Underwater radiation-resistant magnetic induction positioning and communication device and signal processing method

Abstract

Underwater radiation-resistant magnetic induction positioning and communication device and signal processing method. S1. Place the receiving and transmitting coils in water. The hardware circuits of the transmitting end and the receiving end are respectively connected to the upper computer and the lower computer through serial ports, and the device is started. S2. Generate a 100 kHz high-frequency sine wave through the DDS module, and use the serial port signal to control the analog switch to modulate the signal and switch between the two working modes of communication and positioning. S3. Control the signal selection module to select different signal transmission links. After being amplified by two-stage operational amplifiers and a high-frequency transformer, an alternating magnetic field is generated in space. S5. The receiving coil converts the alternating magnetic field in space into a voltage signal, and shifts the original 100 kHz signal to 455 kHz for filtering by means of spectrum shifting. S6. Use a single-chip microcomputer to cooperate with a programmable amplifier to amplify the signal. S7. Control the sampling frequency, and restore the original signal by using the spectrum aliasing phenomenon caused by undersampling. The system of the present invention can operate stably in the spent fuel pool environment.

Description

Technical Field

[0001] The present invention belongs to the field of underwater wireless positioning and communication devices, and specifically relates to an underwater radiation-resistant magnetic induction positioning and communication device and a signal processing method. Background Art

[0002] Underwater robots are widely used in fields such as ocean exploration and offshore salvage. In addition, underwater robots can also be used for the daily inspection and emergency maintenance tasks of the spent fuel pool in nuclear power plants. Traditional cable-connected underwater robots are prone to cable entanglement in the spent fuel pool, which affects the safe production of nuclear power. Therefore, wireless positioning and communication technology is the best choice for underwater robots to be used in the spent fuel pool.

[0003] In the positioning and communication of underwater robots, common underwater wireless positioning and communication technologies include: underwater acoustic positioning and communication technology, underwater optical positioning and communication technology, and underwater electromagnetic wave positioning and communication technology. Among them, underwater acoustic positioning and communication technology and optical positioning and communication technology need to expose some sensors to the environment with high temperature, high humidity, and strong nuclear radiation in the spent fuel pool. The sensor life is very short and the robustness is low. Also, because the spent fuel pool is surrounded by concrete and has a small volume, the underwater electromagnetic wave positioning and communication technology is easily affected by the multipath effect in this environment, resulting in low positioning accuracy and difficult to guarantee communication quality. While underwater magnetic induction positioning and communication technology can make up for these shortcomings and complete positioning and communication work in the environment of high temperature, high humidity, and strong radiation in the spent fuel pool.

[0004] Currently, in the research field of underwater magnetic induction positioning technology, since high-frequency signals will increase the coil impedance and exacerbate the eddy current loss, resulting in a decrease in the magnetic field strength and a reduction in the positioning and communication distance; while the bit rate of low-frequency signals is relatively low, the communication real-time performance is poor, and low frequency cannot meet the positioning and communication requirements between underwater robots and base stations. Although there is certain research on underwater magnetic induction positioning and communication technology currently, the positioning and transmission distance is relatively short, and the research on integrating the two is relatively scarce.

[0005] Technical comparison with the paper "Research on a Radiation-Resistant Underwater Robot Positioning System Based on Three-Dimensional Electromagnetic Coils":

[0006] 1. The amplifier circuit at the transmitting end in the paper uses a combination of a first-stage power amplifier and a high-frequency transformer. While we use a combination of a first-stage operational amplifier, an inverter, a second-stage operational amplifier, and a high-frequency transformer, and the second-stage operational amplifier is built into a differential amplifier circuit.

[0007] 2. The transmitting-end circuit in the paper uses a multiplier for modulation and then selects the mode through an analog switch. While we directly use an analog switch to complete the work of modulation and mode selection.

[0008] III. The receiving end in the paper uses a combination of a first-stage amplifier and a programmable amplifier, without performing frequency-domain processing on the signal. However, we have performed frequency-domain processing on the signal through spectral shifting and spectral aliasing, improving the signal quality.

