Signal line noise removal system

Abstract

To provide a signal line noise removal system that can improve the accuracy of noise removal.SOLUTION: A signal line noise removal system (1) includes a transmitter (10), a signal cable (20), and a receiver (30). The signal cable includes a communication line, an inner insulating layer (L1) formed of a cylindrical insulating material and covering the outer surface of the communication line, and a cylindrical power line (W2) covering the outer surface of the inner insulating layer and arranged coaxially with the communication line and the inner insulating layer. The receiver (30) performs frequency analysis on the power line and removes components of a frequency band corresponding to the results of the frequency analysis from a communication signal transmitted from the communication line.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a noise removal system for a signal line. [Background technology]

[0002] Conventionally, a removal system for removing noise superimposed on a signal line has been known.

[0003] In this regard, Patent Document 1 discloses a power line communication network system including a plurality of power line communication devices that communicate using power lines, and a noise filter that is provided between the power line and a noise interference device that generates noise on the power line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-290288 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology described in Patent Document 1, the communication signal is superimposed on the power line, which increases the noise generated from the power line. Therefore, in the technology described in Patent Document 1, a separate noise removal device is provided between the power line and the device connected to the power line in order to suppress the increased noise generated from the power line, which causes a problem of reduced noise removal accuracy.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to improve the accuracy of noise removal in a noise removal system for a signal line. [Means for solving the problem]

[0007] In order to solve the above problem, the signal line noise removal system of the present invention includes a transmitting device, a communication line that transmits a communication signal sent from the transmitting device, a signal cable having an inner insulating layer formed of a cylindrical insulating material and arranged to cover the outer surface of the communication line, and a cylindrical power line that covers the outer surface of the inner insulating layer and is arranged coaxially with the communication line and the inner insulating layer, and a receiving device that performs frequency analysis on the power line and removes frequency band components from the communication signal transmitted from the communication line according to the results of the frequency analysis.

[0008] The signal cable further includes an outer insulating layer formed of a cylindrical insulating material and arranged to cover the outer surface of the power line, and a cylindrical shield wire arranged to cover the outer surface of the outer insulating layer and coaxial with the power line and the outer insulating layer.

[0009] The receiving device also performs the frequency analysis on the potential difference between the shield wire and the power line.

[0010] The receiving device also removes only components of the communication signal that are equal to or lower than a predetermined potential from components in a frequency band according to the result of the frequency analysis.

[0011] In addition, the transmitting device transmits the communication signal frequency-modulated at a predetermined frequency to the communication line, and the receiving device demodulates the communication signal at the predetermined frequency after removing components of the frequency band according to the result of the frequency analysis. [Effects of the Invention]

[0012] According to the present invention, the signal line noise removal system can improve the accuracy of noise removal. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating the overall configuration of a noise removal system according to an embodiment of the present invention. [Figure 2]FIG. 2 is a diagram illustrating an example of a specific configuration of the noise removal system illustrated in FIG. [Figure 3] 3 is a cross-sectional view taken along line III-III of the signal cable shown in FIG. 2. [Figure 4] 2 is a graph showing an example of a waveform of a power supply potential transmitted through the power line shown in FIG. [Figure 5] 2 is a graph showing an example of the spectrum of a power supply potential transmitted through the power line shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components and steps in each drawing will be designated by the same reference numerals as much as possible, and redundant description will be omitted.

[0015] 1 is a schematic diagram showing the overall configuration of a noise removal system 1 according to this embodiment. As shown in FIG. 1, the main components of the signal line noise removal system 1 include a transmitting device 10, a signal cable 20, and a receiving device 30.

[0016] The transmitting device 10 is a device that transmits a communication signal S1 (see FIG. 2) to the receiving device 30 via a signal cable 20. The transmitting device 10 generates the communication signal S1 and transmits the generated communication signal S1 to the receiving device 30 via a communication line W1 in the signal cable 20. The transmitting device 10 also has an AC voltage source 11. The AC voltage source 11 generates a power supply potential V1 (see FIG. 2) based on a reference potential GND and supplies the generated power supply potential V1 to each component in the transmitting device 10 as the power supply potential V1. The AC voltage source 11 also supplies the generated power supply potential V1 to the receiving device 30 via a power line W2 in the signal cable 20.

