CN114441801A - Acceleration sensor with double light path structure and noise-bottom self-calibration system and method - Google Patents
Acceleration sensor with double light path structure and noise-bottom self-calibration system and method Download PDFInfo
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- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
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Abstract
The invention provides an acceleration sensor with a double-light-path structure and a noise-floor self-calibration system and method; the acceleration sensor comprises an acceleration sensor chip, a double-path detection device, a PCB (printed circuit board) supporting plate and an acceleration sensor frame; the noise bottom self-calibration system comprises an acceleration sensor, a double-path laser driving module, a double-path IV conversion module, a synchronous acquisition module, a double-path cross-correlation module and an environmental background information extraction module; the output signals of the two-path displacement detection module collected by the synchronous collection module have completely same environmental noise signals and respectively different self-noise signals, the completely same environmental noise can be removed through a two-path cross-correlation algorithm, respectively different self-noise signals are obtained, and self-calibration of the Fabry-Perot acceleration sensor noise bottom is achieved.
Description
Technical Field
The invention belongs to the technical field of micro-nano sensors, and relates to an acceleration sensor with a double-optical-path structure, a noise-bottom self-calibration system and a noise-bottom self-calibration method.
Background
In recent years, with the development of MEMS technology, integrated optical MEMS acceleration sensors have attracted the attention of more and more researchers. The integrated optical MEMS acceleration sensor integrates MEMS sensitive chip, laser chip, photodiode and other elements in a miniature casing. Compared with an optical fiber type acceleration sensor, the integrated optical MEMS acceleration sensor solves the problems of high cost and large volume of the optical fiber MEMS acceleration sensor while ensuring high performance, and is widely applied to the fields of aerospace, gravity exploration, consumer electronics and the like.
In the field of gravity exploration, in order to detect weak gravity anomaly caused by small-scale objects, the detection resolution of a gravimeter is generally required to be 3 multiplied by 10 < -7 > m/s2. The resolution ratio of the existing integrated optical MEMS acceleration sensor is the ug level at most, and the distance meeting the gravity exploration requirement is difficult to meet. The ug-level acceleration sensor is not suitable for the gravity exploration industry because the background noise is too high to submerge the external gravity signal and cannot be identified. If a technology for searching the environmental signal from the noise signal is found, the development of the gravity exploration industry in China is facilitated. The output signal of the acceleration sensor comprises a self background noise signal and environment background noise, and if the background noise of the instrument can be solved, the environment background noise can be solved by subtracting the background signal from the output signal. The noise floor calibration of the acceleration sensor is generally performed by selecting a quiet wild cave, and the method has high cost and low calibration efficiency. Meanwhile, air in the cave is not circulated and is moist, so that the working state of the acceleration sensor is influenced, and the noise bottom calibration of the acceleration sensor is further influenced. Tangshihao et al place acceleration sensor and commercial acceleration sensor of higher precision in same environment and do relevant processing after measuring simultaneously[1]And then the noise floor of the acceleration sensor is obtained, but the high-precision commercial acceleration sensor required by the method is high in cost. Meanwhile, the type, the working bandwidth and the installation environment of the commercial acceleration sensor can influence the noise floor calibration level of the measured acceleration sensor. In addition, after the noise floor of the acceleration sensor is successfully calibrated, the calibration cannot be repeated again, however, in practical situations, due to the use environment or the aging of signal driving circuit devices and the like, the noise floor of the acceleration sensor also changes gradually, which directly affects the output signalThe background signal is subtracted from the calculated ambient background noise. In summary, if an attempt is made to search for an environmental signal from a noise signal output from an acceleration sensor, it is a primary prerequisite that the background noise of the acceleration sensor itself can be obtained in real time.
At present, the noise bottom calibration of the acceleration sensor is generally performed in a quiet cave or two sensors are used for calibration and are calibrated once, and no acceleration sensor with the noise bottom self-calibration function in real time exists. Therefore, the problem to be solved is to design an acceleration sensor structure with a noise-bottom real-time self-calibration function.
