Underwater towed geomagnetic measurement system and data time service method

Abstract

The invention discloses an underwater towed geomagnetic measurement system and a data timing method, and belongs to the field of underwater geomagnetic detection. The system comprises a towing boat, a monitoring control unit and a geomagnetic measurement device, the monitoring control unit is arranged on the towing boat, and the geomagnetic measurement device is connected with the monitoring control unit through a photoelectric composite cable. The monitoring control unit comprises a monitoring computer, a first GNSS antenna, a GNSS taming clock module, a first photoelectric conversion module, a first ultra-short baseline positioning beacon and a shipborne power supply. The geomagnetic measurement device comprises a magnetometer, a second photoelectric conversion module, a controller, inertial navigation equipment, a second GNSS antenna, a depth meter, a Doppler log, a second ultra-short baseline positioning beacon and a power conversion module. According to the underwater towed geomagnetic measurement system and the data timing method provided by the invention, high-precision geomagnetic measurement data can be obtained, accurate timing can be carried out on the geomagnetic measurement data, and the reliability is high.

Description

Technical Field

[0001] The invention belongs to the field of underwater geomagnetic detection, and in particular relates to an underwater towed geomagnetic measurement system and a data timing method. Background Art

[0002] When a traditional towed marine magnetometer is measuring, the position of the magnetometer is calculated by the position of the towing ship, the length of the towing cable and the depth information of the magnetometer, and there is a certain error in the position calculation. In addition, since geomagnetic measurement requires post-processing and compensation for geomagnetic quiet diurnal changes and carrier interference, the underwater towed geomagnetic measurement system does not directly process the output data of the sensor device, but receives the data through the controller in the underwater towed geomagnetic measurement platform, and then repackages the time information and equipment data and sends it to the ship-borne monitoring control unit for display and data storage. Since there is a certain time delay from the output of the sensor device to the reception of the controller and the completion of data analysis, there is also a time delay from the input of the magnetometer probe to the output of the magnetometer acquisition unit. These time delays will cause deviations in the position information and time information of the underwater geomagnetic measurement data. Summary of the invention

[0003] In view of the deficiencies existing in the related art, the purpose of the present invention is to provide an underwater towed geomagnetic measurement system and a data timing method to solve the technical problem that the underwater towed geomagnetic measurement system cannot accurately time the measurement data.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] An underwater towed geomagnetic measurement system, comprising:

[0006] Towing boats;

[0007] The monitoring control unit is arranged on the towing vessel and includes:

[0008] Monitor computers;

[0009] A first GNSS antenna, the first GNSS antenna is used to receive GNSS signals;

[0010] The GNSS taming clock module is electrically connected to the first GNSS antenna, and the GNSS taming clock module is electrically connected to the monitoring computer. The GNSS taming clock module is used to parse the GNSS signal to obtain satellite positioning, time and status information and send it to the monitoring computer.

[0011] The taming clock module is also used to output 1PPS signal and 10MHz signal;

[0012] A first photoelectric conversion module, the first photoelectric conversion module is electrically connected to the GNSS disciplined clock module, and the first photoelectric conversion module is used to convert a 1PPS signal and a 10MHz signal into an optical signal;

[0013] The first ultra-short baseline positioning beacon is connected to the monitoring computer through

[0014] The first photoelectric conversion switch is connected;

[0015] Onboard power supply, which is used to provide working power for the monitoring control unit;

[0016] The geomagnetic measuring device is connected to the monitoring control unit through an optoelectronic composite cable. The geomagnetic measuring device includes:

[0017] Magnetometer: Magnetometer is used to collect geomagnetic data;

[0018] A second photoelectric conversion module, the second photoelectric conversion module is connected to the first photoelectric conversion module to convert the 1PPS signal and the 10MHz signal into an electrical signal;

[0019] A controller, the controller is connected to the magnetometer to obtain geomagnetic data, the controller is connected to the second photoelectric conversion module to receive 1PPS signal and 10MHz signal to generate time information, and the controller is connected to the monitoring computer through the second photoelectric conversion switch;

[0021] An inertial navigation device is connected to the controller, and is used to measure the position and attitude of the geomagnetic measuring device;

[0023] a second GNSS antenna, the second GNSS antenna being connected to an inertial navigation device so that the inertial navigation device acquires an initial position and attitude of the geomagnetic measurement device;

[0025] A depth gauge is connected to the controller and is used to measure the depth of the geomagnetic measuring device;

[0027] A Doppler speed meter, which is connected to the controller and is used to measure the speed of the geomagnetic measuring device;

[0029] A second ultra-short baseline positioning beacon, the second ultra-short baseline positioning beacon is connected to the controller, and the second ultra-short baseline positioning beacon is connected to the first ultra-short baseline positioning beacon by hydroacoustic communication to locate the position of the geomagnetic measurement device at a low frequency;

[0031] A power conversion module is connected to the shipboard power supply to provide working power for the geomagnetic measuring device.

[0032] In some embodiments, the controller includes a time information generating unit, and the time information generating unit includes:

[0033] Network communication module, which is used to obtain GNSS time information, including "GNSS year-month-day" and "GNSS hour-minute-second";

[0034] Phase-locked loop: The phase-locked loop uses the 10MHz signal as a reference clock to generate a 100MHz system clock that is in phase with the reference clock.

[0035] A time counter, which is connected to the network communication module to obtain "GNSS hour-minute-second" information to generate "hour-minute-second-millisecond" time information and a cross-day signal;

[0036] Calendar module, the calendar module is connected with the network communication module to obtain "GNSS year-month-day" information, the calendar module is connected with the time counter to obtain cross-day signals, and the calendar module is used to generate "year-month-day" time information;

[0037] 1PPS delay correction module, the 1PPS delay correction module is connected with the time counter and calendar module to obtain "year-month-day-hour-minute-second-millisecond" time information and perform transmission and conversion delay correction.

