A zero-flux magnetometer system and method based on primary and secondary dual probe hierarchical compensation

Abstract

This invention relates to the field of magnetic field measurement and precision instrument technology, specifically to a zero-flux magnetometer system and method based on hierarchical compensation using a dual-probe setup. The system includes a secondary fluxgate probe and a primary fluxgate probe. The secondary fluxgate probe detects the background magnetic field and outputs a demodulated signal. A background magnetic field compensation module generates a first compensation current based on this signal, causing a background compensation coil to generate a reverse compensation magnetic field in the region of the primary fluxgate probe, thus performing physical pre-compensation for the background magnetic field. The primary fluxgate probe detects the residual magnetic field after pre-compensation. A zero-flux feedback loop generates a second compensation current based on the demodulated output signal from the primary probe, maintaining the primary probe in a zero-flux closed-loop state. A data acquisition and processing module reconstructs the measured magnetic field based on the background magnetic field component corresponding to the first compensation current and the residual magnetic field component corresponding to the second compensation current.

Description

Technical Field

[0001] This invention relates to the field of magnetic field measurement and precision instrument technology, specifically to a zero-flux magnetometer system and method based on primary and secondary dual-probe hierarchical compensation. Background Technology

[0002] High-precision magnetic field measurement is widely used in aerospace magnetic surveying, geomagnetic navigation, weak magnetic target detection, and precision instruments. Fluxgate magnetometers, due to their high sensitivity, large measurement range, and ability to operate at room temperature, often employ a zero-flux closed-loop structure. A compensation magnetic field is generated through a feedback coil to keep the magnetic core in a closed-loop state within a preset zero-flux balance range, thereby improving linearity and stability.

[0003] However, in spacecraft platforms or complex electromagnetic environments, the probe is simultaneously affected by the geomagnetic background field, the platform's residual magnetism, the interference magnetic field of the payload equipment, and the slowly varying magnetic field of the environment. Traditional single-probe zero-flux magnetometers use the same probe to simultaneously compensate for the background magnetic field and measure the weak residual magnetic field. This can easily lead to the background magnetic field occupying the dynamic range of the main measurement channel, reducing the effective signal amplitude corresponding to the weak magnetic field changes, and thus affecting resolution and stability.

[0004] Existing technologies often improve performance by increasing probe sensitivity, enhancing feedback capability, and employing high-bit-to-digital converters or back-end digital filtering. However, they still struggle to balance large-range background magnetic field suppression with high-resolution weak magnetic field measurement, and they also increase cost, power consumption, and engineering verification difficulty.

[0005] In view of this, the present invention proposes a zero-flux magnetometer system and method based on hierarchical compensation of primary and secondary dual probes. Summary of the Invention

[0006] The purpose of this invention is to provide a zero-flux magnetometer system and method based on hierarchical compensation of main and auxiliary dual probes, so as to solve the problems of existing single-probe zero-flux magnetometers having their main measurement channel dynamic range occupied, residual weak magnetic field resolution reduced, and high dependence on high bit-number analog-to-digital converters under the influence of large background magnetic fields or platform interference magnetic fields.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a zero flux magnetometer system based on hierarchical compensation of main and auxiliary dual probes, including an auxiliary fluxgate probe, a main fluxgate probe, an auxiliary probe signal processing module, a main probe signal processing module, a background magnetic field compensation module, a zero flux feedback loop, and a data acquisition and processing module.

[0009] The secondary fluxgate probe is used to detect the background magnetic field and output the secondary probe sensing signal. The secondary probe signal processing module is used to process the secondary probe sensing signal and obtain the secondary probe demodulated output signal Va.

[0010] The background magnetic field compensation module is used to generate a first compensation current I1 based on Va and inject I1 into the background compensation coil located in the area of ​​the main fluxgate probe, so that the background compensation coil generates a compensation magnetic field opposite to the direction of the background magnetic field, so as to perform physical pre-compensation of the background magnetic field in the area before the main fluxgate probe detects.

[0011] The main fluxgate probe is used to detect the residual magnetic field after pre-compensation and output the main probe sensing signal. The main probe signal processing module is used to process the main probe sensing signal and obtain the main probe demodulated output signal Vm.

[0012] The zero flux feedback loop is used to generate a second compensation current I2 based on Vm, and input I2 into the feedback coil of the main flux gate probe, so that the feedback coil generates a feedback magnetic field opposite to the direction of the residual magnetic field, so that the main flux gate probe maintains a closed loop state within the preset zero flux balance range.

[0013] The data acquisition and processing module is used to synchronously acquire Va, Vm, I1 and I2, perform time alignment on the synchronously acquired data, and calculate the measured magnetic field B according to B0=k1·(I1-I10), B1=k2·(I2-I20) and B=B0+B1.

[0014] Where B0 is the background magnetic field component, B1 is the residual magnetic field component, k1 and k2 are signed calibration coefficients, and I10 and I20 are the zero-point bias of the compensation current.

[0015] As a preferred embodiment of the present invention, both the secondary fluxgate probe and the primary fluxgate probe include a magnetic core, an excitation coil, and an induction coil. The excitation coil is used to apply a periodic alternating excitation signal to the magnetic core, causing the magnetic core to periodically enter forward saturation and reverse saturation states. The induction coil is used to sense the magnetic flux change generated by the magnetic core under the action of an external magnetic field and output the corresponding induction signal. The secondary fluxgate probe and the primary fluxgate probe share the same excitation source, and the secondary probe signal processing module and the primary probe signal processing module use the same source reference signal for synchronous demodulation.

