Equipment and method for measuring acceleration noise caused by residual gas in inertial sensor

Abstract

The invention discloses a device and method for measuring acceleration noise caused by residual gas in an inertial sensor. The device comprises a test mass block used for simulating a sensitive structure mass block, a suspension wire connected with the test mass block, and a weak force measurement torsion balance used for measuring damping borne by the test mass block. The test mass block is arranged in the vacuum cavity, and the air pressure in the vacuum cavity can be changed; polar plates are arranged on the two sides of the test mass block and move to different positions of the side face of the test mass block so as to simulate gas molecule collision distribution differences caused by lateral gaps and geometric offset changes of the test mass block; an optical read-out system is mounted outside the vacuum cavity, forms an optical measurement link with a reflecting mirror on the outer side of the test mass block through a vacuum pipeline, and is used for continuously recording displacement amplitude and rotation angle data of the test mass block; the method can accurately quantify the contribution of the residual gas to the acceleration noise.

Description

An apparatus and method for measuring acceleration noise caused by residual gas inside an inertial sensor Technical Field

[0001] This invention relates to the technical field of inertial sensor stability testing, specifically to a device and method for measuring acceleration noise caused by residual gas inside an inertial sensor. Background Technology

[0002] In high-vacuum environments, especially in inertial sensors in deep space orbits, a large number of residual gas molecules exist inside. These molecules, due to material efflux and surface adsorption, randomly collide with the test mass, causing stray acceleration. This acceleration is the dominant noise source in the low to mid-frequency range, affecting measurement accuracy, especially in high-vacuum environments where the damping effect of residual gas is more significant. While some research on gas damping has been conducted, accurate measurement and modeling of acceleration noise caused by random gas impacts under high-vacuum conditions remain insufficient, particularly in space environments where differences in vacuum levels and material properties make it difficult to effectively predict the specific contribution of gas damping to acceleration noise. Existing techniques mainly involve measuring random collisions between gas molecules and the test mass using electrostatic levitation accelerometers to estimate the effect of gas damping. By calculating the force exerted by gas molecules on the test mass at different speeds and angles and using the velocity distribution and momentum conservation law of gas molecules, researchers can calculate the force exerted by the gas molecules on the test mass. Existing experimental methods typically obtain the gas damping coefficient by measuring amplitude decay data at different vacuum levels and comparing it with theoretical results.

[0003] Existing gas damping modeling techniques largely rely on static or linearly changing rate distributions, failing to consider the behavior of gas molecules in dynamic environments. This results in measurement results that do not reflect the actual gas damping effect. Existing experimental methods struggle to handle accurate measurements at extremely low pressures. Particularly in high vacuum environments, gas behavior and its impact on the test mass are complex, and existing methods cannot effectively predict these changes. Furthermore, current gas damping measurement methods fail to effectively address the influence of background magnetic field noise on the measurement results, making it difficult to independently identify the contribution of gas damping to acceleration noise. Summary of the Invention

[0004] The purpose of this invention is to provide a device and method for measuring acceleration noise caused by residual gas in an inertial sensor, in order to solve the technical problem in the prior art that the influence of background magnetic field noise on the measurement results is not effectively solved, making it difficult to identify the contribution of gas damping to acceleration noise separately.

[0005] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0006] An acceleration noise measurement device for a test mass block under high vacuum conditions caused by residual gas includes:

[0007] A test mass block for simulating a sensitive structural mass block, a suspension wire connected to the test mass block, and a weak force measuring torsion balance for measuring the damping experienced by the test mass block.

[0008] The test mass block is placed inside a vacuum chamber, and the internal air pressure of the vacuum chamber is 10. -4 Pa to 10 -2 Changes between Pa;

[0009] The test mass block has electrode plates on both sides. The electrode plates are moved to different positions relative to the sides of the test mass block to simulate the differences in gas molecule collision distribution caused by the lateral gap and geometric offset changes of the test mass block.

[0010] An optical readout system is installed outside the vacuum cavity. The optical readout system forms an optical measurement link with the outer reflector of the test mass block through a vacuum pipe. The optical readout system is used to continuously record the displacement amplitude and rotation angle data of the test mass block.