[0038] In some of the embodiments, the underwater towed geomagnetic measurement system also includes a first waterproof and pressure-resistant cabin and a second waterproof and pressure-resistant cabin to carry the geomagnetic measurement device, a towing ring is provided above the center of gravity of the first waterproof and pressure-resistant cabin and the second waterproof and pressure-resistant cabin, and a tail fin is provided at the end of the first waterproof and pressure-resistant cabin near the second waterproof and pressure-resistant cabin.

[0039] In some embodiments, the magnetometer includes a scalar magnetometer and a three-component magnetometer, the scalar magnetometer includes a scalar magnetometer acquisition unit and a scalar magnetometer probe, and the three-component magnetometer includes a three-component magnetometer acquisition unit and a three-component magnetometer probe, wherein the scalar magnetometer unit and the three-component magnetometer unit are arranged in a first waterproof and pressure-resistant cabin, the scalar magnetometer probe and the three-component magnetometer probe are arranged in a second waterproof and pressure-resistant cabin, the three-component magnetometer probe and the first waterproof and pressure-resistant cabin are separated by a first set distance, and the scalar magnetometer probe and the three-component magnetometer probe are separated by a second set distance.

[0040] An underwater towed geomagnetic measurement data timing method, using the above-mentioned underwater towed geomagnetic measurement system, the method comprises the following steps:

[0041] Time information generation step: the GNSS disciplined clock module of the monitoring control unit generates the initial time, 1PPS signal and 10MHz signal, and sends them to the controller through the first photoelectric conversion module, the photoelectric composite cable and the second photoelectric conversion module, and the time information generation unit of the controller generates the time information;

[0042] Steps for preliminary timing of sensor device data: The sensor equipment includes a second ultra-short baseline positioning beacon, a Doppler odometer, a depth gauge, an inertial navigation device, a scalar magnetometer and a three-component magnetometer. The data output is serial communication. The sensor device data is output in the form of a data frame. The 100MHz system clock is used to parse the serial port data bytes and the bits of each byte to obtain the start bit output time t0 of the start byte of the sensor device data frame. Time t0 is the preliminary timing time of the sensor device data.

[0043] In some of the embodiments, the underwater towed geomagnetic measurement data timing method further includes a magnetometer signal measurement correction step:

[0044] S31, using a scalar magnetometer to select a measurement area where the geomagnetic signal changes slowly, so that the amplitude change of the magnetic field measurement value per minute is no more than 2nT, and placing an ocean magnetic diurnal variation observation station in the measurement area;

[0045] S32, setting position a, position b and position c in sequence with a third set distance as the interval, placing the scalar magnetometer at position c, placing the permanent magnet on the side of the scalar magnetometer away from position b, and adjusting the position of the permanent magnet until the measurement value of the scalar magnetometer is about 95 μT;

[0046] S33, use a magnetometer to measure the magnetic field values ​​at position a, position b and position c in a static state, which are B a , B b and B c ;

[0047] S34, photoelectric switches are respectively provided at position a, position b and position c, an electric winch is placed on the side of the permanent magnet away from position c, a fourth set distance is spaced between the electric winch and the permanent magnet, a non-magnetic slider is connected to the noose of the electric winch, a magnetometer probe is placed on the non-magnetic slider, the electric winch pulls the non-magnetic slider at a set speed at a uniform speed, so that the magnetometer probe passes through position a, position b and position c in a straight line in sequence, when the magnetometer probe passes through position a, position b and position c, the output signal of the photoelectric switch at the corresponding position changes from a low level to a high level, the controller collects the rising edge signal output of the photoelectric switch, and then performs preliminary timing on the magnetometer output data according to the method in the step of preliminary timing of sensor device data and then outputs it;

[0048] S35, draw the time curve of the moment when the photoelectric switch output signal changes from low level to high level and the time curve of the magnetometer measurement data, and obtain the moment when the magnetometer probe reaches position a, position b and position c respectively. 0a ,t 0b and t 0c , the amplitude of the magnetometer measurement value reaches B a , Bb and B c The time points are t 01 ,t 02 and t 03 ;

[0049] S36, assuming that the delay of the magnetometer signal from the magnetometer probe input to the magnetometer acquisition unit output is Δt3, then Δt3=[(t 03 -t 0c )+(t 02 -t 0b )] / 2, assuming that the timing time for correcting the magnetometer data is t4, then t4=t0-Δt3.

[0050] In some embodiments, the magnetometer signal measurement correction step further includes step S37: repeating steps S34 to S36 to obtain multiple Δt3 and taking the average value as Will The delay time from the magnetometer probe input to the magnetometer acquisition unit output of the magnetometer signal.

[0051] In some embodiments, the time information generating step includes:

[0052] S11, waiting for the GNSS disciplined clock module to complete discipline and output stable GNSS timing information;

[0053] S12, the time counter and the calendar module receive GNSS timing information, and the time counter uses the received GNSS timing information as initial time information;

[0054] S13, waiting for the rising edge of the next 1PPS signal, and using it as the start signal of the time counter;

[0055] S14, using the 100MHz system clock as the clock source, each time the clock rises, the time counter counts up by 1, and generates "hour-minute-second-millisecond" time information and a cross-day signal according to the time system relationship;

[0056] S15. When the GNSS signal is stable, the internal "hour-minute-second" is compared and corrected. The calendar module uses the 100MHz system clock as the clock source and generates the "year-month-day" time information according to the cross-day signal generated by the time counter and the calendar system relationship.

[0057] In some embodiments, the time information generating step also includes: S16, the 1PPS delay correction module obtains the "year-month-day-hour-minute-second-millisecond" time information generated by the time counter and the calendar module, and the 1PPS signal output by the GNSS disciplined clock module is received by the controller after passing through the first photoelectric conversion module, the photoelectric composite cable and the second photoelectric conversion module in sequence. The "year-month-day-hour-minute-second-millisecond" time information generated by the time counter and the calendar module is set to T0, the transmission delay of the photoelectric composite cable is set to Δt1, the transmission delay of the first photoelectric conversion module and the second photoelectric conversion module is set to Δt2, and the time information corrected by the 1PPS delay correction module is set to T1, then T1=T0-Δt1-Δt2-Δt2.

