CN116839780A - Weak electromagnetic force measuring device and method for wireless power transmission coupler - Google Patents
Weak electromagnetic force measuring device and method for wireless power transmission coupler Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
- G01R33/1253—Measuring galvano-magnetic properties
Abstract
The invention discloses a weak electromagnetic force measuring device and a weak electromagnetic force measuring method of a wireless power transmission coupler, wherein the device comprises a mechanical sensor, a supporting and adjusting structure, a gravity compensator and a data acquisition and processing system, wherein the mechanical sensor is used for measuring weak force generated in the wireless power transmission process; the supporting and adjusting structure is used for supporting and adjusting the installation positions of the coupler transmitting coil, the coupler receiving coil, the magnetic core and the metal shielding plate; the gravity compensator counteracts the gravity of the coupler through the mass block; the data acquisition and processing system is used for amplifying and filtering the output signal of the mechanical sensor, extracting the steady-state acting force, and calculating the magnitude and the direction of the steady-state acting force to obtain the weak electromagnetic force generated in the wireless power transmission process. According to the invention, under the alternating-current high-frequency electromagnetic environment, the measuring range and the precision are considered, the continuous detection of the suction force and the repulsive force between the couplers is realized, and the accuracy of electromagnetic force measurement is improved.
Description
Technical Field
The invention belongs to the technical field of wireless power transmission, and relates to a weak electromagnetic force measuring device and method of a wireless power transmission coupler.
Background
Electromagnetic force measurement in alternating high frequency electromagnetic environments presents a number of challenges that make it difficult for existing mechanical measurement devices to accurately measure electromagnetic forces in such environments. Especially, the measurement of weak electromagnetic force is still blank in the wireless power transmission process; in carrying out the invention, the inventors have found that there are at least the following problems in the prior art:
1. in a complex alternating high-frequency electromagnetic environment, the wavelength of electromagnetic waves is very short, and the signal propagation speed is very high. This makes the electromagnetic field change very rapidly in space and time, and it is difficult for existing mechanical measuring devices to capture the change in electromagnetic force in real time in such environments.
2. No adaptation is made to the wireless power transfer coupler; the existing force measuring device cannot directly carry out mechanical measurement on the wireless power transmission coupler due to the requirements of the wireless power transmission coupler such as size, assembly and fixation, and a brand new architecture is required to be designed.
3. The measuring range and the resolution of the existing force measuring equipment are not matched; the sensitivity and resolution of existing mechanical measuring devices may not be sufficient to accurately measure electromagnetic forces in high frequency electromagnetic environments. First, the indexes of different load cells are different, and some of the load cells have large measurement ranges, but low resolution, and some of the load cells have high resolution, but small measurement ranges. The selection of the load cell should be targeted. Secondly, the electromagnetic force generated in the wireless power transmission process is very weak, and the general mechanical magnitude is 10 -1 N to 10 - 4 N, however, the coupler for wireless power transmission is heavy, typically about 5kg to 10 kg. Therefore, it is difficult to simultaneously achieve the resolution required for electromagnetic force measurement while requiring the measurement range of the force measuring device to satisfy the measurement range of the coupler weight.
In summary, the weak force measurement device and the related state of the art on the market have already advanced to a certain extent, but no device is available for measuring weak electromagnetic force in the wireless power transmission process, especially in the complex alternating high-frequency electromagnetic field environment.
Disclosure of Invention
In order to solve the problems, the invention provides a weak electromagnetic force measuring device of a wireless power transmission coupler, which combines measuring range and precision in an alternating-current high-frequency electromagnetic environment, realizes continuous detection of suction force and repulsive force between the couplers, improves the accuracy of electromagnetic force measurement and solves the problems in the prior art.
Another object of the present invention is to provide a measurement method of a weak electromagnetic force measurement device of a wireless power transmission coupler.
The technical scheme adopted by the invention is that the weak electromagnetic force measuring device of the wireless power transmission coupler comprises:
the mechanical sensor is arranged below the coupler receiving coil and is used for measuring weak force generated in the wireless power transmission process;
the supporting and adjusting structure is used for supporting and adjusting the installation positions of the coupler transmitting coil, the coupler receiving coil, the magnetic core and the metal shielding plate; the distance or the relative position between the sensor and the measured sample is adjusted, so that the sensor can accurately measure weak force;
the gravity compensator counteracts the gravity of the coupler through the mass block;
the data acquisition and processing system is used for amplifying and filtering the output signal of the mechanical sensor, carrying out Fourier transform on the filtered signal, converting the time domain signal into the frequency domain signal, extracting the steady-state acting force, carrying out smoothing treatment on the extracted steady-state acting force, and calculating the magnitude and direction of the steady-state acting force, thus obtaining the weak electromagnetic force generated in the wireless power transmission process.
