CN107576334B

CN107576334B - Calibration method and device of inertia measurement unit

Info

Publication number: CN107576334B
Application number: CN201610519242.0A
Authority: CN
Inventors: 张金凤
Original assignee: Beijing Unistrong Science & Technology Co ltd
Current assignee: Beijing Unistrong Science & Technology Co ltd
Priority date: 2016-07-04
Filing date: 2016-07-04
Publication date: 2020-03-31
Anticipated expiration: 2036-07-04
Also published as: CN107576334A

Abstract

The embodiment of the invention discloses a calibration method and a calibration device of an IMU (inertial measurement Unit), which are used for respectively acquiring output angular velocity data of each single-axis gyroscope in the IMU under different placement states and rotation states; simultaneously, respectively acquiring acceleration data output by each single-axis accelerometer in a static state under different placing states; then, according to the data characteristics output in different placement states, the mutual influence among the parameters is eliminated, namely, the decoupling of the parameters is realized, and the true values of the parameters are obtained, so that the calibration precision of the IMU is improved.

Description

Calibration method and device of inertia measurement unit

Technical Field

The invention relates to the technical field of automatic control, in particular to a calibration method and a calibration device for an inertia measurement unit.

Background

An IMU (Inertial Measurement Unit) contains three single-axis accelerometers and three single-axis gyroscopes. The three single-axis accelerometers are orthogonally arranged and used for respectively measuring acceleration information in three axis directions; the three single-axis gyroscopes are orthogonally installed and used for respectively measuring angular velocity information in three axis directions. And measuring the angular speed and the acceleration of the object in the inertial space, and calculating the attitude of the object according to the angular speed and the acceleration.

MEMS (Micro-Electro-Mechanical Systems ) IMUs are finding increasingly widespread use in the field of navigation. Under the influence of various factors, after the MEMS IMU is placed for a period of time, the error parameters and the inertial element parameters of the MEMS IMU change, and the precision requirements of navigation and guidance cannot be met, so that the corresponding parameters of the MEMS IMU must be calibrated regularly.

At present, various parameters of the MEMS IMU are calibrated independently, and the calibration of each parameter needs to acquire data independently and then calibrate. Due to the interplay between the various parameters of the IMU, for example, the zero offset, the scale factor and the misalignment angle. The single calibration mode not only consumes long time in the calibration process, but also influences of various parameters, and the calibration mode cannot eliminate or reduce the mutual influence among various parameters (namely, various parameters cannot be decoupled) to the greatest extent, so that the parameter calibration precision is low.

Disclosure of Invention

The embodiment of the invention provides a calibration method and a calibration device of an inertia measurement unit, and aims to solve the problem of low parameter calibration precision of the inertia measurement unit in the prior art.

In order to solve the technical problem, the embodiment of the invention discloses the following technical scheme:

in a first aspect, the present invention provides a calibration method for an inertial measurement unit IMU, where the method includes:

in a preset temperature environment, respectively acquiring output data of each sensor in the IMU under different placement states;

for any one sensor, eliminating the influence of zero deviation scaling factor by using the output data of the sensor in different placement states to obtain the misalignment angle scaling factor coupling term of the sensor; obtaining a corresponding scale factor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term; obtaining the misalignment angle of the sensor by utilizing the misalignment angle scale factor coupling term and the scale factor; obtaining a zero offset of the sensor using the scale factor and the misalignment angle;

obtaining a fitting coefficient by using the scale factor and the zero offset which are obtained at different preset temperatures and correspond to each sensor;

and substituting the fitting coefficient into a preset output model of the IMU to obtain a calibration output model of the IMU.

Optionally, the placement state includes:

the Y-axis positive direction is a first state of the direction of the gravitational acceleration, a second state of the X-axis positive direction opposite to the direction of the gravitational acceleration, a third state of the Z-axis positive direction opposite to the direction of the gravitational acceleration, a fourth state obtained by rotating the second state by 180 degrees around the Z axis, a fifth state obtained by rotating the first state by 180 degrees around the X axis, and a sixth state obtained by rotating the third state by 180 degrees around the Y axis.

Optionally, if the sensor is a single-axis gyroscope, the obtaining a misalignment angle scaling factor coupling term by eliminating the influence of a zero-offset scaling factor by using output data of the sensor in different placement states includes:

calculating a first difference value of angular velocity data output by the single-axis gyroscope in a forward rotation state and a reverse rotation state respectively, wherein the X axis is used as a rotating axis; obtaining a first misalignment angle scale factor coupling term of the single-axis gyroscope according to the first difference, the rotation rate of the single-axis gyroscope and the preset temperature;

calculating a second difference value of angular velocity data output by the single-axis gyroscope in a forward rotation state and a reverse rotation state respectively, wherein the Y axis is used as a rotating axis; obtaining a second misalignment angle scale factor coupling term of the single-axis gyroscope according to the second difference, the rotation rate of the single-axis gyroscope and the preset temperature;

calculating a third difference value of angular velocity data output by the single-axis gyroscope in a forward rotation state and a reverse rotation state respectively, wherein the Z axis is used as a rotating axis; and obtaining a third misalignment angle scale factor coupling term of the single-axis gyroscope according to the third difference, the rotation rate of the single-axis gyroscope and the preset temperature.

Optionally, if the sensor is a single-axis gyroscope, the obtaining the scale factor corresponding to the sensor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term includes:

and for any one of the single-axis gyroscopes, utilizing the first misalignment angle scale factor coupling term, the second misalignment angle scale factor coupling term and the third misalignment angle scale factor coupling term to eliminate the influence of the misalignment angle scale factor according to a trigonometric theorem to obtain the scale factor of the single-axis gyroscope.

Optionally, if the sensor is a uniaxial gyroscope, the obtaining the misalignment angle of the sensor by using the misalignment angle scale factor coupling term and the scale factor includes:

and for any one of the single-axis gyroscopes, respectively calculating misalignment angles between the single-axis gyroscope and the other two axes by using corresponding misalignment angle scale factor coupling terms when the other two axes except the axis where the single-axis gyroscope is located in the three axes are respectively taken as rotating axes and the scale factors of the single-axis gyroscope.

Optionally, if the sensor is a uniaxial accelerometer, the obtaining a misalignment angle scaling factor coupling term by eliminating the influence of a zero offset scaling factor by using output data of the sensor in different placement states includes:

calculating a first difference value of acceleration data output by the single-axis accelerometer under the condition that the directions of an X axis and gravity acceleration are the same and opposite; obtaining a first misalignment angle scale factor coupling term of the single-axis accelerometer according to the first difference, the gravity acceleration and the preset temperature;

calculating a second difference value of acceleration data output by the single-axis accelerometer under the condition that the direction of the Y axis is the same as or opposite to that of the gravity acceleration; obtaining a second misalignment angle scale factor coupling term of the single-axis accelerometer according to the second difference, the gravity acceleration and the preset temperature;

calculating a third difference value of acceleration data output by the single-axis accelerometer under the condition that the direction of the Z axis is the same as or opposite to that of the gravity acceleration; and obtaining a third misalignment angle scale factor coupling term of the single-axis accelerometer according to the third difference, the gravity acceleration and the preset temperature.

