A phase adjusting and quadrature error self-adapting correction system for fluxgate sensor

Abstract

The application relates to the technical field of fluxgate sensor detection, and discloses a phase adjustment and quadrature error self-adaptive correction system for a fluxgate sensor, which comprises a digital phase shifter, a double-channel demodulation module and a processing unit. The digital phase shifter performs phase shifting on a first reference signal generated by a digital signal synthesizer and having a frequency of twice that of an excitation signal based on a shifted phase, and generates a shifted signal. The double-channel demodulation module demodulates an in-phase direct current component and a quadrature error component. The processing unit is configured to perform the following: when VQ satisfies a preset closed-loop suppression condition and is not zero, a compensation signal is generated and superimposed on a to-be-demodulated signal; when VQ does not satisfy the preset closed-loop suppression condition, an updated locking phase is generated, VQ is detected based on the updated locking phase, and a closed-loop suppression process of the quadrature error component is performed. The application can eliminate the quadrature error, improve the stability of a demodulated direct current signal and the demodulation sensitivity.

Description

Technical Field

[0001] This invention relates to the field of fluxgate sensor detection technology, and in particular to a phase adjustment and orthogonal error adaptive correction system for fluxgate sensors. Background Technology

[0002] A fluxgate magnetometer is a high-precision weak magnetic field measuring device based on the nonlinear magnetization characteristics of a high-permeability iron core in an alternating magnetic field. Its core structure consists of a magnetic core made of a high-permeability soft magnetic material (such as permalloy), an excitation coil, and an induction coil. During operation, a high-frequency alternating current is applied to the excitation coil, causing the magnetic core to periodically enter a saturation state. In the absence of an external magnetic field, the magnetization process of the magnetic core is symmetrical, and the induction coil primarily generates a fundamental signal. When an external magnetic field is present, it modulates the magnetization process of the magnetic core, thereby generating a second harmonic signal in the induction coil that contains information about the measured magnetic field. The amplitude of this signal is proportional to the strength of the measured magnetic field. However, because this second harmonic signal is extremely weak and is overwhelmed by the much stronger excitation signal, it requires signal processing such as phase-sensitive detection for extraction.

[0003] To demodulate the signal under test, a local oscillator reference signal that is strictly synchronized with the second harmonic signal is required, with the two signals having the same frequency and zero phase difference. This local oscillator reference signal needs to be precisely phase-shifted relative to the excitation signal for in-phase demodulation.

[0004] However, due to factors such as core nonlinearity, analog circuit phase shift, temperature drift, and component aging, a dynamically changing, non-zero phase difference Δθ exists between the phase of the second harmonic signal output by the fluxgate sensor and the phase of the local oscillator reference signal generated by the excitation signal. This Δθ causes an error component orthogonal to the useful signal in the demodulation output, specifically manifested as a decrease in demodulation gain and additional zero-point drift, ultimately reducing demodulation sensitivity and causing serious measurement errors.

[0005] Existing traditional solutions often employ fixed RC phase-shifting networks or manually adjustable analog potentiometers. For example, in manual or semi-automatic analog phase-shifting schemes, the circuit typically includes an RC all-pass filter and an LC phase-shifting network. The time constant is changed by manually adjusting the potentiometer, and the phase zero point is found by observing the graph on an oscilloscope. Programmable phase-shifting schemes based on switched capacitors or digital potentiometers use a microcontroller to control the resistance value of the digital potentiometer, achieving coarse and fine phase adjustments. These existing solutions struggle to cover the entire temperature range, and when fluxgate sensor probes age or ambient temperature changes cause the magnetic core's magnetic properties to drift, the phase difference changes accordingly, resulting in a significant zero-point shift in the demodulated DC signal and a decrease in demodulation sensitivity. Summary of the Invention

[0006] The purpose of this invention is to provide a phase adjustment and orthogonal error adaptive correction system for fluxgate sensors. Through closed-loop control, it can accurately determine the phase difference and achieve high-precision and high-stability adaptive phase adjustment of the local oscillator reference signal, thereby adaptively adjusting the orthogonal error. When the phase difference between the second harmonic signal and the local oscillator reference signal approaches 0° in real time, the orthogonal error interference is eliminated at the source, and zero-point drift is suppressed. This helps to improve the stability, demodulation sensitivity and detection accuracy of the demodulated DC signal.

[0007] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0008] This application relates to a phase adjustment and orthogonal error adaptive correction system for a fluxgate sensor, comprising:

[0009] The signal processing module is used to process the fluxgate induction signal output by the fluxgate sensor into a signal to be demodulated.