[0017] The signal cable 20 is, for example, a composite cable having a communication line W1 and a power line W2. The communication line W1 transmits a communication signal S1 transmitted from the transmitting device 10 to the receiving device 30. The power line W2 supplies a power supply potential V1 supplied from the AC voltage source 11 of the transmitting device 10 to the receiving device 30.

[0018] The receiving device 30 is, for example, a control device for controlling industrial machinery or various components provided at various locations on a robot, and receives the signal and power transmitted from the transmitting device 10 via the signal cable 20. The receiving device 30 operates using the power supply potential V1 supplied from the power line W2 of the signal cable 20 as its power source. The receiving device 30 also performs frequency analysis on the power line W2, and removes components of the communication signal S1 transmitted from the communication line W1 of the signal cable 20 in a frequency band corresponding to the results of the frequency analysis on the power line W2.

[0019] The above describes the overall configuration of the signal line noise removal system 1. Next, we will explain the specific configuration of the noise removal system 1. Figure 2 is a diagram showing an example of the specific configuration of the noise removal system 1 shown in Figure 1.

[0020] As shown in FIG. 2, the main components of the transmitting device 10 include, in addition to an AC voltage source 11, a signal generating unit 12, a modulating unit 13, and a multiplier 14, for example. The AC voltage source 11 generates a power supply potential V1. The positive terminal + of the AC voltage source 11 is connected to the power supply terminals of the components of the transmitting device 10 and to a power line W2 of the signal cable 20, and the negative terminal − is connected to a reference line W_GND. The AC voltage source 11 supplies the power supply potential V1 to the signal generating unit 12, the modulating unit 13, and the multiplier 14. The AC voltage source 11 also supplies the power supply potential V1 to the receiving device 30 via the power line W2 of the signal cable 20.

[0021] Signal generating unit 12 generates signal S0 that is the source of communication signal S1 and outputs the generated signal S0 to multiplier 14. Furthermore, signal generating unit 12 has a power supply terminal connected to the positive terminal + of AC voltage source 11, a reference terminal connected to reference line W_GND, and is operated by power supply potential V1 supplied from AC voltage source 11.

[0022] Modulation unit 13 generates a carrier wave having a predetermined frequency used when frequency modulating signal S0, and outputs the generated carrier wave to multiplier 14. When generating the carrier wave, modulation unit 13 uses a predetermined frequency that is stored in advance, or acquires information about the predetermined frequency from a signal transmitted from outside modulation unit 13. Modulation unit 13 has a power supply terminal connected to the positive terminal + of AC voltage source 11, a reference terminal connected to reference line W_GND, and operates with power supply potential V1 supplied from AC voltage source 11.

[0023] Multiplier 14 performs frequency modulation on signal S0 with a predetermined frequency, which is the frequency of a carrier wave. Specifically, multiplier 14 performs frequency modulation on signal S0 with the predetermined frequency by multiplying signal S0 generated by modulation unit 13 by a carrier wave having the predetermined frequency, which is also generated by modulation unit 13. Multiplier 14 transmits the frequency-modulated signal as communication signal S1 to receiving device 30 via communication line W1 of signal cable 20. Multiplier 14 has a power supply terminal connected to the positive terminal + of AC voltage source 11, a reference terminal connected to reference line W_GND, and is operated by power supply potential V1 supplied from AC voltage source 11.

[0024] The signal cable 20 mainly includes, for example, a communication line W1, a power line W2, a shielded wire W3, an inner insulating layer L1, and an outer insulating layer L2. The structure of the signal cable 20 will now be described in detail with reference to Fig. 3. Fig. 3 is a cross-sectional view of the signal cable 20 taken along line III-III in Fig. 2.

[0025] 3, the signal cable 20 includes, for example, a communication line W1, an inner insulating layer L1, a power line W2, an outer insulating layer L2, and a shielding line W3, in this order from the inside to the outside in the radial direction. That is, the communication line W1, the inner insulating layer L1, the power line W2, the outer insulating layer L2, and the shielding line W3 are arranged isotropically and concentrically.

[0026] The communication line W1 is a line for transmitting the communication signal S1 transmitted from the transmitting device 10 to the receiving device 30, and is made of a conductor such as copper or aluminum. The communication line W1 is provided along the axis P at the center of the signal cable 20, and has an outer diameter D1.

