WO2023201936A1

WO2023201936A1 - Accelerometer

Info

Publication number: WO2023201936A1
Application number: PCT/CN2022/112213
Authority: WO
Inventors: 范玉娇; 常密生; 杨月舳
Original assignee: 北京华卓精科科技股份有限公司
Priority date: 2022-04-18
Filing date: 2022-08-12
Publication date: 2023-10-26
Also published as: CN114966105B; CN114966105A

Abstract

An accelerometer, relating to the technical field of inertia measurement instruments, and comprising: a laser interferometer, an instrument head, and an acceleration resolving module. The instrument head comprises: a housing (1), a mass block (2), and an elastic support member (3); the mass block (2) is arranged inside the housing (1), and the mass block (2) is connected to the housing (1) by means of the elastic support member (3); the housing (1) is fixedly connected to an object to be tested; the laser interferometer is used for generating reference light and measurement light; the measurement light is transmitted to the interior of the housing (1) by means of an optical fiber (9), and is emitted to the surface of the mass block (2); the surface of the mass block (2) is used for reflecting measurement light to form reflected light; the laser interferometer is further used for receiving the reflected light and making the reflected light interfere with the reference light to form interference light; the laser interferometer is further used for converting the interference light into an interference signal and sending the interference signal to the acceleration resolving module for resolving so as to obtain an acceleration value of the object.

Description

an accelerometer

Cross-references to related applications

This disclosure claims the priority of Chinese patent application CN202210402846.2 titled "An Accelerometer" submitted on April 18, 2022, the entire content of which is incorporated into this disclosure by reference.

Technical field

The present disclosure relates to the technical field of inertial detection instruments, and in particular to an accelerometer.

Background technique

Accelerometers are widely used in inertial guidance, robot posture measurement, automobile inertial positioning and other occasions. Since the measured acceleration is directly used to calculate the object's position, attitude, velocity and other state quantities, its measurement accuracy has become one of the most important indicators for measuring the technical level of the accelerometer.

According to different detection principles, accelerometers in related technologies include acceleration measurement solutions such as measuring elastomer strain based on strain gauges, measuring stress based on piezoelectric ceramics, measuring inertial mass displacement based on the capacitance principle, and measuring inertial mass displacement based on the electromagnetic induction principle. However, due to the resistor heating effect, piezoelectric sensor nonlinearity, capacitance nonlinearity, magnetic field nonlinearity and other characteristics, there are non-negligible nonlinear errors in the above solutions, which limits the measurement accuracy of the accelerometer.

In addition, the acceleration solution also directly affects the measurement results. The accuracy of acceleration calculation in related technologies depends on the accuracy of the installation position of the detection unit in the accelerometer, and processing and installation errors are difficult to be accurately compensated.

The above defects all cause the measurement results of the accelerometers in the related art to be inaccurate enough and cannot meet the measurement accuracy requirements of the accelerometers.

Contents of the invention

In view of the above-mentioned problems in the related technologies, the present disclosure proposes an accelerometer, which can effectively reduce the nonlinear errors existing in the related technologies and obtain more accurate acceleration measurement results.

In order to achieve the above objectives, the technical solution of the present disclosure is implemented as follows: An embodiment of the present disclosure provides an accelerometer, including: a laser interferometer, a meter head and an acceleration calculation module; the meter head includes: a housing, a mass block and Elastic support; the mass block is arranged inside the housing, and the mass block and the housing are connected through the elastic support; the housing is used to be fixedly connected to the object to be measured; the laser interferometer is used to generate reference light and measurement light; measurement light It is transmitted to the inside of the housing through the optical fiber and emitted to the surface of the mass block; the surface of the mass block is used to reflect the measurement light to form reflected light; the laser interferometer is also used to receive the reflected light and interfere with the reference light to form interference light ; The laser interferometer is also used to convert the interference light into an interference signal and send it to the acceleration calculation module; the acceleration calculation module is used to calculate the received interference signal and obtain the acceleration value of the object to be measured.

Description of the drawings

The scope of the present disclosure may be better understood by reading the following detailed description of exemplary embodiments in conjunction with the accompanying drawings. The accompanying drawings included are:

Figure 1 is a schematic diagram of the system structure of an embodiment of the present disclosure.