[0010] A digital phase shifter, which shifts the phase of a first reference signal generated by a digital signal synthesizer at twice the frequency of the excitation signal based on the phase shifted signal, to generate the phase-shifted signal;

[0011] The dual-channel demodulation module includes:

[0012] A phase-sensitive detector receives the signal to be demodulated and the phase-shifted signal, and demodulates the in-phase DC component corresponding to the signal to be demodulated.

[0013] The quadrature error detector receives the signal to be demodulated and an orthogonal reference signal with a phase difference of 90° from the phase-shifted signal, and demodulates the orthogonal error component that is orthogonal to the signal to be demodulated.

[0014] A quadrature reference signal generator that generates the quadrature reference signal based on the phase-shifted signal;

[0015] The processing unit, when using the fluxgate sensor for detection, is configured to perform the following:

[0016] Based on the current locked phase, the phase-shifted signal is the local oscillator reference signal RefI, the in-phase phase-sensitive detector outputs the in-phase DC component VI, and the quadrature error detector outputs the quadrature error component VQ.

[0017] The process of performing closed-loop suppression of the quadrature error component is as follows: when VQ satisfies the preset closed-loop suppression condition and is not zero, a compensation signal with the same amplitude as the quadrature error component VQ and opposite phase to the quadrature reference signal is generated and superimposed on the signal to be demodulated.

[0018] The process of updating the locked phase is as follows: when the quadrature error component VQ does not meet the preset closed-loop suppression condition, the locked phase is updated, and based on the updated locked phase, the quadrature error component VQ is re-detected, and the closed-loop suppression process of the quadrature error component is executed.

[0019] In the locked phase, the local oscillator reference signal is in phase with the signal to be demodulated.

[0020] In some embodiments of this application, the in-phase phase-sensitive detector includes a first multiplier and a first low-pass filter connected in sequence. The first multiplier receives the signal to be demodulated and the phase-shifted signal, and the first low-pass filter outputs a DC component.

[0021] The quadrature error detector includes a second multiplier and a second low-pass filter connected in sequence. The second multiplier receives the signal to be demodulated and the quadrature reference signal, and the second low-pass filter outputs the quadrature error component.

[0022] In some embodiments of this application, the digital signal synthesizer also generates an excitation signal for the excitation coil of the fluxgate sensor.

[0023] In some embodiments of this application, the processing unit includes an orthogonal error suppression module, which includes:

[0024] The first judgment module is used to determine whether the orthogonal error component VQ reaches the preset closed-loop suppression condition.

[0025] The second judgment module is used to determine whether the orthogonal error component VQ is zero when the orthogonal error component VQ reaches the preset closed-loop suppression condition.

[0026] A digital PID controller is configured to: when the quadrature error component VQ is not zero, output a correction value to a controllable cancellation signal source based on the quadrature error component VQ, and control the controllable cancellation signal source to output the compensation signal until VQ is zero.

[0027] In some embodiments of this application, the processing unit further includes a phase update module, which is configured to update the locked phase when the quadrature error component VQ does not meet a preset closed-loop suppression condition, specifically:

[0028] The digital phase shifter uses its resolution as a step size to cyclically fine-tune the initial phase within a preset fine-tuning angle range. After each fine-tuning, the demodulated signal and the quadrature reference signal are input to the quadrature error detector, and the quadrature error component output by the quadrature error detector is detected.

[0029] When the orthogonal error component is detected to meet the preset closed-loop suppression condition, the locked phase is updated using the currently fine-tuned phase.

[0030] In some embodiments of this application, the processing unit is configured to actively or periodically update the locked phase automatically.

[0031] In some embodiments of this application, the processing unit is configured to obtain the initial phase of the locked phase in the following manner:

[0032] The initial phase is initialized to zero;

[0033] The digital phase shifter is controlled to perform cyclic phase shifting within the range of [0°, 360°] with its resolution as the step size. After each phase shift, the demodulated signal and the phase-shifted signal are input to the in-phase phase-sensitive detector, and the in-phase DC component output by the in-phase phase-sensitive detector is detected.

[0034] When the in-phase DC component is detected to reach its maximum value, the current phase shift is locked as the initial phase of the locked phase.

[0035] In some embodiments of this application, the signal detection system further includes:

[0036] In the closed-loop suppression process of the quadrature error component, when the quadrature error component VQ is detected to be zero, the storage unit stores the current locked phase, or the locked phase and the quadrature suppression parameter used to characterize the amplitude of the compensation signal, in the storage unit as the initial phase to be used when the next power-on.

[0037] In some embodiments of this application, when using the fluxgate sensor for detection, the processing unit is further configured to perform the following:

[0038] Call the locked phase, or both the locked phase and the quadrature suppression parameter, from the memory unit;

[0039] The quadrature error component VQ is continuously monitored. When the quadrature error component VQ meets the preset closed-loop suppression condition, the closed-loop suppression process of the quadrature error component is executed using the called locked phase. When the quadrature error component VQ does not meet the preset closed-loop suppression condition, the locked phase is updated, and the closed-loop suppression process of the quadrature error component is executed based on the updated locked phase.

