An airborne high-precision fiber-optic inertial measurement device and integrated navigation method

Abstract

The application provides an airborne high-precision fiber-optic inertial measurement device and a combined navigation method, which can simultaneously output angular velocity information, visual acceleration information, geographical position information, speed information and attitude information of a measured carrier in three orthogonal sensitive axes. The gyro circuit board is distributed and placed, so that the zero offset stability and the first power-on stability of the gyro are effectively improved, the influence of temperature on the gyro is reduced, and the gyro precision is improved; the I / F conversion circuit board is placed between the base and the bottom cover, so that the influence of the heat dissipation of the I / F conversion circuit board on the system body is weakened, the environmental temperature of the gyro body is effectively improved, and a gyro with higher precision is realized. The combined navigation method is suitable for the case that the satellite receiver information is lost, image information obtained by the binocular camera is used to solve the pose information of the carrier, and the inertial navigation information calculated by the fiber-optic inertial measurement device is filtered and fused, so that the navigation precision of the fiber-optic inertial measurement device is improved.

Description

TECHNICAL FIELD

[0001] The application relates to an airborne high-precision fiber-optic inertial measurement device and a combined navigation method, in particular to a miniaturized, light-weight, high-precision fiber-optic inertial measurement device for unmanned aerial vehicle (UAV) inertial navigation in the field of aerospace, and belongs to the technical field of inertial measurement. BACKGROUND

[0002] As a rapidly developing unmanned equipment system, the unmanned aerial vehicle (UAV) can perform functions such as rapid reconnaissance, ground attack and defense, missile guidance and load in the military field, and plays an increasingly important role in the 21st century. It is a modern weapon relying on technology and information for iteration and improvement. At the same time, its role in the civil field is also particularly prominent, such as participating in disaster relief in geological disasters, crop detection and cultivation, geographic mapping and other purposes.

[0003] As an important single device of the flight control system of the unmanned aerial vehicle (UAV), the inertial measurement device has a significant influence on the flight reliability and flight precision. The fiber-optic inertial measurement device is widely used in the military and civil unmanned aerial vehicle (UAV) fields due to its advantages such as light weight, miniaturization, low power consumption, high precision and space environment adaptability.

[0004] The fiber-optic inertial measurement device is a pure inertial measurement device, and an inertial measurement unit composed of an optical fiber gyroscope and an accelerometer is the main part. By outputting the angular velocity, linear acceleration of three orthogonal axes, the velocity information, attitude information and geographic position information of the carrier in different time of the geographic coordinate system can be calculated through the integral iteration algorithm. Its main features are as follows: (1) high precision: the navigation precision is better than 1 nautical mile / hour; (2) miniaturization: reasonable and compact internal layout, high space utilization rate, small size and low power consumption.

[0005] In the prior art, the fiber-optic inertial measurement device has a relatively large volume under the same precision, and the device with the same volume has relatively low precision. In the prior art, when the pose information of the carrier calculated by the visual navigation system is used as the measurement information to correct the pure inertial navigation information, the visual navigation information is not updated through closed-loop optimization, the precision of the observation information is low, the precision of the navigation information calculated by the combined navigation after the filtering correction is relatively low, and in the prior art, two subsystems are usually built for tight coupling or loose coupling systems without association between feature vectors during filtering fusion. The former has high algorithm complexity and cannot meet the real-time requirement of the unmanned application equipment system for combined navigation, and the latter cannot improve the navigation and positioning precision in an effective time. SUMMARY

[0006] The present application aims at overcoming the above-mentioned deficiencies of the prior art, and provides an airborne high-precision optical fiber inertial measurement device and a combined navigation method.

[0007] The present application aims at overcoming the above-mentioned deficiencies of the prior art, and provides an airborne high-precision optical fiber inertial measurement device and a combined navigation method.

[0008] The present application aims at overcoming the above-mentioned deficiencies of the prior art, and provides an airborne high-precision optical fiber inertial measurement device and a combined navigation method.

