High-precision calibration device and method for accelerometer based on demodulation of rotating mass

Abstract

The present invention discloses a high-precision calibration device and method for an accelerometer based on rotating mass modulation and demodulation. The present invention uses the generated gravitational acceleration as a signal source to calibrate the scale factor of the accelerometer. The mass body is rotated around a certain axis so that the gravitational acceleration is modulated and periodically changed, and then the rotation angle signal is used to demodulate the output signal of the accelerometer to improve the calibration accuracy. The present invention can calibrate the calibration factor of the acceleration under the condition that the input acceleration amplitude is between the pg magnitude and the ng magnitude to meet the test requirements of high detection sensitivity accelerometers at the #imgabs0# level on the ground. The present invention only requires the relative rotation of the accelerometer and the mass body, does not limit how the accelerometer itself moves, and the generated gravitational acceleration amplitude is weak, so it is applicable to occasions with a small range or requirements for in-situ and on-line measurement. The present invention provides an in-situ, on-line, and high-precision acceleration calibration device and method through rotating mass demodulation.

Description

Technical Field

[0001] The present invention relates to a high-precision calibration device and method for an accelerometer, and particularly to a high-precision calibration device and method for an accelerometer based on the demodulation of a rotating mass body. Background Art

[0002] Accelerometers are widely used in multiple motion measurement fields such as inertial navigation, weapon guidance, resource exploration, vibration monitoring of mechanical equipment, and intelligent manufacturing of robots. As a basic component for motion measurement, the technological progress of accelerometers will play an important role in promoting the development of industries such as advanced manufacturing in our country. With the continuous development of the economy and national defense in our country, the demand trend for the research, manufacturing, testing and calibration, and large-scale application of high-detection-sensitivity ( level) accelerometers has become increasingly significant.

[0003] Currently, the methods for generating standardized and reproducible accelerations on the ground for calibration mainly include the centrifuge method, the linear vibration table method, the single pendulum table method, and the gravity field inclination method, etc., which are mainly introduced as follows:

[0004] The centrifuge method uses the centripetal acceleration generated by a precision centrifuge as the input quantity, and is mainly used for calibrating the performance under large accelerations (1g to 100g).

[0005] The linear vibration table method uses the linear vibration acceleration generated by a precision linear vibration table as the input quantity, and the generated acceleration amplitude is generally between 0.1mg and 1g, and can also be used for calibrating the second-order nonlinear coefficient and frequency response characteristics.

[0006] The single pendulum table method uses the component of the gravitational acceleration along the tangent direction of the pendulum when the digital pendulum table swings at a small angle along the vertical plane as the input quantity. Limited by the angular measurement accuracy of about 1 arcsecond of the optical dividing head, the end tooth disk, and the rotary encoder, and the severe deterioration of the pendulum motion nonlinearity as the pendulum angle increases, the acceleration amplitude generated by this method is generally between 0.1μg and 1mg.

[0007] The gravity field inclination method conducts multi-point tilting and even rolling tests on the accelerometer in the gravity field. Similarly limited by the angular measurement accuracy and the amplitude of the earth's gravity field, the acceleration amplitude generated by this method is generally between 0.1μg and 1g.

