CN114994777A - Active suppression method for electromagnetic motion noise in ground-space frequency domain - Google Patents

Abstract

The invention relates to the technical field of geophysical non-destructive exploration, in particular to a method for actively suppressing electromagnetic motion noise in the ground-space frequency domain. According to the exploration depth range, use the skin depth formula to calculate the frequency band range of the main frequency of the transmitting current; adjust the elastic coefficient of the dynamic noise suppression module of the receiving coil sensor, and reduce the natural frequency f of the receiving coil sensor to make it different from the transmitting fundamental frequency f _o1 . Aliasing; read the angular velocity and acceleration of the receiving coil sensor in the pitch and roll directions through the dynamic noise suppression active adjustment module, and adjust the damping coefficient according to the angular velocity and acceleration, and minimize the acceleration of the receiving coil sensor by changing the damping characteristics. The problem of dynamic noise of electromagnetic sensors in the method of ground-air electromagnetic exploration in frequency domain is to be solved.

Description

An active suppression method for electromagnetic motion noise in the ground-air frequency domain

technical field

The invention relates to the technical field of geophysical non-destructive exploration, in particular to a method for actively suppressing electromagnetic motion noise in the ground-space frequency domain.

Background technique

With the rapid and sustainable development of the economy, the problems of resources and energy have become increasingly prominent. With the increase in the demand for resources and energy exploration, the demand for underground exploration has increased year by year. However, the detection efficiency of traditional geophysical exploration methods is low, and it is difficult to meet the demand for resources and energy resources. The demand for rapid exploration in large areas, therefore, it is urgent to realize high-efficiency, high-quality detection devices and construction in areas with complex geological conditions, the combination of ground-air frequency domain electromagnetic method and UAV flight platform, combined with high-power ground electromagnetic method The dual advantages of emission and airborne electromagnetic method for rapid and non-contact acquisition can enter the complex terrain area to carry out large-depth resource exploration. In recent years, it has become a hot spot in the study of geophysical electromagnetic method. Compared with ground and aerial electromagnetic methods, it is more economical, safe and convenient to carry out fine detection of large-depth underground structures in mountainous areas, dense vegetation, water areas and other areas, so it has broad market prospects and application value.

Chinese Patent No. 201510039201 discloses a ground-to-air electromagnetic exploration method in the frequency domain. The method adopts the working mode of ground emission and air reception of electromagnetic wave signals, extracts the frequency spectrum of the signal, and inverts and interprets the underground electrical structure through the apparent resistivity method of the whole area. A new type of electromagnetic exploration method. The transmitting system working on the ground transmits multi-frequency pseudo-random waves to the underground through multiple cascades, and can obtain signals of multiple frequencies once excited, which greatly improves the detection efficiency. The receiving system is mounted on the aircraft and measures the magnetic field over the survey area, which can adapt to the environment with complex surface structure and at the same time weaken the static effect caused by the influence of the near field, and expand the detection range of electromagnetic exploration. The system can correct and compensate the measured magnetic field components under the condition of measuring multiple magnetic field components, which improves the resolution of magnetic field measurement. This method is suitable for deep detection in areas with harsh surface conditions, and has the characteristics of wide detection range, large detection depth and high detection efficiency.

Chinese patent 201710491480 discloses a method and device for synchronously measuring the three-dimensional attitude of a ground-to-air electromagnetic detection coil, which relates to the technical field of ground-to-air electromagnetic method experimental devices. With the aid of the system and the device, the real-time attitude measurement of the receiving coil in the ground-to-air electromagnetic detection and synchronized with the electromagnetic transmission system can be completed. The use of the device can eliminate the error caused by the sudden change of the coil posture, so that the later data processing work can more effectively reflect the actual geological structure. Effective qualitative analysis can be performed for general attitude observation, and the cost is low and easy to use.

Although the ground-air electromagnetic exploration method in the frequency domain can greatly improve the detection efficiency, it does not solve the problem of sensor dynamic noise, and the detection accuracy needs to be improved. The three-dimensional attitude synchronization measurement method and device of the ground-to-air electromagnetic detection coil provides a correction attitude method to eliminate errors, which cannot measure the changing attitude of less than 0.1°, and the dynamic noise is still mixed in the effective signal and cannot be separated. Motion noise cannot be completely suppressed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for actively suppressing electromagnetic motion noise in the ground-space frequency domain, and to solve the dynamic noise problem of the electromagnetic sensor in the ground-space electromagnetic exploration method in the frequency domain.

