Accelerometer sensitivity calibration method and device

Abstract

The present invention provides a method and device for calibrating accelerometer sensitivity, belonging to the field of precision measurement. The calibration device includes: a shielding cover, a precision angle measuring instrument, a precision displacement adjustment platform, a displacement adjustment mass, a vibration isolation foundation, and a tilt compensation pendulum. The shielding cover is a container that reduces airflow, electromagnetic fields, or temperature interference. The accelerometer to be tested is an instrument for measuring linear acceleration. The combination of the precision displacement adjustment platform and the displacement adjustment mass enables sub-μrad to μrad adjustment of the pitch and roll angles of the tilt compensation pendulum, providing a sub-μg to μg acceleration calibration signal. The precision angle measuring instrument continuously monitors the pitch and roll angle changes of the tilt compensation pendulum. The tilt compensation pendulum isolates ground vibration noise in the 0.001Hz to 1Hz frequency band from being transmitted to the accelerometer to be tested, thereby reducing the impact of ground vibration on accelerometer calibration.

Description

Technical Field

[0001] The present invention belongs to the field of precision measurement, and more specifically, relates to a method and device for calibrating the sensitivity of an accelerometer. Background Art

[0002] High-precision accelerometers have important application significance in fields such as space gravity experiments and satellite gravity measurements. Satellite gravity measurements require high-precision accelerometers to measure the non-conservative forces acting on spacecraft. Accelerometer measurement data is of great significance for gravity field inversion and atmospheric model research, and the uncertainty of its sensitivity coefficient will directly affect the accuracy of gravity field recovery and atmospheric model calculation accuracy. The resolution of accelerometers in satellite gravity measurements must be at least 10 - 10 m / s 2 / Hz 1 / 2 The accuracy requirements for calibrating the sensitivity coefficient of such instruments on the ground are getting higher and higher, because the ground pulsation noise is generally around 10 -7 ~10 -8 m / s 2 / Hz 1 / 2 The magnitude of the sensitivity coefficient calibration is far beyond the test resolution requirements of current and future high-precision accelerometers. It is difficult to meet the requirements by directly calibrating the sensitivity coefficient of high-precision accelerometers on the ground. Therefore, a new sensitivity calibration method must be developed to meet the future design and verification requirements of high-precision accelerometers.

[0003] Currently, there are two main methods for evaluating the sensitivity coefficient of high-precision accelerometers. One method involves testing and calibrating the high-precision accelerometer on a high-precision six-degree-of-freedom displacement adjustment table. The high-precision six-degree-of-freedom displacement adjustment table is located on a marble table in a quiet laboratory. However, due to the limited vibration isolation capability of the marble table against low-frequency ground pulsations, this testing method cannot meet the requirements for high-precision calibration of the sensitivity coefficient of high-precision accelerometers.

[0004] Another method is to place a high-precision accelerometer and a high-precision six-degree-of-freedom displacement adjustment table on the vibration isolation system for testing and calibration. However, due to the working mode of the high-precision six-degree-of-freedom table, its connecting cables will affect the performance of the vibration isolation system and ultimately affect the accuracy of the test and calibration results. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims to provide a method and device for calibrating the sensitivity of an accelerometer, aiming to solve the problem that the existing method of testing and calibrating a high-precision accelerometer by placing it on a high-precision six-degree-of-freedom displacement adjustment table, which is located on a marble table in a quiet laboratory, cannot meet the requirements of high-precision calibration of the sensitivity coefficient of a high-precision accelerometer due to the limited vibration isolation capability of the marble table against low-frequency ground pulsations.

[0006] To achieve the above-mentioned object, on the one hand, the present invention provides an accelerometer sensitivity calibration device, comprising: a shielding cover, a precision angle measuring instrument, a precision displacement adjustment platform, a displacement adjustment mass block, a vibration isolation foundation, and a tilt compensation pendulum platform;

[0007] The accelerometer to be tested, the precision angular velocity measuring instrument, and the precision displacement adjustment platform are mounted on a tilt compensation platform; the displacement adjustment mass block is placed on the precision displacement adjustment platform; the tilt compensation platform and the shielding cover are mounted on a horizontal vibration isolation foundation, with the shielding cover completely covering the tilt compensation platform; the precision angle measuring instrument, the accelerometer to be tested, and the precision displacement adjustment platform all use batteries and wireless communication modules for power supply and communication with external PC-side data monitoring software, respectively.