Further, the weak electromagnetic force has a magnitude of 10 -1 N～10 -4 N。
Further, the mechanical sensor is a miniature tension pressure sensor, a miniature force sensor,Annular hollow force sensor or cantilever type weighing force sensor, resolution 10 -4 N。
Further, the system also comprises a display and control interface for displaying the measurement data in real time and controlling the measurement process through a computer software interface or a hardware control panel.
Further, the supporting and adjusting structure comprises a base, and the base can drive the coupler transmitting coil and the coupler receiving coil to independently move in a three-dimensional plane.
Further, the mass block of the gravity compensator is arranged above the sensor and is positioned on the mounting platform of the coupler.
A measuring method of a weak electromagnetic force measuring device of a wireless power transmission coupler comprises the following steps:
s1, setting a filtering grade, setting zero voltage and setting gravity compensation;
s2, acquiring acquisition data through a mechanical sensor;
s3, carrying out undistorted amplification on the voltage at the output end of the force transducer through a signal amplifier, and carrying out filtering treatment on the measured signal through a digital filtering and spike removing method to remove high-frequency noise and low-frequency interference;
s4, continuously sampling the filtered data in a period of time, calculating vibration amplitude, and if the vibration amplitude meets a set value, namely, is a steady-state force, performing data smoothing processing in the next step; resetting the filtering level if the amplitude variation exceeds the set amplitude variation tolerance times, namely the data is unstable;
s5, smoothing the data to remove high-frequency noise or burst interference;
s6, judging the difference value between the current voltage and the zero voltage, and if the difference value is larger than zero, marking the input voltage as positive; if the difference is less than zero, the input voltage flag is negative; thereby determining whether the current coupler is stressed by suction force or repulsive force;
s7, calculating the stressed value of the current coupler through a function obtained by linear calibration of the voltage and the electromagnetic force gain.
Further, the method also comprises the following steps:
performing Fourier transform on the filtered signals, and converting the time domain signals into frequency domain signals so as to more clearly observe the intensity of each frequency component, thereby separating out the frequency components of the steady acting force;
and finding out a frequency component corresponding to the steady acting force in the frequency domain signal, and converting the frequency component into a time domain signal through inverse Fourier transform, wherein the obtained signal is the steady acting force.
Further, zero voltage calibration is performed prior to each measurement.
Further, the electromagnetic force gain linear calibration method comprises the following steps: fitting the nonlinear stress relation through a spline function to obtain a function of a sensor voltage value and an electromagnetic force value between couplers:
S i (x)＝a i +b i (x-x i )+c i (x-x i ) 2 +d i (x-x i ) 3 ,i＝0,1…n-1
wherein S is i (x) Representing the output voltage value of the sensor corresponding to the electromagnetic force x currently measured, x i An electromagnetic force value, a, representing an ith voltage gain calibration input i ，b i ，c i ，d i For coefficients to be solved, n represents the number of the number values involved in the fitting.
The beneficial effects of the invention are as follows:
1. the invention analyzes the measurement result of the weak electromagnetic force of the wireless power transmission coupler in the alternating-current high-frequency electromagnetic environment and provides the needed data for scientific researchers.
2. The invention can simulate the suspension state of the coupler in the microgravity environment by utilizing the gravity compensation technology, and can improve the resolution of the force transducer.
3. The invention aims at a data processing method for extracting effective electromagnetic force under a complex alternating electromagnetic field environment, combines a gravity compensation method with high measurement precision and sensitivity, can obtain a continuous curve of electromagnetic force changing along with current, measures continuous electromagnetic force values, and realizes the detection of electromagnetic force between couplers through dynamic balance of voltage.
4. The receiving and transmitting ends of the coupler can independently move in a 3-dimensional plane, and an open mechanism verification platform is provided for the position sensitive parameters of the large magnetic coupler.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of the overall structure of an embodiment of the present invention.
Fig. 2 is a detailed view of the structure of an embodiment of the present invention.
FIG. 3 is a block diagram of a support and adjustment structure according to an embodiment of the present invention.
