Input device and noise removal method

Abstract

A digital input unit (1) comprising: a digital input circuit (11) connected to a connection device (3) that outputs an analog signal, for capturing the analog signal and converting it into a digital signal; an analog input circuit (12) for capturing the analog signal; a digital input circuit filter (13) for removing noise from the digital signal converted by the digital input circuit (11); and a control unit (14) for setting a digital filter constant of the digital input circuit filter based on the analog signal captured by the analog input circuit and a noise detection parameter.

Description

Technical Field

[0001] The present disclosure relates to an input device and a noise removal method.

Background Art

[0002] During the operation of equipment, device abnormalities may occur due to incorrect input. The main cause is that noise is superimposed on the input signal of the digital input unit, and the digital input unit determines the noise as an input. To address this problem, generally, a filter for ignoring or removing noise signals is provided. This filter includes not only a circuit combination of a capacitor and a resistor but also one that periodically samples the input signal and processes it digitally. In a digital filter (hereinafter referred to as a digital filter), generally, when a plurality of sampling data continuously match, the matched data is processed as an input. By changing the number of matches and the sampling period (hereinafter referred to as the digital filter constant), the characteristics of the digital filter, that is, the response speed and the noise removal performance, can be changed. The response speed and the noise removal performance of the digital filter are in an inverse relationship, that is, when the response speed is improved, the noise removal performance deteriorates. Therefore, it is desirable to change the digital filter constant according to the situation.

[0003] Patent Document 1 discloses a technique for a user to adjust digital filter constants via a tool. Even when the user sets optimal digital filter constants using the technique described in Patent Document 1, noise may change due to external factors such as partial changes in peripheral equipment or aging changes, and it may no longer be an optimal digital filter. In the worst case, when it is no longer an optimal digital filter, noise may be judged as an input and lead to device abnormalities. Therefore, it is required to automatically set an optimal digital filter according to the state of noise for users other than those who emphasize response speed. Optimal digital filter setting means setting the digital filter constants to remove only the noise contained in the input signal and improve the response speed. Therefore, in order to automatically set an optimal digital filter, it is necessary to detect the noise contained in the input signal.

[0004] Patent Document 2 discloses a technique related to noise detection. The technique described in Patent Document 2 is a technique related to the fault diagnosis test of a safety device. By measuring the noise input before the fault diagnosis test is performed, a test pulse width for fault diagnosis that is not affected by the noise is calculated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 1 is a technology in which a user sets digital filter constants via a tool. The noise detection method described in Patent Document 2 compares the voltage threshold value for noise determination set in advance with the voltage value of the noise signal, and determines that it is noise when the voltage value of the noise signal is greater than the threshold value for noise determination. Therefore, for a signal containing an input signal and noise, noise cannot be detected. Therefore, even by using the technologies described in Patent Document 1 and Patent Document 2, it is not possible to automate the optimal digital filter setting.

[0007] The present disclosure has been made to solve the above problems, and an object thereof is to automate the optimal digital filter setting for removing noise from an input signal.

Means for Solving the Problems

[0008] To achieve the above object, an input device according to the present disclosure is connected to a connection device that outputs an analog signal, and includes a digital input circuit, an analog input circuit, a digital input circuit filter, and a control unit. The digital input circuit captures an analog signal and converts it into a digital signal. The analog input circuit captures an analog signal. The digital input circuit filter removes noise from the digital signal converted by the digital input circuit. The control unit sets the digital filter constant of the digital input circuit filter based on the analog signal captured by the analog input circuit and the noise detection parameter. The noise detection parameter is the minimum and maximum values of the normal ON / OFF slew rate time in the analog signal. The control unit generates an analog signal that simulates a digital signal based on the analog signal and the ON / OFF threshold value of the digital input circuit, and determines whether it is a normal ON / OFF slew rate or an ON / OFF slew rate due to noise by comparing the noise detection parameter with the ON / OFF slew rate time of the analog signal, detects the misjudgment location due to noise in the analog signal, calculates the ON / OFF period due to noise based on the misjudgment location, and sets the digital filter constant corresponding to the ON / OFF period as the set value of the digital input circuit.

Effects of the Invention

[0009] According to the present disclosure, the digital input circuit and the analog input circuit capture the input signal from the connection device, and the control unit sets the digital filter constant of the digital input circuit filter based on the analog signal waveform of the input signal captured by the analog input circuit and the noise detection parameter, thereby automating the optimal digital filter setting for removing noise from the input signal.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, the input device and the noise removal method according to the present embodiment will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. In the present embodiment, an example in which a digital input unit is applied as the input device will be described.