[0009] The gyro digital board is embedded on the gyro meter head, three mutually orthogonal gyro meter heads are installed on the side and top of the gyro body; the three gyro meter heads share one light source, the gage assembly is located on the inner side of the gyro body and connected with the gyro body, the gyro body is installed on the base, the electric connector is installed on the side end of the base, the bottom cover as the bottom end of the measurement device is located below the base, the I / F conversion circuit and the DSP circuit are installed between the base and the bottom cover in the order from top to bottom, and the bottom cover realizes the closure of the circuit; the cover and the bottom cover are installed on the base, the gyro body is installed inside the cover through four groups of waist vibration absorbers, and the cover realizes the closure of the measurement device shell.

[0010] Further, the light source adopts one three-axis shared erbium source box.

[0011] Further, the outer envelope size of the optical fiber inertial measurement device is not greater than 150mm*140mm*127mm, the weight is not greater than 3.5Kg, and the normal temperature power consumption is not greater than 18W.

[0012] Further, the I / F conversion circuit and the DSP circuit are arranged between the base and the bottom cover away from the gyro body, and when the device is in the powered-on state, the ambient temperature of the gyro meter head is ensured.

[0013] Further, the present application further provides a combined navigation method, which comprises the following steps:

[0014] (1) the DSP circuit obtains the angular velocity information sensitive to the gyro, obtains the specific force information sensitive to the gage assembly, and performs first integration on the obtained angular velocity information and specific force information to obtain the three-axis attitude angle and velocity information of the optical fiber inertial measurement device, and performs second integration on the velocity information to obtain the position information of the optical fiber inertial measurement device; the optical fiber inertial measurement device sends the integrated information to the airborne computer through the device serial port; the data sampling period of the optical fiber inertial measurement device is 1ms.

[0015] (2) The visual positioning system and the optical fiber inertial measurement device are installed on the same airborne platform, and the two sub-navigation systems are used as the positioning information input source of the combined navigation system of the airborne platform;

[0016] (3) The coordinate system of the visual positioning system is converted from the world coordinate system to the camera coordinate system, and the conversion matrix is calculated;

[0017] The data sampling frequency of the visual navigation system is 30Hz Z When it performs pose calculation, it involves four coordinate systems: world coordinate system, camera coordinate system, image coordinate system, and pixel coordinate system. The pose calculated in the visual navigation system is the camera coordinate system relative to the world coordinate system, and the coordinates of the road marker point in the real world in the world coordinate system are defined as P w = [x w , y w , z w ] T The coordinates in the camera coordinate system are represented as P c = [x c , y c , z c ] T The conversion relationship between the two positions is:

[0018]

[0019] Among them, R represents the rotation matrix from the world coordinate system to the camera coordinate system, T represents the translation length from the origin of the rotated world coordinate system to the origin of the camera coordinate system;

[0020] (4) The coordinate system of the visual navigation system is converted from the camera coordinate system to the image coordinate system, and the conversion matrix is calculated;

[0021]

[0022] Among them: The physical meaning of R is the extrinsic matrix of the camera;

[0023] The conversion relationship between the coordinates of the pixel point in the camera coordinate system and in the image coordinate system is as follows:

[0024]

[0025] The physical meaning of f is the focal length of the camera, and f x = f y = f;

[0026]

[0027] (5) Calculate the conversion matrix of camera coordinate system-image coordinate system-pixel coordinate system in visual navigation system;

[0028]

[0029] The physical meaning of M is the intrinsic matrix of the camera, which and the extrinsic matrix can be obtained by calibration; x and c y are the unit length of a pixel point in the x-axis and y-axis, respectively, u x and v y represent the horizontal and vertical coordinates of the pixel point in the pixel coordinate system;

[0030] Determine the transformation relationship between the coordinates P w = [x w , y w , z w ] T of the P point in the global reference system and the coordinates P uv = [u, v] T in the pixel coordinate system:

[0031]

[0032] (6) Establish the observation equation of the visual navigation system to provide a mathematical platform for calculating the three-dimensional coordinates p of the pixel point in the world coordinate system;

[0033] The observation equation of the visual navigation system is:

[0034] Z = h(X, Y)

[0035] Where: Z represents the observation of the feature point on the projection plane, X represents the calculated camera pose, represented by Lie algebra ξ, and Y represents the three-dimensional coordinate estimation of the road marker point;

[0036] h(ξ, p) represents the pixel coordinates obtained after re-projection, so the expression of the error function is:

[0037] e = Z - h(ξ, p)

[0038] Label the actual pixel coordinates of all feature points and the camera state ξ, and let Z ij be the observation produced by the i-th frame camera in state ξ i , on the road marker p j The cost function represents the error function to be minimized, and the expression is:

[0039]

[0040] The optimal estimation is completed by continuously iterating to minimize the cost function, and the ξ and p at this time are calculated, i.e. the state of the airborne platform and the three-dimensional coordinates of the landmark points in the world coordinate system are calculated;

[0041] (7) The position information ξ of the airborne platform calculated by the visual positioning system is also sent to the airborne computer, so as to provide input information for multi-source fusion of the integrated navigation system;

[0042] (8) The initial transformation matrix between the geographic coordinate system and the world coordinate system is calculated;

[0043] The longitude, latitude, pitch, roll and heading angles and the northeast sky speed calculated by the inertial coordinate system are relative to the geographic coordinate system, and the pose information in the two coordinate systems needs to be unified and calibrated when the fusion is performed, the geographic coordinate system is set as the N system, i.e. the east-north-sky coordinate system, the world coordinate system is set as the W system, and the transformation matrix between the two coordinate systems is The transformation matrix between the two coordinate systems is calculated by calibration when the aircraft is installed, and the position information calculated by the two sub-navigation systems is projected into the same coordinate system by using the initial transformation matrix calculated by calibration;

[0044] (9) The state equation of the integrated navigation system is established;

[0045] The state vector of the integrated navigation system is:

[0046]

[0047] Among them: represents a unit quaternion, representing the rotation of the carrier from the inertial coordinate system to the world coordinate system, b g represents the zero offset of the gyroscope, represents the specific position of the carrier in the global world coordinate system, a represents the zero offset of the gyroscope, represents the specific position of the carrier in the global world coordinate system, represents the position of the camera in the global world coordinate system when the Nth image is shot, represents the rotation of the camera relative to the global world coordinate system when the Nth image is shot;

[0048] (10) The observation equation of the integrated navigation system is established;

[0049] (11) The state update and observation update of the integrated navigation system are completed, the filtering is realized, and the navigation positioning is completed.

[0050] Compared with the prior art, the present application has the following advantages:

[0051] (1) the application adopts the design scheme of compartmentalization, so that the outer envelope size of the optical fiber inertial measurement device is not greater than 150mm*140mm*127mm, the weight is not greater than 3.5Kg, the normal temperature power consumption is not greater than 18W, under the premise of ensuring that the optical fiber inertial measurement device realizes high-precision measurement, lightweight and miniaturization design is realized.

[0052] (2) the gyro circuit board is distributed and placed, and the I / F conversion circuit board is placed on the base, so that the lightweight and miniaturization characteristics are ensured, the environmental temperature of the gyro is improved under the power-on state of the device, and the gyro precision is greatly improved.