Optionally, if the sensor is a uniaxial accelerometer, the obtaining, by using the misalignment angle scale factor coupling term, a scale factor corresponding to the sensor after the misalignment angle is eliminated includes:

and for any one of the uniaxial accelerometers, utilizing the first misalignment angle scale factor coupling term, the second misalignment angle scale factor coupling term and the third misalignment angle scale factor coupling term to eliminate the influence of the misalignment angle scale factor according to a trigonometric theorem to obtain the scale factor of the uniaxial accelerometer.

Optionally, if the sensor is a uniaxial accelerometer, the obtaining the misalignment angle of the sensor by using the misalignment angle scaling factor coupling term and the scaling factor includes:

for any one of the single-axis accelerometers, the misalignment angle between the single-axis accelerometer and the other two axes is calculated by utilizing the corresponding misalignment angle scale factor coupling terms of the other two axes except the axis where the single-axis accelerometer is located in the same direction and the opposite direction of the gravity acceleration and the scale factors of the single-axis accelerometer.

In a second aspect, the present invention provides a calibration apparatus for an inertial measurement unit IMU, including:

the data acquisition module is used for respectively acquiring output data of each sensor in the IMU under different placement states in a preset temperature environment;

the parameter calibration module is used for eliminating the influence of a zero deviation scaling factor by utilizing the output data of the sensor in different placing states to obtain a misalignment angle scaling factor coupling term of the sensor; obtaining a corresponding scale factor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term; obtaining the misalignment angle of the sensor by utilizing the misalignment angle scale factor coupling term and the scale factor; obtaining a zero offset of the sensor using the scale factor and the misalignment angle;

the fitting module is used for obtaining a fitting coefficient by utilizing the scale factor and the zero offset which are obtained at different preset temperatures and correspond to each sensor;

and the output model calibration module is used for substituting the fitting coefficient into a preset output model of the IMU to obtain a calibration output model of the IMU.

Optionally, if the sensor is a single-axis gyroscope, the parameter calibration module is configured to eliminate an influence of a zero-offset scaling factor by using output data of the sensor in different placement states, and when a misalignment angle scaling factor coupling term of the sensor is obtained, specifically configured to:

Optionally, if the sensor is a single-axis gyroscope, when the parameter calibration module obtains the scale factor corresponding to the sensor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term, the parameter calibration module is specifically configured to:

Optionally, if the sensor is a single-axis gyroscope, the gyroscope parameter calibration module is specifically configured to, when obtaining the misalignment angle of the sensor by using the misalignment angle scale factor coupling term and the scale factor:

Optionally, if the sensor is a uniaxial accelerometer, the parameter calibration module is configured to, when the influence of a zero offset scaling factor is eliminated by using output data of the sensor in different placement states, obtain a misalignment angle scaling factor coupling term of the sensor, specifically:

Optionally, if the sensor is a uniaxial accelerometer, when the parameter calibration module obtains the scale factor corresponding to the sensor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term, the parameter calibration module is specifically configured to:

Optionally, if the sensor is a uniaxial accelerometer, the parameter calibration module is specifically configured to, when obtaining the misalignment angle of the sensor by using the misalignment angle scale factor coupling term and the scale factor:

According to the technical scheme, the IMU calibration method provided by the embodiment of the invention can be used for respectively acquiring the output data of each sensor in the IMU under different states. Firstly, the influence of zero deviation on the scale factor is eliminated by utilizing output data, and a misalignment angle scale factor coupling term containing a misalignment angle and the scale factor is obtained. And eliminating the influence of the misalignment angle on the scale factor by using each misalignment angle scale factor coupling term to obtain the decoupled real scale factor. And obtaining a real misalignment angle by using the decoupled scale factor and the corresponding misalignment angle scale factor coupling term. And obtaining the real zero offset by using the decoupled scale factor and the decoupled misalignment angle. And obtaining a fitting coefficient by utilizing the decoupled scale factor and zero offset in different temperature environments, substituting the fitting coefficient into a preset output model of the IMU, and finally obtaining the IMU calibrated output model. According to the method, the mutual influence among all parameters is eliminated according to the data characteristics output in different states, namely, the decoupling of all parameters is realized, and the true values of all parameters are obtained, so that the calibration precision of the IMU is improved.

Drawings

In order 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 described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.

FIG. 1 is a schematic flow chart of an IMU calibration method according to an embodiment of the present invention;

FIG. 2 is a schematic illustration of a placement state according to an embodiment of the invention;

fig. 3 is a block diagram of an IMU calibration apparatus according to an embodiment of the present invention.

Detailed Description

Before describing the embodiment of the present invention in detail, the parameters of the IMU to be calibrated in the present invention are described: the zero offset is as the name implies that when the output of the IMU should be 0, the actual output is not zero; the scaling factor refers to the scaling factor between the actual output and the input of the IMU; the misalignment angle means that the coherence axis has an effect on the output of the three axes because the axes are not perfectly orthogonal when the gyroscopes or accelerometers are mounted. For example, for an X-axis gyroscope, a Y-axis gyroscope and a Z-axis gyroscope are the coherence axes; for a Y-axis gyroscope, the X-axis gyroscope and the Z-axis gyroscope are coherent axes; for a Z-axis gyroscope, the X-axis gyroscope and the Y-axis gyroscope are coherent axes.

According to the IMU calibration method provided by the invention, in a preset temperature environment, output data of each sensor in the IMU under different placement states are respectively acquired; then, for any sensor, the output data of the sensor in different placement states is utilized to eliminate the coupling relation among zero offset, a scale factor and a misalignment angle, namely, all parameters are decoupled; then, obtaining a fitting coefficient by using the scale factor and the zero offset which are obtained at different preset temperatures and correspond to each sensor; and finally, substituting the fitting coefficient into a preset output model of the IMU to obtain a calibration output model of the IMU, so that the calibration precision of the IMU is improved.

It should be noted that any sensor herein refers to any uniaxial gyroscope or any uniaxial accelerometer hereinafter.

In order to make the technical solutions in the embodiments of the present invention better understood and make the above objects, features and advantages of the embodiments of the present invention more comprehensible, the technical solutions in the embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

The output of the MEMS IMU is biased in different temperature environments, and therefore, the parameters of the IMU need to be calibrated in combination with temperature.

The calibration process needs an incubator, a single-shaft or multi-shaft rotary table and a hexahedron clamp, wherein the rotary table is placed in the incubator, and the temperature of the incubator can be controlled; the hexahedral clamp is used for fixing the IMU to be calibrated. The turntable may rotate in a forward direction (clockwise rotation) or a reverse direction (counterclockwise rotation) about the gravitational acceleration direction.

Referring to fig. 1, which is a schematic flow chart of an IMU calibration method according to an embodiment of the present invention, after the temperature of the incubator is stabilized at a preset temperature T, various parameters of the IMU are calibrated. In the present embodiment, an X-axis gyroscope and an X-axis accelerometer are taken as examples to explain:

and S110, respectively acquiring angular velocity data output by the X-axis gyroscope in different placing states and different rotating states.

