CN112556724A - Initial coarse alignment method for low-cost navigation system of micro aircraft in dynamic environment - Google Patents
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Abstract
The initial coarse alignment method of the low-cost navigation system of the micro aircraft in the dynamic environment is characterized in that the micro aircraft is provided with sensor equipment such as a three-axis inertial device, a magnetometer and a satellite navigation system GNSS, the initial alignment is carried out by adopting the combined information of the inertial device, the magnetometer and the satellite navigation system GNSS, the three-axis inertial device and the magnetometer on the aircraft respectively measure the acceleration and the magnetic field intensity information under a coordinate system of the aircraft body, the GNSS of the satellite navigation system measures the current longitude and latitude of a carrier and the speed information relative to a geographic navigation coordinate system, a direction cosine matrix is converted from the coordinate system of the aircraft body to the initial attitude of the geographic navigation coordinate system through calculation, and then the initial attitude angle of the aircraft relative to the geographic navigation coordinate system is determined to complete the initial.
Description
Technical Field
The invention belongs to the technical field of aircraft navigation positioning, and particularly relates to an initial coarse alignment method of a low-cost navigation system of a miniature aircraft in a dynamic environment.
Background
In recent years, with the rapid development of unmanned aerial vehicles and micro aircrafts in military and civil industries, the expansion of the application field of the unmanned aerial vehicle industry becomes continuous power for promoting the development of the unmanned aerial vehicle industry. The unmanned micro aircraft used after ground launching or aerial release and then electrified is different from the traditional ground take-off and landing aircraft, has low requirements on fields and use environments, can be applied to the military fields of remote monitoring, investigation and striking and the like of the sea and enemy territory, and the civil fields of aerial photography, disaster rescue, mapping and the like during sea and forest fires. Positioning accuracy of a navigation system using a micro aircraft during air electrification becomes the first guarantee for successfully executing a flight task, and when a Micro Electro Mechanical System (MEMS) navigation system widely adopted by the micro aircraft is initially aligned, the initial attitude angles of an engine body relative to a geographic navigation coordinate system, namely an initial pitch angle and a roll angle, need to be determined, and the determination of the initial attitude angle becomes the key of subsequent positioning accuracy, so that the initial alignment method of the low-cost navigation system of the micro aircraft under the air dynamic environment has great application prospect.
The MEMS navigation positioning sensor widely adopted by the micro aircraft has the advantages of low cost, small size and the like, but also has the defects of low precision and the like, can not identify the rotation angular velocity of the earth, and is difficult to solve the problem of self-alignment. Meanwhile, aiming at the micro aircraft used after being launched on the ground or being charged after being thrown in the air, because the micro aircraft is in the dynamic environment in the air at the initial moment and is simultaneously influenced by aerodynamic lift, aerodynamic resistance, aircraft self power, gravity and the like, the acceleration caused by acting force except the gravity exists, and the method for determining the initial pitch angle and the roll angle only by the accelerometer measurement value in the static arrangement state on the ground adopted by the traditional micro aircraft at the initial alignment cannot be applied. Therefore, in order to obtain the initial coarse alignment posture of the micro-aircraft low-cost MEMS navigation system in the air dynamic environment, the alignment must be assisted by external information.
The navigation system of the traditional unmanned aerial vehicle widely adopts a magnetometer, a satellite navigation system GNSS and the like to carry out external information to assist a low-cost MEMS inertial device to carry out combined navigation, so that the task requirement is met only by modifying a software algorithm under the condition of utilizing the existing hardware and not increasing a measuring sensor, the cost can be greatly reduced, and the practicability and the economic benefit are improved. However, for the alignment problem in the air dynamic environment, since the method of providing the initial absolute reference information by using the gravity acceleration in the ground static state cannot be adopted, another kind of absolute reference information needs to be found. Meanwhile, the updating speed of the GNSS of the satellite navigation system is low, the sampling rate of the MEMS inertial navigation is high, and the difference of the sampling rates can cause information delay to generate errors, so that how to reasonably use the magnetometer, the GNSS of the satellite navigation system and the like to carry out auxiliary alignment of external information needs to be further solved.