FIG. 4 is a flow chart of a gravity compensation calibration setup in an embodiment of the invention.
FIG. 5 is a graph of a gravity compensation fit in an embodiment of the invention.
FIG. 6 is a flow chart of a force measuring method according to an embodiment of the invention.
Fig. 7 is a graph of electromagnetic force applied to a coupler calculated according to an embodiment of the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The existing wireless power transmission technology mainly aims at the application scene of the ground, the environment is affected by the earth gravity, electromagnetic force received between the receiving and transmitting coils during wireless power transmission is not easy to appear (generally offset by the ground friction force), so that the problem of the electromagnetic force is not the problem to be solved conventionally, and the problem is not emphasized. In the field of aerospace, electromagnetic force generated in a weightless environment can enable the position of a receiving and transmitting coil to gradually deviate from the central position, so that the function of the device is disabled. Therefore, in aerospace applications, the problem of electromagnetic forces between transmit and receive coils cannot be ignored.
Examples
A weak electromagnetic force measuring device of a wireless power transmission coupler is shown in fig. 1-2, and comprises a supporting and adjusting structure, a mechanical sensor and a data acquisition and processing system.
As shown in fig. 3, the support and adjustment structure is responsible for supporting the sensor, coupler, etc., and minimizing the impact of environmental factors (e.g., vibration, thermal expansion) on the measurement results. The support structure should have good stability and rigidity. The sensor is provided with an adjusting mechanism for adjusting the distance or the relative position between the sensor and an object to be measured (a wireless power transmission coupler) so as to ensure that the sensor can accurately measure weak force. By utilizing the gravity compensation technology, the measuring range of the force transducer is greatly reduced, and the resolution of the force transducer is effectively improved. The gravity compensation method is carried out by adopting a multi-axis mass block counter weight counteracting method. In mechanical systems (e.g., balance, robotic arm, lift platform, etc.), the addition of multi-axis masses counteracts or balances the gravitational force on the wireless power transfer coupler, thereby enabling simultaneous gravitational force compensation in multiple directions. The design can improve the applicability of the system, so that the system can cope with the gravity influence of different objects to be detected, thereby greatly reducing the measuring range of the force sensor and greatly improving the resolution of the force sensor.
The selection and installation of the mass blocks are determined according to parameters, gravity direction, installation position and other factors of an actual system. The mass, shape and mounting position of the mass block need to be precisely calculated and adjusted for optimal balancing. In practical application, the material of the mass block is usually metal material such as iron, steel, copper and the like, and has higher density and good mechanical property.
The mass of the mass is determined by the weight of the wireless power transfer coupler, and is adjustable to accommodate different couplers. In a manner similar to a "balance" the weight of the coupler is counteracted as much as possible, for example if the total amount of coupler is 5kg, the range of the load cell is required to be at least greater than 50N, (here an approximation of 9.8N/kg). The gravity compensator is arranged above the sensor and is positioned on a mounting platform of the coupler, the gravity of the coupler is counteracted as much as possible in a similar way of a balance scale, and the gravity compensator is combined with calibration, so that the acting force of the coupler on the load cell is reduced as much as possible.
The mechanical sensor is responsible for measuring weak forces. Electromagnetic force generated in the wireless power transmission process is very weak, and the general mechanical magnitude is 10 -1 N to 10 -4 About N, the embodiment of the invention adopts micro tension pressure sensor, micro force sensor, annular hollow force sensor, cantilever type weighing force sensor and other precision sensors (measuring range 1N, resolution 10) -4 N). It is noted that the range and resolution of the load cell are in a relationship that is constrained by each other, i.e., the greater the range, the lower the resolution and vice versa. The coupler coil is arranged above the force transducer, the measuring range of the force transducer is larger than the gravity of the coupler coil, so that the force transducer can work stably, but the resolution of the force transducer is limited. The type of the load cell is targeted. The electromagnetic force measuring range and resolution of the embodiment of the invention are provided based on the actual situation of wireless power transmission, and are the model selection of the force sensor which is specially performed aiming at the electromagnetic force measuring range and resolution generated in the wireless power transmission process. The measurement range and resolution of the existing force measuring device do not particularly precisely indicate the standard, so that the sensitivity and resolution of the existing mechanical measuring device may not be sufficient to precisely measure the electromagnetic force in the high-frequency electromagnetic environment.
