CN103424124A - Nonmagnetic inertial navigation unit calibration method based on image measuring technologies - Google Patents

Abstract

The invention relates to a nonmagnetic inertial navigation unit (IMU) calibration method based on image measuring technologies. A specialized nonmagnetic calibration frame, a geological compass and more than two vidicons are placed in a measuring environment. The space coordinate of the geological compass and the coordinate of the indication ball of the calibration frame of the image measuring analytic system are measured respectively by utilization of a total station, and a unified measuring coordinate system is constructed. An IMU to be measured is fixed on the frame. In the measuring frame, two white and reflective balls are arranged at each of three orthogonal directions of X, Y and Z and used for indicating axial directions. The measuring frame is revolved continuously around the X, Y and Z axes. The corresponding dynamic images are collected synchronously through the vidicons and the data output from the IMU is recorded at the same time. The indication ball space coordinate data is calculated through the mage measuring analytic system, and then the space attitude data of the frame is figured out and used as theory data. Through comparison of the theory data and the space attitude data output from the IMU, the error of the IMU is calculated, and finally the correction coefficient is obtained by utilization of the least square method.

Description

Based on image measurement technology without magnetic inertial navigation unit scaling method

Technical field

The present invention relates to a kind of utilize total powerstation, geologic compass and image measurement analytic system demarcate inertial sensor without the magnetic inertia calibration system.

Background technology

Measure accurately the attitude of rigid body in three dimensions in space flight and aviation, transportation under water, industrial automation, most important in the fields such as virtual reality and human motion Epidemiological Analysis.Motion and rotational trajectory based on accelerometer, earth magnetism and gyrostatic Inertial Measurement Unit (IMU) for measurement target.The researchist utilizes acceleration and angular velocity can extrapolate with respect to gravity side and obtains roll angle (roll) and the angle of pitch (picth), and IMU introduces magnetometer can measure the course angle (heading) of target with respect to the magnetic north direction.

For the demarcation of inertial sensor, traditional mode is to utilize turntable, and IMU is fixed on turntable and is demarcated by the attitude angle that relatively the output data of sensor output and turntable are exported IMU.But, because turntable is driven by motor, the magnetic field that motor produces can badly influence the ground magnetic chip in sensor, so this turntable can't be demarcated the inertial sensor with the ground magnetic chip.Pure manual without the magnetic turntable by gear-driven mode, by manpower, drive turntable to rotate, produce the problem that influence of magnetic field is demarcated while having solved machine operation, but it has been difficult to the stationary problem that sensor signal and turntable are exported.Because turntable is specialized equipment, the installation of equipment needs special place, and very high to site requirements in addition, and expense is very high.

In sum, invent a kind of special place that do not need, utilize traditional common equipment to demarcate the very real meaning that has of inertial sensor change.

Summary of the invention

The objective of the invention is to utilize the equipment commonly used such as video camera, total powerstation and geologic compass to realize the demarcation of IMU. at first utilize total powerstation, geologic compass and image measurement analytic system calibration frame, determine and measure coordinate system (earth coordinates); And then utilization image measurement analytic system, analysis indicates the image of ball by the gage frame under camera record, parse the spatial data that indicates ball, further solve the spatial attitude data of gage frame, and then contrasted with the attitude angle of sensor output, solve the inertial sensor error.

In order to achieve the above object, the invention provides a method of utilizing the optical measurement principle to demarcate inertial sensor.It comprises that one indicates calibration frame ball, that can rotate around X, Y, Z tri-axles, a high-precision geologic compass, two or two above video cameras, a total powerstation and a set of image measurement analysis software with 6.

The coordinate points that indicates ball for the calibration frame by two coordinate points of looking in the mirror of geologic compass and image measurement analytic system is determined the measurement coordinate system, and scaling method comprises a coordinate conversion program.

For by gage frame is indicated to nodule number according to carrying out calculation process, draw the spatial attitude angle of gage frame, scaling method comprises one and indicates nodule number according to handling procedure.

In order to obtain the output data of sensor, scaling method comprises a sensing data and receives software.

Advantage of the present invention:

1, cost is low.Utilize the common apparatus such as video camera, total powerstation to complete the staking-out work of inertial sensor, avoid the procurement price costliness without the magnetic turntable.

2, easy to use, do not need to build special-purpose place.