[0027] The inner insulating layer L1 is a layer for providing electrical insulation between the communication line W1 and the power line W2, and is formed into a cylindrical shape using an insulating material. The insulating material is a synthetic resin such as foamed polyethylene or polytetrafluoroethylene. The inner insulating layer L1 is provided to cover the outer surface of the communication line W1, and has an outer diameter D2 that is larger than the outer diameter D1 of the communication line W1 (D2>D1).

[0028] The power line W2 is a line for supplying the power supply potential V1, which is supplied from the AC voltage source 11, to the receiving device 30, and is formed into a cylindrical shape using a conductor such as copper or aluminum. The power line W2 is provided so as to cover the outer peripheral surface of the inner insulating layer L1 and is coaxial with the communication line W1 and the inner insulating layer L1. The power line W2 has an outer diameter D3 that is larger than the outer diameter D2 of the inner insulating layer L1 (D3>D2). Note that, because the power line W2 is provided coaxially with the communication line W1, the shortest distance from the inner peripheral surface of the power line W2 to the outer peripheral surface of the communication line W1 is substantially the same at any point.

[0029] The outer insulating layer L2 is a layer for providing electrical insulation between the power line W2 and the shielded wire W3, and is formed into a cylindrical shape from an insulating material. The outer insulating layer L2 is provided to cover the outer surface of the power line W2, and has an outer diameter D4 that is larger than the outer diameter D3 of the power line W2 (D4>D3).

[0030] The shield wire W3 is a wire for reducing the effect of noise applied from outside the signal cable 20 on the communication line W1 and the power line W2. One end is connected to the reference line W_GND of the transmitter 10, and the other end is connected to the reference line W_GND2 of the receiver 30. The shield wire W3 is formed into a cylindrical shape from a conductor such as copper or aluminum, and is arranged so as to cover the outer surface of the outer insulating layer L2 and to be coaxial with the communication line W1, the inner insulating layer L1, the power line W2, and the outer insulating layer L2. The outer diameter of the shield wire W3 is D5, which is larger than the outer diameter D4 of the outer insulating layer L2 (D5>D4).

[0031] In this example, the signal cable 20 is formed to have flexibility that allows it to be bent, but this is not limiting and the signal cable 20 may have flexibility that makes it difficult to bend by hand. The signal cable 20 may further be provided with an outer coating made of an insulating material such as polyethylene, polyvinyl chloride, or polytetrafluoroethylene, which covers the outer surface of the shielded wire W3 and provides insulation between the signal cable 20 and the outside.

[0032] 2, the receiving device 30 is mainly configured to include, for example, an analysis unit 31, a removal unit 32, a demodulation unit 33, and a processing unit 34. The analysis unit 31 is, for example, an impedance analyzer, and performs frequency analysis on the power line W2 and transmits the result of the frequency analysis to the removal unit 32.

[0033] Here, frequency analysis will be described with reference to FIGS. 4 and 5. FIG. 4 is a graph showing an example of the waveform of the power supply potential V1 transmitted through the power line W2 shown in FIG. 1. FIG. 5 is a graph showing an example of the spectrum of the power supply potential V1 transmitted through the power line W2 shown in FIG. 1. The analysis unit 31 performs frequency analysis on the signal waveform of the power supply potential V1, which is the potential difference between the power line W2 and the shielded wire W3 as shown in FIG. 4, using a technique such as FFT (Fast Fourier Transform). The analysis unit 31 calculates the spectral intensity of the power supply potential V1 for each frequency as shown in FIG. 5 through the frequency analysis. Here, the spectral intensity may be, for example, the amplitude of the power supply potential V1 in each predetermined frequency band, a value proportional to the amplitude, or a value proportional to the value obtained by raising the amplitude to a predetermined power. As shown in FIG. 5, the spectral intensity of the power supply potential V1 is greatest in a frequency band including the power supply frequency determined by the AC voltage source 11.

[0034] Returning to FIG. 2, the elimination unit 32 removes components of a frequency band corresponding to the result of frequency analysis by the analysis unit 31 from the communication signal S1 transmitted from the communication line W1 of the signal cable 20. Specifically, the elimination unit 32 acquires the result of the frequency analysis from the analysis unit 31 and selects a frequency band that is equal to or lower than a predetermined potential from among the predetermined frequency bands. The predetermined potential is, for example, a potential determined by the threshold related to the spectral intensity in FIG. 5 described above. For each selected frequency band, the elimination unit 32 subtracts the amplitude value of the power supply potential V1 from the communication signal S1 to remove the components of the selected frequency band. The elimination unit 32 then outputs the subtraction result as signal S2 to the demodulation unit 33. The elimination unit 32 has a power terminal connected to the power line W2, a reference terminal connected to the reference line W_GND2, and operates on the power supply potential V1 supplied from the power line W2.