Explanation of reference signs

1- Shell 2- Mass block 3- Elastic support 4- Polarizing beam splitter

5-First quarter-wave plate 6-Second quarter-wave plate 7-Reflector

8-First collimator 9-Optical fiber 10-Second collimator 11-Third collimator

Detailed ways

In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the implementation method of the present disclosure will be described in detail below in conjunction with the drawings and examples, whereby the present disclosure applies technical means to solve technical problems and achieve technical effects. The process is fully understood and implemented accordingly.

Many specific details are set forth in the following description to fully understand the present disclosure. However, the present disclosure may also be implemented in other ways than those described here. Therefore, the protection scope of the present disclosure is not limited by the specific implementation disclosed below. Example limitations.

This disclosure proposes an accelerometer based on laser interference redundant measurement, which is suitable for high-precision measurement of low-frequency acceleration. The accelerometer uses a laser interferometer to redundantly measure the displacement of the mass block in the meter head, and solves the optical path model equations containing redundant information according to a specific solution algorithm to achieve multi-axis acceleration decoupling and high-precision solution , thereby solving the problem of non-linear errors in the measurement results of accelerometers based on laser interference displacement measurement in related technologies, which is beneficial to improving the accuracy and resolution of acceleration measurement.

Based on the above ideas, the embodiment of the present disclosure provides an accelerometer, as shown in Figure 1, including: a laser interferometer, a meter head and an acceleration calculation module; the meter head includes: a housing 1, a mass block 2 and an elastic support member 3; The mass block 2 is arranged inside the housing 1, and the mass block 2 and the housing 1 are connected through an elastic support 3; the housing 1 is used to be fixedly connected to the object to be measured. In one embodiment, the housing 1 can Rigidly fixed on the surface of the object to be measured; the laser interferometer is used to generate reference light and measurement light; the measurement light is transmitted to the inside of the housing 1 through the optical fiber and emitted to the surface of the mass block 2; the surface of the mass block 2 is used to reflect the measurement light to form a reflection Light; the laser interferometer is also used to receive reflected light and interfere with the reference light to form interference light; the laser interferometer is also used to convert the interference light into an interference signal and send it to the acceleration calculation module; The acceleration calculation module is used to calculate the received interference signal and obtain the acceleration value of the object to be measured.

In one embodiment, in a connection method between the housing 1, the mass 2, the elastic support 3 and the object to be measured, when the object to be measured has acceleration, the mass 2 can produce a six-dimensional rotation relative to the housing 1. Degrees of freedom displacement; among them, the six degrees of freedom include: the movement degrees of freedom along the three rectangular coordinate axes of X, Y, and Z, and the rotational degrees of freedom around the three rectangular coordinate axes of X, Y, and Z respectively. The accelerometer provided in this embodiment is a six-dimensional accelerometer that can realize simultaneous measurement of three-axis acceleration and three-axis angular acceleration.

In this embodiment, there is at least one elastic support member 3; the mass block 2 is in the shape of a regular hexahedron; each surface of the mass block 2 is connected to the inner wall of the housing 1 through the elastic support member 3 corresponding to that surface. Of course, the mass block 2 can also be in other shapes such as a rectangular parallelepiped, a sphere, an ellipsoid, etc., which is not specifically limited in this embodiment.

In one embodiment, as shown in Figure 1, when the mass block 2 is in the shape of a regular hexahedron, the elastic support member 3 corresponds to each side of the mass block 2, and each side of the mass block 2 passes through an elastic support member. 3 is connected to the inner wall of the housing 1. In this way, when the object to be measured fixedly connected to the housing 1 has acceleration, the mass 2 can produce a six-degree-of-freedom displacement relative to the housing 1. This displacement is detected by a laser interferometer. Afterwards, the acceleration value corresponding to the displacement can be calculated through the acceleration calculation module.

In this embodiment, the mass block 2 can be used to carry the inertial force caused by the acceleration to be measured, thereby producing a tendency of six degrees of freedom displacement relative to the housing 1. At the same time, the mass block 2 is also used to reflect the force generated by the laser interferometer. of measuring light. In order to reflect the measurement light more effectively, in this embodiment, the surface of the mass block 2 is coated with a laser reflective film. The elastic support 3 can be used to provide a restoring force that makes the mass 2 tend to return to the force equilibrium position when the mass 2 and the housing 1 are relatively displaced or the mass 2 deviates from the force equilibrium position.

