A magnetic shielding cabin residual magnetic field generating device and control method

Abstract

The present invention proposes a device and control method for generating a residual magnetic field in a magnetic shielding cabin, comprising a host computer, a DSP module, a power amplifier, a fluxgate sensor, a programmable gain amplifier, a demagnetization coil, and a magnetic shielding cabin. The host computer outputs analog quantities through programming to control the demagnetization current parameters and DC bias; the analog quantities are converted into voltage signals and output by the DSP module; the voltage signals are amplified and output after passing through the power amplifier; the voltage signals act on a load resistor to form a demagnetization current with specific parameters; the fluxgate sensor obtains the magnitude of the residual magnetic field at the center of the magnetic shielding cabin and converts it into a voltage signal and outputs it; the programmable gain amplifier reads the voltage signal and amplifies the signal through program control to obtain the magnitude of the magnetic field. The present invention achieves control of the residual magnetic field in the magnetic shielding cabin by adding a DC bias to the demagnetization current, ensuring low cost while generating a stable and controllable residual magnetic field.

Description

Technical Field

[0001] The invention belongs to the technical field of demagnetization, and in particular relates to a residual magnetic field generating device for a magnetic shielding cabin and a control method thereof. Background Art

[0002] At present, fields such as national defense science and technology, aerospace, biological detection and cutting-edge physics research all have strict requirements for extremely weak magnetic environments. In order to achieve a near-zero magnetic environment, it is necessary to build a magnetic shielding device, demagnetize the device, and use a magnetic compensation coil to control the residual magnetic field at the center.

[0003] The aforementioned biological detection field also raises the issue of generating a submagnetic magnetic field (residual magnetic field less than 5μT). Some biological experiments do not pursue near-zero background magnetic conditions, but instead require cultivating and observing the physiological behavior of plants and animals under a residual magnetic field of a specific magnitude. These experiments do not require high-precision control of the background magnetic field, but rather require that the background field be maintained stable over a long period of time.

[0004] The existing magnetic field generation solution is to add an active magnetic compensation system to the magnetic shielding cabin. First, the magnetic shielding cabin is used to isolate the influence of the ambient magnetic field, and then the arrangement of the magnetic compensation coils and the current size are controlled to change the magnetic field at the center. This magnetic field generation solution requires a complex control system. In order to maintain the stability of the magnetic field, current needs to be passed through the magnetic compensation coils for a long time. After power failure, the residual magnetic field will change rapidly. Therefore, the overall cost of the solution is high and it is not suitable for providing a magnetic field environment for a long time. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a magnetic shielding cabin residual magnetic field generating device and control method, which realizes the control of the magnetic shielding cabin residual magnetic field based on the demagnetization method.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A residual magnetic field generating device for a magnetic shielding cabin, comprising:

[0008] Host computer, DSP module, power amplifier, load resistor and magnetic shielding cabin; the magnetic shielding cabin includes a degaussing coil and a fluxgate sensor;

[0009] The host computer is used to write programs to control demagnetization current parameters and DC bias;

[0010] The DSP module is used to output an analog voltage signal;

[0011] The power amplifier is used to amplify the voltage signal;

[0012] The load resistor is used to convert the voltage signal into current;

[0013] The degaussing coil is used to generate an alternating magnetic field to demagnetize the magnetic shielding cabin;

[0014] The magnetic shielding cabin is used to shield the influence of the environmental magnetic field and generate a specific residual magnetic field at the center;

[0015] The fluxgate sensor obtains the magnitude of the residual magnetic field.

[0016] Furthermore, the DSP module includes a DA conversion unit and a signal amplification unit; the DA conversion unit is used to convert the host computer digital signal into an analog voltage signal; the signal amplification unit is used to amplify the analog voltage to a specific multiple according to application requirements and output it.

[0017] Furthermore, the power amplifier uses a voltage control mode.

[0018] Furthermore, the rated power of the load resistor is greater than 500W.