[0009] IV. The paper does not include the gain change logic of the programmable amplifier.

[0010] V. The paper does not include the anti-radiation structure design for the transmitter and receiver circuits. Summary of the Invention

[0011] To solve the above technical problems, the present invention proposes an underwater radiation-resistant magnetic induction positioning and communication device and a signal processing method. For the transmitter, the present invention uses the method of serial port + analog switch to achieve the combination of magnetic induction positioning technology and magnetic induction communication technology with low cost and high availability. At the same time, the signal amplification circuit is optimized. Considering the characteristics of high impedance and low power consumption of the magnetic induction coil, through first-stage amplification, signal inversion, second-stage differential amplification, and third-stage high-frequency transformer amplification, the peak-to-peak voltage of the transmitter reaches more than 240V, effectively increasing the magnetic field strength generated by the transmitting coil. For the receiving end, due to severe noise interference near 100kHz and difficulty in filtering, the present invention uses spectral shifting technology to shift the original signal to 455kHz, uses a ceramic filter with a very narrow passband to filter out the noise, and through a single-chip microcomputer cooperating with a programmable amplifier, the signal is amplified in two stages, making full use of the 0~3.3V sampling interval to improve the sampling accuracy. Finally, by controlling the sampling frequency of the single-chip microcomputer ADC, the original signal of 100kHz is restored using the spectral aliasing phenomenon caused by undersampling and transmitted to the lower computer to achieve relative position calculation and communication functions. The entire system can achieve full coverage within a distance of 5m, decimeter-level positioning, and communicate at a baud rate of 9600bit / s. Since the control systems of the underwater magnetic induction positioning and communication devices are all installed in a shielding box made of metal lead, only the three-dimensional magnetic induction coil needs to be exposed to the high-temperature, high-humidity, and strong-radiation environment of spent fuel. The coil is wound with ordinary enameled wire and is little affected by temperature, humidity, and nuclear radiation. Therefore, it can operate stably for a long time in the environment of a spent fuel pool.

[0012] To achieve the above object, the technical solution adopted by the present invention is:

[0013] The underwater radiation-resistant magnetic induction positioning and communication device is divided into two parts: the receiving end and the transmitting end.

[0014] The transmitting end part includes a transmitting end single-chip microcomputer, a waveform generating circuit, an analog switch, a signal gating circuit, a two-stage operational amplifier, a high-frequency transformer, and a three-dimensional transmitting coil. The three-dimensional transmitting coil is wound in three mutually orthogonal circular wire grooves. Except for the three-dimensional transmitting coil, all circuits are integrated on a circuit board and fixed inside a cuboid radiation shielding box by screws. The host computer is connected to the transmitting end single-chip microcomputer through a USB-to-TTL module. The three-dimensional transmitting coil is connected to the transmitting end circuit board through a 2P wire-to-board connector with a pin pitch of 3.96 mm;

[0015] The receiving end part includes a three-dimensional receiving coil, an operational amplifier, an analog multiplier, a ceramic filter, a programmable amplifier, and a receiving end single-chip microcomputer. The three-dimensional receiving coil is wound in three mutually orthogonal circular wire grooves. Except for the three-dimensional receiving coil, all circuits are integrated on a circuit board and fixed inside a cuboid radiation shielding box by screws. The slave computer is connected to the receiving end single-chip microcomputer through a USB-to-TTL module. The three-dimensional receiving coil is connected to the receiving end circuit board through a 2P wire-to-board connector with a pin pitch of 3.96 mm.

[0016] As a further improvement of the present invention, the analog switch is controlled by a serial port signal to modulate the transmitting end signal and switch between two working modes of communication and positioning.

[0017] As a further improvement of the present invention, the two-stage operational amplifier and the high-frequency transformer form a transmitting end amplification circuit. The transmitting end amplification circuit consists of operational amplifiers of two models, TL082IDR and AD8016AREZ, and their peripheral circuits; TL082IDR has two built-in operational amplifiers. One operational amplifier is used for the first-stage amplification of the signal, and the other operational amplifier inverts the amplified signal to obtain a set of differentially amplified signals after the first-stage amplification; using the two built-in operational amplifiers of AD8016AREZ, a differential amplification circuit is built to achieve the second-stage amplification of the signal; through a high-frequency transformer with a turns ratio of 1:10 for boosting, the third-stage amplification is achieved, and finally the signal is transmitted through the coil.