The accompanying drawing explanation

Below in conjunction with drawings and the embodiments, the present invention is further detailed explanation:

The part diagram that Fig. 1 is the inertial navigation system scaling method middle frame device based on image measurement technology.

Fig. 2 is location survey amount coordinate system operative scenario schematic diagram really in the inertial navigation system scaling method based on image measurement technology.

The staking-out work scene schematic diagram that Fig. 3 is the inertial sensor IMU in the inertial navigation system scaling method based on image measurement technology

Fig. 4 is the process flow diagram of location survey amount coordinate system really in the inertial navigation system scaling method based on image measurement technology.

Fig. 5 is the process flow diagram that the inertial sensor IMU in the inertial navigation system scaling method based on image measurement technology demarcates.

In Fig. 1,1 is the frame knuckles ball; 2 is the white reflection ball; 3 is the sensor fixed position; 4 is column; 5 is handle; 6 is base.

In Fig. 2,1 is left side camera; 2 is the right side video camera; Geologic compass and frame mounting are in the measurement photographed scene of total powerstation and left and right two video cameras; The shooting angle of left and right two video cameras is approximately 90 degree; Total powerstation leans on rear position in the middle of two video cameras.Video camera and total powerstation apart from framework about 5 meters.

In Fig. 3,1 is left side camera; 2 is the right side video camera; Be fixed with the gage frame device of inertial sensor in the measurement photographed scene of left and right two video cameras; The shooting angle of left and right two video cameras is approximately 90 degree; About 5 meters of video camera range observation framework.

Embodiment

For further cognitive and understanding being arranged to feature of the present invention, purpose and function, hereinafter the spy describes relevant concrete use of the present invention, and detailed step is as follows:

At first, according to indicating in Fig. 2, set up and debugged total powerstation and video camera to duty, calibration frame is put to precalculated position, and after guaranteeing the unobstructed measurement of total powerstation and camera system, fixedly all parameters of total powerstation and video camera are until the experiment end, and require not have extraneous high-intensity magnetic field (display near in the experimental site of calibration frame, power supply, electrical equipment, ferrous metal object etc.).

1 determines that local terrestrial magnetic field magnetic north points to

The geologic compass level is put to the calibration frame scope, and on the aiming center line of geologic compass, two of signs indicate ball M1, and M2, utilize total station survey M1, the M2 coordinate data, and then extrapolate M1,2 vectors under total station instrument coordinate system of M2

Utilize rectangular coordinate to turn the spherical coordinates formula and calculate the horizontal angle of this vector under total station instrument coordinate system

Record geologic compass registration angle, theoretical formula is as follows simultaneously:

$M_{\mathrm{sl}}=\frac{M_s-M_l}{\left|\right|M_s-M_l\left|\right|}=(x_{\mathrm{sl}},y_{\mathrm{sl}},z_{\mathrm{sl}})---\left(1\right)$

By calculating the horizontal sextant angle Cangle of magnetic north and total powerstation X-axis.Cangle being compensated on the horizontal angle of total station survey, is that the horizontal initial angle X of total powerstation is consistent with the magnetic north direction again, namely total station instrument coordinate system is transformed into to sky, northeast coordinate system.

2 unified optical imagery systems, total powerstation, IMU coordinate system

Utilize total station survey to have the rigid body framework that 8 above optics indicate ball, the solid space that all sign balls of rigid body framework cover should be able to cover without the magnetic calibration frame.In this experiment, use reflective Archon that 16 diameters are 30mm as mark,, so the output valve of total station survey is chosen as the spherical coordinates pattern, the coordinate data that output indicates ball P is

R is that total station instrument coordinate is that initial point O arrives to the distance between P, the angle that θ is directed line segment OP and z axle forward,

For from positive z axle, from the x axle, by counter clockwise direction, forwarding OM (M is the projection of P at the xoy face) to.The spherical coordinates data that total powerstation is recorded compensate, as formula (4), (5):

R＝r+15mm (4)

θ1＝θ+Cangle (5)

Utilize spherical coordinates to turn rectangular coordinate formula (6)

Wherein, x, y, z is the expression of P in rectangular coordinate system, θ ∈ [0, π],

Simultaneously, utilize video camera to take the image of rigid body framework.

(x, y, z) coordinate is imported in the optics image analysis software, utilize rigid body to indicate anti-sky, the northeast coordinate system of releasing of spherical coordinates.