The placing state includes different states in which the X axis, the Y axis, and the Z axis are respectively used as the rotation axes and the positive directions of the rotation axes are opposite, for example, when the X axis is used as the rotation axis, the placing state must include two states in which the positive direction of the X axis is directed toward the gravitational acceleration direction and the positive direction of the X axis is opposite to the gravitational acceleration direction. The rotation state includes normal rotation (clockwise rotation) about the gravitational acceleration direction and reverse rotation (counterclockwise rotation) about the gravitational acceleration direction.

And S120, respectively acquiring acceleration data output by the X-axis accelerometer in different placing states.

Calibrating the accelerometer requires only output data from the IMU in a static state, while calibrating the gyroscope requires output data from the IMU in a dynamic state, so that S120 and then S110 may be performed for a certain placement state.

And S130, eliminating the influence of the zero deviation scaling factor by utilizing the angular velocity data corresponding to the X-axis gyroscope to obtain a misalignment angle scaling factor coupling term of the X-axis gyroscope.

For the X-axis gyroscope, calculating a corresponding misalignment angle scale factor coupling term of the X-axis gyroscope according to the following steps:

1) calculating a first difference value of angular velocity data output by an X-axis gyroscope in a forward rotation state and a reverse rotation state respectively, wherein the X-axis gyroscope is used as a rotating shaft; obtaining a first misalignment angle scale factor coupling term of the X-axis gyroscope according to the first difference, the rotation rate of the X-axis gyroscope and a preset temperature; see equation 8 below and will not be described in detail here.

2) Calculating a second difference value of angular velocity data output by the X-axis gyroscope in a forward rotation state and a reverse rotation state respectively by taking the Y axis as a rotating shaft; obtaining a second misalignment angle scale factor coupling term of the X-axis gyroscope according to the second difference, the rotation rate of the X-axis gyroscope and the preset temperature; see equation 7, which will be described later, and will not be described in detail here.

3) Calculating a third difference value of angular velocity data output by the X-axis gyroscope in a forward rotation state and a reverse rotation state respectively by taking the Z axis as a rotating shaft; and obtaining a third misalignment angle scale factor coupling term of the X-axis gyroscope according to the third difference, the rotation rate of the X-axis gyroscope and the preset temperature. See equation 9 below and will not be described in detail here.

And S140, obtaining the scale factor corresponding to the X-axis gyroscope after the misalignment angle is eliminated by utilizing the misalignment angle scale factor coupling term.

For the X-axis gyroscope, the influence of the proportional factor of the misalignment angle is eliminated by utilizing the first misalignment angle proportional factor coupling term, the second misalignment angle proportional factor coupling term and the third misalignment angle proportional factor coupling term and combining a trigonometric formula, and the proportional factor of the X-axis gyroscope is obtained through calculation. Please refer to equation 10 below, which will not be described in detail.

And S150, obtaining the misalignment angle of the X-axis gyroscope by utilizing the misalignment angle scale factor coupling term and the scale factor.

For the X-axis gyroscope, the misalignment angle between the X-axis gyroscope and the Y-axis gyroscope is calculated by using the misalignment angle scale factor coupling term and the scale factor corresponding to the X-axis gyroscope when the Y-axis is used as the rotation axis, which may be specifically referred to as formula 12 in the following, and details are not described here.

When the Z axis is used as the rotation axis, the misalignment angle of the Z axis gyroscope and the X axis gyroscope is calculated by using the misalignment angle scale factor coupling term and the scale factor corresponding to the X axis gyroscope, which can be referred to as formula 11 in the following, and is not described in detail here.

And S160, obtaining the zero offset of the X-axis gyroscope by using the scale factor and the misalignment angle.

After the decoupled scale factor and misalignment angle of the X-axis gyroscope are obtained through calculation in the above steps, the true zero offset of the X-axis gyroscope is obtained through calculation, which can be referred to as formula 13 and is not described in detail here.

And repeating S130-S160 to obtain the scale factor, the misalignment angle and the zero offset of the Y-axis gyroscope and the Z-axis gyroscope.

Similarly, the scale factor, misalignment angle, and zero offset of the accelerometer are found with reference to the method described above.

S170, eliminating the influence of the zero deviation scaling factor by using the acceleration data of the X-axis accelerometer to obtain a misalignment angle scaling factor coupling term of the X-axis accelerometer.

For an X-axis accelerometer, the misalignment angle scale factor coupling term can be calculated as follows:

1) respectively calculating acceleration data output by an X-axis accelerometer when the directions of the X-axis and the gravity acceleration are the same, and calculating a first difference value between the acceleration data output by the X-axis accelerometer when the directions of the X-axis and the gravity acceleration are opposite; and then, obtaining a first misalignment angle scale factor coupling term of the X-axis accelerometer according to the first difference, the gravity acceleration and the preset temperature.

2) Respectively calculating acceleration data output by the X-axis accelerometer when the direction of the Y axis is the same as that of the gravity acceleration and calculating a second difference value between the acceleration data output by the X-axis accelerometer when the direction of the Y axis is opposite to that of the gravity acceleration; and then, obtaining a second misalignment angle scale factor coupling term of the X-axis accelerometer according to the second difference, the gravity acceleration and the preset temperature.

3) Respectively calculating acceleration data output by the X-axis accelerometer when the direction of the Z axis is the same as that of the gravity acceleration and calculating a third difference value between the acceleration data output by the X-axis accelerometer when the direction of the Z axis is opposite to that of the gravity acceleration; and then, obtaining a third misalignment angle scale factor coupling term of the X-axis accelerometer according to the third difference, the gravity acceleration and the preset temperature.

And S180, obtaining the scale factor corresponding to the uniaxial accelerometer after the misalignment angle is eliminated by utilizing the misalignment angle scale factor coupling term.

And eliminating the influence of the proportional factor of the misalignment angle according to a trigonometric theorem by utilizing a first misalignment angle proportional factor coupling term, a second misalignment angle proportional factor coupling term and a third misalignment angle proportional factor coupling term which correspond to the X-axis accelerometer, and calculating to obtain the proportional factor of the X-axis accelerometer.

And S190, obtaining the misalignment angle of the X-axis accelerometer by using the misalignment angle scale factor coupling term and the scale factor.

For the X-axis accelerometer, calculating a misalignment angle between the X-axis accelerometer and the Y-axis accelerometer by using a misalignment angle scale factor coupling term corresponding to the X-axis accelerometer in a state that the Y-axis is an acceleration axis (that is, the Y-axis direction is the same as or opposite to the gravity acceleration direction), and the scale factor of the X-axis accelerometer calculated in the above steps;

similarly, the misalignment angle between the X-axis accelerometer and the Z-axis accelerometer can be calculated, which is not described herein.

And S1100, obtaining the zero offset of the X-axis accelerometer by using the scale factor and the misalignment angle.

And calculating to obtain the scale factor and the misalignment angle of the X-axis accelerometer after decoupling by utilizing the steps, and calculating the real zero offset of the X-axis accelerometer.

And repeatedly executing S170-S1100 to obtain the scale factor, the misalignment angle and the zero offset of the Y-axis accelerometer and the Z-axis accelerometer.