Disclosure of Invention
The invention aims to solve the task application problems of low precision of a low-cost navigation system and alignment of an air dynamic environment, and provides an initial rough alignment method of a low-cost navigation system of a micro aircraft under the dynamic environment, wherein the micro aircraft is provided with sensor equipment such as a triaxial inertia device, a magnetometer and a satellite navigation system GNSS, the initial alignment is carried out by adopting the combined information of the inertia device, the magnetometer and the satellite navigation system GNSS, the airborne triaxial inertia device and the magnetometer respectively measure the acceleration and magnetic field intensity information under a body coordinate system, the satellite navigation system GNSS measures the current longitude and latitude of a carrier and the speed information relative to a geographical navigation coordinate system, converting the initial attitude of the coordinate system of the body to the coordinate system of the geographical navigation into a direction cosine matrix through calculation, and then determining an initial attitude angle of the aircraft relative to a geographical navigation coordinate system to complete initial coarse alignment.
Further, the method comprises the following steps:
s1, the magnetic field intensity vector of the real-time current position of the micro aircraft is obtained by inquiring an earth magnetic field distribution table according to the GNSS positioning data or directly calculated according to an earth magnetic field model,
the vector relationship between the measurement data of the airborne measuring magnetometer and the magnetic field intensity under the local geographic coordinate system is as follows:
in the formula, mnIs the magnetic field intensity vector under the local geographical navigation coordinate system,the vector of the magnetic field intensity under the coordinate system of the machine body is measured by the magnetometer,converting a direction cosine matrix from a body coordinate system to a geographical navigation coordinate system;
the origin of the geographic navigation coordinate system is located at the center of mass of the aircraft, and the three-dimensional coordinate axes respectively point to the fixed directions of the north, the east and the ground; the origin of the body coordinate system is positioned at the mass center of the aircraft, and the three-dimensional coordinate axes point to the reference directions of the carrier, namely the front, the right and the lower sides;
s2, for the accelerometer measuring data, since the accelerometer measures the specific force, the specific force is not the motion acceleration of the carrier, but the difference between the absolute acceleration of the carrier relative to the inertia space and the gravity acceleration of the earth, wherein the inertia space is the difference between the motion and the rest of the object described by newton' S law relative to a special reference frame, there is the following relationship:
in the formula (f)nFor local geography guidanceA specific force vector under the navigation coordinate system;a specific force vector of a coordinate system of the body measured for the accelerometer;
aiming at the alignment problem in the air dynamic environment, because the method of providing initial absolute reference information by using the gravity acceleration under the static state of the ground cannot be used, another absolute reference information needs to be searched, and the specific force vector f under the local geographic coordinate systemnAccording to a gravity field data model and a micro aircraft carrier current motion velocity vector vnDetermining, based on the Coriolis acceleration theorem, a specific force f on a geographical coordinate systemnWith acceleration in a geographical coordinate systemAnd acceleration of gravity gnThe following relationship is satisfied:
in the formula (I), the compound is shown in the specification,the rotation angular speed of the geographic coordinate system;projecting the rotational angular velocity of the earth on a geographic coordinate system; for a carrier with a small moving speed, and the measurement accuracy limit of a low-cost MEMS navigation system,negligible, so the following formula:
s3 speed information, namely the current motion speed vector of the micro-aircraft carrierQuantity vnThe measurement is obtained through a GNSS system;
s4 magnetic field intensity vector under assumed measurement vector machine body coordinate systemSpecific force vector of body coordinate systemThe vectors are not parallel, and if the two vectors are parallel, the measurement can be performed when the two vectors are not parallel, such as the next measurement time, and the like, by judging that the two vectors are parallel, so that a third vector equation is obtained by the vector cross product of the two vectors as follows:
wherein the content of the first and second substances,is a posture conversion direction cosine matrix of the vector coordinate conversion from the body coordinate system to the geographic coordinate system;
s5, calculating a vector m in three known calculation vectorsn、fnAnd mn×fnAnd three measurement vectorsAndin combination with the above formula, the following formula is given:
the orientation transformation direction cosine matrix from the computer body coordinate system to the geographic coordinate system is as follows:
s6, rolling angle phi, pitching angle theta and yaw angle psi of the aircraft and attitude transformation direction cosine matrix from the body coordinate system to the geographic coordinate systemThe relationship of (a) to (b) is as follows:
converting a direction cosine matrix according to attitudeThe initial attitude angle (namely the roll angle phi) during the coarse alignment is calculated through an inverse trigonometric function0Angle of pitch theta0And yaw angle psi0The following were used:
in conclusion, the invention obtains the initial attitude angle in the air dynamic environment.
Further, step S1 is preceded by:
and S0, the micro aircraft is powered on after being launched from the ground or thrown in the air, and when the standby navigation sensor equipment is started to work normally after a period of time, the airborne inertial device, the magnetometer and the satellite navigation system GNSS work normally, and the micro aircraft navigation system starts to run.