[0012] The configuration of the digital input unit 1 according to the embodiment will be described with reference to FIG. 1. The digital input unit 1 includes a digital input circuit 11 that is connected to a connected device 3, captures an input signal from the connected device 3, and converts it into a digital signal; an analog input circuit 12 that captures the input signal from the connected device 3; a digital input circuit filter 13 that removes noise from the digital signal obtained by converting the input signal; and a control unit 14 that detects noise based on a noise detection parameter, which is a parameter for detecting the input signal waveform captured by the analog input circuit 12 and the noise acquired via the communication unit 15, and sets the digital filter constant of the digital input circuit filter 13.

[0013] The user terminal 2 used by the user includes a setting unit 21 that receives the setting of noise detection parameters by the user and transmits the set noise detection parameters to the digital input unit 1, and a display unit 22 that displays a setting screen for the noise detection parameters.

[0014] The input signal from the connected device 3 is distributed and taken into the digital input circuit 11 and the analog input circuit 12. The digital input circuit 11 uses an ON / OFF threshold value to convert the captured input signal into a digital signal, and sends it to the control unit 14 via the digital input circuit filter 13. The analog input circuit 12 sends the analog signal waveform of the captured input signal to the control unit 14.

[0015] A method for removing noise by setting the digital filter constant of the digital input circuit filter 13 performed by the control unit 14 will be described with reference to FIGS. 2, 3, and 4. The control unit 14 generates a digital signal (hereinafter referred to as a simulated signal) that simulates the digital signal converted by the digital input circuit 11 based on the analog signal waveform and the ON / OFF threshold value of the digital input circuit 11. For example, as shown in FIG. 2, for the analog signal waveform, when the ON / OFF threshold value of the digital input circuit is set to V ON_TH ,V OFF_TH , when the analog signal exceeds V ON_TH , the simulated signal outputs High, and when the analog signal is below V OFF_TH , the simulated signal outputs Low to generate a simulated signal.

[0016] The control unit 14 acquires the noise detection parameters in advance via the communication unit 15. The noise detection parameters are the minimum value and the maximum value of the normal ON / OFF slew rate time in the input signal of the connected device 3. Let the minimum value of the normal ON / OFF slew rate time be T ON_TH_MIN ,T OFF_TH_MIN , and the maximum value be T ON_TH_MAX ,T OFF_TH_MAX . The control unit 14 compares the noise detection parameters with the ON / OFF slew rate time T ON ,T OFFBy comparing, it is determined whether it is a normal ON / OFF throughput rate or an ON / OFF throughput rate due to noise, and the misjudgment location due to noise in the analog signal is detected.

[0017] The criteria for discriminating between a normal ON / OFF throughput rate and an ON / OFF throughput rate due to noise using noise detection parameters are as follows (1) to (4). (1) Normal ON throughput rate: T ON_TH_MIN ≦T ON ≦T ON_TH_MAX (2) Normal OFF throughput rate: T OFF_TH_MIN ≦T OFF ≦T OFF_TH_MAX (3) ON throughput rate due to noise: T ON <T ON_TH_MIN ,T ON_TH_MAX <T ON (4) OFF throughput rate due to noise: T OFF <T OFF_TH_MIN ,T OFF_TH_MAX <T OFF

[0018] When the analog signal waveform shown in FIG. 2 is sent, the control unit 14 determines the ON / OFF throughput time T of the analog signal waveform ON1 ,T OFF1 ,T ON2 ,T OFF2 ,T ON3 ,T OFF3 ,T ON4 ,T OFF4 and applies it to the criteria of (1) to (4), and T ON1 ,T OFF2 ,T ON3 ,T OFF4 is determined as a normal ON / OFF throughput rate, and T OFF1 ,T ON2 ,T OFF3 ,T ON4Determine it as the ON / OFF through-rate due to noise. A simulated signal obtained by simulating the analog signal waveform shown in FIG. 2 is shown in FIG. 3. The control unit 14 determines that the rising and falling edges of the waveform correction time T in the simulated signal shown in FIG. 3 are the misjudgment locations of the digital input circuit 11 caused by noise.

[0019] The control unit 14 calculates the ON / OFF periods T ON_Noise , T OFF_Noise generated by noise from the misjudgment locations in the simulated signal. The control unit 14 stores in advance a digital filter constant table indicating the digital filter constants corresponding to the ON / OFF periods due to noise, and the calculated ON / OFF periods T ON_Noise , T OFF_Noise corresponding to it are set as the setting values of the digital input circuit filter 13.