Now the optical imagery system is sky, northeast coordinate system, can obtain sky, northeast coordinate system after the compensation data Cangle of total powerstation collection.The data that optical imagery system and total powerstation gather and IMU output are unified to the same coordinate system.

3 data acquisitions

Geologic compass and rigid body framework are moved away to the position of calibration frame, IMU is fixed on calibration frame, make the x of IMU coordinate system, y, the z axle parallel framework x that tries one's best, y, z axle.Then, rotator inertia sensor calibration apparatus (Fig. 1) handle 5, column 4 turn an angle (5 degree), again along rotating frame joint ball 1 (5 degree) progressively in the plane of column 4 grooves, data with total station survey Mark ball, record the data of inertial sensor, with scene image under camera record simultaneously.Repeat above step until joint ball, at a rotation with in surface 360 degree, is recorded total data; The cradle head ball 1 progressively along the another one plane of another column groove again by the data of total station survey Mark ball, records the data of sensor and by camera record hypograph data, until joint ball is spent at this rotation with in surface 360 simultaneously.

Turning handle 5 again, repeat top operation, and record indicates the data of ball and the data of sensor, about 5 degree of each rotational angle.Like this repetitive operation until column 4 rotate one week.Record all data.

Inertial sensor caliberating device framework (Fig. 1) 1 is hung up, guarantee that framework, in original scene, stirs framework with hand, use the dynamic data of dynamic image data and sensor under two camera records simultaneously.

4 data analyses

4.1 calculate the calibration frame attitude

6 the every group sign spherical coordinates that utilization collects, determine three mutually orthogonal vector of unit length, represents tri-axles of xyz of measuring table, as shown in formula (7) (8) (9).

$C_{\mathrm{xE}}=\frac{C_{i1}-C_{i2}}{\left|\right|C_{i1}-C_{i2}\left|\right|}---\left(7\right)$

$C_{\mathrm{yE}}=\frac{C_{j1}-{\mathrm{<figure-callout\; id="2"\; label="C\; j"\; filenames="HSA00000721705000021.png,HSA00000721705000031.png"\; state="\{\{state\}\}">C</figure-callout>}}_j}{\left|\right|C_{j1}-{\mathrm{<figure-callout\; id="2"\; label="C\; j"\; filenames="HSA00000721705000021.png,HSA00000721705000031.png"\; state="\{\{state\}\}">C</figure-callout>}}_j\left|\right|}---\left(8\right)$

$C_{\mathrm{zE}}=\frac{C_{k1}-{\mathrm{<figure-callout\; id="2"\; label="C\; k"\; filenames="HSA00000721705000021.png,HSA00000721705000031.png"\; state="\{\{state\}\}">C</figure-callout>}}_k}{\left|\right|C_{k1}-{\mathrm{<figure-callout\; id="2"\; label="C\; k"\; filenames="HSA00000721705000021.png,HSA00000721705000031.png"\; state="\{\{state\}\}">C</figure-callout>}}_k\left|\right|}---\left(9\right)$

These three vector of unit length have defined the rotation matrix of coordinate system of the lower calibrating platform of sky, northeast system coordinate system

By formula (10), mean:

$R_E^C=\left[\begin{array}{ccc}{C}_{\mathrm{xM}}& C_{\mathrm{yM}}& C_{\mathrm{zM}}\end{array}\right]---\left(10\right)$

Due to the strict orthogonal of measuring and platform itself can not be truly

It is not real rotation matrix, therefore we utilize Bar-Itzhack to propose a method, can from inaccurate off plumb rotation matrix, extract the hypercomplex number (can settle accounts attitude) of an optimum, this method need to be set up the symmetric matrix K of 4 * 4, by formula (11), means:

$K=\frac{1}{3}\left[\begin{array}{cccc}{r}_{11}-r_{22}-r_{33}& r_{21}+r_{12}& r_{31}+r_{13}& r_{23}-r_{32}\\ r_{21}+r_{12}& r_{22}-r_{11}-r_{33}& r_{32}+r_{23}& r_{31}-r_{13}\\ r_{31}+r_{13}& r_{32}+r_{23}& r_{33}-r_{11}-r_{22}& r_{12}-r_{21}\\ r_{23}-r_{32}& r_{31}-r_{13}& r_{12}-r_{21}& r_{11}+r_{22}+r_{33}\end{array}\right]---\left(11\right)$

Wherein rmn is exactly the element of the capable n row of formula (17) matrix m, the normalized proper vector that the eigenvalue of maximum that this optimum hypercomplex number is K is corresponding, and formula (12) means:

$q_E^C=\left[\begin{array}{cccc}v4& v1& v2& v3\end{array}\right]---\left(12\right)$

Represent that the calibration frame hypercomplex number means, the attitude angle that is converted to calibration frame according to hypercomplex number to Eulerian angle.

