阅读说明：本技术 一种基于激波管的阶跃加速度校准装置 (Step acceleration calibrating device based on shock tube ) 是由 刘渊 杨军 梁志国 姜延欢 于 2020-11-18 设计创作，主要内容包括：本发明公开的一种基于激波管的阶跃加速度校准装置,属于计量测试领域。本发明包括激波管激励装置、加速度计安装缸体、加速度计安装活塞、激光测速仪、加速度计、数据采集卡,还包括数据采集计算机。本发明使用激波管产生的压力激波对加速度计进行激励,压力激波作用于激波管端面的气缸装置,推动安装于气缸活塞上的加速度计向前运动,获得加速度计的测量输出；同时布置于加速度计端面另一侧的激光测速仪获得加速度计运动的标准加速度信号,通过对比两路信号实现加速度计校准,能够用于高频响加速度计的冲击校准,有效激励。本发明加速度幅值由调节破膜压力调节,产生的加速度幅值可控,准确度在1％以内。(The invention discloses a step acceleration calibration device based on a shock tube, and belongs to the field of metering tests. The invention comprises a shock tube exciting device, an accelerometer mounting cylinder, an accelerometer mounting piston, a laser velocimeter, an accelerometer, a data acquisition card and a data acquisition computer. The invention uses the pressure shock wave generated by the shock tube to excite the accelerometer, the pressure shock wave acts on the cylinder device on the end face of the shock tube to push the accelerometer arranged on the cylinder piston to move forwards, and the measurement output of the accelerometer is obtained; meanwhile, the laser velocimeter arranged on the other side of the end face of the accelerometer obtains a standard acceleration signal of the movement of the accelerometer, and the calibration of the accelerometer is realized by comparing two paths of signals, so that the method can be used for impact calibration of the high-frequency response accelerometer and effective excitation. The acceleration amplitude of the invention is adjusted by adjusting the rupture membrane pressure, the generated acceleration amplitude is controllable, and the accuracy is within 1%.)

1. The utility model provides a step acceleration calibrating device based on shock tube, includes shock tube (1) excitation device, accelerometer installation cylinder body (6), accelerometer installation piston (7), laser velocimeter (8), accelerometer (9), data acquisition card (10), its characterized in that: the system also comprises a data acquisition computer;

the shock tube (1) is used as dynamic pressure calibration equipment and is used for generating step pressure with the rise time within 1 microsecond; the shock tube structure mainly comprises a high-pressure section (2), a low-pressure section (5), a transition section, a film clamping machine, a high-pressure gas cylinder (11) and a pressure control valve;

the accelerometer mounting device consists of a cylinder body and a piston, wherein the cylinder body is connected with the end face of the low-pressure section (5) of the shock tube through a sealing ring and threads and keeps sealed; an accelerometer mounting piston (7) is arranged in the cylinder body, and the accelerometer mounting piston (7) can freely move back and forth; one end of the accelerometer, which is provided with the piston (7), is a plane and is used for bearing the excitation of pressure shock waves; the processing depth of the other end of the accelerometer mounting piston (7) is equal to the height of the accelerometer (9) to be calibrated, and the diameter of the accelerometer mounting piston is slightly larger than the groove of the outer diameter of the accelerometer (9) to be calibrated; a mounting hole with threads is processed at the bottom of the groove and is connected with the calibrated accelerometer (9) through a bolt;

the laser velocimeter (8) mainly comprises a beam prism, a laser, a photoelectric receiver and a demodulation circuit;

the front end interface of the data acquisition card (10) is connected with an accelerometer (9) to be calibrated and an output cable of the laser velocimeter (8), and the rear end is connected with a communication interface of a post-processing computer; and the post-processing computer is provided with data acquisition and processing software and performs visual processing on the acquired data.

2. The shock tube-based step acceleration calibration device of claim 1, wherein: the shock tube (1) is used as an accelerometer calibration excitation device, a cylinder structure and the outer wall of a piston are used to guarantee the stable operation of the accelerometer in the calibration process, a cylinder piston is composed of a bottom and a cylindrical outer wall, the bottom is mainly used for bearing pressure shock excitation, and the outer wall is mainly used for motion guiding of the piston.

3. The shock tube-based step acceleration calibration device of claim 1, wherein: an accelerometer (9) arranged on a cylinder piston is subjected to acceleration measurement tracing by using a laser velocimeter (8); the laser velocimeter (8) obtains an acceleration signal of the bottom of the accelerometer mounting piston (7) in the motion process through optical principle measurement; the measuring signals are stored in a data acquisition computer through a data acquisition card (10).

