CA3071299A1 - Initial alignment system and method for strap-down inertial navigation of shearer based on optical flow method - Google Patents
Initial alignment system and method for strap-down inertial navigation of shearer based on optical flow method Download PDFInfo
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- CA3071299A1 CA3071299A1 CA3071299A CA3071299A CA3071299A1 CA 3071299 A1 CA3071299 A1 CA 3071299A1 CA 3071299 A CA3071299 A CA 3071299A CA 3071299 A CA3071299 A CA 3071299A CA 3071299 A1 CA3071299 A1 CA 3071299A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C25/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass
- G01C25/005—Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass initial alignment, calibration or starting-up of inertial devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
- G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
- G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
- G01C21/165—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments
Abstract
An initial alignment system and method for strap-down inertial navigation of a shearer based on an optical flow method, comprising an explosion-proof box, a strap-down inertial navigation system, a processor, and a camera. The strap-down inertial navigation system and the processor are mounted in the explosion-proof box. The camera is fixed on a hydraulic support at one side of the shearer by means of the fixed support. A moving image of the shearer is photographed by the camera, and the motion direction and the actual velocity over ground of the shearer are obtained in combination with the optical flow technology. Then, a multi-vector attitude determination equation is derived from a specific force equation of the strap-down inertial navigation. The present invention uses external velocity assistance without the need for a coarse alignment stage to achieve accurate initial alignment of a movable base of the strap-down inertial navigation.
Description
INITIAL ALIGNMENT SYSTEM AND METHOD FOR STRAP-DOWN INERTIAL
NAVIGATION OF SHEARER BASED ON OPTICAL FLOW METHOD
TECHNICAL FIELD
The present invention relates to an initial alignment system and method for a shearer, and in particular, to an initial alignment system and method for strap-down inertial navigation of a shearer based on an optical flow method.
BACKGROUND OF THE INVENTION
Coal is the most widely distributed and most abundant energy resource in the world and has always dominated the world's energy system. Coal is the basic energy and raw material of national economy in China, and accounts for about 70% of primary energy sources. Although China calls for energy conservation and emission reduction and encourages the development of new energy sources in recent years, coal-based energy structure plays an important role in national economic production activities. Therefore, whether the coal industry can be developed healthily and stably is of great significance for energy stability and economic development in China.
In order to realize the linkage of "three machines" for mining, it is of great significance to accurately detect the spatial position and attitude of a shearer, namely, to dynamically position the shearer. In order to realize the position and attitude detection of the shearer, some scholars have proposed the inertial navigation positioning method of the shearer. A
strap-down inertial navigation system refers to directly fixing a gyroscope and an accelerometer on a carrier, measuring triaxial angular velocity and triaxial acceleration information of the running carrier in real time by using inertia sensitive components such as the gyroscope and the accelerometer, and obtaining navigation information such as attitude, velocity and position of the running carrier through high-velocity integration in combination with the initial inertia information of the running carrier. During operation, the strap-down inertial navigation system does not rely on external information, does not radiate energy to the outside, and is not susceptible to interference and damage. It is an autonomous navigation system with the advantages of high data update rate, comprehensive data and high short-term positioning accuracy. The method uses external velocity assistance without the need for a coarse alignment stage to achieve accurate initial alignment of a movable base of the strap-down inertial navigation.
Prior to operation, the inertial navigation system first initializes the navigation information, wherein the process of obtaining the initial attitude information is called initial alignment. However, because the shearer is easily interfered during operation, resulting in shaking of the body of the shearerõ so that the original detection of the rotation angular velocity of the earth by the gyroscope is easily masked by the angular velocity of motion of the bodyõ the conventional analytical method has a too large initial alignment error and even is unusable, and the initial alignment based on the inertial coordinate system has better anti-interference ability for angular shaking.
The algorithm of the initial alignment based on the inertial coordinate system requires the velocity over ground of the shearer. The conventional video velocity measurement algorithms include a background subtraction method, a frame subtraction method, and an optical flow method, etc. The background difference method cannot adapt to the scene change well. The frame subtraction method cannot completely extract the state of all relevant feature points, so that the obtained image is not a pure background image, resulting in inaccurate detection results, which is not conducive to target analysis and velocity detection.