[0008] It can be seen that for the commonly used calibration methods on the ground currently, the amplitude of the standardized and reproducible acceleration signal generated is not less than 0.1μg. If used on the ground The research and test of high-sensitivity accelerometers cannot fully guarantee that the calibration factor remains unchanged when the input acceleration decreases from 0.1 μg to the ng level. For example, there is a possibility of dead zones, and the scientific nature and accuracy of the calibration method are insufficient. In the aviation field, some people have proposed a scheme to directly calibrate electrostatically suspended accelerometers on the space orbit of satellites by using a mass body to generate gravitational acceleration. The amplitude of the gravitational acceleration generated is generally also between the pg level and the ng level. However, different from the space orbit that is highly isolated from the environment, the accelerometers placed on the ground calibration platform will be interfered by the noise of environmental factors such as temperature, pressure, and vibration. The signal-to-noise ratio of the pg-level to ng-level gravitational acceleration signal generated by the mass body relative to the environmental noise is insufficient, and the relative error of the calibrated scale factor is relatively large. For example, only considering the ground intrinsic vibration caused by celestial body movement, atmospheric and ocean tides, plate movement, etc., according to the low-noise model of the global seismic network, even in the quietest frequency band (~10 mHz), the random power spectrum of the acceleration noise of the ground intrinsic vibration is generally between and . If a complex vibration isolation, constant temperature, and constant pressure environmental factor isolation system is built to match the space orbit environment to adapt to the direct calibration scheme of gravitational acceleration, the design and construction difficulty and cost of the isolation system are very high, and it is difficult to meet the large-scale application requirements. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the present invention proposes a high-precision calibration device and method for accelerometers based on the demodulation of a rotating mass body. The present invention can not only generate gravitational acceleration with an amplitude between the pg level and the ng level for calibration, but also uses demodulation technology to reduce the measurement bandwidth of the gravitational acceleration signal for calibration to suppress the interference of environmental factors such as temperature, pressure, and vibration noise, so as to adapt to the calibration accuracy requirements of high-sensitivity accelerometers on the ground and reduce the design and construction complexity and cost of the environmental isolation system. The specific scheme of the present invention is as follows:

[0010] I. A high-precision calibration device for accelerometers based on the modulation and demodulation of a rotating mass body

[0011] The calibration device includes an accelerometer, a shielding container, a vibration isolation platform, a mass body, a rotating support, a rotating motor, a rotary encoder, and a demodulator;

[0012] The accelerometer is placed on the vibration isolation platform, the shielding container covers the accelerometer and the vibration isolation platform, the rotating motor is placed on one side outside the shielding container, the rotating shaft of the rotating motor is coaxially connected to the bottom of the rotating support, the mass body is fixedly installed at the top of the rotating support, the rotating support is connected to the rotary encoder, the rotary encoder is used to measure the rotation angle of the rotating support, and the accelerometer and the rotary encoder are respectively electrically connected to the demodulator.

[0013] The distance between the accelerometer and the mass body is between millimeters and meters, and the mass of the mass body is between milligrams and tons.

[0014] The mass body is composed of N discrete sub-mass bodies, N≥1. The N sub-mass bodies are respectively fixedly installed on the top of the rotary support. Each sub-mass body satisfies the following conditions: Where M i is the mass of the i-th sub-mass body, and L i is the distance from the centroid of the i-th sub-mass body to the rotation axis of the rotary support, 1≤i≤N, M Sup is the mass of the rotary support, and L Sup is the distance between the centroid of the rotary support and the rotation axis of the rotary support.

[0015] The distance between the sub-mass bodies is between millimeters and meters, and the shapes of the sub-mass bodies include spherical, square and cylindrical.

[0016] The measurement type of the rotary encoder is absolute or incremental, and the principle types of the rotary encoder include capacitive, photoelectric and static magnetic grating types.

[0017] II. A high-precision calibration method for an accelerometer based on rotary mass body modulation and demodulation

[0018] Use the high-precision calibration device for the accelerometer described above; the method includes the following steps:

[0019] 1) Start the rotary motor to make the rotary support and the mass body rotate around the rotation axis of the rotary motor at a preset speed f Rot while using the rotary encoder to measure the angular position signal V angle (t) of the rotary support and send it to the demodulator. The rotation of the rotary support and the mass body generates gravitational acceleration on the accelerometer, and the accelerometer outputs a voltage signal V a (t) and send it to the demodulator;

[0020] 2) In the demodulator, according to the angular position signal V angle (t) of the rotary support and the voltage signal V a (t) output by the accelerometer, after demodulation, obtain the demodulated signal amplitude V Demod,amp and the angular position signal amplitude V θ,amp ;

[0021] 3) According to the mass, structure, rotation speed of the mass body and the rotary support, and the spatial position relationship between the mass body and the accelerometer, use the law of universal gravitation to calculate the gravitational acceleration, and determine the gravitational acceleration amplitude a Mod,amp ;

[0022] 4) According to the demodulated signal amplitude VDemod,amp and the amplitude V of the angular position signal θ,amp as well as the amplitude a of the gravitational acceleration Mod,amp , calculate and obtain the calibration factor of the accelerometer.