4.2IMU the static attitude footmark is fixed

The angle of pitch ρ of IMU and roll angle γ determine by each axle component of accelerometer, actual to the correction of the angle of pitch and roll angle the accelerometer of IMU demarcated.

According to 6 Fa Huo10 position, position method principles in traditional accelerometer rating test, in conjunction with this characteristic of experiment, Multiple station method has been proposed.Sensor gravitate when static, under day coordinate system, gravity vector g (x, y, z) is (0,0,1) northeastward.The gravity that IMU gathers is (x1, y1, z1) at the component of three axles, and the conversion formula that the sensor coordinates meaned according to Euler's horn cupping is tied to sky, northeast coordinate system is:

$\left[\begin{array}{c}{A}_{x1}\\ A_{y1}\\ {\mathrm{<figure-callout\; id="1"\; label="A\; z"\; filenames="HSA00000721705000021.png"\; state="\{\{state\}\}">A</figure-callout>}}_z\end{array}\right]=\left[\begin{array}{ccc}\cos \mathrm{\&rho;}\cos \mathrm{\&psi;}& \cos \mathrm{\&rho;}\sin \mathrm{\&psi;}& -\sin \mathrm{\&rho;}\\ \cos \mathrm{\&psi;}\sin \mathrm{\&rho;}\sin \mathrm{\&gamma;}-\cos \mathrm{\&gamma;}\sin \mathrm{\&psi;}& \cos \mathrm{\&gamma;}\cos \mathrm{\&psi;}+\sin \mathrm{\&rho;}\sin \mathrm{\&gamma;}\sin \mathrm{\&psi;}& \cos \mathrm{\&rho;}\sin \mathrm{\&gamma;}\\ \cos \mathrm{\&psi;}\sin \mathrm{\&rho;}\cos \mathrm{\&gamma;}+\sin \mathrm{\&gamma;}\sin \mathrm{\&psi;}& -\sin \mathrm{\&gamma;}\cos \mathrm{\&psi;}+\sin \mathrm{\&rho;}\cos \mathrm{\&gamma;}\sin \mathrm{\&psi;}& \cos \mathrm{\&rho;}\cos \mathrm{\&gamma;}\end{array}\right]\&CenterDot;\left[\begin{array}{c}0\\ 0\\ 1\end{array}\right]$

A _x1＝-sinρ

A _y1＝cosρsinγ

A _z1＝cosρcosγ

$\left[\begin{array}{c}{A}_{x1}\\ A_{y1}\\ A_{\mathrm{<figure-callout\; id="1"\; label="z"\; filenames="HSA00000721705000021.png"\; state="\{\{state\}\}">z</figure-callout>}1}\end{array}\right]={[A\_m]}_{3\&times;3}\left[\begin{array}{ccc}\frac{1}{A\_{\mathrm{SC}}_x}& 0& 0\\ 0& \frac{1}{A\_{\mathrm{SC}}_y}& 0\\ 0& 0& \frac{1}{A\_{\mathrm{SC}}_z}\end{array}\right]\&CenterDot;\left[\begin{array}{c}{A}_x-A\_{\mathrm{OS}}_x\\ A_y-A\_{\mathrm{OS}}_y\\ A_z-A\_{\mathrm{OS}}_z\end{array}\right]=\left[\begin{array}{ccc}{\mathrm{ACC}}_{11}& {\mathrm{ACC}}_{12}& {\mathrm{ACC}}_{13}\\ {\mathrm{ACC}}_{21}& {\mathrm{ACC}}_{22}& {\mathrm{ACC}}_{23}\\ {\mathrm{ACC}}_{31}& {\mathrm{ACC}}_{32}& {\mathrm{ACC}}_{33}\end{array}\right]\&CenterDot;\left[\begin{array}{c}\mathrm{Ax}\\ \mathrm{Ay}\\ \mathrm{Az}\end{array}\right]+\left[\begin{array}{c}{\mathrm{ACC}}_{10}\\ {\mathrm{ACC}}_{20}\\ {\mathrm{ACC}}_{30}\end{array}\right]$