SUMMARY OF THE INVENTION
Regarding the foregoing problems in the prior art, the present invention provides an initial alignment system and method for strap-down inertial navigation of a shearer based on an optical flow method, which improves the error correction for accurate initial alignment of a movable base of the shearer without a coarse alignment stage, to achieve accurate initial alignment of the movable base of the strap-down inertial navigation.
To achieve the foregoing objective, the technical solution adopted by the present invention is: an initial alignment system for strap-down inertial navigation of a shearer based on an optical flow method, comprising an explosion-proof box, a strap-down inertial navigation system, a processor, a fixed support, and a camera, wherein the explosion-proof box is fixedly mounted on the body of the shearer; the strap-down inertial navigation system and the processor are mounted in the explosion-proof box; and the camera is fixed on a hydraulic support at one side of the shearer by means of the fixed support, with the photographing direction of the camera facing toward the shearer.
Further, the processor comprises a micro-processing unit module, a communication module, an alarm module, a data storage module, an isolation circuit, and a power module.
NAVIGATION OF SHEARER BASED ON OPTICAL FLOW METHOD
TECHNICAL FIELD
The present invention relates to an initial alignment system and method for a shearer, and in particular, to an initial alignment system and method for strap-down inertial navigation of a shearer based on an optical flow method.
BACKGROUND OF THE INVENTION
Coal is the most widely distributed and most abundant energy resource in the world and has always dominated the world's energy system. Coal is the basic energy and raw material of national economy in China, and accounts for about 70% of primary energy sources. Although China calls for energy conservation and emission reduction and encourages the development of new energy sources in recent years, coal-based energy structure plays an important role in national economic production activities. Therefore, whether the coal industry can be developed healthily and stably is of great significance for energy stability and economic development in China.
In order to realize the linkage of "three machines" for mining, it is of great significance to accurately detect the spatial position and attitude of a shearer, namely, to dynamically position the shearer. In order to realize the position and attitude detection of the shearer, some scholars have proposed the inertial navigation positioning method of the shearer. A
strap-down inertial navigation system refers to directly fixing a gyroscope and an accelerometer on a carrier, measuring triaxial angular velocity and triaxial acceleration information of the running carrier in real time by using inertia sensitive components such as the gyroscope and the accelerometer, and obtaining navigation information such as attitude, velocity and position of the running carrier through high-velocity integration in combination with the initial inertia information of the running carrier. During operation, the strap-down inertial navigation system does not rely on external information, does not radiate energy to the outside, and is not susceptible to interference and damage. It is an autonomous navigation system with the advantages of high data update rate, comprehensive data and high short-term positioning accuracy. The method uses external velocity assistance without the need for a coarse alignment stage to achieve accurate initial alignment of a movable base of the strap-down inertial navigation.
Prior to operation, the inertial navigation system first initializes the navigation information, wherein the process of obtaining the initial attitude information is called initial alignment. However, because the shearer is easily interfered during operation, resulting in shaking of the body of the shearerõ so that the original detection of the rotation angular velocity of the earth by the gyroscope is easily masked by the angular velocity of motion of the bodyõ the conventional analytical method has a too large initial alignment error and even is unusable, and the initial alignment based on the inertial coordinate system has better anti-interference ability for angular shaking.
The algorithm of the initial alignment based on the inertial coordinate system requires the velocity over ground of the shearer. The conventional video velocity measurement algorithms include a background subtraction method, a frame subtraction method, and an optical flow method, etc. The background difference method cannot adapt to the scene change well. The frame subtraction method cannot completely extract the state of all relevant feature points, so that the obtained image is not a pure background image, resulting in inaccurate detection results, which is not conducive to target analysis and velocity detection.
SUMMARY OF THE INVENTION
Regarding the foregoing problems in the prior art, the present invention provides an initial alignment system and method for strap-down inertial navigation of a shearer based on an optical flow method, which improves the error correction for accurate initial alignment of a movable base of the shearer without a coarse alignment stage, to achieve accurate initial alignment of the movable base of the strap-down inertial navigation.
To achieve the foregoing objective, the technical solution adopted by the present invention is: an initial alignment system for strap-down inertial navigation of a shearer based on an optical flow method, comprising an explosion-proof box, a strap-down inertial navigation system, a processor, a fixed support, and a camera, wherein the explosion-proof box is fixedly mounted on the body of the shearer; the strap-down inertial navigation system and the processor are mounted in the explosion-proof box; and the camera is fixed on a hydraulic support at one side of the shearer by means of the fixed support, with the photographing direction of the camera facing toward the shearer.