[0023] The specific content of the above (2) is as follows:

[0024] In the demodulator, first, after doubling the frequency and synchronizing the phase of the angular position signal V angle (t) of the rotary support, obtain the angular signal V θ (t). Determine the amplitude V of the angular position signal according to the angular signal V θ (t) θ,amp ; Then multiply the angular signal V θ (t) by the voltage signal V a (t) output by the accelerometer to obtain the demodulated signal V Demod (t). Determine the amplitude V of the demodulated signal according to the demodulated signal V Demod (t) Demod,amp .

[0025] The specific content of the above (4) is as follows:

[0026] First, divide the amplitude V of the demodulated signal Demod,amp by the amplitude V of the angular position signal θ,amp to obtain the response amplitude V of the gravitational acceleration a,amp ; Then, divide the response amplitude V of the gravitational acceleration a,amp by the amplitude a of the gravitational acceleration Mod,amp to obtain the calibration factor β of the accelerometer Acc .

[0027] The maximum modulated frequency f of the gravitational acceleration Mod satisfies f Mod = Nf Rot , and the maximum modulated frequency f Mod is less than 10 times the measurement bandwidth f of the accelerometer c .

[0028] The cut-off frequency f of the low-pass filter in the demodulator c,lp is lower than 10 times the maximum modulation frequency f of the gravitational acceleration Mod .

[0029] The beneficial effects of the present invention are:

[0030] The present invention provides an in-situ, on-line, and high-precision acceleration calibration device and method through the demodulation of a rotating mass. First, the present invention only requires the relative spatial positions of the accelerometer and the mass to rotate, and does not need to restrict how the accelerometer itself moves, unlike methods such as the gravitational field inclination method. Moreover, the calibration only superimposes a gravitational acceleration with a magnitude as weak as several pg to several ng on the measurement value of the accelerometer, which is much smaller than its range of at least μg. Therefore, it is applicable to calibration scenarios with a small range or requirements for in-situ measurement in space and on-line measurement in time, such as working aerospace aircraft or deep-sea submersibles. Second, the gravitational acceleration generated by the mass is only related to its mass and spatial position, and the interference of electromagnetic, temperature, and other factors in the environment is low. Coupled with the demodulation scheme, the measurement bandwidth of the acceleration signal for calibration is fully reduced, the interference of noise factors such as air temperature, air pressure, and vibration in the environment is effectively suppressed, the calibration accuracy is significantly improved, and the design and construction complexity and cost of the environmental isolation system are reduced. Brief Description of the Drawings

[0031] Figure 1 Schematic connection diagram of a high-precision calibration device for an accelerometer based on the modulation and demodulation of a rotating mass according to the present invention.

[0032] Figure 2 Schematic flow diagram of the method according to the present invention.

[0033] Figure 3 Schematic diagram of the structure of a mass 4 and a rotating support 5 in Application Example 1.

[0034] Figure 4 For the modulated gravitational accelerations a Mod,x (θ), a Mod,y (θ), and a Mod,z (θ) of the mass 4 and the rotating support 5 on the accelerometer 1 along the three-axis directions and their relationship curves with the rotation angle θ.

[0035] Figure 5 Internal connection schematic diagram of the demodulator 8 in Application Example 2.

[0036] In the figure: accelerometer 1, shielding container 2, vibration isolation platform 3, mass 4, rotating support 5, rotating motor 6, rotary encoder 7, demodulator 8. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with the drawings and embodiments.