[0040] In some embodiments of this application, the processing unit is configured to update the locked phase when the quadrature error component VQ does not meet a preset closed-loop suppression condition, specifically:

[0041] The digital phase shifter uses its resolution as a step size to cyclically fine-tune the currently locked phase within a preset fine-tuning angle range. After each fine-tuning, the demodulated signal and the quadrature reference signal are input to the quadrature error detector, and the quadrature error component output by the quadrature error detector is detected.

[0042] When the orthogonal error component is detected to meet the preset closed-loop suppression condition, the locked phase is updated using the currently fine-tuned phase.

[0043] The phase adjustment and orthogonal error adaptive correction system for fluxgate sensors proposed in this application has the following advantages and beneficial effects compared with the prior art:

[0044] (1) A dual-channel demodulation module is established to extract the in-phase DC component and the quadrature error component respectively. The quadrature error component is used as a feedback signal to generate a compensation signal to actively cancel the quadrature component in the demodulated signal. The quadrature error component is controlled in a closed loop. The response speed is fast and the suppression ratio is higher than that of the existing passive filtering of quadrature components, which improves the stability and accuracy of the in-phase DC component in the demodulated second harmonic signal.

[0045] (2) Based on real-time continuous detection of quadrature error components, the lock phase is dynamically adjusted so that the local oscillator reference signal is always aligned with the phase of the signal to be demodulated, and the quadrature error components are controlled to approach zero, thereby achieving phase adaptive alignment and improving demodulation accuracy. Moreover, this method of adjusting the lock phase can automatically adapt to drift caused by changes in ambient temperature, probe aging, etc.

[0046] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This invention presents a block diagram illustrating the principle of the phase adjustment and orthogonal error adaptive correction system for fluxgate sensors.

[0049] Figure 2 A flowchart illustrating the closed-loop suppression process of orthogonal error components in the phase adjustment and orthogonal error adaptive correction system for fluxgate sensors proposed in this invention is shown.

[0050] Figure 3The flowchart illustrates the process executed by the orthogonal error suppression module in the phase adjustment and orthogonal error adaptive correction system for the fluxgate sensor proposed in this invention during the closed-loop suppression of the orthogonal error signal.

[0051] Figure 4 This invention presents a flowchart illustrating the phase-locking update process in the phase adjustment and orthogonal error adaptive correction system for fluxgate sensors proposed in this invention.

[0052] Figure 5 The flowchart illustrates the process of obtaining the initial phase of the locked phase in the phase adjustment and orthogonal error adaptive correction system for fluxgate sensors proposed in this invention.

[0053] Figure label:

[0054] 110. Signal processing module; 120. Digital phase shifter; 130. Dual-channel demodulation module; 131. In-phase phase-sensitive detector; 132. Quadrature error detector; 140. Quadrature reference signal generator; 150. Digital signal synthesizer; 160. Processing unit; 161. Quadrature error suppression module; 162. Phase update module. Detailed Implementation

[0055] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0056] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0057] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0058] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0059] In order to improve demodulation sensitivity and reduce measurement error when using a fluxgate sensor for weak magnetic field measurement, this application proposes a phase adjustment and orthogonal error adaptive correction system for a fluxgate sensor. By detecting the orthogonal error component in real time and performing closed-loop control, the system accurately determines the phase difference Δθ between the second harmonic signal and the local oscillator reference signal, and achieves high-precision and high-stability adaptive phase shifting of the local oscillator reference signal, so that the phase difference Δθ between the two signals tends to zero. With phase adjustment, the orthogonal error interference is adaptively eliminated, thereby improving the signal demodulation accuracy and measurement accuracy.

[0060] Figure 1 The schematic diagram of the phase adjustment and orthogonal error adaptive correction system for the fluxgate sensor is shown.

[0061] The fluxgate sensor phase adjustment and orthogonal error adaptive correction system includes a signal processing module 110, a digital phase shifter 120, a digital signal synthesizer 150, a dual-channel demodulation module 130, an orthogonal reference signal generator 140, and a processing unit 160.

[0062] Combination Figures 1 to 5 This paper describes the working principle of the phase adjustment and orthogonal error adaptive correction system for the fluxgate sensor.

[0063] The signal processing module 110 processes the fluxgate induction signal output by the fluxgate sensor into a demodulated signal. The excitation signal is fed into the excitation coil of the fluxgate sensor, causing the magnetic core to periodically enter a saturation state. When an external magnetic field is present, it modulates the magnetization process of the magnetic core, thereby generating a fluxgate induction signal (including the second harmonic signal) containing information about the measured magnetic field in the induction coil of the fluxgate sensor.