[0019] The present invention also provides a method for controlling a residual magnetic field generating device of a magnetic shielding cabin, comprising:

[0020] The demagnetization current DC bias is changed multiple times using a specific gradient, and a relationship curve between the demagnetization current DC bias and the residual magnetic field is drawn. Based on the relationship curve, the DC bias of the demagnetization current is changed to control the residual magnetic field.

[0021] Furthermore, the host computer controls the demagnetization current DC bias through programming.

[0022] Furthermore, the specific gradient is first large and then small, wherein the large gradient changes the demagnetization current DC bias to quickly determine the curve saturation point and the curve slope change interval, and the small gradient changes the demagnetization current DC bias to determine the end point of the linear area in the curve.

[0023] Furthermore, the demagnetization current DC bias is changed multiple times using a specific gradient, and a curve of the relationship between the demagnetization current DC bias and the residual magnetic field is drawn, which specifically includes the following steps:

[0024] Step S11: Place the fluxgate sensor in the same position of the magnetic shielding cabin, and read the initial residual magnetic field in the X, Y, and Z directions. Calculate the fluxgate sensor bias B in each direction x' ,B y' ,B z' , the calculation formula is as follows:

[0025]

[0026]

[0027]

[0028] The magnetic field magnitude measured by the fluxgate sensor minus the bias in each direction is the true value of the magnetic field magnitude at that point;

[0029] Step S12, controlling the demagnetization current amplitude A=0 and the DC bias ΔI=0 through the host computer programming, measuring the DA conversion unit output voltage U0, and if U0≠0, changing the bias variable in the host computer program until the DA conversion unit output voltage is 0;

[0030] Step S13, adding a demagnetization current to the demagnetization coil through the magnetic shielding cabin residual magnetic field generating device to demagnetize the magnetic shielding cabin;

[0031] Step S14: adding a degaussing current containing a DC bias to the degaussing coil to generate a residual magnetic field of a specific magnitude at the center of the magnetic shielding cabin;

[0032] Step S15, reading the magnetic field magnitude at the center of the magnetic shielding cabin through a fluxgate sensor and a programmable gain amplifier, recording the DC bias magnitude and the residual magnetic field magnitude at this time, and plotting a relationship graph between the two;

[0033] If the image at this time meets the actual application requirements, then the control method ends; if not, then the process proceeds to step S16;

[0034] Step S16, changing the DC bias value and entering step S13.

[0035] Furthermore, in step S15, a relationship curve between the demagnetization current DC bias and the residual magnetic field is drawn, in which the independent variable is the DC bias ΔI and the dependent variable is the residual magnetic field B, specifically including the following steps:

[0036] Step S21: Demagnetize the magnetic shielding cabin without applying a DC bias. Record the bias current and residual magnetic field at this point, and mark this point as a. Point a is the starting point of the curve. Increase the demagnetization current DC bias with a large gradient and record the corresponding change in the residual magnetic field. When the residual magnetic field reaches saturation, record the bias current and residual magnetic field at this point, and mark this point as c. Point c is the end point of the curve.

[0037] Step S22: Based on the data recorded in step S21, find the interval where the slope of the curve begins to change. Within this interval, change the demagnetization current DC bias with a small gradient and record the corresponding change in the residual magnetic field. When the slope of the curve begins to change, the turning point of the slope is recorded as b. Point b is the end point of the linear change region.

[0038] Step S23, connecting point a and point b, the linear change area ab is the main control area in this control method;

[0039] If the linear region meets the actual application requirements, the process ends; if not, the process proceeds to step S24;

[0040] Step S24 , starting from point b, increasing the demagnetization current DC bias with a small gradient, and recording the corresponding residual magnetic field change until reaching the end point c.

