A dynamic noise active suppression suspension system for airborne electromagnetic surveying

Abstract

This invention discloses a dynamic noise active suppression suspension system for air-to-ground electromagnetic detection, belonging to the field of geophysical exploration technology. It includes a coil vibration suppression system connected to a UAV, a receiving coil sensor, and a coil attitude control system. The coil vibration suppression system is connected to the pitch frame of the coil attitude control system via a carbon fiber tube assembly. The pitch frame is connected to the receiving coil sensor via two roll shafts. One roll shaft is connected to a first motor, and a second motor is mounted on the frame edge of the pitch frame perpendicular to the roll shaft. Both the first and second motors are connected to a controller. The coil vibration suppression system suppresses the vibration amplitude of the receiving coil and absorbs the motion noise generated by the receiving coil vibration. The controller collects and controls the first and second motors to adjust the attitude of the receiving coil, suppressing the motion noise generated by the attitude change of the receiving coil. This application significantly reduces the motion noise of air-to-ground transient electromagnetic reception data, enabling low-noise detection using air-to-ground transient electromagnetic methods in complex environments.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration technology, and in particular relates to a dynamic noise active suppression suspension system for ground-to-air electromagnetic detection method. Background Technology

[0002] In recent years, with the sustained and rapid economic development, the contradiction between resource supply and demand has become increasingly prominent, hindering socio-economic development to some extent. The demand for underground exploration has been increasing year by year. However, traditional geophysical exploration methods are inefficient and struggle to achieve high-efficiency, high-quality exploration and construction in areas with complex geological conditions. The ground-to-air transient electromagnetic method uses a long conductor source as the transmitter on the ground and a UAV carrying a receiving coil to receive the secondary field. It combines the advantages of high-power transmission from ground-based electromagnetic methods and the wide-area, flexible reception of airborne electromagnetic methods. It possesses the ability to conduct geological exploration in harsh environments, offering better terrain adaptability compared to ground-based electromagnetic methods and greater detection depth compared to airborne electromagnetic methods.

[0003] In the air-to-ground transient electromagnetic method (ETM), the receiving coil is the core component of the exploration system, suspended on a drone. During flight, the drone is affected by factors such as airflow and wind direction, causing changes in the roll and pitch angles of the receiving coil. This alters the induced magnetic flux due to the cutting of the Earth's magnetic field, resulting in motion noise in the acquired secondary field. This reduces the accuracy of subsequent inversion interpretation. Given the high-precision detection requirements of the ETM method, suppressing motion noise from the receiving coil is particularly crucial.

[0004] The invention patent application with publication number CN113341469A discloses a method and system for correcting semi-airborne transient electromagnetic data. By performing polynomial fitting on single-cycle semi-airborne transient electromagnetic data excluding effective data segments, and resampling all data points according to the obtained fitting equation, noise reduction of motion is achieved. The attitude correction of the filtered semi-airborne transient electromagnetic data is performed based on the three-axis attitude angle of the receiving coil and the deflection of the reference coordinate system, thus realizing the motion attitude correction of the receiving coil.

[0005] The invention patent application with publication number CN115576017A discloses a method and system for noise correction of a receiving coil using an electrical source semi-airborne transient electromagnetic method. Based on the positional changes of the receiving coil, the coupling changes between the receiving coil and the ground are obtained, thereby obtaining the motion noise generated by the induced voltage in the receiving coil and realizing the motion noise correction of the receiving coil.

[0006] Currently, existing methods for suppressing motion noise in the receiving coil of the ground-to-air transient electromagnetic method mainly rely on denoising the signal acquired by the receiving coil using denoising algorithms to improve the signal-to-noise ratio. However, these methods do not suppress noise at the noise source, and subsequent data processing may distort the effective signal, making it difficult to completely remove motion noise from the secondary field signal. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a dynamic noise active suppression suspension system based on the ground-to-air electromagnetic detection method.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] This invention discloses a dynamic noise active suppression suspension system based on the ground-to-air electromagnetic detection method, comprising a receiving coil sensor, a coil vibration suppression system, and a coil attitude control system.

