimination method for input / output device of programmable controller - Google Patents

Abstract

(57) [Abstract] [Purpose] To simplify the noise elimination circuit of the input / output device of the programmable controller. [Arrangement] Adder 2 performs averaging processing and moving average processing on a digital input signal after analog / digital conversion.
1, the divider 22 and the MPU 5 are used to remove noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise elimination method for an input / output device of a programmable controller, and more particularly to a digital / digital signal input / output to / from a device to be controlled.
The present invention relates to a noise elimination method for an input / output device of a programmable controller that performs mutual conversion into analog.

[0002]

2. Description of the Related Art Conventionally, a programmable controller is known as a device for automatically controlling electronic devices.
The programmable controller inputs an input signal indicating the operating state of the contacts in the electronic device to be controlled,
Based on this input signal, a new operation content of the contact is determined. An output signal is output from the programmable controller to transmit the determined operation content to the electronic device to be controlled. In the programmable controller, a digital signal at the control signal level is usually handled, and an analog signal is handled on the controlled device side. Therefore, an input / output unit that performs analog / digital conversion is installed between the programmable controller body and the control target device.

FIG. 9 shows a typical system configuration of the input signal processing system of the input / output unit. A programmable controller body 1, an input / output interface (I / O) 2 and an input / output unit 12 are connected via a bus 3 in the programmable controller. The programmable controller main body 1 performs a sequence operation based on an input signal to determine an output signal. The programmable controller body 1 has a CPU, and the CPU performs transfer processing of input signals and output signals with the input / output unit 12. The I / O 2 is connected to a programming device and inputs a program for sequence operation from the programming device. In the input / output unit 12, the bus interface 4 is connected to the bus 3, and a plurality of output signals output from the CPU of the programmable controller body 1 to the bus 3 for output are output via the bus interface 4 to the MPU.
5 is transferred. The MPU 5 collectively receives the output signals from the programmable controller main body 1, temporarily stores them in the RAM 7, and then outputs them to the control target device via an analog / digital conversion circuit (not shown).

On the other hand, input signals at a plurality of points sent from the controlled equipment side are input to the operational amplifier 11, respectively. A noise filter 10 removes noise from the input signal shaped into a high / low signal having a constant voltage by the operational amplifier 11. After this, the noise-removed input signals sequentially selected by the multiplexer 9 are analog / digital (A /
D) Converted into a digital signal by the converter 8, and MPU5
Is temporarily stored in the RAM 7 via the. After this, MPU5
Synchronizes with the operation on the programmable main body 1 side and transfers the input signal of the RAM 7 to the programmable controller main body 1 via the bus interface 4 (see FIG. 10). The above operation control is realized by the MPU 5 executing the processing procedure stored in the ROM 6.

[0005]

Conventionally, this type of system requires an expensive noise elimination filter having good frequency characteristics as many as the number of input signals (the number of channels).
This has had an influence on the size increase and cost reduction of the input / output unit 12.

In view of the above points, an object of the present invention is to provide an input / output device of a programmable controller that has a noise removing effect equivalent to that of a noise filter and can contribute to downsizing and cost reduction of the device. To provide a method of removing noise.

[0007]

In order to achieve such an object, the present invention eliminates noise in an input / output device and performs analog / digital conversion on an analog input signal sent from a device to be controlled. In the method of removing noise of an input / output device of a programmable controller for transferring to a programmable controller main body, a digital input signal after analog / digital conversion is sampled a plurality of times, and the sampled digital input signal is subjected to a first operation. The high-frequency component of noise is removed by averaging with a filter, the processed digital input signal is stored in the memory, and the processed digital input signal at this time and the past digital input signal on the memory are stored. A low-frequency component of noise is removed by performing a moving average by the second arithmetic unit. .

[0008]

In the present invention, attention is paid to the signal characteristic peculiar to the programmable controller that the input signal sent from the controlled object device to the programmable controller side is held and output during the sequence operation cycle of the programmable controller main body. A noise component included in the input signal is removed by performing the averaging process and the moving average process.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Before describing the processing according to the present invention, the noise elimination circuit according to the present invention will be described with reference to FIG. The configuration of the input / output unit is almost the same as that of the conventional example shown in FIG. 9, but instead of the filter 10 of FIG. 9, the averaging circuit of FIG. 2 is provided on the output side of the A / D converter 8. The difference between the configuration of the conventional example and that of the present embodiment is that an arithmetic unit) is connected.