Then, calculating the scale factor, misalignment angle and zero offset of the X-axis gyroscope, the Y-axis gyroscope and the Z-axis gyroscope at different preset temperatures according to the same method; and solving the scale factor, the misalignment angle and the zero offset of the accelerometers at the X axis, the Y axis and the Z axis at different preset temperatures.

And S1110, obtaining a fitting coefficient by using the scale factor and the zero offset corresponding to each single-axis gyroscope and the scale factor and the zero offset corresponding to each accelerometer, which are obtained at different preset temperatures.

And S1120, substituting the fitting coefficient into a preset output model of the IMU to obtain a calibration output model of the IMU.

It should be noted that, various parameters of the accelerometer may be obtained first, various parameters of the gyroscope are obtained, and finally, the IMU is calibrated by using the parameters of the accelerometer and the gyroscope.

In the IMU calibration method provided in this embodiment, output angular velocity data of each single-axis gyroscope in the IMU is respectively obtained in different placement states and rotation states; simultaneously, respectively acquiring acceleration data output by each single-axis accelerometer in a static state under different placing states; then, eliminating the influence of the zero deviation scaling factor by utilizing the angular velocity data to obtain a misalignment angle scaling factor coupling term containing the misalignment angle and the scaling factor, and then eliminating the influence of the misalignment angle scaling factor by utilizing each misalignment angle scaling factor coupling term to obtain a decoupled real scaling factor. And obtaining a real misalignment angle by using the decoupled scale factor and the corresponding misalignment angle scale factor coupling term. And obtaining the real zero offset by using the decoupled scale factor and the decoupled misalignment angle. And obtaining a fitting coefficient by utilizing the decoupled scale factor and zero offset in different temperature environments, substituting the fitting coefficient into a preset output model of the IMU, and finally obtaining the IMU calibrated output model. According to the method, the mutual influence among all parameters is eliminated according to the data characteristics output in different placement states, namely, the decoupling of all parameters is realized, and the true values of all parameters are obtained, so that the calibration precision of the IMU is improved.

Fig. 2 is a schematic diagram of six placement states of an IMU according to an embodiment of the present invention.

The first state is that the positive direction of the Y axis faces the direction of the gravitational acceleration, and the second state is that the positive direction of the X axis is opposite to the direction of the gravitational acceleration; the third state is that the positive direction of the Z axis is opposite to the gravity acceleration direction; the fourth state is obtained by rotating the second state by 180 degrees around the Z axis; the fifth state is obtained by rotating the first state by 180 degrees around the X axis; the sixth state is obtained by rotating the third state by 180 degrees around the Y axis.

The first, second, third, fourth, fifth, and sixth states are only for distinguishing different placement states, and the names for distinguishing the respective states may be changed, and for example, the first state may be defined as a state in which the positive direction of the X axis is opposite to the direction of gravitational acceleration.

And respectively acquiring and storing the data when the IMU is placed in the six placing states without repeatedly acquiring the data.

The calibration process of the IMU will be described in detail based on the placement state shown in fig. 2.

Selecting a preset temperature T according to the preset working temperature range of an IMU internal device, and carrying out a subsequent calibration process after the temperature of the incubator is stabilized at the preset temperature T:

for a three-axis gyroscope, the rotation rate of the turntable is required as input to the three-axis gyroscope, so only dynamic data is used; for the triaxial accelerometer, the gravity acceleration is required to be used as the input of the triaxial accelerometer, so only static data is used, and therefore, the process of acquiring the output data of the IMU in different states is as follows:

1) the IMU is placed in a first state, the rotary table is static, and output data of the three-axis accelerometer are collected;

2) the IMU is placed in a first state, the rotary table rotates forwards at the maximum rotation rate v allowed by the three-axis gyroscope, and output data of the three-axis gyroscope at the moment are collected;

3) the IMU is placed in a first state, the rotary table rotates reversely at the maximum rotation rate v allowed by the three-axis gyroscope, and output data of the three-axis gyroscope at the moment are collected;

5) and when the IMU is placed in a second state, a third state, a fourth state, a fifth state and a sixth state respectively, repeating the acquisition process of the steps 1) to 4).

6) Repeating the acquisition process of the steps 1) to 5) at different preset temperatures.

Taking an X-axis gyroscope as an example, the output data of the X-axis gyroscope in different states, which needs to be acquired during parameter calibration, includes:

e0_ gx, the IMU is placed in the first state, and the mean value of the output data of the X-axis gyroscope collected when the rotary table rotates forwards is acquired;

e90_ gx, the IMU is placed in the second state, and the mean value of the output data of the X-axis gyroscope collected when the rotary table rotates forwards is acquired;

e180_ gx, the IMU is placed in the first state, and the mean value of the output data of the x-axis gyroscope collected when the turntable rotates reversely is obtained;

e270_ gx, the IMU is placed in a second state, and the mean value of the output data of the x-axis gyroscope collected when the rotary table rotates reversely is obtained;

e01_ gx, the IMU is placed in a third state, and the mean value of the output data of the x-axis gyroscope collected when the rotary table rotates forwards is acquired;

e1801_ gx, IMU placed in the third state, mean of x-axis gyroscope output data collected when the turret is inverted.

Ideally, the IMU is placed in the first state, and when the turret is rotated, the Y-axis gyroscope has an output and the X-axis gyroscope and Z-axis gyroscope outputs are all zero, since only the Y-axis direction has an input (the turret rotates about the gravitational acceleration direction), and the X-axis and Z-axis directions do not rotate, and thus no angular velocity can be detected. However, because of the zero offset, and the misalignment angle between the X-axis and Y-axis, the output of the X-axis gyroscope includes components of the input of the X-axis gyroscope and the zero offset. In the first state, since the Z-axis gyroscope has no input, the misalignment angle between the Z-axis and the X-axis has no influence on the output of the X-axis gyroscope. Therefore, the theoretical calculation formula of E0_ gx is shown in formula 1:

e0_ gx bias0_ gx T + scale _ gx T v sin (delta _ o _ gx) (formula 1)

In formula 1, bias0_ gx is the zero offset of the X-axis gyroscope, scale _ gx is the scale factor of the X-axis gyroscope, T is the preset temperature, v is the rotation rate of the turntable, and delta _ o _ gx is the misalignment angle between the X-axis and the Y-axis; scale _ gx T v sin (delta _ o _ gx) is the effect of the Y-axis gyroscope input on the X-axis gyroscope output due to the misalignment angle between the X-axis and the Y-axis.

The theoretical calculation formula of E90_ gx is shown in equation 2:

E90_gx＝bias0_gx*T+scale_gx*T*v*cos(delta_p_gx)*cos(delta_o_gx)

(formula 2)

In equation 2, delta _ p _ gx is the misalignment angle between the X-axis and the Z-axis, and scale _ gx T v cos (delta _ p _ gx) cos (delta _ o _ gx) is the effect of Y, Z axes on the X-axis gyroscope output due to the misalignment angle between the X-axis and the Y, Z axes, respectively.

The theoretical calculation formula of E180_ gx is shown in equation 3:

e180_ gx bias0_ gx T-scale _ gx T v sin (delta _ o _ gx) (equation 3)

E180_ gx differs from E0_ gx in that E0_ gx is data collected when the turntable is rotated forward, and E180_ gx is data collected when the turntable is rotated backward; in the first state, the positive rotation or the negative rotation of the turntable influences the input symbol of the Y-axis gyroscope. The Y-axis output is positive when the turntable is rotated forward and negative when the turntable is rotated backward, and therefore scale _ gx _ T _ v _ sin (delta _ o _ gx) is negative.