[0020] For example, as shown in FIG. 3, when the simulated signal becomes OFF during the waveform correction time T due to noise, the waveform correction time T is T OFF_Noise . The control unit 14 sets the digital filter constant corresponding to the waveform correction time T in the digital input circuit filter 13 from the digital filter constant table to correct the input signal. Thereby, the noise of the input signal is removed.

[0021] Here, the noise removal process performed by the digital input unit 1 will be described with reference to FIG. 5. The noise removal process starts, for example, when the digital input circuit 11 and the analog input circuit 12 capture the input signal from the connected device 3. The control unit 14 generates a simulated signal that simulates the digital signal converted by the digital input circuit 11 based on the analog signal waveform and the ON / OFF threshold of the digital input circuit 11 (step S11).

[0022] For example, as shown in FIG. 2, when V ON_TH , V OFF_TH is set as the ON / OFF threshold of the digital input circuit with respect to the analog signal waveform, when the analog signal is V ON_THWhen it exceeds, the analog signal outputs High, and when the analog signal is lower than V OFF_TH it generates an analog signal that outputs Low.

[0023] Returning to FIG. 5, the control unit 14 compares the noise detection parameter with the ON / OFF slew rate time T ON , T OFF to determine whether it is a normal ON / OFF slew rate or an ON / OFF slew rate due to noise, and detects the misjudgment location due to noise in the analog data (step S12).

[0024] For example, when the analog signal waveform shown in FIG. 2 is sent, the control unit 14 determines the ON / OFF slew rate times T ON1 , T OFF1 , T ON2 , T OFF2 , T ON3 , T OFF3 , T ON4 , T OFF4 against the above-mentioned criteria (1) to (4), determines T ON1 , T OFF2 , T ON3 , T OFF4 as a normal ON / OFF slew rate, and determines T OFF1 , T ON2 , T OFF3 , T ON4 as an ON / OFF slew rate due to noise. The analog signal simulating the analog signal waveform shown in FIG. 2 is shown in FIG. 3. The control unit 14 determines that the falling and rising locations of the waveform correction time T in the analog signal shown in FIG. 3 are misjudgment locations of the digital input circuit 11 caused by noise.

[0025] Returning to FIG. 5, the control unit 14 calculates the ON / OFF periods T ON_Noise , T OFF_Noise generated by noise from the misjudgment locations in the analog signal (step S13). The control unit 14 stores in advance a digital filter constant table indicating the digital filter constants corresponding to the ON / OFF periods due to noise, and the calculated ON / OFF periods T due to noiseON_Noise , T OFF_Noise Set the digital filter constant corresponding to it in the digital input circuit filter 13 (step S14), and end the process.

[0026] Note that the control unit 14 may generate an analog signal when setting the digital filter constant corresponding to noise for the analog signal, that is, an analog signal with noise removed. In this case, the analog signal with noise removed generated by the control unit 14 is shown in FIG. 4. The analog signal shown in FIG. 4 is an analog signal with noise removed from the analog signal shown in FIG. 3. The control unit 14 transmits the analog signal waveform of the input signal, the digital signal waveform of the analog signal before noise removal, and the digital signal waveform of the analog signal after noise removal to the user terminal 2 and displays them on the display unit 22. Alternatively, it may be output to a display device (not shown) for display. Thereby, the noise of the input signal can be visualized, facilitating adjustment when the user can adjust the digital input circuit filter 13, and also facilitating review of peripheral devices and wiring when noise removal is impossible even after adjusting the digital input circuit filter 13.

[0027] According to the digital input unit 1 according to the embodiment, the digital input circuit 11 and the analog input circuit 12 capture the input signal from the connected device 3, and the control unit 14 sets the digital filter constant of the digital input circuit filter 13 based on the analog signal waveform of the input signal captured by the analog input circuit 12 and the noise detection parameter, thereby automating the optimal digital filter setting for removing the noise of the input signal.