[0064] The second harmonic signal is relatively weak. Therefore, before subsequent demodulation, it can be pre-amplified and bandpass filtered to obtain a signal suitable for demodulation. Thus, the signal processing module 110 can include a differential amplifier and a bandpass filter. The differential amplifier amplifies the second harmonic signal differentially to improve the signal-to-noise ratio. The bandpass filter can be selected with a center frequency twice the excitation signal frequency to initially screen out the second harmonic components, i.e., the signal to be demodulated is a valid second harmonic component.

[0065] In some embodiments of this application, the digital signal synthesizer 150 is controlled to output two co-source signals: an excitation signal with frequency f (denoted as f(φ)) and a first reference signal with a frequency twice that of the excitation signal (denoted as 2f(φ)), wherein the phase φ of the excitation signal and the first reference signal is adjustable and in phase.

[0066] For ease of description, φ is adjusted to 0°. Therefore, the excitation signal is denoted as f(0°) and the first reference signal is denoted as 2f(0°).

[0067] The digital phase shifter 120 receives a phase shift command and shifts the phase of the signal. In some embodiments of this application, the digital phase shifter 120 receives a first reference signal 2f(0°) output by the digital signal synthesizer 150, shifts the first reference signal based on the shifted phase θ, and generates the phase-shifted signal (denoted as 2f(θ)).

[0068] In this application, the digital phase shifter 120 receives a first reference signal 2f(0°), based on the shifted phase θ being the locked phase θ. opt The first reference signal is phase-shifted to generate a local oscillator reference signal RefI (denoted as 2f(θ)) with a phase difference of 0° from the signal to be demodulated and a frequency of 2f. opt That is, locking the phase θ. opt The signal to be demodulated and the local oscillator reference signal are in phase.

[0069] The dual-channel demodulation module 130 includes an in-phase phase-sensitive detector 131 and a quadrature error detector 132. The in-phase phase-sensitive detector 131 is used to demodulate and extract the in-phase DC component of the corresponding second harmonic signal, and the quadrature error detector 132 is used to demodulate and extract the quadrature error component that is orthogonal to the second harmonic signal. The quadrature error component will affect the demodulation sensitivity of the second harmonic signal and the measurement accuracy of the fluxgate sensor.

[0070] In some embodiments of this application, the in-phase phase-sensitive detector 131 includes a first multiplier (unlabeled) and a first low-pass filter (unlabeled) connected in sequence. The first multiplier is connected to a digital phase shifter 120 and receives the phase-shifted signal 2f(θ) output by the digital phase shifter 120 and the signal to be demodulated. After multiplication, the signal to be demodulated is demodulated into a DC component, while other frequency components remain AC signals. The first low-pass filter receives the output of the first multiplier, filters out all AC components, and retains only the DC output related to the measured magnetic field.

[0071] In order to extract the quadrature error component that is orthogonal to the signal to be demodulated, the quadrature reference signal generator 140 receives the phase-shifted signal 2f(θ) output by the digital phase shifter 120 and generates a quadrature reference signal 2f(θ+90°) with a frequency of 2f and a phase difference of 90°.

[0072] Similar to the structure of the in-phase phase-sensitive detector 131, the quadrature error detector 132 includes a second multiplier (unlabeled) and a second low-pass filter (unlabeled) connected in sequence. The second multiplier receives the signal to be demodulated and the quadrature reference signal 2f(θ+90°). After multiplication, the quadrature error component is demodulated into a DC component, while other frequency components remain AC signals. The second low-pass filter receives the output of the second multiplier, filters out all AC components, and retains only the DC output related to the quadrature error component.

[0073] In some embodiments of this application, in order to reliably demodulate the signal to be demodulated, the processing unit 160 performs the following process.

[0074] (1) The phase of the local oscillator reference signal is locked. Under the locked phase, the local oscillator reference signal is in phase with the signal to be demodulated, and the quadrature error detector 132 outputs the quadrature error component VQ.

[0075] (2) When VQ satisfies the preset closed-loop suppression condition and is not zero, the closed-loop suppression process of the orthogonal error component VQ is entered. During this process, a compensation signal V is actively generated based on the orthogonal error component VQ. cancel The negative feedback is then superimposed onto the signal to be demodulated to actively cancel the quadrature error component in the output signal of the fluxgate sensor probe. See [link to relevant documentation]. Figure 2 .

[0076] It should be noted that VQ is a controlled variable, and its tendency to zero can be considered as zero.