[0041] The beneficial effects of the present invention are:

[0042] The present invention replaces the magnetic compensation scheme with a demagnetization scheme, simplifies the structure of the magnetic field generating device, avoids the use of a complex control system, and the generated residual magnetic field can remain stable for a long time after power failure, greatly reducing costs while achieving nT-level control of the residual magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a control block diagram of a magnetic field generating device in an embodiment of the present invention;

[0044] Figure 2 This is a flow chart of measuring the residual magnetic field after different DC bias demagnetization treatments in an embodiment of the present invention;

[0045] Figure 3 This is a flow chart for drawing a curve showing the relationship between the demagnetization current DC bias and the residual magnetic field in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0047] like Figure 1 As shown, this embodiment provides a magnetic shield cabin residual magnetic field generating device, including:

[0048] A host computer, a DSP module, a power amplifier, a load resistor and a magnetic shielding cabin; the magnetic shielding cabin includes a degaussing coil, a fluxgate sensor and a programmable gain amplifier.

[0049] The host computer is used to write programs to control demagnetization current parameters and DC bias;

[0050] The DSP module is used to output analog voltage signals;

[0051] The power amplifier is used to amplify the voltage signal;

[0052] The load resistor is used to convert the voltage signal into current;

[0053] The degaussing coil is used to generate an alternating magnetic field to degauss the magnetic shielding cabin;

[0054] The magnetic shielding cabin is used to shield the influence of the environmental magnetic field and generate a specific residual magnetic field at the center;

[0055] The fluxgate sensor obtains the magnitude of the residual magnetic field;

[0056] The programmable gain amplifier is used to amplify the voltage signal output by the fluxgate sensor to facilitate data reading.

[0057] In some embodiments, the DSP module includes a DA conversion unit and a signal amplification unit; the DA conversion unit is used to convert the host computer digital signal into an analog voltage signal; the signal amplification unit is used to amplify the analog voltage by a specific multiple according to application requirements and output it.

[0058] In some embodiments, the power amplifier uses a voltage control mode.

[0059] In some embodiments, the load resistor has a power rating greater than 500W.

[0060] like Figure 1 As shown in the figure, the waveform of the demagnetization current and the size of the DC bias are controlled by the host computer programming. After passing through the DA conversion unit of the DSP module, the analog voltage signal is output to the power amplifier. The amplified voltage signal acts on the load resistor connected in series with the demagnetization coil to form a demagnetization current. After the demagnetization current with DC bias acts on the magnetic shielding cabin, a specific size of residual magnetic field will be generated in it.

[0061] This embodiment further provides a method for controlling a residual magnetic field generating device of a magnetic shielding cabin, which is characterized by comprising:

[0062] The demagnetization current DC bias is changed multiple times using a specific gradient, and a curve showing the relationship between the demagnetization current DC bias and the residual magnetic field is drawn. Based on this curve, the residual magnetic field can be controlled by changing the demagnetization current DC bias.

[0063] In some embodiments, the host computer controls the DC bias through programming.

[0064] In some embodiments, a fluxgate sensor obtains the magnitude of the residual magnetic field.

[0065] In some embodiments, the specific gradient should be large at first and then small, wherein the large gradient changes the demagnetization current DC bias to quickly determine the curve saturation point and the curve slope change interval, and the small gradient changes the demagnetization current DC bias to determine the end point of the linear region in the curve.

[0066] Next, the process of measuring the magnitude of the residual magnetic field after demagnetization treatments with different DC biases in the control method according to the embodiment of the present invention to draw a curve showing the relationship between the demagnetization current DC bias and the residual magnetic field will be described.

[0067] like Figure 2As shown, in the embodiment of the present invention, measuring the residual magnetic field after different DC bias demagnetization processes specifically includes the following steps:

[0068] Step S11: Place the fluxgate sensor in the same position of the magnetic shielding cabin, and read the initial residual magnetic field in the X, Y, and Z directions. Calculate the fluxgate sensor bias B in each direction x' ,B y' ,B z' , the calculation formula is as follows:

[0069]

[0070]

[0071]

[0072] In the subsequent steps, the magnetic field magnitude measured by the fluxgate sensor minus the bias in each direction is the true value of the magnetic field magnitude at that point;

[0073] Step S12, controlling the demagnetization current amplitude A=0 and the DC bias ΔI=0 through the host computer programming, measuring the DA conversion unit output voltage U0, and if U0≠0, changing the bias variable in the host computer program until the DA conversion unit output voltage is 0;

[0074] Step S13, by Figure 1 The generator shown adds a demagnetizing current to the demagnetizing coil to demagnetize the magnetic shielding cabin. The purpose of this step is to provide a constant initial condition to eliminate the influence of the residual magnetic field in the cabin on subsequent steps.

