Compensation and reset integrated measurement method for superconducting-magnetoresistance composite magnetic sensor

Abstract

The invention discloses a compensation and reset integrated measurement method for a superconducting-magnetoresistance composite magnetic sensor. The compensation and reset integrated measurement method comprises the following steps: acquiring a difference value e between an output signal V of the superconducting-magnetoresistance composite magnetic sensor and a zero-point voltage V0, and calculating a compensation current I; if the compensation current I is within the threshold range, generating a feedback compensation magnetic field Bc by using the compensation current I to counteract the change of the external magnetic field so that the sensor always works near the zero magnetic field B0, and calculating a measured value B of the measured magnetic field Bx according to B = B0 + f (I) by combining a compensation function f (I); otherwise, resetting the superconducting-magnetoresistance composite magnetic sensor to be close to the zero working point, and updating the zero magnetic field B0 according to B0 = B0 + f (I). The invention aims to solve the problems that the measuring range of a superconducting-magnetoresistance composite magnetic sensor is limited and accumulative measurement errors are introduced in the existing method, and wide-range and high-resolution measurement of weak magnetic field signals is realized.

Description

Technical Field

[0001] The present invention relates to the field of weak magnetic field signal detection, and particularly to a compensation and reset integrated measurement method for a superconducting-magnetoresistive composite magnetic sensor. Background Art

[0002] In the field of weak signal detection, weak magnetic field detection based on magnetic sensors is a very important research topic. With the development of modern technology, various new weak magnetic field detection requirements have gradually emerged, posing new requirements for the performance of magnetic sensors. Miniaturized high-sensitivity (pT level or even fT level) magnetic sensors have shown important application values in biological magnetic field measurement, underwater target detection, etc. due to their high resolution and small size. Traditional high-sensitivity magnetic sensors such as superconducting quantum interference devices and atomic magnetometers have deficiencies such as large volume and harsh magnetic shielding environment, which limit their application scenarios. The superconducting-magnetoresistive composite magnetic sensor can achieve ultra-high resolution in the fT order of magnitude by using the magnetic field gain of thousands of times of the superconducting magnetic amplifier. However, the measurement range of the superconducting-magnetoresistive composite magnetic sensor is only about 10 μT, and it is easy to saturate in the geomagnetic field environment or when the external magnetic field changes greatly. The existing methods for expanding the measurement range of the superconducting-magnetoresistive composite magnetic sensor mainly reset the working point of the sensor by applying a pulsed magnetic field. However, due to the influence of the nonlinearity of the sensor itself, this method will introduce a large cumulative measurement error. Summary of the Invention

[0003] The technical problem to be solved by the present invention: In view of the above problems of the prior art, a compensation and reset integrated measurement method for a superconducting-magnetoresistive composite magnetic sensor is provided. The present invention aims to solve the problems of the limited measurement range of the superconducting-magnetoresistive composite magnetic sensor and the cumulative measurement error introduced by the existing methods, and realizes wide-range and high-resolution measurement of weak magnetic field signals.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A compensation and reset integrated measurement method for a superconducting-magnetoresistive composite magnetic sensor, comprising the following steps: obtaining the output signal of the superconducting-magnetoresistive composite magnetic sensor under the action of the measured magnetic field B x ; calculating the difference between the output signal V and the zero-point voltage V 0 V ; calculating the compensation current e through a closed-loop controller I ; judging whether the compensation current I satisfies I min < I < I max ; if it is satisfied, controlling the current generator to generate the compensation current IAnd a feedback compensation magnetic field is generated for the superconducting-magnetoresistive composite magnetic sensor through the excitation coil B c to offset the change of the external magnetic field so that the superconducting-magnetoresistive composite magnetic sensor always works in a zero magnetic field B near 0, and according to B = B 0+ f ( I ) the measured magnetic field to be measured is obtained B x measurement value B ; Otherwise, control the current generator to generate a pulse reset current and generate a pulse reset magnetic field for the superconducting-magnetoresistive composite magnetic sensor through the excitation coil to reset the superconducting-magnetoresistive composite magnetic sensor to near the zero working point, and after stabilization, according to B 0= B 0+ f ( I ) update the zero magnetic field B 0; Wherein I min and I max are respectively the minimum value and the maximum value of the compensation current I , B 0 is the zero magnetic field, f ( I ) is the preset compensation amount based on the compensation current I , B r is the saturation magnetic field of the superconducting-magnetoresistive composite magnetic sensor