[0053] (3) the visual navigation system as a subsystem in the integrated navigation system does not depend on external factors, can realize real-time navigation calculation in all geographical environments and all weather conditions, can correct the position information of pure inertial navigation calculation when the satellite receiver information is lost, and the integrated navigation algorithm can use the position information estimated by the visual navigation system to correct the position information caused by long-time integral calculation of pure inertial navigation, so as to correct the three-axis attitude angle and improve the navigation precision. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is an outline structure schematic diagram of the application;

[0055] Figure 2 It is an internal structure schematic diagram of the application;

[0056] Figure 3 It is a flow chart of the integrated navigation method; DETAILED DESCRIPTION

[0057] The application will be further described in detail in combination with the drawings and specific examples:

[0058] As shown in Figure 1 and Figure 2 , the application proposes an airborne high-precision optical fiber inertial measurement device, which comprises: an outer cover 1, a gyro body 2, a gyro meter head 3, a gyro digital board 4, a light source 5, a meter assembly 6, a base 7, an electrical connector 8, a bottom cover 9, an I / F conversion circuit 10, a DSP circuit 11.

[0059] The gyro digital board 4 is embedded on the gyro meter head 3, three mutually orthogonal gyro meter heads 3 are installed on the side and top of the gyro body 2; the three gyro meter heads 3 share one light source 5, the adding table assembly 6 is located on the inner side of the gyro body 2 and connected with the gyro body 2, the gyro body 2 is installed on the base 7, the electric connector 8 is installed on the side end of the base 7, the bottom cover 9 is located below the base 7 as the bottom end of the measuring device, the I / F conversion circuit 10 and the DSP circuit 11 are installed between the base 7 and the bottom cover 9 in the order from top to bottom, and the bottom cover 9 realizes the closure of the circuit; the outer cover 1 and the bottom cover 9 are installed on the base 7, the gyro body 2 is installed inside the outer cover 1 through four groups of waist shock absorbers, and the outer cover 1 realizes the closure of the shell of the measuring device.

[0060] Preferably, the light source 5 adopts an erbium source box shared by three axes.

[0061] Preferably, the outer envelope size of the fiber optic inertial measuring device is not greater than 150mm*140mm*127mm, the weight is not greater than 3.5Kg, and the normal temperature power consumption is not greater than 18W.

[0062] Preferably, the I / F conversion circuit 10 and the DSP circuit 11 are arranged between the base 7 and the bottom cover 9 away from the gyro body, and when the device is in a powered state, the ambient temperature of the gyro meter head is ensured.

[0063] The device of the application provides an RS-422 external output interface, can simultaneously output the angular velocity information, visual acceleration information, geographical position information, speed information and attitude information of the measured carrier in three orthogonal sensitive axes, the gyro circuit board is distributed and placed, the zero offset stability and the one-time power-on stability of the gyro can be effectively improved, the influence of temperature on the gyro is reduced, and the gyro precision is improved; the I / F conversion circuit board is placed between the base and the bottom cover, the influence of the heat dissipation of the I / F conversion circuit board on the system body is weakened, the ambient temperature of the gyro body is effectively improved, and a gyro with higher precision is realized. The combined navigation method of the application is suitable for when the satellite receiver information is lost, using the image information obtained by the binocular camera to solve the pose information of the carrier and the inertial navigation information iteratively calculated by the fiber optic inertial measuring device to carry out filtering and fusion, constructing a multi-source filtering combined navigation system, improving the navigation precision of the fiber optic inertial measuring device, and ensuring the reliability of flight in multiple flight boundary states.

[0064] The application further provides a combined navigation method based on the fiber optic inertial measuring device, which comprises the following steps:

[0065] (1)DSP circuit acquires angular velocity information sensitive to the gyroscope, acquires specific force information sensitive to the accelerometer assembly, and performs first integration on the obtained angular velocity information and specific force information to obtain three-axis attitude angle and velocity information of the fiber-optic inertial measurement device, performs second integration on the velocity information to obtain position information of the fiber-optic inertial measurement device, and sends the integrated information to the airborne computer through a device serial port; the data sampling period of the fiber-optic inertial measurement device is 1 ms;

[0066] (2) install the visual positioning system and the fiber-optic inertial measurement device two sub-navigation systems on the same airborne platform, and use the two sub-navigation systems as the positioning information input source of the combined navigation system of the airborne platform, as shown in Figure 3 ;

