A multi-modal array magnetic field generation system and method

Abstract

The present invention relates to the field of magnetic field generation, and discloses a multi-modal array magnetic field generation system and method, including single-excitation source matrix excitation; the single-excitation source matrix excitation includes an FPGA main control chip and a DDS signal generation module. The DDS chip reads the signal waveform stored in the ROM, and the keying module combines the PLL clock signal module and the amplification circuit to realize a signal with adjustable amplitude, frequency, phase and duty cycle. The bipolar D / A conversion is used to apply excitation to the array coil to generate magnetic fields of different modes, and the Hall magnetosensitive sensor is combined to adjust the angle and direction of the generated magnetic field in real time, dynamically changing the angle of magnetic field focusing. The present invention excites the array coil by generating current signals with various different amplitudes, frequencies, phases, duty cycles and directions, and combines the Hall magnetosensitive sensor above the coil to realize the controllability of the energy and direction of the array magnetic field, improve the magnetic field generation efficiency, and enhance the detectability.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field generation, and particularly to a multi-modal array magnetic field generation system and method. Background Art

[0002] In recent years, with the continuous development of communication technology and its increasingly widespread application, the demand for signal sources has become more diverse and complex. A signal source, also known as a signal generator, can generate different waveform signals with adjustable frequency, duty cycle, and amplitude, and can be used in a large number of test scenarios that require electromagnetic waves as excitation. It has a wide range of applications in fields such as electronic circuits, scientific experiments, communications, scientific instruments, and automatic control, and is one of the most commonly used and basic electronic instruments. With the improvement of digital integrated circuit and microelectronic manufacturing process levels, DDS technology has the characteristics of high integration, wide frequency synthesis range, high frequency synthesis accuracy, continuous phase during frequency tuning, high spurious suppression ratio, and low phase noise. The generated signal has good stability and high quality. However, most common signal generators are direct current outputs, capable of simple frequency, phase, and amplitude adjustments and having fewer output channels. Since underground target detection includes mineral resource exploration, goaf search, archaeological relic detection, and unexploded ordnance investigation, ordinary signal generators cannot meet the high-precision detection of underground targets and are prone to safety hazards. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a multi-modal array magnetic field generation system to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the following technical solutions are further adopted:

[0005] A multi-modal array magnetic field generation system includes a single excitation source matrix excitation and a multi-mode magnetic field adaptive direction adjustment mechanism;

[0006] The single excitation source matrix excitation includes an FPGA master control chip, a DDS signal generation module, a PLL clock signal module, and a D / A conversion module. The FPGA master control chip provides signals to the DDS signal generation module and the PLL clock signal module through an external crystal oscillator source. The DDS signal generation module places data of a complete cycle of square wave signals in the ROM memory. The ROM memory uses the phase code input by the phase modulator as the read address, outputs in multiple channels, and reads the data at the corresponding address in a parallel manner for voltage output. The frequency word input and phase word input of the DDS signal generation module are controlled to adjust the frequency and phase of the generated signal. The duty cycle of the signals generated in each path is adjusted by the PLL clock signal module for each signal output channel;

[0007] It is converted into an analog signal through a bipolar high-speed D / A conversion module, and the signal is output in the form of current through a voltage-current conversion circuit, completing a current signal with adjustable frequency, phase, and duty cycle;

[0008] The output analog signal is filtered through a filter circuit. After removing stray noise, it passes through a current amplification circuit, and the amplitude of the output current is adjusted by changing the amplification factor of the circuit. A single-pole double-throw switch is used to change the direction of the current flowing into the coil, completing the output of multi-modal matrix current;

[0009] The multi-mode magnetic field adaptive direction adjustment mechanism includes an array excitation coil on the lower layer and an array Hall magnetosensor on the upper layer. A magnetic field is generated by a single excitation source multi-mode array excitation coil, and the generated magnetic field intensity is detected by the upper-layer array Hall magnetosensor. The data of the array Hall magnetosensor is used to measure the distribution of the regional magnetic field through a filter circuit, and the output current is fed back through a data conditioning circuit. By changing the mode of the output current, the expected generated magnetic field direction is gradually approximated.

