Method for suppressing external interference of metal detector

Abstract

The invention relates to the field of metal detectors, and discloses an external interference suppression method for a metal detector, which comprises the following steps: directly using a receiving coil in a probe coil system as a detection coil for external interference, or adding a group of auxiliary coils as the detection coil, and detecting an external interference signal received by the detection coil through a signal recovery module. The amplitude and the phase of a signal component of a specific frequency point in an external interference signal are obtained, the signal of the frequency point can be restored, and the restored signal is injected into the interference suppression coil in a manner of being equal in size and opposite in phase with an original signal, so that the signal component of the external interference signal at the specific frequency point is counteracted. The method for suppressing the external interference of the cover metal detector adopts an active interference suppression method, detects the external electromagnetic interference in real time, generates an offset signal and injects the offset signal into a probe coil, so that the external interference is eliminated, and the method does not need to carry out welding modification on equipment, does not occupy extra space and is high in adaptability.

Description

Technical Field

[0001] The present invention relates to the field of metal detectors, and in particular to a method for suppressing external interference of a metal detector. Background Art

[0002] A metal detector is a device that detects foreign matter (especially metal foreign matter) based on the changes in the electromagnetic field in the probe window. The electrical signal on the transmitting coil in the probe excites an electromagnetic field in the probe window, and the receiving coil in the probe detects this electromagnetic field and transmits its changes to subsequent components for processing. Metal detectors are based on electromagnetic field detection, so they are particularly sensitive to external electromagnetic field interference. The working environment of a metal detector requires a stable electromagnetic environment, and nearby high-power signal transmitting equipment or power equipment may have an impact on it. Metal detectors are widely used in various industrial production lines. At present, industrial equipment is becoming increasingly complex, and it is difficult to ensure a clean and stable electromagnetic environment. The probability of metal detectors being interfered with by external interference is increasing. Once interfered with, the metal detector will not work properly.

[0003] At present, there are not many measures to deal with electromagnetic interference of metal detectors. Generally, the detection window is shielded, such as welding shielding rings on both sides of the probe window, or placing the whole machine in a shielding cover, which is a passive suppression method. The effectiveness of the shielding ring is not high. Although the shielding cover is effective, it is expensive and requires a large installation space. It cannot be used in many occasions. For this reason, we propose a method for metal detectors to suppress external interference. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for suppressing external interference of a metal detector, which solves the above-mentioned problems.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a method for suppressing external interference of a metal detector, comprising the following steps:

[0006] S1: Use the receiving coil in the probe coil system as a detection coil for external interference;

[0007] S2: Use the transmitting coil in the probe coil system as an interference suppression coil;

[0008] S3: When the metal detector is working, it receives the external interference signal through the detection coil, and then obtains the amplitude and phase of the signal component of a specific frequency point in the external interference signal through the signal recovery module, and recovers the signal of the frequency point;

[0009] S4: Injecting the restored signal obtained in the above step S3 into the interference suppression coil in a manner of being equal to or opposite to the original signal, so as to offset the signal component of the external interference signal at a specific frequency point.

[0010] Preferably, a set of auxiliary coils can be added as detection coils in S1 to detect interference without stopping the normal detection of the metal detector. In this way, the normal detection of the metal detector can be realized in hardware. However, in order to detect external interference more sensitively, it is better to stop the normal detection of the metal detector and also suspend the signal transmission of the transmitting coil so that the detection coil can receive pure external interference signals.

[0011] One or more auxiliary coils can be added to S2 to serve as interference suppression coils. By arranging multiple suppression coils in the probe coil system, real-time cancellation of external interference signal components at multiple frequencies can be achieved simultaneously.

[0012] Preferably, when detecting the external interference signal in S3, the signal component of the external interference signal at the frequency point of the metal detector working frequency is tested first and suppressed, which can eliminate the problem of equipment being interfered with to a large extent. After that, detection can also be performed at frequency points near the working frequency point, or scanning can be performed on the entire frequency band to understand more about the noise distribution of the external interference signal. By detecting each frequency point of the external interference signal, information on its main interference component can be obtained.