The present invention is realized in this way,

A method for actively suppressing electromagnetic motion noise in the ground-space frequency domain. The method suppresses noise by adjusting a receiving system, wherein the receiving system includes: a receiving coil sensor, a receiver, a dynamic noise suppression module, and a dynamic noise suppression active adjustment module. The coil sensor is in the shape of a ring, the dynamic noise suppression modules are connected at equal intervals on the ring, and the other ends of the three dynamic noise suppression modules are converged and connected to the receiver. The three dynamic noise suppression modules and the receiving coil sensor An axisymmetric conical structure is formed; the receiver is suspended on the unmanned rotorcraft, and the dynamic noise suppression module adjusts the natural frequency and Amplitude at natural frequency;

The suppression method includes:

According to the exploration depth range, use the skin depth formula to calculate the frequency band range of the main frequency of the emission current;

Adjust the elastic coefficient of the dynamic noise suppression module of the receiving coil sensor, and reduce the natural frequency f of the receiving coil sensor so that it does not alias with the transmitting fundamental frequency f _o1 ;

The dynamic noise suppression active adjustment module reads the angular velocity and acceleration of the receiving coil sensor in the pitch and roll directions, and adjusts the damping coefficient according to the angular velocity and acceleration, and minimizes the acceleration of the receiving coil sensor by changing the damping characteristics.

Further, the dynamic noise suppression active adjustment module includes: an IMU, a controller and a solenoid valve, the IMU detects the vibration of the receiving coil sensor, analyzes the peak value of the power spectrum of the vibration, and makes a difference with the expected vibration value, and the difference value is passed through. The controller calculates and controls the solenoid valve through the fuzzy control method, and changes the opening of the orifice through the solenoid valve, thereby changing the damping coefficient.

Further, the IMU detects the vibration of the receiving coil sensor, analyzes the peak value of the power spectrum of the vibration, and makes a difference with the expected value, which specifically includes:

Stick the IMU horizontally on the receiving coil sensor, read the angular velocities ω _x , ω _y and acceleration α _x , α _y of the receiving coil sensor in pitch and roll directions, and obtain its vibration in the horizontal plane,

ω(t) and α(t) are obtained through FFT to obtain the spectrum Xω(ω) and Xα(ω), and then according to the spectrum, the power spectrum is obtained:

The maximum values Gω(ω ₀ ) and Gα(ω ₀ ) are selected in the power spectrum, and according to their power spectrum,

where ω _s = 2πf _s , W _ω and W _α are the mean power spectral density, and the mean value can be regarded as white noise, as the expected vibration value of the dynamic noise suppression active adjustment module, then

e _ω and e _α are used as the input of the controller.

Further, the input quantities e _ω and e _α of the controller are output as a fuzzy set through fuzzy control, and the center of gravity method is used to take the center of gravity of the area enclosed by the fuzzy membership function curve and the abscissa as the final output value of fuzzy inference. Defuzzification gets the exact output c.

Compared with the prior art, the present invention has the following beneficial effects:

The method of the present invention reduces the dynamic noise to an ideal frequency, and then separates it from the received effective frequency. The present invention can consume the energy generated by the vibration through the damping system in the dynamic noise suppression module, thereby reducing the vibration cutting of the induction coil sensor in the air. The dynamic noise generated by the geomagnetic field line does not introduce electromagnetic interference, and the signal-to-noise ratio of the collected signal is increased without weakening the effective signal, the detection depth of the receiving system is increased, and the improvement cost is low and easy to use.

