CA3080201C - Device and method for testing background noise of high precision acceleration sensor - Google Patents
Device and method for testing background noise of high precision acceleration sensor Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
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Abstract
A device for testing background noise of an acceleration sensor comprises a vibration isolation device and a vibration damping system. The vibration isolation device comprises a silencing chamber and a vibration isolation table comprising an air-floating vibration isolation table and a multi-stage elastic vibration isolation table. A rotating base is installed on the ground of the silencing chamber; the air-floating vibration isolation table is arranged on the rotating base; and the multi-stage elastic vibration isolation table is arranged above the air- floating vibration isolation table after being connected in series. The tested acceleration sensor is arranged on a surface of a bearing vibration isolation table which is on an uppermost part of the multi- stage elastic vibration isolation table. The vibration damping system comprises a standard sensor group, a signal detection and conditioning unit, an acquisition unit, a control unit and a driver. A testing method using the device is also provided.
Description
DEVICE AND METHOD FOR TESTING BACKGROUND NOISE OF HIGH
PRECISION ACCELERATION SENSOR
Technical Field The invention relates to the technical field of sensor detection, in particular to a device and a method for testing background noise of a high precision acceleration sensor.
Background Art The acceleration sensor is an inertial sensor for measuring acceleration of an external input. In general, after the acceleration sensor is designed, the background noise of the sensor is required to be tested to judge whether the background noise meets design requirements. However, due to the fact that the acceleration sensor is very sensitive to external environment noise, external vibration, angular motion, linear motion and the like can be coupled into input acceleration, so that other noise is mixed in a test result of background noise, and it is difficult to obtain the background noise of the acceleration sensor accurately. Especially for a high-precision acceleration sensor with extremely low background noise, the background noise in a common noise test environment is already higher than that of the tested high-precision acceleration sensor, so that the test result of the background noise of the acceleration sensor is completely submerged in the environment noise. Therefore, a basic requirement for the sensor noise test is that the background noise of the environment is lower than that of the tested acceleration sensor.
According to a traditional method for reducing environmental background noise, a wild cave or a basement of a building is generally selected for noise testing, but with the problems of low experimental efficiency and high cost for the method; or a vibration isolation table is adopted in an urban building, which can only isolate the vibration perpendicular to the ground direction; and the vibration of the building is multi-degree-of-freedom noise, including horizontal vibration, torsional pendulum vibration and the like besides the vibration in the vertical direction, so that the environmental background noise which can be reduced by the mode is limited, and the building noise except that in the perpendicular direction cannot be isolated.
Therefore, the Date Recue/Date Received 2020-04-30 background noise of the environment cannot meet the requirements of the noise test for the high-precision acceleration sensor.
In addition, a filter cannot be used for filtering some interferences in a frequency range of the background noise of the tested sensor, affecting a test result of the background noise of the tested sensor.
Therefore, it is required to solve a problem of how to establish a noise test environment suitable for the high-precision acceleration sensor, and that the test results are not affected by interference signals in a specific frequency range.
Summary of the Invention In order to achieve the above object, one aspect of the present invention provides a device for testing background noise of a high precision acceleration sensor, comprising a vibration isolation device and a vibration damping system, wherein the vibration isolation device comprises a silencing chamber and a vibration isolation table, the vibration isolation table comprises an air-floating vibration isolation table and a multi-stage elastic vibration isolation table;
the silencing chamber is internally provided with an accommodating space;
a rotating base is installed on the ground of the silencing chamber, the rotating base can rotate unifoimly at a determined angular velocity;
the air-floating vibration isolation table is arranged on the rotating base of the silencing chamber and can rotate along with the rotating base.;
and the multi-stage elastic vibration isolation table is arranged above the air-floating vibration isolation table after being connected in series;
the tested acceleration sensor is arranged on a surface of a bearing vibration isolation table which is located on an uppermost part of the multi-stage elastic vibration isolation table;
the vibration damping system comprises a standard sensor group, a signal detection and conditioning unit, an acquisition unit, a control unit, a driver and a noise processing unit.
PRECISION ACCELERATION SENSOR
Technical Field The invention relates to the technical field of sensor detection, in particular to a device and a method for testing background noise of a high precision acceleration sensor.
Background Art The acceleration sensor is an inertial sensor for measuring acceleration of an external input. In general, after the acceleration sensor is designed, the background noise of the sensor is required to be tested to judge whether the background noise meets design requirements. However, due to the fact that the acceleration sensor is very sensitive to external environment noise, external vibration, angular motion, linear motion and the like can be coupled into input acceleration, so that other noise is mixed in a test result of background noise, and it is difficult to obtain the background noise of the acceleration sensor accurately. Especially for a high-precision acceleration sensor with extremely low background noise, the background noise in a common noise test environment is already higher than that of the tested high-precision acceleration sensor, so that the test result of the background noise of the acceleration sensor is completely submerged in the environment noise. Therefore, a basic requirement for the sensor noise test is that the background noise of the environment is lower than that of the tested acceleration sensor.
According to a traditional method for reducing environmental background noise, a wild cave or a basement of a building is generally selected for noise testing, but with the problems of low experimental efficiency and high cost for the method; or a vibration isolation table is adopted in an urban building, which can only isolate the vibration perpendicular to the ground direction; and the vibration of the building is multi-degree-of-freedom noise, including horizontal vibration, torsional pendulum vibration and the like besides the vibration in the vertical direction, so that the environmental background noise which can be reduced by the mode is limited, and the building noise except that in the perpendicular direction cannot be isolated.
Therefore, the Date Recue/Date Received 2020-04-30 background noise of the environment cannot meet the requirements of the noise test for the high-precision acceleration sensor.
In addition, a filter cannot be used for filtering some interferences in a frequency range of the background noise of the tested sensor, affecting a test result of the background noise of the tested sensor.
Therefore, it is required to solve a problem of how to establish a noise test environment suitable for the high-precision acceleration sensor, and that the test results are not affected by interference signals in a specific frequency range.
Summary of the Invention In order to achieve the above object, one aspect of the present invention provides a device for testing background noise of a high precision acceleration sensor, comprising a vibration isolation device and a vibration damping system, wherein the vibration isolation device comprises a silencing chamber and a vibration isolation table, the vibration isolation table comprises an air-floating vibration isolation table and a multi-stage elastic vibration isolation table;
the silencing chamber is internally provided with an accommodating space;
a rotating base is installed on the ground of the silencing chamber, the rotating base can rotate unifoimly at a determined angular velocity;
the air-floating vibration isolation table is arranged on the rotating base of the silencing chamber and can rotate along with the rotating base.;
and the multi-stage elastic vibration isolation table is arranged above the air-floating vibration isolation table after being connected in series;
the tested acceleration sensor is arranged on a surface of a bearing vibration isolation table which is located on an uppermost part of the multi-stage elastic vibration isolation table;
the vibration damping system comprises a standard sensor group, a signal detection and conditioning unit, an acquisition unit, a control unit, a driver and a noise processing unit.
2 Date Recue/Date Received 2020-04-30 Further, the air-floating vibration isolation table comprises an air-floating table surface and at least one first-stage supporting leg, the first-stage supporting leg being arranged between the floor of the silencing chamber and the air-floating table surface.
Further, the multi-stage elastic vibration isolation table comprises a plurality of supporting tables and elastic supporting legs, the elastic supporting legs are arranged between the supporting tables, and the elastic supporting legs of the elastic vibration isolation table at a bottommost layer are arranged between the air-floating vibration isolation table and the supporting table at the bottommost layer.
Further, an inflation pump is arranged to inflate the air-floating vibration isolation table.
Further, the silencing chamber has a shockproof frame type of main body structure, and size parameters are as follows: the width is 1-2 meters, the depth is 2-4 meters, and the height is 1-3 meters.
Further, the vibration isolation table comprises one air-floating vibration isolation table and two elastic vibration isolation tables.
Further, the standard sensor group comprises a sensor for measuring a change in acceleration of the vibration isolation table, a sensor for measuring a change in angular velocity of the vibration isolation table, and a displacement sensor.
Further, the driver adjusts the vibration isolation table to perform a reverse motion according to the data detected by the standard sensor group, thereby further attenuating vibration of the vibration isolation table.
A test method based on the device for testing the acceleration background noise, characterized by comprising:
step 1, installing an acceleration sensor to be tested;
step 2, adjusting parameters of the vibration isolation table according to the mass of the acceleration sensor to be tested;
step 3, starting the vibration damping system step 4, starting the rotating base to drive the vibration isolation table to rotate;
Further, the multi-stage elastic vibration isolation table comprises a plurality of supporting tables and elastic supporting legs, the elastic supporting legs are arranged between the supporting tables, and the elastic supporting legs of the elastic vibration isolation table at a bottommost layer are arranged between the air-floating vibration isolation table and the supporting table at the bottommost layer.
Further, an inflation pump is arranged to inflate the air-floating vibration isolation table.
Further, the silencing chamber has a shockproof frame type of main body structure, and size parameters are as follows: the width is 1-2 meters, the depth is 2-4 meters, and the height is 1-3 meters.
Further, the vibration isolation table comprises one air-floating vibration isolation table and two elastic vibration isolation tables.
Further, the standard sensor group comprises a sensor for measuring a change in acceleration of the vibration isolation table, a sensor for measuring a change in angular velocity of the vibration isolation table, and a displacement sensor.