The theoretical calculation formula of E270_ gx is shown in equation 4:

E270_gx＝bias0_gx*T-scale_gx*T*v*cos(delta_p_gx)*cos(delta_o_gx)

(formula 4)

Similarly, E180_ gx differs from E0_ gx only in that the turntable rotation direction is reversed, and thus the scale _ gx T v cos (delta _ p _ gx) term is negative in equation 4.

The theoretical calculation formula of E01_ gx is shown in equation 5:

e01_ gx bias0_ gx T + scale _ gx T v sin (delta _ p _ gx) (equation 5)

In equation 5, scale _ gx _ T _ v _ sin (delta _ p _ gx) is the misalignment angle between the X axis and the Z axis, resulting in the influence of the Z axis on the X axis output.

The theoretical calculation formula of E1801_ gx is shown in equation 6:

e1801_ gx ═ bias0_ gx T-scale _ gx T v sin (delta _ p _ gx) (equation 6)

Similarly, E1801_ gx differs from E01_ gx only in that the turntable is rotated in the opposite direction, and thus, the scale _ gx T v sin (delta _ p _ gx) term in equation 6 is negative.

The four parameters, bias0_ gx, scale _ gx, delta _ o _ gx and delta _ p _ gx, are parameters to which the X-axis gyroscope needs to be calibrated.

The following takes the calibration of the X-axis gyroscope as an example, and a specific calibration process is described:

from equation 1 and equation 3, it can be seen that the influence of zero offset on the scaling factor can be eliminated by using E0_ gx-E180_ gx. As can be derived from equations 1 and 3, the misalignment angle scaling factor coupling term scale _ gx _ sin (delta _ o _ gx) between the X axis and the Y axis in the first state can be calculated according to equation 7, and is defined as a _ gx, and equation 7 is as follows:

a _ gx ═ (E0_ gx-E180_ gx)/(2 _ v × T) (formula 7)

Similarly, the influence of zero offset on the scaling factor calculation can be eliminated by using E90_ gx-E270_ gx, and the misalignment angle scaling factor coupling term scale _ gx _ cos (delta _ p _ gx) × cos (delta _ o _ gx) of the Y axis and the Z axis with the X axis can be calculated by using formula 8, and is defined as C _ gx. Equation 8 is as follows:

c _ gx ═ (E90_ gx-E270_ gx)/(2 _ v × T) (formula 8)

Similarly, the influence of zero offset on the scaling factor calculation can be eliminated by using E01_ gx-E1801_ gx, and a scaling factor coupling term scale _ gx _ sin (delta _ p _ gx) of the misalignment angle between the Z axis and the X axis in the third state can be calculated by using formula 9, and is defined as B _ gx. Equation 9 is as follows:

b _ gx ═ (E01_ gx-E1801_ gx)/(2 _ v × T) (formula 9)

Substituting the data obtained from the formulas 7 to 9 into the formula 10, and using trigonometric theory sin²x+cos²The influence of the misalignment angle on the scale factor can be eliminated when x is 1, so that the scale factor after the misalignment angle is eliminated, namely the decoupling misalignment angle and the scale factor, is calculated. Equation 10 is shown below:

since B _ gx ═ scale _ gx sin (delta _ p _ gx), the misalignment angle delta _ p _ gx between the Z axis and the X axis can be derived as shown in equation 11 below:

delta _ p _ gx arcsin (B _ gx/scale _ gx) (equation 11)

Wherein, B _ gx is obtained by solving formula 9, and scale _ gx is obtained by calculating formula 10.

The misalignment angle delta _ o _ gx between the Y axis and the X axis can be derived from a _ gx ═ scale _ gx sin (delta _ o _ gx), and equation 12 is as follows:

delta _ o _ gx arcsin (a _ gx/scale _ gx) (equation 12)

Wherein, a _ gx is calculated by formula 7, and scale _ gx is calculated by formula 10.

The misalignment angle and the scale factor are decoupled using equations 11 and 12.

The zero bias0_ gx of the X-axis gyroscope can be derived from equation 1, as shown in equation 13:

bias0_ gx ═ E0_ gx-scale _ gx ═ v × T × (delta _ o _ gx) (equation 13)

Where E0_ gx is the collected data, scale _ gx is calculated using equation 10, delta _ o _ gx is calculated using equation 12, v is the turntable rotation rate, and T is the preset temperature.

Similarly, when the temperature T is preset, the Y-axis gyroscope is calibrated.

The output data of the Y-axis gyroscope in different states, which are required to be acquired when the parameter calibration is carried out on the Y-axis gyroscope, comprises the following steps:

e0_ gy is the average value of y-axis gyroscope data collected when the IMU is placed in the fourth state and the turntable rotates forwards;

e90_ gy is the average value of y-axis gyroscope data collected when the IMU is placed in the fifth state and the turntable rotates forwards;

e180_ gy is the mean value of y-axis gyroscope data collected when the IMU is placed in the fourth state and the turntable rotates reversely;

e270_ gy is the average value of y-axis gyroscope data collected when the IMU is placed in the fifth state and the turntable rotates reversely;

e01_ gy is the average value of y-axis gyroscope data collected when the IMU is placed in the sixth state and the turntable rotates forwards;

e1801_ gy is the mean value of the y-axis gyroscope data collected when the IMU is placed in the sixth state and the turntable is reversed.

The data collected above is then substituted into the following equation to eliminate the effect of zero bias on the scale factor.

A _ gy ═ (E0_ gy-E180_ gy)/(2 × v × T) (formula 14)

C _ gy ═ (E90_ gy-E270_ gy)/(2 × v × T) (equation 15)

B _ gy ═ (E01_ gy-E1801_ gy)/(2 × v × T) (formula 16)

In the formulas 14-16, v is the rotation rate of the rotary table, T is a preset temperature, and A _ gy represents a coupling term of a scale factor after zero offset is eliminated and a misalignment angle between a Y axis and an X axis; c _ gy represents a coupling term for eliminating the scale factor after zero offset and the misalignment angle between the Y axis and the X, Z axis; b _ gy represents the coupling term to eliminate the scale factor after zero offset and the misalignment angle between the Y and Z axes.

Substituting the data obtained from equations 14 to 16 into equation 17, calculating the scale factor after eliminating the misalignment angle, where equation 17 is as follows:

substituting the B _ gy calculated by the formula 16 and the scale _ gy calculated by the formula 17 into the formula 18 to calculate the true misalignment angle between the Z axis and the Y axis, where the formula 18 is as follows:

delta _ p _ gy ═ arcsin (B _ gy/scale _ gy) (equation 18)

Substituting the a _ gy calculated by the formula 14 and the scale _ gy calculated by the formula 17 into the formula 19 to calculate the true misalignment angle between the Y axis and the X axis, where the formula 19 is as follows:

delta _ o _ gy is arcsin (a _ gy/scale _ gy) (equation 19)

Substituting the calculated scale _ gy, delta _ o _ gy and E0_ gy into formula 20 to calculate the true zero offset of the Y-axis gyroscope, wherein the formula 20 is as follows:

bias0_ gy ═ E0_ gy-scale _ gy _ v × T ·sin (delta _ o _ gy) (equation 20)

Similarly, when the temperature T is preset, the Z-axis gyroscope is calibrated.