[0005] Optionally, the function expression of the preset compensation amount based on the compensation current I is: f ( I )= I × k , wherein k is the excitation coefficient of the excitation coil

[0006] Optionally, the zero-point voltage V 0 is the initial output voltage of the superconducting-magnetoresistive composite magnetic sensor and is equal to the output voltage after each working point reset of the superconducting-magnetoresistive composite magnetic sensor

[0007] Optionally, before obtaining the output signal B x of the superconducting-magnetoresistive composite magnetic sensor under the action of the measured magnetic field V , it also includes calibrating the minimum value I of the compensation current I minand the maximum value I max and the saturation magnetic field B r : Apply a vertical magnetic field to the superconducting-magnetoresistive composite magnetic sensor, test the magnetic field-output voltage loop curve of the superconducting-magnetoresistive composite magnetic sensor under vertical magnetic fields of different magnitudes, and determine the saturation magnetic field according to the saturation region in the magnetic field-output voltage loop curve B r , the maximum output voltage value V max and the minimum output voltage value V min ; Calculate the compensation current according to the following formula I the minimum value of I min and the maximum value I max : I max =( V max - V 0) / S / k , I min =( V min - V 0) / S / k , where V 0 is the zero-point voltage, S is the sensitivity of the superconducting-magnetoresistive composite magnetic sensor, and the sensitivity refers to the change value of the output voltage of the superconducting-magnetoresistive composite magnetic sensor under the change of unit external magnetic field, k is the excitation coefficient of the excitation coil

[0008] Optionally, the pulsed reset magnetic field includes magnetic fields in three stages: the magnetic field in the first stage is to apply a reverse magnetic field B r equal to the saturation magnetic field to the superconducting-magnetoresistive composite magnetic sensor, so that the superconducting-magnetoresistive composite magnetic sensor is reversely saturated at this time; the magnetic field in the second stage is to apply a forward magnetic field B r equal to half of the saturation magnetic field B r to the superconducting-magnetoresistive composite magnetic sensor B r / 2, so that the superconducting-magnetoresistive composite magnetic sensor reaches forward saturation at this time; the magnetic field in the third stage is to cancel the magnetic field applied to the superconducting-magnetoresistive composite magnetic sensor by the excitation coil, so that the superconducting-magnetoresistive composite magnetic sensor is reset to near the zero working point.

[0009] Optionally, the durations of the magnetic fields in the three stages are equal.

[0010] Optionally, the durations of the magnetic fields in the three stages are all 10 ms, so that the total duration of the pulsed reset magnetic field is 30 ms.

[0011] Optionally, the closed-loop controller uses a closed-loop control algorithm as a PID solver.

[0012] Optionally, the value of the proportional parameter P used by the PID solver is 0.5, and the value of the integral parameter I is 0.01.

[0013] Optionally, the closed-loop controller is an ARM processor.

[0014] Compared with the prior art, the present invention can mainly achieve the following beneficial effects: The present invention uses a compensation magnetic field to keep the working point of the composite sensor unchanged, which can effectively improve the linearity of the sensor; at the same time, when the compensation magnetic field is large, a reset is performed in a timely manner to synchronize the compensation current and the working point of the sensor to zero, thereby expanding the magnetic field measurement range of the superconducting-magnetoresistive composite magnetic sensor, and having the advantages of wide range, high resolution, high linearity, and low power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the principle of the method according to the embodiment of the present invention.

[0016] Figure 2 It is the normal saturation output voltage curve of the superconducting-magnetoresistive composite magnetic sensor according to the embodiment of the present invention.

[0017] Figure 3 It is a schematic diagram of the pulsed reset magnetic field of the superconducting-magnetoresistive composite magnetic sensor according to the embodiment of the present invention.