Further, the processor comprises a micro-processing unit module, a communication module, an alarm module, a data storage module, an isolation circuit, and a power module.
2 The micro-processing unit module is connected to the communication module, the alarm module, the data storage module, the isolation circuit, and the power module, respectively.
Further, the micro-processing unit module in the processor selects a DSP chip from the T1 company.
Further, the explosion-proof box is a special explosion-proof box for coal mines.
Further, the camera is hingedly connected to the fixed support.
Further, the strap-down inertial navigation system adopts a laser strap-down inertial navigation system, wherein the random drift stability of a laser gyroscope is 0.01 /h, and the bias stability of an accelerometer is le g.
An initial alignment method for strap-down inertial navigation of shearer based on optical flow method comprises the following specific steps:
A. photographing, by a camera with the camera frame rate of 25 frames/s, an image of the environment where a shearer is located, and transmitting the photographed image to a processor;
B. performing, by the processor, gray-scale processing on the photographed image in an image gray-scale mode; when the shearer moves in the photographing environment, so that the photographed target image changes, and the surface motion of the image gray-scale mode is optical flow, determining the moving direction of the shearer based on the principle of principal direction of motion according to the relationship between a motion field and an optical flow field of the shearer;
C. calculating the optical flow velocity of the shearer moving in the image by using the Lucas-Kanade optical flow method, and converting the calculated optical flow velocity in the image into the actual velocity over ground of the shearer, marked Li. b, to obtain velocity information in the motion direction of the shearer;
E. projecting specific force information onto an inertial coordinate system by using a specific force equation of strap-down inertial navigation, to obtain direction change information of the specific force relative to the inertial space as the earth rotates, with the specific force equation being:
Further, the micro-processing unit module in the processor selects a DSP chip from the T1 company.
Further, the explosion-proof box is a special explosion-proof box for coal mines.
Further, the camera is hingedly connected to the fixed support.
Further, the strap-down inertial navigation system adopts a laser strap-down inertial navigation system, wherein the random drift stability of a laser gyroscope is 0.01 /h, and the bias stability of an accelerometer is le g.
An initial alignment method for strap-down inertial navigation of shearer based on optical flow method comprises the following specific steps:
A. photographing, by a camera with the camera frame rate of 25 frames/s, an image of the environment where a shearer is located, and transmitting the photographed image to a processor;
B. performing, by the processor, gray-scale processing on the photographed image in an image gray-scale mode; when the shearer moves in the photographing environment, so that the photographed target image changes, and the surface motion of the image gray-scale mode is optical flow, determining the moving direction of the shearer based on the principle of principal direction of motion according to the relationship between a motion field and an optical flow field of the shearer;
C. calculating the optical flow velocity of the shearer moving in the image by using the Lucas-Kanade optical flow method, and converting the calculated optical flow velocity in the image into the actual velocity over ground of the shearer, marked Li. b, to obtain velocity information in the motion direction of the shearer;
E. projecting specific force information onto an inertial coordinate system by using a specific force equation of strap-down inertial navigation, to obtain direction change information of the specific force relative to the inertial space as the earth rotates, with the specific force equation being:
3 (t) (0+ a. (t))x vh (1) - fib (t) = gb wherein at(t) is the angular velocity of a body coordinate system, U (t) is the projection of the rotation angular velocity of the earth in the body coordinate system, vh(t) is the velocity over ground of the shearer, fcsfh(t) is the specific force measured by an accelerometer in the body coordinate system, and gb is the gravity acceleration of the body coordinate system;
then deriving a multi-vector attitude determination equation from the specific force equation of the strap-down inertial navigation in combination with the velocity over ground o" (t) ; and of the shearer obtained in step D: y(t) = c F. selecting m different integration moments and constructing m non-coplanar vectors in a three-dimensional space:
r cr (i = 1, 2, ...m) = b v and finally, solving an initial attitude matrix of the strap-down inertial navigation by using a Whaba optimal matrix, so as to achieve the initial alignment of the strap-down inertial navigation system.