[0075] Step S14: adding a degaussing current containing a DC bias to the degaussing coil to generate a residual magnetic field of a specific magnitude at the center of the magnetic shielding cabin;

[0076] Step S15, reading the magnetic field magnitude at the center of the magnetic shielding cabin through a fluxgate sensor and a programmable gain amplifier, recording the DC bias magnitude and the residual magnetic field magnitude at this time, and plotting a relationship graph between the two;

[0077] If the image at this time meets the actual application requirements, the process ends; if not, the process proceeds to step S16;

[0078] Step S16, changing the DC bias value and entering step S13.

[0079] The method is used to accurately obtain the residual magnetic field size at the center of the magnetic shielding cabin under a specific DC bias. The specific steps of changing the DC bias in step S16 and drawing the residual magnetic field size image after demagnetization with different DC biases in step S15 will be combined with Figure 3 To elaborate.

[0080] Experiments have shown that as the DC bias of the demagnetization current gradually increases, the change in the residual magnetic field will show a trend of first increasing linearly and then gradually approaching saturation. Based on this property, an embodiment of the present invention proposes a method for plotting a curve showing the relationship between the DC bias of the demagnetization current and the residual magnetic field, in which the independent variable is the DC bias ΔI and the dependent variable is the residual magnetic field B.

[0081] like Figure 3 As shown, in the embodiment of the present invention, drawing a curve of the relationship between the demagnetization current DC bias and the residual magnetic field specifically includes the following steps:

[0082] Step S21: Demagnetize the magnetic shielding cabin without applying a DC bias. Record the bias current and residual magnetic field at this point, and mark this point as a. Point a is the starting point of the curve. Increase the demagnetization current DC bias with a large gradient and record the corresponding change in the residual magnetic field. When the residual magnetic field reaches saturation, record the bias current and residual magnetic field at this point, and mark this point as c. Point c is the end point of the curve.

[0083] Step S22: Based on the data recorded in step S21, find the interval where the slope of the curve begins to change. Within this interval, change the demagnetization current DC bias with a small gradient and record the corresponding change in the residual magnetic field. When the slope of the curve begins to change, the turning point of the slope is recorded as b. Point b is the end point of the linear change region.

[0084] Step S23, connecting point a and point b, the linear change area ab is the main control area in this control method;

[0085] If the linear region meets the actual application requirements, the process ends; if not, the process proceeds to step S24;

[0086] Step S24 , starting from point b, increasing the demagnetization current DC bias with a small gradient, and recording the corresponding residual magnetic field change until reaching the end point c.

[0087] Parts of the present invention that are not disclosed in detail belong to the common knowledge in the art.

[0088] Although the specific implementation details of the present invention have been described above to facilitate technical personnel in the relevant fields to understand the present invention, it is worth noting that the present invention is not limited to the scope of specific applications. For ordinary technical personnel in the relevant fields, as long as various changes are within the scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations obtained by using the concept of the present invention are within the scope of protection.