[0016] As a preferred technical solution of the present invention, the sensitive axis directions of the secondary fluxgate probe and the primary fluxgate probe are parallel and are spaced apart, so that the background magnetic field detected by the secondary fluxgate probe and the background magnetic field in the area where the primary fluxgate probe is located satisfy a preset spatial correlation, and the coupling magnetic field generated by the background compensation coil and the feedback coil at the secondary fluxgate probe is lower than a preset crosstalk threshold.

[0017] The preset spatial correlation is determined by synchronously acquiring the background magnetic field of the area where the auxiliary fluxgate probe and the main fluxgate probe are located at different probe spacings, and based on the correlation between the two background magnetic field sampling sequences; the preset crosstalk threshold is determined based on the change in the output signal of the auxiliary fluxgate probe when the background compensation coil and the feedback coil are driven respectively.

[0018] As a preferred embodiment of the present invention, the secondary probe signal processing module includes a secondary probe synchronous demodulation circuit, a secondary probe low-noise amplification circuit, and a secondary probe integration circuit. The secondary probe synchronous demodulation circuit uses the excitation signal as a demodulation reference to extract the effective magnetic field component corresponding to the background magnetic field from the secondary probe induced signal. The secondary probe low-noise amplification circuit amplifies the demodulated signal, and the secondary probe integration circuit integrates the amplified signal to obtain the secondary probe demodulated output signal Va.

[0019] As a preferred embodiment of the present invention, the background magnetic field compensation module includes a compensation current generation circuit and a current detection circuit; the compensation current generation circuit is used to generate a first compensation current I1 based on the demodulated output signal Va of the sub-probe, and output I1 to the background compensation coil; the current detection circuit is used to detect the actual I1 flowing through the background compensation coil and feed it back to the data acquisition and processing module.

[0020] The compensation current generation circuit is a voltage-to-current conversion circuit that converts Va into I1, or it may include an analog-to-digital conversion circuit, a data acquisition and processing module, a digital-to-analog conversion circuit, and a constant current drive circuit. The analog-to-digital conversion circuit is used to convert Va into a digital sampled value, the data acquisition and processing module is used to generate a digital compensation control quantity based on the digital sampled value, and the digital-to-analog conversion circuit and the constant current drive circuit are used to output I1 based on the digital compensation control quantity.

[0021] As a preferred embodiment of the present invention, the main probe signal processing module includes a main probe synchronous demodulation circuit, a main probe low-noise amplification circuit, and a main probe integration circuit; the main probe synchronous demodulation circuit uses the excitation signal as a demodulation reference to extract the effective magnetic field component corresponding to the residual magnetic field from the main probe induced signal; the main probe low-noise amplification circuit amplifies the demodulated residual magnetic field signal, and the main probe integration circuit integrates the amplified signal to obtain the main probe demodulated output signal Vm.

[0022] As a preferred embodiment of the present invention, the amplification factor of the low-noise amplifier circuit of the main probe is greater than that of the low-noise amplifier circuit of the secondary probe, so that the signal processing module of the main probe processes the residual magnetic field signal with a gain higher than that of the signal processing module of the secondary probe after the background magnetic field is pre-compensated.

[0023] As a preferred technical solution of the present invention, k1, k2, I10 and I20 are obtained by collecting the first compensation current I1 and the second compensation current I2 under a known standard magnetic field environment and performing linear fitting, multi-point calibration or temperature segment calibration; the data acquisition and processing module is also used to correct k1, k2, I10 and I20 according to the temperature data collected by the temperature sensor.

[0024] The data acquisition and processing module also stores the crosstalk calibration parameters between the main and auxiliary fluxgate probes, and performs crosstalk correction on the demodulated output signal Va or the first compensation current I1 of the auxiliary probe according to the crosstalk calibration parameters. The crosstalk calibration parameters are used to characterize the coupling effect of the magnetic field generated by the background compensation coil and the feedback coil on the detection result of the auxiliary fluxgate probe.

[0025] As a preferred technical solution of the present invention, the data acquisition and processing module synchronously samples Va, Vm, I1 and I2 and performs time alignment so that Va, Vm, I1 and I2 within the same sampling period have the same or convertible time identifier; the data acquisition and processing module is also used to perform amplitude limiting judgment on I1 and I2, and outputs background compensation range prompt when I1 exceeds a preset first current threshold, and outputs zero flux closed loop status prompt or closed loop loss risk prompt when I2 exceeds a preset second current threshold.

[0026] Secondly, the present invention provides a zero-flux magnetometer measurement method based on primary and secondary dual-probe hierarchical compensation, which is implemented using the first aspect and includes the following steps:

[0027] S101, activate the main fluxgate probe, the auxiliary fluxgate probe, and the excitation signal;

[0028] S102, the auxiliary fluxgate probe detects the background magnetic field and outputs the auxiliary probe sensing signal;

[0029] S103 performs synchronous demodulation, low-noise preamplification, and integration processing on the sub-probe sensing signal to obtain the sub-probe demodulated output signal Va.

[0030] S104, Generate a first compensation current I1 based on Va, and inject I1 into the background compensation coil located in the area where the main fluxgate probe is located, so that the background compensation coil generates a compensation magnetic field opposite to the direction of the background magnetic field, and performs physical pre-compensation on the background magnetic field in the area where the main fluxgate probe is located.

[0031] S105, the main fluxgate probe detects the residual magnetic field after pre-compensation and outputs the main probe induction signal;

[0032] S106 performs synchronous demodulation, low-noise preamplification, and integration processing on the main probe sensing signal to obtain the main probe demodulated output signal Vm.

[0033] S107, generate a second compensation current I2 according to Vm, and input I2 into the feedback coil of the main fluxgate probe, so that the feedback coil generates a feedback magnetic field opposite to the direction of the residual magnetic field, so that the main fluxgate probe maintains a closed loop state within the preset zero flux balance range.