[0010] The coil attitude control system includes a controller, first and second motors, and a pitch frame. The coil vibration suppression system is connected to the pitch frame via a carbon fiber tube assembly. The pitch frame is connected to the receiving coil sensor via two symmetrical roll axes. One roll axis is connected to the first motor, and a second motor is installed on the frame edge of the pitch frame perpendicular to the roll axis. Both the first and second motors are connected to the controller. The coil vibration suppression system is connected to the UAV via a lanyard. The coil vibration suppression system suppresses the vibration amplitude of the receiving coil and absorbs the motion noise generated by the vibration of the receiving coil. The controller collects and controls the first and second motors to adjust the attitude of the receiving coil and suppress the motion noise generated by the attitude change of the receiving coil.

[0011] Furthermore, the receiving coil sensor includes a receiving coil and a preamplifier, with the output terminal of the receiving coil connected to the input terminal of the preamplifier, and the output terminal of the preamplifier connected to the receiver.

[0012] Furthermore, the receiving coil has four winding channels on its frame, with silver-plated wire wound on the upper two winding channels and the lower two winding channels respectively, forming an upper winding group and a lower winding group. The silver-plated wire winding paths of the upper winding group and the lower winding group are the same.

[0013] Furthermore, the preamplifier includes a signal damping matching circuit, a signal amplification circuit, and a voltage follower circuit. The input terminal of the signal damping matching circuit is connected to the upper and lower winding groups of the receiving coil, respectively. The output terminal of the signal damping matching circuit is connected to the input terminal of the signal amplification circuit. The output terminal of the signal amplification circuit is connected to the input terminal of the voltage follower circuit. The output terminal of the voltage follower circuit is connected to the receiver.

[0014] Furthermore, the coil vibration suppression system includes a connecting frame and four sets of shock-absorbing components arranged at the four corners of the connecting frame. Each set of shock-absorbing components includes a base, a shock-absorbing column, and a hanging ring. The bottom of the shock-absorbing column is provided with a base and is connected to the connecting frame through the base. The top of the shock-absorbing column is connected to the hanging ring. The four sets of hanging rings are connected by hanging ropes and suspended below the drone, so that the hanging rings and hanging ropes form a four-sided pyramid structure.

[0015] Furthermore, one end of each of the two roll shafts is symmetrically connected to the receiving coil, the other end of one roll shaft is connected to the pitch frame, and the other end of the other roll shaft passes through the pitch frame and connects to the output shaft of the first motor. The roll angle of the receiving coil is controlled by the first motor. The pitch angle of the pitch frame and the receiving coil is controlled by the second motor connected to the pitch frame.

[0016] Furthermore, the controller includes a microcontroller chip, a keyboard, a display screen, a GPS clock synchronization module, an IMU module, and an SD card module. The IMU module is used to detect the roll and pitch angles of the receiving coil. The microcontroller chip is connected to the display screen, keyboard, IMU module, SD card module, and the first and second motors respectively. The controller parameters are set through the display screen and keyboard. The microcontroller chip collects the roll and pitch angles of the receiving coil through the IMU module and writes them to the SD card module. The microcontroller chip calculates the angle correction value and controls the first and second motors to rotate by the corresponding angle.

[0017] Furthermore, the IMU module is mounted on the receiving coil, and the rotation angles of the first and second motors are controlled based on the roll angle and pitch angle correction values ​​of the receiving coil obtained from the attitude information collected by the IMU module; the attitude information includes the roll angle and pitch angle.

[0018] Furthermore, the control method of the coil attitude control system includes:

[0019] Obtain the roll angle and pitch angle parameters of the receiving coil;

[0020] Based on the roll angle parameters and pitch angle parameters, determine the first difference of roll angle and the second difference of pitch angle. The first difference is the difference between the actual value and the expected value of roll angle, and the second difference is the difference between the actual value and the expected value of pitch angle.

[0021] The fractional-order PID controller determines the roll angle correction value based on the first difference and the pitch angle correction value based on the second difference; it controls the rotation angle of the first motor and the second motor to adjust the attitude of the receiving coil.