[0011] As a preferred embodiment of the present invention, the electrode plates are mounted on a stable platform, and angular disturbances are applied to the suspended test mass block to move the electrode plates on both sides to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment.

[0012] In addition, the present invention also provides a method for measuring acceleration noise caused by residual gas in a test mass block under high vacuum, comprising:

[0013] Step 100: Construct a gas damping effect model: By considering the force exerted by residual gas molecules on the test mass block at different speeds and collision angles, based on Maxwell's speed distribution function and the law of conservation of momentum, the torque exerted by the residual gas on the test mass block is derived, and a random collision model between residual gas molecules and the test mass block is established.

[0014] Step 200: Verify the gas damping effect model: By adjusting the pumping speed of the vacuum pump, drive the test mass block to make initial motion under different pressures, continuously record the displacement amplitude and rotation angle data of the test mass block under free oscillation, and calculate the damping coefficient and acceleration noise.

[0015] Step 300: Data Processing and Fitting Analysis: Fit the experimental data with the theoretical gas damping effect model to obtain the relationship curve between the damping coefficient and the air pressure. By analyzing the fitting results, evaluate the contribution of gas damping to acceleration noise and further revise the gas damping effect model.

[0016] As a preferred embodiment of the present invention, in step 100, the method for establishing a random collision model between residual gas molecules and the test mass block based on Maxwell's rate distribution function and the law of conservation of momentum is as follows:

[0017] When testing gas damping perpendicular to the direction of motion, the test mass is on the sensitive axis. The velocity relative to the electrode cage is At that time, Within the solid angle it encompasses, the number of surfaces hitting the test mass block per unit time. Above, speed The number of molecules between them is:

[0018] ;

[0019] in The velocity per unit volume of gas molecules escaping from the lower surface of the upper electrode plate (3) is... The number of molecules between them, and we have:

[0020] ;

[0021] in, Let Maxwell's rate distribution function be used.

[0022] According to the law of conservation of momentum The surface of the test mass block The force is:

[0023] ;

[0024] In the formula, The normal unit vector to the upper surface of the test mass block;

[0025] Based on the above formula, the number of particles that escape from the lower surface of the upper electrode plate (3) and hit the upper surface of the test mass block (1) per unit time is obtained. The forces exerted by all gas molecules on this elemental surface are:

[0026]

[0027] The sum of the force vectors exerted on the test mass block (1) by all molecules that escape from the lower surface of the upper electrode plate (3) and the upper surface of the lower electrode plate (3) and hit the upper and lower surfaces of the test mass block per unit time is:

[0028] .

[0029] As a preferred embodiment of the present invention, when testing the gas damping horizontally in the direction of motion, due to the Knuth-Zehnder effect, the side of the test mass block will also be subject to gas damping, resulting in a surface roughness on one side. Above, speed Number of molecules and interaction forces between them:

[0030] ;

[0031] ;

[0032] Based on the above, the number of particles that escape from the surface of the side electrode plate (3) and hit the side surface of the test mass block per unit time can be obtained. The forces exerted by all gas molecules on this elemental surface are:

[0033] :

[0034] Ultimately, we can obtain the sum of the force vectors acting on the sides:

[0035] .

[0036] As a preferred embodiment of the present invention, based on the above calculations of the front and side surfaces, we obtain the total gas damping:

[0037] ;

[0038] The damping coefficient is:

[0039] ;

[0040] The acceleration thermal noise caused by gas damping is:

[0041] .

[0042] As a preferred embodiment of the present invention, by setting a confined environment between the electrode cage and the test mass block, the formula for the damping coefficient of the residual gas after correction is as follows:

[0043] ;

[0044] in, This represents the damping coefficient exerted by the residual gas on the test mass block. This is the effective cavity geometry correction factor. This is the residual gas pressure. To test the length, width, and height of the mass block, Mass of gas molecules For temperature;

[0045] The modified residual rarefied gas is randomly impacted onto a test mass block. The acceleration disturbance caused by the impact is parameterized and modeled to generate a theoretical gas damping effect model:

[0046] ;

[0047] in, To test the quality of the mass block, Boltzmann's constant, For geometric correction factor, This represents the damping coefficient exerted by the residual gas on the test mass block. This refers to ambient pressure.