Compared with the prior art, the present invention utilizes a camera mounted on a hydraulic support, obtains the motion direction and the actual velocity over ground of the shearer in combination with the optical flow technology, derives a multi-vector attitude determination equation from a specific force equation of strap-down inertial navigation, and finally, solves an initial attitude matrix of the strap-down inertial navigation by using a Whaba optimal matrix, so as to achieve the initial alignment of the strap-down inertial navigation system. The present invention uses external velocity assistance without the need for a coarse alignment stage to achieve accurate initial alignment of a movable base of the strap-down inertial navigation. In addition, the combination of optical flow technology and strap-down inertial navigation technology can further reduce the error of the attitude angle of the shearer, improving the error correction effect for the accurate initial alignment of the movable base of the shearer.
then deriving a multi-vector attitude determination equation from the specific force equation of the strap-down inertial navigation in combination with the velocity over ground o" (t) ; and of the shearer obtained in step D: y(t) = c F. selecting m different integration moments and constructing m non-coplanar vectors in a three-dimensional space:
r cr (i = 1, 2, ...m) = b v and finally, solving an initial attitude matrix of the strap-down inertial navigation by using a Whaba optimal matrix, so as to achieve the initial alignment of the strap-down inertial navigation system.
Compared with the prior art, the present invention utilizes a camera mounted on a hydraulic support, obtains the motion direction and the actual velocity over ground of the shearer in combination with the optical flow technology, derives a multi-vector attitude determination equation from a specific force equation of strap-down inertial navigation, and finally, solves an initial attitude matrix of the strap-down inertial navigation by using a Whaba optimal matrix, so as to achieve the initial alignment of the strap-down inertial navigation system. The present invention uses external velocity assistance without the need for a coarse alignment stage to achieve accurate initial alignment of a movable base of the strap-down inertial navigation. In addition, the combination of optical flow technology and strap-down inertial navigation technology can further reduce the error of the attitude angle of the shearer, improving the error correction effect for the accurate initial alignment of the movable base of the shearer.
4 BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic structural diagram according to the present invention;
FIG. 2 is a schematic diagram of a two-dimensional projection of a three-dimensional object moving at a point according to the present invention;
FIG. 3 is a flowchart of detecting the velocity of a shearer in combination with the optical flow method according to the present invention; and FIG. 4 is a flowchart of initial alignment of inertial navigation according to the present invention.
In the drawings, 1: shearer; 2: explosion-proof box; 3: strap-down inertial navigation system; 4: processor; 5: hydraulic support; 6: fixed support; 7: camera.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is further described below.
As shown in the drawings, an initial alignment system for strap-down inertial navigation of a shearer based on an optical flow method comprises an explosion-proof box 2, a strap-down inertial navigation system 3, a processor 4, a fixed support 6, and a camera 7, wherein the explosion-proof box 2 is fixedly mounted on the body of the shearer 1; the strap-down inertial navigation system 6 and the processor 4 are mounted in the explosion-proof box 2; the camera 7 is fixed on a hydraulic support 5 at one side of the shearer 1 by means of the fixed support 6, with the photographing direction of the camera 7 facing toward the shearer 1.
Further, the processor 4 comprises a micro-processing unit module, a communication module, an alarm module, a data storage module, an isolation circuit, and a power module.
The micro-processing unit module is connected to the communication module, the alarm module, the data storage module, the isolation circuit, and the power module, respectively.
Further, the micro-processing unit module of the processor 4 selects a DSP
chip from the TI company. The DSP chip is used to collect and process the data collected by the strap-down inertial navigation system and the camera.
Further, the explosion-proof box 2 is a special explosion-proof box for coal mines.
Further, the camera 7 is hingedly connected to the fixed support 6. This connection mode allows the camera 7 to rotate 360 degrees around the fixed support 6.
Further, the strap-down inertial navigation system 3 adopts a laser strap-down inertial navigation system, wherein the random drift stability of a laser gyroscope is 0.01 /h, and the bias stability of an accelerometer is 10-5 g.
An initial alignment method for strap-down inertial navigation of shearer based on optical flow method comprises the following specific steps.
A. A camera 7 photographs an image of the environment where a shearer 1 is located with the camera frame rate of 25 frames/s, and transmits the photographed image to a processor 4.
B. The processor 4 performs gray-scale processing on the photographed image in an image gray-scale mode. When the shearer 1 moves in the photographing environment, the photographed target image changes, and the surface motion of the image gray-scale mode is optical flow, and the optical flow at each point in the image forms an optical flow field. The optical flow field is a two-dimensional instantaneous velocity field in which a two-dimensional velocity field vector is the projection of a three-dimensional velocity vector of a visible point in the scene on an imaging surface. If a velocity vector is assigned to each pixel point in the image, an image motion field is formed. At a particular moment in the motion, a certain point pi in the image corresponds to a certain point P0 on the shearer.