[0058] In some embodiments, the step of initially synchronizing sensor device data includes:

[0059] S21, the controller determines the level of the serial port input signal. When in idle state, the input signal is at a high level. When the level changes from a high level to a low level, the start bit of the data is received. The time information of the controller at this time is set to t0;

[0060] S22, after receiving a complete byte, determine whether the byte is the starting byte of the sensor device data frame, if yes, proceed to step S23, if no, return to step S21;

[0061] S23, after receiving the current data frame, determine whether the data of this frame conforms to the data protocol of the device, if yes, proceed to step S24, if no, return to step S21;

[0062] S24, combining the current frame data with the controller's time information t0 into a new data frame, completing the initial data timing, and preparing to receive the next frame data.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] 1. The underwater towed geomagnetic measurement system and data timing method provided by the present invention can obtain high-precision geomagnetic measurement data, and can accurately time the geomagnetic measurement data with high reliability. The system and timing method can accurately measure the changes in the earth's magnetic field, which is of great significance for studying the internal structure of the earth, detecting mineral resources, etc.

[0065] 2. The underwater towed geomagnetic measurement system and data timing method provided by the present invention can perform geomagnetic measurement while the towing ship is sailing, without stopping the ship or slowing down, thereby improving the working efficiency of geomagnetic measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0067] Figure 1 A schematic diagram of the system structure of an embodiment of an underwater towed geomagnetic measurement system and a data timing method of the present invention;

[0068] Figure 2 It is a principle block diagram of a monitoring control unit of an embodiment of an underwater towed geomagnetic measurement system and a data timing method of the present invention;

[0069] Figure 3 It is a principle block diagram of a geomagnetic measurement device of an embodiment of an underwater towed geomagnetic measurement system and a data timing method of the present invention;

[0070] Figure 4 It is a principle block diagram of a time information generating unit of an embodiment of an underwater towed geomagnetic measurement system and a data timing method of the present invention;

[0071] Figure 5 A schematic diagram of serial communication timing and protocol of an embodiment of an underwater towed geomagnetic measurement system and a data timing method of the present invention;

[0072] Figure 6 A flow chart of preliminary timing of sensor device data in one embodiment of an underwater towed geomagnetic measurement system and data timing method of the present invention;

[0073] Figure 7 A schematic diagram of magnetometer signal measurement correction of an embodiment of an underwater towed geomagnetic measurement system and a data timing method of the present invention;

[0074] Figure 8 A schematic diagram of a time curve of the moment when the photoelectric switch output signal changes to a high level and the magnetometer measurement data in one embodiment of the underwater towed geomagnetic measurement system and data timing method of the present invention;

[0075] Fig. 9 The present invention is a data timing flow chart of an underwater towed geomagnetic measurement system and a data timing method according to an embodiment of the present invention.

[0076] In the figure:

[0077] 1. Towing vessel; 2. Monitoring and control unit; 3. First GNSS antenna; 4. Second GNSS antenna; 5. First ultra-short baseline positioning beacon; 6. Second ultra-short baseline positioning beacon; 7. Geomagnetic measuring device; 8. Optoelectronic composite cable; 9. Depth gauge; 10. Doppler log; 11. First waterproof and pressure-resistant cabin; 12. Second waterproof and pressure-resistant cabin; 13. Scalar magnetometer probe; 14. Three-component magnetometer probe; 15. Towing ring; 16. Tail fin; 17. Winch. DETAILED DESCRIPTION

[0078] 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. 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 making creative work are within the scope of protection of the present invention.

[0079] In the description of the present invention, it should be understood that the terms "center", "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0080] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0081] Embodiment 1:

[0082] See attached Figures 1 to 9 , a schematic embodiment of the underwater towed geomagnetic measurement system proposed in the present invention is given, and the underwater towed geomagnetic measurement system includes a towing vessel 1, a monitoring control unit 2 and a geomagnetic measurement device 7.

[0083] See attached Figure 1The monitoring control unit 2 is arranged on the towing vessel 1, and the geomagnetic measuring device 7 is connected to the monitoring control unit 2 through the photoelectric composite cable 8. The towing vessel 1 provides power for the towing measurement of the underwater geomagnetic measuring device 7. In this embodiment, a winch 17 is also provided on the towing vessel 1, and the winch 17 is connected to the photoelectric composite cable 8 to retract and release the photoelectric composite cable 8 and the geomagnetic measuring device 7. The photoelectric composite cable 8 is used to realize power supply and communication of the geomagnetic measuring device 7 on the one hand, and bear the towing tension of the geomagnetic measuring device 7 on the other hand.

[0084] See attached Figure 2 The monitoring control unit 2 includes a monitoring computer, a first GNSS antenna 3, a GNSS discipline clock module, a first photoelectric conversion module, a first photoelectric conversion switch, a first ultra-short baseline positioning beacon 5 and a shipboard power supply. The first GNSS antenna 3 is used to receive GNSS signals, the GNSS discipline clock module is electrically connected to the first GNSS antenna 3, the GNSS discipline clock module is electrically connected to the monitoring computer, the GNSS discipline clock module is used to parse the GNSS signal to obtain satellite positioning, time and status information and send it to the monitoring computer, and the GNSS discipline clock module is also used to output 1PPS signals and 10MHz signals. The first photoelectric conversion module is electrically connected to the GNSS discipline clock module, and the first photoelectric conversion module is used to convert the 1PPS signal and the 10MHz signal into optical signals. The first ultra-short baseline positioning beacon 5 is connected to the monitoring computer through the first photoelectric conversion switch. The shipboard power supply is used to provide working power for the monitoring control unit 2 and the geomagnetic measurement device 7.