[0018] As a further improvement of the present invention, the operational amplifier, analog multiplier, ceramic filter, and programmable amplifier form the receiving-end circuit, and the receiving-end circuit consists of an OPA356AIDBVR operational amplifier, an AD835 analog multiplier, an LTM455HW ceramic filter, an LTC6910-2HTS8#TRMPBF programmable amplifier, and its peripheral circuits; the OPA356AIDBVR operational amplifier completes the first-stage amplification of the signal; the AD835 analog multiplier is used to shift the 100 kHz signal to 455 kHz and then filter it through the LTM455HW ceramic filter; by controlling the amplification factor of the LTC6910-2HTS8#TRMPBF programmable amplifier and adding a 1.65 V DC bias to the received AC signal, the voltage signal after the second-stage amplification makes full use of the 0~3.3 V sampling interval; finally, by controlling the sampling frequency of the single-chip microcomputer ADC, the high-frequency signal is undersampled to restore the original signal, and is transmitted to the lower computer for relative position calculation and signal demodulation processing.

[0019] As a further improvement of the present invention, the rectangular shielding boxes equipped with the receiving-end circuit and the transmitting-end circuit are both made of metallic lead.

[0020] The present invention provides a signal processing method for an underwater radiation-resistant magnetic induction positioning communication device, including the following steps:

[0021] (1) Shift the original signal with a frequency of 100 kHz from high frequency through a multiplier. Let the original signal frequency be , and the given signal frequency be , then the frequency of the shifted signal is:

[0022]

[0023] (2) Due to the symmetry of the spectrum, both frequencies in formula (1) are acceptable. Use the characteristic of the narrow passband of the LTM455HW ceramic filter to filter the signal generated in step (1), and one of the frequencies;

[0024] (3) By judging the positive and negative of the maximum value of the induced electromotive force of the receiving coil after amplification sampled by the ADC in the previous sampling period T-1 and its derivative , determine the gain multiple Kpa of the programmable amplifier in the next sampling period T. The judgment logic is as follows:

[0025]

[0026] After pre-amplification, the signal is sampled by the ADC of the single-chip microcomputer. Since the serial data transmission protocol is NRZ code (non-return-to-zero coding), when the bit rate of the signal is the level inversion frequency is at most According to the Shannon sampling theorem, the sampling frequency should at least meet:

[0027]

[0028] Also, because when the sampling frequency can be divided evenly by the fundamental frequency undersampling will not be able to restore the original information. Therefore, the sampling frequency also needs to meet:

[0029]

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The present invention proposes an underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing. For the transmitting end, the present invention uses the method of serial port + analog switch to achieve the combination of magnetic induction positioning technology and magnetic induction communication technology with low cost and high availability. At the same time, the signal amplification circuit is optimized. Considering the characteristics of high impedance and low power consumption of the magnetic induction coil, through first-stage amplification, signal inversion, second-stage differential amplification, and third-stage high-frequency transformer amplification, the peak-to-peak voltage of the transmitting end reaches more than 240V, effectively improving the magnetic field strength generated by the transmitting coil. For the receiving end, since the noise interference is serious near 100kHz and it is not easy to filter, the present invention uses the spectrum shifting technology to shift the original signal to 455kHz, uses a ceramic filter with a very narrow passband to filter the noise, and through the single-chip microcomputer cooperating with the programmable amplifier, the signal is amplified twice to make full use of the sampling interval of 0~3.3V and improve the sampling accuracy. Finally, by controlling the sampling frequency of the single-chip microcomputer ADC, the original signal of 100kHz is restored by using the spectrum aliasing phenomenon caused by undersampling and transmitted to the lower computer to realize the relative position calculation and communication function. The entire system can achieve full coverage within a distance of 5m, decimeter-level positioning, and communicate at a baud rate of 9600bit / s. Since the control systems of the underwater magnetic induction positioning and communication device are all installed in a shielding box made of metal lead, only the three-dimensional magnetic induction coil needs to be exposed to the high-temperature, high-humidity, and strong-radiation environment of spent fuel. And the coil is wound with ordinary enameled wire and is little affected by temperature, humidity, and nuclear radiation. Therefore, it can operate stably for a long time in the environment of the spent fuel pool. Description of the Drawings