[0035] The demodulation unit 33 demodulates or detects the signal S2 transmitted from the removal unit 32 using a predetermined frequency that is the frequency of the carrier wave of the communication signal S1. The demodulation unit 33 outputs the result of the demodulation or detection as a signal S3 to the processing unit 34. The demodulation unit 33 has a power supply terminal connected to the power line W2 and a reference terminal connected to the reference line W_GND2, and operates using a power supply potential V1 supplied from the power line W2.

[0036] The processing unit 34 performs processing related to the operation of the receiving device 30 in accordance with the control command indicated by the signal S3 transmitted from the demodulation unit 33. If the receiving device 30 is, for example, a driving member provided at various locations on a robot, the processing unit 34 drives the receiving device 30 in accordance with the control command indicated by the signal S3. If the receiving device 30 is, for example, a control device for controlling industrial machinery, the processing unit 34 controls the operation of the industrial machinery in accordance with the control command indicated by the signal S3. The processing unit 34 has a power terminal connected to the power line W2 and a reference terminal connected to the reference line W_GND2, and is operated by the power supply potential V1 supplied from the power line W2.

[0037] <Action and effect> As described above, in this embodiment, the signal line noise removal system 1 includes a transmitting device 10, a signal cable 20 having a communication line W1 transmitting a communication signal S1, an inner insulating layer L1, and a power line W2, and a receiving device 30. The inner insulating layer L1 is formed of a cylindrical insulating material and is provided so as to cover the outer peripheral surface of the communication line W1. The power line W2 is formed in a cylindrical shape so as to cover the outer peripheral surface of the inner insulating layer L1 and be coaxial with the communication line W1 and the inner insulating layer L1. The receiving device 30 performs frequency analysis on the power line W2 and removes frequency band components corresponding to the results of the frequency analysis from the communication signal S1 transmitted from the communication line W1.

[0038] As a result, in the noise removal system 1, the magnetic field that a predetermined position of the power line W2 exerts on the communication line W1 is canceled out by the magnetic field that a position on the power line W2 that is symmetrical with respect to the communication line W1 exerts on the communication line W1, thereby reducing the effect of the power line W2 on the communication line W1. Furthermore, the noise removal system 1 removes components in a frequency band corresponding to the results of frequency analysis of the power line W2, thereby reducing noise exerted on the communication line W1 from outside the signal cable 20. Therefore, the noise removal system 1 can improve the accuracy of noise removal. Furthermore, the noise removal system 1 can particularly improve the accuracy of noise removal when the receiving device 30 is a device that is prone to generating noise and is easily affected by noise, such as an industrial robot with a proximity sensor.

[0039] In this embodiment, the signal cable 20 further includes an outer insulating layer L2 formed of a cylindrical insulating material and covering the outer peripheral surface of the power line W2, and a cylindrical shield wire W3 covering the outer peripheral surface of the outer insulating layer L2 and provided coaxially with the power line W2 and the outer insulating layer L2. Therefore, the noise removal system 1 can reduce the influence of external noise on the communication line W1 and the power line W2 by using the shield wire W3, thereby further improving the accuracy of noise removal.

[0040] In this embodiment, the receiving device 30 also performs frequency analysis on the potential difference between the shield wire W3 and the power line W2. Therefore, the noise removal system 1 can further remove the effects of noise that is applied from the outside to the communication line W1 and the power line W2 via the shield wire W3 and the outer insulating layer L2.

[0041] In this embodiment, the receiving device 30 removes only components of the communication signal S1 that are equal to or lower than a predetermined potential from among components in a frequency band according to the result of frequency analysis. Therefore, the noise removal system 1 removes only noise components that are externally applied to the power line W2, further improving the accuracy of noise removal.

[0042] In this embodiment, the transmitting device 10 transmits a communication signal S1 that has been frequency-modulated at a predetermined frequency to the communication line W1. The receiving device 30 removes components of a frequency band corresponding to the result of frequency analysis from the communication signal S1 and then demodulates the communication signal S1 at the predetermined frequency. Therefore, the noise removal system 1 transmits the frequency-modulated communication signal S1 from the transmitting device 10 to the receiving device 30, thereby improving the noise resistance of the communication signal S1.