[0085] Specifically, the monitoring computer is used to monitor and control the geomagnetic measuring device 7, and receive and store the sensor equipment data uploaded by the geomagnetic measuring device 7. The GNSS taming clock module has a built-in GNSS receiver. The GNSS taming clock module uses the 1PPS signal output by the GNSS receiver to tame its temperature compensated crystal oscillator, and generates a 1PPS signal and a 10MHz signal with the same phase as the 1PPS signal output by the GNSS receiver. The GNSS taming clock module can ensure that when the GNSS signal is poor, a high-precision 1PPS signal and a 10MHz signal are continuously output. On the one hand, the GNSS taming clock module obtains satellite positioning, time and status information through the GNSS receiver, and sends the GNSS receiver information and its own taming status to the monitoring computer through the RS232 serial port. On the other hand, it outputs a 1PPS signal and a 10MHz signal. The first photoelectric conversion module sends the optical signal to the geomagnetic measuring device 7 through the photoelectric composite cable 8. The first photoelectric conversion switch is used for network communication between the monitoring computer, the geomagnetic measuring device 7 and the first ultra-short baseline positioning beacon 5.

[0086] See attached Figure 3The geomagnetic measuring device 7 includes a magnetometer, a second photoelectric conversion module, a second photoelectric conversion switch, a controller, an inertial navigation device, a second GNSS antenna 4, a depth meter 9, a Doppler odometer 10, a second ultra-short baseline positioning beacon 6 and a power conversion module.

[0087] The magnetometer is used to collect geomagnetic data. The second photoelectric conversion module is connected to the first photoelectric conversion module to convert the 1PPS signal and the 10MHz signal into electrical signals. The controller is connected to the magnetometer to obtain geomagnetic data, the controller is connected to the second photoelectric conversion module to receive the 1PPS signal and the 10MHz signal generation time information, and the controller is connected to the monitoring computer through the second photoelectric conversion switch. The inertial navigation device is connected to the controller, and the inertial navigation device is used to measure the position and attitude of the geomagnetic measuring device 7. The second GNSS antenna 4 is connected to the inertial navigation device so that the inertial navigation device obtains the initial position and attitude of the geomagnetic measuring device 7. Specifically, the inertial navigation device obtains the initial position and attitude of the geomagnetic measuring device 7 on the deck. The depth gauge 9 is connected to the controller, and the depth gauge 9 is used to measure the depth of the geomagnetic measuring device 7 during underwater towing measurement. The Doppler speed meter 10 is connected to the controller, and the Doppler speed meter 10 is used to measure the speed of the geomagnetic measuring device 7 during underwater towing measurement. The second ultra-short baseline positioning beacon 6 is connected to the controller, and the second ultra-short baseline positioning beacon 6 is connected to the first ultra-short baseline positioning beacon 5 by hydroacoustic communication to locate the position of the geomagnetic measuring device 7 at a low frequency. The arrangement of the depth meter 9, the Doppler log 10 and the second ultra-short baseline positioning beacon 6 helps to improve the positioning accuracy of the inertial navigation device in the geomagnetic measuring device 7. The power conversion module is connected to the shipboard power supply to provide the geomagnetic measuring device 7 with working power.

[0088] In this embodiment, the controller is designed based on FPGA. On the one hand, it receives 1PPS signals and 10MHz signals to generate accurate time information. On the other hand, it receives measurement data of each sensor device in the geomagnetic measurement device 7, and sends these data to the monitoring computer of the monitoring control unit 2 via Ethernet after timing.

[0089] In order to ensure the safety of geomagnetic measurement, in this embodiment, the underwater towed geomagnetic measurement system also includes a first waterproof and pressure-resistant cabin 11 and a second waterproof and pressure-resistant cabin 12 to carry the geomagnetic measurement device 7. The first waterproof and pressure-resistant cabin 11 includes an outer skin structure, the outer skin material uses polyoxymethylene resin plastic without magnetic interference, and the outer shape is designed to be fish-shaped to reduce water resistance during towing. The waterproof and pressure-resistant cabin fixing structure and water-permeable holes are designed inside the skin. The second waterproof and pressure-resistant cabin 12 is made of fiberglass, which has a low density and high strength, that is, the fiberglass material can ensure strength while having a light weight, which is easy to carry and install.

[0090] A towing ring 15 is provided above the center of gravity of the first waterproof and pressure-resistant cabin 11 and the second waterproof and pressure-resistant cabin 12, and the towing ring 15 is used for hoisting and towing the geomagnetic measuring device 7. A tail 16 is provided at the end of the first waterproof and pressure-resistant cabin 11 close to the second waterproof and pressure-resistant cabin 12. Specifically, there are four tails 16, and the four tails include two fixed wings that are symmetrical in the horizontal direction and two fixed wings that are symmetrical in the upper and lower directions. The left-right symmetrical tail is used to maintain the pitch angle when the geomagnetic measuring device 7 is towed, and the lower symmetrical tail is used to maintain the heading angle when the geomagnetic measuring device 7 is towed, so that the geomagnetic measuring device 7 is always consistent with the towing direction, reducing the influence of water flow in the water.

[0091] In this embodiment, the geomagnetic measuring device further includes a counterweight block and a buoyancy adjusting block, which are used to adjust the center of gravity and the center of buoyancy of the geomagnetic measuring device 7. The gravity of the geomagnetic measuring device 7 in water is greater than the buoyancy, and the center of buoyancy is located directly below the center of gravity, so that the Doppler speed meter 10 of the geomagnetic measuring device 7 remains vertically downward. When the dragging measurement is performed, when the tension, water resistance, buoyancy and gravity of the geomagnetic measuring device 7 are balanced, the geomagnetic measuring device 7 will remain within a certain depth range.

[0092] In order to maintain a stable and reliable connection of the equipment in extreme deep-sea environments, in this embodiment, the geomagnetic measurement device also includes a watertight connector and a cable, which is used to connect the optoelectronic composite cable 8, the second GNSS antenna 4, the second ultra-short baseline positioning beacon 6, the depth meter 9, the Doppler speed meter 10, the first waterproof and pressure-resistant cabin 11, and the second waterproof and pressure-resistant cabin 12, which can resist the erosion of seawater and ensure long-term stable operation.