[0018] Figure 4 It is the external magnetic field-compensation magnetic field curve of the superconducting-magnetoresistive composite magnetic sensor according to the embodiment of the present invention.

[0019] Figure 5 It is the external magnetic field-reset magnetic field curve of the superconducting-magnetoresistive composite magnetic sensor according to the embodiment of the present invention.

[0020] Figure 6 It is the external magnetic field-measurement result curve of the superconducting-magnetoresistive composite magnetic sensor according to the embodiment of the present invention.

[0021] Figure 7Measurement results before compensation and reset integration according to embodiments of the present invention.

[0022] Figure 8 Measurement results after compensation and reset integration according to embodiments of the present invention. Detailed implementation manners

[0023] In order to enable those skilled in the art of this technology to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0024] As Figure 1 shown, the compensation and reset integration measurement method for the superconducting-magnetoresistive composite magnetic sensor in this embodiment includes the following steps: S101. Obtain the output signal of the superconducting-magnetoresistive composite magnetic sensor under the action of the measured magnetic field B x and calculate the difference between the output signal V and the zero-point voltage V 0, and calculate the compensation current V through the closed-loop controller; e I I ; S102. If I min < I < I max holds, then control the current generator to generate the compensation current I and generate a feedback compensation magnetic field for the superconducting-magnetoresistive composite magnetic sensor through the excitation coil B c to offset the change in the external magnetic field so that the superconducting-magnetoresistive composite magnetic sensor always operates near the zero magnetic field B 0, and calculate the measured value B = B 0 + f ( I ) to obtain the measured value B x of the measured magnetic field B ; S103. If I min < I < I max does not hold, then control the current generator to generate a pulse reset current and generate a pulse reset magnetic field for the superconducting-magnetoresistive composite magnetic sensor through the excitation coil to reset the superconducting-magnetoresistive composite magnetic sensor to near the zero working point, and after stabilization, update the zero magnetic field B 0 = B 0 + f ( I ) according to B0; Wherein, I min and I max are respectively the minimum value and the maximum value of the compensation current I , 0 is the zero - point magnetic field, B 0 is the zero - point magnetic field, f ( I ) is the preset compensation amount based on the compensation current I , B r is the saturation magnetic field of the superconducting - magnetoresistive composite magnetic sensor.

[0025] The compensation function of the compensation current I can adopt the required mapping method according to actual needs. For example, as an optional implementation manner, in this embodiment, a linear mapping is adopted. The function expression of the preset compensation amount based on the compensation current I is: f ( I ) = I × k , Wherein, k is the excitation coefficient of the excitation coil, that is, the magnitude of the magnetic field generated by the coil per unit current, which can be calibrated in advance. In addition, polynomial fitting or machine learning models, etc., can also be used according to needs to establish the mapping relationship between the compensation current I and the compensation amount based on the compensation current I .

[0026] In this embodiment, the zero - point voltage V 0 is the initial output voltage of the superconducting - magnetoresistive composite magnetic sensor and is equal to the output voltage after each working point reset of the superconducting - magnetoresistive composite magnetic sensor.