1.Tang S,Liu H,Yan S,Xu X,Wenjie W,Fan J,Liu J,Hu C and Tu L-C.Ahigh-sensitivity MEMS gravimeter with a large dynamic range.Microsystems&Nanoengineering,2019,5:1-11。
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an acceleration sensor with a double-light-path structure, a noise-bottom self-calibration system and a noise-bottom self-calibration method, so that the noise-bottom real-time self-calibration function of the acceleration sensor can be realized through the designed acceleration sensor with the double-light-path structure, and the self-noise-bottom of the acceleration sensor can be effectively obtained.
The invention is realized by the following technical scheme:
an acceleration sensor with a double-light-path structure comprises,
the system comprises an acceleration sensor chip, a two-way displacement detection device, a PCB (printed circuit board) supporting plate and an acceleration sensor frame; the acceleration sensor chip is arranged at the end part of the acceleration sensor frame; the two-way displacement detection device is arranged on the PCB supporting plate; the PCB supporting plate is fixed at the bottom of the acceleration sensor frame; the acceleration sensor chip is provided with a movable mirror and a fixed mirror; the movable mirror surface is arranged between the two fixed mirror surfaces, and the movable mirror surface and the fixed mirror surfaces are bonded together through an anode key; the two ends of the fixed mirror surface are connected with the acceleration sensor frame; the double-path displacement detection device comprises a first vertical cavity surface emitting laser, a first photodiode, a second vertical cavity surface emitting laser and a second photodiode; the first vertical cavity surface emitting laser and the second vertical cavity surface emitting laser are arranged on the inner side of the PCB supporting plate, and the first photodiode and the second photodiode are arranged on the outer side of the PCB supporting plate.
Preferably, the distance between the PCB support plate and the fixed mirror surface is H, and the distance between the first vertical cavity surface emitting laser and the second vertical cavity surface emitting laser is L; in order to ensure that the two output signals of the acceleration sensor are independent of each other, the parameter H, L and the divergence angle a of the vertical cavity surface emitting laser satisfy:
preferably, the movable mirror comprises one of a spring-mass movable mirror, a cantilever-mass movable mirror, and a membrane-mass movable mirror;
a noise-bottom self-calibration method for acceleration sensor with dual optical path structure includes,
s1, calibrating the self transfer function of the acceleration sensor;
s2, measuring the two-way output signal of the acceleration sensor and acquiring the numerical value of the two-way output signal;
and S3, calculating the background noise of the acceleration sensor by a cross-correlation method through the transfer function in S1 and the value of the two-way output signal in S2.
Preferably, in S1, a transfer function of the acceleration sensor itself is calibrated, and the specific method is as follows: setting two paths of laser-driven output currents, synchronously acquiring two paths of voltage-converted output measured signals x (t) and y (t), assembling an acceleration sensor on a vibration table, sweeping frequency, respectively measuring amplitude-frequency responses of the acceleration sensor under different frequencies, and calculating a double-light-path formulated transfer function H through the amplitude-frequency response of the acceleration sensor1And a transfer function H2。
Preferably, in S2, the method includes measuring a dual output signal of the acceleration sensor, and recording a value of the dual output signal, and includes: setting two paths of laser-driven output currents, synchronously acquiring two paths of voltage-converted output measured signals x (t) and y (t), placing an acceleration sensor in a quiet environment, and continuously recording at a sampling speed 2 times of natural frequency; and (4) sliding the data of the historical records to obtain a specific numerical value of the two-way output signal in real time by taking 10 days as a time interval.
Preferably, in S3, the background noise of the acceleration sensor is calculated by a cross-correlation method, which specifically includes: respectively calculating the self-noise power spectral density P of the measured signal x (t) and the measured signal y (t) by using a windowed average periodogram method through the recorded specific values of the two-way output signalsxxAnd self-noise power spectral density Pyy(ii) a Performing cross-correlation operation on the detected signal x (t) and the detected signal y (t), and performing Fourier transform to obtain cross-power spectral density Pxy(ii) a The obtained self-noise power spectral density PxxSum noise power spectral density PyyPower spectral density P of mutual noisexyAnd the resulting transfer function H1And a transfer function H2Substituting into formula, calculating to obtain background noise P of two paths of outputs of acceleration sensorNNAnd noise floor PMMTherefore, the self-calibration of the acceleration sensor noise bottom is realized, wherein the specific calculation formula is as follows:
preferably, the two paths of signals output by the acceleration sensor are based on the same sensitive unit, the transfer functions of the two paths of signals are the same, and a specific calculation formula of the background noise of the two paths of signals output by the acceleration sensor can be converted into:
wherein, PNNAnd PMMBackground noise, P, of both outputs of the acceleration sensorxxIs the self-noise power spectral density; pyyTo noise power spectral density, PxyIs the cross-power spectral density, H1Is a transfer function and H2Is a transfer function.