4. The shock tube-based step acceleration calibration device of claim 1, wherein: the calibration of the accelerometer (9) is completed by acquiring a step response amplitude value of the accelerometer (9) after being excited by the shock wave and an acceleration measurement result of the laser velocimeter (8); the acceleration signal peak value and the acceleration signal waveform measured by an accelerometer (9) and a laser velocimeter (8) in a data acquisition computer are used for establishing a second-order system transfer function, and uncertainty evaluation is carried out on model parameters in the transfer function, so that model-based step acceleration excitation and calibration are realized.

5. A shock tube-based step acceleration calibration device according to claim 1, 2, 3 or 4, characterized in that: the working method is that an O-shaped sealing ring is placed at the interface of the high-pressure cavity and the low-pressure cavity, and a diaphragm is installed; installing the transition section in the low pressure cavity, and then assembling the high pressure cavity, the low pressure cavity and the transition section together; an accelerometer (9) is arranged in a groove of an accelerometer mounting clamp, and glass beads are adhered to the bottom of the groove of an accelerometer mounting piston (7) to increase the optical reflectivity; the laser velocimeter (8) is powered on and is started to preheat, so that the measurement effect is better; then, inflating the high-pressure chamber, monitoring the pressure of the high-pressure chamber and the low-pressure chamber by using a pressure sensor, and automatically breaking the diaphragm when a preset pressure value is reached to form pressure shock waves; and a piston (7) is arranged on the accelerometer at the position of the bottom end face of the pressure shock wave impact low-pressure cavity, and the step acceleration calibration is realized by comparing the output signal of the accelerometer (9) with the measurement result of the laser velocimeter (8).

6. The shock tube-based step acceleration calibration device of claim 5, wherein: the accelerometer mounting device mainly comprises a cylinder body and a piston, wherein the cylinder body is made of stainless steel.

7. The shock tube-based step acceleration calibration device of claim 5, wherein: the piston is processed by titanium alloy material.

8. The shock tube-based step acceleration calibration device of claim 5, wherein: and (4) switching on a power supply of the laser velocimeter (8) and starting up for preheating for 30 minutes.

Technical Field

The invention relates to a step acceleration calibration device based on a shock tube, and belongs to the field of metering test.

Background

The accelerometer calibration is usually realized by an impactor, the air-gun type impactor is widely applied to accelerometer calibration due to the advantages of capability of generating impact acceleration in a large range, good stability and the like, and the air-gun type impactor is used as an excitation source of the accelerometer in a calibration device. The waveform generated by the air gun type impact machine is generally a half-sine waveform, and the higher the waveform quality is, the more accurate the accelerometer calibration result is. To produce high quality waveforms during calibration, bullets and cushions of various shapes and sizes need to be designed.

When the accelerometers of various types are calibrated, the excitation range of one air cannon type impact machine cannot meet the requirement when the range change of the accelerometers is large, and meanwhile, for the accelerometers with high g values, the frequency response range is wide, and the waveform pulse width generated by the conventional air cannon type impact machine cannot excite the frequency characteristic of the accelerometers. The generation of narrow pulse width excitation waveforms requires a means such as raising the pressure of the high pressure chamber, which increases the design difficulty and manufacturing cost of the high pressure chamber and barrel, and also puts high requirements on the design of the bullets and the cushion pad. Meanwhile, the traditional impact acceleration excitation device completes excitation through elastic collision between solids, along with the occurrence of requirements such as acceleration measurement when a body collides with water flow when a seaplane falls into water, the calibration requirement of the accelerometer under partial scenes cannot be met through a mode that acceleration excitation is generated through collision between the solids, and fluid is needed to be adopted to excite and calibrate the accelerometer to solve the problem.

Disclosure of Invention

The invention discloses a step acceleration calibration device based on a shock tube, aiming at solving the problems that the waveform pulse width generated by the traditional air gun type impactor is wider and cannot meet the excitation requirement of a high-response frequency accelerometer, and the traditional air gun type impactor cannot accurately excite and calibrate the accelerometer used in the fluid-solid coupling working condition.

The purpose of the invention is realized by the following technical scheme.

The invention discloses a step acceleration calibration device based on a shock tube, which comprises a shock tube excitation device, an accelerometer mounting cylinder, an accelerometer mounting piston, a laser velocimeter, an accelerometer, a data acquisition card and a data acquisition computer.

The shock tube is used as dynamic pressure calibration equipment and is used for generating step pressure with rising time within 1 microsecond; the shock tube structure mainly comprises a high-pressure section, a low-pressure section, a transition section, a film clamping machine, a high-pressure gas cylinder and a pressure control valve.