This correspondence can be obtained from the projection equation. In the case of perspective projection, a line connecting a point in the image to a corresponding point on the object passes through the optical center, and is called an image point connecting line (point ray), as shown in FIG. 2.
The relational model is as follows: assuming that a point pa on the object has a velocity vo relative to the camera, a corresponding projection point pi on the image plane has a velocity v, . The point pa moves by vzdt at a time interval at . The velocity is expressed by the following formula:
-v_ Cirg laL dt dr I
V f dt (1) wherein the motion relationship between To and r: is:
rt . Vii I r (2) wherein f is the focal length of a lens, and z is the distance from the center of the lens to the target. The velocity vector relationship, as shown in formula (3), given to each pixel is obtained by formula (2) and formula (1), and these vectors form the motion field.
Vi civi f (3) The relationship between the motion velocity of the three-dimensional object and the projection velocity of the image plane can be obtained from formula (3).
The moving direction of the shearer 1 is determined based on the principle of principal direction of motion according to the relationship between a motion field and an optical flow field of the shearer 1.
C. The optical flow velocities in the horizontal and vertical directions of each point on the optical flow image are calculated by using the Lucas-Kanade optical flow method, and average values u and v of the optical flow velocities in the horizontal and vertical directions of these feature points are calculated. The calculation formula is as follows:
i ft it m !Zutcx.ry) It n V m ¨ZirMrY) 1 =v , Then, the macroscopic optical velocity of the moving object can be obtained, and the calculation formula is as follows:
1 = ;;274-- ;i According to formula (3), the velocity in pixels can be converted into the velocity in distances, and the actual moving velocity of the shearer can be obtained:
1131 mi kitil Thus, the velocity information in the motion direction of the shearer 1 is obtained.
D. Specific force information is projected onto an inertial coordinate system by using a specific force equation of strap-down inertial navigation, to obtain direction change information the specific force relative to the inertial space as the earth rotates, with the specific force equation being:
= gb wherein cab(t) is the angular velocity of a body coordinate system, N(t) is the projection of the rotation angular velocity of the earth in the body coordinate system, vb(t) is= the velocity over ground of the shearer, fib (t) is the specific force measured by an accelerometer in the body coordinate system, and gb is the gravity acceleration of the body coordinate system.
Both sides are then simultaneously multiplied by a Ch" matrix in combination with the velocity over ground of the shearer I obtained in step D, to obtain the following formula after finishing:
C,': {Cb (0i' (t)+ C'bh (t)(ot (t)+ a (t)) x vh (t) - C (t) fib =
(t) wherein given that u' (t)= (t)ds to v'h" (t)= C (t)+ C 0(40+
a:e(ox vb (t)- C' (t) ft' (t)ds the multi-vector attitude determination equation is obtained as follows:
v' (t) = (t) E. m different integration moments are selected, and m non-coplanar vectors are constructed in a three-dimensional space according to the multi-vector attitude determination equation:
v=Cv r (i = 1, 2, ...m) Multi-vector attitude determination is to solve the optimal attitude matrix Cbr that satisfies the above formula. In order to quantitatively describe the "optimal"
performance (the meaning of the so-called "optimal" is to minimize the weighted sum square of the measurement errors), an index function is constructed:
J( w, vffr ¨ Cbrvib 12 =min 2 , wherein w, is the known weighting coefficient, /w, = 1, and for an equally-weighted average, w, = , and v,r ¨Cbrv,b reflects an inconsistency error of the same physical vector measured in a geographic coordinate system and a carrier coordinate system.
Finally, a constant matrix 010 is found by using the Whaba optimal matrix solving algorithm, to achieve the initial alignment of the strap-down inertial navigation of the shearer I.
FIG. 1 is a schematic structural diagram according to the present invention;
FIG. 2 is a schematic diagram of a two-dimensional projection of a three-dimensional object moving at a point according to the present invention;
FIG. 3 is a flowchart of detecting the velocity of a shearer in combination with the optical flow method according to the present invention; and FIG. 4 is a flowchart of initial alignment of inertial navigation according to the present invention.
In the drawings, 1: shearer; 2: explosion-proof box; 3: strap-down inertial navigation system; 4: processor; 5: hydraulic support; 6: fixed support; 7: camera.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is further described below.