A noise-bottom self-calibration system of acceleration sensor with dual optical path structure comprises,
the system comprises an acceleration sensor, a two-way laser driving module, a two-way IV conversion module, a synchronous acquisition module, a two-way cross-correlation module and an environmental background information extraction module;
one end of the two-way laser driving module is connected with a first vertical cavity surface emitting laser of the acceleration sensor, and the other end of the two-way laser driving module is connected with a second vertical cavity surface emitting laser of the acceleration sensor; one path of the input end of the two-path IV conversion module is connected with a first photodiode of the acceleration sensor, the other path of the input end of the two-path IV conversion module is connected with a second photodiode of the acceleration sensor, the output end of the two-path IV conversion module is connected with the input end of the synchronous acquisition module, and the output end of the synchronous acquisition module is sequentially connected with the two-path cross-correlation module and the environment background information extraction module;
the two-way laser driving module is used for outputting laser driving current; the two-way IV conversion module is used for converting two-way output voltage; the synchronous acquisition module is used for acquiring output signals; the two-channel cross-correlation module is used for calculating the background noise of the acceleration sensor; the environment background information extraction module is used for extracting environment noise from the output signal of the acceleration sensor.
Preferably, the synchronous acquisition module adopts a synchronous digital-to-analog conversion chip or a combination of multiple digital-to-analog conversion chips; the two-way IV conversion module comprises an IV converter 1 and an IV converter 2; the two-way laser driving module comprises a laser driver 1 and a laser driver 2; the input of IV converter 1 with the first photodiode of acceleration sensor is connected, the output of IV converter 1 is connected with the input of synchronous acquisition module, the input of IV converter 2 with the second photodiode of acceleration sensor is connected, the output of IV converter 2 is connected with the input of synchronous acquisition module.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides an acceleration sensor with a double-light-path structure and a noise-bottom self-calibration system and method, so that the designed acceleration sensor with the double-light-path structure can realize the real-time self-calibration function of the noise bottom of the acceleration sensor, and can effectively acquire the self-noise bottom of the acceleration sensor. Meanwhile, two mutually unrelated measurement systems are integrated in the acceleration sensor with the double-light-path structure, and the two measurement systems measure the state of the same inertial unit, so that the types, the working bandwidths and the installation environments of the two sensing systems are the same, and the calibration of the noise bottom of the acceleration sensor is more favorably realized. In addition, the acceleration sensor with the double-light-path structure has two paths of mutually independent signal outputs, can execute a double-channel mutual correlation algorithm in real time, and can obtain the self noise floor of the sensor in real time. The noise-bottom self-calibration method has the advantages of reasonable design scheme, simple system structure, easy realization and full play of the advantages of the acceleration sensor.