[0027] In this embodiment, before obtaining the output signal B x of the superconducting - magnetoresistive composite magnetic sensor under the action of the measured magnetic field V , it also includes calibrating the minimum value I min and the maximum value I max of the compensation current I and the saturation magnetic field B r : S201, apply a vertical magnetic field to the superconducting - magnetoresistive composite magnetic sensor, and test the magnetic field - output voltage loop curve of the superconducting - magnetoresistive composite magnetic sensor under different magnitudes of vertical magnetic fields; As Figure 2 shown in the normal saturation output voltage curve of the superconducting - magnetoresistive composite magnetic sensor, the abscissa Bis the magnetic field magnitude, and the vertical coordinate V is the output voltage. The magnetic field range corresponding to the entire linear region is the saturation magnetic field B r , and the maximum value of the vertical coordinate corresponding to the curve is V max , and the minimum value is V min . Figure 2 In, ① is the initial state. The output voltage of the sensor first increases with the increase of the positive external magnetic field. When it reaches the positive saturation, the output voltage remains constant. ② is that if the external magnetic field is decreased at this time, the sensor starts to be sensitive to the external magnetic field again. ③ is that the sensor reaches the negative saturation and the output voltage remains constant. The process of ④ is similar to ②. If the direction of the external magnetic field change is changed at this time, the sensor starts to be sensitive again. ⑤ is that the sensor reaches the positive saturation again, completing a complete saturation loop; S202. Determine the saturation magnetic field according to the saturation region in the magnetic field-output voltage loop curve B r , the maximum output voltage value V max and the minimum output voltage value V min ; Calculate the compensation current according to the following formula I The minimum value of I min and the maximum value I max are: I max =( V max - V 0) / S / k , I min =( V min - V 0) / S / k , where, V 0 is the zero voltage, S is the sensitivity of the superconducting-magnetoresistive composite magnetic sensor. The sensitivity refers to the change value of the output voltage of the superconducting-magnetoresistive composite magnetic sensor under the change of unit external magnetic field, k is the excitation coefficient of the excitation coil.

[0028] In this embodiment, the pulsed reset magnetic field includes magnetic fields in three stages: The magnetic field in the first stage is to apply a reverse magnetic field equal to the saturation magnetic field B r to the superconducting-magnetoresistive composite magnetic sensor - Br , so that the superconducting-magnetoresistive composite magnetic sensor is reversely saturated at this time; the magnetic field in the second stage is to apply a saturation magnetic field equal to the magnitude of the superconducting-magnetoresistive composite magnetic sensor. B r Half of the positive magnetic field B r / 2, so that the superconducting-magnetoresistive composite magnetic sensor reaches positive saturation at this time; the magnetic field in the third stage is to cancel the magnetic field applied by the excitation coil to the superconducting-magnetoresistive composite magnetic sensor, so that the superconducting-magnetoresistive composite magnetic sensor is reset to near the zero working point. Therefore, the magnetic fields in the three stages can be expressed as:- B r → B r / 2→0. Figure 3 This is a schematic diagram of the pulse reset magnetic field in step S103 of this embodiment. Regardless of where the working point of the composite magnetic sensor is located (O1 or O2), first apply a reverse magnetic field -Br equal to the saturation magnetic field, at which time the sensor is reversely saturated and works at point A; then apply a forward magnetic field Br / 2 equal to half of the saturation magnetic field, the sensor reaches forward saturation and works at point B; then cancel the magnetic field, and the sensor working point returns to point C, roughly near the zero point.

[0029] The period of the pulse resetting magnetic field in step S103 should be as short as possible to reduce the loss of magnetic field information and achieve high-speed response of the magnetic field. In this embodiment, the duration of the magnetic field in the three stages is equal, and as an optional implementation, the duration of the magnetic field in the three stages is 10ms, so that the total duration of the pulse resetting magnetic field is 30ms, which can effectively reduce the loss of magnetic field information and achieve high-speed response of the magnetic field.

[0030] The closed-loop controller can adopt the required closed-loop control algorithm as required. As an optional implementation, the closed-loop controller in this embodiment adopts a PID solver as the closed-loop control algorithm. The PID solver should adjust parameters according to the actual situation of the system, and effectively suppress the nonlinearity of the system without affecting the system bandwidth and noise. As an optional implementation, the value of the proportional parameter P used by the PID solver in this embodiment is 0.5, and the value of the integral parameter I is 0.01.

[0031] The closed-loop controller can use the required chip type as required. As an optional implementation, the closed-loop controller in this embodiment is an ARM processor. The ARM processor with small size, low power consumption, low cost and high performance is used. Programming it can realize high-speed data calculation and threshold judgment, and realize fast solution of the measured magnetic field.