[0028] In the above-described embodiment, the user sets the noise detection parameters in the setting unit 21 of the user terminal 2, and the control unit 14 acquires the noise detection parameters from the setting unit 21 via the communication unit 15. However, the present invention is not limited to this. For example, the control unit 14 may obtain the noise detection parameters of the connected device 3 from external information. A configuration example of the digital input unit 1 according to this modification 1 is shown in FIG. 6. The digital input unit 1 is the same as the configuration example of the digital input unit 1 shown in FIG. 1, but the control unit 14 acquires external information from an external device or system 4 via the communication unit 15, and obtains the noise detection parameters of the connected device 3 from the external information. In this case, the control unit 14 receives, for example, an input of the model name of the connected device 3, requests and acquires the noise detection parameters of the connected device 3 from an external device or system 4 via the communication unit 15, or acquires external information corresponding to the model name of the connected device 3 and extracts the noise detection parameters of the connected device 3 from the external information. Alternatively, in the configuration example of the digital input unit 1 shown in FIG. 1, the setting unit 21 may receive an input of the model name of the connected device 3, request and acquire the noise detection parameters of the connected device 3 from an external device or system 4, or acquire external information corresponding to the model name of the connected device 3 and extract the noise detection parameters of the connected device 3 from the external information.

[0029] In addition, the control unit 14 may store the noise detection parameters in advance. A configuration example of the digital input unit 1 according to this modification 2 is shown in FIG. 7. The digital input unit 1 includes a digital input circuit 11, an analog input circuit 12, a digital input circuit filter 13, and a control unit 14. The control unit 14 stores in advance a noise detection parameter table indicating the noise detection parameters for each connected device 3. In this configuration, the control unit 14 switches the noise detection parameters according to the connected device 3 connected to the digital input unit 1.

[0030] Note that the present disclosure can be implemented in various embodiments and variations without departing from the broad spirit and scope of the present disclosure. Further, the above-described embodiments are for explaining this disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is indicated by the claims rather than the embodiments. And various modifications made within the scope of the claims and within the scope of the meaning of the disclosure equivalent thereto are considered to be within the scope of this disclosure.

Explanation of Reference Numerals

[0031] 1 Digital input unit, 2 User terminal, 3 Connecting device, 4 External device or system, 11 Digital input circuit, 12 Analog input circuit, 13 Digital input circuit filter, 14 Control unit, 15 Communication unit, 21 Setting unit, 22 Display unit.

Claims

1. Connected to a connection device that outputs an analog signal, A digital input circuit that captures the analog signal and converts it into a digital signal; An analog input circuit that captures the analog signal; A digital input circuit filter that removes noise from the digital signal converted by the digital input circuit; A control unit that sets a digital filter constant of the digital input circuit filter based on the analog signal captured by the analog input circuit and noise detection parameters; Comprising: The noise detection parameters are: The minimum and maximum values of the normal ON / OFF slew rate time in the analog signal; The control unit: Generates an analog signal simulating the digital signal based on the analog signal and the ON / OFF threshold value of the digital input circuit, compares the noise detection parameters with the ON / OFF slew rate time of the analog signal to determine whether it is a normal ON / OFF slew rate or an ON / OFF slew rate due to noise, detects the misjudgment location due to noise in the analog signal, calculates the ON / OFF period due to noise based on the misjudgment location, and sets the digital filter constant corresponding to the ON / OFF period as the set value of the digital input circuit; Input device.

2. The control unit: Generates an analog signal with noise removed by setting the digital filter constant corresponding to the ON / OFF period as the set value of the digital input circuit, and outputs the digital signal waveforms of the analog signal before noise removal and the analog signal after noise removal, which are the same as the digital signal waveform of the analog signal, to a display device or a user terminal; The input device according to claim 1.

3. The control unit acquires the noise detection parameters of the connection device from external information obtained from an external device or system; The input device according to claim 1 or 2.

4. The control unit stores in advance a noise detection parameter table indicating the noise detection parameters for each connection device, and switches the noise detection parameters according to the connected connection device; The input device according to claim 1 or 2.

5. Connected to a connection device that outputs an analog signal, a digital input circuit that captures the analog signal and converts it into a digital signal, an analog input circuit that captures the analog signal, and an input device including a digital input circuit filter that removes noise from the digital signal, having a step of setting a digital filter constant of the digital input circuit filter based on the analog signal captured by the analog input circuit and a noise detection parameter; wherein the noise detection parameter is the minimum and maximum values of the normal ON / OFF slew rate time in the analog signal; In the step of setting the digital filter constant, an analog signal simulating the digital signal is generated based on the analog signal and the ON / OFF threshold value of the digital input circuit, and by comparing the noise detection parameter with the ON / OFF slew rate time of the analog signal, it is determined whether it is a normal ON / OFF slew rate or an ON / OFF slew rate due to noise, and the misjudgment location due to noise in the analog signal is detected. Based on the misjudgment location, the ON / OFF period due to noise is calculated, and the digital filter constant corresponding to the ON / OFF period is set as the set value of the digital input circuit. Noise removal method.

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