Drawings
FIG. 1 is a schematic diagram of the acceleration sensor of the present invention;
FIG. 2 is a flow chart of a noise floor self-calibration method of the sensor of the present invention;
FIG. 3 is a flow chart of the noise floor self-calibration system of the sensor of the present invention;
wherein, 1, fixing the mirror surface; 2. a movable mirror surface; 3. an acceleration sensor frame; 4. a PCB supporting plate; 5. a first vertical cavity surface emitting laser; 6. a first photodiode; 7. a second vertical cavity surface emitting laser; 8. a second photodiode.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
The invention provides an acceleration sensor with a double light path structure and a noise bottom self-calibration system and a method;
an acceleration sensor with a dual optical path structure, as shown in fig. 1, includes,
the device comprises an acceleration sensor chip, a two-way displacement detection device, a PCB support plate 4 and an acceleration sensor frame 3; the acceleration sensor chip is arranged at the end of the acceleration sensor frame 3; the two-way displacement detection device is arranged on the PCB supporting plate 4; the PCB supporting plate 4 is fixed at the bottom of the acceleration sensor frame 3; the acceleration sensor chip is provided with a movable mirror surface 2 and a fixed mirror surface 1; the movable mirror surface 2 is arranged between the two fixed mirror surfaces 1, and two ends of each fixed mirror surface 1 are connected with the acceleration sensor frame 3; the two-way displacement detection device comprises a first vertical cavity surface emitting laser 5, a first photodiode 6, a second vertical cavity surface emitting laser 7 and a second photodiode 8; the first vertical cavity surface emitting laser 5 and the second vertical cavity surface emitting laser 7 are disposed inside the PCB support plate 4, and the first photodiode 6 and the second photodiode 8 are disposed outside the PCB support plate 4. The double-path detection module and the acceleration sensor chip are packaged in an integrated mode, wherein the double-path detection module is independent from each other and consistent in working environment;
the distance between the PCB supporting plate 4 and the fixed mirror surface 1 is H, and the distance between the first vertical cavity surface emitting laser 5 and the second vertical cavity surface emitting laser 7 is L; in order to ensure that the two output signals of the acceleration sensor 9 are independent of each other, the parameter H, L and the divergence angle a of the vertical cavity surface emitting laser satisfy:
the movable mirror 2 comprises one of a spring-mass movable mirror, a cantilever-mass movable mirror and a membrane-mass movable mirror; the double-path displacement detection device of the acceleration sensor, which is provided by the invention, can be a piezoresistive acceleration sensor, a piezoelectric acceleration sensor and a resonant acceleration sensor which are based on a double-path piezoresistive detection device, a double-path piezoelectric detection device, a double-path resonant detection device and the like, besides an optical-based Fabry-Perot acceleration sensor. The same between different types of acceleration sensors is that the two-way detection modules are independent from each other and have consistent working environment.
A noise-bottom self-calibration method for an acceleration sensor with a dual-optical-path structure is shown in FIG. 2, and comprises,
s1, calibrating the self transfer function of the acceleration sensor;
s2, measuring the two-way output signal of the acceleration sensor and acquiring the numerical value of the two-way output signal;
and S3, calculating the background noise of the acceleration sensor by a cross-correlation method through the transfer function in S1 and the value of the two-way output signal in S2.
In S1, a transfer function of the acceleration sensor itself is calibrated, and the specific method is as follows: setting two paths of laser-driven output currents to be 8mA respectively, synchronously collecting two paths of converted output voltages, assembling an acceleration sensor on a vibration table, sweeping frequency, measuring amplitude-frequency responses of the acceleration sensor under different frequencies respectively, and calculating a double-light-path formulated transfer function H through the amplitude-frequency response of the acceleration sensor1And a transfer function H2。
In the step S2, a two-way output signal of the acceleration sensor is measured, and a value of the two-way output signal is recorded, and the specific method includes: setting output currents of two laser drives to be 8mA respectively, synchronously acquiring two tested signals x (t) and y (t) output after voltage conversion, placing the acceleration sensor in a quiet environment, and continuously sampling at a sampling speed 2 times of the inherent frequency; and (4) sliding the data of the historical records to obtain a specific numerical value of the two-way output signal in real time by taking 10 days as a time interval.
The noise floor of the acceleration sensor is calculated by the cross-correlation method in S3,the specific method comprises the following steps: respectively calculating the self-noise power spectral density P of the measured signal x (t) and the measured signal y (t) by using a windowed average periodogram method through the recorded specific values of the two-way output signalsxxAnd self-noise power spectral density Pyy(ii) a Performing cross-correlation operation on the detected signal x (t) and the detected signal y (t), and performing Fourier transform to obtain cross-power spectral density Pxy(ii) a The obtained self-noise power spectral density PxxSum noise power spectral density PyyPower spectral density P of mutual noisexyAnd the resulting transfer function H1And a transfer function H2Substituting into formula, calculating to obtain background noise P of two paths of outputs of acceleration sensorNNAnd noise floor PMMTherefore, the self-calibration of the acceleration sensor noise bottom is realized, wherein the specific calculation formula is as follows:
two paths of signal output of the acceleration sensor are based on the same sensitive unit, the transfer functions of the two paths of signals are the same, and the specific calculation formula of the background noise of the two paths of output of the acceleration sensor can be converted into:
wherein, PNNAnd PMMBackground noise, P, of both outputs of the acceleration sensorxxIs the self-noise power spectral density; pyyTo noise power spectral density, PxyIs the cross-power spectral density, H1Is a transfer function and H2Is a transfer function.