[0013] Preferably, the method further includes: after the offset signal is injected, the system should continuously monitor the output signal of the detection coil to evaluate the interference suppression effect. If the interference signal is still not completely eliminated, the system can automatically adjust the parameters of the offset signal until the best suppression effect is achieved;

[0014] During the operation of the system, the interference detection and suppression strategy is dynamically adjusted to adapt to changes in the external environment. After confirming that the external interference is effectively suppressed, it switches back to the normal detection mode and resumes the signal transmission of the transmitting coil.

[0015] Preferably, the signal restoration module in S3 is used to obtain the amplitude and phase of the signal component of a specific frequency point in the external interference signal, and restore the signal of the frequency point, which specifically includes: transmitting the received interference signal to the signal restoration module for processing, the signal restoration module analyzes the interference signal in the frequency domain through algorithms such as fast Fourier transform (FFT), identifies the main interference frequency points and their corresponding signal components, and quantizes the identified signal components of the specific frequency points, including their amplitude and phase information. Using this information, the signal restoration module can restore the interference signal waveform of the frequency point.

[0016] Preferably, the restored signal obtained in S4 is injected into the interference suppression coil in a manner of being in a phase opposite to the original signal to offset the signal component of the external interference signal at a specific frequency point, specifically including: generating a cancellation signal in a phase opposite to the original interference signal based on the restored interference signal waveform, the cancellation signal having the same amplitude as the original interference signal but a completely opposite phase, and injecting the generated cancellation signal into the probe area through the transmitting coil or the additional auxiliary interference suppression coil. Since the cancellation signal and the original interference signal meet and overlap in space, they will cancel each other, thereby eliminating or significantly reducing the influence of the external interference signal on the metal detector.

[0017] Preferably, a metal detector external interference suppression system is designed to implement a metal detector external interference suppression method, comprising:

[0018] The probe coil system includes a receiving coil and a transmitting coil or multiple sets of auxiliary coils are added as detection coils and interference suppression coils;

[0019] A signal recovery module, used to process the received interference signal and generate a cancellation signal;

[0020] A control module for switching detection / suppression modes and managing the signal output of the transmitting coil;

[0021] At least one power supply and necessary circuit components to support normal operation of the system.

[0022] Preferably, the control module specifically connects multiple groups of coils in the probe coil system to an electronic network, and realizes dynamic adjustment of the coil load by controlling the resistance and capacitance.

[0023] Compared with the prior art, the present invention provides a method for suppressing external interference of a metal detector, which has the following beneficial effects:

[0024] 1. The metal detector suppresses external interference by actively suppressing interference, detecting external electromagnetic interference in real time, and generating a cancellation signal to inject into the probe coil, thereby eliminating external interference. This method does not require welding modification of the equipment, does not occupy additional space, and has strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the process of the method for suppressing external interference of a metal detector of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure of the probe coil system of the present invention;

[0027] Figure 3 This is a schematic diagram of the principle block diagram of the signal restoration module of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1-3 , a method for suppressing external interference of a metal detector, comprising the following steps:

[0030] S1: Use the receiving coil in the probe coil system as a detection coil for external interference;

[0031] S2: Use the transmitting coil in the probe coil system as an interference suppression coil;

[0032] S3: When the metal detector is working, it receives the external interference signal through the detection coil, and then obtains the amplitude and phase of the signal component of a specific frequency point in the external interference signal through the signal recovery module, and recovers the signal of the frequency point;

[0033] S4: Injecting the restored signal obtained in the above step S3 into the interference suppression coil in a manner of being equal to or opposite to the original signal, so as to offset the signal component of the external interference signal at a specific frequency point.