[0093] See attached Figure 3 The magnetometer includes a scalar magnetometer and a three-component magnetometer. The scalar magnetometer includes a scalar magnetometer acquisition unit and a scalar magnetometer probe 13. The three-component magnetometer includes a three-component magnetometer acquisition unit and a three-component magnetometer probe 14. The scalar magnetometer unit and the three-component magnetometer unit are arranged in the first waterproof and pressure-resistant cabin 11, and the scalar magnetometer probe 13 and the three-component magnetometer probe 14 are arranged in the second waterproof and pressure-resistant cabin 12, for realizing geomagnetic signal measurement. Specifically, the scalar magnetometer acquisition unit acquires the signal of the scalar magnetometer probe 13 and outputs the scalar magnetometer measurement data; the three-component magnetometer acquisition unit acquires the signal of the three-component magnetometer probe 14 and outputs the three-component magnetometer measurement data.

[0094] See attached Figure 1, a first set distance is set between the three-component magnetometer probe 14 and the outer skin structure of the first waterproof and pressure-resistant cabin 11. In this embodiment, the first set distance is 0.8m to reduce the interference of the first waterproof and pressure-resistant cabin 11 and other metal structural parts on the magnetometer. A second set distance is set between the scalar magnetometer probe 13 and the three-component magnetometer probe 14. In this embodiment, the second set distance is 0.3m to reduce the mutual interference between the magnetometer probes.

[0095] The underwater towed geomagnetic measurement system data timing is achieved by the controller receiving the sensor device data, and then repackaging the accurate time information and sensor device data for output. To ensure the accuracy of the controller timing, see the attached Figure 4 In this embodiment, the controller includes a time information generation unit, which includes a network communication module, a phase-locked loop, a time counter, a calendar module and a 1PPS delay correction module. The network communication module is used to obtain GNSS timing time information, specifically, to obtain GNSS timing time information, GNSS receiver information and self-taming status from the monitoring computer of the monitoring control unit 2 through Ethernet. GNSS timing time information includes "GNSS year-month-day" and "GNSS hour-minute-second". The phase-locked loop is used to use the 10MHz signal as a reference clock to generate a 100MHz system clock with the same phase as the reference clock. The time counter is connected to the network communication module to obtain "GNSS hour-minute-second" information to generate "hour-minute-second-millisecond" time information and a cross-day signal. The calendar module is connected to the network communication module to obtain "GNSS year-month-day" information, the calendar module is connected to the time counter to obtain a cross-day signal, and the calendar module is used to generate "year-month-day" time information. Among them, the time information generated by the time counter is a 24-hour system with a millisecond resolution of 10ns. The 1PPS delay correction module is connected to the time counter and calendar module to obtain the "year-month-day-hour-minute-second-millisecond" time information and perform transmission and conversion delay correction.

[0096] In the above-mentioned schematic embodiment, the underwater towed geomagnetic measurement system can obtain high-precision geomagnetic measurement data and can accurately synchronize the geomagnetic measurement data with high reliability. The system can accurately measure the changes in the earth's magnetic field, which is of great significance for studying the internal structure of the earth and detecting mineral resources.

[0097] Embodiment 2:

[0098] This embodiment provides an underwater towed geomagnetic measurement data timing method, using the underwater towed geomagnetic measurement system described in Example 1, and the underwater towed geomagnetic measurement data timing method includes the following steps:

[0099] Time information generation step: the GNSS disciplined clock module of the monitoring control unit 2 generates the initial time, 1PPS signal and 10MHz signal, and sends them to the controller through the first photoelectric conversion module, the photoelectric composite cable 8 and the second photoelectric conversion module, and the time information generation unit of the controller generates the time information;

[0100] The steps for preliminary timing of sensor device data: the sensor device includes a second ultra-short baseline positioning beacon 6, a Doppler odometer 10, a depth meter 9, an inertial navigation device, a scalar magnetometer and a three-component magnetometer. The data output is serial communication. The sensor device data is output in the form of a data frame. The 100MHz system clock is used to parse the serial port data bytes and the bits of each byte to obtain the start bit output time t0 of the start byte of the sensor device data frame. Time t0 is the preliminary timing time of the sensor device data.

[0101] In this embodiment, the controller obtains the time when the sensor device data is output, and uses the time information generated by the controller at this time to perform preliminary timing on the sensor device data. Specifically, the time information generation step includes:

[0102] S11, waiting for the GNSS disciplined clock module to complete discipline and output stable GNSS timing information;

[0103] S12, the time counter and the calendar module receive GNSS timing information, and the time counter uses the received GNSS timing information as initial time information;

[0104] S13, waiting for the rising edge of the next 1PPS signal, and using it as the start signal of the time counter;

[0105] S14, using the 100MHz system clock as the clock source, each time the clock rises, the time counter counts up by 1, and generates "hour-minute-second-millisecond" time information and a cross-day signal according to the time system relationship;

[0106] S15. When the GNSS signal is stable, the internal "hour-minute-second" is compared and corrected. The calendar module uses the 100MHz system clock as the clock source and generates the "year-month-day" time information according to the cross-day signal generated by the time counter and the calendar system relationship.

[0107] Since there is a signal transmission and conversion delay from the 1PPS signal output by the GNSS disciplined clock module to the controller, correction processing is required. In this embodiment, the time information generation step also includes: S16, the 1PPS delay correction module obtains the "year-month-day-hour-minute-second-millisecond" time information generated by the time counter and calendar module, and the 1PPS signal output by the GNSS disciplined clock module is received by the controller after passing through the first photoelectric conversion module, the photoelectric composite cable 8 and the second photoelectric conversion module in sequence, assuming that the "year-month-day-hour-minute-second-millisecond" time information generated by the time counter and calendar module is T0, assuming that the transmission delay of the photoelectric composite cable 8 is Δt1, assuming that the transmission delays of the first photoelectric conversion module and the second photoelectric conversion module are both Δt2, assuming that the time information corrected by the 1PPS delay correction module is T1, then T1 = T0-Δt1-Δt2-Δt2. Among them, the transmission delay of the photoelectric composite cable 8 is Δt1 = optical signal speed in the optical fiber / optical fiber length, and the transmission delay Δt2 of the photoelectric conversion module can be obtained by querying the module product manual.