A noise-floor self-calibration system of an acceleration sensor with a dual-optical-path structure is shown in FIG. 3, which comprises,
the system comprises an acceleration sensor, a two-way laser driving module, a two-way IV conversion module, a synchronous acquisition module, a two-way cross-correlation module and an environmental background information extraction module;
one end of the two-way laser driving module is connected with a first vertical cavity surface emitting laser 5 of the acceleration sensor, and the other end of the two-way laser driving module is connected with a second vertical cavity surface emitting laser 7 of the acceleration sensor; one path of the input end of the two-path IV conversion module is connected with a first photodiode 6 of the acceleration sensor, the other path of the input end of the two-path IV conversion module is connected with a second photodiode 8 of the acceleration sensor, the output end of the two-path IV conversion module is connected with the input end of the synchronous acquisition module, and the output end of the synchronous acquisition module is sequentially connected with the two-path cross-correlation module and the environment background information extraction module;
the two-way laser driving module is used for outputting laser driving current; the two-way IV conversion module is used for converting two-way output voltage; the synchronous acquisition module is used for acquiring output signals; the two-channel cross-correlation module is used for calculating the background noise of the acceleration sensor; the environment background information extraction module is used for extracting environment noise from the output signal of the acceleration sensor.
The two-path laser driving module consists of two sets of laser drivers ITC102 with the same model, and the two laser drivers output the same laser driving current to act on the first vertical cavity surface emitting laser and the second vertical cavity surface emitting laser respectively. The IV converter consists of an operational amplifier and an amplifying resistor, and the photoelectric current emitted by the first photodiode and the second photodiode is converted into voltage after passing through the IV converter A and the IV converter B, and then is synchronously acquired by the synchronous acquisition module. The synchronous acquisition module can be composed of a synchronous digital-to-analog conversion chip or a multi-path digital-to-analog conversion chip. The acceleration signals after synchronous acquisition are processed by a double-channel cross-correlation module to calculate the self noise bottom of the acceleration sensor, and then the environmental background information extraction module is used for extracting environmental noise from the output signals of the acceleration sensor.
The synchronous acquisition module adopts a synchronous digital-to-analog conversion chip or a multi-path digital-to-analog conversion chip combination; the two-way IV conversion module comprises an IV converter 1 and an IV converter 2; the two-way laser driving module comprises a laser driver 1 and a laser driver 2; the input of IV converter 1 with acceleration sensor's first photodiode 6 is connected, the output of IV converter 1 is connected with synchronous acquisition module's input, the input of IV converter 2 with acceleration sensor's second photodiode 8 is connected, the output of IV converter 2 is connected with synchronous acquisition module's input.
The two-path displacement monitoring module is formed by two sets of optical path systems, after the two sets of optical path systems are reasonably arranged, the two sets of optical paths are mutually independent and have the same working environment, and the two sets of optical paths respectively demodulate the cavity length information of the acceleration sensor chip. The output signals of the two paths of displacement detection modules acquired by the synchronous acquisition module have completely same environmental noise signals and respectively different self-noise signals, and because the environmental noises are consistent, the completely same environmental noises can be removed by using a two-channel cross-correlation algorithm, respectively different self-noise power spectrum signals of the two paths of displacement detection modules are obtained, and the self-calibration of the noise bottom of the acceleration sensor is realized. The signal output of a single path in the two-path displacement detection module comprises an environmental noise signal and a self-noise signal of the sensor, so that the power spectrum of the environmental noise signal can be obtained by subtracting the self-noise signal of the sensor from the power spectrum of the output signal.
The following embodiments of the present invention are provided, and it should be noted that the present invention is not limited to the following embodiments, and all equivalent changes based on the technical solutions of the present invention are within the protection scope of the present invention.