[0010] Preferably, the signal output of each path of the DDS signal generation module adopts a serial structure of two PLL chips. One chip generates a clock signal with a specific frequency corresponding to the output of the channel as the reference signal input of the second PLL chip. Four clock signals with different duty cycles are preset inside the second PLL chip, which are 10%, 20%, 30%, and 40% respectively. The adjustment of the clock signal with any duty cycle is realized through the combination of clock signals. The PWM modulation signals corresponding to each channel are generated by two PLL chips to adjust the duty cycle of the signals generated by each path of the DDS signal generation module.

[0011] A multi-modal array magnetic field generation method includes the following steps:

[0012] S1: Select the amplitude, phase, frequency, duty cycle, and direction of the output of each channel of the single excitation source matrix current of the array;

[0013] S2: According to the output waveform, the currents I1, I2, I3... of the required waveform are output through a bipolar D / A conversion circuit, and then the current amplitude is adjusted by turning the knob of the amplification circuit. Finally, the output current is used to excite the coil; the output current of each channel can be expressed as:

[0014]

[0015] A represents the amplitude of the excitation current, and f represents the excitation frequency. represents the initial phase of the excitation current, the current period is R, and the duty cycle of the current can be expressed as:

[0016]

[0017] S3: When a bipolar pulse excitation I1 with a period of T is applied to the transmitting coil, a changing primary magnetic field H1 will be generated around the coil. At this time, under the excitation of the alternating current, the magnetic field generated by a certain coil in one cycle is expressed as:

[0018]

[0019] Thus, the magnetic field generated by the matrix coil can be obtained as:

[0020]

[0021] According to the principle of magnetic field vector superposition, the total magnetic field generated by the array coil is:

[0022]

[0023] S4: Make a judgment based on the magnetic field magnitude value detected by the Hall magnetic sensor, and perform feedback adjustment on the current amplitude, frequency, phase, and duty cycle applied to the coil, so that the generated magnetic field gradually approaches the target angle magnetic field.

[0024] The beneficial effects of the present invention are:

[0025] The present invention is based on an FPGA master control chip combined with a DDS signal generation module and a PLL clock signal module to implement a signal source with multi-channel and multi-mode matrix output, adjust the frequency and phase of the output signal, independently control the duty cycle of each output by controlling two PLL chips to generate PWM waves, design a bipolar high-speed D / A conversion module, and combine a current amplification circuit to achieve amplitude adjustment of the current; design an array coil combined with a Hall magnetic sensor, generate a magnetic field by applying different modes of excitation to the array coil, according to the principle of magnetic field vector superposition, the magnetic field generated by the array coil can be fitted into a complete magnetic field, adjust the mode of a certain coil to change the superposition state of the magnetic field, realize the adjustment of the magnetic field focusing direction, and according to the value of the Hall magnetic sensor at the upper end of the coil, detect the magnetic field direction in real time and compare it with the theoretical value of the target angle according to the sensor data, and dynamically adjust the excitation mode in real time to complete the generation of a multi-mode array magnetic field. Description of the Drawings

[0026] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0027] Figure 1 is a schematic structural diagram of a multi-mode array magnetic field generation system of the present invention;

[0028] Figure 2 is a structural diagram for adjusting the frequency, phase, duty cycle, and amplitude of a certain channel of the present invention;

[0029] Figure 3 is a schematic structural diagram of the array coil and Hall magnetosensitive sensor of the present invention;

[0030] Figure 4 is a schematic working principle diagram of the Hall magnetosensitive sensor in theory of the present invention;

[0031] Figure 5 is a schematic diagram of multimodal magnetic field superposition in theory of the present invention. Specific Embodiments

[0032] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0033] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0034] A multimodal array magnetic field generating system includes a single excitation source matrix excitation and a multimode magnetic field adaptive direction adjusting mechanism;