The receiving and transmitting end of the coupler can independently move in 3 dimensions (up and down, left and right, front and back); the base can be displaced back and forth, left and right, and the stand can be adjusted up and down, as shown in fig. 3. The spiral guide rod is in threaded connection with the rotating knob, the spiral guide rod is in sliding connection with the bracket along the axial direction, and the outer wall of the spiral guide rod is fixedly connected with the platform; when the knob is turned, the screw guide rod is driven to axially move by the rotation of the screw thread, and in the process, the platform moves axially along the guide rod on the screw line, and the guide rod is actually extended or shortened in the axial direction. The axial movement distance of the coupler coil is equal to the pitch of the spiral line when the knob rotates once. Therefore, through rotating the knob, the axial movement distance of the platform and the length of the guide rod can be accurately controlled, and the platform is driven to move left and right, front and back and up and down.
The data acquisition and processing system is responsible for converting the output signals of the sensors into readable data and processing and analyzing the data through a correlation algorithm. This part includes a signal amplifier, an analog to digital converter (ADC), a microprocessor or computer, etc.
Due to the complex alternating high frequency electromagnetic environment characteristics. The wireless power transmission comprises a transmitting coil and a receiving coil, wherein alternating current on the transmitting coil generates a high-frequency alternating electromagnetic field, and induction current on the receiving coil simultaneously generates the high-frequency alternating electromagnetic field. In this scenario, two parts of force are generated, the first part being a periodic force that varies over time, and the second part being a steady-state force in one direction. These two forces react to overlapping forces in space and time, requiring efficient data acquisition and processing for a particular scene. The embodiment of the invention provides a data processing method, which separates two parts of force in measurement, and the periodic acting force is a force which can be counteracted in one period, but the steady-state force cannot be counteracted, so that the method is an electromagnetic force focused by people.
The data processing method specifically comprises the following steps:
1. signal amplification: the device is used for measuring weak force in the working of the wireless power coupler, and because the force applied to the force sensor is very small, the voltage change generated by the bridge in the sensor is very small, which is in the order of mV or even in the order of mu V, and an amplifying circuit is designed for carrying out undistorted amplification on the voltage at the output end of the force sensor in order to ensure the accuracy of data measurement. And carrying out analog-to-digital conversion on the amplified analog signals through an analog-to-digital converter.
2. And (3) signal filtering: the digital filtering technology and the spike removing technology are adopted to eliminate the filtering processing of the measured signals and remove the high-frequency noise and the low-frequency interference. The higher the level of digital filtering, the more interference and noise can be eliminated, but at the same time the delay and complexity of the filter will be increased, the filtering level will be selected according to the specific application and signal characteristics.
3. Fourier transform: and carrying out Fourier transform on the filtered signals, and converting the time domain signals into frequency domain signals. In this way, the intensity of each frequency component can be more clearly observed, and thus the frequency components of the steady-state force can be separated.
4. Extracting steady-state acting force: in the frequency domain signal, the frequency component corresponding to the steady-state force is found and then converted back into the time domain signal by an inverse fourier transform. The signal thus obtained is the steady-state force.
5. Smoothing: the extracted steady-state acting force is smoothed, and the sampled data may contain high-frequency noise or burst interference. When smoothing the high-frequency sampling data, an appropriate average number needs to be selected to balance the relation between the smoothing effect and the data response speed. The sampling frequency is higher, the data change is faster, and the device sets 4 groups of average numbers so as to maintain the data response speed.
6. Data analysis: the extracted steady-state acting force is subjected to data analysis, and the characteristic parameters such as the size, the direction and the like of the steady-state acting force are calculated so that subsequent application, such as liquid crystal display, can be used as parameters set to zero points.
In summary, the steady-state acting force applied to the metal object is measured in the high-frequency electromagnetic field environment, and the steps of filtering, fourier transformation, frequency domain analysis, inverse fourier transformation, smoothing and the like are required to be performed on the original signal, so that the steady-state acting force is separated and extracted.
And the display and control interface is used for displaying the measurement data in real time and providing a function of controlling the measurement process. This part may be a computer software interface or a hardware control panel.