[0038] As Figure 1 shown, the device includes an accelerometer 1, a shielding container 2, a vibration isolation platform 3, a mass 4, a rotating support 5, a rotating motor 6, a rotary encoder 7, and a demodulator 8;

[0039] The accelerometer 1 is placed on the vibration isolation platform 3 and remains stationary in the initial state. The shielding container 2 covers the accelerometer 1 and the vibration isolation platform 3. The rotating motor 6 is placed on one side outside the shielding container 2. The rotating shaft of the rotating motor 6 is coaxially connected to the bottom of the rotating support 5. The top of the rotating support 5 is fixedly installed with a mass body 4. The rotating shaft of the rotating motor 6, the rotating support 5, and the mass body 4 are relatively stationary. A rotary encoder 7 is placed on the rotating motor 6. The rotating support 5 is connected to the rotary encoder 7. The rotary encoder 7 is used to measure the rotation angle of the rotating support 5, and thus obtain the rotational speed of the mass body 4. The accelerometer 1 and the rotary encoder 7 are respectively electrically connected to the demodulator 8.

[0040] The accelerometer 1 is an instrument that can measure linear acceleration, including but not limited to a vacuum optical tweezer accelerometer, a MEMS accelerometer, and an electrostatically levitated accelerometer;

[0041] The shielding container 2 is a container that can reduce the interference of air flow, magnetic field or electric field. The materials include but not limited to wood, metal, and glass.

[0042] The types of the vibration isolation platform 3 include active vibration isolation and passive vibration isolation. The vibration isolation platform 3 is used to suppress the interference effect of environmental vibration and the vibration caused by the rotating mass body on the accelerometer 1.

[0043] The distance between the accelerometer 1 and the mass body 4 is between millimeters and meters, and the mass of the mass body 4 is between milligrams and tons; therefore, the amplitude a of the modulated gravitational acceleration signal Mod is between pg and ng.

[0044] The mass body 4 generates a definite gravitational acceleration and provides an input acceleration signal source for the accelerometer 1. The mass body 4 is composed of N relatively stationary and position-separated sub-mass bodies, N≥1. The N sub-mass bodies are respectively fixedly installed on the top of the rotating support 5. Each sub-mass body satisfies the following conditions: where M i is the mass of the i-th sub-mass body, L i is the distance from the centroid of the i-th sub-mass body to the rotating axis of the rotating support 5, 1≤i≤N, M Sup is the mass of the rotating support 5, L Sup is the distance between the centroid of the rotating support 5 and the rotating axis of the rotating support 5, that is, the generated gravitational acceleration modulation signal mainly comes from the rotational motion of the mass body 4 rather than the rotating support 5.

[0045] The distance between the sub-mass bodies is between millimeters and meters, and the shapes of the sub-mass bodies include but not limited to spherical, square, and cylindrical.

[0046] The rotary support 5 is used to fix and support the mass body 4, enabling the mass body 4 to rotate around a fixed axis. The rotary support 5 includes, but is not limited to, a rotary table and an upright rotary frame.

[0047] The rotary motor 6 provides the energy source for the rotary motion of the rotary support 5. The rotary motor includes, but is not limited to, a DC reduction motor, a stepper motor, and a servo motor.

[0048] The rotary encoder 7 outputs the angular position signal of the rotary support 5 in real time, and the range of the angular position signal is 0 - 2π. The measurement type of the rotary encoder 7 is absolute or incremental, and the principle types of the rotary encoder 7 include, but are not limited to, capacitive, photoelectric, and static magnetic grating types. The implementation forms of the demodulator 8 include, but are not limited to, a demodulation chip module, an analog lock-in amplifier instrument, a digital lock-in amplifier instrument, and a host computer demodulation algorithm, etc.

[0049] As Figure 2 shown, the method includes the following steps: adopting an accelerometer calibration device;

[0050] 1) Start the rotary motor 6 to make the rotary support 5 and the mass body 4 rotate around the rotation axis of the rotary motor 6 at a preset speed f Rot While using the rotary encoder 7 to measure the angular position signal V angle (t) of the rotary support 5 and send it to the demodulator 8. The rotation of the rotary support 5 and the mass body 4 generates a gravitational acceleration on the accelerometer 1, and the accelerometer 1 outputs a voltage signal V a (t) and send it to the demodulator 8; the maximum modulated frequency f Mod of the gravitational acceleration satisfies f Mod = Nf Rot , and the maximum modulated frequency f Mod is less than 10 times the measurement bandwidth f c of the accelerometer 1, so that the fluctuation of the modulation frequency will not cause a drastic change in the measured value of the scale factor.