As shown in the drawings, an initial alignment system for strap-down inertial navigation of a shearer based on an optical flow method comprises an explosion-proof box 2, a strap-down inertial navigation system 3, a processor 4, a fixed support 6, and a camera 7, wherein the explosion-proof box 2 is fixedly mounted on the body of the shearer 1; the strap-down inertial navigation system 6 and the processor 4 are mounted in the explosion-proof box 2; the camera 7 is fixed on a hydraulic support 5 at one side of the shearer 1 by means of the fixed support 6, with the photographing direction of the camera 7 facing toward the shearer 1.
Further, the processor 4 comprises a micro-processing unit module, a communication module, an alarm module, a data storage module, an isolation circuit, and a power module.
The micro-processing unit module is connected to the communication module, the alarm module, the data storage module, the isolation circuit, and the power module, respectively.
Further, the micro-processing unit module of the processor 4 selects a DSP
chip from the TI company. The DSP chip is used to collect and process the data collected by the strap-down inertial navigation system and the camera.
Further, the explosion-proof box 2 is a special explosion-proof box for coal mines.
Further, the camera 7 is hingedly connected to the fixed support 6. This connection mode allows the camera 7 to rotate 360 degrees around the fixed support 6.
Further, the strap-down inertial navigation system 3 adopts a laser strap-down inertial navigation system, wherein the random drift stability of a laser gyroscope is 0.01 /h, and the bias stability of an accelerometer is 10-5 g.
An initial alignment method for strap-down inertial navigation of shearer based on optical flow method comprises the following specific steps.
A. A camera 7 photographs an image of the environment where a shearer 1 is located with the camera frame rate of 25 frames/s, and transmits the photographed image to a processor 4.
B. The processor 4 performs gray-scale processing on the photographed image in an image gray-scale mode. When the shearer 1 moves in the photographing environment, the photographed target image changes, and the surface motion of the image gray-scale mode is optical flow, and the optical flow at each point in the image forms an optical flow field. The optical flow field is a two-dimensional instantaneous velocity field in which a two-dimensional velocity field vector is the projection of a three-dimensional velocity vector of a visible point in the scene on an imaging surface. If a velocity vector is assigned to each pixel point in the image, an image motion field is formed. At a particular moment in the motion, a certain point pi in the image corresponds to a certain point P0 on the shearer.
This correspondence can be obtained from the projection equation. In the case of perspective projection, a line connecting a point in the image to a corresponding point on the object passes through the optical center, and is called an image point connecting line (point ray), as shown in FIG. 2.
The relational model is as follows: assuming that a point pa on the object has a velocity vo relative to the camera, a corresponding projection point pi on the image plane has a velocity v, . The point pa moves by vzdt at a time interval at . The velocity is expressed by the following formula:
-v_ Cirg laL dt dr I
V f dt (1) wherein the motion relationship between To and r: is:
rt . Vii I r (2) wherein f is the focal length of a lens, and z is the distance from the center of the lens to the target. The velocity vector relationship, as shown in formula (3), given to each pixel is obtained by formula (2) and formula (1), and these vectors form the motion field.
Vi civi f (3) The relationship between the motion velocity of the three-dimensional object and the projection velocity of the image plane can be obtained from formula (3).
The moving direction of the shearer 1 is determined based on the principle of principal direction of motion according to the relationship between a motion field and an optical flow field of the shearer 1.
C. The optical flow velocities in the horizontal and vertical directions of each point on the optical flow image are calculated by using the Lucas-Kanade optical flow method, and average values u and v of the optical flow velocities in the horizontal and vertical directions of these feature points are calculated. The calculation formula is as follows:
i ft it m !Zutcx.ry) It n V m ¨ZirMrY) 1 =v , Then, the macroscopic optical velocity of the moving object can be obtained, and the calculation formula is as follows:
1 = ;;274-- ;i According to formula (3), the velocity in pixels can be converted into the velocity in distances, and the actual moving velocity of the shearer can be obtained:
1131 mi kitil Thus, the velocity information in the motion direction of the shearer 1 is obtained.
D. Specific force information is projected onto an inertial coordinate system by using a specific force equation of strap-down inertial navigation, to obtain direction change information the specific force relative to the inertial space as the earth rotates, with the specific force equation being:
= gb wherein cab(t) is the angular velocity of a body coordinate system, N(t) is the projection of the rotation angular velocity of the earth in the body coordinate system, vb(t) is= the velocity over ground of the shearer, fib (t) is the specific force measured by an accelerometer in the body coordinate system, and gb is the gravity acceleration of the body coordinate system.