[0043] <Modification> The present invention is not limited to the above-described embodiments. In other words, variations of the above-described embodiments, which are appropriately modified by a person skilled in the art, are also included within the scope of the present invention as long as they include the features of the present invention. Furthermore, the elements of the above-described embodiments and the modifications described below can be combined to the extent technically possible, and such combinations are also included within the scope of the present invention as long as they include the features of the present invention.

[0044] For example, in the present embodiment, the noise removal system 1 has the power line W2 formed in a cylindrical shape, but this is not limited thereto. The noise removal system 1 may have any shape as long as the power line W2 is symmetrical with respect to the communication line W1 when the signal cable 20 is viewed along line III-III in FIG. 2. For example, the power line W2 may be formed so that its cross section is a regular even polygon, such as a regular hexagon or a square, when viewed along line III-III in FIG. 2. With this configuration, the noise removal system 1 can improve the accuracy of noise removal even when the power line W2 is formed in various shapes.

[0045] Furthermore, in this embodiment, the noise removal system 1 transmits the communication signal S1, which is obtained by frequency-modulating the signal S0 at a predetermined frequency, from the transmitting device 10 to the receiving device 30 via the signal cable 20, but this is not limited to this. The noise removal system 1 may also modulate the signal S0 using a modulation method other than frequency modulation and transmit the modulated signal as the communication signal S1 from the transmitting device 10 to the receiving device 30 via the signal cable 20. Modulation methods other than frequency modulation include, for example, amplitude modulation and phase modulation. With this configuration, the noise removal system 1 can improve the accuracy of noise removal even when a modulation method other than frequency modulation is used to transmit the communication signal S1 from the transmitting device 10 to the receiving device 30.

[0046] Furthermore, in this embodiment, the analysis unit 31 of the noise removal system 1 performs frequency analysis on the potential difference between the power line W2 and the shield wire W3 connected to the reference lines W_GND and W_GND2, but this is not limited to this. When the analysis unit 31 of the noise removal system 1 analyzes the potential difference between the power line W2 and the power supply potential V1, any potential that can serve as a reference, such as ground potential, may be used as the reference. Furthermore, the noise removal system 1 does not require the signal cable 20 to be provided with the shield wire W3. With this configuration, the noise removal system 1 can improve the accuracy of noise removal even when the signal cable 20 does not have the shield wire W3. [Explanation of symbols]

[0047] 1...Removal system, 10...Transmitting device, 20...Signal cable, 30...Receiving device, L1...Inner insulating layer, L2...Outer insulating layer, W1...Communication line, W2...Power line, W3...Shielded wire

Claims

1. a transmitting device; a signal cable including a communication line for transmitting a communication signal transmitted from the transmitting device, an inner insulating layer formed of a cylindrical insulating material and provided so as to cover an outer peripheral surface of the communication line, and a cylindrical power line provided so as to cover the outer peripheral surface of the inner insulating layer and coaxially with the communication line and the inner insulating layer; a receiving device that performs a frequency analysis on the power line and removes components of a frequency band corresponding to a result of the frequency analysis from the communication signal transmitted from the communication line; A noise removal system for a signal line, comprising:

2. The signal cable an outer insulating layer formed of a cylindrical insulating material and provided to cover an outer peripheral surface of the power line; a cylindrical shield wire provided so as to cover an outer peripheral surface of the outer insulating layer and to be coaxial with the power line and the outer insulating layer; 2. The noise removal system for a signal line according to claim 1, further comprising:

3. 3. The noise removal system for a signal line according to claim 2, wherein the receiving device performs the frequency analysis on a potential difference between the shield line and the power line.

4. The signal line noise removal system according to any one of claims 1 to 3, characterized in that the receiving device removes only components of the communication signal that are below a predetermined potential from among components of a frequency band corresponding to the result of the frequency analysis.

5. the transmitting device transmits the communication signal, which is frequency-modulated at a predetermined frequency, to the communication line; The signal line noise removal system according to any one of claims 1 to 3, characterized in that the receiving device demodulates the communication signal at the predetermined frequency after removing components of the frequency band according to the result of the frequency analysis.

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