[0067] (3) convert the coordinate system of the visual positioning system from the world coordinate system to the camera coordinate system, and calculate the conversion matrix;

[0068] The data sampling frequency of the visual navigation system is 30 Hz Z , and four coordinate systems are involved in the pose solution thereof: the world coordinate system, the camera coordinate system, the image coordinate system, and the pixel coordinate system. The pose solved in the visual navigation system is the camera coordinate system relative to the world coordinate system, and the coordinates of a road marker point in the real world in the world coordinate system are defined as P w = [x w , y w , z w ] T , the coordinates in the camera coordinate system are represented as P c = [x c , y c , z c ] T , and the conversion relationship between the two positions is:

[0069]

[0070] wherein, represents a rotation matrix from the world coordinate system to the camera coordinate system, represents the translation length from the origin of the rotated world coordinate system to the origin of the camera coordinate system;

[0071] (4) convert the coordinate system of the visual navigation system from the camera coordinate system to the image coordinate system, and calculate the conversion matrix;

[0072]

[0073] wherein: the physical meaning of the camera extrinsic matrix is;

[0074] The coordinate transformation relationship between the pixel point in the camera coordinate system and the image coordinate system is as follows:

[0075]

[0076] The physical meaning of f is the focal length of the camera, and f x = f y = f.

[0077]

[0078] (5) Calculate the conversion matrix of the camera coordinate system-image coordinate system-pixel coordinate system in the visual navigation system;

[0079]

[0080] The physical meaning of M is the intrinsic matrix of the camera, and the intrinsic matrix and the extrinsic matrix of the camera can be obtained by calibration; c x and c y are the unit length of a pixel point in the x-axis and y-axis, respectively, u x and v y represent the horizontal and vertical coordinates of the pixel point in the pixel coordinate system;

[0081] Determine the coordinate P of the point P in the global reference system P w = [x w , y w , z w ] T and the transformation relationship between its coordinate P uv = [u, v] T in the pixel coordinate system:

[0082]

[0083] (6) Establish the observation equation of the visual navigation system to provide a mathematical platform for calculating the three-dimensional coordinates p of the pixel point in the world coordinate system;

[0084] The observation equation of the visual navigation system is:

[0085] Z = h (X, Y)

[0086] Where: Z represents the observation of the feature point on the projection plane, X represents the calculated camera pose, represented by Lie algebra ξ, and Y represents the three-dimensional coordinate estimation of the road marker point;

[0087] h (ξ, p) represents the pixel coordinates obtained after re-projection, so the expression of the error function is:

[0088] e = Z - h (ξ, p)

[0089] Let the actual pixel coordinates of all feature points and the camera state ξ be denoted as Z ij The camera state ξ i of the i-th frame j The generated observation, the cost function represents an error function to be minimized, and the expression is:

[0090]

[0091] The cost function is minimized through continuous iteration, that is, the optimal estimation is completed, and the ξ and p at this time are calculated, that is, the state of the airborne platform and the three-dimensional coordinates of the landmark points in the world coordinate system are calculated;

[0092] (7) The position information ξ of the airborne platform calculated by the visual positioning system is also sent to the airborne computer, providing input information for multi-source fusion of the integrated navigation system;

[0093] (8) Calculate the initial transformation matrix between the geographic coordinate system and the world coordinate system;

[0094] The longitude, latitude, pitch, roll, and heading angles calculated in the inertial coordinate system are relative to the geographic coordinate system. When the pose information in the two coordinate systems is fused, the two coordinate systems must be unified and calibrated first. Let the geographic coordinate system be N, that is, the East-North-Sky coordinate system, and the world coordinate system be W. The transformation matrix between the two coordinate systems is The transformation matrix between the two coordinate systems is calculated through calibration when the aircraft is installed. The initial transformation matrix calculated through calibration is used to project the position information calculated by the two sub-navigation systems into the same coordinate system.