The invention adopts a preferred embodiment, and adopts a Fabry-Perot acceleration sensor and a double-path displacement detection device as preferred embodiment modes;
the Fabry-Perot acceleration sensor comprises a Fabry-Perot sensitive chip, a double-path displacement detection device, a PCB supporting plate 4 and a Fabry-Perot sensor frame 3. The Fabry-Perot MEMS sensitive chip consists of a spring-mass block movable mirror surface and a fixed mirror surface 1 which are bonded together through anodic bonding. The two-way displacement detection device is composed of a first vertical cavity surface emitting laser 5, a first photodiode 6, a second vertical cavity surface emitting laser 7 and a second photodiode 8. The first vertical cavity surface emitting laser 5, the first photodiode 6, the second vertical cavity surface emitting laser 7, and the second photodiode 8 are soldered on the PCB support plate 4, the lasers are located at the inner side, and the photodiodes are located at the outer side. The PCB supporting plate 4 is fixed at the bottom of the Fabry-Perot sensor frame 3, and the Fabry-Perot MEMS sensitive chip is fixed at the end of the Fabry-Perot sensor frame 3. The distance between the PCB supporting plate 4 and the fixed mirror surface 1 is H, and the distance between the lasers on the PCB is L. In order to ensure that the two output signals of the acceleration sensor are independent of each other, the parameter H, L and the divergence angle a of the vertical cavity surface emitting laser satisfy:
the Fabry-Perot acceleration sensor noise bottom self-labeling system is composed of a Fabry-Perot acceleration sensor, a double-path laser driving system, a double-path IV conversion module, a synchronous acquisition module, a double-path cross-correlation module and an environment background information extraction module.
The two-path laser driving module consists of two sets of laser drivers ITC102 with the same model, and the two laser drivers output the same laser driving current 8mA which respectively acts on the first vertical cavity surface emitting laser 5 and the second vertical cavity surface emitting laser 7. The two-way IV conversion module consists of an operational amplifier and an amplifying resistor, and the photoelectric currents sent by the first photodiode 6 and the second photodiode 8 are converted into voltages after passing through the IV converter 1 and the IV converter 2 and then are synchronously acquired by the synchronous acquisition module. The acceleration signals after synchronous acquisition are processed by a double-channel cross-correlation module to calculate the self noise bottom of the acceleration sensor, and then the environmental background information extraction module is used for extracting environmental noise from the output signals of the acceleration sensor. The two-way laser driving module comprises a laser driver 1 and a laser driver 2.
The working process of the invention is as follows:
a self-calibration technology of the background noise of a Fabry-Perot acceleration sensor based on a cross-correlation principle comprises the steps of calibration of a transfer function, measurement of double-path output signals of the acceleration sensor and calculation of the background noise of the acceleration sensor.
Transfer function calibration
The step of calibrating the transfer function of the acceleration sensor comprises the following three steps:
1) the output current of the laser driver 2 of the laser driver 1 is set to 8mA, and the output voltages of the IV converter 1 and the IV converter 2 are acquired by using a synchronous acquisition module.
2) And (3) assembling the Fabry-Perot acceleration sensor on a vibration table, then sweeping frequency, and respectively measuring the amplitude-frequency response of the Fabry-Perot acceleration sensor under different frequencies.
3) Solving two paths of formulated transfer functions H according to the amplitude-frequency response of the Fabry-Perot acceleration sensor1And H2。
The influence of environment or time on the noise floor of the Fabry-Perot acceleration sensor is mainly generated by influencing the output light intensity noise of the laser, and the influence of an electronic device on the noise floor of the Fabry-Perot acceleration sensor can be ignored. The transfer function calculated by the transfer function calibration process is the relation from an external acceleration signal to a voltage signal output by an IV converter, and the internal coefficient of the transfer function is not influenced by a laser, so that the transfer function calibrated by the process is a fixed value, can be directly used when the background noise of the sensor is calibrated in real time at a later stage, and does not need to be calibrated repeatedly.
Two-way output signal of acceleration sensor
The step of recording the double-path output signals of the Fabry-Perot acceleration sensor mainly comprises the following two steps:
1) the output currents of the laser driver 1 and the laser driver 2 are set to be 8mA respectively, and the measured signals x (t) and y (t) of the voltage outputs of the IV converter 1 and the IV converter 2 are synchronously acquired by using a synchronous acquisition module.
2) The Fabry-Perot acceleration sensor calibration system is placed in a quiet environment of a laboratory and continuously records at a sampling speed which is 2 times of the natural frequency.