[0077] (3) If, during the closed-loop suppression process, the quadrature error component VQ is not controlled to approach zero by the closed loop, but instead increases to the point where the preset closed-loop suppression condition is not met, it indicates that the current locked phase can no longer ensure that the phase difference between the demodulated signal and the local oscillator reference signal is zero. Therefore, a phase update process is required at this time. During this phase update process, the locked phase is updated based on the quadrature error component VQ until VQ meets the preset closed-loop suppression condition. Then, the closed-loop suppression process of the quadrature error component VQ is executed again. See [link to relevant documentation]. Figure 3 .

[0078] The locked phase has an initial phase. When updating, the initial phase is changed to obtain a new phase value as the locked phase. However, no matter how it is updated, the local oscillator reference signal remains in phase with the signal to be demodulated under the locked phase.

[0079] The implementation of the above specific processes Figures 1 to 3 The description is as follows.

[0080] See Figure 1 When using a fluxgate sensor for detection, based on the locked phase θ optThe digital phase shifter 120 generates the native oscillator reference signal 2f(θ). opt The quadrature reference signal generator 140 receives the local oscillator reference signal 2f(θ). opt (Also denoted as RefI), generating an orthogonal reference signal 2f(θ) opt +90° (also denoted as RefQ).

[0081] For example, RefI=sin(2π·2f·t +θ) opt ),RefQ=cos(2π·2f·t +θ opt ).

[0082] The in-phase phase-sensitive detector 131 receives the local oscillator reference signal 2f(θ). opt The quadrature error detector 132 receives the quadrature reference signal 2f(θ) and the signal to be demodulated, and outputs the in-phase DC component VI; the quadrature error detector 132 receives the quadrature reference signal 2f(θ). opt +90°) and the signal to be demodulated, outputting the quadrature error component VQ.

[0083] Figure 2 A flowchart illustrating the closed-loop suppression process of the orthogonal error signal is shown. Figure 3 The flowchart shows the process executed by the orthogonal error suppression module 161 when performing closed-loop suppression of the orthogonal error signal.

[0084] In some embodiments of this application, see Figure 1 and Figure 2 The core of the closed-loop suppression process of the orthogonal error component VQ is executed by the orthogonal error suppression module 161.

[0085] The orthogonal error suppression module 161 includes a first judgment module (not shown), a second judgment module (not shown), and a digital PID controller (not shown).

[0086] In some embodiments of this application, in order to accurately control the orthogonal error component VQ, when VQ satisfies the preset closed-loop suppression condition and is not zero, an actively generated compensation signal V is used. cancel The quadrature error component VQ is controlled. If the quadrature error component VQ gradually increases to the point that it no longer meets the preset closed-loop suppression condition, it means that the current locked phase cannot satisfy the local oscillator reference signal and the demodulated signal to be in phase, and needs to be updated.

[0087] In some embodiments of this application, a preset closed-loop suppression condition can be set for VQ.

[0088] The preset closed-loop suppression condition can be a range of values ​​or a specific value. For example, the preset closed-loop suppression condition is that VQ reaches the lower limit of the preset value, which can be selected as 5%FS (Full Scale).

[0089] The lower limit of VQ reaching the preset value can be represented as VQ < 5%FS or VQ ≤ 5%FS.

[0090] For clarity, the lower limit for VQ to reach the preset value is described as VQ < 5%FS.

[0091] In some embodiments of this application, the first judgment module is used to determine whether the orthogonal error component VQ in S21 satisfies a preset closed-loop condition (e.g., whether VQ is less than 5%FS). If so, the closed-loop suppression process is initiated, and a compensation signal V is generated. cancel This is used to control the orthogonal error component VQ, in order to counteract the orthogonal error component.

[0092] During the closed-loop suppression process, the quadrature error component VQ is detected in real time. The second judgment module is used to determine whether the quadrature error component VQ is equal to zero. If VQ is zero, it means that the local oscillator reference signal and the demodulated signal have reached a precise in-phase relationship, and the influence of the quadrature error component interference has been completely eliminated. At this time, the closed-loop suppression process control ends, and the stable, quadrature error-eliminated in-phase DC component VI can be digitally output. If VQ is not zero, the closed-loop suppression process is executed cyclically.

[0093] The above closed-loop suppression process is implemented using a digital PID controller.

[0094] In some embodiments of this application, when it is determined that VQ < 5%FS and VQ is not zero, the process proceeds to S23 to generate a compensation signal V with the same amplitude as the quadrature error component VQ and opposite phase to the quadrature reference signal. cancel Then, the negative feedback is superimposed onto the signal to be demodulated at S24.

[0095] After being superimposed onto the signal to be demodulated, the quadrature error component VQ is detected in step S25. The second judgment module is used to determine whether the quadrature error component VQ is equal to zero in step S26. If VQ is not zero, the closed-loop suppression process is executed cyclically.

[0096] In some embodiments of this application, the digital PID controller is the core unit for performing the closed-loop suppression process.