Both sides are then simultaneously multiplied by a Ch" matrix in combination with the velocity over ground of the shearer I obtained in step D, to obtain the following formula after finishing:
C,': {Cb (0i' (t)+ C'bh (t)(ot (t)+ a (t)) x vh (t) - C (t) fib =
(t) wherein given that u' (t)= (t)ds to v'h" (t)= C (t)+ C 0(40+
a:e(ox vb (t)- C' (t) ft' (t)ds the multi-vector attitude determination equation is obtained as follows:
v' (t) = (t) E. m different integration moments are selected, and m non-coplanar vectors are constructed in a three-dimensional space according to the multi-vector attitude determination equation:
v=Cv r (i = 1, 2, ...m) Multi-vector attitude determination is to solve the optimal attitude matrix Cbr that satisfies the above formula. In order to quantitatively describe the "optimal"
performance (the meaning of the so-called "optimal" is to minimize the weighted sum square of the measurement errors), an index function is constructed:
J( w, vffr ¨ Cbrvib 12 =min 2 , wherein w, is the known weighting coefficient, /w, = 1, and for an equally-weighted average, w, = , and v,r ¨Cbrv,b reflects an inconsistency error of the same physical vector measured in a geographic coordinate system and a carrier coordinate system.
Finally, a constant matrix 010 is found by using the Whaba optimal matrix solving algorithm, to achieve the initial alignment of the strap-down inertial navigation of the shearer I.
Claims (2)
1. An initial alignment system for strap-down inertial navigation of a shearer based on an optical flow method, comprising an explosion-proof box (2), a strap-down inertial navigation system (3), a processor (4), a fixed support (6), and a camera (7), wherein the explosion-proof box (2) is fixedly mounted on the body of the shearer (1); the strap-down inertial navigation system (6) and the processor (4) are mounted in the explosion-proof box (2); the camera (7) is fixed on a hydraulic support (5) at one side of the shearer (1) by means of the fixed support (6), with the photographing direction of the camera (7) facing toward the shearer (1);
the processor (4) comprises a micro-processing unit module, a communication module, an alarm module, a data storage module, an isolation circuit, and a power module, the micro-processing unit module being connected to the communication module, the alarm module, the data storage module, the isolation circuit, and the power module, respectively;
the micro-processing unit module in the processor (4) selects a DSP chip from the TI
company;
the explosion-proof box (2) is a special explosion-proof box for coal mines;
the camera (7) is hingedly connected to the fixed support (6);
the strap-down inertial navigation system (3) adopts a laser strap-down inertial navigation system, wherein the random drift stability of a laser gyroscope is 0.01°/h, and the bias stability of an accelerometer is 10 -5 g.
the processor (4) comprises a micro-processing unit module, a communication module, an alarm module, a data storage module, an isolation circuit, and a power module, the micro-processing unit module being connected to the communication module, the alarm module, the data storage module, the isolation circuit, and the power module, respectively;
the micro-processing unit module in the processor (4) selects a DSP chip from the TI
company;
the explosion-proof box (2) is a special explosion-proof box for coal mines;
the camera (7) is hingedly connected to the fixed support (6);
the strap-down inertial navigation system (3) adopts a laser strap-down inertial navigation system, wherein the random drift stability of a laser gyroscope is 0.01°/h, and the bias stability of an accelerometer is 10 -5 g.