In an actual operation environment, the Fabry-Perot acceleration sensor can be in a working state all the time, and output data are recorded and stored. And (3) taking 10 days as a time interval to carry out sliding value taking on the data of the historical records, carrying out cross-correlation operation on the taken values, and solving the background noise of the Fabry-Perot acceleration sensor.
Thirdly, calculating the background noise of the acceleration sensor
The noise bottom of the Fabry-Perot acceleration sensor is calculated through a cross-correlation algorithm, and the method mainly comprises the following 3 steps:
1) respectively calculating the self-noise power spectral density P of the detected signals x (t) and y (t) by using a windowed average periodogram methodxxAnd Pyy。
2) Performing cross correlation on the detected signals x (t) and y (t), and performing Fourier transform to obtain cross-power spectral density Pxy。
3) Self-noise power spectral density PxxAnd PyyPower spectral density P of mutual noisexyAnd a transfer function H1And H2Substituting the formula to obtain the background noise P of two paths of outputs of the Fabry-Perot acceleration sensorNNAnd PMM。
Because two paths of outputs of the Fabry-Perot acceleration sensor are based on the same sensitive unit, the transfer functions of two paths of signals are the same, namely the formula is converted into:
the above is a flow of self-calibration of the noise floor of the fabry acceleration sensor, and if the background noise of the acceleration sensor is to be measured in real time, the above steps two and three are only required to be executed circularly. After the background noise of the Fabry-Perot acceleration sensor is solved, the noise bottom of the acceleration sensor is subtracted from the signal output by the Fabry-Perot acceleration sensor to obtain the environment background noise.
Claims (10)
1. An acceleration sensor with a double-light-path structure is characterized by comprising,
the device comprises an acceleration sensor chip, a two-way displacement detection device, a PCB supporting plate (4) and an acceleration sensor frame (3); the acceleration sensor chip is arranged at the end part of the acceleration sensor frame (3); the two-way displacement detection device is arranged on the PCB supporting plate (4); the PCB supporting plate (4) is fixed at the bottom of the acceleration sensor frame (3); the acceleration sensor chip comprises a movable mirror surface (2) and a fixed mirror surface (1); the movable mirror surface (2) is arranged between the two fixed mirror surfaces (1), and the movable mirror surface (2) and the fixed mirror surfaces (1) are bonded together through an anode key; the two ends of the fixed mirror surface (1) are connected with the acceleration sensor frame (3); the double-path displacement detection device comprises a first vertical cavity surface emitting laser (5), a first photodiode (6), a second vertical cavity surface emitting laser (7) and a second photodiode (8); the first vertical cavity surface emitting laser (5) and the second vertical cavity surface emitting laser (7) are arranged on the inner side of the PCB supporting plate (4), and the first photodiode (6) and the second photodiode (8) are arranged on the outer side of the PCB supporting plate (4).
2. The acceleration sensor of a dual optical path structure according to claim 1, wherein the distance between the PCB support plate (4) and the fixed mirror (1) is H, and the distance between the first vertical cavity surface emitting laser (5) and the second vertical cavity surface emitting laser (7) is L; in order to ensure that two output signals of the acceleration sensor (9) are independent of each other, the parameter H, L and the vertical cavity surface emitting laser divergence angle a satisfy the following condition:
3. the acceleration sensor of a dual optical path structure according to claim 1, wherein said movable mirror (2) comprises one of a spring-mass movable mirror, a cantilever-mass movable mirror and a membrane-mass movable mirror.
4. A noise floor self-calibration method of an acceleration sensor with a dual optical path structure, which is based on the acceleration sensor with a dual optical path structure of any one of claims 1 to 3, comprises,
s1, calibrating the self transfer function of the acceleration sensor;
s2, measuring the two-way output signal of the acceleration sensor and recording the numerical value of the two-way output signal;
and S3, calculating the background noise of the acceleration sensor by a cross-correlation method through the transfer function in S1 and the value of the two-way output signal in S2.