Further, the driver adjusts the vibration isolation table to perform a reverse motion according to the data detected by the standard sensor group, thereby further attenuating vibration of the vibration isolation table.
A test method based on the device for testing the acceleration background noise, characterized by comprising:
step 1, installing an acceleration sensor to be tested;
step 2, adjusting parameters of the vibration isolation table according to the mass of the acceleration sensor to be tested;
step 3, starting the vibration damping system step 4, starting the rotating base to drive the vibration isolation table to rotate;
3 Date Recue/Date Received 2021-08-05 step 5, enabling that a sensitive axis of the acceleration sensor to be tested is parallel to the Z axis, and sequentially testing the background noise in a direction of +1g and a direction of -1g;
step 6, enabling that the sensitive axis of the acceleration sensor to be tested is parallel to the X axis or the Y axis, and testing the background noise in the direction of Og; and step 7, obtaining an output of the tested acceleration sensor suppressing external interference by calculating a cross-correlation signal.
Further, in the test method, the rotating frequency of the rotating base is 1-10Hz.
According to the invention, the affection of environmental noise on the background noise test process of the acceleration sensor can be reduced under a condition of poor environment, so that the measured background noise of the acceleration sensor is closer to a true value.
Brief Description of the Drawings Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for the purpose of illustrating preferred embodiments and are not to be construed as limiting the invention. Also, throughout the drawings, like reference numerals designate like parts. In the drawings:
Fig. 1 is a view illustrating a silencing chamber structure according to an embodiment of the present invention;
Fig. 2 is a device for testing background noise of an acceleration sensor according to an embodiment of the present invention;
Fig. 3 is a schematic diagram of a mechanical model of a three-stage vibration isolation table according to an embodiment of the present invention;
Fig. 4 is a block diagram of a damping system for testing background noise of an acceleration sensor according to an embodiment of the present invention;
step 6, enabling that the sensitive axis of the acceleration sensor to be tested is parallel to the X axis or the Y axis, and testing the background noise in the direction of Og; and step 7, obtaining an output of the tested acceleration sensor suppressing external interference by calculating a cross-correlation signal.
Further, in the test method, the rotating frequency of the rotating base is 1-10Hz.
According to the invention, the affection of environmental noise on the background noise test process of the acceleration sensor can be reduced under a condition of poor environment, so that the measured background noise of the acceleration sensor is closer to a true value.
Brief Description of the Drawings Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for the purpose of illustrating preferred embodiments and are not to be construed as limiting the invention. Also, throughout the drawings, like reference numerals designate like parts. In the drawings:
Fig. 1 is a view illustrating a silencing chamber structure according to an embodiment of the present invention;
Fig. 2 is a device for testing background noise of an acceleration sensor according to an embodiment of the present invention;
Fig. 3 is a schematic diagram of a mechanical model of a three-stage vibration isolation table according to an embodiment of the present invention;
Fig. 4 is a block diagram of a damping system for testing background noise of an acceleration sensor according to an embodiment of the present invention;
4 Date Recue/Date Received 2021-08-05 Fig. 5 is a schematic view illustrating a mounting manner of a standard sensor group according to an embodiment of the present invention;
Fig. 6 is a block diagram of a signal detection and conditioning unit according to an embodiment of the present invention;
Fig. 7 is a block diagram of a control unit according to an embodiment of the present invention;
Fig. 8 is a result of testing a high-precision acceleration sensor according to an embodiment of the present invention;
Fig. 9 is a result of testing a higher-precision acceleration sensor according to an embodiment of the present invention.
Detailed Description of the Invention In order to solve the problem in the prior art, the invention provides a device and a method for testing background noise of a high precision acceleration sensor, which can reduce the affection of environmental noise on the background noise testing process of the acceleration sensor under a condition of poor environment, so that the measured background noise of the acceleration sensor is closer to a true value, and is more suitable for being practical.
In order to further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purposes of the present invention, the device and method for testing the background noise of the acceleration sensor according to the present invention, as well as the specific embodiments, structures, characteristics and effects thereof, will be described in detail with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "the embodiment" means not necessarily the same embodiment. Furthermore, the features, structures, or characteristics of one or more embodiments may be combined in any suitable form.
The term "and/or", as used herein, is merely an association that describes associated Date Recue/Date Received 2020-04-30 objects, meaning that there may be three relationships, e.g., A and/or B, which can be specifically understood as that A and B may be included together, A may be present alone or B may be present alone, and any of the above three cases may be provided.
An embodiment of the invention provides a device for testing background noise of an acceleration sensor, comprising a vibration isolation device and a vibration damping system.
Among them, the vibration isolation device comprises a silencing chamber and a vibration isolation table, wherein the vibration isolation table comprises an air-floating vibration isolation table and a multi-stage elastic vibration isolation table.
The silencing chamber is internally provided with an accommodating space.
In an embodiment of the invention, a rotating base is installed on the ground of the silencing chamber, the rotating base can rotate unifoitaly at a determined angular velocity.
The air-floating vibration isolation table is arranged on the rotating base of the silencing chamber and can rotate along with the rotating base, and the multi-stage elastic vibration isolation table is arranged above the air-floating vibration isolation table after being connected in series. Furthermore, an inflation pump is arranged to inflate the air-floating vibration isolation table, and the tested acceleration sensor is arranged on a surface of a bearing vibration isolation table which is located at an uppermost part of the multi-stage elastic vibration isolation table.
Furthermore, since testing environment and the sensor to be tested are different each time, the inflation pump is arranged to inflate the air-floating vibration isolation table; and the inflation pump is provided with an air pressure meter, the air pressure of the air-floating vibration isolation table can be set by the inflation pump provided with the air pressure meter, and transfer function parameters of vibration can be adjusted by adjusting the air pressure according to different testing environment.
The air-floating vibration isolation table comprises an air-floating table surface and at least one first-stage supporting leg. The first-stage supporting leg is arranged between the floor of the silencing chamber and the air-floating table surface. The multi-stage elastic Date Recue/Date Received 2020-04-30 vibration isolation table comprises a plurality of supporting tables and elastic supporting legs, the elastic supporting legs are arranged between the supporting tables, and the elastic supporting legs of the elastic vibration isolation table at a bottommost layer are arranged between the air-floating vibration isolation table and the supporting table at the bottommost layer.
The device for testing the background noise of the acceleration sensor further comprises a level gauge. The level gauge is used for leveling the surface of the multi-stage elastic vibration isolation table.
According to an embodiment of the invention, the silencing chamber is built in an experiment site, the silencing chamber has the size parameters as follows: the width is 1-2m, the depth is 2-4m, the height is 1-3m, with a shockproof frame type of main body structure. By adopting the parameters, the size of the main body structure is reduced as much as possible on the basis of reserving a space for placing the vibration isolation table and personnel operation, which not only can reduce test cost, but also facilitate noise shielding.
Furthermore, the silencing chamber is also provided with a soundproof door for an operator to enter or exit. The silencing chamber adopts a mode of sound absorption at four sides (including the soundproof door) and on the top surface and sound insulation on the bottom layer, so that a low-noise environment is achieved in the silencing chamber. A
glass steel plate is served as a panel for an outer plate of the silencing chamber adopts, a porous aluminum plate is served for an inner plate, and sound absorption cotton or other sound insulation materials are filled between the inner and outer plates, with a thickness of 3-12mm, and the surface of the plate sprayed with damping paint.
The bottom of the silencing chamber is not in direct contact with the floor of the experiment site, but has a certain gap with the floor of the experiment site.
That is, it is hollow between the bottom of the silencing chamber and the floor of the experiment site, and some damping materials such as butyl rubber, polyurethane foam and the like can be filled therebetween in other embodiments.
Date Recue/Date Received 2020-04-30 According to the invention, a honeycomb type vibration isolation structure is further designed at the bottom of the silencing chamber. The honeycomb type vibration isolation structure adopts trapezoidal aluminum-zinc plated steel plates to be adhered to each other, and a plurality of grooves are punched on the surfaces of the steel plates to increase the supporting strength, so that the contact surface between the floor of the silencing chamber and the floor of the experiment site is small, with high strength and small local deformation. The silencing chamber design is shown in Fig. 1.
In an embodiment of the invention, an air-floating vibration isolation table and two spring vibration isolation tables are arranged on a floor of a silencing chamber to form a three-stage vibration isolation device, and a tested acceleration sensor is fixed on a surface of the third-stage vibration isolation table, as shown in Fig. 2 Preferably, the air-floating vibration isolation table can be provided with damping according to the field environment, and has a good vibration isolation effect in a horizontal direction and a perpendicular direction, large bearing capacity, good stability, capability of being automatically leveled, and resistance to aging. But it needs to be connected with an inflation pump, and has a complicated structure, so that the air-floating vibration isolation table is used for the first-stage vibration isolation table.
The spring vibration isolation table is simple in structure, small in size and flexible and convenient to control a table surface, so that the spring vibration isolation table is used for the second-stage vibration isolation table and the third-stage vibration isolation table.
Before the noise test is started, the inflation pump is started to inflate the first-stage air-floating vibration isolation table so as to support the second-stage spring vibration isolation table and the third-stage spring vibration isolation table, and then the second-stage spring vibration isolation table and the third-stage spring vibration isolation table are leveled by a level gauge to realize passive vibration isolation filtering.
In other embodiments, a combination of one air-floating vibration isolation table and three spring vibration isolation tables, or a combination of two air-floating vibration isolation tables and three spring vibration isolation tables may be used. The structure of a three-layer vibration isolation table is explained as an example.
Date Recue/Date Received 2020-04-30 The mechanical model of the three-layer isolation table can be simplified to a mass-spring-damping system, as shown in Fig. 3. Since the mass of the sensor is lighter than the vibration table, it is negligible. ml, m2 and m3 are masses of the first-stage, the second-stage and the third-stage vibration isolation tables respectively; kl, k2 and k3 are spring stiffness coefficients of the three vibration isolation tables respectively; cl, c2 and c3 are damping coefficients of the vibration isolation tables respectively; x I, x2 and x3 are displacements of the three vibration isolation tables relative to the ground respectively;
and a matrix-form motion differential equation of the system is written by using a dynamics law as follows:
M x+ C x+ Kx = F (1) wherein, - -T - - T
iT X = xl, x2, x3 x = xl, x2, x3 x = x2, x3.1 F =[0,0,F1 The mass matrix, the damping matrix and the stiffness matrix are respectively as follows:
ml 0 0 M= 0 m2 0 0 0 m3 -cl+ c2 ¨c2 0 C= ¨c2 cl+ c2 ¨c3 0 ¨c3 c3 -kl+ k2 ¨k2 0 K= ¨k2 k2+ k3 ¨k3 0 ¨k3 k3 - -According to the vibration isolation device, it can meet the background noise test environment required by the high-precision acceleration sensor, greatly expanding the application scene of the test device; and the device can be built in an urban building environment, and the test cost is reduced.
In order to further reduce the background noise of the testing device, the background Date Recue/Date Received 2020-04-30 noise of a higher-precision acceleration sensor is tested, and noise suppression capability of a low-frequency band is improved. On the basis of the vibration isolation device, a vibration damping system with notch frequency characteristics is further designed in an active control mode, and noise of the test environment can be further reduced by the vibration damping system.
The device for testing the background noise of the acceleration sensor further comprises a damping system for testing the background noise of the acceleration sensor, wherein the damping system comprises:
a standard sensor group including a sensor for measuring a change in acceleration of the vibration isolation table, a sensor for measuring a change in angular velocity of the vibration isolation table, and a displacement sensor, wherein the standard sensor group is installed on the surface of the third-stage vibration isolation table;
a signal detection and conditioning unit for performing signal conditioning on acceleration, angular velocity signals and displacement signals of the standard sensor group and performing servo control on the sensor;
an acquisition unit for acquiring acceleration change data, angular velocity change data, displacement change data and data of the tested acceleration sensor;
a control unit for controlling the action of the driver according to the acceleration change data, the angular velocity change data and the displacement change data acquired by the acquisition unit; the control unit structure adopts feedback control of a three-ring closed loop of an acceleration ring, a speed ring and a position ring, and a feedforward controller is added into the acceleration loop to form a composite control method combining feedforward control and feedback control, so that the steady-state error of the system is reduced, further improving the active suppression capability of the vibration isolation table on low-frequency disturbance; and a driver for adjusting the vibration isolation table to perform a reverse motion according to the data detected by the standard sensor group, thereby further attenuating vibration of the vibration isolation table; the driver is mounted on a specific support and positioned Date Recue/Date Received 2020-04-30 below a surface of a bearing vibration isolation table and at a side edge of the surface of the bearing vibration isolation table.
In an embodiment, a resonant peak at the natural frequency of the vibration isolation table may be reduced by adjusting the motion of the vibration isolation table.
a noise processing unit for processing the noise data and obtaining the background noise of the tested acceleration sensor.
According to the vibration damping system, vibration damping of noises with different degrees of freedom can be realized according to different number and combination modes of sensors adopted by the standard sensor group.
In an embodiment of the present invention, the standard sensor group comprises a sensor for measuring a change in acceleration of the vibration isolation table, a sensor for measuring a change in angular velocity of the vibration isolation table, and a displacement sensor. The sensors are all installed on the surface of the third-stage vibration isolation table. As the vibration acting on the third-stage vibration isolation table is very small, the sensors with small size, light weight, low noise, high precision and high bandwidth are selected. Setting a coordinate system of the surface is as shown in Fig. 5, wherein the Z axis is an upward direction of the vertical table surface, the X
axis is a forward direction of the parallel table surface, and the Y axis is a rightward direction of the parallel table surface.
As an embodiment, the sensor for measuring the acceleration change of the vibration isolation table adopts a high-precision acceleration sensor for sensing the vibration angular acceleration around the X-axis direction of the vibration isolation table. However, since the acceleration sensor measures linear acceleration, two acceleration sensors are required to be installed for measuring one axis to convert the linear acceleration into the angular acceleration. In the working process, the angular acceleration of the surface of the third-stage vibration isolation table is less than or equal to 10 o/s2, and the diameter of the table surface is not more than lm. Hence, the accelerometer is selected with a measuring range of 0.02g, a noise power spectral density of 0.0lughi Hz and a bandwidth of Date Recue/Date Received 2020-04-30 500Hz. The sensor for measuring the angular velocity change of the vibration isolation table adopts a high-precision solid-state gyroscope, with the sensitive axis coinciding with the X axis. This embodiment selects a gyroscope with a measuring range of 20 /s, a bandwidth of 200 Hz, a zero-bias stability of 0.05 /h, and an angular random walk of 0.003 hi hr. The displacement sensor of this embodiment has a measuring range of 200 mm and an accuracy of 0.001 mm.
As an example, a very wideband pendulum seismometer may also be used as a standard measurement unit for the position loop. Because the output stability is good at low frequency, the low-frequency drift of the speed ring of the vibration isolation table can be well compensated, expanding the response of the system at low frequency.
However, because the very broadband pendulum seismometer outputs velocity, it needs to be used with an integrator. The range is 0.01m/s and the bandwidth is 50Hz-120s.
As an example, it is not limited to a two-degree-of-freedom damping system consisting of only two acceleration sensors, one solid-state gyroscope, and one displacement sensor.
Four acceleration sensors, two solid gyroscopes and two displacement sensors can also be adopted to form a four-degree-of-freedom damping system; and six acceleration sensors, three solid-state gyroscopes and three displacement sensors can also be adopted to form a six-degree-of-freedom damping system . The number and different combinations of standard sensors determine the freedom of testing.
The manner in which the standard sensor group is installed is shown in Fig. 5, taking sensing vibrations about the X-axis direction as an example. The sensor for measuring the acceleration change of the vibration isolation table is arranged at a position below the surface of the third-stage vibration isolation table, parallel to the Y axis and equidistant from the center of the table surface. Since a sensitive unit of the solid-state gyroscope is made of metal materials, great moment of inertia can be brought if the sensitive unit and a servo circuit are both installed on the vibration isolation table, so that the sensitive unit of the gyroscope is separated from the circuit during installation, and only the sensitive unit of the gyroscope is installed at an edge position below the surface of the third-stage vibration isolation table; and the sensitive axis of the sensitive unit coincides with the X
Date Recue/Date Received 2020-04-30 axis, and the gyroscope circuit is installed on a floor or other positions.
The displacement sensor is arranged at an edge position below the surface of the third-stage vibration isolation table. For a two- and three-degree-of-freedom damping system, the standard sensor group is installed in a manner similar to that described above, except that the sensitive axis is different.
A signal detection and conditioning unit used for performing signal conditioning on acceleration, angular velocity signals and displacement signals of the standard sensor group and performing servo control on the sensor.
According to the signal detection and conditioning unit, different circuit structures are adopted for different sensors, an analog-digital hybrid circuit can be formed by an analog device and a digital processor, and the digital part can be realized by an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).
In an embodiment of the invention, the closed-loop detection and conditioning circuit of the accelerometer is composed of an analog preamplifier circuit, a switch circuit, an analog-to-digital conversion circuit, a PID circuit, a time sequence control circuit and a down-sampling filter. Other circuits are all digital circuits and implemented in an FPGA
except that the preamplifier circuit and the switch circuit adopt analog devices. A
closed-loop detection and conditioning circuit of the gyroscope consists of an amplitude control circuit, a numerical control oscillation circuit, a cross coupling circuit and an angular velocity output circuit, which are all implemented in the FPGA. A
block diagram of the signal detection and conditioning unit is shown in Fig. 6.
An acquisition unit divided into two modules, wherein a first module is used for acquiring acceleration change data, angular velocity change data and displacement change data acquired by the signal detection and conditioning unit; the module can adopt an FPGA as a processor for acquiring signals; and acceleration change data, angular velocity change data and displacement change data output by the signal conditioning circuit are fused as sensor data to output the signals to the control unit. A second module is used for collecting output data of the tested acceleration sensor; in the case where the tested acceleration sensor is in analog output, an 18-bit or 24-bit analog-to-digital converter Date Recue/Date Received 2020-04-30 (ADC) can be used for firstly converting an analog-to-digital signal and then outputting the analog-to-digital signal to a noise processing unit; and in the case where the measured acceleration sensor is a digital output, it can be directly output to the noise processing unit.
A control unit used for controlling the action of the driver according to the acceleration change data, the angular velocity change data and the displacement change data which are interfered by the third-stage vibration isolation table.
In an embodiment of the invention, the control unit forms a three-closed-loop feedback control system consisting of an acceleration closed loop, a speed closed loop and a position closed loop; interference is firstly suppressed by the acceleration closed loop feedback, stable input is provided for the speed closed loop, low-frequency noise such as angular velocity drift caused by acceleration sensor integration is suppressed by the speed closed loop feedback, and low-frequency noise such as angular position drift existing after gyroscope integration is suppressed by the position closed loop feedback. Finally, angular position information subjected to correction and noise suppression is output, so that the driver performs actions according to the angular position information. The three-closed-loop feedback control structure is shown in Fig. 7, Ca(s), Cg(s) and Cd(s) are respectively an acceleration closed-loop controller, a speed closed-loop controller and a position closed-loop controller; Ga(s) is an acceleration open-loop transfer function, and v(s) and 0(s) are respectively an angular velocity and an angular position of a surface of a third-stage vibration isolation table; 0i(s) and Ai(s) are the disturbance angular position and the disturbance acceleration respectively; and 00(s) is the stable position of the vibration isolation table and is generally zero. The suppression transfer function of the third-stage vibration isolation table to disturbance is as follows:
t9(s) 1 1 1 E ¨ 0 Bi(s) 1+GaC. 1 + ¨1C 1 + ¨s1Cd According to the three-closed-loop feedback control system, the suppression to the disturbance is determined by the suppression capability of the acceleration ring, the speed Date Recue/Date Received 2020-04-30 ring and the position ring together, so that the suppression capability of the vibration isolation table on the disturbance is improved; and the structure is combined with a high-precision acceleration sensor and a high-precision solid-state gyroscope in a standard sensor group, so that the stability precision of the vibration isolation table is improved.
In order to further improve the suppression capability of the vibration isolation table on medium-low frequency disturbance, a feedforward control unit is further arranged in an embodiment of the invention, so that the feedforward control unit and the feedback control are combined to form composite control, and the residual disturbance after passive vibration isolation and closed-loop feedback suppression is compensated to cause the output of the angle to be zero. In an embodiment of the invention, a feedforward control based on speed disturbance is added in the three-closed-loop feedback control structure, and a solid-state gyroscope is placed on the rotating base of the silencing chamber for measuring the disturbance speed of the base of the vibration isolation table and providing disturbance information for the feedforward control. As shown in Fig. 7, Vi(s) represents the disturbance velocity on the floor of the silencing chamber; Va(s) represents the disturbance velocity after being suppressed by the three-stage vibration isolation table; Gn(s) represents the noise suppression capability through the three-stage vibration isolation table; Gap(5) represents the suppression capability of the acceleration loop; He(s) represents the characteristics of the feedforward control loop solid-state gyroscope; and Cev(s) represents the feedforward controller. The output of the control system after the feedforward controller is added is as follows:
¨
GõGa p +1 - fi,C frGa closed S Vi(S) 9(S) __________________ 1 1+1 Ga ¨closedCft, + s2 Ga closed d Ga closed(S) is the closed-loop transfer function of the acceleration loop. It can be concluded from the formula that Gn Gap is a residual error of the disturbance of the rotating base of the silencing chamber fed back by the three-stage vibration isolation table and the vibration damping system, Hfv CfvGa closed/S is the suppression of the disturbance Date Recue/Date Received 2020-04-30 by the velocity feedforward control, the feedforward control is to compensate the disturbance residual error of the vibration isolation table by the feedforward control, that is, Gn Ga_p + Hi' v CfvGa closed/s = 0, so that the expression of feedforward controller is deduced as follows:
GnGa pS
= _____________ Ga closed A driver for adjusting the vibration isolation table to perform a reverse motion according to the data detected by the standard sensor group, thereby further attenuating vibration of the vibration isolation table.
In an embodiment of the present invention, a voice coil motor may be used as a driver for a vibration damping system with high accuracy, sensitivity to response, and suitability for short range, fast response, and high precision closed loop servo control.
Taking the noise vibration direction around the X-axis as an example, it is necessary to mount a voice coil motor above or below the table surface near the edge of the table surface.
Preferably, the voice coil motor has a maximum range of 200 mm and an accuracy of 1 um.
As an example, a vibration exciter may act as a driver for the vibration damping system when a stable driving force is required in the low frequency range. The vibration exciter can be installed on a stable support connected with the ground, and a pushing or pulling force is applied to the table surface by a push-pull rod. Preferably, the vibration exciter has a maximum displacement of 100 mm and a frequency range of DC-1kHz.
A noise processing unit for processing the noise data and obtaining the background noise of the tested acceleration sensor.
As an embodiment, the noise processing unit can set parameters such as the number of sets, frequency, scaling factor, frequency range of interest and the like for collected data, perform noise processing on a plurality of sets of collected output data of tested acceleration sensors, and finally calculate the background noise of the tested acceleration sensors and draw a noise power spectral density curve.
In an embodiment of the invention, a window function is added to the data to prevent Date Recue/Date Received 2020-04-30 spectral leakage prior to calculating the noise power spectral density.
Considering that windowing will reduce the resolution of narrowband signal, a 7-order Blackman-Harris window function is adopted in the embodiment, because the sidelobe amplitude thereof is very low, causing small influence on the resolution of the narrowband signal after the windowing.
An EMC unit for preventing the system from generating radiation interference to the outside and also preventing the system from being interfered by the outside, thereby ensuring correctness and stability of the operation of the system.
As an example, in a standard sensor group, the sensitive unit of the acceleration sensor is shielded in a shell with the circuit, the circuit of the gyroscope is separated from the sensitive unit and independently shielded in a shell, and the signal conditioning unit, the acquisition unit and the control unit are shielded in a shell, which are simply referred to as a system circuit.
Specifically, the EMC unit comprises:
(1) Shell shielding The sensor sensitive unit, the sensor circuit and the system circuit all adopt aluminum alloy shells, so that common-mode interference has a medium and a path for reflection, absorption and offset.
(2) Grounding The sensor circuit is operatively interconnected with an aluminum alloy shell of the sensor sensitive unit at a position proximate to a connector, and then interfering current enters the shell prior to flowing through the circuit, so that the sensor circuit and its sensitive unit are not disturbed by common mode current.
A circle of discontinuous bare copper is distributed on the surface of the system circuit along the edge of the circuit board to serve as a ground wire, and is locked with the surface of the metal shell via a metal screw to realize tight electrical contact.
(3) Cable Date Recue/Date Received 2020-04-30 The system is complex in wiring, an external cable is arranged among the sensor, the power supply and the system circuit, and the wiring is also arranged among several circuit boards in the system circuit.
For external cables, the location where the cables are distributed is mainly considered. In order to reduce radiation, the circuit loop area should be reduced as much as possible; the shape of the closed loop should be as narrow as possible to reduce the radiation interference of differential mode current; and the cables for sensitive signals are as short as possible and remote from interfering signal sources, such as signal lines not bundled with power lines.
The circuit boards in the shell are interconnected by pin headers or flat cables to ensure that the cable has a minimum length in a polarization direction of a larger radiation level to reduce electromagnetic energy coupled by the signal wires. In addition, in order to avoid ESD interference, conductive foam is added among the signal conditioning circuit, the acquisition circuit and the control circuit board, and a low-impedance discharge path of ESD interference is designed.
(4) Circuit board design The system contains analog circuit and digital circuit, and the layout and wiring design of hybrid circuit should be considered in a PCB design to avoid signal interference.
The layout of the components is divided into an analog region and a digital region, the analog devices are distributed in the analog region, the digital devices are distributed in the digital region, and the devices in the two regions cannot be mixed and distributed.
The analog region and the digital region each have a corresponding reference ground plane, and the analog and digital reference ground planes are independent and complete planes, respectively, located below the analog region and the digital region.
The analog and digital regions have respective analog and digital power supplies.
Shielded ground wires are used to isolate the analog and digital regions, and the shielded ground wires are interconnected to the ground plane by a plurality of via holes.
Date Recue/Date Received 2020-04-30 As shown in Fig. 8, in order to only use the test result of the vibration isolation device, it can be seen that the noise base of the tested accelerometer is higher due to the limitation of the background noise of the test system, but it can meet the noise test requirement of the high-precision acceleration sensor; Fig. 9 is a test result using the vibration isolation device and an active vibration damping system, and it can be seen that the use of the active vibration damping system can reduce the noise base of the system and meet the test requirement of the acceleration sensor with higher accuracy.
In the actual test, sometimes external interference signals will fall into the inherent frequency band of the background noise of the tested acceleration sensor, so that a test result of the background noise is affected, and the interference cannot be filtered by a filter.
In an embodiment of the invention, the tested acceleration sensor is required to be tested for noise in different directions. When the sensitive direction of the acceleration sensor is parallel to the X-axis or the Y-axis, the rotating chassis of the silencing chamber is started to rotate at a certain low frequency, and now the tested acceleration sensor and the reference gyroscope are sampled. The low frequency is 1-10 Hz in an embodiment of the invention. Because the output signals of the both are related signals, the interference signals are not related to the output signals, and the interference signals of the both signals are not related to each other, so that the external interference signals are suppressed.
Specifically, when the background noise of the acceleration sensor is tested, the background noise in a direction of +1g, a direction of +1g, a direction of +1g and a direction of +Og are tested respectively. When background noise in the direction of +1g and the direction of -1g is tested, the sensitive direction of the acceleration sensor is parallel to the Z axis; when background noise in the direction of Og is tested, the sensitive direction of the acceleration sensor is parallel to the X axis or the Y axis.
During testing, the chassis of the testing device is rotated, a rotation frequency is 6 , and T
a sampling interval of the output of the tested acceleration sensor is . If the background Date Recue/Date Received 2020-04-30 noise in the direction of Og is tested, the output of the tested acceleration sensor is as follows:
d 0(k) = Aocos(co x k xT, + p)+ no (k) = go(k)+ no(k) wherein C is an initial phase of the signal, g is a gravity acceleration signal without interference noise, and n 0(k) is external interference.
The sensitive axis of the gyroscope on the chassis is parallel to the Z axis, the output of the gyroscope is used as a reference signal, and the amplitude is normalized.
At this time, the output of the gyroscope is as follows:
dr (k)= cos(co xkxTs)+ r(k) = ro(k)+ r(k) wherein is an angular velocity signal without interference noise, and r is external interference to the gyroscope.
Since the acceleration sensor is related to the reference signal of the gyroscope, the related signals of the tested acceleration sensor and the gyroscope are as follows:
N ¨1 + r)x a 1,(k)= Fgoro(r)+ Fgon,(r)+ Frono(r)+ Fnon,(r) N k=0 wherein the acceleration signal is irrelevant to the interference noise, so the sum of F (r) F (r) gon, and r n is 0, and the correlation between the external interference received by the tested acceleration sensor and the external interference received by the gyroscope F,, (T) -is very weak, so n' 15 0. Thus, Ao F, F goro(r) = ¨cos(cor + p) Therefore, the output of the tested acceleration sensor suppressing the external interference can be obtained:
go (k) = 2 x Fdo (r) = 4 cos(co +
Date Recue/Date Received 2020-04-30 By using this output signal to calculate the power spectral density, the background noise of the acceleration sensor without interference signals can be obtained in the inherent frequency range.
If the background noise in the directions of +1g and -1g is tested, the acceleration sensor outputs a direct-current slowly-varying signal because the output of the acceleration sensor is not affected by rotation, and the external interference can be filtered by a low-pass filter or a moving average filter When different tested acceleration sensors are subjected to noise tests in different directions, and the sensitive direction of the acceleration sensors is parallel to the X axis or the Y axis, the rotating chassis of the silencing chamber is started to rotate at a certain low frequency, and the tested acceleration sensors and now the reference gyroscope are sampled. Because the output signals of the both are related signals, the interference signals are not related to the output signals, and the interference signals of the both signals are not related to each other, so that the external interference signals can be suppressed.
According to the invention, the environment noise interference is reduced by adopting a passive filtering mode, meeting the background noise test requirement of the high-precision sensor; in order to meet the requirements of the background noise test environment of the acceleration sensor with higher accuracy, it adopts a combination of passive filtering and damping control technology, and corresponding circuit design, control method design and electromagnetic compatibility (EMC) design; and based on the correlation detection method, interference signals in the background noise frequency range of the tested sensor are suppressed to finally obtain a clean background noise result of the tested sensor.
Although the preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concept is known. It is therefore intended that the appended claims be interpreted as including the preferred embodiments and all such changes and modifications as fall within the true scope of the present invention.
Date Recue/Date Received 2020-04-30 It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Date Recue/Date Received 2020-04-30
Fig. 6 is a block diagram of a signal detection and conditioning unit according to an embodiment of the present invention;
Fig. 7 is a block diagram of a control unit according to an embodiment of the present invention;
Fig. 8 is a result of testing a high-precision acceleration sensor according to an embodiment of the present invention;
Fig. 9 is a result of testing a higher-precision acceleration sensor according to an embodiment of the present invention.
Detailed Description of the Invention In order to solve the problem in the prior art, the invention provides a device and a method for testing background noise of a high precision acceleration sensor, which can reduce the affection of environmental noise on the background noise testing process of the acceleration sensor under a condition of poor environment, so that the measured background noise of the acceleration sensor is closer to a true value, and is more suitable for being practical.
In order to further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purposes of the present invention, the device and method for testing the background noise of the acceleration sensor according to the present invention, as well as the specific embodiments, structures, characteristics and effects thereof, will be described in detail with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "the embodiment" means not necessarily the same embodiment. Furthermore, the features, structures, or characteristics of one or more embodiments may be combined in any suitable form.
The term "and/or", as used herein, is merely an association that describes associated Date Recue/Date Received 2020-04-30 objects, meaning that there may be three relationships, e.g., A and/or B, which can be specifically understood as that A and B may be included together, A may be present alone or B may be present alone, and any of the above three cases may be provided.
An embodiment of the invention provides a device for testing background noise of an acceleration sensor, comprising a vibration isolation device and a vibration damping system.
Among them, the vibration isolation device comprises a silencing chamber and a vibration isolation table, wherein the vibration isolation table comprises an air-floating vibration isolation table and a multi-stage elastic vibration isolation table.
The silencing chamber is internally provided with an accommodating space.
In an embodiment of the invention, a rotating base is installed on the ground of the silencing chamber, the rotating base can rotate unifoitaly at a determined angular velocity.
The air-floating vibration isolation table is arranged on the rotating base of the silencing chamber and can rotate along with the rotating base, and the multi-stage elastic vibration isolation table is arranged above the air-floating vibration isolation table after being connected in series. Furthermore, an inflation pump is arranged to inflate the air-floating vibration isolation table, and the tested acceleration sensor is arranged on a surface of a bearing vibration isolation table which is located at an uppermost part of the multi-stage elastic vibration isolation table.
Furthermore, since testing environment and the sensor to be tested are different each time, the inflation pump is arranged to inflate the air-floating vibration isolation table; and the inflation pump is provided with an air pressure meter, the air pressure of the air-floating vibration isolation table can be set by the inflation pump provided with the air pressure meter, and transfer function parameters of vibration can be adjusted by adjusting the air pressure according to different testing environment.
The air-floating vibration isolation table comprises an air-floating table surface and at least one first-stage supporting leg. The first-stage supporting leg is arranged between the floor of the silencing chamber and the air-floating table surface. The multi-stage elastic Date Recue/Date Received 2020-04-30 vibration isolation table comprises a plurality of supporting tables and elastic supporting legs, the elastic supporting legs are arranged between the supporting tables, and the elastic supporting legs of the elastic vibration isolation table at a bottommost layer are arranged between the air-floating vibration isolation table and the supporting table at the bottommost layer.
The device for testing the background noise of the acceleration sensor further comprises a level gauge. The level gauge is used for leveling the surface of the multi-stage elastic vibration isolation table.
According to an embodiment of the invention, the silencing chamber is built in an experiment site, the silencing chamber has the size parameters as follows: the width is 1-2m, the depth is 2-4m, the height is 1-3m, with a shockproof frame type of main body structure. By adopting the parameters, the size of the main body structure is reduced as much as possible on the basis of reserving a space for placing the vibration isolation table and personnel operation, which not only can reduce test cost, but also facilitate noise shielding.
Furthermore, the silencing chamber is also provided with a soundproof door for an operator to enter or exit. The silencing chamber adopts a mode of sound absorption at four sides (including the soundproof door) and on the top surface and sound insulation on the bottom layer, so that a low-noise environment is achieved in the silencing chamber. A
glass steel plate is served as a panel for an outer plate of the silencing chamber adopts, a porous aluminum plate is served for an inner plate, and sound absorption cotton or other sound insulation materials are filled between the inner and outer plates, with a thickness of 3-12mm, and the surface of the plate sprayed with damping paint.
The bottom of the silencing chamber is not in direct contact with the floor of the experiment site, but has a certain gap with the floor of the experiment site.
That is, it is hollow between the bottom of the silencing chamber and the floor of the experiment site, and some damping materials such as butyl rubber, polyurethane foam and the like can be filled therebetween in other embodiments.
Date Recue/Date Received 2020-04-30 According to the invention, a honeycomb type vibration isolation structure is further designed at the bottom of the silencing chamber. The honeycomb type vibration isolation structure adopts trapezoidal aluminum-zinc plated steel plates to be adhered to each other, and a plurality of grooves are punched on the surfaces of the steel plates to increase the supporting strength, so that the contact surface between the floor of the silencing chamber and the floor of the experiment site is small, with high strength and small local deformation. The silencing chamber design is shown in Fig. 1.
In an embodiment of the invention, an air-floating vibration isolation table and two spring vibration isolation tables are arranged on a floor of a silencing chamber to form a three-stage vibration isolation device, and a tested acceleration sensor is fixed on a surface of the third-stage vibration isolation table, as shown in Fig. 2 Preferably, the air-floating vibration isolation table can be provided with damping according to the field environment, and has a good vibration isolation effect in a horizontal direction and a perpendicular direction, large bearing capacity, good stability, capability of being automatically leveled, and resistance to aging. But it needs to be connected with an inflation pump, and has a complicated structure, so that the air-floating vibration isolation table is used for the first-stage vibration isolation table.
The spring vibration isolation table is simple in structure, small in size and flexible and convenient to control a table surface, so that the spring vibration isolation table is used for the second-stage vibration isolation table and the third-stage vibration isolation table.
Before the noise test is started, the inflation pump is started to inflate the first-stage air-floating vibration isolation table so as to support the second-stage spring vibration isolation table and the third-stage spring vibration isolation table, and then the second-stage spring vibration isolation table and the third-stage spring vibration isolation table are leveled by a level gauge to realize passive vibration isolation filtering.
In other embodiments, a combination of one air-floating vibration isolation table and three spring vibration isolation tables, or a combination of two air-floating vibration isolation tables and three spring vibration isolation tables may be used. The structure of a three-layer vibration isolation table is explained as an example.
Date Recue/Date Received 2020-04-30 The mechanical model of the three-layer isolation table can be simplified to a mass-spring-damping system, as shown in Fig. 3. Since the mass of the sensor is lighter than the vibration table, it is negligible. ml, m2 and m3 are masses of the first-stage, the second-stage and the third-stage vibration isolation tables respectively; kl, k2 and k3 are spring stiffness coefficients of the three vibration isolation tables respectively; cl, c2 and c3 are damping coefficients of the vibration isolation tables respectively; x I, x2 and x3 are displacements of the three vibration isolation tables relative to the ground respectively;
and a matrix-form motion differential equation of the system is written by using a dynamics law as follows:
M x+ C x+ Kx = F (1) wherein, - -T - - T
iT X = xl, x2, x3 x = xl, x2, x3 x = x2, x3.1 F =[0,0,F1 The mass matrix, the damping matrix and the stiffness matrix are respectively as follows:
ml 0 0 M= 0 m2 0 0 0 m3 -cl+ c2 ¨c2 0 C= ¨c2 cl+ c2 ¨c3 0 ¨c3 c3 -kl+ k2 ¨k2 0 K= ¨k2 k2+ k3 ¨k3 0 ¨k3 k3 - -According to the vibration isolation device, it can meet the background noise test environment required by the high-precision acceleration sensor, greatly expanding the application scene of the test device; and the device can be built in an urban building environment, and the test cost is reduced.
In order to further reduce the background noise of the testing device, the background Date Recue/Date Received 2020-04-30 noise of a higher-precision acceleration sensor is tested, and noise suppression capability of a low-frequency band is improved. On the basis of the vibration isolation device, a vibration damping system with notch frequency characteristics is further designed in an active control mode, and noise of the test environment can be further reduced by the vibration damping system.
The device for testing the background noise of the acceleration sensor further comprises a damping system for testing the background noise of the acceleration sensor, wherein the damping system comprises:
a standard sensor group including a sensor for measuring a change in acceleration of the vibration isolation table, a sensor for measuring a change in angular velocity of the vibration isolation table, and a displacement sensor, wherein the standard sensor group is installed on the surface of the third-stage vibration isolation table;
a signal detection and conditioning unit for performing signal conditioning on acceleration, angular velocity signals and displacement signals of the standard sensor group and performing servo control on the sensor;
an acquisition unit for acquiring acceleration change data, angular velocity change data, displacement change data and data of the tested acceleration sensor;
a control unit for controlling the action of the driver according to the acceleration change data, the angular velocity change data and the displacement change data acquired by the acquisition unit; the control unit structure adopts feedback control of a three-ring closed loop of an acceleration ring, a speed ring and a position ring, and a feedforward controller is added into the acceleration loop to form a composite control method combining feedforward control and feedback control, so that the steady-state error of the system is reduced, further improving the active suppression capability of the vibration isolation table on low-frequency disturbance; and a driver for adjusting the vibration isolation table to perform a reverse motion according to the data detected by the standard sensor group, thereby further attenuating vibration of the vibration isolation table; the driver is mounted on a specific support and positioned Date Recue/Date Received 2020-04-30 below a surface of a bearing vibration isolation table and at a side edge of the surface of the bearing vibration isolation table.
In an embodiment, a resonant peak at the natural frequency of the vibration isolation table may be reduced by adjusting the motion of the vibration isolation table.
a noise processing unit for processing the noise data and obtaining the background noise of the tested acceleration sensor.
According to the vibration damping system, vibration damping of noises with different degrees of freedom can be realized according to different number and combination modes of sensors adopted by the standard sensor group.
In an embodiment of the present invention, the standard sensor group comprises a sensor for measuring a change in acceleration of the vibration isolation table, a sensor for measuring a change in angular velocity of the vibration isolation table, and a displacement sensor. The sensors are all installed on the surface of the third-stage vibration isolation table. As the vibration acting on the third-stage vibration isolation table is very small, the sensors with small size, light weight, low noise, high precision and high bandwidth are selected. Setting a coordinate system of the surface is as shown in Fig. 5, wherein the Z axis is an upward direction of the vertical table surface, the X
axis is a forward direction of the parallel table surface, and the Y axis is a rightward direction of the parallel table surface.
As an embodiment, the sensor for measuring the acceleration change of the vibration isolation table adopts a high-precision acceleration sensor for sensing the vibration angular acceleration around the X-axis direction of the vibration isolation table. However, since the acceleration sensor measures linear acceleration, two acceleration sensors are required to be installed for measuring one axis to convert the linear acceleration into the angular acceleration. In the working process, the angular acceleration of the surface of the third-stage vibration isolation table is less than or equal to 10 o/s2, and the diameter of the table surface is not more than lm. Hence, the accelerometer is selected with a measuring range of 0.02g, a noise power spectral density of 0.0lughi Hz and a bandwidth of Date Recue/Date Received 2020-04-30 500Hz. The sensor for measuring the angular velocity change of the vibration isolation table adopts a high-precision solid-state gyroscope, with the sensitive axis coinciding with the X axis. This embodiment selects a gyroscope with a measuring range of 20 /s, a bandwidth of 200 Hz, a zero-bias stability of 0.05 /h, and an angular random walk of 0.003 hi hr. The displacement sensor of this embodiment has a measuring range of 200 mm and an accuracy of 0.001 mm.
As an example, a very wideband pendulum seismometer may also be used as a standard measurement unit for the position loop. Because the output stability is good at low frequency, the low-frequency drift of the speed ring of the vibration isolation table can be well compensated, expanding the response of the system at low frequency.
However, because the very broadband pendulum seismometer outputs velocity, it needs to be used with an integrator. The range is 0.01m/s and the bandwidth is 50Hz-120s.
As an example, it is not limited to a two-degree-of-freedom damping system consisting of only two acceleration sensors, one solid-state gyroscope, and one displacement sensor.
Four acceleration sensors, two solid gyroscopes and two displacement sensors can also be adopted to form a four-degree-of-freedom damping system; and six acceleration sensors, three solid-state gyroscopes and three displacement sensors can also be adopted to form a six-degree-of-freedom damping system . The number and different combinations of standard sensors determine the freedom of testing.
The manner in which the standard sensor group is installed is shown in Fig. 5, taking sensing vibrations about the X-axis direction as an example. The sensor for measuring the acceleration change of the vibration isolation table is arranged at a position below the surface of the third-stage vibration isolation table, parallel to the Y axis and equidistant from the center of the table surface. Since a sensitive unit of the solid-state gyroscope is made of metal materials, great moment of inertia can be brought if the sensitive unit and a servo circuit are both installed on the vibration isolation table, so that the sensitive unit of the gyroscope is separated from the circuit during installation, and only the sensitive unit of the gyroscope is installed at an edge position below the surface of the third-stage vibration isolation table; and the sensitive axis of the sensitive unit coincides with the X
Date Recue/Date Received 2020-04-30 axis, and the gyroscope circuit is installed on a floor or other positions.
The displacement sensor is arranged at an edge position below the surface of the third-stage vibration isolation table. For a two- and three-degree-of-freedom damping system, the standard sensor group is installed in a manner similar to that described above, except that the sensitive axis is different.
A signal detection and conditioning unit used for performing signal conditioning on acceleration, angular velocity signals and displacement signals of the standard sensor group and performing servo control on the sensor.
According to the signal detection and conditioning unit, different circuit structures are adopted for different sensors, an analog-digital hybrid circuit can be formed by an analog device and a digital processor, and the digital part can be realized by an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).
In an embodiment of the invention, the closed-loop detection and conditioning circuit of the accelerometer is composed of an analog preamplifier circuit, a switch circuit, an analog-to-digital conversion circuit, a PID circuit, a time sequence control circuit and a down-sampling filter. Other circuits are all digital circuits and implemented in an FPGA
except that the preamplifier circuit and the switch circuit adopt analog devices. A
closed-loop detection and conditioning circuit of the gyroscope consists of an amplitude control circuit, a numerical control oscillation circuit, a cross coupling circuit and an angular velocity output circuit, which are all implemented in the FPGA. A
block diagram of the signal detection and conditioning unit is shown in Fig. 6.
An acquisition unit divided into two modules, wherein a first module is used for acquiring acceleration change data, angular velocity change data and displacement change data acquired by the signal detection and conditioning unit; the module can adopt an FPGA as a processor for acquiring signals; and acceleration change data, angular velocity change data and displacement change data output by the signal conditioning circuit are fused as sensor data to output the signals to the control unit. A second module is used for collecting output data of the tested acceleration sensor; in the case where the tested acceleration sensor is in analog output, an 18-bit or 24-bit analog-to-digital converter Date Recue/Date Received 2020-04-30 (ADC) can be used for firstly converting an analog-to-digital signal and then outputting the analog-to-digital signal to a noise processing unit; and in the case where the measured acceleration sensor is a digital output, it can be directly output to the noise processing unit.
A control unit used for controlling the action of the driver according to the acceleration change data, the angular velocity change data and the displacement change data which are interfered by the third-stage vibration isolation table.
In an embodiment of the invention, the control unit forms a three-closed-loop feedback control system consisting of an acceleration closed loop, a speed closed loop and a position closed loop; interference is firstly suppressed by the acceleration closed loop feedback, stable input is provided for the speed closed loop, low-frequency noise such as angular velocity drift caused by acceleration sensor integration is suppressed by the speed closed loop feedback, and low-frequency noise such as angular position drift existing after gyroscope integration is suppressed by the position closed loop feedback. Finally, angular position information subjected to correction and noise suppression is output, so that the driver performs actions according to the angular position information. The three-closed-loop feedback control structure is shown in Fig. 7, Ca(s), Cg(s) and Cd(s) are respectively an acceleration closed-loop controller, a speed closed-loop controller and a position closed-loop controller; Ga(s) is an acceleration open-loop transfer function, and v(s) and 0(s) are respectively an angular velocity and an angular position of a surface of a third-stage vibration isolation table; 0i(s) and Ai(s) are the disturbance angular position and the disturbance acceleration respectively; and 00(s) is the stable position of the vibration isolation table and is generally zero. The suppression transfer function of the third-stage vibration isolation table to disturbance is as follows:
t9(s) 1 1 1 E ¨ 0 Bi(s) 1+GaC. 1 + ¨1C 1 + ¨s1Cd According to the three-closed-loop feedback control system, the suppression to the disturbance is determined by the suppression capability of the acceleration ring, the speed Date Recue/Date Received 2020-04-30 ring and the position ring together, so that the suppression capability of the vibration isolation table on the disturbance is improved; and the structure is combined with a high-precision acceleration sensor and a high-precision solid-state gyroscope in a standard sensor group, so that the stability precision of the vibration isolation table is improved.
In order to further improve the suppression capability of the vibration isolation table on medium-low frequency disturbance, a feedforward control unit is further arranged in an embodiment of the invention, so that the feedforward control unit and the feedback control are combined to form composite control, and the residual disturbance after passive vibration isolation and closed-loop feedback suppression is compensated to cause the output of the angle to be zero. In an embodiment of the invention, a feedforward control based on speed disturbance is added in the three-closed-loop feedback control structure, and a solid-state gyroscope is placed on the rotating base of the silencing chamber for measuring the disturbance speed of the base of the vibration isolation table and providing disturbance information for the feedforward control. As shown in Fig. 7, Vi(s) represents the disturbance velocity on the floor of the silencing chamber; Va(s) represents the disturbance velocity after being suppressed by the three-stage vibration isolation table; Gn(s) represents the noise suppression capability through the three-stage vibration isolation table; Gap(5) represents the suppression capability of the acceleration loop; He(s) represents the characteristics of the feedforward control loop solid-state gyroscope; and Cev(s) represents the feedforward controller. The output of the control system after the feedforward controller is added is as follows:
¨
GõGa p +1 - fi,C frGa closed S Vi(S) 9(S) __________________ 1 1+1 Ga ¨closedCft, + s2 Ga closed d Ga closed(S) is the closed-loop transfer function of the acceleration loop. It can be concluded from the formula that Gn Gap is a residual error of the disturbance of the rotating base of the silencing chamber fed back by the three-stage vibration isolation table and the vibration damping system, Hfv CfvGa closed/S is the suppression of the disturbance Date Recue/Date Received 2020-04-30 by the velocity feedforward control, the feedforward control is to compensate the disturbance residual error of the vibration isolation table by the feedforward control, that is, Gn Ga_p + Hi' v CfvGa closed/s = 0, so that the expression of feedforward controller is deduced as follows:
GnGa pS
= _____________ Ga closed A driver for adjusting the vibration isolation table to perform a reverse motion according to the data detected by the standard sensor group, thereby further attenuating vibration of the vibration isolation table.
In an embodiment of the present invention, a voice coil motor may be used as a driver for a vibration damping system with high accuracy, sensitivity to response, and suitability for short range, fast response, and high precision closed loop servo control.
Taking the noise vibration direction around the X-axis as an example, it is necessary to mount a voice coil motor above or below the table surface near the edge of the table surface.
Preferably, the voice coil motor has a maximum range of 200 mm and an accuracy of 1 um.
As an example, a vibration exciter may act as a driver for the vibration damping system when a stable driving force is required in the low frequency range. The vibration exciter can be installed on a stable support connected with the ground, and a pushing or pulling force is applied to the table surface by a push-pull rod. Preferably, the vibration exciter has a maximum displacement of 100 mm and a frequency range of DC-1kHz.
A noise processing unit for processing the noise data and obtaining the background noise of the tested acceleration sensor.
As an embodiment, the noise processing unit can set parameters such as the number of sets, frequency, scaling factor, frequency range of interest and the like for collected data, perform noise processing on a plurality of sets of collected output data of tested acceleration sensors, and finally calculate the background noise of the tested acceleration sensors and draw a noise power spectral density curve.
In an embodiment of the invention, a window function is added to the data to prevent Date Recue/Date Received 2020-04-30 spectral leakage prior to calculating the noise power spectral density.
Considering that windowing will reduce the resolution of narrowband signal, a 7-order Blackman-Harris window function is adopted in the embodiment, because the sidelobe amplitude thereof is very low, causing small influence on the resolution of the narrowband signal after the windowing.
An EMC unit for preventing the system from generating radiation interference to the outside and also preventing the system from being interfered by the outside, thereby ensuring correctness and stability of the operation of the system.
As an example, in a standard sensor group, the sensitive unit of the acceleration sensor is shielded in a shell with the circuit, the circuit of the gyroscope is separated from the sensitive unit and independently shielded in a shell, and the signal conditioning unit, the acquisition unit and the control unit are shielded in a shell, which are simply referred to as a system circuit.
Specifically, the EMC unit comprises:
(1) Shell shielding The sensor sensitive unit, the sensor circuit and the system circuit all adopt aluminum alloy shells, so that common-mode interference has a medium and a path for reflection, absorption and offset.
(2) Grounding The sensor circuit is operatively interconnected with an aluminum alloy shell of the sensor sensitive unit at a position proximate to a connector, and then interfering current enters the shell prior to flowing through the circuit, so that the sensor circuit and its sensitive unit are not disturbed by common mode current.
A circle of discontinuous bare copper is distributed on the surface of the system circuit along the edge of the circuit board to serve as a ground wire, and is locked with the surface of the metal shell via a metal screw to realize tight electrical contact.
(3) Cable Date Recue/Date Received 2020-04-30 The system is complex in wiring, an external cable is arranged among the sensor, the power supply and the system circuit, and the wiring is also arranged among several circuit boards in the system circuit.
For external cables, the location where the cables are distributed is mainly considered. In order to reduce radiation, the circuit loop area should be reduced as much as possible; the shape of the closed loop should be as narrow as possible to reduce the radiation interference of differential mode current; and the cables for sensitive signals are as short as possible and remote from interfering signal sources, such as signal lines not bundled with power lines.
The circuit boards in the shell are interconnected by pin headers or flat cables to ensure that the cable has a minimum length in a polarization direction of a larger radiation level to reduce electromagnetic energy coupled by the signal wires. In addition, in order to avoid ESD interference, conductive foam is added among the signal conditioning circuit, the acquisition circuit and the control circuit board, and a low-impedance discharge path of ESD interference is designed.
(4) Circuit board design The system contains analog circuit and digital circuit, and the layout and wiring design of hybrid circuit should be considered in a PCB design to avoid signal interference.
The layout of the components is divided into an analog region and a digital region, the analog devices are distributed in the analog region, the digital devices are distributed in the digital region, and the devices in the two regions cannot be mixed and distributed.
The analog region and the digital region each have a corresponding reference ground plane, and the analog and digital reference ground planes are independent and complete planes, respectively, located below the analog region and the digital region.
The analog and digital regions have respective analog and digital power supplies.
Shielded ground wires are used to isolate the analog and digital regions, and the shielded ground wires are interconnected to the ground plane by a plurality of via holes.
Date Recue/Date Received 2020-04-30 As shown in Fig. 8, in order to only use the test result of the vibration isolation device, it can be seen that the noise base of the tested accelerometer is higher due to the limitation of the background noise of the test system, but it can meet the noise test requirement of the high-precision acceleration sensor; Fig. 9 is a test result using the vibration isolation device and an active vibration damping system, and it can be seen that the use of the active vibration damping system can reduce the noise base of the system and meet the test requirement of the acceleration sensor with higher accuracy.
In the actual test, sometimes external interference signals will fall into the inherent frequency band of the background noise of the tested acceleration sensor, so that a test result of the background noise is affected, and the interference cannot be filtered by a filter.
In an embodiment of the invention, the tested acceleration sensor is required to be tested for noise in different directions. When the sensitive direction of the acceleration sensor is parallel to the X-axis or the Y-axis, the rotating chassis of the silencing chamber is started to rotate at a certain low frequency, and now the tested acceleration sensor and the reference gyroscope are sampled. The low frequency is 1-10 Hz in an embodiment of the invention. Because the output signals of the both are related signals, the interference signals are not related to the output signals, and the interference signals of the both signals are not related to each other, so that the external interference signals are suppressed.