Description of drawings

Fig. 1 is the schematic diagram of the electromagnetic exploration system in the ground-space frequency domain adopted by the method of the present invention

Fig. 2 is the structure diagram of the receiving system in Fig. 1;

Fig. 3 is the dynamic noise suppression module in Fig. 2;

Fig. 4 is the receiving coil sensor in Fig. 2;

Fig. 5 is the equivalent model of the dynamic noise suppression module in Fig. 3;

FIG. 6 is a schematic diagram of the dynamic noise suppression active adjustment module in FIG. 3;

Fig. 7 is the control flow chart of the dynamic noise suppression active adjustment module in Fig. 3;

8 is a schematic structural diagram of a damping system provided by an embodiment of the present invention;

Among them, 1 unmanned rotorcraft, 2 nylon rope, 3 receiving system, 4 transmitting cable, 5 transmitting system, 31 built-in power supply, 32 receiver, 33 shielded twisted cable, 341 first nylon rope, 342 second nylon rope , 343 Third Nylon Rope, 35 Dynamic Noise Suppression Module, 351 First Spring Damping System, 352 Second Spring Damping System, 353 Third Spring Damping System, 3511 First Ring, 3521 Second Ring, 3531 Third Ring, 3512 1st spring system, 3522 2nd spring system, 3532 3rd spring system, 3513 1st damping system, 3523 2nd damping system, 3533 3rd damping system, 3514 5th ring, 3524 6th ring, 3534 7th ring, 36 receiving coil sensor, 361 eighth ring, 362 ninth ring, 363 tenth ring, 364 receiving coil preamplifier, 365 coil bobbin, 366 induction coil, 37 dynamic noise suppression active adjustment module; 7 solenoid valve; 8 throttle hole.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Referring to FIG. 1 , the method of the present invention is based on a ground-to-air frequency domain detection system. The ground-to-air frequency domain detection system includes an unmanned rotorcraft 1 that mounts a receiving system 3 by hanging a nylon rope 2 , and a transmitting system 5 that transmits cables 4 to the receiving system 3 . Pseudo-random sequence waveforms are transmitted underground, and the transmission power is artificially controllable.

Referring to Figures 2 and 3, the receiving system includes a receiving coil sensor 36, a receiver 32 and a dynamic noise suppression module 35. The receiving coil sensor is annular, and the dynamic noise suppression modules are connected at equal intervals on the annular ring. The other ends of each dynamic noise suppression module are converged and connected to the receiver, the receiver is suspended on the unmanned rotorcraft, wherein the dynamic noise suppression module adjusts the natural frequency of the receiving coil sensor by adjusting its own elastic coefficient and damping coefficient.

The dynamic noise suppression module 35 includes a first spring damping system 351, a second spring damping system 352 and a third spring damping system 353, and is provided with a first hanging ring 3511, a second hanging ring 3521, a third hanging ring 3531, a first hanging rope 341, The second hanging rope 342 and the third hanging rope 343 are connected, and the fifth hanging ring 3514 , the sixth hanging ring 3524 , and the seventh hanging ring 3534 are connected to the eighth hanging ring 361 , the ninth hanging ring 362 , and the tenth hanging ring 363 of the receiving coil sensor 36 . A central axis-symmetric conical structure is formed. The receiving coil sensor is suspended from the upper side of the receiver 32 by the nylon rope 2, the receiver 32 is connected to the receiving coil sensor 364 by the shielded stranded cable 33, and the lower side of the receiver 32 is connected by the first nylon rope 341, the second nylon rope 342, the third The three nylon ropes 343 are connected with the first spring damping system 351 , the second spring damping system 352 and the third spring damping system 353 , and the dynamic noise suppression module 35 can reduce the natural frequency of the receiving coil sensor 36 and absorb the vibration of the receiving coil sensor 36 energy.

The dynamic noise suppression module includes a spring system and a damping system that are coaxially connected in parallel, the damping system includes a first cylinder, a second cylinder with a diameter smaller than the first cylinder is coaxially arranged on the first cylinder, and two ends of the damping system are respectively Connecting rings, one end of the rings is connected to the receiving coil sensor, one end of the rings is connected to the receiver through nylon ropes, and the spring system is sleeved on the first cylinder and the second cylinder. The first spring damping system 351, the second spring damping system 352, and the third spring damping system 353 constitute three dynamic noise suppression modules.

The invention changes the natural frequency of the receiving coil sensor by adjusting the elastic damping coefficient of the dynamic noise suppression module, so that the natural frequency of the receiving coil sensor does not overlap with the transmitting frequency and the effective receiving signal frequency.

Referring to FIG. 4, the receiving coil sensor includes a ring-shaped coil bobbin 365, an induction coil 366 and a coil preamplifier 364. The induction coil is an enameled wire layered and wound on the outside of the coil bobbin to form a differential structure. The output end of the induction coil is connected to the receiving coil. A preamplifier, the receiving coil preamplifier is connected to the receiver through a shielded twisted cable, and the receiver built-in power supply 31 can supply power to the receiver and the receiving coil preamplifier. The coil bobbin is a non-conductive material.

The receiving coil sensor is connected to the first spring damping system 351, the second spring damping system 352, and the third spring damping system 353 through the suspension ring, specifically:

The fifth suspension ring 3514 of the first spring damping system 351 is connected to the eighth suspension ring 361 of the receiving coil sensor 36, the sixth suspension ring 3524 of the second spring damping system 352 is connected to the ninth suspension ring 362 of the receiving coil sensor 36, and the third spring damping The seventh hoisting ring 3534 of the system 353 is connected to the tenth hoisting ring 363 of the receiving coil sensor 36, the first hoisting ring 3511 of the first spring damping system 351 is connected to the first nylon rope 341, and the second hoisting ring 3521 of the second spring damping system 352 is connected to the The second nylon rope 342 is connected, the third suspension ring 3531 of the third spring damping system 353 is connected to the third nylon rope 343, the first nylon rope 341, the second nylon rope 342, and the third nylon rope 343 are connected to the receiver 32 again, The receiver 32 is connected with the receiving coil sensor 36 through a shielded twisted cable 33, and finally the receiver system 3 is suspended through the nylon rope 2 drawn from the unmanned rotorcraft 1;

Before the flight aerial survey, the natural frequency of the receiving coil sensor is changed by adjusting the elastic damping coefficient of the dynamic noise suppression module, so that the natural frequency of the receiving coil sensor does not overlap with the transmitting frequency and the effective receiving signal frequency, specifically:

Adjust the elastic coefficient and 3513 damping coefficient of the first spring system 3512 of the first spring damping system 351, adjust the elastic coefficient of the second spring system 3522 and the first damping system 3523 damping coefficient of the second spring damping system 352, adjust the third spring The elastic coefficient of the third spring system 3532 of the damping system 353 and the damping coefficient of the third damping system 3533, the unmanned rotorcraft 1 suspends the receiving system 3 hovering in the air, the receiving system 3 collects the dynamic noise of the receiving coil sensor 36, analyzes and analyzes it. The spectral characteristics and resonance points of the dynamic noise are determined to ensure that the natural mechanical vibration frequency of the receive coil sensor 36 does not overlap the transmit frequency and the effective receive signal frequency.

During detection, the transmitting system cable 4 is arranged at a distance of 2 to 5 kilometers away from the receiving system 3, and the two electrodes are deeply buried in the ground, and the transmitting system 5 is connected in series. The transmitting system 5 can transmit 3-frequency, 5-frequency, 7-frequency, 9-frequency Frequency pseudo random sequence waveform, the power supply of transmitting system 5 is generated by the generator to generate 380V three-phase alternating current, and then AC-DC is converted into direct current with controllable voltage, according to the detection requirements, select the appropriate transmitting frequency and transmitting voltage;

When the unmanned rotorcraft 1 flies according to the set route of the detection area, the axial direction of the receiving coil sensor 36 is perpendicular to the ground and receives the secondary magnetic field signal generated in the detection area in real time. The receiving coil sensor 36 will vibrate when flying in the air, and its induction The coil 366 will cut the geomagnetic field lines to generate dynamic noise with the same vibration frequency. Through the dynamic noise suppression module 35, the vibration amplitude and vibration frequency in the pitch and roll directions can be reduced, the energy generated by the vibration can be weakened, and the frequency migration of the motion noise can be realized. Separation from the effective frequency magnetic field signal to improve the detection capability of the receiving coil sensor 36;

The receiving coil sensor 36 transmits data in real time to the receiver 32 through the shielded twisted cable 33. The receiver 32 completes the conversion of the analog signal to the digital signal, and stores the signal in the receiver 32; The data collected by the aircraft 32, preliminary analysis of the data spectrum characteristics and signal-to-noise ratio, to confirm whether to change the output power of the launch system 5; if the signal-to-noise ratio of the collected signal is low, the transmission power can be increased, and the detection process can be completed to complete the flight aerial survey task; All data are saved, and data processing personnel analyze the data to obtain effective electromagnetic signals in the frequency domain; draw the apparent resistivity map of the electromagnetic data in the frequency domain.

Among them, before the flight aerial survey, the suspension ring of the dynamic noise suppression module is connected with the suspension ring of the receiving coil sensor, the receiver 32 and the receiving coil sensor 36 are connected through the shielded twisted cable 33, and finally the nylon rope 2 drawn from the unmanned rotorcraft 1 is used. Pendant receiver system 3.

Referring to Figure 5, before the aerial survey, adjust the elastic coefficient of the spring system of the dynamic noise suppression module. Taking the vertical direction as an example, set the acceleration of the Z-component receiving coil sensor as a, the mass as m, and the vibration frequency as f. In order to simplify the system Mathematical model, considering the dynamic noise suppression module 35 as a whole, its mathematical model is a spring mass damping system, and the motion differential equation of the forced vibration of the system can be summarized as

The response equation of the system is

c The damping coefficient of the dynamic noise suppression module 35, k the elastic coefficient of the dynamic noise suppression module 35, and the natural mechanical frequency of the receiving coil sensor 36 is

Since the mass of the coil sensor is determined, the natural frequency of the receiving coil sensor 36 can be lowered by reducing the elastic damping coefficient k.

The damping ratio of the system is

The dynamic noise suppression active adjustment module can independently realize the optimal adjustment of the damping coefficient c.

The unmanned rotorcraft 1 suspends the receiving system 3 hovering in the air, the receiving system 3 collects the dynamic noise of the receiving coil sensor 36, analyzes and determines the spectral characteristics and resonance point of the dynamic noise, and ensures that the natural mechanical vibration frequency of the receiving coil sensor 36 is the same as that of the receiving coil sensor 36. The transmit frequency and the effective receive signal frequency do not overlap.

According to the exploration depth range, use the skin depth formula (5) to determine the frequency band range of the main frequency of the emission current:

δ is the exploration depth, ρ is the uniform half-space resistivity, f _o is the launch angular frequency, and the launch fundamental frequency f _o1 .

Reduce the natural frequency f of the receiving coil sensor 36 so that the frequency does not overlap with the transmitting fundamental frequency f _o1 , so that the detection depth can be increased. After being buried underground, the transmitter system 5 is connected in series. The transmitter system 5 can transmit 3-frequency, 5-frequency, 7-frequency, and 9-frequency pseudo-random sequence waveforms. The power supply of the transmitter system 5 is generated by the generator to generate 380V three-phase alternating current and then converted into voltage by AC-DC. Controllable direct current, according to the detection needs, select the appropriate transmission frequency and transmission voltage. When the unmanned rotorcraft 1 flies according to the set route of the detection area, the axial direction of the receiving coil sensor 36 is perpendicular to the ground and receives the secondary magnetic field signal generated in the detection area in real time. The receiving coil sensor 36 will vibrate when flying in the air, and its induction The coil 366 will cut the geomagnetic field lines to generate dynamic noise with the same vibration frequency. The dynamic noise suppression module 35 can reduce the vibration amplitude and vibration frequency in the pitch and roll directions, weaken the energy generated by the vibration, and realize the frequency migration of the motion noise. Separation from the effective frequency magnetic field signal improves the detection capability of the receiving coil sensor 36 .

The receiving coil sensor 36 transmits data to the receiver 32 in real time through the shielded twisted cable 33 . The receiver 32 completes the conversion of the analog signal to the digital signal, and stores the signal in the receiver 32 .

After the flight aerial survey task is completed, the data collected by the receiver 32 is extracted, and the spectral characteristics and signal-to-noise ratio of the data are preliminarily analyzed to confirm whether the output power of the transmitting system 5 is changed.

Save all the data, analyze the data by the data processing personnel, obtain the effective electromagnetic signal in the frequency domain, and draw the apparent resistivity map of the electromagnetic data in the frequency domain.

Referring to FIG. 6 , a dynamic noise suppression active adjustment module 37 is added to the above-mentioned system, and is added to the three spring damping systems for adjusting the damping size of the spring damping system. The dynamic noise suppression active adjustment module includes: IMU (Inertial Measurement Unit) ), a controller and a solenoid valve, wherein, the IMU detects the vibration of the coil bobbin, analyzes the peak value of the power spectrum of the vibration, and makes a difference with the expected value. The difference is calculated by the controller and controlled by the fuzzy control method. The solenoid valve device changes the throttle The opening of the hole finally realizes the active control of the size of the damping. Referring to FIG. 8 , it is a schematic diagram of the structure of the damping system used.

The natural vibration frequency f of the receiving coil sensor is generally within 50Hz. When the natural frequency can be adjusted by the spring system, it is within 10Hz, so the sampling frequency can be f _s >2f.

Stick the IMU horizontally on the coil bobbin, read the angular velocity ω _x , ω _y and acceleration α _x , α _y in the pitch and roll directions of the coil bobbin, and get its vibration in the horizontal plane,

ω(t) and α(t) are obtained through FFT to obtain the spectrum Xω(ω) and Xα(ω), and then according to the spectrum, the angular velocity power spectrum and the acceleration power spectrum are obtained:

In the power spectrum, the maximum value Gω(ω ₀ ) of the angular velocity power spectrum and the maximum value Gα(ω ₀ ) of the acceleration power spectrum are respectively selected, and according to their power spectrum, the

where ω _s = 2πf _s , W _ω and W _α are the mean power spectral density, and the mean value can be regarded as white noise, as the expected vibration value of the dynamic noise suppression active adjustment module, then

是将差值将其比例化，这样e_ω和e_α输出值为(0-100)％，例如：当振动很大时，Gα(ω)和Gω(ω)值会很大，那么

的值会趋近于100％(代表振动很大)，当几乎没有振动时，

中W_α≈Gα(ω)，值几乎趋近于0(代表振动很小)。e _ω and e _α are used as the input of the controller. W _ω and W _α are used as reference quantities. The purpose of Gω(ω ₀ ) and Gα(ω ₀ ) is to approach the values of W _ω and W _α . Gα(ω)-W _α is used to calculate the difference. The difference between the two approaches almost 0.

is to scale the difference so that the output values of e _ω and e _α are (0-100)%, for example: when the vibration is large, the Gα(ω) and Gω(ω) values will be large, then

The value of will approach 100% (representing a lot of vibration), when there is almost no vibration,

where W _α ≈ Gα(ω), the value is almost close to 0 (representing very little vibration).

The input quantities e _ω and e _α are divided into three subsets, respectively, and the corresponding expression relationship of e _ω is: small angular velocity (S _ω ), moderate angular velocity (M _ω ), and large angular velocity (L _ω ), the corresponding expression relationship of e _α are: small acceleration (S _α ), moderate acceleration (M _α ), and large acceleration (L _α ). The output value c is divided into 5 subsets, and the corresponding expressions are: small damping (VS _C ), small damping (S _C ), moderate damping (M _C ), large damping (L _C ), and large damping (VL _C ) ).

e _ω = {S _ω M _ω L _ω }

e _α = {S _α M _α L _α }

C={VS _C S _C M _C L _C VL _C }

Set the input and output variable membership functions as triangular membership functions.

When the coil bobbin vibrates, the IMU will detect the vibration, and the dynamic noise suppression active adjustment module will minimize the acceleration of the coil bobbin by changing the damping characteristics. The minimum here refers to approaching zero to ensure the stability of the receiving coil sensor. , therefore, the control rule of the active adjustment module for receiving dynamic noise suppression is:

Rule 1: When the angular velocity and acceleration are large, the damping force output of the controller is large;

Rule 2: When the angular velocity and acceleration are moderate, the damping force output of the controller is moderately damped;

Rule 3: When the angular velocity and acceleration are small, the damping force output of the controller is small;

This control strategy adopts a two-dimensional fuzzy controller algorithm. The input linguistic variable e _ω is the error of the system, the input linguistic variable e _α is the rate of change of the system error, and the output fuzzy linguistic variable C is the output variable of the fuzzy controller. The fuzzy obtains the precise quantity c, and the fuzzy control rule is described by the fuzzy rule table 1.

Table 1 Fuzzy control rule table

Therefore, the fuzzy controller has a total of 9 rules, namely

According to the fuzzy inference synthesis rules, we can get:

Since the output of fuzzy control is a fuzzy set, it represents the combination of different membership values of the control quantum universe to the fuzzy set. When the controlled object can only accept one control, a precise control quantity needs to be determined from the obtained fuzzy subset. Using the center of gravity method, it takes the center of gravity of the area enclosed by the fuzzy membership function curve and the abscissa as the final output value of fuzzy inference, and finally obtains the precise output value c through defuzzification.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within the range.

Claims (4)

1. An active suppression method for electromagnetic motion noise in a ground-space frequency domain is characterized in that the method suppresses noise by adjusting a receiving system, wherein the receiving system comprises: the receiving coil sensor is in a ring shape, the dynamic noise suppression modules are connected to the ring shape at equal intervals, the other ends of the three dynamic noise suppression modules are connected to the receiver in a gathering mode, and the three dynamic noise suppression modules and the receiving coil sensor form an axisymmetric cone structure; the receiver is suspended on the unmanned gyroplane, and the dynamic noise suppression module adjusts the natural frequency of the receiving coil sensor and the amplitude value at the natural frequency by adjusting the elastic coefficient of the dynamic noise suppression module and adjusting the damping coefficient of the dynamic noise suppression active adjusting module;

the inhibition method comprises the following steps:

calculating the frequency band range of the transmitting current main frequency by using a skin depth formula according to the exploration depth range;

adjusting the elastic coefficient of the dynamic noise suppression module of the receiving coil sensor, and reducing the natural frequency f of the receiving coil sensor to the transmitting fundamental frequency f _o1 No aliasing occurs;

the dynamic noise suppression active adjustment module reads the angular velocity and the acceleration of the pitch direction and the roll direction of the receiving coil sensor, adjusts the damping coefficient according to the angular velocity and the acceleration, and enables the acceleration of the receiving coil sensor to be minimum by changing the damping characteristic.

2. The active earth-space frequency domain electromagnetic motion noise suppression method according to claim 1, wherein the active dynamic noise suppression adjustment module comprises: the IMU detects the vibration condition of the receiving coil sensor, analyzes the power spectrum peak value of the vibration, makes a difference with an expected vibration value, calculates the difference value through the controller, controls the electromagnetic valve through a fuzzy control method, and changes the opening degree of the throttling hole through the electromagnetic valve so as to change the damping coefficient.

3. The active suppression method for electromagnetic motion noise in the ground-space frequency domain according to claim 2, wherein the IMU detects the vibration of the receiver coil sensor, analyzes the peak of the power spectrum of the vibration, and differentiates the peak from an expected value specifically comprises:

horizontally sticking the IMU on a receiving coil sensor, and reading the angular velocity omega of the receiving coil sensor in the pitching direction and the rolling direction _x ,ω _y And acceleration a _x ,α _y So as to obtain the vibration of the water-bearing glass on a horizontal plane,

obtaining frequency spectrums X omega (omega) and X alpha (omega) through FFT of omega (t) and alpha (t), and obtaining a power spectrum according to the frequency spectrums:

selecting the maximum G omega (omega) in the power spectrum ₀ ) And G α (ω) ₀ ) And from its power spectrum

Wherein ω is _s ＝2πf _s ，W _ω And W _α Is the mean value of the power spectral density, the mean value of which can be regarded as white noise, and is taken as the expected vibration value of the dynamic noise suppression active adjustment module, then

e _ω And e _α As an input to the controller.

4. Method for active suppression of electromagnetic motion noise in the earth-space frequency domain according to claim 3, characterized in that the input e of the controller is adjusted _ω And e _α The output is a fuzzy set through fuzzy control, the gravity center of the area enclosed by the fuzzy membership function curve and the abscissa is taken as a final output value of fuzzy reasoning by adopting a gravity center method, and finally the accurate output quantity c is obtained through fuzzy solution.

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