In this embodiment, as shown in Figure 1, the laser interferometer includes: a laser source, an interference lens group and a signal processing board; the interference lens group includes: a polarizing beam splitter 4, a first quarter-wave plate 5, a second fourth Quarter-wave plate 6 and reflector 7; the laser light generated by the laser source is divided into reference light and measurement light by polarizing beam splitter 4; after the reference light passes through the first quarter-wave plate 5, it is reflected by the reflector 7 Return along the original optical path; after the measurement light passes through the second quarter-wave plate 6, it enters the optical fiber 9 through the first collimator 8, is transmitted to the inside of the housing 1 through the optical fiber 9, and exits through the second collimator 10. The surface of the mass block 2; the reflected light enters the optical fiber 9 through the second collimator 10 and returns along the original optical path; the interference light enters the signal processing board through the third collimator 11, and is converted into an interference signal by the signal processing board and sent to the acceleration solution calculation module.

In order to more effectively calculate the interference signal obtained by the laser interferometer and obtain more accurate calculation results, in this embodiment, the mass block 2 is set in the shape of a regular hexahedron. When the mass block 2 is in the shape of a regular hexahedron, the measurement light generated by the laser interferometer is emitted through the second collimator 10 to at least two adjacent three surfaces of the mass block 2, so that more effective interference signals can be obtained later.

In this embodiment, there are N interference lens groups, where N>6; the laser generated by the laser source is transmitted to each interference lens group through N optical fibers to form N channels of interference light; the signal processing board is also used to N channels of interference light are converted into N channels of interference signals and then sent to the acceleration calculation module.

Figure 1 shows the situation where nine channels of measurement light are emitted to the surface of mass block 2. In this case, the signal processing board can receive nine channels of interference light, and then convert it into nine channels of interference signals for the acceleration calculation module to solve. Calculate.

In one embodiment, in the laser interferometer, the laser light generated by the laser source is transmitted to N interference lens groups through N (N>6) optical fibers, and is divided into N channels of reference light and N channels of measurement through the polarizing beam splitter 4 Light; after each reference light passes through the first quarter-wave plate 5, it is reflected by the reflector 7 and then returns along the original optical path. It passes through the first quarter-wave plate 5 twice so that the polarization direction of the reference light is deflected by 90°. ; After each measurement light passes through the second quarter-wave plate 6, it enters the optical fiber 9 connected to the meter head through the first collimator 8, and passes through the second collimator 10 installed on the meter head housing 1. It is emitted, reflected at different positions on the surface of the mass block 2 and then returns along the original path. It passes through the second quarter-wave plate 6 twice so that the polarization direction of the measurement light is deflected by 90°; the returned reference light interferes with the returned measurement light. N beams of interference light are formed, which are received by the signal processing board; after receiving the N beams of interference light, the signal processing board obtains N-channel interference signal digital quantities through photoelectric conversion and analog-to-digital conversion, which includes six freedoms of the coupled mass block relative to the shell. degree displacement information, that is, it includes coupled six-dimensional acceleration information to be measured.

After receiving the N-channel interference signal digital quantity generated by the signal processing board, the acceleration solution module processes it according to the corresponding acceleration decoupling algorithm to obtain the six-dimensional acceleration value.

In this embodiment, the acceleration calculation module uses the following method to calculate the received interference signal to obtain the acceleration value of the object to be measured.

Step 1: Substitute N interference signals V _i (i=1,2,...,N) into the optical path model equations to obtain the first equations:

Among them, V _i is the i-th interference signal, i=1,2,3...,N; X is the six degrees of freedom displacement of the mass block relative to the coordinate origin, where the coordinate origin is the mass block without acceleration input The position of the center of mass; P _i is the position parameter of the second collimator corresponding to the i-th interference signal, obtained by pre-calibration; ε _i is the noise signal of the i-th interference signal; F _i (·) is the i-th interference signal The optical path model function, the output of this function is the optical path difference between the i-th measurement light and the i-th reference light.