The output data of the Z-axis gyroscope in different states, which are required to be acquired when the Z-axis gyroscope is subjected to parameter calibration, comprises the following steps:

e0_ gz is the mean value of Z-axis gyroscope data collected when the IMU is placed in the fourth state and the turntable rotates forwards;

e90_ gz is the mean value of Z-axis gyroscope data collected when the IMU is placed in the third state and the turntable rotates forwards;

e180_ gz is the mean value of Z-axis gyroscope data acquired when the IMU is placed in the fourth state and the turntable is reversely rotated;

e270_ gz is the mean value of Z-axis gyroscope data acquired when the IMU is placed in the third state and the turntable rotates reversely;

e01_ gz is the mean value of Z-axis gyroscope data collected when the IMU is placed in the fifth state and the turntable rotates forwards;

e1801_ gy is the mean of the Z-axis gyroscope data collected when the IMU is placed in the fifth state and the turntable is reversed.

A _ gz ═ (E0_ gz-E180_ gz)/(2 × v × T) (formula 21)

C _ gz ═ (E90_ gz-E270_ gz)/(2 v · T) (equation 22)

B _ gz ═ (E01_ gz-E1801_ gz)/(2 v · T) (equation 23)

In formulas 21-23, v is the rotation rate of the rotary table, T is a preset temperature, and A _ gz represents a coupling term of a scale factor after zero offset is eliminated and a misalignment angle between a Z axis and an X axis; c _ gz represents the coupling term to eliminate the scale factor after zero offset and the misalignment angle between the Z axis and the X, Y axis; b _ gz represents the coupling term to cancel the zero-offset scaling factor and the misalignment angle between the Z and Y axes.

Substituting the data obtained by the formulas 21-23 into a formula 24, and calculating to obtain a scale factor after the misalignment angle is eliminated, wherein the formula 24 is as follows:

substituting the calculated B _ gz and scale _ gz into a formula 25 to calculate a true misalignment angle between the Z axis and the Y axis, wherein the formula 25 is as follows:

delta _ p _ gz arcsin (B _ gz/scale _ gz) (equation 25)

Substituting the calculated A _ gz and scale _ gz into a formula 26 to calculate a true misalignment angle between the Z axis and the X axis, wherein the formula 26 is as follows:

delta _ o _ gz ═ arcsin (A _ gz/scale _ gz) (equation 26)

Substituting the calculated scale _ gz, delta _ o _ gz and E0_ gz into formula 27 to calculate the true zero offset of the Z-axis gyroscope, wherein the formula 27 is as follows:

bias0_ gz ═ E0_ gz-scale _ gz ═ v · T ·sin (delta _ o _ gz) (equation 27)

Then, the zero offset, scale factor and misalignment angle of the X, Y, Z axis gyroscope at different preset temperatures are found in the same way as described above.

For the three-axis accelerometer, the calibration process of the three-axis accelerometer is described by taking the X-axis accelerometer as an example.

The data collected by calibrating the X-axis accelerometer comprises the following steps:

e0_ ax, the IMU is placed in the first state, the turntable is static, and the average value of the acquired x-axis accelerometer output data is obtained;

e90_ ax, the IMU is placed in the second state, the turntable is static, and the average value of the acquired x-axis accelerometer output data is obtained;

e180_ ax, the IMU is placed in a fifth state, the turntable is static, and the acquired mean value of the output data of the accelerometer on the x axis is acquired;

e270_ ax, the IMU is placed in a fourth state, the turntable is static, and the acquired mean value of the output data of the accelerometer on the x axis is acquired;

e01_ ax, the IMU is placed in a third state, the turntable is static, and the average value of the acquired x-axis accelerometer output data is obtained;

e1801_ ax, IMU placed in sixth state, turret still, mean value of the collected x-axis accelerometer output data.

Ideally, the IMU is placed in the first state with the turret stationary, the Y-axis accelerometer has an output, and the X-axis accelerometer and Z-axis accelerometer have outputs that are all zero, since only inputs in the Y-axis direction (gravitational acceleration) and no acceleration inputs in the X-axis and Z-axis directions will detect no acceleration output. However, because of the zero offset, and the misalignment angle between the X-axis and the Y-axis, the output of the X-axis accelerometer includes components of the input of the Y-axis accelerometer on the X-axis and zero offset. It should be noted that, in the first state, since the Z-axis accelerometer has no input, the misalignment angle between the Z-axis and the X-axis has no influence on the output of the X-axis accelerometer. Therefore, the theoretical calculation formula of E0_ ax is shown in equation 28:

e0_ ax (bias 0_ ax T + scale _ ax g sin (delta _ o _ ax) (equation 28)

In formula 28, bias0_ ax is the zero offset of the X-axis accelerometer, scale _ ax is the scale factor of the X-axis accelerometer, T is the preset temperature, g is the acceleration of gravity, and delta _ o _ gx is the misalignment angle between the X-axis and the Y-axis; scale _ ax _ T _ g _ sin (delta _ o _ ax) is the effect of the Y-axis input on the X-axis output due to the misalignment angle of the Y-axis and the X-axis, referred to as the Y-axis and X-axis misalignment angle scaling factor coupling term.

The theoretical calculation formula of E90_ ax is shown in equation 29:

E90_ax＝bias0_ax*T+scale_ax*T*g*cos(delta_p_ax)*cos(delta_o_ax)

(formula 29)

In equation 29, delta _ p _ ax is the term that couples the misalignment angle scaling factors of the X-axis and the Y, Z axis, respectively.

The theoretical calculation formula of E180_ ax is shown in equation 30:

e180_ ax (bias 0_ ax T-scale _ ax T g sin (delta _ o _ ax) (equation 30)

The theoretical calculation formula of E270_ ax is shown in formula 31:

E270_ax＝bias0_ax*T-scale_ax*T*g*cos(delta_p_ax)*cos(delta_o_ax)

(formula 31)

The theoretical calculation formula of E01_ ax is shown in equation 32:

e01_ ax (bias 0_ ax T + scale _ ax T v sin) (equation 32)

In equation 32, scale _ ax _ T _ v _ sin (delta _ p _ ax) is the influence of the misalignment angle between the Z-axis and the X-axis on the output of the X-axis accelerometer due to the input of the Z-axis accelerometer, and is referred to as the Z-axis to X-axis misalignment angle scaling factor coupling term.

The theoretical calculation formula of E1801_ ax is shown in equation 33:

e1801_ ax ═ bias0_ ax T-scale _ ax T v sin (delta _ p _ ax) (equation 33)

From equations 28 and 30, it can be derived that the misalignment angle scale factor coupling term for the X and Y axes, defined as A _ ax, is given by equation 34:

a _ ax ═ (E0_ ax-E180_ ax)/(2 × g × T) (formula 34)

Wherein, the influence of zero offset on the calculation of the scaling factor is eliminated through E0_ ax-E180_ ax.