[0034] S108 synchronously acquires Va, Vm, I1, and I2, and performs time alignment on the synchronously acquired data;

[0035] S109, calculate the background magnetic field component B0 according to B0=k1·(I1-I10), and calculate the residual magnetic field component B1 according to B1=k2·(I2-I20), where k1 and k2 are signed calibration coefficients that include the direction of compensation current, coil winding direction, positive direction of probe sensitive axis and signal processing polarity relationship.

[0036] S110 calculates the measured magnetic field B according to B=B0+B1 and outputs the measurement result.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] This invention first detects the background magnetic field using a secondary fluxgate probe. A background magnetic field compensation module then generates a first compensation current based on the demodulated output signal from the secondary probe. This causes the background compensation coil to produce a compensation magnetic field in the region of the main fluxgate probe, opposite in direction to the background magnetic field. This effectively reduces the obstruction of the main measurement channel by the background magnetic field at the main probe's measurement front end. Furthermore, the main fluxgate probe performs zero-flux closed-loop measurement only on the pre-compensated residual magnetic field, and the second compensation current characterizes the residual magnetic field component. Therefore, the main probe's signal processing channel can use a higher amplification factor to process weak magnetic field signals, improving the effective resolution of the weak residual magnetic field. Simultaneously, the data acquisition and processing module reconstructs the measured magnetic field based on the background magnetic field component corresponding to the first compensation current and the residual magnetic field component corresponding to the second compensation current. Thus, while ensuring complete magnetic field measurement results, it reduces reliance on high-bit-to-digital converters and improves the stability and engineering applicability of magnetic field measurements in complex electromagnetic environments. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the zero-flux magnetometer system structure based on hierarchical compensation of main and auxiliary dual probes according to the present invention;

[0040] Figure 2 This is a flowchart of the zero-flux magnetometer measurement method based on primary and secondary dual-probe graded compensation according to the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be noted that the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] Example 1

[0044] Please see Figure 1 This invention provides a zero flux magnetometer system based on hierarchical compensation of main and auxiliary dual probes, including an auxiliary fluxgate probe, a main fluxgate probe, an auxiliary probe signal processing module, a main probe signal processing module, a background magnetic field compensation module, a zero flux feedback loop, and a data acquisition and processing module.

[0045] The secondary fluxgate probe is used to detect the background magnetic field or platform interference magnetic field in the measurement environment, while the primary fluxgate probe is used to detect the residual magnetic field after background magnetic field compensation. The secondary probe signal processing module processes the induced signal output by the secondary fluxgate probe to obtain the demodulated output signal Va. The background magnetic field compensation module generates a first compensation current I1 based on the demodulated output signal Va and applies it to the area where the primary fluxgate probe is located, performing physical pre-compensation for the background magnetic field in that area before the primary fluxgate probe detects the residual magnetic field. The primary probe signal processing module processes the residual magnetic field signal output by the primary fluxgate probe to obtain the demodulated output signal Vm. The zero flux feedback loop generates a second compensation current I2 based on the demodulated output signal Vm, maintaining the primary fluxgate probe in a closed-loop state within a preset zero flux balance range. The data acquisition and processing module is used to synchronously acquire the demodulated output signal Va of the sub-probe, the demodulated output signal Vm of the main probe, the first compensation current I1 and the second compensation current I2, and reconstruct the measured magnetic field B based on the first compensation current I1 and the second compensation current I2.

[0046] Both the secondary fluxgate and primary fluxgate probes include a magnetic core, an excitation coil, and an induction coil. The excitation coil applies a periodic alternating excitation signal to the magnetic core, causing it to periodically enter forward and reverse saturation states. The induction coil senses the flux change generated by the magnetic core under the influence of an external magnetic field and outputs an induced signal related to the external magnetic field. The sensitive axes of the secondary and primary fluxgate probes are parallel and arranged within the same measurement area, with the secondary probe positioned close to the primary probe. This ensures that the background magnetic field detected by the secondary probe has a preset spatial correlation with the background magnetic field in the area where the primary probe is located. A preset distance is maintained between the secondary and primary fluxgate probes. This preset distance ensures that the ambient background magnetic field detected by the secondary and primary probes satisfies the preset spatial correlation and that the coupling magnetic field generated by the background compensation coil and feedback coil at the secondary probe is below a preset crosstalk threshold. This reduces the crosstalk between the background compensation magnetic field and the zero-flux feedback magnetic field at the primary probe on the detection results of the secondary probe.

[0047] The preset spatial correlation can be determined by simultaneously acquiring the background magnetic fields in the regions where the secondary fluxgate and primary fluxgate probes are located at different probe spacings, and calculating the correlation coefficient between the two background magnetic field sampling sequences. The preset crosstalk threshold can be determined by driving the background compensation coil and the feedback coil respectively, detecting the change in the output signal of the secondary fluxgate probe, and based on the allowable background magnetic field measurement error. Thus, while ensuring the spatial consistency of the background magnetic field, the crosstalk of the two-stage compensation magnetic field to the secondary fluxgate probe is controlled.

[0048] The secondary probe signal processing module includes a secondary probe synchronous demodulation circuit, a secondary probe low-noise amplification circuit, and a secondary probe integrator circuit. The output signal from the induction coil of the secondary fluxgate probe is input to the secondary probe synchronous demodulation circuit, which uses the excitation signal as a demodulation reference to extract the effective magnetic field component corresponding to the background magnetic field from the output signal of the secondary fluxgate probe. The secondary probe low-noise amplification circuit amplifies the demodulated signal, and the secondary probe integrator circuit integrates the amplified signal to obtain the secondary probe demodulated output signal Va.