[0008] The shielding cover is a container for reducing airflow, electromagnetic field or temperature interference; the accelerometer to be measured is an instrument for measuring linear acceleration;

[0009] The combination of a precision displacement adjustment stage and a displacement adjustment mass block achieves sub-μrad to μrad level angle adjustment of the platform pitch and roll angle of the tilt compensation pendulum through sub-mm to sub-m stage travel and g to sub-kg mass, respectively, and is used to provide sub-μg to μg acceleration calibration signals.

[0010] The precision angle measuring instrument is used to continuously monitor the pitch and roll angle data of the tilt compensation platform;

[0011] The tilt compensation platform is used to isolate the ground vibration noise in the frequency band of 0.001Hz to 1Hz from being transmitted to the accelerometer to be tested.

[0012] Further preferably, the accelerometer to be measured is a MEMS accelerometer, a reed accelerometer, and an electrostatic suspension accelerometer.

[0013] Further preferably, the angle measurement resolution of the precision angle measuring instrument reaches nrad / Hz 1 / 2 The horizontal and measuring range is greater than 1000μrad.

[0014] Further preferably, the tilt compensation swing platform includes a platform, a balancing mass block, a rigid connecting rod, a suspension frame and a suspension hinge;

[0015] The two ends of the suspension hinge are respectively fixedly connected to the suspension frame and several rigid links; the other end of the rigid link is fixedly connected to the platform; any two rigid links and the platform are constructed into a triangular shape, and the several rigid links and the suspension hinge are used together to act as a suspension platform and also to attenuate vibrations higher than the natural frequency of the tilt compensation pendulum table and transmit them to the platform; the suspension hinge is used to allow the platform to swing freely in the vertical plane and suppress the torsional motion of the platform in the horizontal plane; the battery and wireless communication module are placed on the platform to reduce the impact of the external cables of the device under test on the vibration isolation performance of the tilt compensation pendulum table.

[0016] In another aspect, the present invention provides a method for calibrating the sensitivity of an accelerometer, comprising the following steps:

[0017] Step 1: Adjust the position and mass of the balancing mass block on the tilt compensation platform to adjust the horizontal control output of the accelerometer to be tested to zero;

[0018] Step 2: After closing the shielding cover, stabilize the tilt compensation platform for a preset time so that the angular noise of the tilt compensation platform falls below the required limit;

[0019] Step 3: Set up a displacement adjustment mass block movement program to generate multiple calibration steps within the range of the accelerometer to be measured;

[0020] Step 4: Monitor and record the pitch and roll angle data θ of the tilt compensation platform, and simultaneously record the horizontal control output data V of the accelerometer to be measured; wherein, the platform's tilt angle data θ is multiplied by the gravity acceleration g to obtain the input calibration signal of the accelerometer;

[0021] Step 5: After calibration, take the tilt compensation platform pitch and roll angle data θ and the accelerometer horizontal control output data V of the middle stable section of each step and perform statistics to obtain the average value and standard deviation of each step;

[0022] Step 6: Perform linear regression fitting analysis on the average value of each step of the tilt compensation platform's inclination data and the average value of each step of the accelerometer's horizontal control output data to obtain a linear relationship between the accelerometer's control output signal and the input calibration signal. The first-order term coefficient in the linear relationship is the sensitivity coefficient of the accelerometer under test, K1 = Δθg / ΔV; where Δθ is the linear regression value of the platform's inclination data; ΔV is the linear regression value of the accelerometer's control output data; and g is the acceleration of gravity.

[0023] Step 7: Perform error analysis on the linear regression fitting process of the tilt compensation platform's inclination data θ and the accelerometer's horizontal control output data V to obtain the standard error ΔK1 of the sensitivity coefficient. Divide it by the sensitivity coefficient to obtain the Class A relative uncertainty of the calibrated sensitivity coefficient.

[0024] Further preferably, in step three, the number of calibration steps and the duration of each step are set according to the measuring range of the accelerometer to be measured.

[0025] In general, the above technical solutions conceived by the present invention have the following advantages compared with the prior art:

[0026] Beneficial effects:

[0027] The present invention provides an accelerometer sensitivity calibration device, wherein the tilt compensation swing table is used to isolate the ground vibration noise in the frequency band of 0.001Hz to 1Hz from being transmitted to the acceleration to be measured, that is, to provide the accelerometer to be measured with a vibration level of ng / Hz in the frequency band of 0.001Hz to 1Hz. 1 / 2 In an environment with a magnitude of 0.1, the impact of ground vibration on accelerometer calibration is reduced.