In one implementation, each geometric quantity in this embodiment takes the housing 1 as the reference system, and the position of the center of mass of the mass block 2 when there is no acceleration input is the coordinate origin O; X=[u, v, w, θ _x ,θ _y ,θ _z ] ^T is the six-degree-of-freedom displacement of the mass block 2 relative to the coordinate origin O (the quantity to be solved); P _i =[x _i ,y _i ,z _i ,l _i ] ^T is the relationship with the i-th The position parameter (to be quantified) of the second collimator corresponding to the path interference signal, in one embodiment, may include: the coordinates of the second collimator, and the emitting laser direction vector of the second collimator. Since the second collimator is fixedly installed on the rigid shell, P _i does not change with changes in acceleration input; ε _i is the noise signal of the i-th interference signal (to be quantified); F _i (·) is the i-th interference signal Optical path model function, the input quantity of this function is [X,P _i ], and the output quantity is the optical path difference between the i-th measurement light and the i-th reference light in Figure 1. Because regardless of whether there is acceleration input, any [X, P _i ] are uniquely corresponding to a set of mass block positions, the coordinates of the second collimator and the outgoing laser direction vector of the second collimator. At this time, the optical path of the measurement light in Figure 1 is also uniquely determined, and is determined by the reference Since the optical path of light is fixed, it can be seen that F _i (·) can be uniquely determined based on geometric relations.

Step 2: Use the least squares method to solve the first set of equations to obtain the six-degree-of-freedom displacement of the mass block relative to the coordinate origin.

In one embodiment, the position parameter Pi of the second collimator obtained by self _- calibration is substituted into the above-mentioned first system of equations, and a nonlinear system of equations solving algorithm based on least squares (i.e., the least squares method) is used to solve the above-mentioned first system of equations. The system of equations is solved by minimizing

In order to optimize the target, the solution of the six-degree-of-freedom displacement X=[u, v, w, θ _x , θ _y , θ _z ] ^T of the mass block relative to the coordinate origin when the target is reached is obtained.

Step 3: Calculate the product of the six-degree-of-freedom displacement of the mass block relative to the coordinate origin and the pre-calibrated stiffness matrix to obtain the acceleration value of the object to be measured.

In one embodiment, the six-dimensional acceleration A is obtained by multiplying the solved six-degree-of-freedom displacement X=[u, v, w, θ _x , θ _y , θ _z ] ^T by the stiffness matrix K relative to the coordinate origin. =[a _x , a _y , a _z , β _x , β _y , β _z ], that is, the acceleration value of the object to be measured. In one embodiment, the expression can be: A=K·X, where the stiffness matrix K is a pair of diagonal matrices, the values of the diagonal elements of which are determined by the standard acceleration of the accelerometer on a test bench that can produce six-dimensional standard acceleration. In the input test, the six-dimensional standard acceleration is divided by the six-degree-of-freedom displacement in sequence.

In this embodiment, the least squares method is used to solve the first set of equations to obtain the six-degree-of-freedom displacement of the mass relative to the coordinate origin, which includes the following steps S1 to S4.

S1: Rewrite the first set of equations as V=F(X)+e; where, V=[V ₁ ,...,V _N ] ^T , which is N-channel interference signal; F(·)=[F ₁ ( ·),..., F _N (·)], is the optical path model function. Since the value of the second collimator position parameter _Pi has been substituted into the system of equations, F(·) is a function only about X; e = [ε ₁ , ε ₂ ,..., ε _n ], is the noise signal of N interference signals; X is the six-degree-of-freedom displacement of the mass block relative to the coordinate origin, and is the quantity to be solved.

S2: Calculate the iteration initial value X ₀ of variable X using the preset nominal parameter values.

S3: Select the minimization objective function

Iteratively solve the variable X according to the following iterative formula:

X _k+1 =X _k +[J ^T (X _k )J(X _k )] ^-1 J ^T (X _k )[VF(X _k )]

in,

is the Jacobian matrix of F(X _k ).

S4: Given the error preset value δ and _the maximum number of iterations k _max , if ||X _k+1 -X _k ||≥δ and k<k _max , return to S3 to continue iteration, if || If X _k ||<δ or k≥k _max , the iteration ends and a solution result X _k+1 close to the true value is obtained.

In this embodiment, the position parameters of the second collimator corresponding to the i-th interference signal include: the coordinates of the second collimator, and the outgoing laser direction vector of the second collimator; pre-calibrated in the following manner Obtain the position parameter of the second collimator corresponding to the i-th interference signal.