[0049] The demodulated output signal Va of the secondary probe satisfies:

[0050] Va = Ka·Bbg + Va0;

[0051] Wherein, Ka is the magnetic field-to-voltage conversion coefficient of the secondary fluxgate probe, Bbg is the background magnetic field detected by the secondary fluxgate probe, and Va0 is the zero bias of the secondary fluxgate probe; the secondary probe signal processing module is mainly used to detect larger background magnetic field components, so its amplification factor is set according to the background magnetic field range to avoid saturation of the secondary probe signal processing channel when the background magnetic field is large.

[0052] The background magnetic field compensation module is connected to the secondary probe signal processing module. The background magnetic field compensation module receives the demodulated output signal Va from the secondary probe and generates a first compensation current I1 based on Va, a preset compensation ratio coefficient, and compensation direction parameters. The first compensation current I1 is input to the background compensation coil located in the area where the main fluxgate probe is located. The background compensation coil generates a compensation magnetic field in the area where the main fluxgate probe is located, opposite in direction to the background magnetic field, to cancel or weaken the background magnetic field at the main fluxgate probe. Therefore, the main fluxgate probe does not directly experience the complete background magnetic field, but detects the residual magnetic field under conditions where the background magnetic field has been pre-compensated.

[0053] In one analog control implementation, the background magnetic field compensation module includes a voltage-to-current conversion circuit and a current detection circuit. The voltage-to-current conversion circuit generates a first compensation current I1 based on the demodulated output signal Va of the secondary probe, a preset compensation ratio coefficient, and compensation direction parameters, and outputs the first compensation current I1 to the background compensation coil; the current detection circuit detects the actual first compensation current I1 flowing through the background compensation coil in real time and feeds the first compensation current I1 back to the data acquisition and processing module.

[0054] In another digital control implementation, the background magnetic field compensation module includes an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), a constant current drive circuit, and a current detection circuit. The ADC converts the demodulated output signal Va from the secondary probe into a digital sample value and inputs it to the data acquisition and processing module. The data acquisition and processing module generates a digital compensation control quantity based on the digital sample value, a preset compensation ratio coefficient, and compensation direction parameters. The DAC converts the digital compensation control quantity into an analog control signal. The constant current drive circuit outputs a first compensation current I1 based on the analog control signal. The current detection circuit detects the first compensation current I1 in real time and feeds it back to the data acquisition and processing module.

[0055] The background magnetic field compensation module includes a digital-to-analog converter circuit, a constant current drive circuit, and a current detection circuit. The digital-to-analog converter circuit generates an analog control signal based on the demodulated output signal Va from the secondary probe or the digital control quantity processed by the data acquisition and processing module. The constant current drive circuit outputs a first compensation current I1 based on the analog control signal. The current detection circuit detects the first compensation current I1 in real time and feeds it back to the data acquisition and processing module. The data acquisition and processing module uses the actual first compensation current I1 flowing through the background compensation coil as the basis for calculating the background magnetic field components, thereby reducing the impact of drive circuit errors, temperature drift, or coil parameter variations on the measurement results.

[0056] The main probe signal processing module includes a main probe synchronous demodulation circuit, a main probe low-noise amplifier circuit, and a main probe integrating circuit. The output signal of the induction coil of the main fluxgate probe is input to the main probe synchronous demodulation circuit, which uses the excitation signal as a demodulation reference to extract the effective magnetic field component corresponding to the residual magnetic field from the output signal of the main fluxgate probe. The main probe low-noise amplifier circuit amplifies the demodulated residual magnetic field signal, and the main probe integrating circuit integrates the amplified signal to obtain the main probe demodulated output signal Vm. Since the background magnetic field at the main fluxgate probe has been pre-canceled or weakened by the first compensation current I1, the amplification factor of the main probe low-noise amplifier circuit is greater than that of the secondary probe low-noise amplifier circuit to improve the effective resolution of the weak residual magnetic field signal. That is, the secondary probe signal processing channel is configured with a gain according to the larger background magnetic field range, and the main probe signal processing channel is configured with a higher gain according to the pre-compensated residual magnetic field range, thus forming a hierarchical signal processing structure that matches the range and resolution.

[0057] The demodulated output signal Vm of the main probe satisfies:

[0058] Vm = Km·Bres + Vm0;

[0059] Wherein, Km is the magnetic field-voltage conversion coefficient of the main fluxgate probe, Bres is the residual magnetic field at the main fluxgate probe after background compensation, and Vm0 is the zero bias of the main fluxgate probe.

[0060] The zero-flux feedback loop is connected to the main probe signal processing module. The zero-flux feedback loop generates a second compensation current I2 based on the demodulated output signal Vm of the main probe and inputs this second compensation current I2 into the feedback coil of the main fluxgate probe. The feedback coil generates a feedback magnetic field opposite in direction to the residual magnetic field, maintaining the core of the main fluxgate probe in a closed-loop state within a preset zero-flux equilibrium range. When the residual magnetic field changes, the demodulated output signal Vm of the main probe changes accordingly, and the zero-flux feedback loop adjusts the second compensation current I2 to allow the main fluxgate probe to return to a closed-loop equilibrium state. The second compensation current I2 is used to characterize the residual magnetic field component that still acts on the main fluxgate probe after the background magnetic field pre-compensation.

[0061] The data acquisition and processing module is connected to the secondary probe signal processing module, the primary probe signal processing module, the background magnetic field compensation module, and the zero flux feedback loop, respectively. The module synchronously samples the demodulated output signal Va from the secondary probe, the demodulated output signal Vm from the primary probe, the first compensation current I1, and the second compensation current I2, and performs time alignment on the sampled data. Va, Vm, I1, and I2 within the same sampling period are assigned the same or a convertible time identifier to reduce timing errors between changes in the background magnetic field, the first compensation current, the residual magnetic field, and the second compensation current. The data acquisition and processing module can be implemented using an MCU, FPGA, DSP, spaceborne computer, or other embedded processor. The analog-to-digital converter (ADC) can select the appropriate number of effective bits according to the measurement range, sampling rate, and resolution requirements. Since the background magnetic field has already undergone physical pre-compensation at the primary probe measurement front end, the requirements for the dynamic range and effective bits of the ADC can be reduced while obtaining the same residual magnetic field measurement resolution.