[0108] In the initial timing step of the sensor device data, the sensor device data output is all serial communication, and the communication interface specifically includes RS232, RS422, and RS485. Figure 5 , is the serial communication timing and protocol for the data output of the sensor device. The data is output in the form of a data frame. The starting byte of the data frame is a special character, and the ending byte of the data frame is a special character or check data. The smallest unit of each data frame is a byte, and each byte includes 1 start bit, 8 data bits, 0 check bits, and 1 stop bit. The moment when the sensor device completes data measurement and outputs data is t0, the moment when the starting byte is fully output is t1, and the moment when the controller receives the data frame is t2. The traditional timing method is to use an embedded processor to receive a complete data frame and parse it correctly, and then use t1 or t2 as the timing information of this data frame, but these two moments will introduce time delays.

[0109] The underwater towed geomagnetic measurement data timing method of this embodiment uses a 100MHz system clock to parse the serial port data bytes and the bits of each byte, obtain the start bit output time t0 of the start byte of the sensor device data frame, and use time t0 as the initial timing time of the sensor device data. The initial timing steps of the sensor device data specifically include:

[0110] S21, the controller determines the level of the serial port input signal. When in idle state, the input signal is at a high level. When the level changes from a high level to a low level, the start bit of the data is received. The time information of the controller at this time is set to t0;

[0111] S22, after receiving a complete byte, determine whether the byte is the starting byte of the sensor device data frame, if yes, proceed to step S23, if no, return to step S21;

[0112] S23, after receiving the current data frame, determine whether the data of this frame conforms to the data protocol of the device, if yes, proceed to step S24, if no, return to step S21;

[0113] S24, combining the current frame data with the controller's time information t0 into a new data frame, completing the initial data timing, and preparing to receive the next frame data.

[0114] Among them, in step S23, if it is determined that the data frame conforms to the data protocol of the device, it indicates that the data of this frame is complete and the next step can be entered. If it is determined that the data frame does not conform to the data protocol of the device, it indicates that the data of this frame is damaged or incomplete, and it is necessary to return to step S21.

[0115] In the data of each sensor device, the geomagnetic signal is usually a slowly changing signal, but in the magnetic anomaly area and when using a mobile platform for geomagnetic measurement, the time delay from the input to the output of the magnetometer sensor signal cannot be ignored. Therefore, in this embodiment, the delay from the input of the magnetometer signal to the output of the acquisition unit is measured and corrected, and the underwater towed geomagnetic measurement data timing method also includes a magnetometer signal measurement correction step:

[0116] S31, using a scalar magnetometer to select a measurement area where the geomagnetic signal changes slowly, so that the amplitude change of the magnetic field measurement value per minute is no more than 2nT, and placing an ocean magnetic diurnal variation observation station in the measurement area;

[0117] S32, setting position a, position b and position c in sequence with a third set distance as the interval, placing the scalar magnetometer at position c, placing the permanent magnet on the side of the scalar magnetometer away from position b, and adjusting the position of the permanent magnet until the measurement value of the scalar magnetometer is about 95 μT;

[0118] S33, use a magnetometer to measure the magnetic field values ​​at position a, position b and position c in a static state, which are B a , B b and B c ;

[0119] S34, photoelectric switches are respectively provided at position a, position b and position c, an electric winch is placed on the side of the permanent magnet away from position c, a fourth set distance is spaced between the electric winch and the permanent magnet, a non-magnetic slider is connected to the noose of the electric winch, a magnetometer probe is placed on the non-magnetic slider, the electric winch pulls the non-magnetic slider at a set speed at a uniform speed, so that the magnetometer probe passes through position a, position b and position c in a straight line in sequence, when the magnetometer probe passes through position a, position b and position c, the output signal of the photoelectric switch at the corresponding position changes from a low level to a high level, the controller collects the rising edge signal output of the photoelectric switch, and then performs preliminary timing on the magnetometer output data according to the method in the step of preliminary timing of sensor device data and then outputs it;

[0120] S35. Draw the time curve of the moment when the photoelectric switch output signal changes from low level to high level and the magnetometer measurement data. See Appendix. Figure 8 , the time when the magnetometer probe reaches position a, position b and position c are t 0a ,t 0b and t 0c , the amplitude of the magnetometer measurement value reaches B a , B b and B c The time points are t 01 ,t 02 and t 03 ;

[0121] S36, assuming that the delay of the magnetometer signal from the magnetometer probe input to the magnetometer acquisition unit output is Δt3, then Δt3=[(t 03 -t 0c )+(t 02 -t 0b )] / 2, assuming that the timing time for correcting the magnetometer data is t4, then t4=t0-Δt3.

[0122] See attached Figure 7 In this embodiment, the third setting distance is selected as 0.2m, and the intervals between positions a, b and c are 0.2m respectively. The scalar magnetometer is placed at position c. When the measured value is about 95μT, the distance between the permanent magnet and position c is L. The fourth setting distance is selected as 10m, and the interval between the electric winch and the permanent magnet is 10m.

[0123] In step S31 and step S32, a scalar magnetometer is used to determine the measurement area and the placement position of the permanent magnet. In step S33 to step S36, a scalar magnetometer or a three-component magnetometer is selected. When a scalar magnetometer is selected, the delay of the scalar magnetometer signal from the scalar magnetometer probe input to the scalar magnetometer acquisition unit output is measured and corrected. When a three-component magnetometer is selected, the delay of the three-component magnetometer signal from the three-component magnetometer probe input to the three-component magnetometer acquisition unit output is measured and corrected.