In FIG. 2, reference numeral 21 is a D-type flip-flop, which samples the output of the A / D converter 8 for each clock and holds and outputs it to the flip-flop 21 on the downstream side and also outputs to the adder 22. To do. The adder 22 adds the output of the flip-flop 21 and the cumulative output one clock before the output. In the circuit example of FIG. 2, 4 points of A / D sampled at 4 clocks per channel
The total output of the converter 8 is averaged by the divider 23. The noise removal processing according to the present invention will be described below with reference to FIGS. 4 and 5. Incidentally. 4 and 5 show MPU5
Shows the steps performed by. As an example of the description, a case where the number of input points is 10, that is, there are 10 input channels will be described as an example. In addition, in this embodiment, sampling is performed four times in order to input one input signal.

Programmable controller body 1 is RA
After reading the input signals for 10 points stored in M7, M
PU5 executes the control procedure of FIG. When the MPU 5 initializes the channel to "1", the multiplexer 9 outputs the output of the first channel (the uppermost amplifier 10 of FIG. 9) to the averaging circuit of FIG. As described above, the averaging circuit of FIG. 2 performs the averaging process by sampling the input signal four times at different time points within the fixed time (see FIG. 3) and outputs the average of the sampling data (Q1 of FIG. 3) to the input signal. And hand it over to MPU5. The MPU 5 receives the input signal R
It is stored in the first channel allocation area of AM7 (S20 to S30 in FIG. 4).

Hereinafter, the MPU 5 switches the channel,
The average output of the second channel and the average output of the third channel are sequentially written in the RAM 5 (S20 to S4 in FIG. 4).
0 → S50 loop process). When the average output of all the channels is input, the MPU 5 next performs the control procedure of FIG. 5 as the second computing unit of the present invention to perform the moving average processing for each channel. The moving average process is a fixed number of consecutive numbers (in the example of FIG. 1 of the present embodiment, 3
It is the process of calculating the average of the data of points. Figure 3
In the example, the average output Q3 obtained in the past is the average output Q1,
The moving average value of Q2 and the current average output Q3 is calculated, and this moving average value is determined as the value of the final input signal. The moving average value calculated for each channel by the MPU 5 in this way is stored in the RAM 7 (S in FIG. 5).
110 to S150), and is delivered to the programmable controller body 1 side.

By performing the averaging process as described above, the high frequency components of noise contained in the analog input signal are reduced (smoothed) as schematically shown in FIG. 6 before the averaging process is performed. Further, the low frequency component of noise is reduced by the moving average process, as schematically shown in FIG. Further, by combining the two averaging processes, the noise component is almost removed, as schematically shown in FIG.

Further, since the simple averaging operation can be realized by the software operation of the MPU 5, it is not necessary to provide a dedicated filter circuit for noise removal, and the manufacturing connel does not become extremely expensive.

Besides the present embodiment, the following example can be realized.

1) In this embodiment, the simple averaging process is executed by the arithmetic unit (adder and divider), but it may be realized by the software process of the MPU 5. In this case, the number of program steps is shorter and the processing time is shorter if the simple average processing and the moving average processing are successively executed for each channel.

[0018]

As described above, according to the present invention, noise of an input signal can be removed with a simple circuit structure, which can contribute to downsizing of the device and reduction of manufacturing cost.

[Brief description of drawings]

FIG. 1 is a timing chart showing sampling timing of an input signal in an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an averaging circuit in the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a moving average processing timing in the embodiment of the present invention.

FIG. 4 is a flowchart showing a processing procedure of the MPU 5 in the embodiment of the present invention.

FIG. 5 is a flowchart showing a processing procedure of the MPU 5 in the embodiment of the present invention.

FIG. 6 is a diagram showing noise removal characteristics obtained by averaging processing.

FIG. 7 is a diagram showing noise removal characteristics obtained by moving processing.

FIG. 8 is a diagram showing noise removal characteristics obtained by averaging processing and moving average processing.

FIG. 9 is a block diagram showing a system configuration of a conventional input / output unit.

FIG. 10 is a timing chart for explaining the operation of the system of the conventional input / output unit.

[Explanation of symbols]

 1 programmable controller main body 2 I / O 3 bus 4 bus interface 5 MPU 6 ROM 7 RAM 8 A / D converter 9 multiplexer 10 (for noise removal) filter

Claims (1)

[Claims] 1. An input / output device of a programmable controller input / output device, which removes noise in the input / output device, and performs analog / digital conversion on an analog input signal sent from a device to be controlled, and transfers the analog / digital conversion to a programmable controller main body. In the method of removing noise, the digital input signal after analog / digital conversion is sampled a plurality of times, the high frequency component of noise is removed by averaging the sampled digital input signal by the first calculator, and A digital input signal is stored in a memory, and a low frequency component of noise is removed by moving averaging the digital input signal after the current processing and the past digital input signal on the memory by a second computing unit. A method for eliminating noise in an input / output device of a programmable controller, characterized by