2. A method of using the initial alignment system for strap-down inertial navigation of a shearer based on an optical flow method according to claim 1, comprising the following specific steps:
A. photographing, by a camera (7) with the camera frame rate of 25 frames/s, an image of the environment where a shearer (1) is located, and transmitting the photographed image to a processor (4);
B. performing, by the processor (4), gray-scale processing on the photographed image in an image gray-scale mode; when the shearer (1) moves in the photographing environment, so that the photographed target image changes, and the surface motion of the image gray-scale mode is optical flow, determining the moving direction of the shearer (1) based on the principle of principal direction of motion according to the relationship between a motion field and an optical flow field of the shearer 1;
C. calculating the optical flow velocity of the shearer (1) moving in the image by using the Lucas-Kanade optical flow method, and converting the calculated optical flow velocity in the image into the actual velocity over ground of the shearer (I), marked .nu.o, to obtain velocity information in the motion direction of the shearer (1);
D. projecting specific force information onto an inertial coordinate system by using a specific force equation of strap-down inertial navigation, to obtain direction change information of the specific force relative to the inertial space as the earth rotates, with the specific force equation being:
wherein a(t) is the angular velocity of a body coordinate system, .omega.~(t) is the projection of the rotation angular velocity of the earth in the body coordinate system, .nu. b (t) is the velocity over ground of the shearer, .function.~(t) is the specific force measured by an accelerometer in the body coordinate system, and g b is the gravity acceleration of the body coordinate system;
then deriving a multi-vector attitude determination equation from the specific force equation of the strap-down inertial navigation in combination with the velocity over ground of the shearer (1) obtained in step D: vi b o(t)= C~u io(t); and E. selecting m different integration moments and constructing m non-coplanar vectors in a three-dimensional space:
and finally, solving an initial attitude matrix of the strap-down inertial navigation by using a Whaba optimal matrix, so as to achieve the initial alignment of the strap-down inertial navigation system.
A. photographing, by a camera (7) with the camera frame rate of 25 frames/s, an image of the environment where a shearer (1) is located, and transmitting the photographed image to a processor (4);
B. performing, by the processor (4), gray-scale processing on the photographed image in an image gray-scale mode; when the shearer (1) moves in the photographing environment, so that the photographed target image changes, and the surface motion of the image gray-scale mode is optical flow, determining the moving direction of the shearer (1) based on the principle of principal direction of motion according to the relationship between a motion field and an optical flow field of the shearer 1;
C. calculating the optical flow velocity of the shearer (1) moving in the image by using the Lucas-Kanade optical flow method, and converting the calculated optical flow velocity in the image into the actual velocity over ground of the shearer (I), marked .nu.o, to obtain velocity information in the motion direction of the shearer (1);
D. projecting specific force information onto an inertial coordinate system by using a specific force equation of strap-down inertial navigation, to obtain direction change information of the specific force relative to the inertial space as the earth rotates, with the specific force equation being:
wherein a(t) is the angular velocity of a body coordinate system, .omega.~(t) is the projection of the rotation angular velocity of the earth in the body coordinate system, .nu. b (t) is the velocity over ground of the shearer, .function.~(t) is the specific force measured by an accelerometer in the body coordinate system, and g b is the gravity acceleration of the body coordinate system;
then deriving a multi-vector attitude determination equation from the specific force equation of the strap-down inertial navigation in combination with the velocity over ground of the shearer (1) obtained in step D: vi b o(t)= C~u io(t); and E. selecting m different integration moments and constructing m non-coplanar vectors in a three-dimensional space:
and finally, solving an initial attitude matrix of the strap-down inertial navigation by using a Whaba optimal matrix, so as to achieve the initial alignment of the strap-down inertial navigation system.
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| CN201810540173.0 | 2018-05-30 | ||
| PCT/CN2018/115777 WO2019227865A1 (en) | 2018-05-30 | 2018-11-16 | Optical flow method-based coal mining machine strap-down inertial navigation initial alignment system and method |
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| CN109839109B (en) * | 2019-02-25 | 2020-11-24 | 中国矿业大学 | Development machine absolute pose detection method based on image recognition and multi-sensor fusion |
| GB2599380A (en) | 2020-09-30 | 2022-04-06 | Roadmetric Ltd | Measuring vehicle speeds with an uncalibrated camera |
| CN112731930A (en) * | 2020-12-23 | 2021-04-30 | 重庆华渝电气集团有限公司 | Cantilever type excavator control system based on inertial navigation unit |
| CN112901273A (en) * | 2021-01-27 | 2021-06-04 | 中煤科工开采研究院有限公司 | Fully mechanized coal mining face coal mining machine positioning method and system based on coded pattern recognition |
| CN113804913B (en) * | 2021-10-13 | 2022-11-29 | 东南大学 | Method for acquiring rotating speed of spherical motor by using single optical flow sensor |
| CN116295511B (en) * | 2022-12-16 | 2024-04-02 | 南京安透可智能系统有限公司 | Robust initial alignment method and system for pipeline submerged robot |
| CN116358606B (en) * | 2023-05-31 | 2023-08-29 | 中国船舶集团有限公司第七〇七研究所 | Initial coarse alignment method, device, equipment and medium of inertial navigation system |
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