Multi-mode array magnetic field generation system and method

Abstract

The invention relates to the field of magnetic field generation, and discloses a multi-mode array magnetic field generation system and method. The single excitation source matrix excitation comprises an FPGA main control chip and a DDS signal generation module, a DDS chip reads a signal waveform stored in an ROM, a keying module is combined with a PLL clock signal module and an amplification circuit, signals with adjustable amplitude, frequency, phase and duty ratio are achieved, excitation is applied to an array coil through bipolar D / A conversion to generate magnetic fields of different modes, and the magnetic fields of different modes are generated. The Hall magneto-dependent sensor is combined to adjust the angle and direction of the generated magnetic field in real time, and the focusing angle of the magnetic field is dynamically changed. The array coil is excited by generating a plurality of current signals with different amplitudes, frequencies, phases, duty ratios and directions, and the Hall magneto-dependent sensor above the coil is combined, so that the energy and direction of an array magnetic field are controllable, the magnetic field generation efficiency is improved, and the detection target is enhanced.

Description

Technical Field

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

[0002] In recent years, with the continuous development and increasing application of communication technology, the demand for signal sources has become increasingly diverse and complex. Signal sources, also known as signal generators, can generate various waveform signals with adjustable frequency, duty cycle, and amplitude. They can be used in a wide range of test scenarios requiring electromagnetic waves as excitation. They are widely used in electronic circuits, scientific experiments, communications, scientific instrumentation, and automatic control, making them one of the most commonly used and fundamental electronic instruments. With the advancement of digital integrated circuit and microelectronic manufacturing processes, DDS technology has achieved high integration, a wide frequency synthesis range, high frequency synthesis accuracy, phase continuity during frequency tuning, high spurious suppression, and low phase noise, resulting in high-quality and stable signals. However, most common signal generators have a DC output, provide simple frequency, phase, and amplitude adjustments, and have limited output channels. Since underground target detection includes mineral resource exploration, goaf locating, archaeological artifact detection, and unexploded ordnance detection, ordinary signal generators cannot meet the high-precision requirements for underground target detection, posing a potential safety hazard. Summary of the Invention

[0003] In view of this, an object of the present invention is to provide a multi-mode array magnetic field generating system to solve the problems raised in the above background technology.

[0004] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0005] A multi-mode array magnetic field generating system, comprising a single excitation source matrix excitation and a multi-mode magnetic field adaptive direction adjustment mechanism;

[0006] Single excitation source matrix excitation, including FPGA main control chip, DDS signal generation module, PLL clock signal module and D / A conversion module. The FPGA main control chip provides signals to the DDS signal generation module and PLL clock signal module through an external crystal oscillator source. The DDS signal generation module places the data of a complete cycle of square wave signal in the ROM memory. The ROM memory uses the phase code input by the phase modulator as the reading address, multi-channel output, and uses parallel reading to output voltage for the data of the corresponding address. It controls the frequency word input and phase word input of the DDS signal generation module, adjusts the frequency and phase of the generated signal, and each signal output channel adjusts the duty cycle of the signal generated by each path through the PLL clock signal module;

[0007] The signal is converted into an analog signal through a bipolar high-speed D / A conversion module, and 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 to remove stray noise and then passed through a current amplifier 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 to complete the multi-modal matrix current output.

[0009] The multi-mode magnetic field adaptive direction adjustment mechanism includes an array excitation coil at the lower layer and an array Hall magnetic sensor at the upper layer. The magnetic field is generated by the multi-mode array excitation coil with a single excitation source, and the magnetic field intensity is detected by the upper array Hall magnetic sensor. The data of the array Hall magnetic sensor is used to measure the distribution of the regional magnetic field through a filtering 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 approached.