[0032] Figure 1 is a schematic diagram of an embodiment of the radiation-resistant underwater positioning and communication device based on a three-dimensional magnetic induction coil according to the present invention;

[0033] Figure 2 is a schematic diagram of the signal link at the transmitting end of the underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing according to the present invention;

[0034] Figure 3 is a schematic diagram of the signal link at the receiving end of the underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing according to the present invention;

[0035] Figure 4 is a partial design drawing 1 of the underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing according to the present invention;

[0036] Figure 5 is a partial design drawing 2 of the underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing according to the present invention;

[0037] Figure 6 is a partial design drawing 3 of the underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing according to the present invention;

[0038] Figure 7 is the overall assembly drawing of the underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing according to the present invention;

[0039] Figure 8 is a flowchart of the signal processing method of the underwater radiation-resistant magnetic induction positioning and communication device based on spectrum shifting and spectrum aliasing according to the present invention;

[0040] Component description:

[0041] 1. Transmitting end control part; 2. DDS and analog switch; 3. Three-way selection switch; 4. First-stage amplification circuit at the transmitting end; 5. Inverter; 6. Differential amplification circuit; 7. High-frequency transformer; 8. First-stage amplification circuit at the receiving end; 9. Spectrum shifting and filtering circuit; 10. Gain self-adjusting circuit; 11. Receiving end control part; 12. Three-dimensional transmitting and receiving coil; 13. Metal lead shielding box; 14. Serial port interface; 15. Type-c power supply interface; 16. Screw hole positions for connecting the shielding box and the cover plate; 17. Screw hole positions for fixing the circuit board; 18. Wire-to-board connector; 19. Metal lead shielding box cover plate; 20. Screw hole positions for connecting the shielding box and the cover plate; 21. Main control circuit at the transmitting end; 22. Main control circuit at the receiving end. Detailed implementation manners

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners:

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the exemplified embodiments do not limit the present invention.

[0044] The present invention is an underwater radiation-resistant magnetic induction positioning and communication device;

[0045] (1) An underwater positioning and communication device based on a three-dimensional magnetic induction coil

[0046] An underwater positioning and communication device based on a three-dimensional magnetic induction coil, the circuit structure of its transmitting end is mainly as follows Figure 1 shown, there are a control part 1, a DDS and an analog switch 2, a three-way gating switch 3, a first-stage amplifier circuit 4, an inverter 5, a differential amplifier circuit 6, a high-frequency transformer 7, and three groups of coils wound in a three-dimensional orthogonal coil slot 12, etc. The single-chip microcomputer is connected to the upper computer in the form of USB to TTL to form the control part, and the high-frequency transformer is connected to the coil through a 2P wire-to-board connector with a pin pitch of 3.96 mm. The circuit structure of the receiving end is mainly as follows Figure 3 shown, there are three groups of coils wound in a three-dimensional orthogonal coil slot 12, a first-stage amplifier circuit 8, a spectrum shifting and filtering circuit 9, a programmable amplifier circuit 10, a control part 11, etc. The single-chip microcomputer is connected to the lower computer in the form of USB to TTL to form the control part, and the input end of the first-stage amplifier circuit is connected to the coil through a 2P wire-to-board connector with a pin pitch of 3.96 mm.