[0095] (9) Establish the state equation of the integrated navigation system;

[0096] The state vector of the integrated navigation system is:

[0097]

[0098] Among them: represents a unit quaternion, representing the rotation of the carrier from the inertial coordinate system to the world coordinate system, b g represents the zero offset of the gyroscope, represents the velocity of the carrier in the global world coordinate system b a represents the zero offset of the gyroscope, represents the specific position of the carrier in the global world coordinate system, represents the position of the camera in the global world coordinate system when the N-th image is taken, represents the rotation of the camera relative to the global world coordinate system when the N-th image is taken;

[0099] The state vector includes the inertial system state and the state of N cameras, and the state of the camera at the current time is estimated according to the state of the inertial system currently calculated and the coordinate transformation matrix between the inertial system and the vision system and and added to the state vector

[0100] The state quantity of the IMU in the state vector is composed of two parts, which are respectively: an estimated quantity and an error quantity

[0101]

[0102]

[0103]

[0104] When constructing the state equation of the integrated navigation system, only the state of the inertial system is considered, so the estimated state quantity is taken as:

[0105]

[0106] The system estimated state quantity is represents the pose state of the inertial system at time i

[0107] The error state quantity is defined as:

[0108]

[0109] In the state prediction process, the current and previous states do not have pose changes, so the process model is zero:

[0110]

[0111] In the design of the integrated navigation system, the estimated state and the error state are as follows:

[0112]

[0113] The inertial system error state equation is: Taylor expansion is performed on A c to obtain:

[0114]

[0115] Q c represents the covariance matrix of the noise:

[0116]

[0117] The inertial system state quantity is the sum of the state estimation quantity and the state error quantity, and therefore to obtain the update result of the state quantity, the estimation value and the error value need to be updated:

[0118]

[0119]

[0120]

[0121]

[0122] T l is the state transition matrix of the estimation quantity; T h is the state transition matrix of the error quantity;

[0123] The present combined navigation system is used for completing the observation update of the front end by using the environmental image information obtained by the binocular camera sensor in the visual positioning system, the observation update process is used for estimating the position of the feature point by using the historical camera, when the same feature points can be observed by multiple images, the geometric constraint can be formed between the images, and the state vector is updated by using the geometric constraint.

[0124] The residual error model corresponding to each camera state is:

[0125]

[0126] (10) establishing the observation equation of the combined navigation system;

[0127] The observation equation of the combined system is:

[0128]

[0129]

[0130]

[0131]

[0132] is the pixel coordinate of the feature point f j in the camera coordinate system C i , is the pixel coordinate of the feature point f j in the camera coordinate system C i , and the residual error model is minimized to continuously realize the observation update.

[0133] (11) completing the state update and the observation update of the combined navigation system, realizing the filtering, and completing the navigation positioning.

[0134] Embodiment:

[0135] The overall composition design is shown in the schematic diagram of the outer structure of the fiber optic inertial measurement device Figure 1 and the schematic diagram of the internal structure is shown in Figure 2 The fiber optic inertial measurement device comprises a base, an outer cover, a bottom cover, a gyro body, a three-axis common light source (an erbium source box), a gyro circuit, a system circuit, an I / F conversion circuit, a three-axis integrated gyroscope, an electrical connector, a power supply, four sets of shock absorbers, and a gage assembly; three mutually orthogonal gyroscopes are installed on the side and top of the body; three accelerometers are located on the inner side of the gyroscopes and connected to the body, the erbium source box is installed at the lower part of the body, the gyro circuit is installed at the lower part of the erbium source box and connected to the body, the body is installed inside the shell through the waist four sets of shock absorbers, the power supply, the connector, the system circuit, the outer cover and the bottom cover are installed on the base, the bottom cover realizes the sealing of the system circuit, and the outer cover realizes the sealing of the shell.