Specifically, when the background noise of the acceleration sensor is tested, the background noise in a direction of +1g, a direction of +1g, a direction of +1g and a direction of +Og are tested respectively. When background noise in the direction of +1g and the direction of -1g is tested, the sensitive direction of the acceleration sensor is parallel to the Z axis; when background noise in the direction of Og is tested, the sensitive direction of the acceleration sensor is parallel to the X axis or the Y axis.
During testing, the chassis of the testing device is rotated, a rotation frequency is 6 , and T
a sampling interval of the output of the tested acceleration sensor is . If the background Date Recue/Date Received 2020-04-30 noise in the direction of Og is tested, the output of the tested acceleration sensor is as follows:
d 0(k) = Aocos(co x k xT, + p)+ no (k) = go(k)+ no(k) wherein C is an initial phase of the signal, g is a gravity acceleration signal without interference noise, and n 0(k) is external interference.
The sensitive axis of the gyroscope on the chassis is parallel to the Z axis, the output of the gyroscope is used as a reference signal, and the amplitude is normalized.
At this time, the output of the gyroscope is as follows:
dr (k)= cos(co xkxTs)+ r(k) = ro(k)+ r(k) wherein is an angular velocity signal without interference noise, and r is external interference to the gyroscope.
Since the acceleration sensor is related to the reference signal of the gyroscope, the related signals of the tested acceleration sensor and the gyroscope are as follows:
N ¨1 + r)x a 1,(k)= Fgoro(r)+ Fgon,(r)+ Frono(r)+ Fnon,(r) N k=0 wherein the acceleration signal is irrelevant to the interference noise, so the sum of F (r) F (r) gon, and r n is 0, and the correlation between the external interference received by the tested acceleration sensor and the external interference received by the gyroscope F,, (T) -is very weak, so n' 15 0. Thus, Ao F, F goro(r) = ¨cos(cor + p) Therefore, the output of the tested acceleration sensor suppressing the external interference can be obtained:
go (k) = 2 x Fdo (r) = 4 cos(co +
Date Recue/Date Received 2020-04-30 By using this output signal to calculate the power spectral density, the background noise of the acceleration sensor without interference signals can be obtained in the inherent frequency range.
If the background noise in the directions of +1g and -1g is tested, the acceleration sensor outputs a direct-current slowly-varying signal because the output of the acceleration sensor is not affected by rotation, and the external interference can be filtered by a low-pass filter or a moving average filter When different tested acceleration sensors are subjected to noise tests in different directions, and the sensitive direction of the acceleration sensors is parallel to the X axis or the Y axis, the rotating chassis of the silencing chamber is started to rotate at a certain low frequency, and the tested acceleration sensors and now the reference gyroscope are sampled. Because the output signals of the both are related signals, the interference signals are not related to the output signals, and the interference signals of the both signals are not related to each other, so that the external interference signals can be suppressed.
According to the invention, the environment noise interference is reduced by adopting a passive filtering mode, meeting the background noise test requirement of the high-precision sensor; in order to meet the requirements of the background noise test environment of the acceleration sensor with higher accuracy, it adopts a combination of passive filtering and damping control technology, and corresponding circuit design, control method design and electromagnetic compatibility (EMC) design; and based on the correlation detection method, interference signals in the background noise frequency range of the tested sensor are suppressed to finally obtain a clean background noise result of the tested sensor.
Although the preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concept is known. It is therefore intended that the appended claims be interpreted as including the preferred embodiments and all such changes and modifications as fall within the true scope of the present invention.
Date Recue/Date Received 2020-04-30 It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Date Recue/Date Received 2020-04-30
Claims (10)
1. A device for testing background noise of an acceleration sensor, characterized by comprising a vibration isolation device and a vibration damping system, wherein the vibration isolation device comprises a silencing chamber and a vibration isolation table;
the vibration isolation table comprises an air-floating vibration isolation table and a multi-stage elastic vibration isolation table;
the silencing chamber is internally provided with an accommodating space;
a rotating base is installed on the ground of the silencing chamber, the rotating base rotates uniformly at a determined angular velocity;
the air-floating vibration isolation table is arranged on the rotating base of the silencing chamber and rotates along with the rotating base;
and the multi-stage elastic vibration isolation table is arranged above the air-floating vibration isolation table after being connected in series;
the tested acceleration sensor is arranged on a surface of a bearing vibration isolation table which is located on an uppermost part of the multi-stage elastic vibration isolation table;
the vibration damping system comprises a standard sensor group, a signal detection and conditioning unit, an acquisition unit, a control unit, a driver and a noise processing unit.
the vibration isolation table comprises an air-floating vibration isolation table and a multi-stage elastic vibration isolation table;
the silencing chamber is internally provided with an accommodating space;
a rotating base is installed on the ground of the silencing chamber, the rotating base rotates uniformly at a determined angular velocity;
the air-floating vibration isolation table is arranged on the rotating base of the silencing chamber and rotates along with the rotating base;
and the multi-stage elastic vibration isolation table is arranged above the air-floating vibration isolation table after being connected in series;
the tested acceleration sensor is arranged on a surface of a bearing vibration isolation table which is located on an uppermost part of the multi-stage elastic vibration isolation table;
the vibration damping system comprises a standard sensor group, a signal detection and conditioning unit, an acquisition unit, a control unit, a driver and a noise processing unit.
2. The device for testing the background noise of the acceleration sensor according to claim 1, wherein the air-floating vibration isolation table comprises an air-floating table surface and at least one first-stage supporting leg, the first-stage supporting leg being arranged between the floor of the silencing chamber and the air-floating table surface.
3. The device for testing the background noise of the acceleration sensor according to claim 1, wherein the multi-stage elastic vibration isolation table comprises a plurality of supporting tables and elastic supporting legs, the elastic supporting legs are arranged between the supporting tables, and the elastic supporting legs of the elastic vibration Date Recue/Date Received 2022-01-12 isolation table at a bottommost layer are arranged between the air-floating vibration isolation table and the supporting table at the bottommost layer.
4. The device for testing the background noise of the acceleration sensor according to claim 1, wherein an inflation pump is arranged to inflate the air-floating vibration isolation table.
5. The device for testing the background noise of the acceleration sensor according to claim 1, wherein the silencing chamber has a shockproof frame type of main body structure, and size parameters are as follows: the width is 1-2 meters, the depth is 2-4 meters, and the height is 1-3 meters.
6. The device for testing the background noise of the acceleration sensor according to claim 1, wherein the multi-stage elastic vibration isolation table is a two-stage elastic vibration isolation table.
7. The device for testing the background noise of the acceleration sensor according to claim 1, wherein the standard sensor group comprises a sensor for measuring a change in acceleration of the vibration isolation table, a sensor for measuring a change in angular velocity of the vibration isolation table, and a displacement sensor.
8. The device for testing the background noise of the acceleration sensor according to claim 1, wherein the driver adjusts the vibration isolation table to perform a reverse motion according to data detected by the standard sensor group, thereby further attenuating vibration of the vibration isolation table.
9. A test method based on the device for testing the acceleration background noise as claimed in claim 1, characterized by comprising:
step 1, installing an acceleration sensor to be tested;
step 2, adjusting parameters of the vibration isolation table according to the mass of the acceleration sensor to be tested;
step 3, starting the vibration damping system;
step 4, starting the rotating base to drive the vibration isolation table to rotate;
Date Recue/Date Received 2022-01-12 step 5, enabling that a sensitive axis of the acceleration sensor to be tested is parallel to the Z
axis, and sequentially testing the background noise in a direction of +1g and a direction of -1g;
step 6, enabling that the sensitive axis of the acceleration sensor to be tested is parallel to the X
axis or the Y axis, and testing the background noise in the direction of Og;
and step 7, obtaining an output of the tested acceleration sensor suppressing external interference by calculating a cross-correlation signal.
step 1, installing an acceleration sensor to be tested;
step 2, adjusting parameters of the vibration isolation table according to the mass of the acceleration sensor to be tested;
step 3, starting the vibration damping system;
step 4, starting the rotating base to drive the vibration isolation table to rotate;
Date Recue/Date Received 2022-01-12 step 5, enabling that a sensitive axis of the acceleration sensor to be tested is parallel to the Z
axis, and sequentially testing the background noise in a direction of +1g and a direction of -1g;
step 6, enabling that the sensitive axis of the acceleration sensor to be tested is parallel to the X
axis or the Y axis, and testing the background noise in the direction of Og;
and step 7, obtaining an output of the tested acceleration sensor suppressing external interference by calculating a cross-correlation signal.
10. The method according to claim 9, wherein the rotating frequency of the rotating base is 1-10Hz.
Date Recue/Date Received 2022-01-12
Date Recue/Date Received 2022-01-12
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| CN114499710B (en) * | 2022-04-02 | 2022-06-21 | 成都爱瑞无线科技有限公司 | Background noise change measuring method, background noise change measuring device, background noise change measuring system, electronic device, and storage medium |
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| US5899443A (en) * | 1996-10-22 | 1999-05-04 | The United States Of America As Represented By The Secretary Of The Navy | Passive-active vibration isolation |
| CN101364052B (en) * | 2008-10-08 | 2010-10-27 | 上海微电子装备有限公司 | Active vibration damping system and forecast control method thereof |
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| CN106763464A (en) * | 2017-03-02 | 2017-05-31 | 江苏大学 | A kind of active air vibration isolation unit for micro-vibration technology |
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