[0047] The partial schematic diagram is as follows Figures 4-6 shown. The circuit of the transmitting end and the receiving end of the present invention can both be installed in a shielding box 13 made of metallic lead. The circuit board is installed at the bottom of the shielding box 13 through self-tapping screws and screw holes 17; the upper computer and the lower computer are connected to the circuit through through holes 14, and the circuit is connected to the Type-c interface through through holes 15 for power supply; the three signal lines of the transmitting end and the receiving end are connected to the coil through through holes 18; the shielding box cover can be fixed on the top of the shielding box through self-tapping screws and screw holes 16 and 20. The assembly of the entire system is as follows Figure 7 shown, 21 is the transmitting-end circuit, and 22 is the receiving-end circuit.

[0048] Place the receiving and transmitting coils in water. The hardware circuits of the transmitting end and the receiving end are respectively connected to the upper computer and the lower computer through the serial port, and the device is started. Control the DDS module to generate a high-frequency sine wave of 100 kHz through the SPI communication protocol, and use the serial port signal to control the analog switch to modulate the signal and switch between the two working modes of communication and positioning. The control signal gating module selects different signal transmission links. After being amplified by two-stage operational amplifiers and a high-frequency transformer, the three coils sequentially and time-divisionally transmit signals, generating an alternating magnetic field in space. The receiving coil converts the alternating magnetic field in space into a voltage signal, amplifies the signal by one stage, and then uses a analog multiplier to shift the original signal of 100 kHz to 455 kHz and filter it with a ceramic filter with a narrow passband. Use a single-chip microcomputer to cooperate with a programmable amplifier to amplify the signal, making full use of the sampling interval of 0~3.3V. Control the ADC sampling frequency through the single-chip microcomputer timer, use the phenomenon of spectral aliasing to restore the original signal of 100 kHz, and transmit the sampled data to the lower computer through the serial port for relative position calculation and signal demodulation processing.

[0049] The signal processing method at the receiving end is as Figure 8 shown and is specifically explained as follows:

[0050] (1) Shift the original signal with a frequency of 100 kHz from high frequency through a multiplier. Let the original signal frequency be , and the given signal frequency be , then the frequency of the shifted signal is:

[0051]

[0052] (2) Due to the symmetry of the spectrum, both of the two frequencies in formula (1) are acceptable. The signal generated in step (1) can be filtered using the characteristic of the narrow passband of the LTM455HW ceramic filter, and one of the frequencies can be selected.

[0053] (3) By judging the positive and negative of the maximum value of the induced electromotive force of the receiving coil after amplification sampled by the ADC in the previous sampling period T-1 and its derivative , determine the gain multiple Kpa of the programmable amplifier in the next sampling period T. The judgment logic is as follows:

[0054]

[0055] (4) After pre-amplification, the signal is sampled by the ADC of the single-chip microcomputer. Since the serial port data transmission protocol is NRZ code (non-return-to-zero coding), when the bit rate of the signal is When its level inversion frequency is up to , according to the Shannon sampling theorem, the sampling frequency shall at least meet the requirement:

[0056]

[0057] Also, because when the sampling frequency can be divided evenly by the fundamental frequency , undersampling will not be able to restore the original information. Therefore, the sampling frequency shall also meet the requirement:

[0058]

[0059] The above are only the preferred embodiments of the present invention, and do not constitute any other form of limitation to the present invention. Any modification or equivalent change made according to the technical essence of the present invention still falls within the scope protected by the present invention.