[0062] Before the system is put into measurement, the auxiliary fluxgate probe, main fluxgate probe, background compensation coil, and feedback coil are calibrated. The calibration process includes: applying multiple standard magnetic fields of different intensities under a known standard magnetic field environment; recording the first compensation current I1 and the second compensation current I2 corresponding to each standard magnetic field; and determining the calibration coefficient k1 between the first compensation current I1 and the background magnetic field component, the calibration coefficient k2 between the second compensation current I2 and the residual magnetic field component, the zero-point offset I10 of the first compensation current, and the zero-point offset I20 of the second compensation current based on the recorded results. k1, k2, I10, and I20 can be obtained through linear fitting, multi-point calibration, or temperature-segmented calibration.

[0063] The calibration coefficients k1 and k2 are signed calibration coefficients. During the calibration process, the positive directions of the measured magnetic field, the positive directions of the sensitive axes of the main fluxgate and auxiliary fluxgate probes, the positive directions of the first compensation current I1 and the second compensation current I2, and the winding directions of the background compensation coil and the feedback coil are uniformly defined. Thus, k1 and k2 contain the correspondence between the winding direction of the compensation coil, the direction of the compensation current, the positive direction of the probe's sensitive axis, and the signal processing polarity, so that the converted background magnetic field component B0 and residual magnetic field component B1 are both represented according to the same measurement coordinate system.

[0064] After calibration, the data acquisition and processing module calculates the background magnetic field component B0 based on the first compensation current I1:

[0065] B0 = k1·(I1-I10);

[0066] Wherein, B0 is the background magnetic field component detected by the auxiliary fluxgate probe and obtained by the background magnetic field compensation module; k1 is the signed calibration coefficient between the first compensation current and the background magnetic field component; I1 is the first compensation current acquired in real time; and I10 is the zero-point bias of the first compensation current.

[0067] The data acquisition and processing module calculates the residual magnetic field component B1 based on the second compensation current I2:

[0068] B1 = k2·(I2-I20);

[0069] Among them, B1 is the residual magnetic field component detected by the main fluxgate probe after background magnetic field pre-compensation; k2 is the signed calibration coefficient between the second compensation current and the residual magnetic field component; I2 is the second compensation current acquired in real time; and I20 is the zero-point bias of the second compensation current.

[0070] The data acquisition and processing module superimposes the background magnetic field component B0 and the residual magnetic field component B1 to obtain the final measured magnetic field B:

[0071] B = B0 + B1;

[0072] Since B0 and B1 are both obtained by conversion using signed calibration coefficients that include the current direction, coil winding direction, positive direction of the probe sensitive axis, and signal processing polarity, they have been unified to the same magnetic field coordinate direction. Therefore, they are reconstructed according to B=B0+B1.

[0073] Therefore, the background magnetic field component corresponding to the secondary fluxgate probe and the residual magnetic field component corresponding to the primary fluxgate probe are reconstructed into the complete measured magnetic field value. This measurement method does not simply subtract or add the output signals of the two probes at the data processing end, but first converts the detection result of the secondary fluxgate probe into a first compensation current I1, and forms a physical compensation magnetic field in the region where the primary fluxgate probe is located. Then, the primary fluxgate probe detects the pre-compensated residual magnetic field in a zero flux closed-loop state, and finally reconstructs the magnetic field based on the magnetic field components corresponding to the two-stage compensation current.

[0074] Example 2

[0075] like Figure 2 As shown, this embodiment, based on the system structure of Embodiment 1, provides a zero-flux magnetometer measurement method based on hierarchical compensation of a main and auxiliary dual-probe system. This method includes the following steps:

[0076] S101, activate the main fluxgate probe, the auxiliary fluxgate probe and the excitation signal, so that the magnetic cores of the main fluxgate probe and the auxiliary fluxgate probe enter the positive saturation and reverse saturation states respectively under the action of the periodic alternating excitation signal.

[0077] S102, the secondary fluxgate probe detects the background magnetic field in the measurement environment and outputs the secondary probe sensing signal through the induction coil of the secondary fluxgate probe. The background magnetic field includes at least one of the following: geomagnetic background field, platform residual magnetism, load equipment interference magnetic field, or slowly varying environmental magnetic field.

[0078] S103, the secondary probe signal processing module performs synchronous demodulation, low-noise pre-amplification, and integration processing on the secondary probe's induced signal to obtain the secondary probe demodulated output signal Va. Specifically, the secondary probe synchronous demodulation circuit uses the excitation signal as a demodulation reference to extract the effective magnetic field component corresponding to the background magnetic field from the secondary probe's induced signal; the secondary probe low-noise amplification circuit amplifies the demodulated signal; and the secondary probe integration circuit integrates the amplified signal to obtain the secondary probe demodulated output signal Va.

[0079] S104, the background magnetic field compensation module generates a first compensation current I1 based on the demodulated output signal Va of the secondary probe, and injects the first compensation current I1 into the background compensation coil located in the area of ​​the main fluxgate probe. This causes the background compensation coil to generate a compensation magnetic field opposite to the direction of the background magnetic field, thereby physically pre-compensating the background magnetic field in the area of ​​the main fluxgate probe. Through this step, the background magnetic field experienced by the main fluxgate probe is canceled or weakened, so that the main fluxgate probe no longer directly undertakes the task of measuring and compensating the complete background magnetic field.