[0136] The fiber optic inertial measurement device adopts a design scheme of separate cabins, so that the outer envelope size of the fiber optic inertial measurement device is not greater than 150mmx140mmx127mm, the weight is not greater than 3.5Kg, and the normal temperature power consumption is not greater than 18W.

[0137] The airborne high-precision fiber optic inertial measurement device has the characteristics of light weight and miniaturization, and the gyro circuit board is distributed and placed, and the I / F conversion circuit board is placed on the base, so that the environmental temperature of the gyroscope is improved under the condition of power-on of the device, which has great significance for improving the gyro precision.

[0138] The integrated navigation method reduces the algorithm complexity of the algorithm on the basis of realizing high-precision navigation and positioning, can improve the calculation speed, and meets the real-time requirement.

[0139] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

Claims

1. A combined navigation method based on a fiber optic inertial measurement unit, characterized in that... The steps include the following: (1) The DSP circuit acquires the angular velocity information sensitive by the gyroscope and the relative force information sensitive by the addition component. The acquired angular velocity information and relative force information are integrated once to obtain the three-axis attitude angle and velocity information of the fiber optic inertial measurement device. The velocity information is integrated again to obtain the position information of the fiber optic inertial measurement device. The fiber optic inertial measurement device sends the integrated information to the airborne computer through the device serial port. The data sampling period of the fiber optic inertial measurement device is 1ms. (2) The two sub-navigation systems, the visual positioning system and the fiber optic inertial measurement device, are installed on the same airborne platform. The two sub-navigation systems serve as the source of positioning information for the combined navigation system of the airborne platform. (3) Transform the coordinate system of the visual positioning system from the world coordinate system to the camera coordinate system and calculate the transformation matrix; (4) Transform the coordinate system of the visual navigation system from the camera coordinate system to the image coordinate system, and calculate the transformation matrix; (5) Calculate the transformation matrix from camera coordinate system to image coordinate system to pixel coordinate system in the visual navigation system; (6) Establish the observation equation of the visual navigation system to provide a mathematical platform for calculating the three-dimensional coordinates p of the pixel in the world coordinate system; (7) The position information ξ of the airborne platform calculated by the visual positioning system is also sent to the airborne computer to provide input information for the multi-source fusion of the integrated navigation system; (8) Calculate the initial transformation matrix between the geographic coordinate system and the world coordinate system; (9) Establish the state equations of the integrated navigation system; The state vector of the integrated navigation system is: in: Representing a unit quaternion, characterizing the rotation of a carrier from the inertial coordinate system to the world coordinate system, b g This indicates the zero bias of the gyroscope. The velocity b of the carrier in the global world coordinate system. a This indicates the zero bias of the gyroscope. This indicates the specific location of the carrier in the global world coordinate system. This represents the position of the camera in the global world coordinate system when the Nth frame is captured. This represents the camera's rotation relative to the global world coordinate system when the Nth frame is captured; (10) Establish the observation equations for the integrated navigation system; (11) The state update and observation update of the integrated navigation system were completed, filtering was implemented, and navigation and positioning were completed.

2. The integrated navigation method according to claim 1, characterized in that: The data sampling frequency of the visual navigation system is 30Hz. Z The pose calculation in a visual navigation system involves four coordinate systems: world coordinate system, camera coordinate system, image coordinate system, and pixel coordinate system. The pose calculated in the visual navigation system is the camera coordinate system relative to the world coordinate system. The coordinates of a landmark point in the real world in the world coordinate system are defined as P. w =[x w ,y w ,z w ] T The coordinates in the camera coordinate system are represented as P. c =[x c ,y c ,z c ] T The transformation relationship between the two positions is as follows: in, This represents the rotation matrix that transforms the world coordinate system to the camera coordinate system. This represents the translation length from the origin of the rotated world coordinate system to the origin of the camera coordinate system.