Claims

1. The underwater radiation-resistant magnetic induction positioning and communication device is divided into a receiving end and a transmitting end, and is characterized in that: The transmitting end part includes a transmitting end single-chip microcomputer, a waveform generating circuit, an analog switch, a signal gating circuit, a two-stage operational amplifier, a high-frequency transformer and a three-dimensional transmitting coil. The three-dimensional transmitting coil is wound in three mutually orthogonal circular wire grooves. Except for the three-dimensional transmitting coil, all circuits are integrated on a circuit board and fixed inside a cuboid radiation shielding box by screws. The host computer is connected to the transmitting end single-chip microcomputer through a USB to TTL module. The three-dimensional transmitting coil is connected to the transmitting end circuit board through a 2P wire-to-board connector with a pin pitch of 3.96 mm. The receiving end part includes a three-dimensional receiving coil, an operational amplifier, a analog multiplier, a ceramic filter, a programmable amplifier and a receiving end single-chip microcomputer. The three-dimensional receiving coil is wound in three mutually orthogonal circular wire grooves. Except for the three-dimensional receiving coil, all circuits are integrated on a circuit board and fixed inside a cuboid radiation shielding box by screws. The slave computer is connected to the receiving end single-chip microcomputer through a USB to TTL module. The three-dimensional receiving coil is connected to the receiving end circuit board through a 2P wire-to-board connector with a pin pitch of 3.96 mm. The signal processing method of the receiving end part includes the following steps: (1) The original signal with a frequency of 100 kHz is shifted from a high frequency by a multiplier. Let the original signal frequency be , and the given signal frequency be . Then the frequency of the shifted signal is: ； (2) Due to the symmetry of the spectrum, both frequencies in formula (1) are acceptable. Use the characteristic of the narrow passband of the LTM455HW ceramic filter to filter the signal generated in step (1) and select one of the frequencies. (3) By judging the maximum value of the amplified induced electromotive force of the receiving coil obtained by ADC sampling in the previous sampling period T-1 and its derivative to determine the gain multiple Kpa of the programmable amplifier in the next sampling period T. The judgment logic is as follows: ； (4) After pre-amplification, the signal is sampled by the ADC of the single-chip microcomputer. Since the serial data transmission protocol is NRZ code (non-return-to-zero coding), when the bit rate of the signal is its level inversion frequency is at most , according to the Shannon sampling theorem, the sampling frequency should at least satisfy: ； Also, since when the sampling frequency is divisible by the fundamental frequency undersampling will not be able to restore the original information. Therefore, the sampling frequency also needs to satisfy: 。 2. The underwater radiation-resistant magnetic induction positioning and communication device according to claim 1, wherein: The analog switch is controlled by a serial port signal to modulate the transmitting end signal and switch between the two working modes of communication and positioning.

3. The underwater radiation-resistant magnetic induction positioning and communication device according to claim 1, characterized in that: The two-stage operational amplifier and the high-frequency transformer form a transmitting end amplification circuit. The transmitting end amplification circuit consists of operational amplifiers of two models, TL082IDR and AD8016AREZ, and their peripheral circuits. TL082IDR has two built-in operational amplifiers. One operational amplifier is used for the first-stage amplification of the signal, and the other operational amplifier inverts the amplified signal to obtain a set of differentially amplified signals after the first-stage amplification. Use the two built-in operational amplifiers of AD8016AREZ to build a differential amplification circuit to achieve the second-stage amplification of the signal. Through a high-frequency transformer with a turns ratio of 1:10 for voltage boosting, the third-stage amplification is achieved, and finally the signal is transmitted through the coil.

4. The underwater radiation-resistant magnetic induction positioning and communication device according to claim 1, characterized in that: The operational amplifier, analog multiplier, ceramic filter and programmable amplifier constitute the receiving-end circuit. The receiving-end circuit consists of an OPA356AIDBVR operational amplifier, an AD835 analog multiplier, an LTM455HW ceramic filter, an LTC6910-2HTS8#TRMPBF programmable amplifier and its peripheral circuits. The OPA356AIDBVR operational amplifier completes the first-stage amplification of the signal. The AD835 analog multiplier is used to shift the 100 kHz signal to 455 kHz and then filter it through the LTM455HW ceramic filter. By controlling the amplification factor of the LTC6910-2HTS8#TRMPBF programmable amplifier and adding a 1.65 V DC bias to the received AC signal, the voltage signal after the second-stage amplification makes full use of the 0~3.3 V sampling interval. Finally, by controlling the sampling frequency of the single-chip microcomputer ADC, the high-frequency signal is undersampled to restore the original signal, and then transmitted to the lower computer for relative position calculation and signal demodulation processing.

5. The underwater radiation-resistant magnetic induction positioning and communication device according to claim 1, characterized in that: The cuboid shielding boxes equipped with the receiving-end circuit and the transmitting-end circuit are both made of metallic lead.

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