[0034] In S1, a set of auxiliary coils can be added as detection coils to detect interference without stopping the normal detection of the metal detector. In this way, the normal detection of the metal detector can be realized in hardware. However, in order to detect external interference more sensitively, it is better to stop the normal detection of the metal detector and also suspend the signal transmission of the transmitting coil so that the detection coil can receive pure external interference signals;

[0035] One or more auxiliary coils can be added to S2 to serve as interference suppression coils. By setting multiple suppression coils in the probe coil system, real-time cancellation of external interference signal components at multiple frequencies can be achieved simultaneously.

[0036] When detecting external interference signals in S3, the signal components of the external interference signals at the frequency point of the metal detector's operating frequency are tested first and suppressed, which can largely eliminate the problem of equipment being interfered with. After that, detection can be performed at frequency points near the operating frequency point, or scanning can be performed over the entire frequency band to understand more about the noise distribution of external interference signals. By detecting each frequency point of the external interference signal, information on its main interference components can be obtained.

[0037] It also includes: after the cancellation signal is injected, the system should continuously monitor the output signal of the detection coil to evaluate the interference suppression effect. If the interference signal is still not completely eliminated, the system can automatically adjust the parameters of the cancellation signal (such as amplitude, phase or frequency) until the best suppression effect is achieved;

[0038] During the operation of the system, the interference detection and suppression strategy is dynamically adjusted to adapt to changes in the external environment. After confirming that the external interference is effectively suppressed, it switches back to the normal detection mode and resumes the signal transmission of the transmitting coil.

[0039] In S3, the amplitude and phase of the signal component of a specific frequency point in the external interference signal are obtained through the signal restoration module, and the signal of the frequency point is restored. Specifically, the received interference signal is transmitted to the signal restoration module for processing. The signal restoration module analyzes the interference signal in the frequency domain through algorithms such as fast Fourier transform (FFT), identifies the main interference frequency points and their corresponding signal components, and quantizes the identified signal components of the specific frequency points, including their amplitude and phase information. Using this information, the signal restoration module can restore the interference signal waveform of the frequency point.

[0040] The restored signal obtained in S4 is injected into the interference suppression coil in a manner of being equal to or opposite to the original signal in phase, so as to offset the signal component of the external interference signal at a specific frequency point. Specifically, a cancellation signal of equal to or opposite to the original interference signal is generated according to the restored interference signal waveform. The cancellation signal has the same amplitude as the original interference signal, but is completely opposite in phase. The generated cancellation signal is injected into the probe area through the transmitting coil (if the transmitting coil is not used for other purposes) or the additional auxiliary interference suppression coil. Since the cancellation signal and the original interference signal meet and overlap in space, they will offset each other, thereby eliminating or significantly reducing the influence of the external interference signal on the metal detector.

[0041] A metal detector external interference suppression system is designed to implement a metal detector external interference suppression method, including:

[0042] The probe coil system includes a receiving coil and a transmitting coil or multiple sets of auxiliary coils are added as detection coils and interference suppression coils;

[0043] The signal recovery module is used to process the received interference signal and generate a cancellation signal; the principle description block diagram of the signal recovery module is as follows Figure 3 As shown in the figure: the interference signal is restored by the restoration module to obtain the suppression signal. The suppression signal maintains the same magnitude as the specific frequency component in the interference signal, which can offset the influence of the interference signal at the frequency point. If the frequency component in the interference signal changes, Dx and Dy will also change accordingly, and the suppression signal will also change, so that the suppression signal follows the interference signal, realizing real-time cancellation of the external interference signal.

[0044] A control module for switching detection / suppression modes and managing the signal output of the transmitting coil;

[0045] At least one power supply and necessary circuit components to support normal operation of the system.

[0046] The control module specifically connects multiple groups of coils in the probe coil system to an electronic network, and realizes dynamic adjustment of the coil load by controlling the resistance and capacitance. After confirming that the external interference is effectively suppressed, the system can automatically switch back to normal detection mode, restore the signal transmission of the transmitting coil, and continue metal detection.