[0035] The single excitation source matrix excitation includes an FPGA main control chip, a DDS signal generating module, a PLL clock signal module, and a D / A conversion module. The FPGA main control chip provides signals to the DDS signal generating module and the PLL clock signal module through an external crystal oscillator source. The DDS signal generating module places the data of a complete cycle of square wave signals in the ROM memory. The ROM memory uses the phase code input by the phase modulator as the read address, outputs in multiple channels, and reads the data at the corresponding address in a parallel manner to output voltage, controls the frequency word input and phase word input of the DDS signal generating module, adjusts the frequency and phase of the generated signal. Each signal output channel adopts a serial structure of two PLL chips. One of the chips generates a clock signal with a specific frequency corresponding to the channel output as the reference signal input of the second PLL chip. Four clock signals with different duty cycles are preset inside the second PLL chip, which are: 10%, 20%, 30%, and 40% respectively. The adjustment of the clock signal with any duty cycle is achieved through the combination of clock signals. The PWM modulation signals corresponding to each channel are generated by two PLL chips to adjust the duty cycle of the signals generated by each path of the DDS signal generating module;

[0036] It is converted into an analog signal through a bipolar high-speed D / A conversion module, and the signal is output in the form of current through a voltage-current conversion circuit, completing a current signal with adjustable frequency, phase, and duty cycle;

[0037] The output analog signal is filtered through a filter circuit, and after removing the stray noise, it passes through a current amplification circuit. The amplitude of the output current is adjusted by changing the amplification factor of the circuit, and a single-pole double-throw switch is used to change the direction of the current flowing into the coil, completing the multi-modal matrix current output;

[0038] The multi-mode magnetic field adaptive direction adjustment mechanism includes an array excitation coil 1 on the lower layer and an array Hall magnetosensor 2 on the upper layer. A magnetic field is generated by a single excitation source multi-mode array excitation coil, and the magnetic field intensity generated is detected by the upper-layer array Hall magnetosensor 2. The data of the array Hall magnetosensor 2 is used to measure the distribution of the regional magnetic field through a filter circuit, and the output current is fed back through a data conditioning circuit. By changing the mode of the output current, the expected magnetic field direction is gradually approximated.

[0039] Frequency and phase adjustment are quantified according to the rotation angle of the knob, and the frequency word input and phase sub-input of the DDS chip are adjusted; Duty cycle adjustment is mainly achieved by adding two PLL chips in each signal output path. By recording the frequency corresponding to the current output signal and setting the target duty cycle, a PWM modulation waveform corresponding to the channel is generated to adjust the duty cycle of each signal; Current amplitude and direction adjustment include bipolar D / A conversion, a signal filter circuit, a current amplification circuit, and a single-pole double-throw switch. It is consistent with the frequency and phase adjustment method. The amplitude of the excitation current is adjusted by changing the amplification factor of the circuit through the knob, and the direction of the coil excitation current is adjusted by changing the position of the switch paddle.

[0040] A multi-modal array magnetic field generation method includes the following steps:

[0041] S1: Select the amplitude, phase, frequency, duty cycle, and direction of the output of each channel of the single excitation source matrix current of the array;

[0042] S2: According to the output waveform, the currents I1, I2, I3... of the required waveform are output through a bipolar D / A conversion circuit, and then the amplitude of the current is adjusted by the amplification circuit knob. Finally, the current output is used to excite the coil; The output current of each channel can be expressed as:

[0043]

[0044] A represents the amplitude of the excitation current, f represents the excitation frequency, represents the initial phase of the excitation current, the current period is T, and the duty cycle of the current can be expressed as:

[0045]

[0046] S3: When a bipolar pulse excitation I1 with a period of T is applied to the transmitting coil, a changing primary magnetic field H1 will be generated around the coil; at this time, under the excitation of the alternating current, the magnetic field generated by a certain coil in one cycle is expressed as:

[0047]

[0048] Thus, the magnetic field generated by the matrix coil can be obtained as:

[0049]

[0050] According to the principle of magnetic field vector superposition, the total magnetic field generated by the array coil is:

[0051]

[0052] S4: Make a judgment based on the magnetic field magnitude value detected by the Hall magnetosensitive sensor, and perform feedback adjustment on the current amplitude, frequency, phase, and duty cycle of the coil, so that the generated magnetic field gradually approaches the target angle magnetic field.