[0032] Figure 4 , Figure 5 and Figure 6The compensation magnetic field in this embodiment B c , the reset magnetic field B s and the magnetic field measurement result B are the variation curves with the external magnetic field. When the external magnetic field is less than half of the saturation magnetic field B r / 2, the excitation coil generates a compensation magnetic field in the opposite direction to the external magnetic field ( Figure 4 ), at this time the compensation magnetic field is small and no reset is required ( Figure 5 ), and the system directly obtains the magnetic field measurement result by taking the inverse of the compensation magnetic field ( Figure 6 ); when the external magnetic field increases to half of the saturation magnetic field B r / 2, the compensation magnetic field returns to zero ( Figure 4 ), and the system controls the excitation coil to generate a - B r → B r / 2→0 pulsed magnetic field ( Figure 5 ), performs a reset, and the system determines the new zero magnetic field based on the magnetic field before the reset. At this time, the compensation magnetic field is zero, so the output magnetic field is equal to the magnetic field before the reset B r / 2 ( Figure 6 ); as the external magnetic field further increases, thereafter whenever the compensation magnetic field reaches half of the saturation magnetic field B r / 2, the system will perform a reset and update the zero magnetic field, thereby realizing continuous measurement of the magnetic field.

[0033] Figure 7 and Figure 8 are the comparison of the measurement results before and after adopting the integrated compensation and reset method in this embodiment, where Figure 7 is the external magnetic field-output voltage curve before the integrated compensation and reset, Figure 8 is the external magnetic field-measurement result curve after the integrated compensation and reset. Referring to Figure 7 and Figure 8 it can be seen that before adopting the integrated compensation and reset method, the linear working range of the superconducting-magnetoresistive composite magnetic sensor is about ±5000 nT, and there is a large non-linearity; after adopting the integrated compensation and reset method, each time the external magnetic field exceeds 10000 nT, a pulsed magnetic field is applied to reset the working point. After 20 resets, the measurement range is extended to ±100000 nT, and due to the adoption of the compensation method, the linearity is greatly improved.

[0034] In summary, the integrated measurement method for compensation and reset of the superconducting-magnetoresistive composite magnetic sensor in this embodiment includes obtaining the output voltage of the superconducting-magnetoresistive composite magnetic sensor and performing compensation. Whenever the compensation current exceeds the current corresponding to the saturation magnetic field of the composite magnetic sensor, a reset magnetic field from B r to B r / 2 to 0 is applied to the composite magnetic sensor, so that the composite magnetic sensor enters the negative saturation region at the falling edge of the pulse excitation, enters the positive saturation region at the rising edge of the pulse, and finally enters the middle position of the linear region when the pulse is cancelled. And the zero magnetic field B 0 is updated after each reset. Finally, the measured value of the external magnetic field is calculated according to the zero magnetic field B 0 and the compensation current I B . The method of this embodiment can solve the problems of limited range and non-linearity of the superconducting-magnetoresistive composite magnetic sensor, and can realize the range extension and non-linearity suppression of the superconducting-magnetoresistive composite magnetic sensor on the premise of meeting the requirements of simple structure and small volume, so as to achieve wide-range and high-resolution measurement.

[0035] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.​

Claims

1. A superconducting-magnetoresistive composite magnetic sensor compensation and reset integrated measurement method, characterized in that, including the following steps: obtaining the magnetic field to be measured B x the output signal of the superconducting-magnetoresistive composite magnetic sensor under the action V , calculating the output signal V and the zero-point voltage V the difference of 0 e , calculating the compensation current through the closed-loop controller I ; judging whether the compensation current I meets I min < I < I max , if it meets, controlling the current generator to generate a compensation current I and generating a feedback compensation magnetic field for the superconducting-magnetoresistive composite magnetic sensor through the excitation coil B c to offset the change of the external magnetic field so that the superconducting-magnetoresistive composite magnetic sensor always works near the zero magnetic field B 0, and according to B = B 0+ f ( I ) calculating and obtaining the measured value of the magnetic field to be measured B x ; otherwise, controlling the current generator to generate a pulse reset current and generating a pulse reset magnetic field for the superconducting-magnetoresistive composite magnetic sensor through the excitation coil to reset the superconducting-magnetoresistive composite magnetic sensor to near the zero working point, and after stabilization, according to B 0= B 0= B 0+ f ( I ) updating the zero magnetic field B 0; where I min and I max are respectively the minimum value and the maximum value of the compensation current I , B 0 is the zero magnetic field,[[]] f ( I ) is the preset compensation amount based on the compensation current I , B r is the saturation magnetic field of the superconducting-magnetoresistive composite magnetic sensor.[[]] 2. The integrated measurement method for compensation and reset of a superconducting-magnetoresistive composite magnetic sensor according to claim 1, characterized in that The preset function expression of the compensation amount based on the compensation current I is as follows: f ( I )= I × k ， Among them, k is the excitation coefficient of the exciting coil.