From equations 29 and 31, the misalignment angle scaling factor coupling term for the X axis and Y, Z axis, respectively, can be derived, defined as C _ ax, as shown in equation 35:

c _ ax ═ (E90_ ax-E270_ ax)/(2 × g × T) (equation 35)

Wherein, the influence of zero offset on the calculation of the scaling factor is eliminated through E90_ ax-E270_ ax.

From equations 32 and 33, the misalignment angle scale factor coupling term for the Z-axis and X-axis can be derived, and is located at B _ ax, as shown in equation 36:

b _ ax ═ (E01_ ax-E1801_ ax)/(2 × g × T) (formula 36)

Wherein, the influence of zero offset on the calculation of the scaling factor is eliminated through E01_ ax-E1801_ ax.

Substituting the data obtained from equations 34 to 36 into equation 37, and calculating to obtain the scale factor after eliminating the misalignment angle, i.e. the decoupling misalignment angle and the scale factor, where equation 37 is as follows:

substituting the calculated B _ ax and scale _ ax into equation 38 can calculate the misalignment angle delta _ p _ ax between the X axis and the Z axis, where equation 38 is as follows:

delta _ p _ ax ═ asin (B _ ax/scale _ ax) (equation 38)

Substituting the calculated A _ ax and scale _ ax into equation 39, the misalignment angle delta _ o _ ax between the Y axis and the X axis can be obtained, and equation 39 is as follows:

delta _ o _ ax ═ asin (a _ ax/scale _ ax) (equation 39)

Substituting the calculated sacle _ ax, delta _ o _ ax and the collected E0_ ax into a formula 40 to calculate a zero-bias 0_ ax of the X-axis accelerometer, wherein the formula 40 is as follows: (g is 1, so does not)

bias0_ ax E0_ ax-sacle _ ax T g sin (delta _ o _ ax) (equation 40)

Wherein T is a preset temperature, and g is a gravity acceleration.

Similarly, at preset temperature T, the Y-axis accelerometer is calibrated, and the data required to be collected in the calibration process includes:

e0_ ay, where the IMU is placed in the sixth state, the turntable is stationary, and the mean of the collected y-axis accelerometer output data;

e90_ ay, the IMU is placed in the fifth state, the turntable is stationary, and the mean value of the collected y-axis accelerometer output data;

e180_ ay, the IMU is placed in a third state, the turntable is stationary, and the mean value of the collected y-axis accelerometer output data;

e270_ ay, the IMU is placed in the first state, the turntable is stationary, and the mean of the collected y-axis accelerometer output data;

e01_ ay, the IMU is placed in the second state, the turntable is stationary, and the mean value of the collected y-axis accelerometer output data;

e1801_ ay, the IMU is placed in the fourth state, the gantry is stationary, and the mean of the collected y-axis accelerometer output data.

A _ ay ═ (E0_ ay-E180_ ay)/(2 × g × T) (formula 41)

C _ ay ═ (E90_ ay-E270_ ay)/(2 × g × T) (formula 42)

B _ ay ═ (E01_ ay-E1801_ ay)/(2 × g × T) (formula 43)

In formulas 41-43, g is a gravity acceleration, T is a preset temperature, and A _ gy represents a coupling term of a scale factor after zero offset is eliminated and a misalignment angle between a Y axis and an X axis; c _ gy represents a coupling term for eliminating the scale factor after zero offset and the misalignment angle between the Y axis and the X, Z axis; b _ gy represents the coupling term to eliminate the scale factor after zero offset and the misalignment angle between the Y and Z axes.

Substituting the calculated A _ gy, B _ gy and C _ gy into a formula 44 to calculate a scale factor of the Y-axis accelerometer after the misalignment angle is eliminated, wherein the formula 44 is as follows:

substituting the calculated B _ ay and scale _ ay into a formula 45 to calculate a true misalignment angle delta _ p _ ay between the Y axis and the Z axis, wherein the formula 45 is as follows:

delta _ p _ ay ═ asin (B _ ay/scale _ ay) (formula 45)

Substituting the calculated A _ ay and scale _ ay into the formula 46 to calculate the misalignment angle delta _ o _ ay between the Y axis and the X axis, wherein the formula 46 is as follows:

delta _ o _ ay ═ asin (a _ ay/scale _ ay) (equation 46)

Substituting the calculated sacle _ ay and delta _ o _ ay and the acquired E0_ ay into equation 47, calculating the zero offset of the Y-axis accelerometer, where equation 47 is as follows:

bias0_ ay _ E0_ ay-sacle _ ay _ T _ g _ sin (delta _ o _ ay) (equation 47)

Similarly, calibrating the Z-axis accelerometer at the preset temperature T by the same method, wherein the data required to be acquired in the calibration process comprises the following steps:

e0_ az, the IMU is placed in the fourth state, the turntable is static, and the acquired mean value of the output data of the z-axis accelerometer is obtained;

e90_ az, the IMU is placed in a third state, the turntable is static, and the acquired mean value of the output data of the z-axis accelerometer is obtained;

e180_ az, the IMU is placed in the second state, the turntable is static, and the acquired mean value of the output data of the z-axis accelerometer is acquired;

e270_ az, the IMU is placed in a sixth state, the rotary table is static, and the acquired mean value of the output data of the z-axis accelerometer is acquired;

e01_ az, the IMU is placed in the fifth state, the turntable is static, and the acquired mean value of the output data of the z-axis accelerometer is obtained;

e1801_ az, IMU placed in the first state, turntable stationary, mean value of collected z-axis accelerometer output data.

A _ az ═ (E0_ az-E180_ az)/(2 × g × T) (formula 48)

C _ az ═ E90_ az-E270_ az)/(2 × g × T) (formula 49)

B _ ay ═ (E01_ az-E1801_ az)/(2 × g × T) (formula 50)

In the formula 48-50, g is gravity acceleration, T is preset temperature, and A _ gz represents a coupling term of a scale factor after zero offset is eliminated and a misalignment angle between a Z axis and an X axis; c _ gz represents the coupling term to eliminate the scale factor after zero offset and the misalignment angle between the Z axis and the X, Y axis; b _ gz represents the coupling term to cancel the zero-offset scaling factor and the misalignment angle between the Z and Y axes.

Substituting the calculated A _ gz, B _ gz and C _ gz into a formula 51 to calculate a scale factor of the Z-axis accelerometer after the misalignment angle is eliminated, wherein the formula 51 is as follows:

substituting the calculated B _ az and scale _ az into a formula 52 to calculate a true misalignment angle delta _ p _ az between the Z axis and the Y axis, wherein the formula 52 is as follows:

delta _ p _ az ═ asin (B _ az/scale _ az) (formula 52)

Substituting the calculated A _ az and scale _ az into a formula 53 to calculate a misalignment angle delta _ o _ az between the Z axis and the X axis, wherein the formula 53 is as follows:

delta _ o _ az ═ asin (a _ az/scale _ az) (formula 53)

Substituting the calculated sacle _ az, delta _ o _ az and the acquired E0_ az into a formula 54 to calculate the zero offset of the Z-axis accelerometer, wherein the formula 54 is as follows:

bias0_ az ═ E0_ az-sacle _ az ═ T ═ g sin (delta _ o _ az) (formula 54)

Then, the zero offset, scale factor and misalignment angle of the X, Y, Z axis accelerometer at different preset temperatures are obtained in the same way.