3. The integrated navigation method according to claim 2, characterized in that: Step (4) transforms the coordinate system of the visual navigation system from the camera coordinate system to the image coordinate system and calculates the transformation matrix, specifically as follows: in: The physical meaning is the camera's extrinsic parameter matrix; The transformation relationship between the coordinates of a pixel in the camera coordinate system and its coordinates in the image coordinate system is as follows: The physical meaning of f is the focal length of the camera, and f is... x =f y =f; 4. The integrated navigation method according to claim 3, characterized in that: Step (5) calculates the transformation matrix of the camera coordinate system-image coordinate system-pixel coordinate system in the visual navigation system, specifically as follows: The physical meaning of M is the camera's intrinsic parameter matrix. The camera's intrinsic and extrinsic parameter matrices can be obtained through calibration; c x and c y These represent the unit lengths of a pixel on the x and y axes, respectively. x and v y Represents the horizontal and vertical coordinates of a pixel in the pixel coordinate system; Determine the coordinates of point P in the global reference frame. w =[x w ,y w ,z w ] T Its coordinates P in the pixel coordinate system uv =[u,v] T Transformation relationship between them:

5. The integrated navigation method according to claim 4, characterized in that: The observation equation of the visual navigation system in step (6) is: Z = h(X,Y) Where: Z represents the observation of the feature point on the projection plane, X represents the calculated camera pose, represented by the Lie algebra ξ, and Y represents the three-dimensional coordinate estimation of the landmark point; h(ξ,p) represents the pixel coordinates obtained after reprojection, therefore the expression for the error function is: e = Zh(ξ,p) Label the actual pixel coordinates of all feature points and the camera state ξ, and let Z be the coordinates of the feature points. ij For the camera in the i-th frame, with state ξ i , for road sign p j The resulting observations are represented by a cost function that minimizes the error function, expressed as: By iterating continuously to minimize the cost function, the optimal estimate is achieved. ξ and p are then calculated, which in turn determines the state of the airborne platform and the three-dimensional coordinates of the landmark points in the world coordinate system.

6. The integrated navigation method according to claim 5, characterized in that: Step (8) calculates the initial transformation matrix between the geographic coordinate system and the world coordinate system, specifically as follows: The latitude, longitude, altitude, pitch, roll, and yaw rates calculated using the inertial coordinate system are relative to the geographic coordinate system. When fusing pose information from the two coordinate systems, the two systems must first be unified and calibrated. Let the geographic coordinate system be the N-system (East-North-Sky coordinate system), and the world coordinate system be the W-system. The transformation matrix between the two coordinate systems is... The transformation matrix between the two coordinate systems is obtained through calibration calculations during aircraft installation. The initial transformation matrix obtained from the calibration calculations is used to project the position information calculated by the two sub-navigation systems onto the same coordinate system.

7. The integrated navigation method according to claim 1, characterized in that: The fiber optic inertial measurement unit includes: an outer casing (1), a gyroscope body (2), a gyroscope instrument head (3), a gyroscope digital board (4), a light source (5), an instrumentation assembly (6), a base (7), an electrical connector (8), a bottom cover (9), an I / F conversion circuit (10), and a DSP circuit (11). The gyroscope digital board (4) is embedded in the gyroscope instrument head (3). Three mutually orthogonal gyroscope instrument heads (3) are installed on the side and top of the gyroscope body (2). The three gyroscope instrument heads (3) share a light source (5). The metering component (6) is located inside the gyroscope body (2) and connected to the gyroscope body (2). The gyroscope body (2) is installed on the base (7). The electrical connector (8) is installed on the side of the base (7). The bottom cover (9) is located below the base (7) as the bottom of the measuring device. The I / F conversion circuit (10) and the DSP circuit (11) are installed between the base (7) and the bottom cover (9) in order from top to bottom. The bottom cover (9) realizes the circuit enclosure. The outer cover (1) and the bottom cover (9) are installed on the base (7). The gyroscope body (2) is installed inside the outer cover (1) through four sets of vibration dampers at the waist. The outer cover (1) realizes the enclosure of the measuring device housing.

Images