The accelerometer mounting device consists of a cylinder body and a piston, wherein the cylinder body is connected with the end face of the low-pressure section of the shock tube through a sealing ring and threads and keeps sealed; the accelerometer mounting piston is arranged in the cylinder body and can freely move back and forth; one end of the accelerometer, which is provided with the piston, is a plane and is used for bearing the excitation of pressure shock waves; the processing depth of the other end of the accelerometer mounting piston is equal to the height of the accelerometer to be calibrated, and the diameter of the accelerometer mounting piston is slightly larger than the groove of the outer diameter of the accelerometer to be calibrated; the bottom of the groove is provided with a threaded mounting hole and is connected with the calibrated accelerometer through a bolt.

The laser velocimeter mainly comprises a beam prism, a laser, a photoelectric receiver and a demodulation circuit.

The front end interface of the data acquisition card is connected with an accelerometer to be calibrated and an output cable of the laser velocimeter, and the rear end of the data acquisition card is connected with a communication interface of a post-processing computer; and the post-processing computer is provided with data acquisition and processing software and performs visual processing on the acquired data.

Preferably, a shock tube is used as an accelerometer calibration excitation device, a cylinder structure and the outer wall of a piston are used for guaranteeing the stable operation of the accelerometer in the calibration process, the cylinder piston is composed of a bottom and a cylindrical outer wall, the bottom is mainly used for bearing the pressure shock wave excitation, and the outer wall is mainly used for the motion guidance of the piston.

Preferably, a laser velocimeter is used for carrying out acceleration measurement tracing on an accelerometer arranged on a cylinder piston; the laser velocimeter obtains an acceleration signal of the bottom of the piston with the accelerometer installed in the movement process through measurement of an optical principle; the measuring signal is stored in the data acquisition computer through the data acquisition card.

Preferably, the calibration of the accelerometer is completed by acquiring a step response amplitude value of the accelerometer after being excited by the shock wave and an acceleration measurement result of the laser velocimeter; the method comprises the steps of establishing a second-order system transfer function by using acceleration signal peak values and waveforms measured by an accelerometer and a laser velocimeter in a data acquisition computer, and carrying out uncertainty evaluation on model parameters in the transfer function to realize step acceleration excitation and calibration based on a model.

The invention discloses a working method of a step acceleration calibration device based on a shock tube, which comprises the following steps:

placing an O-shaped sealing ring at the interface of the high-pressure cavity and the low-pressure cavity, and installing a diaphragm; installing the transition section in the low pressure cavity, and then assembling the high pressure cavity, the low pressure cavity and the transition section together; fixing an accelerometer in an accelerometer mounting clamp groove at the end part of the piston through a bolt, and adhering glass beads at the bottom of the accelerometer mounting seat groove to increase the optical reflectivity; the laser velocimeter is powered on and is started to preheat, so that the measurement effect is better; then, inflating the high-pressure chamber, monitoring the pressure of the high-pressure chamber and the low-pressure chamber by using a pressure sensor, and automatically breaking the diaphragm when a preset pressure value is reached to form pressure shock waves; and a piston is arranged on the accelerometer at the bottom end face of the pressure shock wave impact low-pressure cavity, and the step acceleration calibration is realized by comparing the output signal of the accelerometer with the measurement result of the laser velocimeter.

Preferably, the accelerometer mounting device mainly comprises a cylinder and a piston, wherein the cylinder is made of stainless steel.

Preferably, the piston is machined from a titanium alloy material.

Preferably, the laser velocimeter is powered on and is powered on to preheat for 30 minutes.

Has the advantages that:

1. aiming at the problems that when an accelerometer with high frequency response is calibrated, the excitation pulse width is wide, high-frequency response excitation cannot be met, and accurate excitation calibration cannot be carried out on the accelerometer used under the fluid-solid coupling working condition, the invention discloses a step acceleration calibration device based on a shock tube. And meanwhile, the laser velocimeter arranged on the other side of the end surface of the accelerometer obtains a standard acceleration signal of the movement of the accelerometer, and the calibration of the accelerometer is realized by comparing two paths of signals, so that the method can be used for the impact calibration of the high-frequency response accelerometer.

2. The invention discloses a step acceleration calibration device based on a shock tube, which adopts the shock tube as a step acceleration generation device, can generate acceleration with very short rise time, and the rise time of the front edge of the step wave is controlled within 1 microsecond. The acceleration amplitude is adjusted by adjusting the rupture pressure, the generated acceleration amplitude is controllable, and the accuracy is within 1%. Compared with the traditional impact calibration device, the shock tube is used as an accelerometer calibration excitation source, so that accurate and effective excitation of the high-response frequency accelerometer can be realized.

Drawings

Fig. 1 is a schematic diagram of a shock tube-based step acceleration calibration apparatus.