[0097] Figure 4 The generated compensation signal V is shown. cancel The flowchart.

[0098] See Figure 4 The digital PID controller receives the magnitude and positive / negative polarity of the quadrature error component VQ (see [reference]). Figure 4 (S231), and calculate the correction amount based on the magnitude of VQ and the positive / negative polarity (see S231). Figure 4 (S232), then, the correction amount is output to the controllable cancellation signal source (see S232). Figure 4(S233), and based on this correction amount, control the output compensation signal V of the controllable cancellation signal source. cancel (See) Figure 4 S234), used for compensation control VQ, wherein the compensation signal V cancel It has the same amplitude as the quadrature error component VQ and the opposite phase to the quadrature reference signal RefQ.

[0099] In some embodiments of this application, during the above-described closed-loop suppression process, refer back to [link to previous document]. Figure 2 If the preset closed-loop suppression condition is not met (for example, VQ≥5%FS is detected), it indicates that a phase drift problem may have occurred due to factors such as rising ambient temperature or aging of the fluxgate sensor probe. Therefore, the locked phase needs to be updated.

[0100] After completing the locked phase update, the orthogonal error component VQ is re-detected using the newly updated locked phase, and then the closed-loop suppression process is performed.

[0101] In some embodiments of this application, see Figure 1 The locked phase can be updated using the phase update module 162.

[0102] For ease of description, the current locked phase is denoted as θ. opt .

[0103] Figure 4 A flowchart describing the locked phase update process is shown.

[0104] Generally, when phase drift occurs, there will not be a large fluctuation based on the current locked phase. Therefore, a preset fine-tuning angle range (e.g., [-5°, 5°]) can be set based on experience to fine-tune based on the current locked phase, reducing time and computational costs.

[0105] See Figure 4 It specifically describes the process of updating the locked phase.

[0106] S41: The digital phase shifter 120 uses its resolution as a step size to cyclically fine-tune the currently locked phase within a preset fine-tuning angle range.

[0107] In some embodiments of this application, the digital phase shifter 120 employs a high-precision digital phase shifter with a resolution selectable to be 0.01°.

[0108] After each fine-tuning, the phase becomes θ. opt =θ opt ±0.01.

[0109] S42: Detect the orthogonal error component VQ.

[0110] At this phase θopt See below. Figure 1 The orthogonal error component VQ is re-detected.

[0111] S43: Determine whether VQ has reached the preset closed-loop suppression condition. If yes, proceed to S44; otherwise, return to S41.

[0112] S44: Lock the currently fine-tuned phase, and then execute the closed-loop suppression process.

[0113] Meeting the preset closed-loop inhibition condition means meeting the VQ condition required to enter the closed-loop inhibition process; for example, VQ < 5%FS. Afterward, the closed-loop inhibition process can be used to control VQ to approach zero, specifically in conjunction with... Figure 2 and Figure 3 See the content mentioned above.

[0114] In this way, by detecting the quadrature error component VQ in real time, the phase of the local oscillator reference signal is adaptively and precisely controlled, so that the phase difference between the local oscillator reference signal and the signal to be demodulated is zero, the quadrature error component is eliminated, and the stability, accuracy and measurement results of the demodulated DC component are improved.

[0115] In order to use and update the locked phase, an initial phase is set for the locked phase. When the fluxgate sensor is initially used normally, the initial phase is used for the closed-loop suppression process. Then, during the phase update process, the initial phase is updated.

[0116] In some embodiments of this application, a cyclic scanning optimization method is used to obtain the initial phase. Figure 5 The flowchart shows the process of obtaining the initial phase through a cyclic scanning optimization method.

[0117] See Figure 5 This describes the scanning optimization process for the specific initial phase θ0.

[0118] S51: Initialize the initial phase θ0=0 and Vmax=0.

[0119] Initial conditions are set for subsequent iterative updates, after which the cyclic scanning process begins.

[0120] S52: Control the digital phase shifter 120 to shift the first reference signal by phase θ0.

[0121] The digital phase shifter 120 shifts the first reference signal 2f (0°) based on the shifted phase θ0 to generate the phase-shifted signal (denoted as 2f(θ0)).

[0122] S53: Input the demodulated signal and the phase-shifted signal to the in-phase phase-sensitive detector 131, and detect the DC voltage Vout output by the in-phase phase-sensitive detector 131.

[0123] To find that the phase of the phase-shifted signal is aligned with the phase of the demodulated signal, it is necessary to determine whether the DC voltage Vout of the demodulated output has reached its maximum value. Therefore, before determining Vout, it is necessary to detect the DC voltage Vout.

[0124] S54: Determine if Vout is greater than Vmax. If yes, proceed to S55; otherwise, return to S6.