[0124] In order to improve the accuracy, in this embodiment, the magnetometer signal measurement correction step further includes step S37: repeating steps S34 to S36 to obtain multiple Δt3 and taking the average value as Will The delay time from the magnetometer probe input to the magnetometer acquisition unit output of the magnetometer signal.

[0125] See attached Fig. 9 , which is a data timing flow chart of the underwater towed geomagnetic measurement data timing method of this embodiment. When the GNSS signal is good, wait for the GNSS disciplined clock module to be trained and output stable 1PPS signal, 10MHz signal and GNSS timing time information. The controller of the geomagnetic measurement device obtains the initial time and generates internal time information. The controller receives the sensor device data frame and performs preliminary timing. Determine whether the received sensor device data is magnetometer data. If the current data frame is magnetometer data, correct the magnetometer data timing time to t4=t0-Δt3, and then output the data to the monitoring computer via Ethernet; if the current data frame is not magnetometer data, directly output the data to the monitoring computer via Ethernet.

[0126] In the above-mentioned exemplary embodiment, the underwater towed geomagnetic measurement data timing method can perform geomagnetic measurement while the towing ship is sailing, without stopping the ship or slowing down, thereby improving the work efficiency of geomagnetic measurement.

[0127] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0128] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. An underwater towed geomagnetic measurement system, It is characterized in that include: Towing boats; A monitoring control unit, which is arranged on the towing vessel, and comprises: Monitor computers; A first GNSS antenna, wherein the first GNSS antenna is used to receive GNSS signals; GNSS discipline clock module, the GNSS discipline clock module is electrically connected to the first GNSS antenna, the GNSS discipline clock module is electrically connected to the monitoring computer, the GNSS discipline clock module is used to parse the GNSS signal to obtain satellite positioning, time and status information and send it to the monitoring computer, the GNSS discipline clock module is also used to output 1PPS signal and 10MHz signal; A first photoelectric conversion module, the first photoelectric conversion module is electrically connected to the GNSS disciplined clock module, and the first photoelectric conversion module is used to convert a 1PPS signal and a 10MHz signal into an optical signal; A first ultra-short baseline positioning beacon, wherein the first ultra-short baseline positioning beacon is connected to the monitoring computer via a first photoelectric conversion switch; A shipboard power supply, the shipboard power supply is used to provide working power to the monitoring control unit; A geomagnetic measuring device, the geomagnetic measuring device is connected to the monitoring control unit via an optoelectronic composite cable, and the geomagnetic measuring device comprises: A magnetometer, which is used to collect geomagnetic data; a second photoelectric conversion module, the second photoelectric conversion module being connected to the first photoelectric conversion module to convert the 1PPS signal and the 10MHz signal into an electrical signal; A controller, the controller is connected to the magnetometer to obtain geomagnetic data, the controller is connected to the second photoelectric conversion module to receive 1PPS signal and 10MHz signal generation time information, and the controller is communicatively connected to the monitoring computer via a second photoelectric conversion switch; An inertial navigation device, the inertial navigation device is connected to the controller, and the inertial navigation device is used to measure the position and attitude of the geomagnetic measurement device; a second GNSS antenna, wherein the second GNSS antenna is connected to the inertial navigation device so that the inertial navigation device acquires an initial position and attitude of the geomagnetic measurement device; A depth gauge, connected to the controller, and used to measure the depth of the geomagnetic measuring device; A Doppler speed meter, connected to the controller, and used to measure the speed of the geomagnetic measuring device; A second ultra-short baseline positioning beacon, the second ultra-short baseline positioning beacon is connected to the controller, and the second ultra-short baseline positioning beacon is connected to the first ultra-short baseline positioning beacon by hydroacoustic communication to locate the position of the geomagnetic measurement device at a low frequency; A power conversion module is connected to the shipboard power supply to provide working power for the geomagnetic measurement device.

2. The underwater towed geomagnetic measurement system according to claim 1, It is characterized in that The controller includes a time information generating unit, and the time information generating unit includes: A network communication module, the network communication module is used to obtain GNSS timing information, the GNSS timing information includes "GNSS year-month-day" and "GNSS hour-minute-second"; A phase-locked loop, wherein the phase-locked loop uses a 10 MHz signal as a reference clock to generate a 100 MHz system clock in phase with the reference clock; A time counter, the time counter is connected to the network communication module to obtain "GNSS hour-minute-second" information to generate "hour-minute-second-millisecond" time information and a cross-day signal; A calendar module, the calendar module is connected to the network communication module to obtain "GNSS year-month-day" information, the calendar module is connected to the time counter to obtain a cross-day signal, and the calendar module is used to generate "year-month-day" time information; 1PPS delay correction module, the 1PPS delay correction module is connected to the time counter and calendar module to obtain "year-month-day-hour-minute-second-millisecond" time information and perform transmission and conversion delay correction.

3. The underwater towed geomagnetic measurement system according to claim 2, It is characterized in that It also includes a first waterproof and pressure-resistant cabin and a second waterproof and pressure-resistant cabin to carry the geomagnetic measuring device. A towing ring is provided above the center of gravity of the first waterproof and pressure-resistant cabin and the second waterproof and pressure-resistant cabin. A tail wing is provided at the end of the first waterproof and pressure-resistant cabin close to the second waterproof and pressure-resistant cabin.

4. The underwater towed geomagnetic measurement system according to claim 3, It is characterized in that The magnetometer includes a scalar magnetometer and a three-component magnetometer, the scalar magnetometer includes a scalar magnetometer acquisition unit and a scalar magnetometer probe, and the three-component magnetometer includes a three-component magnetometer acquisition unit and a three-component magnetometer probe, wherein the scalar magnetometer unit and the three-component magnetometer unit are arranged in the first waterproof and pressure-resistant cabin, the scalar magnetometer probe and the three-component magnetometer probe are arranged in the second waterproof and pressure-resistant cabin, the three-component magnetometer probe and the first waterproof and pressure-resistant cabin are spaced apart by a first set distance, and the scalar magnetometer probe and the three-component magnetometer probe are spaced apart by a second set distance.