[0080] When using analog control, the demodulated output signal Va from the secondary probe is input to the voltage-to-current conversion circuit, which generates the first compensation current I1 based on Va. When using digital control, Va is first converted into a digital sample value, and the data acquisition and processing module generates a digital compensation control quantity based on the digital sample value. Then, the first compensation current I1 is generated through the digital-to-analog conversion circuit and the constant current drive circuit.

[0081] S105, the main fluxgate probe detects the residual magnetic field after the background magnetic field has been pre-compensated, and outputs the main probe sensing signal through the induction coil of the main fluxgate probe. The residual magnetic field is the magnetic field component of the background magnetic field that still acts on the main fluxgate probe after being canceled or weakened by the compensation magnetic field corresponding to the first compensation current I1.

[0082] S106, the main probe signal processing module performs synchronous demodulation, low-noise pre-amplification, and integration processing on the main probe's induced signal to obtain the main probe demodulated output signal Vm. Specifically, the main probe synchronous demodulation circuit uses the excitation signal as the demodulation reference to extract the effective magnetic field component corresponding to the residual magnetic field from the main probe's induced signal; the main probe low-noise amplification circuit amplifies the demodulated residual magnetic field signal; and the main probe integration circuit integrates the amplified signal to obtain the main probe demodulated output signal Vm. Since the background magnetic field at the main fluxgate probe has been pre-compensated, the main probe low-noise amplification circuit can process the weak residual magnetic field signal with a higher amplification factor.

[0083] S107, the zero-flux feedback loop generates a second compensation current I2 based on the demodulated output signal Vm of the main probe, and inputs the second compensation current I2 into the feedback coil of the main fluxgate probe. This causes the feedback coil to generate a feedback magnetic field opposite to the direction of the residual magnetic field, so that the magnetic core of the main fluxgate probe remains in a closed-loop state within a preset zero-flux balance range. When the residual magnetic field changes, the demodulated output signal Vm of the main probe changes accordingly, and the zero-flux feedback loop adjusts the second compensation current I2, so that the main fluxgate probe returns to a closed-loop balance state.

[0084] S108, the data acquisition and processing module synchronously acquires the demodulated output signal Va from the secondary probe, the demodulated output signal Vm from the main probe, the first compensation current I1, and the second compensation current I2, and performs time alignment on the sampled data. Va, Vm, I1, and I2 within the same sampling period have the same or convertible time identifiers to reduce timing errors between changes in the background magnetic field, changes in the first compensation current, changes in the residual magnetic field, and changes in the second compensation current.

[0085] S109, the data acquisition and processing module calculates the background magnetic field component B0 based on the first compensation current I1, and calculates the residual magnetic field component B1 based on the second compensation current I2, wherein:

[0086] B0 = k1·(I1-I10);

[0087] B1 = k2·(I2-I20);

[0088] Wherein, B0 is the background magnetic field component detected by the auxiliary fluxgate probe and obtained by the background magnetic field compensation module, B1 is the residual magnetic field component detected by the main fluxgate probe after background magnetic field pre-compensation, k1 is the calibration coefficient between the first compensation current I1 and the background magnetic field component, k2 is the calibration coefficient between the second compensation current I2 and the residual magnetic field component, I10 is the zero-point bias of the first compensation current, and I20 is the zero-point bias of the second compensation current.

[0089] k1 and k2 are signed calibration coefficients. The signed calibration coefficients include the correspondence between the directions of the first compensation current I1 and the second compensation current I2, the winding direction of the background compensation coil and the feedback coil, the positive direction of the sensitive axis of the main and auxiliary fluxgate probes, and the signal processing polarity, so that the background magnetic field component B0 and the residual magnetic field component B1 are represented according to the same measurement coordinate direction.

[0090] S110, the data acquisition and processing module superimposes the background magnetic field component B0 and the residual magnetic field component B1 to calculate the measured magnetic field B, and outputs the measurement result, wherein:

[0091] B = B0 + B1.

[0092] Therefore, the background magnetic field component corresponding to the secondary fluxgate probe and the residual magnetic field component corresponding to the primary fluxgate probe are reconstructed into the complete measured magnetic field value. This measurement method does not simply subtract or add the output signals of the two probes at the data processing end, but firstly, a physical compensation magnetic field is formed in the region where the primary fluxgate probe is located through the first compensation current I1, then the primary fluxgate probe detects the pre-compensated residual magnetic field in a zero flux closed-loop state, and finally, the magnetic field components corresponding to the two-stage compensation current are reconstructed.

[0093] In a preferred embodiment, the secondary fluxgate probe and the primary fluxgate probe share the same excitation source. When sharing the same excitation source, the secondary probe signal processing module and the primary probe signal processing module use a common reference signal for synchronous demodulation to improve the consistency of the demodulation results. In another embodiment, the secondary fluxgate probe and the primary fluxgate probe are each provided with an independent excitation source, so that the excitation frequency and excitation amplitude can be set according to the core parameters, sensitivity, or range of different probes.

[0094] In a preferred embodiment, the data acquisition and processing module performs amplitude limiting judgment on the first compensation current I1 and the second compensation current I2. When the first compensation current I1 exceeds a preset first current threshold, it is determined that the background magnetic field or external interference magnetic field exceeds the effective compensation range of the background compensation coil, and a background compensation range prompt is output. When the second compensation current I2 exceeds a preset second current threshold, it is determined that the residual magnetic field at the main fluxgate probe exceeds the effective adjustment range of the zero flux feedback loop, and a zero flux feedback over-limit prompt or a closed-loop lockout risk prompt is output. By limiting the amplitude, distorted magnetic field results can be avoided even after the compensation current enters the nonlinear region.