[0048] As a preferred embodiment of the present invention, in step 200, the method for verifying the implementation of the gas damping effect model is as follows:

[0049] Adjust the vacuum pump speed to reduce the air pressure inside the torsion balance vacuum chamber from arrive The variation between these values ​​corresponds to a molecular path of freedom ranging from 10 km to 10 m, meaning the internal gas molecules are completely in a state of molecular flow. The damping magnitude is determined by measuring the damping under different pressures. Curve, in which, The damping coefficient is... Given the ambient vacuum level, the damping coefficient at this point... Includes air damping and mechanical losses Among them, mechanical wear The contribution is close to a constant;

[0050] ;

[0051] The experimental measurement expression for damping strength is:

[0052] ;

[0053] in, The frequency of the torsion balance is [value], and the amplitude of the selected vibration period of the torsion balance is [value]. and , Let be the moment of inertia of the torsion balance. The statistical gap is specifically the average amplitude attenuation ratio of all vibration cycles.

[0054] As a preferred embodiment of the present invention, when verifying the gas damping effect model, the system ambient vacuum level is adjusted from... arrive The angle of the test mass was changed to vary between the two sides, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm and 20mm respectively for the experiment.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] This invention, through precise gas damping effect modeling and high-precision experimental measurement methods, can accurately quantify the contribution of residual gas to acceleration noise. Theoretical derivation shows that, at a gas pressure of 10⁻⁴ Pa, the error between the experimental gas damping coefficient and the theoretical value is controlled within 10%.

[0057] Accurate prediction and control of acceleration noise. By fitting experimental data and theoretical models, this scheme can accurately predict acceleration noise caused by gas damping under different vacuum conditions. Under high vacuum, the acceleration noise caused by gas damping is less than 10⁻¹⁴ m / s² / Hz⁻¹ / ², which meets the noise performance requirements of inertial sensors. Attached Figure Description

[0058] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0059] Figure 1 is a schematic diagram of the overall structure of the acceleration noise measurement device according to an embodiment of the present invention;

[0060] Figure 2 is a flowchart illustrating the acceleration noise measurement method according to an embodiment of the present invention;

[0061] The labels in the diagram represent the following:

[0062] 1-Test mass block; 2-Suspension wire; 3-Electrode plate; 4-Optical readout system; 5-Stabilizing platform; 6-Weak force measurement torsion balance; 7-Vacuum chamber. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] As shown in Figure 1, this invention provides a device for measuring acceleration noise caused by residual gas in a test mass block under high vacuum. The device includes a test mass block 1 for simulating a sensitive structural mass block, a suspension wire 2 connected to the test mass block 1, and a weak force measuring torsion balance 6 for measuring the damping experienced by the test mass block 1. The test mass block 1 is placed inside a vacuum chamber 7, and the internal gas pressure of the vacuum chamber 7 is 10... -4 Pa to 10 -2 Variations between Pa.

[0065] The test mass block 1 has electrode plates 3 on both sides. The electrode plates 3 are moved to different positions relative to the sides of the test mass block 1 to simulate the differences in gas molecule collision distribution caused by changes in the lateral gap and geometric offset of the test mass block 1.

[0066] An optical readout system 4 is installed on the outside of the vacuum chamber 7. The optical readout system 4 forms an optical measurement link with the outer reflector of the test mass block 1 through the vacuum pipe. The optical readout system 4 is used to continuously record the displacement amplitude and rotation angle data of the test mass block 1.

[0067] The electrode plate 3 is installed on the stable platform 5. An angular disturbance is applied to the suspended test mass block 1, and the electrode plates 3 on both sides are moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm and 20mm respectively for the experiment.

[0068] The test method for residual gas noise is as follows: the damping of the test mass block 1 in the electrode cage is measured using a weak force measuring torsion balance 6. The physical laws are extrapolated by combining the actual internal dimensions and pressure of the inertial sensor to obtain the damping coefficient and corresponding acceleration noise under working conditions. The noise level is obtained by fitting the relationship curve between the damping coefficient and the pressure.