[0010] Preferably, the signal output of each channel of the DDS signal generation module adopts a serial structure of two PLL chips, wherein one chip generates a clock signal of a specific frequency outputted by the corresponding channel as a reference signal input of the second PLL chip, and four clock signals with different duty cycles are pre-set inside the second PLL chip, namely: 10%, 20%, 30%, and 40%. The clock signal adjustment with any duty cycle is achieved through the combination of clock signals, and the PWM modulation signal corresponding to each channel is generated by the two PLL chips, and the duty cycle of the signal generated by each channel of the DDS signal generation module is adjusted.

[0011] A method for generating a multi-mode array magnetic field comprises the following steps:

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

[0013] S2: Based on the output waveform, the bipolar D / A conversion circuit outputs the current I1, I2, I3, etc. of the required waveform. The current amplitude is then adjusted through the amplifier circuit knob, and finally the current output 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, f represents the excitation frequency, Represents the initial phase of the excitation current, the current period is R, and the current duty cycle 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 is generated around the coil. At this time, under the excitation of the alternating current, the magnetic field generated by a coil in one cycle is expressed as:

[0018]

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

[0020]

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

[0022]

[0023] S4: Based on the magnitude of the magnetic field detected by the Hall effect sensor, the current amplitude, frequency, phase, and duty cycle are fed back to the coil to adjust the generated magnetic field gradually toward the target angle magnetic field.

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

[0025] The present invention realizes the signal source of multi-channel multi-mode matrix output based on FPGA main control chip in combination with DDS signal generation module and PLL clock signal module, adjusts the frequency and phase of the output signal, and realizes independent control of the duty cycle of each output by controlling two PLL chips to generate PWM waves. A bipolar high-speed D / A conversion module is designed, and the amplitude of the current is adjusted in combination with a current amplifier circuit; an array coil is designed in combination with a Hall magnetic sensor, and a magnetic field is generated 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. By adjusting the mode of a certain coil, the superposition state of the magnetic field is changed, and the adjustment of the magnetic field focusing direction is realized. According to the value of the Hall magnetic sensor at the upper end of the coil, the magnetic field direction is detected in real time and compared with the sensor data and the theoretical value of the target angle, the excitation mode is dynamically adjusted in real time to complete the generation of multi-mode array magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

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

[0028] Figure 2 This is a diagram showing the frequency, phase, duty cycle, and amplitude adjustment structure of a channel of the present invention;

[0029] Figure 3 It is a schematic diagram of the structure of the array coil and Hall magnetic sensor of the present invention;

[0030] Figure 4 This is a diagram showing the working principle of the Hall effect magnetic sensor according to the present invention;

[0031] Figure 5 This is a schematic diagram of the theoretical multi-modal magnetic field superposition of the present invention. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0034] A multi-mode array magnetic field generating system, comprising a single excitation source matrix excitation and a multi-mode magnetic field adaptive direction adjustment mechanism;

[0035] 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 the data of a complete square wave signal in the ROM memory. The ROM memory uses the phase code input by the phase modulator as the read address. The multi-channel output uses a parallel reading method to output the voltage of the data at the corresponding address. 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. Each signal output channel uses a serial structure of two PLL chips. One chip generates a clock signal of a specific frequency output for the corresponding channel as the reference signal input of the second PLL chip. The second PLL chip has four clock signals with different duty cycles preset inside: 10%, 20%, 30%, and 40%. The clock signal adjustment of any duty cycle is achieved by combining the clock signals. The two PLL chips generate a PWM modulation signal corresponding to each channel to adjust the duty cycle of the signal generated by each path of the DDS signal generation module.

[0036] The signal is converted into an analog signal through a bipolar high-speed D / A conversion module, and 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 to remove stray noise and then passed through a current amplifier 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 to complete 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 magnetic sensor 2 on the upper layer. The magnetic field is generated by the multi-mode array excitation coil with a single excitation source, and the upper array Hall magnetic sensor 2 detects the generated magnetic field strength. The data of the array Hall magnetic sensor 2 is used to measure the distribution of the regional magnetic field through a filtering 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 approached.