Claims

1. A control method for a residual magnetic field generating device of a magnetic shielding cabin, characterized in that: The residual magnetic field generating device of the magnetic shielding cabin includes: a host computer, a DSP module, a power amplifier, a load resistor and a magnetic shielding cabin; the magnetic shielding cabin includes a degaussing coil, a fluxgate sensor and a programmable gain amplifier; The host computer is used to write programs to control demagnetization current parameters and DC bias; The DSP module is used to output an analog voltage signal; The power amplifier is used to amplify the voltage signal; The load resistor is used to convert the voltage signal into current; The degaussing coil is used to generate an alternating magnetic field to demagnetize the magnetic shielding cabin; The magnetic shielding cabin is used to shield the influence of the environmental magnetic field and generate a specific residual magnetic field at the center; The fluxgate sensor obtains the magnitude of the residual magnetic field; The programmable gain amplifier is used to amplify the voltage signal output by the fluxgate sensor to facilitate data reading; the control method includes: The method comprises the following steps: using a specific gradient to change the demagnetization current DC bias multiple times, drawing a relationship curve between the demagnetization current DC bias and the residual magnetic field, and changing the demagnetization current DC bias according to the relationship curve to control the residual magnetic field. Step S11: Place the fluxgate sensor in the same position of the magnetic shielding cabin, and read the , , The initial residual magnetic field magnitude in three directions , calculate the fluxgate sensor bias in each direction , the calculation formula is as follows: (1) (2) (3) The magnetic field magnitude measured by the fluxgate sensor minus the bias in each direction is the true value of the magnetic field magnitude at that point; Step S12: Control the demagnetization current amplitude through host computer programming , DC bias , measure the output voltage of the DA conversion unit ,like , then change the bias variable in the host computer program until the output voltage of the DA conversion unit is ; Step S13, adding a demagnetization current to the demagnetization coil through the magnetic shielding cabin residual magnetic field generating device to demagnetize the magnetic shielding cabin; Step S14: adding a degaussing current containing a DC bias to the degaussing coil to generate a residual magnetic field of a specific magnitude at the center of the magnetic shielding cabin; Step S15, reading the magnetic field magnitude at the center of the magnetic shielding cabin through a fluxgate sensor and a programmable gain amplifier, recording the DC bias magnitude and the residual magnetic field magnitude at this time, and plotting a relationship graph between the two; If the image at this time meets the actual application requirements, then the control method ends; if not, then the process proceeds to step S16; Step S16, changing the DC bias value and entering step S13.

2. The control method according to claim 1, characterized in that: The DSP module includes a DA conversion unit and a signal amplification unit; the DA conversion unit is used to convert the host computer digital signal into an analog voltage signal; the signal amplification unit is used to amplify the analog voltage to a specific multiple according to application needs and output it.

3. The control method according to claim 1, wherein: The power amplifier uses a voltage control mode.

4. The control method according to claim 1, wherein: The rated power of the load resistor is greater than 500 .

5. The control method according to claim 1, characterized in that: The host computer controls the demagnetization current DC bias through programming.

6. The control method according to claim 1, characterized in that: The specific gradient is first large and then small, wherein the large gradient changes the demagnetization current DC bias to quickly determine the curve saturation point and the curve slope change interval, and the small gradient changes the demagnetization current DC bias to determine the end point of the linear area in the curve.

7. The control method according to claim 1, characterized in that: In step S15, a relationship curve between the demagnetization current DC bias and the residual magnetic field is drawn. In the relationship curve, the independent variable is the DC bias. , the dependent variable is the residual magnetic field , specifically including the following steps: Step S21: demagnetize the magnetic shielding cabin without adding DC bias, record the bias current and residual magnetic field at this time, and record this point as ,point This is the starting point of the curve; use a large gradient to increase the demagnetization current DC bias and record the corresponding residual magnetic field changes. When the residual magnetic field is saturated, record the bias current and residual magnetic field at this time and record this point as ,point This is the end point of the curve; Step S22: Based on the data recorded in step S21, find the interval where the slope of the curve begins to change. In this interval, use a small gradient to change the DC bias of the demagnetization current and record the corresponding residual magnetic field change. When the slope of the curve begins to change, record the slope turning point as ,point This is the end point of the linear change area; Step S23, connection Point and Point, linear change area This is the main control area in this control method; If the linear region meets the actual application requirements, the process ends; if not, the process proceeds to step S24; Step S24, from Starting from point 1, increase the demagnetization current DC bias with a small gradient and record the corresponding residual magnetic field change until reaching the end point. .

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