[0022] Furthermore, the determination of the correction values ​​for the roll angle and pitch angle:

[0023] Substituting the first difference and the second difference into the fractional-order PID controller, respectively, yields the correction value for the roll angle. and the correction value of the pitch angle ; ,

[0024] In the formula, It is the first difference. It is the second difference. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the roll axis. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the pitch frame rotation axis.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. This invention addresses the motion noise problem caused by system vibration during flight of the receiving coil sensor. It designs a coil vibration suppression system that absorbs motion noise generated by system vibration through damping columns. Furthermore, it addresses the motion noise problem caused by changes in the receiving coil sensor's attitude during flight by using a servo motor to correct the receiving coil's attitude. This invention can significantly reduce motion noise in air-to-ground transient electromagnetic data reception. It enables low-noise detection using air-to-ground transient electromagnetic methods in complex environments, which will help broaden the application scope of electromagnetic resource exploration technology and improve detection accuracy.

[0027] 2. To address the problem of high background noise in receiving coil sensors, this invention employs a multi-segment receiving coil frame structure and low-noise signal amplification technology to reduce the background noise of the receiving coil sensor.

[0028] 3. The dynamic noise active suppression suspension system of the ground-to-air electromagnetic detection method of the present invention replaces the traditional receiving coil suspension method, reduces the degree of freedom of motion of the receiving coil, reduces the dynamic noise caused by the vibration and attitude change of the receiving coil during the flight of the UAV, and improves the signal-to-noise ratio of the received induced electromagnetic response signal.

[0029] 4. This invention replaces the original integer-order PID controller algorithm with a fractional-order PID controller algorithm and optimizes parameters using a genetic algorithm, thereby enhancing the system's anti-disturbance capability and solving the problems of complex and slow parameter tuning of fractional-order PID controllers. Attached Figure Description

[0030] Figure 1 This is a structural schematic diagram of one embodiment of the hanging method provided by the present invention.

[0031] Figure 2 This is a circuit diagram of one embodiment of the preamplifier in this invention.

[0032] Figure 3 This is a schematic diagram of one embodiment of the controller in this invention.

[0033] Figure 4 A schematic diagram of the structure of one embodiment of the mathematical model of the present invention.

[0034] Figure 5 This is a schematic diagram of one embodiment of the fractional-order PID control of the present invention.

[0035] Figure 6 The figure shows the Simulink simulation results of the fractional-order PID controller of the present invention.

[0036] In the diagram: 1. UAV; 2. Suspension rope; 3. Controller; 4. Coil vibration suppression system; 41. Suspension ring; 42. Vibration damping column; 43. Base; 44. Carbon fiber tube assembly; 45. Connecting plate; 46. Support plate; 47. Fixing plate; 48. Adapter plate; 5. Receiving coil sensor; 51. Receiving coil; 52. Preamplifier; 6. Coil attitude control system; 61. Roll axis; 62. Pitch frame; 63. First motor; 64. Second motor; 65. First power supply; 66. Second power supply; 7. Receiver;

[0037] Matching resistor - R m1 Matching resistor R m2 Electromagnetic signal input interface V in + Electromagnetic signal input interface V in Operational Amplifier 1 (A1), Operational Amplifier 2 (A2), Operational Amplifier 3 (A3), Resistor 1 (R1), Resistor 2 (R2), Resistor 3 (R3), Resistor 4 (R3), Resistor 5 (R5), Resistor 6 (R6), Capacitor 1 (C1), Capacitor 2 (C2), Electromagnetic Signal Output Interface V out + Electromagnetic signal output interface V out - Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The step numbers in the following embodiments are only for ease of explanation, and there is no limitation on the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0039] like Figure 1 As shown, this invention is a dynamic noise active suppression suspension system based on the ground-to-air electromagnetic detection method, comprising a receiving coil sensor 5, a coil vibration suppression system 4, and a coil attitude control system 6.

[0040] The coil attitude control system 6 includes a controller 3, a first motor 63, a second motor 64, and a pitch frame 62. The coil vibration suppression system 4 is connected to the pitch frame 62 via a carbon fiber tube assembly. The pitch frame 62 is connected to the receiving coil sensor 5 via two symmetrical roll axes 61. One of the roll axes 61 is connected to the first motor 63. The second motor 64 is installed on the frame of the pitch frame 62 perpendicular to the roll axis 61. Both the first motor 63 and the second motor 64 are connected to the controller 3. The coil vibration suppression system 4 is connected to the UAV 1 via a suspender rope 2. The coil vibration suppression system 4 suppresses the vibration amplitude of the receiving coil 51 and absorbs the motion noise generated by the vibration of the receiving coil 51. The controller 3 collects and controls the first motor 63 and the second motor 64 to adjust the attitude of the receiving coil 51 and suppress the motion noise generated by the attitude change of the receiving coil 51.

[0041] In the air-to-ground electromagnetic method, the UAV 1 is equipped with a suspension rope 2 (a nylon rope is used in this example), which is connected to the hanging ring 41 on the coil vibration suppression system 4 of this invention, suspending the invention in the air. The induced electromagnetic response signal is collected by the receiving coil sensor 5. During the flight of the UAV 1, the receiving coil 51 of the receiving coil sensor 5 will vibrate at a certain frequency and change its attitude due to the influence of factors such as the UAV 1's motion attitude and airflow. The coil vibration suppression system 4 of this invention can suppress the motion noise caused by the vibration of the receiving coil 51, and the coil attitude control system 6 can suppress the motion noise caused by the attitude change of the receiving coil 51, effectively reducing the dynamic noise of the receiving coil 51 moving in the air.

[0042] Specifically, such as Figure 1As shown, the coil vibration suppression system 4 includes a connecting frame and four sets of shock-absorbing components set at the four corners of the connecting frame. Each set of shock-absorbing components includes a base 43, a shock-absorbing column 42, and a hanging ring 41. The shock-absorbing column 42 (an existing purchased component) has a base 43 at its bottom and a hanging ring 41 connected to its top. The four sets of hanging rings 41 are connected by a hanging rope 2 and suspended below the UAV 1, so that the hanging rings 41 and the hanging rope 2 form a four-sided pyramid structure.

[0043] Specifically, in this example, the connecting frame is a rectangular frame structure formed by connecting the base 43 to four connecting plates 45. A fixing plate 47 is set in the middle of the rectangular frame. Support plates 46 are connected to the base 43 and the two symmetrical connecting plates 45 on the outer periphery of the fixing plate 47. Carbon fiber tube assemblies 44 connected to the pitch frame 62 are connected to the other two symmetrical sides of the fixing plate 47. The carbon fiber tube assembly 44 is an L-shaped bent structure, with the carbon fiber tube assembly 44 connected to the two right-angled sides of the adapter plate 48. One end of the carbon fiber tube assembly 44 is connected to the fixing plate 47, and the other end is connected to the pitch frame 62. The adapter plate 48 is fixed on its corresponding connecting plate 45. In this example, the carbon fiber tube assembly 44 consists of three carbon fiber tubes arranged side by side. When the pitch frame 62 rotates, it drives the receiving coil 51 to rotate synchronously. The carbon fiber tube assembly 44 drives the connecting frame to rotate, and the vibration amplitude generated by the pitch frame 62 and the receiving coil 51 is suppressed by the damping column 42, absorbing the motion noise generated by the vibration of the receiving coil 51.

[0044] Specifically, the receiving coil sensor 5 includes a receiving coil 51 and a preamplifier 52. The signal output terminal of the receiving coil 51 is connected to the input terminal of the preamplifier 52, and the signal output terminal of the preamplifier 52 is connected to the receiver 7. The receiver 7 collects the amplified signal.

[0045] The receiving coil 51 has four winding channels on its frame. The upper two winding channels and the lower two winding channels are respectively wound with silver-plated wire (silver-plated wire has the characteristics of corrosion resistance and low noise, ensuring measurement accuracy in harsh environments), forming an upper winding group and a lower winding group. The silver-plated wire winding paths of the upper winding group and the lower winding group are the same.

[0046] Reference Figure 2 As shown, the signal damping matching circuit includes a matching resistor R. m1 Matching resistor R m2 Electromagnetic signal input interface V in + Electromagnetic signal input interface V in - The matching resistor R m1 Both ends are connected to electromagnetic signal input interfaces V. in + and ground, matching resistor 2R m2 Both ends are connected to electromagnetic signal input interfaces V. in - and ground wire; the matching resistor Rm1 The end connected to the ground wire is connected to the matching resistor R. m2 Connect to the end that is connected to the ground wire. The electromagnetic signal input interface V... in + Connects to the upper end of the upper winding assembly; Electromagnetic signal input interface V in - Connect the lower end of the lower winding assembly, and connect the lower end of the upper winding assembly to the upper end of the lower winding assembly and the ground wire.

[0047] The signal amplification circuit includes operational amplifier A1, operational amplifier A2, resistors R1 and R5, capacitors C1 and C2. Resistor R1 and capacitor C1 are connected in parallel, with one end connected to the inverting input of operational amplifier A1 and the other end connected to its output. Resistor R2 and capacitor C2 are connected in parallel, with one end connected to the inverting input of operational amplifier A2 and the other end connected to its output. Resistor R3 is connected with one end to the inverting input of operational amplifier A1 and the other end to the inverting input of operational amplifier A2. The electromagnetic signal input interface V... in +Connect to the positive input terminal of the operational amplifier A1, the electromagnetic signal input interface V in - Connect one end of the resistor R4 to the inverting input terminal of the operational amplifier A2, and connect one end of the resistor R5 to the output terminal of the operational amplifier A1.

[0048] The voltage follower circuit includes an operational amplifier 3A3, a resistor 6R6, and an electromagnetic signal output interface V. out + Electromagnetic signal output interface V out - The other end of resistor R4 is connected to the positive input terminal of operational amplifier A3, the other end of resistor R5 is connected to the inverting input terminal of operational amplifier A3, and the two ends of resistor R6 are connected to the two ends of operational amplifier A3, controlling the amplification factor of operational amplifier A3 to be 1, achieving voltage following. The two output terminals of operational amplifier A3 are, in sequence, the electromagnetic signal output terminal V. out + The electromagnetic signal output terminal V out - Connect to receiver 7 respectively.

[0049] like Figure 3As shown, the controller 3 includes a microcontroller (MCU), a keyboard, a display screen, a GPS clock synchronization module, an IMU module, and an SD card module. The IMU module is installed on the receiving coil sensor 5 and is used to detect the roll angle and pitch angle of the receiving coil 51. The MCU is an ARM architecture STM32 microcontroller and is the core of the controller. The MCU is connected to the display screen, keyboard, IMU module, SD card module, first motor 63, and second motor 64. The parameters of the controller 3 can be set through the display screen and keyboard, including but not limited to the clock synchronization method, sampling frequency, and number of sampling points. The MCU and IMU module communicate via IIC (interchangeable IC) to acquire the roll angle and pitch angle of the receiving coil 51 and write the roll angle and pitch angle into the SD card module. The MCU calculates the angle correction value and communicates with the first motor 63 and the second motor 64 via RS485 bus to control the first motor 63 and the second motor 64 to rotate the corresponding angle.

[0050] Both the first motor 63 and the second motor 64 are servo motors, which are motors capable of precisely adjusting their angle and position according to control signals. PWM (Pulse Width Modulation) is a commonly used control method used to control the rotation of a motor by adjusting the width of a pulse signal. After receiving instructions sent via RS485, the servo motor can generate corresponding PWM pulse signals. By using the PWM control principle, the angle and position of the servo motor can be precisely controlled, achieving accurate motion control. The roll axis 61 of the receiving coil 51 is connected to the output shaft of the first motor 63, and is connected to the frame of the pitch frame 62 perpendicular to the roll axis 61 and the output shaft of the second motor 64. The rotation of the first motor 63 and the second motor 64 can drive the rotation of the roll axis 61 and the pitch frame 62, thereby realizing the change of the attitude angle of the receiving coil 51.

[0051] The first motor 63 is connected to the first power supply 65, and the second motor 64 is connected to the second power supply 66.

[0052] The two roll shafts 61 are symmetrically connected at one end to the receiving coil 51. The other end of one roll shaft 61 is rotatably connected to the pitch frame 62, and the other end of the roll shaft 61 passes through the pitch frame 62 and connects to the output shaft of the first motor 63. The first motor 63 controls the roll angle of the receiving coil 51. The second motor 64 connected to the pitch frame 62 controls the pitch angle of the pitch frame 62 and the receiving coil 51 connected to it. The IMU module of the controller 3 is set on the receiving coil 51. Based on the roll angle and pitch angle correction values ​​obtained from the attitude information of the receiving coil 51 collected by the IMU module, the controller controls the rotation angle of the first motor 63 and the second motor 64. The attitude information includes the roll angle and the pitch angle.

[0053] The controller 3 synchronizes the clock via a GPS satellite timing unit, including satellite timing, second pulse signal synchronization, and reading in the standard time and location information from the satellite timing.

[0054] During the flight of UAV 1, after the MCU receives the second pulse signal from GPS, it collects the current roll and pitch angles of the receiving coil 51 and writes them to the SD card module. It then calculates the first difference and the second difference based on the current angle and the desired angle, and compares them with a rotation threshold. If the first difference and the second difference are greater than the rotation threshold, it indicates that the current angle of the receiving coil 51 affects the accuracy of the collected induced electromagnetic response signal, and the attitude of the receiving coil 51 needs to be corrected. The MCU generates corresponding control commands and sends them to the first motor 63 and the second motor 64 via RS485. After receiving the control commands, the first motor 63 and the second motor 64 generate corresponding PMW pulse signals, driving the roll axis 61 and the pitch frame 62 to rotate by the corresponding angle, thus correcting the attitude of the receiving coil 51.

[0055] The control method of the coil attitude control system 6 of the present invention is used to adjust the attitude of the receiving coil 51, including:

[0056] Obtain the roll angle and pitch angle parameters of the receiving coil 51;

[0057] Based on the roll angle and pitch angle parameters, the attitude of the receiving coil 51 is adjusted by a fractional-order PID controller, including:

[0058] Determine a first difference and a second difference, where the first difference is the difference between the actual value and the expected value of the roll angle, and the second difference is the difference between the actual value and the expected value of the pitch angle;

[0059] To further reduce the motion noise of the receiving coil 51, a fractional-order PID controller is used to determine the correction value of the roll angle corresponding to the first difference and the correction value of the pitch angle corresponding to the second difference. The roll angle is the angle at which the receiving coil 51 rotates, and the pitch angle is the angle at which the pitch frame 62 rotates. The pitch frame rotation axis is the axis on which the second motor 64 drives the pitch frame 62 to rotate.

[0060] Substituting the first difference and the second difference into the fractional-order PID controller, respectively, yields the correction value for the roll angle. and the correction value of the pitch angle ;

[0061] In the formula, It is the first difference. It is the second difference. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the roll axis. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the pitch frame rotation axis.

[0062] like Figure 4 The diagram shown illustrates a structural embodiment of the present invention based on a fractional-order PID controller. According to the physical characteristics of the suspension system of the present invention (total moment of inertia)... The electrical parameters of the first motor 63 and the second motor 64, including the torque coefficients of the first and second motors. proportionality coefficient The transfer function of the suspension system is obtained as follows:

[0063] The first motor 63 and the second motor 64 have the same voltage parameters, and their input voltages are both... The current generated in the circuit is The energized armature rotor winding produces an electromagnetic torque under the influence of the magnetic field of the excitation winding. .

[0064] From Kirchhoff's laws, the voltage balance equation is obtained, as shown in formula (1): (1),

[0065] In the formula, It is the back electromotive force generated when the armature rotates. For armature inductance, For armature resistance, and angular velocity The specific relationship is shown in formula (2):

[0066] (2),

[0067] In the formula, It is the proportionality coefficient. .

[0068] The electromagnetic torque generated by the armature current is specifically shown in formula (3):

[0069] (3),

[0070] In the formula, For the electromagnetic torque of the first / second motor 63 / 64, The torque coefficients of the first / second motor are 63 / 64. .

[0071] Based on Newton's laws, the torque balance equations on the output shafts of the first / second motors 63 / 64 are derived, as shown in formula (4):

[0072] (4),

[0073] Formula (5) can be obtained through Laplace transform:

[0074] (5),

[0075] The output voltages of the first / second motors 63 / 64 can be obtained from formulas (1)-(5). With output speed The two-way linear differential equations are shown in formula (6):

[0076] (6),

[0077] In the formula, This represents the total moment of inertia.