[0051] 2) In the demodulator 8, after demodulating according to the angular position signal V angle (t) of the rotary support 5 and the voltage signal V a (t) output by the accelerometer 1, the demodulated signal amplitude V Demod,amp and the angular position signal amplitude V θ ,amp are obtained;

[0052] 2) Specifically:

[0053] In the demodulator 8, first, after frequency doubling and synchronous phase of the angular position signal V angle (t) of the rotary support 5, the angle signal V θ (t) is obtained. According to the angle signal V θ(t) Determine the amplitude V of the angular position signal θ,amp ; then multiply the angular signal V θ (t) by the voltage signal V a (t) output by the accelerometer 1 to obtain the demodulated signal V Demod (t). Determine the amplitude V of the demodulated signal according to the demodulated signal V Demod (t) Demod,amp . The cut-off frequency f of the low-pass filter in the demodulator 8 c,lp is lower than 10 times the maximum modulation frequency f of the gravitational acceleration Mod .

[0054] 3) According to the masses, structures, rotational speeds of the mass body 4 and the rotating support 5, and the spatial position relationship between the mass body 4 and the accelerometer 1, calculate the modulated gravitational acceleration using the law of universal gravitation, and determine the amplitude a of the modulated gravitational acceleration according to the modulated gravitational acceleration Mod,amp ;

[0055] 4) Calculate and obtain the calibration factor of the accelerometer 1 according to the amplitude V of the demodulated signal Demod,amp , the amplitude V of the angular position signal θ,amp , and the amplitude a of the modulated gravitational acceleration Mod,amp .

[0056] 4) Specifically:

[0057] First, divide the amplitude V of the demodulated signal Demod,amp by the amplitude V of the angular position signal θ,amp to obtain the response amplitude V of the modulated gravitational acceleration a,amp , that is, V a,amp = V Demod,amp / V θ,amp ; then, divide the response amplitude V of the modulated gravitational acceleration a,amp by the amplitude a of the modulated gravitational acceleration Mod,amp to obtain the calibration factor β of the accelerometer 1 Acc , that is, β Acc = V a,amp / a Mod,amp .

[0058] Application Example 1

[0059] The following gives a specific example to illustrate the modulation process of the gravitational acceleration signal in the present invention.

[0060] The accelerometer 1 to be calibrated is a vacuum optical tweezer accelerometer. Use a linear vibration table to measure the response transfer function, and measure the measurement bandwidth f of the accelerometer 1 c = 1.6 kHz.

[0061] The accelerometer 1 is inside a shielding container 2 that can attenuate the interference of air flow, magnetic field, or electric field. The shielding container 2 is placed on a vibration isolation platform 3, which is used to suppress the interference effect of environmental vibration and the vibration caused by the rotating mass body on the accelerometer 1. Figure 3 It is a schematic diagram of a structure of a mass body 4 and a rotating support 5. The rotating support 5 is used to fix and support the mass body 4, enabling the mass body 4 to rotate around a fixed axis. The mass body 4 is composed of 4 relatively stationary but spatially separated sub-mass bodies. Each sub-mass body is a steel ball with a diameter of 265 mm and a mass of M i = 76 kg. The distance from the center of each sub-mass body to the fixed rotation axis at the center of the rotating support 5 is L i = 1 m. Then the total sum of the mass-distance products of the mass body is The mass M of the rotating support 5 Sup = 55 kg. The design and assembly ensure that the distance from its center of mass to the fixed rotation axis is L Sup ≤ 10 mm. Therefore, it satisfies is much larger than M Sup L Sup . The generated gravitational acceleration modulation signal mainly comes from the rotational motion of the mass body 4 rather than the rotating support 5.

[0062] As Figure 3 shown in (a) and (b) of, the fixed rotation axis at the center of the rotating support 5 is placed vertically. The vertically upward direction is defined as the z-axis. The direction from the sensing unit of the accelerometer 1 to the fixed rotation axis is the x-axis. The four sub-mass bodies are numbered 4-1, 4-2, 4-3, and 4-4 in clockwise order when viewed from the top view, and are arranged with a 90-degree separation. The distance between the centers of 4-1 and 4-3, and the distance between the centers of 4-2 and 4-4 are both 2 m. The minimum distance from the center of the sub-mass body to the sensing unit of the accelerometer 1 is 1 m. The centers of 4-1 and 4-3 are on the same horizontal plane LA. LA is above the horizontal plane LB where the sensing unit of the accelerometer 1 is located, with a distance of 0.3 m. The centers of 4-2 and 4-4 are also on the horizontal plane LB.

[0063] The rotating motor 6 provides the energy source for the rotational motion of the rotating support 5. The rotating motor 6 is a worm gear DC reduction motor, which integrates three components: a motor, a reduction gear, and a slewing bearing. The axial dynamic load is 136 kN, the overturning moment is 35.6 kN·m, the output torque is 8 kN·m, and the supported speed range is 0.1 rpm to 10 rpm. Start the rotating motor 6, and make the mass body 4 and the rotating support 5 rotate at a constant speed f Rot = 0.24 rpm. The number of sub-mass bodies N = 4. Therefore, the maximum modulated frequency f of the gravitational acceleration signal Mod = Nf Rot = 16 mHz. The modulation frequency f Mod is much less than the measurement bandwidth fc , fluctuations in the modulation frequency do not cause drastic changes in the measured value of the scale factor.

[0064] According to the law of universal gravitation and Figure 4 parameters such as the structure of the mass body 4 and the rotary support 5 shown, the modulated gravitational acceleration a of the mass body 4 and the rotary support 5 on the accelerometer 1 along the three-axis directions Mod,x (θ), a Mod,y (θ) and a Mod,z (θ) versus the rotation angle θ are shown as Figure 4 shown. The solid line is the x-axis, the dashed line is the y-axis, and the dotted line is the z-axis. It can be seen that the modulation frequencies of the gravitational acceleration along the x-axis and y-axis are both four times the rotation frequency, and the z-axis is twice, and the modulation phases of the x-axis and y-axis differ by 90 degrees. The phase or frequency differences of the three-axis gravitational acceleration signals enable them to be demodulated using the angular rotation signals of the corresponding frequencies and phases respectively, thus realizing the simultaneous calibration of the scale factors in the three-axis directions of the accelerometer 1. Since the demodulation uses a sine wave with the same frequency and phase as the modulation signal, the amplitudes of the modulated gravitational acceleration signals of the x, y, and z axes are calculated according to the following formula:

[0065] where

[0066] According to Figure 4 the data, the amplitudes of the modulated gravitational acceleration signals of the three-axis Fan are calculated to be a Mod,amp,x = 48.0 pg, a Mod,amp,y = 37.6 pg, and a Mod,amp,z = 26.4 pg. Therefore, the modulation amplitude of the gravitational acceleration generated by the rotation of the structure of the mass body 4 and the rotary support 5 is about dozens of pg, which can be used for the scale factor calibration under the condition of the minimum resolvable input acceleration of high-detection-sensitivity accelerometers at the ground level.

[0067] Application Example 2

[0068] A specific example is given below to illustrate the demodulation process of the gravitational acceleration signal in the present invention.

[0069] The rotary encoder 7 outputs the current angular position signal of the rotary support 5 in real time. The rotary encoder 7 is a single-turn absolute magnetic encoder with a resolution of 4096 pulses / revolution. The internal connection schematic diagram of the demodulator 8 is shown as Figure 5As shown, it is composed of a frequency-doubling phase shifter and a digital lock-in amplifier connected in series. The FPGA chip inside the frequency-doubling phase shifter converts the angle signal output by the rotary encoder 7 in the form of an RS485 interface into a cyclic counter value, then adds a phase offset value, inputs it to the sine wave IP core module, and outputs it to the precision digital-to-analog converter to generate analog sine wave voltage signals V θ,i (t), i = x, y, z. V θ,i , i = x, y, z and the three-axis output voltage signals V a,i (t), i = x, y, z of the accelerometer 1 are simultaneously input to the digital lock-in amplifier.