[0028] The present invention provides an accelerometer sensitivity calibration device, which utilizes the pitch and roll tilt angles of a tilt compensation pendulum to realize the use of the horizontal component of gravity acceleration as the acceleration input in the horizontal sensitive axis direction of the accelerometer. It can provide an acceleration calibration source with an accuracy of sub-μg and a range of μg, meeting the calibration accuracy and range of high-precision accelerometers.

[0029] The present invention provides an accelerometer sensitivity calibration method, which uses a high-precision angle measuring instrument to accurately monitor and record the tilt angle changes of a tilt compensation pendulum. After screening the calibration data, linear regression fitting analysis is used to calibrate the accelerometer sensitivity coefficient and calculate the Class A relative uncertainty. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 1 is a schematic diagram of the front view structure principle of the platform in the accelerometer sensitivity calibration device provided in an embodiment of the present invention;

[0031] Figure 2 1 is a schematic diagram of the top view of the structural principle of the platform in the accelerometer sensitivity calibration device provided by an embodiment of the present invention;

[0032] Among them, 1-shielding cover; 2-precision angle measuring instrument; 3-accelerometer to be measured; 4-precision displacement adjustment platform; 5-displacement adjustment mass block; 6-vibration isolation foundation; 7-tilt compensation pendulum platform; 71-platform; 72-balancing mass block; 73-battery and wireless communication module; 74-rigid connecting rod; 75-suspension frame; 76-suspension hinge;

[0033] Figure 3 This is a flow chart of an implementation method of an accelerometer sensitivity calibration method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] This invention provides a method and device for calibrating the sensitivity of an accelerometer. This device provides excellent vibration noise suppression within the 0.001Hz to 1Hz frequency band, overcoming the shortcomings of conventional calibration devices and methods, which suffer from low calibration accuracy and susceptibility to environmental influences. It can effectively improve the accuracy of ground-based measurement of the sensitivity coefficient of high-precision accelerometers.

[0036] like Figure 1 and Figure 2 As shown, the present invention provides an accelerometer sensitivity calibration device, comprising: a shielding cover 1, a precision angle measuring instrument 2, an accelerometer to be measured 3, a precision displacement adjustment platform 4, a displacement adjustment mass block 5, a vibration isolation foundation 6 and a tilt compensation pendulum 7;

[0037] The accelerometer to be measured 3, the precision angular velocity measuring instrument 2, and the precision displacement adjustment platform 4 are mounted on the platform 71 of the tilt compensation pendulum 7; the displacement adjustment mass block 5 is placed on the precision displacement adjustment platform 4; the tilt compensation pendulum 7 and the shielding cover 1 are mounted on a horizontal vibration isolation foundation 6, and the shielding cover 1 completely covers the tilt compensation pendulum 7; the precision angle measuring instrument 2, the accelerometer to be measured 3, and the precision displacement adjustment platform 4 are all powered by batteries and use a wireless communication module 73 for communication with an external PC.

[0038] The shielding cover 1 is a container that can reduce airflow, electromagnetic fields, or temperature interference. The material includes but is not limited to wood, metal, and glass. If necessary, the inside of the shielding cover 1 can be evacuated to further reduce the impact of environmental factors.

[0039] The accelerometer 3 to be tested is an instrument capable of measuring linear acceleration, including but not limited to a MEMS accelerometer, a reed accelerometer, and an electrostatic suspension accelerometer;

[0040] The combination of the precision displacement adjustment platform 4 and the displacement adjustment mass block 5 can achieve sub-μrad to μrad angle adjustment of the two horizontal orthogonal axes of the platform 71 and the horizontal direction through the sub-mm to sub-m displacement platform stroke and the g to sub-kg mass block mass, so as to provide sub-μg to μg acceleration calibration signals; the precision displacement adjustment platform includes but is not limited to an electrically controlled linear displacement platform and a six-degree-of-freedom displacement platform;

[0041] Precision angle measuring instrument 2, with an angle measurement resolution of nrad / Hz 1 / 2The horizontal and measuring range is greater than 1000 μrad, which can realize simultaneous and uninterrupted monitoring of the angle change of the two horizontal orthogonal axes of the tilt compensation platform 7 relative to the horizontal direction. The precision angle measuring instrument includes but is not limited to a mechanical inclinometer and a photoelectric autocollimator;

[0042] The tilt compensation platform 7 can isolate the ground vibration noise in the frequency band of 0.001Hz to 1Hz from being transmitted to the accelerometer 3 to be tested;

[0043] like Figure 3 As shown in FIG, the implementation process of the accelerometer sensitivity calibration method provided by the embodiment of the present invention is given:

[0044] Step 1: Align the electrostatically suspended accelerometer with the center of the platform mounted on the tilt compensation pendulum, ensuring that the horizontal sensitive axis of the accelerometer to be measured coincides with the two horizontal orthogonal axes of the platform. Use high-voltage suspension to ensure normal operation. Adjust the position and mass of the balancing mass block on the tilt compensation pendulum to adjust the horizontal control output of the accelerometer to zero.

[0045] Step 2: After closing the shield, the tilting platform is stable for a long enough time to make the angular noise of the platform fall below the required limit, such as 30nrad / HZ 1 / 2 Among them, the tilt compensation swing table enters the vibration isolation state, and the shielding cover realizes the isolation of the tilt compensation swing table from the external environment, and it takes a long enough time to stabilize and reach the optimal vibration isolation state;

[0046] Step 3: According to the accelerometer range, set the linear translation stage movement program and set the calibration step signals in the two horizontal directions of the accelerometer, including the number of steps N and the duration of each step T. This allows for setting a relatively large number of calibration points while allowing sufficient time to obtain stable calibration data. For example, a calibration step signal with 13 steps and a duration of 200 seconds per step can be set.

[0047] Step 4: Use a mechanical inclinometer to monitor and record the platform's pitch and roll angle data θ, while also recording the accelerometer's horizontal control output data V. The platform's tilt angle data is multiplied by the gravitational acceleration g to obtain the accelerometer calibration signal.

[0048] Step 5: Select the stable segments of the middle 70% step duration of the two sets of calibration data for processing, eliminate the influence of the initial stage of platform inclination change, and obtain the average value and standard deviation of each step segment respectively;

[0049] Step 6: Use the least squares linear regression analysis on the above mean data to obtain the linear relationship between the accelerometer calibration signal and the accelerometer control output signal. The first-order coefficient is the sensitivity coefficient of the accelerometer to be tested: K1 = Δθg / ΔV;

[0050] Step 7: Perform error analysis on the linear regression fitting process of the tilt compensation platform's inclination data θ and the accelerometer's horizontal control output data V to obtain the calibration coefficient standard error ΔK1. Divide it by the sensitivity coefficient to obtain the Class A relative uncertainty of the calibration sensitivity coefficient.

[0051] In summary, the present invention has the following advantages compared with the prior art:

[0052] The present invention provides an accelerometer sensitivity calibration device, wherein the tilt compensation swing table is used to isolate the ground vibration noise in the frequency band of 0.001Hz to 1Hz from being transmitted to the acceleration to be measured, that is, to provide the accelerometer to be measured with a vibration level of ng / Hz in the frequency band of 0.001Hz to 1Hz. 1 / 2 In an environment with a magnitude of 0.1, the impact of ground vibration on accelerometer calibration is reduced.

[0053] The present invention provides an accelerometer sensitivity calibration device, which utilizes the tilt angles of the pitch angle and roll angle of the tilt compensation platform to realize the use of the horizontal component of gravity acceleration as the acceleration input in the horizontal sensitive axis direction of the accelerometer. It can provide an acceleration calibration source with an accuracy of sub-μg and a range of μg, meeting the calibration accuracy and range of high-precision accelerometers.

[0054] The present invention provides an accelerometer sensitivity calibration method, which uses a high-precision angle measuring instrument to accurately monitor and record the tilt angle changes of a tilt compensation pendulum. After screening the calibration data, linear regression fitting analysis is used to calibrate the accelerometer sensitivity coefficient and calculate the Class A relative uncertainty.

[0055] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An accelerometer sensitivity calibration device, characterized in that: include: Shielding cover, precision angle measuring instrument, precision displacement adjustment platform, displacement adjustment mass block, vibration isolation foundation and tilt compensation pendulum platform; The accelerometer to be measured, the precision angular velocity measuring instrument, and the precision displacement adjustment platform are mounted on the tilt compensation pendulum; the displacement adjustment mass block is placed on the precision displacement adjustment platform; the tilt compensation pendulum and the shielding cover are mounted on the horizontal vibration isolation foundation, and the shielding cover completely covers the tilt compensation pendulum; the precision angle measuring instrument, the accelerometer to be measured, and the precision displacement adjustment platform all use batteries and wireless communication modules for power supply and communication with external PC-side data monitoring software, respectively. The shielding cover is a container that reduces airflow, electromagnetic field or temperature interference; the accelerometer to be measured is an instrument for measuring linear acceleration; The combination of the precision displacement adjustment platform and the displacement adjustment mass block is used to achieve sub-μrad to μrad level angle adjustment of the platform pitch angle and roll angle of the tilt compensation swing table through the sub-millimeter to sub-meter displacement stage stroke and the g to sub-kg mass block mass, respectively, to provide sub-μrad g to μ g The precision angle measuring instrument is used to continuously monitor the angle data of the pitch angle and roll angle of the tilt compensation platform; The tilt compensation platform is used to isolate the ground vibration noise in the frequency band of 0.001Hz~1Hz from being transmitted to the accelerometer to be tested; The tilt compensation platform includes a platform, a balancing mass block, a rigid connecting rod, a suspension frame and a suspension hinge; The two ends of the suspension hinge are respectively fixedly connected to the suspension frame and several rigid links; the other end of the rigid link is fixedly connected to the platform; any two rigid links and the platform are constructed into a triangular shape, and several rigid links and the suspension hinge are used together to play the role of suspending the platform, and are also used to attenuate vibrations higher than the natural frequency of the tilt compensation pendulum table and transmit them to the platform; the suspension hinge is used to allow the platform to swing freely in the vertical plane and suppress the torsional movement of the platform in the horizontal plane; the battery and wireless communication module are placed on the platform to reduce the influence of external cables of the equipment to be tested on the vibration isolation performance of the tilt compensation pendulum table; the balancing mass block is used to adjust the horizontal control output of the accelerometer to be tested to zero.

2. The accelerometer sensitivity calibration device according to claim 1, characterized in that: The angle measurement resolution of the precision angle measuring instrument reaches nrad / Hz 1 / 2 The horizontal and measuring range is greater than 1000 μrad.

3. The accelerometer sensitivity calibration device according to claim 1, characterized in that: The accelerometers to be tested are MEMS accelerometer, reed accelerometer and electrostatic suspension accelerometer.

4. The accelerometer sensitivity calibration method based on the accelerometer sensitivity calibration device according to claim 1, characterized in that: The following steps are involved: Step 1: Adjust the position and mass of the balancing mass block on the tilt compensation platform to adjust the horizontal control output of the accelerometer to be tested to zero; Step 2: After closing the shielding cover, stabilize the tilt compensation platform for a preset time so that the angular noise of the tilt compensation platform falls below the required limit; Step 3: Set up a displacement adjustment mass block movement program to generate multiple calibration steps within the range of the accelerometer to be measured; Step 4: Monitor and record the pitch and roll angle data of the tilt compensation platform , and record the horizontal control output data of the accelerometer to be tested ; Among them, the platform's inclination data Multiply by the acceleration due to gravity g Then the input calibration signal of the accelerometer is obtained; Step 5: After calibration, obtain the pitch and roll angle data of the tilt compensation platform. And the horizontal direction control output data of the accelerometer The data of the middle stable section of each step are statistically analyzed to obtain the average value and standard deviation of each step; Step 6: Perform linear regression fitting analysis on the average values ​​of each step of the pitch and roll angle data of the tilt compensation platform and the average values ​​of each step of the horizontal control output data of the accelerometer to obtain the linear relationship between the control output signal of the accelerometer to be tested and the input calibration signal. The first-order term coefficient in the linear relationship is the sensitivity coefficient of the accelerometer to be tested. Step 7: Tilt compensation table inclination data And the horizontal direction control output data of the accelerometer The error analysis of the linear regression fitting process is performed to obtain the standard error of the sensitivity coefficient , divided by the sensitivity coefficient, to obtain the Class A relative uncertainty of the calibration sensitivity coefficient.

5. The accelerometer sensitivity calibration method according to claim 4, characterized in that: In step three, the number of calibration steps and the duration of each step are set according to the measuring range of the accelerometer to be measured.

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