The coupler is arranged on the measuring device, so that the coupler can move left and right, front and back, up and down, and electromagnetic force measurement can be performed on the coupler under the position movement. The coupler consists of a coil, a magnetic core and a metal shielding plate, and the coil, the magnetic core and the metal shielding plate are required to be fixed on the measuring device. And supports its up-down, left-right adjustment position. Meanwhile, a cabin body for placing the transmitting circuit module and the receiving circuit module of the wireless power transmission is supported. Secondly, the measuring device can simulate a microgravity environment, and mainly utilizes a gravity compensation technology to offset the gravity influence of the coupler.
The measuring process comprises static measurement and dynamic measurement, wherein the static measurement automatically tracks the change of the quality, and gravity compensation calibration setting is carried out. The dynamic measurement has digital filtering processing, is suitable for the measurement of variable micro electromagnetic force, and the vibration tolerance of force can be set by a keyboard. In order to realize the ideal micro electromagnetic force test, the device adopts a gravity compensation calibration method, and simultaneously carries out zero point calibration and voltage gain linear calibration before each measurement.
And carrying out gravity compensation calibration, reducing stress of the sensor, and then carrying out zero point calibration.
Zero point calibration:
the force between the wireless power transmission couplers comprises attractive force and repulsive force, and the attractive force and the repulsive force are different in direction, so that zero point voltage needs to be determined to be used as a calculation reference of repulsive force and attractive force states.
Non-linear error fit (i.e., linear calibration of voltage gain) based on spline functions:
in order to meet the high accuracy requirement of micro electromagnetic force measurement, spline functions are applied to the stress relation to perform fitting, and the functions of measuring gravity compensation and reducing errors are achieved. Taking a measuring device for measuring hundred milli-newtons as an example, at most 9 gain points can be input for linear calibration, and in actual operation, the number of calibration points can be freely selected, and at least 1 gain point can be calibrated to work normally. As shown in fig. 4, the gain compensation process using spline functions: sequentially adding 500mg, 1g, 1.5g, 3g, 3.5g, 4g, 5g, 10g and 20g on a dynamometer platform, converting gravity change into an electric signal through a gravity sensor, finally converting the electric signal into a gravity value by a rear-end data acquisition and processing module, displaying the gravity value, and inputting the gravity value according to a keyboard. Finally obtaining 9 groups of gain point sample data, and obtaining a fitted curve value by solving a cubic spline function equation; after the linear calibration of the voltage gain is performed, the measurement result of the force measuring platform without the linear calibration of the voltage gain is compared with the measurement result of the force measuring platform without the linear calibration of the voltage gain, see fig. 5, wherein the gravity value refers to the gravity of the part of the coupler connected to the force measuring sensor, the test quality is a weight, and a standard gravity value is provided for testing the accuracy of the force measuring sensor. From fig. 5, it can be derived that the data after gravity compensation is more accurate than that without gravity compensation. The purpose of the voltage gain linear calibration is to obtain a more accurate voltage gain function, namely a function of the voltage value of the sensor and the electromagnetic force value between the couplers, wherein the larger the voltage value of the sensor is, the larger the electromagnetic force between the couplers is. In the embodiment, the function relation between the voltage value of each section of sensor and the electromagnetic force value between the couplers is as follows:
S i (x)＝a i +b i (x-x i )+c i (x-x i ) 2 +d i (x-x i ) 3 ,i＝0,1…n-1
wherein S is i (x) Representing the output voltage value of the sensor corresponding to the currently measured stress value (electromagnetic force) x i Representing the stress value of the ith voltage gain calibration input, a i ，b i ，c i ，d i For coefficients to be solved, n represents the number of the number values involved in the fitting.
The n values form n-1 function intervals, and the following expression is established:
S 0 (x) Representing the stress value x at x 0 ≤x≤x 1 And in the interval, the sensor outputs a functional expression of voltage relative to the stress value x. S is S 1 (x) Representing the stress value x at x 1 ≤x≤x 2 And in the interval, the sensor outputs a functional expression of voltage relative to the stress value x. S is S n-1 (x) Representing the stress value x at x n-1 ≤x≤x n And in the interval, the sensor outputs a functional expression of voltage relative to the stress value x.
From the cubic function S of each segment i (x) All contain 4 unknown coefficients, n in this design being in the range of 1,9]The total band solution unknowns in the function is 4 n. According to the boundary condition of each section of function, each section of function passes through the nodes of the function, the 0-order continuity of the connection of all the nodes, namely the function value of one section of equation at the node is equal to the function value of the next section of equation at the same node, the first-order second-order continuity of all the nodes is realized, and the coefficients a, b, c and d of each section of equation are obtained in the program by combining 4n sections of equations.