[0070] For each axis, the two types of signals are multiplied and then low-pass filtered to output the signal V Demod,i (t), i = x, y, z. The low-pass filter adopts T avr = 10 5 s long-time averaging method, and the cut-off frequency is much lower than the maximum modulation frequency f Mod = 16 mHz. The measured amplitude of the x-axis output signal of the demodulator 8 is V Demod,amp,x = 3.3006 μV, and the amplitude of the angle signal of the rotary encoder 7 after 4-fold frequency multiplication and a phase lag of 270 degrees is V θ,amp,x = 0.9981 V. The response amplitude of the modulated gravitational acceleration in the output signal of the accelerometer 1 Then, according to the method of the present invention, the calibration factor of the accelerometer 1 is measured as β Acc,x = V a,amp,x / a Mod,amp,x = 6.89×10 4 V / g. The calibration factors of the y-axis and z-axis are not measured, but the process is similar. In addition, by the gravity inclination method, when a gravitational acceleration component with an amplitude of 2 μg is applied to the accelerometer 1 along the x-axis, the measured x-axis scale factor β Acc,x,2 = 6.91×10 4 V / g. Therefore, when the input acceleration of the accelerometer 1 decreases from 2 μg to 48 pg, the change in the calibration factor is only 0.3%, and the dead zone effect can be ignored.

[0071] After passing through a low-pass filter with a cut-off frequency of 0.1 Hz, the standard deviation of the output signal voltage fluctuation of the accelerometer 1 containing environmental noise is 50.4 μV, and the response amplitude V a,amp,x = 3.3072 μV of the modulated gravitational acceleration is included. If demodulation is not applied, the detection signal-to-noise ratio SNR Non-mod = 3.3072 μV / 20.4 μV = -15.8 dB, which is negative and in an undetectable state. After applying demodulation, the standard deviation of the x-axis output signal fluctuation of the demodulator 8 is 1.6 μV, and the amplitude VDemod,amp,x = 3.3006 μV, detection signal-to-noise ratio SNR Non-mod = 3.3006 μV / 0.43 μV = 7.7 dB, meeting the detection requirements, and the demodulation signal-to-noise ratio is improved by 23.5 dB.

[0072] Finally, it should be noted that the above embodiments and descriptions are only used to illustrate the technical solutions of the present invention rather than to limit them. Those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced. Without departing from the spirit and scope of the disclosure of the technical solutions of the present invention, they should all be covered by the protection scope of the claims of the present invention.

Claims

1. A high-precision calibration device for an accelerometer based on rotating mass body modulation and demodulation, characterized in that, It includes an accelerometer (1), a shielding container (2), a vibration isolation platform (3), a mass body (4), a rotary support (5), a rotary motor (6), a rotary encoder (7), and a demodulator (8); The accelerometer (1) is placed on the vibration isolation platform (3), the shielding container (2) covers the accelerometer (1) and the vibration isolation platform (3), the rotary motor (6) is placed on one side outside the shielding container (2), the rotary shaft of the rotary motor (6) is coaxially connected to the bottom of the rotary support (5), the mass body (4) is fixedly installed at the top of the rotary support (5), the rotary support (5) is connected to the rotary encoder (7), the rotary encoder (7) is used to measure the rotation angle of the rotary support (5), and the accelerometer (1) and the rotary encoder (7) are respectively electrically connected to the demodulator (8); The distance between the accelerometer (1) and the mass body (4) is between millimeters and meters, and the mass of the mass body (4) is between milligrams and tons; The mass body (4) is composed of N sub-mass bodies with discrete positions, N≥1, and the N sub-mass bodies are respectively fixedly installed on the top of the rotary support (5), and each sub-mass body satisfies the following conditions: where M i is the mass of the i-th sub-mass body, and L i is the distance from the centroid of the i-th sub-mass body to the rotation axis of the rotary support (5), 1≤i≤N, M sup is the mass of the rotary support (5), and L Sup is the distance between the centroid of the rotary support (5) and the rotation axis of the rotary support (5).