[0069] The suspension wire 2 is made of high-Q quartz fiber, which serves as a flexible support for the weak force measurement torsion balance 6 and provides single-degree-of-freedom torsional motion. Therefore, under conditions of extremely low mechanical loss, the free oscillation decay of the test mass block 1 is almost entirely determined by gas damping. Furthermore, by using the suspension wire 2, the non-contact suspension state of the test mass block in the electrode cage in the actual inertial sensor is simulated, making the damping source equivalent to the effect of residual gas.

[0070] The weak force measurement torsion balance 6 extracts the damping coefficient by recording the free oscillation decay curve of the test mass block 1. It is mainly used for high-sensitivity measurement of the extremely small damping force and torque on the test mass block 1. The gas damping force measured by the weak force measurement torsion balance 6 is directly equivalent to the acceleration noise caused by the random impact of residual gas during the operation of the accelerometer.

[0071] The electrode 3 adjusts the lateral gap and internal geometric constraints between itself and the test mass block 1 through the relative movement of the stable platform 5. This is mainly used to change the reflection path of residual gas molecules, the collision solid angle and the momentum exchange probability, and to reproduce the gas damping changes caused by different manufacturing deviations of the real inertial sensor step by step.

[0072] The air pressure inside the vacuum chamber 7 is 10⁻ 4 Adjustable from Pa to 10⁻² Pa, it is used to construct a rarefied gas momentum exchange model under the condition that the molecular free path is ≫ gap, providing a molecular flow vacuum environment consistent with the interior of the deep space payload, and realistically reproducing the residual gas noise-dominated mechanism in the vacuum inertial sensor.

[0073] The specific working method of the above-mentioned acceleration measurement device is as follows: electrostatic driving excitation is applied to the electrode cage under different vacuum conditions, the displacement amplitude and rotation angle of the sensitive structure are tested, the damping coefficient is then calculated, and the residual gas noise level is evaluated by fitting the damping coefficient-pressure relationship curve.

[0074] This embodiment obtains the damping coefficient under different pressure and gap conditions by applying an initial angular perturbation and recording the free decay time-series curve of test mass 1. Then, the acceleration noise spectral density caused by residual gas is calculated according to the gas damping thermal noise model. Through model fitting, the mechanical loss and gas damping contribution can be separated, and the random collision theory between gas molecules and test mass can be corrected. Therefore, this invention can directly quantify the force noise contribution of residual rarefied gas to sensitive structures and has experimental equivalence that is highly consistent with the on-orbit operation conditions in space.

[0075] The inertial sensor is located in a high-vacuum deep-space orbit. Due to factors such as the gas escaping effect of the material, a large number of residual gas molecules will be present inside the sensing structure, specifically in the cavity between the electrode cage and the test mass. The stray acceleration caused by the random collisions of these residual gas molecules with the test mass results in white noise in the noise power spectrum.

[0076] The measurement method for the acceleration noise caused by residual gas in the test mass block under high vacuum conditions, as shown in Figure 2, specifically includes:

[0077] Step 100: Construct a gas damping effect model: By considering the force exerted by residual gas molecules on the test mass block at different speeds and collision angles, and based on Maxwell's speed distribution function and the law of conservation of momentum, the torque exerted by the residual gas on the test mass block is derived, and a random collision model between the residual gas molecules and the test mass block is established.

[0078] Based on Maxwell's rate distribution function and the law of conservation of momentum, when establishing a random collision model between residual gas molecules and the test mass block, the gas damping of the front and rear surfaces (i.e., perpendicular to the direction of motion), the gas damping of the side surfaces (i.e., parallel to the direction of motion), and the gas damping of the top and bottom surfaces (parallel to the direction of motion) of the test mass block are calculated. The specific implementation method is as follows:

[0079] When testing gas damping perpendicular to the direction of motion, the test mass is on the sensitive axis. The velocity relative to the electrode cage is At that time, Within the solid angle it encompasses, the number of surfaces hitting the test mass block per unit time. Above, speed The number of molecules between them is:

[0080] ;

[0081] in The velocity per unit volume of gas molecules escaping from the lower surface of the upper electrode plate (3) is... The number of molecules between them, and we have:

[0082] ;

[0083] in, Let Maxwell's rate distribution function be used.