The collected signals are output to the final result, and the measurement method, as shown in fig. 6, comprises the following steps:
s1, setting a filtering grade, setting zero voltage and setting gravity compensation;
in order to weaken the influence of acceleration caused by fluctuation of force caused by external wire traction and fluctuation of micro electromagnetic force on the whole stress, besides adding a following balance mechanism on a mechanical bearing part, additional alternating pulse is generated for the sensor output signal aiming at the traction of the wire, filtering processing is needed to be carried out on detected data in order to acquire stable output signal components of the force detection sensor, and a keyboard can be used for setting a filtering grade in an initialization part so as to acquire stable signals.
S2, acquiring acquisition data through a mechanical sensor;
s3, carrying out undistorted amplification on the voltage at the output end of the force transducer through a signal amplifier, and carrying out filtering treatment on the measured signal through a digital filtering and spike removing method to remove high-frequency noise and low-frequency interference;
performing Fourier transform on the filtered signals, and converting the time domain signals into frequency domain signals so as to more clearly observe the intensity of each frequency component, thereby separating out the frequency components of the steady acting force;
and finding out a frequency component corresponding to the steady acting force in the frequency domain signal, and converting the frequency component into a time domain signal through inverse Fourier transform, wherein the obtained signal is the steady acting force.
S4, continuously sampling the filtered data in a period of time, calculating vibration amplitude, and if the vibration amplitude meets a set value, namely, is a steady-state force, performing data smoothing processing in the next step; if the amplitude change exceeds the set amplitude change tolerance number, i.e. the data is unstable, the filter level is reset and a prompt is presented on the display for an optimal fluctuation tolerance setting.
S5, smoothing the data to remove high-frequency noise or burst interference;
s6, after the data smoothing process, calculating the current voltage, judging the difference value between the current voltage and the zero voltage, and if the difference value is larger than zero, marking the input voltage as positive; if the difference is less than zero, the input voltage flag is negative; the voltage is positive, the tensile force between the couplers is indicated as suction force, and the numerical value is in direct proportion to the tensile force received by the sensor; the voltage is negative, indicating that the pressure is applied, i.e. repulsive force.
S7, calculating the stressed value of the current coupler through a function obtained by linear calibration of the voltage and the electromagnetic force gain; the magnitude of the value is in negative ratio with the pressure to which the sensor is subjected, and the force is calculated according to a voltage gain function.
The input power is tested, the working current and the voltage of the coupler are shown in table 1, the processed data are calculated by a function obtained by linear calibration of the voltage gain to obtain the value of the current coupler stress, and the value is shown in fig. 7, namely the data of the coupler force recorded every 1 minute by observing the force measuring platform in the actual test process. When the wireless power transmission magnetic resonance coupling is carried out, the transmitted electromagnetic field is in a stable state, and the electromagnetic force between the two couplers is the stable force and tends to be stable along with time.
Table 1 input parameters
| Input electricityPressing | Input current | Power of |
| 220V | 4.5A | 990W |
To realize continuous monitoring, a high-precision detection system is required, and weak changes in the system can be captured in real time; according to the embodiment of the invention, the signals are amplified and filtered through hardware, the filtering grade is set through software, the interference is filtered out through smoothing processing and the like on the data, the precision is improved, and the detection accuracy is further improved. Setting a sampling frequency and a data output period according to the working frequency of the coupler, and distinguishing the sensor output voltage change caused by the electromagnetic force change between the couplers and the sensor output voltage change caused by the high-frequency component in the circuit in the electromagnetic force change range in the process of stabilizing the electromagnetic force between the couplers. The voltage measurements at each time point are processed and interpreted to obtain corresponding electromagnetic force measurements. Furthermore, continuous monitoring requires the ability to quickly respond and process data from the sensor, which requires real-time performance and high-speed data acquisition and processing techniques (real-time of the acquired data and the currently displayed data) to ensure accuracy and timeliness of the data.
The embodiment of the invention can realize continuous detection of suction force and repulsive force between couplers, improve the precision and accuracy of related equipment, and can perform plane coupler electromagnetic force research of milli-newton (mN) level and smaller electromagnetic force. Compared with the traditional mechanical test or single-point measurement, the embodiment of the invention can realize high precision, high sensitivity and high resolution based on dynamic balance of voltage.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.