[0095] In a preferred embodiment, the data acquisition and processing module corrects k1, k2, I10, and I20 based on the temperature data collected by the temperature sensor. Specifically, a calibration parameter table is pre-established for different temperature points. During measurement, the corresponding calibration parameters are called according to the current temperature, or k1, k2, I10, and I20 at the current temperature are obtained through interpolation. Temperature correction can reduce the impact of coil resistance changes, core characteristic changes, and analog circuit zero drift on the measurement results.

[0096] In a preferred embodiment, crosstalk between the secondary fluxgate probe and the primary fluxgate probe is corrected using a pre-calibration matrix. During calibration, a known background magnetic field and a known feedback magnetic field are applied respectively to obtain the crosstalk coefficient of the secondary fluxgate probe output affected by the background compensation coil or the feedback coil magnetic field. During measurement, the data acquisition and processing module corrects the demodulated output signal Va of the secondary probe or the first compensation current I1 based on the crosstalk coefficient, so that the output of the secondary fluxgate probe more accurately represents the background magnetic field in the measurement environment.

[0097] Specifically, under the condition that the external background magnetic field remains unchanged, the first compensation current I1 and the second compensation current I2 can be changed respectively, the change in the demodulated output signal Va of the sub-probe can be recorded, and the corresponding crosstalk coefficient can be determined according to the relationship between Va and I1 and I2. During the measurement process, the coupled magnetic field components generated by the background compensation coil and the feedback coil are eliminated from the demodulated output signal Va of the sub-probe according to the crosstalk coefficient.

[0098] In one triaxial measurement implementation, the system includes three sets of primary and secondary fluxgate probes, each set corresponding to a sensitive axis direction, used to measure the magnetic field components in the X, Y, and Z axes, respectively. The data acquisition and processing module calculates the background magnetic field components B0x, B0y, and B0z and the residual magnetic field components B1x, B1y, and B1z in the three directions, and obtains the final magnetic field components Bx, By, and Bz in the three directions, where:

[0099] Bx = B0x + B1x;

[0100] By = B0y + B1y;

[0101] Bz = B0z + B1z;

[0102] Finally, the measured triaxial magnetic field vector is expressed as:

[0103] B = (Bx, By, Bz).

[0104] The calibration coefficients corresponding to the three directions are calibrated with signs according to the positive direction of the probe's sensitive axis, the winding direction of the compensation coil, and the positive direction of the compensation current, so that Bx, By, and Bz are all represented according to the pre-established three-axis coordinate system.

[0105] Using the above method, background magnetic field detection and pre-compensation, along with precise measurement of residual magnetic field at zero flux, are performed in stages. This reduces the impact of the background magnetic field on the dynamic range of the main measurement channel, improves the detection resolution of the main fluxgate probe for weak magnetic field changes, and reduces the dependence on high-bit-to-digital converters.

[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation, characterized in that, It includes a secondary fluxgate probe, a primary fluxgate probe, a secondary probe signal processing module, a primary probe signal processing module, a background magnetic field compensation module, a zero flux feedback loop, and a data acquisition and processing module; The secondary fluxgate probe is used to detect the background magnetic field and output the secondary probe sensing signal. The secondary probe signal processing module is used to process the secondary probe sensing signal and obtain the secondary probe demodulated output signal Va. The background magnetic field compensation module is used to generate a first compensation current I1 based on Va and inject I1 into the background compensation coil located in the area of ​​the main fluxgate probe, so that the background compensation coil generates a compensation magnetic field opposite to the direction of the background magnetic field, so as to perform physical pre-compensation of the background magnetic field in the area before the main fluxgate probe detects. The main fluxgate probe is used to detect the residual magnetic field after pre-compensation and output the main probe sensing signal. The main probe signal processing module is used to process the main probe sensing signal and obtain the main probe demodulated output signal Vm. The zero flux feedback loop is used to generate a second compensation current I2 based on Vm, and input I2 into the feedback coil of the main flux gate probe, so that the feedback coil generates a feedback magnetic field opposite to the direction of the residual magnetic field, so that the main flux gate probe maintains a closed loop state within the preset zero flux balance range. The data acquisition and processing module is used to synchronously acquire Va, Vm, I1 and I2, perform time alignment on the synchronously acquired data, and calculate the measured magnetic field B according to B0=k1·(I1-I10), B1=k2·(I2-I20) and B=B0+B1. Where B0 is the background magnetic field component, B1 is the residual magnetic field component, k1 and k2 are signed calibration coefficients, and I10 and I20 are the zero-point bias of the compensation current.

2. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 1, characterized in that, Both the secondary fluxgate probe and the primary fluxgate probe include a magnetic core, an excitation coil, and an induction coil. The excitation coil is used to apply a periodic alternating excitation signal to the magnetic core, causing the magnetic core to periodically enter forward saturation and reverse saturation states. The induction coil is used to sense the magnetic flux change generated by the magnetic core under the action of an external magnetic field and output the corresponding induction signal. The secondary fluxgate probe and the primary fluxgate probe share the same excitation source, and the secondary probe signal processing module and the primary probe signal processing module use the same source reference signal for synchronous demodulation.

3. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 1, characterized in that, The sensitive axes of the secondary fluxgate probe and the primary fluxgate probe are parallel and spaced apart, so that the background magnetic field detected by the secondary fluxgate probe and the background magnetic field in the area where the primary fluxgate probe is located satisfy the preset spatial correlation, and the coupling magnetic field generated by the background compensation coil and the feedback coil at the secondary fluxgate probe is lower than the preset crosstalk threshold. The preset spatial correlation is determined by synchronously acquiring the background magnetic field of the area where the auxiliary fluxgate probe and the main fluxgate probe are located at different probe spacings, and based on the correlation between the two background magnetic field sampling sequences; the preset crosstalk threshold is determined based on the change in the output signal of the auxiliary fluxgate probe when the background compensation coil and the feedback coil are driven respectively.

4. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 1, characterized in that, The secondary probe signal processing module includes a secondary probe synchronous demodulation circuit, a secondary probe low-noise amplifier circuit, and a secondary probe integration circuit; The secondary probe synchronous demodulation circuit uses the excitation signal as the demodulation reference to extract the effective magnetic field component corresponding to the background magnetic field from the secondary probe sensing signal. The low-noise amplifier circuit of the secondary probe amplifies the demodulated signal, and the integrator circuit of the secondary probe integrates the amplified signal to obtain the demodulated output signal Va of the secondary probe.

5. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 1, characterized in that, The background magnetic field compensation module includes a compensation current generation circuit and a current detection circuit; The compensation current generation circuit is used to generate the first compensation current I1 based on the demodulated output signal Va of the secondary probe, and output I1 to the background compensation coil; the current detection circuit is used to detect the actual I1 flowing through the background compensation coil and feed it back to the data acquisition and processing module. The compensation current generation circuit is a voltage-to-current conversion circuit that converts Va into I1, or it may include an analog-to-digital conversion circuit, a data acquisition and processing module, a digital-to-analog conversion circuit, and a constant current drive circuit. The analog-to-digital conversion circuit is used to convert Va into a digital sampled value, the data acquisition and processing module is used to generate a digital compensation control quantity based on the digital sampled value, and the digital-to-analog conversion circuit and the constant current drive circuit are used to output I1 based on the digital compensation control quantity.

6. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 1, characterized in that, The main probe signal processing module includes a main probe synchronous demodulation circuit, a main probe low-noise amplifier circuit, and a main probe integration circuit. The main probe synchronous demodulation circuit uses the excitation signal as a demodulation reference to extract the effective magnetic field component corresponding to the residual magnetic field from the main probe induced signal. The main probe low-noise amplifier circuit amplifies the demodulated residual magnetic field signal, and the main probe integration circuit integrates the amplified signal to obtain the main probe demodulated output signal Vm.

7. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 6, characterized in that, The amplification factor of the low-noise amplifier circuit of the main probe is greater than that of the low-noise amplifier circuit of the secondary probe, so that the signal processing module of the main probe processes the residual magnetic field signal with a higher gain than that of the signal processing module of the secondary probe after the background magnetic field is pre-compensated.

8. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 1, characterized in that, k1, k2, I10, and I20 are obtained by acquiring the first compensation current I1 and the second compensation current I2 under a known standard magnetic field environment and performing linear fitting, multi-point calibration, or temperature segment calibration; the data acquisition and processing module is also used to correct k1, k2, I10, and I20 based on the temperature data acquired by the temperature sensor. The data acquisition and processing module also stores the crosstalk calibration parameters between the main and auxiliary fluxgate probes, and performs crosstalk correction on the demodulated output signal Va or the first compensation current I1 of the auxiliary probe according to the crosstalk calibration parameters. The crosstalk calibration parameters are used to characterize the coupling effect of the magnetic field generated by the background compensation coil and the feedback coil on the detection result of the auxiliary fluxgate probe.

9. The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation according to claim 1, characterized in that, The data acquisition and processing module synchronously samples Va, Vm, I1, and I2 and performs time alignment so that Va, Vm, I1, and I2 within the same sampling period have the same or convertible time identifier. The data acquisition and processing module is also used to limit I1 and I2. When I1 exceeds the preset first current threshold, it outputs a background compensation range prompt. When I2 exceeds the preset second current threshold, it outputs a zero flux closed-loop status prompt or a closed-loop loss risk prompt.

10. A zero-flux magnetometer measurement method based on primary and secondary dual-probe graded compensation, characterized in that, The zero-flux magnetometer system based on primary and secondary dual-probe hierarchical compensation, as described in any one of claims 1-9, comprises the following steps: S101, activate the main fluxgate probe, the auxiliary fluxgate probe, and the excitation signal; S102, the auxiliary fluxgate probe detects the background magnetic field and outputs the auxiliary probe sensing signal; S103 performs synchronous demodulation, low-noise preamplification, and integration processing on the sub-probe sensing signal to obtain the sub-probe demodulated output signal Va. S104, Generate a first compensation current I1 based on Va, and inject I1 into the background compensation coil located in the area where the main fluxgate probe is located, so that the background compensation coil generates a compensation magnetic field opposite to the direction of the background magnetic field, and performs physical pre-compensation on the background magnetic field in the area where the main fluxgate probe is located. S105, the main fluxgate probe detects the residual magnetic field after pre-compensation and outputs the main probe induction signal; S106 performs synchronous demodulation, low-noise preamplification, and integration processing on the main probe sensing signal to obtain the main probe demodulated output signal Vm. S107, generate a second compensation current I2 according to Vm, and input I2 into the feedback coil of the main fluxgate probe, so that the feedback coil generates a feedback magnetic field opposite to the direction of the residual magnetic field, so that the main fluxgate probe maintains a closed loop state within the preset zero flux balance range. S108 synchronously acquires Va, Vm, I1, and I2, and performs time alignment on the synchronously acquired data; S109, calculate the background magnetic field component B0 according to B0=k1·(I1-I10), and calculate the residual magnetic field component B1 according to B1=k2·(I2-I20), where k1 and k2 are signed calibration coefficients that include the direction of compensation current, coil winding direction, positive direction of probe sensitive axis and signal processing polarity relationship. S110 calculates the measured magnetic field B according to B=B0+B1 and outputs the measurement result.

Images