[0047] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing external interference of a metal detector. Features: The following steps are involved: S1: Use the receiving coil in the probe coil system as a detection coil for external interference; S2: Use the transmitting coil in the probe coil system as an interference suppression coil; S3: When the metal detector is working, it receives the external interference signal through the detection coil, and then obtains the amplitude and phase of the signal component of a specific frequency point in the external interference signal through the signal recovery module, and recovers the signal of the frequency point; S4: Injecting the restored signal obtained in the above step S3 into the interference suppression coil in a manner of being equal to or opposite to the original signal, so as to offset the signal component of the external interference signal at a specific frequency point.

2. A method for suppressing external interference of a metal detector according to claim 1, Features: In the above S1, a set of auxiliary coils can be added to serve as detection coils, so that normal detection of the metal detector does not need to be stopped when detecting interference; One or more auxiliary coils can be added to S2 to serve as interference suppression coils. By arranging multiple suppression coils in the probe coil system, real-time cancellation of external interference signal components at multiple frequencies can be achieved simultaneously.

3. A method for suppressing external interference of a metal detector according to claim 2, Features: When detecting the external interference signal in S3, the signal component of the external interference signal at the frequency point of the metal detector working frequency is tested first and suppressed, which can eliminate the problem of equipment being interfered with to a large extent. After that, detection can also be performed at the frequency point near the working frequency point, or scanning can be performed on the entire frequency band to understand more about the noise distribution of the external interference signal.

4. A method for suppressing external interference of a metal detector according to claim 3, Features: Also includes: After the offset signal is injected, the system should continuously monitor the output signal of the detection coil to evaluate the interference suppression effect. If the interference signal is still not completely eliminated, the system can automatically adjust the parameters of the offset signal until the best suppression effect is achieved; During the operation of the system, the interference detection and suppression strategy is dynamically adjusted to adapt to changes in the external environment. After confirming that the external interference is effectively suppressed, it switches back to the normal detection mode and resumes the signal transmission of the transmitting coil.

5. A method for suppressing external interference of a metal detector according to claim 4, Features: In the S3, the amplitude and phase of the signal component of a specific frequency point in the external interference signal are obtained through the signal restoration module, and the signal of the frequency point is restored, which specifically includes: transmitting the received interference signal to the signal restoration module for processing, the signal restoration module analyzes the interference signal in the frequency domain through algorithms such as fast Fourier transform (FFT), identifies the main interference frequency points and their corresponding signal components, and quantizes the identified signal components of the specific frequency point, including their amplitude and phase information. Using this information, the signal restoration module can restore the interference signal waveform of the frequency point.

6. A method for suppressing external interference of a metal detector according to claim 5, Features: The restored signal obtained in S4 is injected into the interference suppression coil in a manner of being in opposite phase with the original signal to offset the signal component of the external interference signal at a specific frequency point. Specifically, the method includes: generating a cancellation signal in opposite phase with the original interference signal according to the restored interference signal waveform. The cancellation signal has the same amplitude as the original interference signal but a completely opposite phase. The generated cancellation signal is injected into the probe area through the transmitting coil or the additional auxiliary interference suppression coil. Since the cancellation signal and the original interference signal meet and overlap in space, they will cancel each other, thereby eliminating or significantly reducing the influence of the external interference signal on the metal detector.

7. A metal detector external interference suppression system, Features: A method for suppressing external interference of a metal detector according to claim 6, comprising: The probe coil system includes a receiving coil and a transmitting coil or multiple sets of auxiliary coils are added as detection coils and interference suppression coils; A signal recovery module, used to process the received interference signal and generate a cancellation signal; A control module for switching detection / suppression modes and managing the signal output of the transmitting coil; At least one power supply and necessary circuit components to support normal operation of the system.

8. A metal detector external interference suppression system according to claim 7, Features: The control module specifically connects multiple groups of coils in the probe coil system to an electronic network, and realizes dynamic adjustment of the coil load by controlling the resistance and capacitance.

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