${\left[\begin{array}{c}{A}_{x1}\\ A_{y1}\\ A_{z1}\end{array}\right]}^T={\left[\begin{array}{c}{A}_x\\ A_y\\ A_z\\ 1\end{array}\right]}^T\left[\begin{array}{ccc}{\mathrm{ACC}}_{11}& {\mathrm{ACC}}_{21}& {\mathrm{ACC}}_{31}\\ {\mathrm{ACC}}_{12}& {\mathrm{ACC}}_{22}& {\mathrm{ACC}}_{32}\\ {\mathrm{ACC}}_{13}& {\mathrm{ACC}}_{23}& {\mathrm{ACC}}_{33}\\ {\mathrm{ACC}}_{10}& {\mathrm{ACC}}_{20}& {\mathrm{ACC}}_{30}\end{array}\right]$

Utilize least square method, the quadratic sum minimum error method is asked for ACC10 to ACC33, and 12 coefficients, complete the compensation to accelerometer.

The precision of course angle ψ can compensate with reference to the method for traditional turntable compensation.

4.3IMU dynamically attitude angle is demarcated

The sign nodule number certificate of the calibration frame that utilizes the optical imagery system acquisition to arrive, the attitude angle of extrapolating in the calibration frame dynamic process changes, and using it as sensor attitude angle theoretical value and sensor output actual value analyzed, utilize mathematical statistics software, ask for penalty coefficient, adjust dynamic attitude angle output algorithm.

Claims (7)

1. One kind based on image measurement technology without magnetic inertial navigation unit scaling method, calibration system is characterised in that:

   A. place three mutually orthogonal axle X, Y, Z that the witch ball of fixing 6 whites on the aluminum bar of three quadratures indicates framework on described gage frame;

   B. two or aim at gage frame more than two video cameras (camera), between video camera, form an angle;

   C. utilize two volume coordinates of looking in the mirror of total station survey geologic compass, solve the direction of compass, by geologic compass north orientation and attitude ground deflection angle, determine the north orientation of coordinate system;

   D. pass through the sign ball of the calibration frame of total station survey image measurement analytic system, determine the measurement coordinate system (earth coordinates) of video camera;

   E. described IMU is fixed on gage frame;

   Once, after f. described video camera is determined position, need to fix and lock focal length;

   G. the data of synchronous recording view data and IMU;

   H. utilize the image measurement analysis software to calculate the spatial data that gage frame indicates ball, and then solve the spatial attitude data of framework.
2. 2. described according to claim 1, it is characterized in that: the volume coordinate that indicates ball by two coordinates of looking in the mirror of total station survey geologic compass and image measurement analytic system calibration frame. solve geologic compass ground attitude angle according to coordinate, unified the magnetic north direction of the horizontal start angle of total powerstation and measurement.Afterwards, the volume coordinate measured is initialised to measuring system of picture, solves the spatial attitude of framework by volume coordinate, so, the coordinate system of measuring system of picture is unified to earth coordinates.
3. 3. described according to claim 1, gage frame is characterised in that the witch ball by least 6 whites means that tri-of X, Y, Z are axially; Framework can freely rotate around X, Y, Z tri-axles.
4. 4. described according to claim 1, it is characterized in that: utilize image measuring method to measure the spatial attitude angle of tested framework as the reference theoretical value.
5. 5. described according to claim 4, it is characterized in that, at first by the precision of total powerstation or other high-precision angular distance surveying instrument uncalibrated image measuring and analysis system, then, by the tested framework of image taking, by this noncontact, remote metering system, thus created a measurement environment without magnetic for tested IMU.
6. One kind based on image measurement technology without magnetic IMU scaling method, once, after it is characterized in that the precision of uncalibrated image measuring and analysis system, the locus of supposing the sign ball of the gage frame that the image measurement analytic system analyzes is theoretical value.
7. 7. according to the spatial attitude Data Comparison of tried to achieve gross data and IMU output, obtain the error of IMU, finally utilize least square method to try to achieve correction coefficient.

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