[0084] According to the law of conservation of momentum The surface of the test mass block The force is:

[0085] ;

[0086] In the formula, The normal unit vector to the upper surface of the test mass block;

[0087] Based on the above formula, the number of particles that escape from the lower surface of the upper electrode plate and hit the upper surface of the test mass block (1) per unit time is obtained. The forces exerted by all gas molecules on this elemental surface are:

[0088] ;

[0089] The vector sum of the forces exerted on the test mass block by all molecules escaping from the lower surface of the upper electrode plate and the upper surface of the lower electrode plate, respectively, and hitting the upper and lower surfaces of the test mass block per unit time, is obtained as follows:

[0090] .

[0091] When testing gas damping in the direction of motion, due to the Knuth-Zehnder effect, the side of the test mass will also be damped by gas, resulting in a surface roughness on one side. Above, speed Number of molecules and interaction forces between them:

[0092] ;

[0093] ;

[0094] Based on the above, the number of particles that escape from the surface of the side electrode plate (3) and hit the side surface of the test mass block per unit time can be obtained. The forces exerted by all gas molecules on this elemental surface are:

[0095] :

[0096] Ultimately, we can obtain the sum of the force vectors acting on the sides:

[0097] .

[0098] Similarly, the vector sum of the forces acting on the upper and lower surfaces:

[0099] .

[0100] Based on the calculations from the front and side views above, we obtain the total gas damping:

[0101] ;

[0102] The damping coefficient is:

[0103] ;

[0104] The acceleration thermal noise caused by gas damping is:

[0105] .

[0106] To compare the effects of different sensitive structural dimensions on gas damping, we substituted the design parameters of a typical electrostatic levitation accelerometer and an inertial sensor into the formulas, and further illustrated the applicability of the formulas by referring to results from existing literature. Substituting the design parameters of a typical electrostatic levitation accelerometer into the corresponding formulas: , , , , , , Maximum temperature difference within the sensitive structure , .

[0107] ;

[0108] Analogous to the Johnson-Nyguist noise formula for the resistive thermal noise of an RLC resonator: The acceleration thermal noise caused by gas damping is:

[0109]

[0110] Substitute the design parameters and corresponding formulas for the inertial sensor: , , , , , , Maximum temperature difference within the sensitive structure , , :

[0111]

[0112]

[0113] The above results show the damping effect of residual gas in an infinite environment (without the electrode cage). Existing experiments show that the residual gas force is several times higher in a finite environment than in an infinite environment. This conclusion actually does not match the fitting data from the LISA PathFinder on-orbit measurements. Therefore, in a finite, small-interval environment, the correction for the gas damping effect is one of the key parameters to be measured.

[0114] Due to the confined environment between the electrode cage and the test mass block, the corrected formula for the damping coefficient of the residual gas is as follows:

[0115] ;

[0116] Among them, the gas damping coefficient (translation) ratio is ;in, This represents the damping coefficient exerted by the residual gas on the test mass block. This is the effective cavity geometry correction factor. This is the residual gas pressure. To test the length, width, and height of the mass block, Mass of gas molecules For temperature; Geometric correction factor

[0117] The modified residual rarefied gas is randomly impacted onto a test mass block. The acceleration disturbance caused by the impact is parameterized and modeled to generate a theoretical gas damping effect model:

[0118] ;

[0119] in, To test the quality of the mass block, Boltzmann's constant, For geometric correction factor, This represents the damping coefficient exerted by the residual gas on the test mass block. This refers to the ambient vacuum level.

[0120] Step 200: Verify the gas damping effect model: By adjusting the pumping speed of the vacuum pump, drive the test mass block to make initial movements under different pressures, continuously record the displacement amplitude and rotation angle data of the test mass block under free oscillation, and calculate the damping coefficient and acceleration noise.

[0121] Step 300: Data Processing and Fitting Analysis: Fit the experimental data with the theoretical gas damping effect model to obtain the relationship curve between the damping coefficient and the air pressure. By analyzing the fitting results, evaluate the contribution of gas damping to acceleration noise and further revise the gas damping effect model.