[0039] Frequency and phase adjustment are quantified according to the knob rotation angle, 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, recording the frequency corresponding to the current output signal and setting the target duty cycle, generating a PWM modulation waveform for the corresponding channel, and adjusting the duty cycle of each signal; current amplitude and direction adjustment, including bipolar D / A conversion, signal filtering circuit, current amplification circuit and single-pole double-throw switch, is consistent with the frequency and phase adjustment method. The circuit amplification factor is changed by the knob to adjust the amplitude of the excitation current, and the direction of the coil excitation current is adjusted by changing the position of the switch paddle.

[0040] A method for generating a multi-mode array magnetic field comprises the following steps:

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

[0042] S2: Based on the output waveform, the bipolar D / A conversion circuit outputs the current I1, I2, I3, etc. of the required waveform. The current amplitude is then adjusted through the amplifier circuit knob, and 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 current duty cycle 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 is generated around the coil. At this time, under the excitation of the alternating current, the magnetic field generated by a coil in one cycle is expressed as:

[0047]

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

[0049]

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

[0051]

[0052] S4: Based on the magnitude of the magnetic field detected by the Hall effect sensor, the current amplitude, frequency, phase, and duty cycle are fed back to the coil to adjust the generated magnetic field gradually toward the target angle magnetic field.

[0053] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A multi-mode array magnetic field generating system, characterized in that: It includes single excitation source matrix excitation and multi-mode magnetic field adaptive direction adjustment mechanism; Single excitation source matrix excitation, including FPGA main control chip, DDS signal generation module, PLL clock signal module and 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 the data of the square wave signal of a complete cycle in the ROM memory. The ROM memory uses the phase code transmitted by the phase modulator as the reading address, multi-channel output, and uses parallel reading to output the voltage of the data at the corresponding address, control the frequency word input and phase word input of the DDS signal generation module, and adjust the frequency and phase of the generated signal. Each signal output channel adjusts the duty cycle of the signal generated by each path through the PLL clock signal module; The signal is converted into an analog signal through a bipolar high-speed D / A conversion module, and 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 amplifier 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 to complete the multi-modal matrix current output; The multi-mode magnetic field adaptive direction adjustment mechanism includes a lower layer array excitation coil and an upper layer array Hall magnetic sensor. The magnetic field is generated by the single excitation source multi-mode array excitation coil, and the upper layer array Hall magnetic sensor detects the generated magnetic field strength. The data of the array Hall magnetic sensor is used to measure the distribution of the regional magnetic field through a filtering 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 approached.

2. A multi-mode array magnetic field generating system according to claim 1, characterized in that: The signal output of each channel of the DDS signal generation module adopts a serial structure of two PLL chips, one of which generates a clock signal of a specific frequency for the corresponding channel output as the reference signal input of the second PLL chip. Four clock signals with different duty cycles are pre-set inside the second PLL chip: 10%, 20%, 30%, and 40%. The clock signal adjustment of any duty cycle is achieved through the combination of clock signals. The PWM modulation signal corresponding to each channel is generated by the two PLL chips, and the duty cycle of the signals generated by each channel of the DDS signal generation module is adjusted.

3. A multi-mode array magnetic field generation method, characterized in that: The following steps are involved: S1: Select the amplitude, phase, frequency, duty cycle and direction of each channel output of the matrix current of the array single excitation source; S2: According to the output waveform, the bipolar D / A conversion circuit outputs the current I1, I2I3... of the required waveform, and then the current amplitude is adjusted through the amplifier circuit knob, and finally the current output is used to excite the coil; the output current of each channel can be expressed as: 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 R, and the current duty cycle can be expressed as: 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 coil in one cycle is expressed as: From this, the magnetic field generated by the matrix coil can be obtained as: According to the principle of magnetic field vector superposition, the total magnetic field generated by the array coil is: S4: Based on the magnitude of the magnetic field detected by the Hall magnetic sensor, the current amplitude, frequency, phase, and duty cycle are applied to the coil for feedback adjustment, so that the generated magnetic field gradually approaches the target angle magnetic field.

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