[0053] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-modal array magnetic field generating system, characterized in that: It includes a single excitation source matrix excitation and a multi-mode magnetic field adaptive direction adjustment mechanism; The single excitation source matrix excitation includes an FPGA main control chip, a DDS signal generation module, a PLL clock signal module, and a D / A conversion module. The FPGA main control chip provides signals to the DDS signal generation module and the PLL clock signal module through an external crystal oscillator source. The DDS signal generation module places data of a square wave signal with a complete cycle in the ROM memory. The ROM memory uses the phase code input by the phase modulator as the read address, outputs in multiple channels, and reads the data at the corresponding address in a parallel manner to output voltage, controls the frequency word input and phase word input of the DDS signal generation module, and adjusts the frequency and phase of the generated signal. Each signal output channel of the DDS signal generation module adjusts the duty cycle of the signals generated by each path through the PLL clock signal module; It is converted into an analog signal through a bipolar high-speed D / A conversion module, and the signal is output in the form of current through a voltage-current conversion circuit, completing a current signal with adjustable frequency, phase, and duty cycle; The output analog signal is filtered through a filter circuit, and after removing stray noise, it passes through a current amplification circuit. The amplitude of the output current is adjusted by changing the amplification factor of the circuit. A single-pole double-throw switch is used to change the direction of the current flowing into the coil, completing the multi-modal matrix current output; The multi-mode magnetic field adaptive direction adjustment mechanism includes an array excitation coil in the lower layer and an array Hall magnetosensitive sensor in the upper layer. A magnetic field is generated by the single excitation source multi-mode array excitation coil, and the generated magnetic field intensity is detected by the upper-layer array Hall magnetosensitive sensor. The data of the array Hall magnetosensitive sensor measures the distribution of the regional magnetic field through a filter circuit, feeds back the output current through a data conditioning circuit, and gradually approaches the expected magnetic field direction by changing the mode of the output current.

2. The multimodal array magnetic field generation system according to claim 1, wherein: Each signal output path of the DDS signal generation module adopts a serial structure of two PLL chips. One chip generates a clock signal with a specific frequency corresponding to the channel output as the reference signal input of the second PLL chip. Four clock signals with different duty cycles are preset inside the second PLL chip, which are 10%, 20%, 30%, and 40% respectively. The adjustment of the clock signal with any duty cycle is achieved through the combination of clock signals. The PWM modulation signals corresponding to each channel are generated by the two PLL chips to adjust the duty cycle of the signals generated by each path of the DDS signal generation module.

3. A multi-modal array magnetic field generation method, characterized in that, It includes the following steps: S1: Select the amplitude, phase, frequency, duty cycle, and direction of the single excitation source array channel output; S2: According to the output waveform, output the current of the required waveform through the bipolar D / A conversion circuit I 1 、I 2 、I 3 ..., then adjust the current amplitude through the amplifier circuit knob, and finally output the current to excite the coil; the output current of each channel can be expressed as: ； represents the amplitude of the excitation current, represents the excitation frequency, represents the initial phase of the excitation current, represents the duration of the output, and the duty cycle of the current can be expressed as: ； Among them, T high represents the time of the positive output, and the current period is T ; S3: Apply a bipolar pulse excitation with a period of T to the transmitting coil I 1 When this is done, a changing primary magnetic field will be generated around the coil H 1; At this time, under the excitation of an alternating current, the magnetic field generated by a certain coil in one cycle is expressed as: ； Among them, N represents the number of turns of the coil, represents the magnetic permeability of the coil, R represents the radius of the coil, A ｉ represents the output amplitude of the channel with serial number i ; f ｉ represents i the frequency of the output signal of the channel, represents the phase of the excitation signal of the i th channel, T high represents the time of the forward output; thus, the magnetic field generated by the matrix coil can be obtained as follows: ； According to the magnetic field vector superposition principle, the total magnetic field generated by the array coil is: ； Among them, n = 9, and represent the phase and duty cycle of the channels. If the magnetic field direction generated by each channel is downward, it is a + sign; if the magnetic field direction is upward, it is a - sign. H i represents i the magnitude of the magnetic field generated by the S4: Judge according to the magnetic field magnitude value detected by the Hall magnetosensitive sensor, and perform feedback adjustment on the current amplitude, frequency, phase, and duty cycle applied to the coil, so that the generated magnetic field gradually approaches the target angle magnetic field.

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