[0122] Specifically, the geometric correction factor is obtained through least squares fitting. With mechanical loss item This method enables quantitative correction of the model. It can separate the contribution of residual gas damping from mechanical loss and verify the applicability of the theoretical model to different gap conditions, thereby obtaining accurate modeling results of gas damping effect.

[0123] In step 200, the experimental verification model used is specifically a noise model of the residual gas random impact test mass.

[0124] The method for verifying the implementation of the gas damping effect model is as follows:

[0125] Adjust the vacuum pump speed to reduce the air pressure inside the torsion balance vacuum chamber from arrive The gas damping coefficient varies between different vacuum levels, and the corresponding molecular free path is 10 km to 10 m.

[0126] Under different vacuum conditions, different electrode spacings, and rarefied molecular flow conditions, random collisions of residual gas can excite measurable free micro-oscillations.

[0127] That is, the internal gas molecules are completely in a state of molecular flow, and the damping is obtained by measuring the magnitude of damping under different pressures. curve, The P-curve reflects the effect of residual gas density change on damping strength during construction. When plotting the –P curve, pressure P represents the actual measured residual gas pressure inside the vacuum chamber (ambient vacuum level), monitored in real-time by a vacuum gauge, and is independent of the electrode position. The damping coefficient is... Given the ambient vacuum level, the damping coefficient at this point... Includes air damping and mechanical losses ;

[0128] ;

[0129] The experimental measurement expression for damping strength is:

[0130] ;

[0131] in, The frequency of the torsion balance is [value], and the amplitude of the selected vibration period of the torsion balance is [value]. and , Given the moment of inertia of the torsion balance, the damping coefficient of the torsion balance can be calculated based on the above parameters.

[0132] The above physical quantities include both measured and set values. The combined accuracy requirements of these values ​​must be... The accuracy meets the above requirements. The signal format is:

[0133]

[0134] The period of the amplitude decay free torsion balance is The moment of inertia of the inertial element is Suspension wire stiffness: .

[0135] Since it is difficult to achieve the vacuum level required for inertial sensors in space during ground-based verification experiments, it is necessary to extrapolate to obtain the damping coefficient under an even lower vacuum. Substituting the corresponding parameters of the torsion balance inertial element: , h , , , , Mechanical wear If the contribution is close to a constant, then:

[0136] ;

[0137] Acceleration thermal noise caused by gas damping:

[0138] ;

[0139] This acceleration noise is exactly within the range of acceleration noise that can be measured by the torsion balance.

[0140] In actual simulation work, the specific experimental steps for conducting simulation tests on acceleration noise testing equipment are as follows:

[0141] Assembly and testing preparation.

[0142] Set the system environment vacuum level to maintain 1. 10 -2 Pa was applied to the suspended test mass block, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment. An optical readout system was used to continuously record the displacement amplitude and rotation angle data of the sensitive structure, with a recording time of no less than [time value missing] for each position. The experimental data were segmented and averaged.

[0143] Set the system environment vacuum level to 5. 10 -2 Pa was applied to the suspended test mass block, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment. An optical readout system was used to continuously record the displacement amplitude and rotation angle data of the sensitive structure, with a recording time of no less than [time value missing] for each position. The experimental data were segmented and averaged.

[0144] Set the system environment vacuum level to maintain 1. 10 -3 Pa was applied to the suspended test mass block, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment. An optical readout system was used to continuously record the displacement amplitude and rotation angle data of the sensitive structure, with a recording time of no less than [time value missing] for each position. The experimental data were segmented and averaged.

[0145] Set the system environment vacuum level to 5. 10 -3 Pa was applied to the suspended test mass block, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment. An optical readout system was used to continuously record the displacement amplitude and rotation angle data of the sensitive structure, with a recording time of no less than [time value missing] for each position. The experimental data were segmented and averaged.

[0146] Set the system environment vacuum level to maintain 1. 10 -4 Pa was applied to the suspended test mass block, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment. An optical readout system was used to continuously record the displacement amplitude and rotation angle data of the sensitive structure, with a recording time of no less than [time value missing] for each position. The experimental data were segmented and averaged.