Claims (10)
1. A weak electromagnetic force measuring device of a wireless power transmission coupler, comprising:
the mechanical sensor is arranged below the coupler receiving coil and is used for measuring weak force generated in the wireless power transmission process;
the supporting and adjusting structure is used for supporting and adjusting the installation positions of the coupler transmitting coil, the coupler receiving coil, the magnetic core and the metal shielding plate; the distance or the relative position between the sensor and the measured sample is adjusted, so that the sensor can accurately measure weak force;
the gravity compensator counteracts the gravity of the coupler through the mass block;
the data acquisition and processing system is used for amplifying and filtering the output signal of the mechanical sensor, carrying out Fourier transform on the filtered signal, converting the time domain signal into the frequency domain signal, extracting the steady-state acting force, carrying out smoothing treatment on the extracted steady-state acting force, and calculating the magnitude and direction of the steady-state acting force, thus obtaining the weak electromagnetic force generated in the wireless power transmission process.
2. The weak electromagnetic force measurement apparatus of a wireless power transfer coupler according to claim 1, wherein the magnitude of the weak electromagnetic force is 10 -1 N～10 -4 N。
3. The weak electromagnetic force measurement apparatus of claim 1, wherein the mechanical sensor is a miniature tension pressure sensor, a miniature force sensor, a ring-shaped hollow force sensor or a cantilever-type weighing force sensor, and the resolution is 10 -4 N。
4. The weak electromagnetic force measurement apparatus of claim 1, further comprising a display and control interface for displaying measurement data in real time and controlling the measurement process through a computer software interface or a hardware control panel.
5. The weak electromagnetic force measurement apparatus of claim 1, wherein the support and adjustment structure comprises a base, the base being capable of driving the coupler transmitting coil and the coupler receiving coil to move independently in a three-dimensional plane.
6. The weak electromagnetic force measurement apparatus of a wireless power transfer coupler of claim 1, wherein the mass of the gravity compensator is mounted above the sensor on a mounting platform of the coupler.
7. The method for measuring a weak electromagnetic force of a wireless power transmission coupler according to claim 1, comprising the steps of:
s1, setting a filtering grade, setting zero voltage and setting gravity compensation;
s2, acquiring acquisition data through a mechanical sensor;
s3, carrying out undistorted amplification on the voltage at the output end of the force transducer through a signal amplifier, and carrying out filtering treatment on the measured signal through a digital filtering and spike removing method to remove high-frequency noise and low-frequency interference;
s4, continuously sampling the filtered data in a period of time, calculating vibration amplitude, and if the vibration amplitude meets a set value, namely, is a steady-state force, performing data smoothing processing in the next step; resetting the filtering level if the amplitude variation exceeds the set amplitude variation tolerance times, namely the data is unstable;
s5, smoothing the data to remove high-frequency noise or burst interference;
s6, judging the difference value between the current voltage and the zero voltage, and if the difference value is larger than zero, marking the input voltage as positive; if the difference is less than zero, the input voltage flag is negative; thereby determining whether the current coupler is stressed by suction force or repulsive force;
s7, calculating the stressed value of the current coupler through a function obtained by linear calibration of the voltage and the electromagnetic force gain.
8. The method for measuring a weak electromagnetic force of a wireless power transfer coupler according to claim 7, further comprising the steps of:
performing Fourier transform on the filtered signals, and converting the time domain signals into frequency domain signals so as to more clearly observe the intensity of each frequency component, thereby separating out the frequency components of the steady acting force;
and finding out a frequency component corresponding to the steady acting force in the frequency domain signal, and converting the frequency component into a time domain signal through inverse Fourier transform, wherein the obtained signal is the steady acting force.
9. The method of claim 7, wherein the zero voltage calibration is performed before each measurement.
10. The method for measuring a weak electromagnetic force measuring device of a wireless power transmission coupler according to claim 7, wherein in S7, the electromagnetic force gain is linearly calibrated by: fitting the nonlinear stress relation through a spline function to obtain a function of a sensor voltage value and an electromagnetic force value between couplers:
S i (x)＝a i +b i (x-x i )+c i (x-x i ) 2 +d i (x-x i ) 3 ,i＝0,1…n-1
wherein S is i (x) Representing the output voltage value of the sensor corresponding to the electromagnetic force x currently measured, x i An electromagnetic force value, a, representing an ith voltage gain calibration input i ，b i ，c i ，d i For coefficients to be solved, n represents the number of the number values involved in the fitting.
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