5. The noise floor self-calibration method of the acceleration sensor with the dual optical path structure as claimed in claim 4, wherein the transfer function of the acceleration sensor itself is calibrated in S1 by: setting two paths of laser-driven output currents, collecting two paths of measured signals x (t) and y (t) output after voltage conversion, assembling an acceleration sensor on a vibration table, sweeping frequency, respectively measuring amplitude-frequency responses of the acceleration sensor under different frequencies, and respectively measuring the amplitude-frequency responses of the acceleration sensor through the amplitude-frequency responses of the acceleration sensorCalculating the transfer function H of the double light path formulation1And a transfer function H2。
6. The noise floor self-calibration method of the acceleration sensor with the dual optical path structure as claimed in claim 5, wherein the dual output signal of the acceleration sensor is measured in S2, and the value of the dual output signal is recorded, and the specific method is as follows: setting two paths of laser-driven output currents, synchronously acquiring two paths of measured signals x (t) and y (t) output after voltage conversion, placing an acceleration sensor in a quiet environment, and continuously recording at a sampling speed 2 times of natural frequency; and (4) sliding the data of the historical records to obtain a specific numerical value of the two-way output signal in real time by taking 10 days as a time interval.
7. The noise-floor self-calibration method of the acceleration sensor with the dual optical path structure according to claim 6, wherein the noise floor of the acceleration sensor is calculated by a cross-correlation method in S3, and the method specifically comprises: respectively calculating the self-noise power spectral density P of the measured signal x (t) and the measured signal y (t) by using a windowed average periodogram method through the recorded specific values of the two-way output signalsxxAnd self-noise power spectral density Pyy(ii) a Performing cross-correlation operation on the detected signal x (t) and the detected signal y (t), and performing Fourier transform to obtain cross-power spectral density Pxy(ii) a The obtained self-noise power spectral density PxxAnd noise power spectral density PyyPower spectral density P of mutual noisexyAnd the resulting transfer function H1And a transfer function H2Substituting the two paths of output background noise P of the acceleration sensor into the following formulaNNAnd noise floor PMMTherefore, the self-calibration of the acceleration sensor noise bottom is realized, wherein the specific calculation formula is as follows:
8. the noise floor self-calibration method of the acceleration sensor with the dual-optical-path structure according to claim 7, wherein the two signal outputs of the acceleration sensor are based on the same sensitive unit, the transfer functions of the two signals are the same, and the specific calculation formula of the noise floor of the two signal outputs of the acceleration sensor can be converted into:
9. a noise floor self-calibration system of an acceleration sensor with a dual optical path structure, which is based on the acceleration sensor with a dual optical path structure of any one of claims 1 to 3, comprising,
the system comprises an acceleration sensor, a two-way laser driving module, a two-way IV conversion module, a synchronous acquisition module, a two-way cross-correlation module and an environmental background information extraction module;
one end of the two-way laser driving module is connected with a first vertical cavity surface emitting laser (5) of the acceleration sensor, and the other end of the two-way laser driving module is connected with a second vertical cavity surface emitting laser (7) of the acceleration sensor; one path of the input end of the two-path IV conversion module is connected with a first photodiode (6) of the acceleration sensor, the other path of the input end of the two-path IV conversion module is connected with a second photodiode (8) of the acceleration sensor, the output end of the two-path IV conversion module is connected with the input end of the synchronous acquisition module, and the output end of the synchronous acquisition module is sequentially connected with the two-path cross-correlation module and the environment background information extraction module;
the two-way laser driving module is used for outputting laser driving current; the two-way IV conversion module is used for converting two-way output voltage; the synchronous acquisition module is used for acquiring output signals; the two-channel cross-correlation module is used for calculating the background noise of the acceleration sensor; the environment background information extraction module is used for extracting environment noise from the output signal of the acceleration sensor.
10. The noise floor self-calibration system of the acceleration sensor with the dual optical path structure as claimed in claim 9, wherein the synchronous acquisition module employs a synchronous digital-to-analog conversion chip or a combination of multiple digital-to-analog conversion chips; the two-way IV conversion module comprises an IV converter 1 and an IV converter 2; the two-way laser driving module comprises a laser driver 1 and a laser driver 2; the input of IV converter 1 with acceleration sensor's first photodiode (6) are connected, the output of IV converter 1 is connected with synchronous acquisition module's input, the input of IV converter 2 with acceleration sensor's second photodiode (8) are connected, the output of IV converter 2 is connected with synchronous acquisition module's input.
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