[0147] Set the system environment vacuum level to maintain 3. 10 -4 Pa was applied to the suspended test mass block, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment. An optical readout system was used to continuously record the displacement amplitude and rotation angle data of the sensitive structure, with a recording time of no less than [time value missing] for each position. The experimental data were segmented and averaged.

[0148] Set the system environment vacuum level to 5. 10 -4 Pa was applied to the suspended test mass block, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm, and 20mm respectively for the experiment. An optical readout system was used to continuously record the displacement amplitude and rotation angle data of the sensitive structure, with a recording time of no less than [time value missing] for each position. The experimental data were segmented and averaged.

[0149] The test data is processed and analyzed to assess the noise level of the residual gas test.

[0150] The positional changes of the two electrode plates relative to the test mass are used to simulate different lateral clearance states between the test mass and the electrode cage in a space inertial sensor, including conditions such as manufacturing and assembly errors, positional offset, and attitude deflection. The lateral clearance determines the scattering path and effective collision solid angle of residual gas molecules, thus significantly affecting the magnitude of gas damping. Therefore, by changing the clearance between the electrode plates and the test mass, a functional dependence between gas damping and lateral geometric constraints can be established, achieving an equivalent simulation and quantitative characterization of the contribution of gas damping inside the real sensitive structure.

[0151] During the experiment, for pressure of In the initial case, the angle by which the torsion balance is deviated from the equilibrium position is... It swings freely, and the amplitude data of the torsion balance is recorded in each cycle, and the intervals are statistically analyzed. The amplitude attenuation ratio for each cycle is calculated and averaged. The duration of this measurement is... Approximately 12 hours. The attenuation ratio of the amplitude is calculated over 10 period intervals, yielding the damping coefficient as follows: , compared with theoretical value The relative error is 6.3%.

[0152] For pressure is Under maximum damping, calculations show that the amplitude of rotation will be less than [a certain value] after approximately 10 cycles. The resolution of the measuring device is close to that of the measurement equipment, which increases the uncertainty of the measurement.

[0153] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A device for measuring acceleration noise caused by residual gas in a test mass block under high vacuum, characterized in that, include: A test mass block (1) for simulating a sensitive structural mass block, a suspension wire (2) connected to the test mass block (1), and a weak force measuring torsion balance (6) for measuring the damping experienced by the test mass block (1); the test mass block (1) is placed inside a vacuum chamber (7), and the air pressure inside the vacuum chamber (7) is 10. -4 Pa to 10 -2 The test mass block (1) is provided with electrode plates (3) on both sides. The electrode plates (3) are moved to different positions relative to the side of the test mass block (1) to simulate the differences in gas molecule collision distribution caused by the lateral gap and geometric offset changes of the test mass block (1). An optical readout system (4) is installed outside the vacuum chamber (7). The optical readout system (4) forms an optical measurement link with the outer reflector of the test mass block (1) through a vacuum pipe. The optical readout system (4) is used to continuously record the displacement amplitude and rotation angle data of the test mass block (1).

2. The device for measuring acceleration noise caused by residual gas in a test mass block under high vacuum as described in claim 1, characterized in that, The electrode plate (3) is installed on the stable platform (5). An angular disturbance is applied to the suspended test mass block (1). The electrode plates (3) on both sides are moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm and 20mm respectively for the experiment.

3. A method for measuring acceleration noise caused by residual gas in a test mass block under high vacuum, based on the device described in any one of claims 1-2, characterized in that, include: Step 100: Constructing a gas damping effect model: By considering the force exerted by residual gas molecules on the test mass block at different speeds and collision angles, and based on Maxwell's speed distribution function and the law of conservation of momentum, the torque exerted by the residual gas on the test mass block is derived, and a random collision model between the residual gas molecules and the test mass block is established. Step 200: Verifying the gas damping effect model: By adjusting the vacuum pump speed, the test mass block is driven to undergo initial motion under different pressures. The displacement amplitude and rotation angle data of the test mass block under free oscillation are continuously recorded, and the damping coefficient and acceleration noise are calculated. Step 300: Data processing and fitting analysis: The experimental data are fitted with the theoretical gas damping effect model to obtain the relationship curve between the damping coefficient and the gas pressure. By analyzing the fitting results, the contribution of gas damping to acceleration noise is evaluated, and the gas damping effect model is further modified.