2. The high-precision calibration device for an accelerometer based on rotating mass body modulation and demodulation according to claim 1, wherein The distance between the sub-mass bodies is between millimeters and meters, and the shapes of the sub-mass bodies include spherical, square, and cylindrical.

3. The high-precision calibration device for an accelerometer based on rotating mass body modulation and demodulation according to claim 1, characterized in that, The measurement type of the rotary encoder (7) is absolute or incremental, and the principle types of the rotary encoder (7) include capacitive, photoelectric, and static magnetic grating types.

4. A high-precision calibration method for an accelerometer based on rotating mass modulation and demodulation, characterized in that, It includes the following steps: Using the accelerometer high-precision calibration device according to any one of claims 1-3; 1) Start the rotating motor (6) to rotate the rotating support (5) and the mass body (4) at a preset rotational speed f Rot around the rotation axis of the rotating motor (6). Meanwhile, measure the angular position signal V angle (t) of the rotating support (5) using the rotary encoder (7) and send it to the demodulator (8). The rotation of the rotating support (5) and the mass body (4) generates gravitational acceleration on the accelerometer (1), and the accelerometer (1) outputs a voltage signal V a (t) and sends it to the demodulator (8); 2) After demodulating according to the angular position signal V of the rotary support (5) and the voltage signal V output by the accelerometer (1) in the demodulator (8), the demodulated signal amplitude V angle (t) and the angular position signal amplitude V a (t) are obtained after demodulation; Demod,amp and the angular position signal amplitude V θ,amp ; 3) Calculate the gravitational acceleration using the law of universal gravitation based on the mass, structure, rotational speed of the mass body (4) and the rotating support (5), and the spatial position relationship between the mass body (4) and the accelerometer (1). Determine the gravitational acceleration amplitude a based on the gravitational acceleration. Mod,amp ; 4) According to the demodulated signal amplitude V Demod,amp and the angular position signal amplitude V θ,amp as well as the gravitational acceleration amplitude a Mod,amp , calculate and obtain the calibration factor of the accelerometer (1).

5. A high-precision calibration method for an accelerometer based on rotation mass body modulation and demodulation according to claim 4, characterized in that, Specifically, step 2) is: In the demodulator (8), first, after frequency doubling and synchronous phase adjustment of the angular position signal V angle (t) of the rotary support (5), the angular signal V θ (t) is obtained. Based on the angular signal V θ (t), the amplitude V θ,amp of the angular position signal is determined; then, after multiplying the angular signal V θ (t) by the voltage signal V a (t) output by the accelerometer (1), the demodulation signal V Demod (t) is obtained. Based on the demodulation signal V Demod (t), the amplitude V Demod,amp of the demodulation signal is determined.

6. A high-precision calibration method for an accelerometer based on rotating mass body modulation and demodulation according to claim 4, characterized in that Specifically, step 4) is: First, the demodulated signal amplitude V Demod,amp is divided by the angular position signal amplitude V θ,amp to obtain the response amplitude V of the gravitational acceleration a,amp ; then, the response amplitude V of the gravitational acceleration a,amp is divided by the gravitational acceleration amplitude a Mod,amp to obtain the calibration factor β of the accelerometer (1) Acc .

7. A high-precision calibration method for an accelerometer based on rotating mass body modulation and demodulation according to claim 4, characterized in that, The maximum modulated frequency f of the gravitational acceleration Mod , satisfies f Mod = Nf Rot , the maximum modulated frequency f Mod is less than 10 times the measurement bandwidth f of the accelerometer (1) c .

8. A high-precision calibration method for an accelerometer based on rotating mass body modulation and demodulation according to claim 4, characterized in that, The cut-off frequency f of the low-pass filter in the demodulator (8) c,lp is lower than 10 times the maximum modulation frequency f of the gravitational acceleration Mod .

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