Corresponding to the embodiment of the IMU calibration method provided by the invention, the invention also provides an embodiment of an IMU calibration device.

Referring to fig. 3, a schematic structural diagram of a calibration apparatus of an IMU according to an embodiment of the present invention is shown in fig. 3, where the apparatus includes: a data acquisition module 110, a parameter calibration module 120, a fitting module 130, and an output model calibration module 140.

The data acquisition module 110 is configured to acquire output data of each sensor in the IMU in different placement states in a preset temperature environment.

The sensor in this embodiment is the uniaxial gyroscope or the uniaxial accelerometer described above.

A parameter calibration module 120, configured to, for any one of the sensors, eliminate an influence of a zero offset scaling factor by using output data of the sensor in different placement states, to obtain a misalignment angle scaling factor coupling term of the sensor; obtaining a corresponding scale factor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term; obtaining the misalignment angle of the sensor by utilizing the misalignment angle scale factor coupling term and the scale factor; and obtaining the zero offset of the sensor by using the scale factor and the misalignment angle.

The fitting module 130 is configured to obtain a fitting coefficient by using the scale factor and the zero offset corresponding to each sensor obtained at different preset temperatures;

and the output model calibration module 140 is configured to substitute the fitting coefficient into a preset output model of the IMU to obtain a calibrated output model of the IMU.

In the IMU calibration method provided in this embodiment, output angular velocity data of each single-axis gyroscope in the IMU is respectively obtained in different placement states and rotation states; simultaneously, respectively acquiring acceleration data output by each single-axis accelerometer in a static state under different placing states; according to the data characteristics output in different placement states, the mutual influence among the parameters is eliminated, namely, the decoupling of the parameters is realized, and the true values of the parameters are obtained, so that the calibration precision of the IMU is improved.

In some embodiments of the present invention, if the sensor is a single-axis gyroscope, when the misalignment angle scaling factor coupling term of the single-axis gyroscope is calculated by the instrument parameter calibration module 120, the method is specifically configured to:

In another embodiment of the present invention, if the sensor is a single-axis gyroscope, when the parameter calibration module 120 obtains the scale factor corresponding to the sensor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term, the parameter calibration module is specifically configured to:

and for any one of the single-axis gyroscopes, utilizing a first misalignment angle scale factor coupling term, a second misalignment angle scale factor coupling term and a third misalignment angle scale factor coupling term to eliminate the influence of the misalignment angle scale factor according to a trigonometric theorem to obtain the scale factor of the single-axis gyroscope.

In some embodiments of the present invention, the parameter calibration module 120, when obtaining the misalignment angle of the sensor by using the misalignment angle scaling factor coupling term and the scaling factor, is specifically configured to:

The calibration process of the accelerometer is similar to that of the gyroscope, and in some embodiments of the present invention, when the parameter calibration module 120 calculates the misalignment angle scaling factor coupling term of the uniaxial accelerometer, the calibration process is specifically configured to:

In another embodiment of the present invention, if the sensor is a uniaxial accelerometer, when the parameter calibration module 120 obtains the scale factor corresponding to the sensor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term, the parameter calibration module is specifically configured to:

and for any uniaxial accelerometer, eliminating the influence of the misalignment angle on the scale factor by utilizing the first misalignment angle scale factor coupling term, the second misalignment angle scale factor coupling term and the third misalignment angle scale factor coupling term according to a trigonometric theorem to obtain the scale factor of the uniaxial accelerometer.

for any one of the single-axis accelerometers, the corresponding misalignment angle scale factor coupling terms when the other two axes except the axis where the single-axis accelerometer is located in the three axes are respectively used as acceleration axes and the scale factors of the single-axis accelerometer are respectively calculated to obtain the misalignment angles between the single-axis accelerometer and the other two axes.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. One of ordinary skill in the art can understand and implement it without inventive effort.

It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

The foregoing is directed to embodiments of the present invention, and it is understood that various modifications and improvements can be made by those skilled in the art without departing from the spirit of the invention.

Claims

1. A calibration method of an Inertial Measurement Unit (IMU), the method comprising:

2. The method of claim 1, wherein the placement state comprises:

3. The method of claim 1, wherein if the sensor is a single-axis gyroscope, the utilizing the output data of the sensor at different placement states to remove the effect of zero-bias scaling factor to obtain the misalignment angle scaling factor coupling term of the sensor comprises:

4. The method of claim 3, wherein if the sensor is a uniaxial gyroscope, the obtaining the scale factor after the elimination of the misalignment angle corresponding to the sensor by using the misalignment angle scale factor coupling term comprises:

5. The method of claim 4, wherein if the sensor is a single axis gyroscope, the deriving the misalignment angle of the sensor using the misalignment angle scaling factor coupling term and the scaling factor comprises:

6. The method of claim 1, wherein if the sensor is a uniaxial accelerometer, the using the output data of the sensor at different placement states to eliminate the influence of zero offset scaling factor to obtain the misalignment angle scaling factor coupling term of the sensor comprises:

7. The method of claim 6, wherein if the sensor is a uniaxial accelerometer, the obtaining the scale factor after the elimination of the misalignment angle corresponding to the sensor using the misalignment angle scale factor coupling term comprises:

8. The method of claim 7, wherein if the sensor is a uniaxial accelerometer, the using the misalignment angle scaling factor coupling term and the scaling factor to obtain the misalignment angle of the sensor comprises:

9. A calibration device of an Inertial Measurement Unit (IMU) is characterized by comprising:

10. The apparatus of claim 9, wherein if the sensor is a single-axis gyroscope, the parameter calibration module is configured to eliminate an influence of a zero-offset scaling factor by using output data of the sensor in different placement states, and when obtaining a misalignment angle scaling factor coupling term of the sensor, specifically:

11. The apparatus of claim 10, wherein if the sensor is a single-axis gyroscope, the parameter calibration module, when obtaining the scale factor corresponding to the sensor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term, is specifically configured to:

12. The apparatus of claim 11, wherein if the sensor is a single-axis gyroscope, the gyroscope parameter calibration module, when obtaining the misalignment angle of the sensor using the misalignment angle scaling factor coupling term and the scaling factor, is specifically configured to:

13. The apparatus of claim 9, wherein if the sensor is a uniaxial accelerometer, the parameter calibration module is configured to eliminate an influence of a zero offset scaling factor by using output data of the sensor in different placement states, and when obtaining a misalignment angle scaling factor coupling term of the sensor, specifically:

14. The apparatus of claim 13, wherein if the sensor is a uniaxial accelerometer, the parameter calibration module, when obtaining the scale factor corresponding to the sensor after the misalignment angle is eliminated by using the misalignment angle scale factor coupling term, is specifically configured to:

15. The apparatus of claim 14, wherein if the sensor is a uniaxial accelerometer, the parameter calibration module, when obtaining the misalignment angle of the sensor using the misalignment angle scaling factor coupling term and the scaling factor, is specifically configured to: