Offline dynamic calibration method for acceleration sensor

Abstract

The invention discloses an off-line dynamic calibration method for an acceleration sensor, and relates to the field of device calibration. The method for off-line dynamic calibration of the acceleration sensor comprises the following steps: acquiring a frequency response function ratio Pab (f) of a standard acceleration sensor to a calibrated acceleration sensor; installing the calibrated acceleration sensor on a test piece to carry out an ejection test to obtain an ejection test data sequence Yb (m); and calibrating the ejection test data sequence Yb (m) by adopting the frequency response function ratio Pab (f) of the standard acceleration sensor and the calibrated acceleration sensor to obtain a calibrated ejection test data sequence Ycb (m). The method for off-line dynamic calibration of the acceleration sensor can effectively improve the measurement accuracy and consistency of ejection test acceleration data, remarkably reduces the test cost of an ejection test, and is suitable for the field of aviation lifesaving ejection tests and the field of lifesaving parachute air-drop tests.

Description

Technical Field

[0001] This application relates to the field of device calibration. Specifically, it relates to a method for off-line dynamic calibration of an acceleration sensor. Background Art

[0002] In the ejection escape test, an acceleration sensor is required to accurately measure the acceleration of test pieces such as escape devices, and it is required that the relative damping ratio of the acceleration sensor is not less than 0.6 - 0.7. However, in actual ejection test measurements, this requirement is often not met due to various reasons. For example, the acceleration sensor cannot be directly installed on the test piece according to the standard requirements, but an installation tooling needs to be added. At this time, the coupling effect between the installation tooling and the acceleration sensor may change the overall equivalent damping ratio of the acceleration sensor. Another example is that the internal components of the acceleration sensor are worn due to long-term use in an impact and vibration environment, resulting in a change in its damping ratio parameter. In addition, even if the damping ratio parameters of different acceleration sensors meet the standard requirements, that is, the damping ratio is not less than 0.6 - 0.7, it is very difficult for the damping ratio parameters of each acceleration sensor to be exactly the same. For example, the damping ratio of acceleration sensor a is 0.65, the damping ratio of acceleration sensor b is 0.7, and the damping ratio of acceleration sensor c is 1.0, all of which meet the standard requirements. However, these acceleration sensors will give significantly different acceleration data in the same ejection test, affecting the analysis and determination of test performance.

[0003] Therefore, a method is needed to make the overall equivalent damping ratio of each calibrated acceleration sensor equivalent to the damping ratio parameter of the selected standard sensor to meet the usage requirements. Summary of the Invention

[0004] The purpose of this application is to provide a method for off-line dynamic calibration of an acceleration sensor, which can effectively improve the measurement accuracy and consistency of acceleration data in ejection tests, and at the same time significantly reduce the test cost of ejection tests.

[0005] This application is implemented as follows:

[0006] This application provides a method for off-line dynamic calibration of an acceleration sensor, including the following steps:

[0007] Obtain the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated;

[0008] Install the acceleration sensor to be calibrated on the test piece to conduct an ejection test to obtain an ejection test data sequence Yb(m);

[0009] The ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated is used to calibrate the catapult test data sequence Yb(m) to obtain the calibrated catapult test data sequence Ycb(m).

[0010] In some alternative embodiments, obtaining the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated includes the following steps:

[0011] Connect the standard acceleration sensor and the acceleration sensor to be calibrated and install them on the vibration table;

[0012] Apply a swept-frequency excitation signal to the vibration table, and record the output data of the standard acceleration sensor and the acceleration sensor to be calibrated to obtain the data sequences Xa(n) and Xb(n) respectively;

[0013] Calculate the frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the acceleration sensor to be calibrated according to the data sequences Xa(n) and Xb(n);

[0014] Calculate Pab(f) = Pa(f) / Pb(f) according to the frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the acceleration sensor to be calibrated.

[0015] In some alternative embodiments, the frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the acceleration sensor to be calibrated are calculated by using the discrete Fourier transform on the data sequences Xa(n) and Xb(n) respectively.

[0016] In some alternative embodiments, calibrating the catapult test data sequence Yb(m) by using the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated includes the following steps:

[0017] Perform a discrete Fourier transform on the catapult test data sequence Yb(m) to obtain the spectral function Pyb(f);

[0018] Calculate the frequency response function Pcyb(f) of the calibrated test data according to the formula:

[0019] Pcyb(f) = Pyb(f) × Pab(f);

[0020] Calculate the calibrated catapult test data sequence Ycb(m) according to the frequency response function Pcyb(f) of the calibrated test data.

[0021] In some alternative embodiments, the frequency response function Pcyb(f) of the calibrated test data is used to calculate the calibrated catapult test data sequence Ycb(m) according to the inverse discrete Fourier transform.

[0022] In some alternative embodiments, calibrating the ejection test data sequence Yb(m) by using the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated includes the following steps:

[0023] Performing an inverse discrete Fourier transform on the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated to obtain a calibration data sequence Cab(n);

[0024] Performing a convolution calculation on the ejection test data sequence Yb(m) and the calibration data sequence Cab(n) to obtain a calibrated ejection test data sequence Ycb(m):

[0025] Ycb(m) = Yb(m) * Cab(n).

[0026] In some alternative embodiments, the standard acceleration sensor and the acceleration sensor to be calibrated are coaxially connected and mounted on a vibration table.

[0027] In some alternative embodiments, a swept-frequency excitation signal within the frequency response upper limit is applied to the vibration table.

[0028] The beneficial effects of the present application are as follows: The method for offline dynamic calibration of an acceleration sensor provided by the present application includes the following steps: obtaining the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated; mounting the acceleration sensor to be calibrated on a test piece to perform an ejection test to obtain an ejection test data sequence Yb(m); calibrating the ejection test data sequence Yb(m) by using the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated to obtain a calibrated ejection test data sequence Ycb(m). The method for offline dynamic calibration of an acceleration sensor provided by the present application can effectively improve the measurement accuracy and consistency of ejection test acceleration data, and at the same time significantly reduce the test cost of ejection tests, and is applicable to the fields of aviation rescue ejection tests and life-saving parachute airdrop tests. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a schematic flowchart of the method for offline dynamic calibration of an acceleration sensor provided by an embodiment of the present application; Detailed Embodiments

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Apparently, the described embodiments are some but not all of the embodiments of this application.

[0032] Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of this application that is claimed, but merely represents selected embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of this application without creative efforts shall fall within the scope of protection of this application.

[0033] The features and performance of the method for offline dynamic calibration of the acceleration sensor of this application will be further described in detail below in conjunction with embodiments.

[0034] As Figure 1 shown, the embodiments of this application provide a method for offline dynamic calibration of an acceleration sensor, including the following steps:

[0035] Step 1: Obtain the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated, including the following steps:

[0036] 1.1 Obtain the standard acceleration sensor from the metrology calibration unit and clarify the parameter indicators; optionally, the damping ratio of the standard acceleration sensor is 0.7 to 0.8, and the frequency response is 0 to 2000 Hz;

[0037] 1.2 Coaxially connect and install the standard acceleration sensor and the acceleration sensor to be calibrated with a tooling on the vibration table, and connect the test system to the standard acceleration sensor and the acceleration sensor to be calibrated;

[0038] 1.3 Apply a swept-frequency excitation signal within the frequency response upper limit that the test equipment can apply to the vibration table, and record the output data of the standard acceleration sensor and the acceleration sensor to be calibrated to obtain the data sequences Xa(n) and Xb(n) respectively;

[0039] 1.4 Respectively use the discrete Fourier transform DFT to calculate the data sequences Xa(n) and Xb(n) to obtain the frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the acceleration sensor to be calibrated; f represents the frequency variable;

[0040] 1.5 Calculate the ratio Pab(f) of the frequency response functions according to the frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the acceleration sensor to be calibrated, that is, the calibration factor frequency response function Pab(f), where Pab(f) = Pa(f) / Pb(f).

[0041] Step 2: Install the accelerometer to be calibrated on the test piece and conduct a catapult test to obtain the catapult test data sequence Yb(m).

[0042] Step 3: Use the calibration factor frequency response function Pab(f) to calibrate the catapult test data sequence Yb(m) according to the following Step A or Step B to obtain the calibrated catapult test data sequence Ycb(m):

[0043] Step A: Perform a discrete Fourier transform calculation on the catapult test data sequence Yb(m) to obtain the spectrum function Pyb(f); calculate the calibrated test data frequency response function Pcyb(f) according to the following formula: Pcyb(f) = Pyb(f) × Pab(f); perform an inverse discrete Fourier transform calculation on the calibrated test data frequency response function Pcyb(f) to obtain the calibrated catapult test data sequence Ycb(m).

[0044] Step B: Perform an inverse discrete Fourier transform on the ratio of the frequency response functions of the standard accelerometer and the accelerometer to be calibrated, Pab(f), to obtain the calibration data sequence Cab(n); perform a convolution calculation on the catapult test data sequence Yb(m) and the calibration data sequence Cab(n) to obtain the calibrated catapult test data sequence Ycb(m): Ycb(m) = Yb(m) * Cab(n).

[0045] The method for offline dynamic calibration of an accelerometer provided by the embodiments of the present application connects the standard accelerometer and the accelerometer to be calibrated coaxially to a vibration table, applies a swept-frequency excitation signal within the frequency response upper limit, records the output data sequences Xa(n) and Xb(n), and respectively performs a discrete Fourier transform calculation on the data sequences Xa(n) and Xb(n) to obtain the frequency response functions Pa(f) and Pb(f) of the standard accelerometer and the accelerometer to be calibrated, and then obtains the ratio of the frequency response functions Pab(f). Then, according to the ratio of the frequency response functions Pab(f), the catapult test data sequence Yb(m) obtained by installing the accelerometer to be calibrated on the test piece during the catapult test can be calibrated to obtain the calibrated catapult test data sequence Ycb(m). This can effectively improve the measurement accuracy of the catapult test acceleration data, and make the damping ratio parameters of multiple sensors equivalent and consistent, which is beneficial to the consistency and unity of the performance data analysis and comparison of multiple catapult rescue tests. It can relax the requirements for some dynamic frequency response parameter indicators of the accelerometer in the selection and procurement work of the accelerometer to meet the relevant standard requirements, thereby effectively reducing the test cost. It can be applied to fields such as life-saving parachute airdrop tests and parachute opening dynamic load tests.

[0046] The embodiments described above are some, but not all, of the embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

Claims

1. A method for offline dynamic calibration of an acceleration sensor, characterized in that: The following steps are involved: Obtaining the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the acceleration sensor to be calibrated; The calibrated acceleration sensor is installed on the test piece to perform a ejection test to obtain the ejection test data sequence Yb(m); The ejection test data sequence Yb(m) is calibrated using the frequency response function ratio Pab(f) of the standard acceleration sensor and the calibrated acceleration sensor to obtain a calibrated ejection test data sequence Ycb(m).

2. The method for offline dynamic calibration of an acceleration sensor according to claim 1, characterized in that: Obtaining the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the calibrated acceleration sensor comprises the following steps: Connect the standard acceleration sensor and the calibrated acceleration sensor and install them on the vibration table; Applying a sweep frequency excitation signal to the vibration table, recording the output data of the standard acceleration sensor and the calibrated acceleration sensor to obtain data sequences Xa(n) and Xb(n) respectively; The frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the calibrated acceleration sensor are calculated according to the data sequences Xa(n) and Xb(n); Pab(f)=Pa(f) / Pb(f) is calculated based on the frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the calibrated acceleration sensor.

3. The method for offline dynamic calibration of an acceleration sensor according to claim 2, characterized in that: The frequency response functions Pa(f) and Pb(f) of the standard acceleration sensor and the calibrated acceleration sensor are respectively calculated by discrete Fourier transform from the data sequences Xa(n) and Xb(n).

4. The method for offline dynamic calibration of an acceleration sensor according to claim 1, characterized in that: The method of calibrating the ejection test data sequence Yb(m) by using the ratio Pab(f) of the frequency response function of the standard acceleration sensor and the calibrated acceleration sensor comprises the following steps: The ejection test data sequence Yb(m) is subjected to discrete Fourier transform calculation to obtain the spectrum function Pyb(f); The frequency response function Pcyb(f) of the test data after calibration is calculated according to the formula: Pcyb(f)=Pyb(f)×Pab(f); The calibration ejection test data sequence Ycb(m) is calculated based on the calibrated test data frequency response function Pcyb(f).

5. The method for offline dynamic calibration of an acceleration sensor according to claim 4, characterized in that: The calibrated test data frequency response function Pcyb(f) is calculated based on the inverse discrete Fourier transform to obtain the calibration ejection test data sequence Ycb(m).

6. The method for offline dynamic calibration of an acceleration sensor according to claim 1, characterized in that: The method of calibrating the ejection test data sequence Yb(m) by using the ratio Pab(f) of the frequency response function of the standard acceleration sensor and the calibrated acceleration sensor comprises the following steps: Performing an inverse discrete Fourier transform on the ratio Pab(f) of the frequency response functions of the standard acceleration sensor and the calibrated acceleration sensor to obtain a calibration data sequence Cab(n); The ejection test data sequence Yb(m) and the calibration data sequence Cab(n) are convolved to obtain the calibration ejection test data sequence Ycb(m): Ycb(m)=Yb(m)*Cab(n).

7. The method for offline dynamic calibration of an acceleration sensor according to claim 1, characterized in that: The standard acceleration sensor is coaxially connected with the calibrated acceleration sensor and is installed on the vibration table.

8. The method for offline dynamic calibration of an acceleration sensor according to claim 2, characterized in that: A swept frequency excitation signal within an upper frequency response limit is applied to the vibration table.

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