[0125] According to the phase-locked loop principle, when the demodulated output DC voltage out reaches its maximum value, it indicates that the local oscillator reference signal and the demodulated signal have achieved phase alignment (i.e., in phase).

[0126] S55: Record the current phase shift θ0, and update Vmax=Vout at the same time.

[0127] S56: Controls the digital phase shifter 120 to fine-tune the current phase shift θ0 in steps with its resolution.

[0128] In some embodiments of this application, the digital phase shifter 120 employs a high-precision digital phase shifter with a resolution selectable to be 0.01°.

[0129] Therefore, the phase shift after each fine-tuning is: θ0 = θ0 + 0.01.

[0130] S57: Determine if θ0 is greater than or equal to 360°. If yes, proceed to S58; otherwise, return to S52.

[0131] The digital phase shifter 120 is controlled to perform cyclic scanning phase shifting within the range of [0°, 360°], so the phase shifted will not exceed 360°.

[0132] S58: Lock phase θ0 as the initial phase.

[0133] Thus, by using this cyclic scanning optimization method to find the initial phase, the static phase error caused by probe asymmetry or circuit delay is eliminated.

[0134] In some embodiments of this application, in order to facilitate the use and quick activation of the fluxgate sensor, the fluxgate sensor phase adjustment and orthogonal error adaptive correction system further includes a storage unit (not shown), which is a non-volatile memory that stores the locked phase, or the locked phase and the orthogonal suppression parameter used to characterize the amplitude of the compensation signal, in the storage unit.

[0135] These parameters will be quickly invoked and used the next time the fluxgate sensor is started.

[0136] The quadrature suppression parameter described above can be the correction amount G that the digital PID controller dynamically outputs based on the magnitude of VQ and the positive / negative polarity, and enables the controllable cancellation signal source to output a compensation signal V. cancel =G·VQ·cos(2π·2f·t +θ opt +180°), where 180° represents the compensation signal V. cancel It is opposite in phase to RefQ.

[0137] In some embodiments of this application, when using a fluxgate sensor for measurement, the phase-locked phase is first invoked to perform the closed-loop suppression process of the orthogonal error components as described above. Then, when the orthogonal error components fail to meet the preset closed-loop suppression conditions, the phase-locked phase is updated. The process of updating the phase is as described above and will not be repeated here.

[0138] The phase adjustment and orthogonal error adaptive correction system for fluxgate sensors disclosed in this application can actively and dynamically generate compensation signals to cancel the orthogonal error components through closed-loop control of the orthogonal error components, thereby eliminating the interference of the orthogonal error components on the effective second harmonic signal. Furthermore, based on the orthogonal error components, the system adaptively adjusts the phase of the local oscillator reference signal in a closed loop, thereby compensating for phase errors caused by circuit asymmetry and component changes in real time and automatically. This achieves phase alignment between the local oscillator reference signal and the signal to be demodulated, greatly suppressing zero-point drift from the root cause and improving demodulation accuracy and measurement results.

[0139] Furthermore, the phase lock can be periodically or actively calibrated to compensate for temperature drift issues, overcoming the shortcomings of manual calibration or fixed parameter schemes. This phase update method can also adapt to parameter drift caused by changes in ambient temperature and probe aging, achieving phase alignment between the local oscillator reference signal and the demodulated signal across the entire operating temperature range without manual intervention.

[0140] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A phase adjustment and orthogonal error adaptive correction system for a fluxgate sensor, characterized in that, include: The signal processing module is used to process the fluxgate induction signal output by the fluxgate sensor into a signal to be demodulated. A digital phase shifter shifts the phase of a first reference signal generated by a digital signal synthesizer, whose frequency is twice the frequency of the excitation signal, based on the phase shifted phase, to generate the phase-shifted signal. The dual-channel demodulation module includes: A phase-sensitive detector receives the signal to be demodulated and the phase-shifted signal, and demodulates the in-phase DC component corresponding to the signal to be demodulated. The quadrature error detector receives the signal to be demodulated and an orthogonal reference signal with the same frequency and a 90° phase difference from the phase-shifted signal, and demodulates the orthogonal error component that is orthogonal to the signal to be demodulated. A quadrature reference signal generator that generates the quadrature reference signal based on the phase-shifted signal; The processing unit is configured to perform the following: Based on the current locked phase, the phase-shifted signal is the local oscillator reference signal RefI. The in-phase phase-sensitive detector outputs the in-phase DC component VI, and the quadrature error detector outputs the quadrature error component VQ. The process of performing closed-loop suppression of the quadrature error component is as follows: when VQ satisfies the preset closed-loop suppression condition and is not zero, a compensation signal with the same amplitude as the quadrature error component VQ and opposite phase to the quadrature reference signal is generated and superimposed on the signal to be demodulated. The lock phase update process is as follows: when VQ does not meet the preset closed-loop suppression condition, the lock phase is updated, and based on the updated lock phase, the quadrature error component VQ is re-detected, and the closed-loop suppression process of the quadrature error component is executed. In the locked phase, the local oscillator reference signal is in phase with the signal to be demodulated.