4. The measurement method according to claim 3, characterized in that, In step 100, based on Maxwell's rate distribution function and the law of conservation of momentum, the method for establishing a random collision model between residual gas molecules and the test mass block is as follows: when testing gas damping perpendicular to the direction of motion, the test mass block is on the sensitive axis The velocity relative to the electrode cage is At that time, Within the solid angle it encompasses, the number of surfaces hitting the test mass block per unit time. Above, speed The number of molecules between them is: ;in The velocity per unit volume of gas molecules escaping from the lower surface of the upper electrode plate (3) is... The number of molecules between them, and we have: ;in, Let Maxwell's speed distribution function be denoted by ; according to the law of conservation of momentum, The surface of the test mass block The force is: In the formula, The normal unit vector of the upper surface of the test mass block is given by the above formula; the elemental surface that escapes from the lower surface of the upper electrode plate (3) and hits the upper surface of the test mass block (1) per unit time is obtained. The forces exerted by all gas molecules on this elemental surface are: The sum of the force vectors exerted on the test mass block (1) by all molecules that escape from the lower surface of the upper electrode plate (3) and the upper surface of the lower electrode plate (3) and hit the upper and lower surfaces of the test mass block per unit time is: 。 5. The measurement method according to claim 4, characterized in that, When testing gas damping in the direction of motion, due to the Knuth-Zehnder effect, the side of the test mass will also be damped by gas, resulting in a surface roughness on one side. Above, speed Number of molecules and interaction forces between them: ； Based on the above, the number of particles that escape from the surface of the side electrode plate (3) and hit the side surface of the test mass block per unit time can be obtained. The forces exerted by all gas molecules on this elemental surface are: Ultimately, we can obtain the sum of the force vectors acting on the sides: 。 6. The measurement method according to claim 7, characterized in that, Based on the calculations from the front and side views above, we obtain the total gas damping: ； The damping coefficient is: The acceleration thermal noise caused by gas damping is: 。 7. The measurement method according to claim 6, characterized in that, By setting a finite environment between the electrode cage and the test mass block, the formula for the damping coefficient of the residual gas, after correction, is as follows: ;in, This represents the damping coefficient exerted by the residual gas on the test mass block. This is the effective cavity geometry correction factor. This is the residual gas pressure. To test the length, width, and height of the mass block, Mass of gas molecules For temperature; the corrected residual rarefied gas is randomly impacted onto a test mass block, and the acceleration disturbance caused by the impact is parameterized and modeled to generate a theoretical gas damping effect model: ;in, To test the quality of the mass block, Boltzmann's constant, For geometric correction factor, This represents the damping coefficient exerted by the residual gas on the test mass block. This refers to ambient pressure.

8. The measurement method according to claim 3, characterized in that, In step 200, the method for verifying the implementation of the gas damping effect model is as follows: adjust the pumping speed of the vacuum pump to make the gas pressure inside the torsion balance vacuum chamber from arrive The variation between these values ​​corresponds to a molecular path of freedom ranging from 10 km to 10 m, meaning the internal gas molecules are completely in a state of molecular flow. The damping magnitude is determined by measuring the damping under different pressures. Curve, in which, The damping coefficient is... Given the ambient vacuum level, the damping coefficient at this point... Includes air damping and mechanical losses Among them, mechanical wear The contribution is close to a constant; The experimental expression for damping strength is: ;in, The frequency of the torsion balance is [value], and the amplitude of the selected vibration period of the torsion balance is [value]. and ， Let be the moment of inertia of the torsion balance. The statistical gap is specifically the average amplitude attenuation ratio of all vibration cycles.

9. The measurement method according to claim 8, characterized in that, In step 200, when verifying the gas damping effect model, the ambient vacuum level of the system is adjusted from... arrive The angle of the test mass was changed to vary between the two sides, and the two side plates were moved to positions of 1mm, 2mm, 3mm, 4mm, 5mm, 10mm, 15mm and 20mm respectively for the experiment.

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