5. An underwater towed geomagnetic measurement data timing method, using the underwater towed geomagnetic measurement system according to claim 4, It is characterized in that The method comprises the following steps: Time information generation step: the GNSS disciplined clock module of the monitoring control unit generates the initial time, 1PPS signal and 10MHz signal, and sends them to the controller through the first photoelectric conversion module, the photoelectric composite cable and the second photoelectric conversion module, and the time information generation unit of the controller generates the time information; The initial timing steps of the sensor equipment data are as follows: the sensor equipment includes the second ultra-short baseline positioning beacon, Doppler log, depth meter, inertial navigation equipment, scalar magnetometer and three-component magnetometer. The data output is serial communication. The sensor equipment data is output in the form of data frames. The 100MHz system clock is used to parse the serial data bytes and the bits of each byte to obtain the start bit output time t of the start byte of the sensor equipment data frame. 0 , time t 0 It is the initial timing of the sensor device data.

6. The underwater towed geomagnetic measurement data timing method according to claim 5, It is characterized in that It also includes the magnetometer signal measurement correction steps: S31, using a scalar magnetometer to select a measurement area where the geomagnetic signal changes slowly, so that the amplitude change of the magnetic field measurement value per minute is no more than 2nT, and placing an ocean magnetic diurnal variation observation station in the measurement area; S32, setting position a, position b and position c in sequence with a third set distance as the interval, placing the scalar magnetometer at position c, placing the permanent magnet on the side of the scalar magnetometer away from position b, and adjusting the position of the permanent magnet until the measurement value of the scalar magnetometer is about 95 μT; S33, use a magnetometer to measure the magnetic field values ​​at position a, position b and position c in a static state, which are B a , B b and B c ; S34, photoelectric switches are respectively provided at position a, position b and position c, an electric winch is placed on the side of the permanent magnet away from position c, a fourth set distance is spaced between the electric winch and the permanent magnet, a non-magnetic slider is connected to the noose of the electric winch, a magnetometer probe is placed on the non-magnetic slider, the electric winch pulls the non-magnetic slider at a set speed at a uniform speed, so that the magnetometer probe passes through position a, position b and position c in a straight line in sequence, when the magnetometer probe passes through position a, position b and position c, the output signal of the photoelectric switch at the corresponding position changes from a low level to a high level, the controller collects the rising edge signal output of the photoelectric switch, and then performs preliminary timing on the magnetometer output data according to the method in the step of preliminary timing of sensor device data and then outputs it; S35, draw the time curve of the moment when the photoelectric switch output signal changes from low level to high level and the time curve of the magnetometer measurement data, and obtain the moment when the magnetometer probe reaches position a, position b and position c respectively. 0a ,t 0b and t 0c , the amplitude of the magnetometer measurement value reaches B a , B b and B c The time points are t 01 ,t 02 and t 03 ; S36, assuming that the delay of the magnetometer signal from the magnetometer probe input to the magnetometer acquisition unit output is Δt 3 , then Δt 3 =[(t 03 -t 0c )+(t 02 -t 0b )] / 2, assuming that the timing time for correcting the magnetometer data is t 4 , then t 4 =t 0 -Δt 3 .

7. The underwater towed geomagnetic measurement data timing method according to claim 6, It is characterized in that The magnetometer signal measurement correction step further includes step S37: repeating steps S34 to S36 to obtain multiple Δt 3 And take the average value as Will It is the delay time from the magnetometer signal input to the magnetometer acquisition unit output.

8. The underwater towed geomagnetic measurement data timing method according to claim 5, It is characterized in that The time information generating step comprises: S11, waiting for the GNSS disciplined clock module to complete discipline and output stable GNSS timing information; S12, the time counter and the calendar module receive GNSS timing information, and the time counter uses the received GNSS timing information as initial time information; S13, waiting for the rising edge of the next 1PPS signal, and using it as the start signal of the time counter; S14, using the 100MHz system clock as the clock source, each time the clock rises, the time counter counts up by 1, and generates "hour-minute-second-millisecond" time information and a cross-day signal according to the time system relationship; S15. When the GNSS signal is stable, the internal "hour-minute-second" is compared and corrected. The calendar module uses the 100MHz system clock as the clock source and generates the "year-month-day" time information based on the cross-day signal generated by the time counter and the calendar system relationship.

9. The underwater towed geomagnetic measurement data timing method according to claim 8, It is characterized in that The time information generation step also includes: S16, the 1PPS delay correction module obtains the "year-month-day-hour-minute-second-millisecond" time information generated by the time counter and the calendar module, and the 1PPS signal output by the GNSS disciplined clock module is received by the controller after passing through the first photoelectric conversion module, the photoelectric composite cable and the second photoelectric conversion module in sequence. The "year-month-day-hour-minute-second-millisecond" time information generated by the time counter and the calendar module is set as T 0 , assuming that the transmission delay of the optical-electric composite cable is Δt 1 , assuming that the transmission delay of the first photoelectric conversion module and the second photoelectric conversion module are both Δt 2 , let the time information corrected by the 1PPS delay correction module be T 1 , then T 1 =T 0 -Δt 1 -Δt 2 -Δt 2 .

10. The underwater towed geomagnetic measurement data timing method according to claim 5, It is characterized in that The sensor device data preliminary timing step includes: S21, the controller determines the level of the serial port input signal. In the idle state, the input signal is high level. When the level changes from high level to low level, the start bit of the data is received. Let the time information of the controller at this time be t 0 ; S22, after receiving a complete byte, determine whether the byte is the starting byte of the sensor device data frame, if yes, proceed to step S23, if no, return to step S21; S23, after receiving the current data frame, determine whether the data of this frame conforms to the data protocol of the device, if yes, proceed to step S24, if no, return to step S21; S24, compare the current frame data with the time information t of the controller 0 Merge into a new data frame, complete the initial data timing, and prepare to receive the next frame of data.

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