Step 1: Record the values of each interference signal when M times of different acceleration inputs are entered. Substitute the recorded values of each interference signal into the optical path model equations to obtain the following second set of equations, where M>5N/(N-6) , so that the number of equations in the system of equations is greater than the number of unknowns.

Among them, the meaning of each parameter is the same as the meaning of each parameter in the above-mentioned first set of equations. In this second set of equations, considering the six-degree-of-freedom displacement X of the mass block relative to the coordinate origin and the second collimator position parameter _Pi as unknown quantities, a total of MN equations are included, (6M+5N) Unknown.

Step 2: Use the least squares method to solve the second set of equations to obtain the position parameters of the second collimator corresponding to the i-th interference signal.

In one embodiment, the least squares method is used to solve the above second set of equations, that is, to minimize

In order to optimize the target, the solution of the collimator parameter _Pi when reaching the target is obtained, which is used as the self-calibration result to complete the self-calibration.

In this embodiment, the least squares method is used to solve the second set of equations to obtain the position parameters of the second collimator corresponding to the i-th interference signal, which includes the following steps S1 to S4.

S1: Rewrite the second set of equations as V=F(Y)+e; among them, V=[V ₁ ,...,V _MN ] ^T , which is the MN interference signal; F(·)=[F ₁ ( ·),...,F _N (·)], is the optical path model function; e=[ε ₁ , ε ₂ ,..., ε _MN ], is the noise signal of the N-channel interference signal;

is the six-degree-of-freedom displacement of the mass block relative to the coordinate origin, and the position parameter of the second collimator corresponding to the N-channel interference signal, which is the six-degree-of-freedom displacement of the M group of mass blocks relative to the coordinate origin and N sets of second collimator position parameters.

S2: Calculate the iteration initial value Y ₀ of variable Y using the preset parameter nominal values.

S3: Select the minimization objective function

Iteratively solve the variable Y according to the following iterative formula:

Y _k+1 ＝Y _k +[J ^T (Y _k )J(Y _k )] ^-1 J ^T (Y _k )[VF(Y _k )]

in,

is the Jacobian matrix of F(Y _k ).

S4: Given the error preset value δ and the maximum number of iterations k _max , if ||Y _k+1 -Y _k ||≥δ and k<k _max , return to S3 to continue iteration, if ||Y _k+1 - If Y _k ||<δ or k≥k _max , the iteration ends and the solution result Y _k+1 close to the true value is obtained. The N sets of second collimator position parameter values in Y _k+1 are the self-calibration of P _i result.

An accelerometer provided by an embodiment of the present disclosure uses a laser interferometer to generate reference light and measurement light. The measurement light is transmitted to the inside of the casing of the meter head through an optical fiber, emitted to the surface of the mass block, and then reflected by the surface of the mass block. It is received by the laser interferometer and interferes with the reference light to form interference light, which is then converted into an interference signal and the acceleration calculation module calculates the acceleration of the object to be measured. That is, the embodiment of the present disclosure uses a laser interferometer as the detection unit. Compared with accelerometers in the related art that use strain gauges, piezoelectric sensors, capacitive sensors, and electromagnetic induction sensors as detection units, embodiments of the present disclosure have better linearity, and therefore can effectively reduce nonlinear errors caused by the detection principle. , thereby improving the accuracy of acceleration measurement to obtain more accurate acceleration measurement results.

The accelerometer provided by the embodiment of the present disclosure is a new type of precision six-dimensional accelerometer, which has the advantages of high accuracy, large range, etc.; the accelerometer as a whole consists of a laser interferometer that can measure N (N>6) displacements, It consists of a meter head and an acceleration calculation module. The meter head consists of a shell, an elastic support and a mass block. The laser interferometer consists of a laser source, an interference lens group and a signal processing board. The measurement light of the laser interferometer enters through the collimator. The head, after reflection at different positions on the surface of the mass block, interferes with the reference light; when acceleration is input, the laser interferometer measures N interference signals containing coupled and redundant six-dimensional acceleration information, which are input to the acceleration solution After calculating the module, the acceleration value of each axis is obtained according to the acceleration decoupling algorithm and the detection unit parameter self-calibration algorithm. The present disclosure can be applied to six-dimensional acceleration precision measurement.