2. The phase adjustment and orthogonal error adaptive correction system according to claim 1, characterized in that, The in-phase phase-sensitive detector includes a first multiplier and a first low-pass filter connected in sequence. The first multiplier receives the signal to be demodulated and the phase-shifted signal, and the first low-pass filter outputs a DC component. The quadrature error detector includes a second multiplier and a second low-pass filter connected in sequence. The second multiplier receives the signal to be demodulated and the quadrature reference signal, and the second low-pass filter outputs the quadrature error component.

3. The phase adjustment and orthogonal error adaptive correction system according to claim 1, characterized in that, The digital signal synthesizer also generates an excitation signal for the excitation coil of the fluxgate sensor.

4. The phase adjustment and orthogonal error adaptive correction system according to claim 1, characterized in that, The processing unit includes an orthogonal error suppression module, which includes: The first judgment module is used to determine whether the orthogonal error component VQ reaches the preset closed-loop suppression condition. The second judgment module is used to determine whether the orthogonal error component VQ is zero when the orthogonal error component VQ reaches the preset closed-loop suppression condition. A digital PID controller is configured to: when the second judgment module determines that the quadrature error component VQ is not zero, output a correction amount to the controllable cancellation signal source based on the quadrature error component VQ, and control the controllable cancellation signal source to output the compensation signal until VQ is zero.

5. The phase adjustment and orthogonal error adaptive correction system according to claim 1, characterized in that, The processing unit further includes a phase update module, which is configured to update the locked phase when the quadrature error component VQ does not meet a preset closed-loop suppression condition. Specifically: The digital phase shifter uses its resolution as a step size to cyclically fine-tune the currently locked phase within a preset fine-tuning angle range. After each fine-tuning, the demodulated signal and the quadrature reference signal are input to the quadrature error detector, and the quadrature error component output by the quadrature error detector is detected. When the orthogonal error component is detected to meet the preset closed-loop suppression condition, the locked phase is updated using the currently fine-tuned phase.

6. The phase adjustment and orthogonal error adaptive correction system according to claim 1 or 5, characterized in that, The processing unit is configured to actively or periodically update the locked phase automatically.

7. The phase adjustment and orthogonal error adaptive correction system according to claim 1, characterized in that, The processing unit is configured to obtain the initial phase of the locked phase in the following manner: The initial phase is initialized to zero; The digital phase shifter is controlled to perform cyclic phase shifting within the range of [0°, 360°] with its resolution as the step size, and after each phase shift, the demodulated signal and the phase-shifted signal are input to the in-phase phase-sensitive detector, and the in-phase DC component output by the in-phase phase-sensitive detector is detected. When the in-phase DC component is detected to reach its maximum value, the current phase shift is locked as the initial phase of the locked phase.

8. The phase adjustment and orthogonal error adaptive correction system according to claim 1, characterized in that, The phase adjustment and orthogonal error adaptive correction system for the fluxgate sensor also includes: In the closed-loop suppression process of the quadrature error component, when the quadrature error component VQ is detected to be zero, the storage unit stores the current locked phase, or the locked phase and the quadrature suppression parameter used to characterize the amplitude of the compensation signal, in the storage unit as the initial phase to be used on the next power-on.

9. The phase adjustment and orthogonal error adaptive correction system according to claim 8, characterized in that, When using the fluxgate sensor for detection, the processing unit is also configured to perform the following: Call the locked phase, or both the locked phase and the quadrature suppression parameter, in the memory cell; The quadrature error component VQ is continuously monitored. When the quadrature error component VQ meets the preset closed-loop suppression condition, the closed-loop suppression process of the quadrature error component is executed using the called locked phase. When the quadrature error component VQ does not meet the preset closed-loop suppression condition, the locked phase is updated, and the closed-loop suppression process of the quadrature error component is executed based on the updated locked phase.

10. The phase adjustment and orthogonal error adaptive correction system according to claim 9, characterized in that, The processing unit is configured to update the locked phase when the quadrature error component VQ does not meet the preset closed-loop suppression condition, specifically: The digital phase shifter uses its resolution as a step size to cyclically fine-tune the initial phase within a preset fine-tuning angle range. After each fine-tuning, the demodulated signal and the quadrature reference signal are input to the quadrature error detector, and the quadrature error component output by the quadrature error detector is detected. When the orthogonal error component is detected to meet the preset closed-loop suppression condition, the locked phase is updated using the currently fine-tuned phase.

Images