3. The integrated measurement method for compensation and reset of the superconducting-magnetoresistive composite magnetic sensor according to claim 1, wherein The zero voltage V 0 is the initial output voltage of the superconducting-magnetoresistive composite magnetic sensor and is equal to the output voltage of the superconducting-magnetoresistive composite magnetic sensor after each working point reset.

4. The integrated measurement method for compensation and reset of a superconducting-magnetoresistive composite magnetic sensor according to claim 1, wherein The acquisition of the magnetic field to be measured B x the output signal of the superconducting-magnetoresistive composite magnetic sensor under the action V Before that, it also includes calibrating the minimum value I and the maximum value I min of the compensation current I max as well as the saturation magnetic field B r : Apply a vertical magnetic field to the superconducting-magnetoresistive composite magnetic sensor, test the magnetic field-output voltage loop curve of the superconducting-magnetoresistive composite magnetic sensor under vertical magnetic fields of different magnitudes, and determine the saturation magnetic field according to the saturation region in the magnetic field-output voltage loop curve B r the maximum output voltage value V max and the minimum output voltage value V min ; Calculate the minimum value I and the maximum value I min of the compensation current I max : I max =( V max - V 0) / S / k ， I min =( V min - V 0) / S / k ， Among them, V 0 is the zero-point voltage, S is the sensitivity of the superconducting-magnetoresistive composite magnetic sensor, and the sensitivity refers to the change value of the output voltage of the superconducting-magnetoresistive composite magnetic sensor under the change of unit external magnetic field, k is the excitation coefficient of the excitation coil.

5. The integrated measurement method for compensation and reset of the superconducting-magnetoresistive composite magnetic sensor according to claim 1, wherein The pulse reset magnetic field includes three stages of magnetic fields: the first stage of the magnetic field is to apply a saturation magnetic field equal to the magnitude of the superconducting-magnetoresistive composite magnetic sensor. B r The reverse magnetic field - B r , so that the superconducting-magnetoresistive composite magnetic sensor is reversely saturated at this time; the magnetic field in the second stage is to apply a saturation magnetic field equal to the magnitude of the superconducting-magnetoresistive composite magnetic sensor. B r Half of the positive magnetic field B r / 2, so that the superconducting-magnetoresistive composite magnetic sensor reaches positive saturation at this time; the magnetic field in the third stage is to cancel the magnetic field applied by the excitation coil to the superconducting-magnetoresistive composite magnetic sensor, so that the superconducting-magnetoresistive composite magnetic sensor is reset to near the zero operating point.

6. The integrated measurement method for compensation and reset of a superconducting-magnetoresistive composite magnetic sensor according to claim 5, wherein The durations of the magnetic fields in the three stages are equal.

7. The integrated measurement method for compensation and reset of the superconducting-magnetoresistive composite magnetic sensor according to claim 6, wherein The durations of the magnetic fields in the three stages are all 10 ms, so that the total duration of the pulse reset magnetic field is 30 ms.

8. The integrated measurement method for compensation and reset of a superconducting-magnetoresistive composite magnetic sensor according to claim 1, characterized in that The closed-loop controller uses a closed-loop control algorithm as a PID solver.

9. The integrated measurement method for compensation and reset of a superconducting-magnetoresistive composite magnetic sensor according to claim 8, characterized in that The value of the proportional parameter P used by the PID solver is 0.5, and the value of the integral parameter I is 0.

01.

10. The integrated measurement method for compensation and reset of a superconducting-magnetoresistive composite magnetic sensor according to claim 1, wherein The closed-loop controller is an ARM processor.

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