Wherein: the device comprises an air shock tube 1, a shock tube 2, a shock tube high-pressure section 3, a high-low pressure section assembling clamp, an aluminum thin film 4, a shock tube 5, an accelerometer 6, an accelerometer mounting cylinder, an accelerometer 7, an accelerometer mounting piston 8, a laser velocimeter 9, an accelerometer 10, a data acquisition card 11, a compressed air bottle 12, a gas pressure gauge 13, a pressure reducing valve 14 and a gas connecting valve.

Detailed Description

For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.

Example 1:

as shown in fig. 1, the shock tube-based step acceleration calibration device disclosed in this embodiment is composed of an air shock tube 1, a shock tube high-pressure section 2, a high-low pressure section assembling jig 3, an aluminum thin film 4, a shock tube low-pressure section 5, an accelerometer mounting cylinder 6, an accelerometer mounting piston 7, a laser velocimeter 8, an accelerometer 9, a data acquisition card 10, a compressed air bottle 11, a barometer 12, a pressure reducing valve 13, and a gas connection valve 14.

The assembling and working method of the shock tube-based step acceleration calibration device disclosed by the embodiment comprises the following steps:

and (3) opening a connecting bolt of the high-low pressure section assembling clamp 3, separating the high-pressure section 2 and the low-pressure section 5 of the air shock tube 1, installing the processed aluminum thin film 4 on the high-low pressure assembling section 3, and then assembling the high-low pressure section. The accelerometer 9 is installed in a groove of the accelerometer installation piston 7 through a bottom threaded connection structure, and glass beads are adhered to the bottom of the groove of the accelerometer installation piston 7, so that the light reflection coefficient of the end face is increased. And (3) switching on a power supply of the laser velocimeter 8, starting the machine for preheating for 30 minutes, and adjusting the focal length of a lens of the laser velocimeter 8 to focus laser on the surface of the glass microsphere adhered to the bottom of the groove of the accelerometer installation piston 7.

And after the assembly is finished, opening a valve of a compressed air bottle 11, releasing compressed air, monitoring the pressure of the high-pressure section 2 of the shock tube through an air pressure gauge 12, and releasing the compressed air through a pressure reducing valve 13 if the pressure exceeds a safety range. The compressed air pipeline is connected with the shock tube high-pressure section 2 through a gas connecting valve 14, after the gas pressure in the high-pressure section 2 reaches a specific value, the aluminum film 4 is broken, and shock waves are generated at the broken part of the film. After the pressure shock wave acts on the accelerometer mounting piston, the piston moves forwards in the accelerometer mounting cylinder 6 to generate a required acceleration excitation signal, so that the acceleration excitation process with controllable numerical value is completed, meanwhile, the accelerometer mounting piston 7 and the accelerometer 9 move forwards together, and the accelerometer 9 measures the acceleration signal at the moment. Signals measured by the accelerometer are collected and transmitted by the data acquisition card 10 and then stored in the data acquisition computer.

In this embodiment, a pressure shock wave of 100kPa is used to excite an accelerometer, and the calculation process of the excitation amplitude is as follows:

in order to increase the stress wave transmission speed and reduce the mass of the sensor and the mounting device, titanium alloy is adopted as an accelerometer mounting seat, the diameter of the bottom end of the accelerometer mounting seat is 5cm, the base and the sensing and mass are 244g, the base and a cylinder body are in clearance fit, and lubricating grease is adopted between the two parts for lubrication. And then calculating the acceleration values of the accelerometer mounting seat and the accelerometer after being excited by the shock wave by using the shock wave pressure of 100 kPa.

The shock wave exciting force applied to the accelerometer mounting seat is as follows:

F＝P×S＝10⁵×(2.5×10^-2)²×π＝196.25N

according to the relevant content in the mechanical design manual, the dynamic friction coefficient mu of the titanium alloy and the stainless steel under the condition of good lubrication is 0.1, and the friction force applied to the accelerometer mounting seat in the movement process is as follows:

f＝μ×mg＝0.1×0.244×9.8＝0.24N

the total force of the accelerometer mounting base after being excited is:

F_{combination of Chinese herbs}＝F-f＝196.25-0.24＝196.01N

The acceleration that the accelerometer and mount pad produced under the excitation of shock wave is:

meanwhile, due to the laser Doppler effect, the laser velocimeter 8 obtains an acceleration signal of the bottom end of the accelerometer mounting piston 7 in the movement process through measurement by an optical principle. The measurement signal is stored in the data acquisition computer via the data acquisition card 10. The sensitivity coefficient of the accelerometer to be calibrated is obtained by comparing the acceleration peak value and the waveform measured by the accelerometer 9 and the laser velocimeter 8 in the data acquisition computer, so that the accelerometer calibration process based on step acceleration excitation is completed.

The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.