[0078] The transfer function between the first / second motors 63 / 64 and the load platform (i.e., the entire system of this invention) is obtained through Laplace transform. For formula (7):

[0079] (7),

[0080] Reference Figure 5 As shown, this embodiment of the invention is based on fractional-order PID controller adjustment. The desired and measured values ​​of the suspension system are substituted into the fractional-order PID controller to obtain the corresponding correction values, which control the rotation of the first motor 63 and the second motor 64. Specifically, as follows:

[0081] First difference: Expected roll angle Compared with the actual roll angle measurement value The difference is used as the input variable for the roll axis. Second difference: expected pitch angle Compared with the actual pitch angle measurement value The difference is used as the input variable for the rotation axis of the pitch frame 62. See formulas (8) and (9) for details:

[0082] (8),

[0083] (9),

[0084] The specific adjustment process of a fractional-order PID controller is as follows:

[0085] By inputting the transfer function of the roll axis 61 and the transfer function of the pitch frame 62 of the suspension system into the transfer function model built in Simulink (Equation (7)), the six parameters of the fractional-order controller of the roll axis 61 are obtained. , , , , , The six parameters of the 62-axis fractional-order controller for the pitch frame , , , , , .

[0086] Input the roll axis 61 as a variable. And pitch frame 62-axis input variables The values ​​are respectively input into the corresponding roll axis 61 fractional-order controller (formula (10)) and pitch frame 62 rotation axis fractional-order controller (formula (11)):

[0087] (10)

[0088] (11),

[0089] Obtain the correction value for the roll angle. Correction values ​​for pitch angle .

[0090] Based on the obtained roll angle correction value Correction values ​​for pitch angle The rotation angles of the first motor and the second motor are controlled respectively to adjust the rotation angle of the pitch axis and adjust the attitude of the receiving coil.

[0091] in: It is the first difference. It is the second difference. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the roll axis 61. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the 62-axis rotation of the pitch frame.

[0092] It should be noted that the fractional-order PID controller adds an integral order to the integer-order PID controller. and differential order , and It can be any real number between [0, 2], adjusted within a suitable range. and The value can reduce system overshoot, decrease the number of oscillations, shorten the settling time, speed up the response, and improve steady-state accuracy.

[0093] Reference Figure 6 As shown, the effect of using a fractional-order PID controller is significantly better than that of an optimized integer-order PID controller. The overshoot of the integer-order PID controller is about 10%, while the overshoot of the fractional-order PID controller is less than 1%. The settling time of the integer-order PID controller is 0.3s, while the settling time of the fractional-order PID controller is 0.06s.

[0094] Components not described in detail in this application are all existing conventional technologies and will not be described further here.

[0095] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.

Claims

1. A dynamic noise active suppression suspension system based on ground-to-air electromagnetic detection, characterized in that: It includes a receiving coil sensor (5), a coil vibration suppression system (4), and a coil attitude control system (6). The coil attitude control system (6) includes a controller (3), a first motor (63), a second motor (64), and a pitch frame (62). The coil vibration suppression system (4) is connected to the pitch frame (62) through a carbon fiber tube assembly. The pitch frame (62) is connected to the receiving coil sensor (5) through two symmetrical roll axes (61). One side of the roll axis (61) is connected to the first motor (63). The second motor (64) is set on the frame of the pitch frame (62) perpendicular to the roll axis (61). The first motor (63) and the second motor (64) are both connected to the controller (3). The coil vibration suppression system (4) is connected to the UAV (1) through a suspending rope (2). The coil vibration suppression system (4) suppresses the vibration amplitude of the receiving coil (51) and absorbs the motion noise generated by the vibration of the receiving coil (51). The controller (3) collects and controls the first motor (63) and the second motor (64) to adjust the attitude of the receiving coil (51) and suppress the motion noise generated by the attitude change of the receiving coil (51).

2. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 1, characterized in that: The receiving coil sensor (5) includes a receiving coil (51) and a preamplifier (52). The output of the receiving coil (51) is connected to the input of the preamplifier (52), and the output of the preamplifier (52) is connected to the receiver (7).

3. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 2, characterized in that: The receiving coil (51) has four winding channels on its skeleton. The upper two winding channels and the lower two winding channels are respectively wound with silver-plated wire to form an upper winding group and a lower winding group. The silver-plated wire winding paths of the upper winding group and the lower winding group are the same.

4. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 2, characterized in that: The preamplifier (52) includes a signal damping matching circuit, a signal amplification circuit and a voltage follower circuit. The input terminal of the signal damping matching circuit is connected to the upper and lower winding groups of the receiving coil (51) respectively. The output terminal of the signal damping matching circuit is connected to the input terminal of the signal amplification circuit. The output terminal of the signal amplification circuit is connected to the input terminal of the voltage follower circuit. The output terminal of the voltage follower circuit is connected to the receiver (7).

5. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 1, characterized in that: The coil vibration suppression system (4) includes a connecting frame and four sets of shock-absorbing components set at the four corners of the connecting frame. Each set of shock-absorbing components includes a base (43), a shock-absorbing column (42), and a hanging ring (41). The bottom of the shock-absorbing column (42) is provided with a base (43), which is connected to the connecting frame through the base (43). The top of the shock-absorbing column (42) is connected to the hanging ring (41). The four sets of hanging rings (41) are connected by a hanging rope (2) and suspended below the drone (1), so that the hanging ring (41) and the hanging rope (2) form a four-sided pyramid structure.

6. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 1, characterized in that: Two roll shafts (61) are symmetrically connected at one end to the receiving coil (51), and the other end of one roll shaft (61) is connected to the pitch frame (62). The other end of the roll shaft (61) passes through the pitch frame (62) and is connected to the output shaft of the first motor (63). The roll angle of the receiving coil (51) is controlled by the first motor (63). The pitch angle of the pitch frame (62) and the receiving coil (51) is controlled by the second motor (64) connected to the pitch frame (62).

7. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 1, characterized in that: The controller (3) includes a microcontroller chip, a keyboard, a display screen, a GPS clock synchronization module, an IMU module, and an SD card module. The IMU module is used to detect the roll angle and pitch angle of the receiving coil (51). The microcontroller chip is connected to the display screen, keyboard, IMU module, SD card module, first motor (63), and second motor (64). The controller parameters are set through the display screen and keyboard. The microcontroller chip collects the roll angle and pitch angle of the receiving coil (51) through the IMU module and writes them into the SD card module. The microcontroller chip calculates the angle correction value and controls the first motor (63) and second motor (64) to rotate the corresponding angle.

8. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 7, characterized in that: The IMU module is set on the receiving coil (51). Based on the roll angle of the receiving coil (51) and the pitch angle correction value of the pitch frame (62) obtained by the attitude information collected by the IMU module, the rotation angle of the first motor (63) and the second motor (64) is controlled. The attitude information includes the roll angle and the pitch angle.

9. The dynamic noise active suppression suspension system for the ground-to-air electromagnetic detection method according to claim 1, characterized in that: The control method of the coil attitude control system (6) includes: Obtain the roll angle and pitch angle parameters of the receiving coil (51); Based on the roll angle parameters and pitch angle parameters, determine the first difference of roll angle and the second difference of pitch angle. The first difference is the difference between the actual value and the expected value of roll angle, and the second difference is the difference between the actual value and the expected value of pitch angle. The roll angle correction value is determined by the fractional-order PID controller based on the first difference, and the pitch angle correction value is determined based on the second difference; the rotation angle of the first motor (63) and the second motor (64) is controlled to adjust the attitude of the receiving coil (51).

10. The system according to claim 9, characterized in that: Determination of the correction values ​​for the roll angle and pitch angle: Substituting the first difference and the second difference into the fractional-order PID controller, respectively, yields the correction value for the roll angle. and the correction value of the pitch angle ; ， In the formula, It is the first difference. It is the second difference. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the roll axis. , , , , , The proportional coefficient, integral coefficient, differential coefficient, integral order, differential order, and differential operator represent the pitch frame rotation axis.

Images