Compared with six-dimensional accelerometers in related technologies, the present disclosure also has the following advantages: (1) Compared with six-dimensional accelerometers based on strain gauges, piezoelectric sensors, capacitive sensors, and electromagnetic induction sensors, the present disclosure adopts a linear accelerometer. A laser interferometer with better accuracy is used as the detection unit, which reduces the nonlinear error caused by the detection principle and improves the accuracy of acceleration measurement; (2) This disclosure adopts the principle of multi-channel signal redundancy measurement, by increasing the number of signal channels N, reducing the accidental measurement errors caused by signal noise and improving the accuracy of acceleration measurement; (3) This disclosure adopts the collimator parameter self-calibration method, which avoids the processing and installation errors of the manually calibrated detection unit, and improves the accuracy of the acceleration measurement. interference signal model accuracy, thereby improving acceleration measurement accuracy.

In the several embodiments provided in this application, the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated. to another system, or some features can be ignored, or not implemented.

A unit described as a separate component may or may not be physically separate. A component shown as a unit may or may not be a physical unit, that is, it may be located in one place, or it may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present disclosure.

In addition, each functional unit in various embodiments of the present disclosure may be integrated into one processing unit, or each processing unit may exist physically alone, or two or more processing units may be integrated into one unit. The above integrated units can be implemented in the form of hardware or software functional units.

Integrated units may be stored in a computer-readable storage medium if they are implemented in the form of software functional units and sold or used as independent products. Based on this understanding, the technical solution of the present disclosure is essentially or contributes to the relevant technology, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium , including several instructions to cause an electronic device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present disclosure. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program code. .

Although the embodiments disclosed in the present disclosure are as above, the described content is only to facilitate understanding of the present disclosure and is not intended to limit the present disclosure. Any person skilled in the technical field to which this disclosure belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope of this disclosure. However, the protection scope of this disclosure must still be maintained. The scope defined by the appended claims shall prevail.

Claims

An accelerometer, which includes: a laser interferometer, a meter head and an acceleration calculation module; the meter head includes: a housing, a mass block and an elastic support; the mass block is arranged inside the housing, so The mass block and the housing are connected through the elastic support; the housing is used to be fixedly connected to the object to be measured; the laser interferometer is used to generate reference light and measurement light; the measurement light is The optical fiber is transmitted to the inside of the housing and emitted to the surface of the mass block; the surface of the mass block is used to reflect the measurement light to form reflected light; the laser interferometer is also used to receive the reflected light and make The reflected light interferes with the reference light to form interference light; the laser interferometer is also used to convert the interference light into an interference signal and send it to the acceleration calculation module; the acceleration solution The calculation module is used to calculate the received interference signal and obtain the acceleration value of the object to be measured.
The accelerometer according to claim 1, wherein when the object to be measured has acceleration, the mass block can generate six degrees of freedom displacement relative to the housing; wherein the six degrees of freedom include: respectively The degrees of freedom of movement along the three rectangular coordinate axes of X, Y, and Z, and the degrees of freedom of rotation around the three rectangular coordinate axes of X, Y, and Z respectively.
The accelerometer according to claim 2, wherein there is at least one elastic support member; the mass block is in the shape of a regular hexahedron; each surface of the mass block passes through the elastic support member corresponding to the surface Connected to the inner wall of the housing.
The accelerometer according to claim 1, wherein the surface of the mass block is coated with a laser reflective film.
The accelerometer according to claim 2, wherein the laser interferometer includes: a laser source, an interference lens group and a signal processing board; the interference lens group includes: a polarizing beam splitter, a first quarter-wave plate, a second quarter wave plate and a reflecting mirror; the laser light generated by the laser source is divided into the reference light and the measurement light through the polarization beam splitter; the reference light passes through the first quarter wave plate. After passing through the wave plate, it is reflected by the mirror and then returns along the original optical path; after passing through the second quarter-wave plate, the measurement light enters the optical fiber through the first collimator and is emitted by the optical fiber. It is transmitted to the inside of the housing and emitted to the surface of the mass block through the second collimator; the reflected light enters the optical fiber through the second collimator and returns along the original optical path; the interference light passes through the second collimator. The three collimators enter the signal processing board, and are converted into the interference signal by the signal processing board and then sent to the acceleration calculation module.
The accelerometer according to claim 5, wherein when the mass block is in the shape of a regular hexahedron, the measurement light is emitted through the second collimator to at least three adjacent faces of the mass block. .
The accelerometer according to claim 5, wherein there are N interference lens groups, wherein N>6; the laser generated by the laser source is transmitted to each interference lens group through N optical fibers respectively, so as to N channels of interference light are formed; the signal processing board is also used to convert the N channels of interference light into N channels of interference signals and then send them to the acceleration calculation module.
The accelerometer according to claim 7, wherein the acceleration calculation module calculates the received interference signal in the following manner to obtain the acceleration value of the object to be measured:

Substituting N channels of interference signals into the optical path model equations, the first equations are obtained:

Where, Vi is the i-th interference signal, i=1,2,3...,N; X is the six-degree-of-freedom displacement of the mass block relative to the coordinate origin, where the coordinate origin is zero The position of the center of mass of the mass block when acceleration is input; P i is the position parameter of the second collimator corresponding to the interference signal of the i-th channel, obtained by pre-calibration; ε i is the position of the i-th channel The noise signal of the interference signal; F i (·) is the i-th optical path model function, and the output of this function is the optical path difference between the i-th measurement light and the i-th reference light;

The least squares method is used to solve the first system of equations to obtain the six-degree-of-freedom displacement of the mass block relative to the coordinate origin;

Calculate the product of the six-degree-of-freedom displacement of the mass block relative to the coordinate origin and the pre-calibrated stiffness matrix to obtain the acceleration value of the object to be measured.
The accelerometer according to claim 8, wherein the least square method is used to solve the first set of equations to obtain the six-degree-of-freedom displacement of the mass relative to the coordinate origin, including:

S1: Rewrite the first set of equations as V=F(X)+e; where, V=[V 1 ,...,V N ] T , which is the interference signal of N channels; F(·)= [F 1 (·),..., F N (·)] is the optical path model function; e=[ε 1 , ε 2 ,..., ε n ] is the interference signal of N paths Noise signal; X is the six-degree-of-freedom displacement of the mass relative to the coordinate origin;

S2: Calculate the iteration initial value of variable X using the preset nominal parameter values;

S3: Select the minimization objective function
Iteratively solve the variable X according to the following iterative formula:

X k+1 =X k +[J T (X k )J(X k )] -1 J T (X k )[VF(X k )]

in,
is the Jacobian matrix of F(X k );

S4: Given the error preset value δ and the maximum number of iterations k max , if ||X k+1 -X k ||≥δ and k<k max , return to S3 to continue iteration, if || If X k ||<δ or k≥k max , the iteration ends and a solution result X k+1 close to the true value is obtained.
The accelerometer according to claim 8, wherein the position parameter of the second collimator corresponding to the i-th interference signal includes: the coordinates of the second collimator, and the second collimator The outgoing laser direction vector of the collimator; pre-calibrate to obtain the position parameters of the second collimator corresponding to the i-th interference signal in the following manner:

Record the values of each interference signal at M times of different acceleration inputs, and substitute the recorded values of each interference signal into the optical path model equations to obtain the following second equations, where M>5N/(N-6);

The least squares method is used to solve the second set of equations to obtain the position parameters of the second collimator corresponding to the i-th interference signal.
The accelerometer according to claim 10, wherein the least square method is used to solve the second set of equations to obtain the position of the second collimator corresponding to the i-th interference signal. Parameters, including:

S1: Rewrite the second set of equations as V=F(Y)+e; where, V=[V 1 ,...,V MN ] T , is the interference signal of the MN path; F(·)= [F 1 (·),..., F N (·)] is the optical path model function; e=[ε 1 , ε 2 ,..., ε MN ] is the function of the N interference signals noise signal;
is the six-degree-of-freedom displacement of the mass relative to the coordinate origin, and the position parameters of the second collimator corresponding to the N interference signals;

S2: Calculate the iteration initial value of variable Y using the preset nominal parameter values;

S3: Select the minimization objective function
Iteratively solve the variable Y according to the following iterative formula:

Y k+1 ＝Y k +[J T (Y k )J(Y k )] -1 J T (Y k )[VF(Y k )]

in,
is the Jacobian matrix of F(Y k );

S4: Given the error preset value δ and the maximum number of iterations k max , if ||Y k+1 -Y k ||≥δ and k<k max , return to S3 to continue iteration, if ||Y k+1 - If Y k ||<δ or k≥k max , the iteration ends and a solution result Y k+1 close to the true value is obtained.