Preferably, in step S4, since the speed information is obtained by measuring through the GNSS system, but the sampling rate of the MEMS inertial device is high, the sampling rate of the satellite navigation system is low, and time correction is required to be performed on the speed data to solve the problem of sampling rate mismatch, and by correcting the data compared at the sampling time, the error caused by the inconsistency of the sampling time between the GNSS system and the inertial device can be reduced. The method for time correction of the speed information measured by the GNSS system comprises the following steps:
if the output acceleration signal of the inertia device is at tk-1And tkObtained while the neighboring GNSS measurement speed information isAndthe velocity information of the GNSS measurement obtained above isAndmethod for obtaining micro aircraft at time t by using linear interpolationk-1And tkUpper velocity estimation information vn(tk-1) And vn(tk) The details are as follows
According to the sampling data time interval of the MEMS inertial navigation sensor, namely the accelerometer, as delta t, the speed derivative on the geographic coordinate system, namely the acceleration informationCan be obtained by correcting the corrected speed information vn(tk-1) And vn(tk) Time difference obtaining is carried out, namely:
compared with the prior art, the technical scheme of the invention can obtain the following beneficial effects:
1. the initial alignment method designed by the invention obtains absolute reference information for determining the attitude angle of the initial carrier, namely the initial pitch angle and the roll angle, namely the absolute reference magnetic field intensity information of the current position is obtained by looking up a table of earth magnetic field distribution according to the current longitude and latitude, and the absolute reference acceleration information relative to the ground is obtained according to the differential value of the speed relative to the ground navigation coordinate system, so that the accuracy of the system is improved;
2. the initial alignment method designed by the invention solves the problem of mismatching of the sampling rates of the inertial device and the satellite navigation, reduces the alignment error, meets the continuous requirement of the sampling data by time correction of the acquired data, and improves the reliability of the system. .
Drawings
FIG. 1 is a diagram of the relationship between the combined information of an inertial device, a magnetometer and a GNSS of a satellite navigation system in accordance with the present invention;
FIG. 2 is a graph of the inertial device and time correction of satellite navigation sample data in accordance with the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
The initial coarse alignment method of the low-cost navigation system of the miniature aircraft in the dynamic environment is characterized in that the miniature aircraft is provided with sensor equipment such as a triaxial inertia device, a magnetometer and a satellite navigation system GNSS, the initial alignment is carried out by adopting the combined information of the inertia device, the magnetometer and the satellite navigation system GNSS, the airborne triaxial inertia device and the magnetometer respectively measure the acceleration and magnetic field intensity information under a body coordinate system, the satellite navigation system GNSS measures the current longitude and latitude of a carrier and the speed information relative to a geographical navigation coordinate system, the initial attitude transformation direction cosine matrix from the body coordinate system to the geographical navigation coordinate system is obtained through calculation, and then the initial attitude angle of the aircraft relative to the geographical navigation coordinate system is determined to complete the initial coarse alignment.
The method comprises the following steps:
s0, the micro aircraft is powered on after being launched from the ground or thrown in the air, when a period of time passes and the standby navigation sensor equipment is started to work normally, the airborne inertial device, the magnetometer and the satellite navigation system GNSS work normally, and the micro aircraft navigation system starts to run;
s1, because the earth magnetic field data model is quite perfect, the magnetic field intensity vector of the real-time current position of the micro aircraft is obtained by inquiring the earth magnetic field distribution table according to the GNSS positioning data or directly calculated according to the earth magnetic field model,
the vector relationship between the measurement data of the airborne measuring magnetometer and the magnetic field intensity under the local geographic coordinate system is as follows:
in the formula, mnIs the magnetic field intensity vector under the local geographical navigation coordinate system,the vector of the magnetic field intensity under the coordinate system of the machine body is measured by the magnetometer,converting a direction cosine matrix from a body coordinate system to a geographical navigation coordinate system;
the origin of the geographic navigation coordinate system is located at the center of mass of the aircraft, and the three-dimensional coordinate axes respectively point to the fixed directions of the north, the east and the ground; the origin of the body coordinate system is positioned at the mass center of the aircraft, and the three-dimensional coordinate axes point to the reference directions of the carrier, namely the front, the right and the lower sides;
s2, for the accelerometer measuring data, since the accelerometer measures the specific force, the specific force is not the motion acceleration of the carrier, but the difference between the absolute acceleration of the carrier relative to the inertia space and the gravity acceleration of the earth, wherein the inertia space is the difference between the motion and the rest of the object described by newton' S law relative to a special reference frame, there is the following relationship:
in the formula (f)nA specific force vector under a local geographical navigation coordinate system;a specific force vector of a coordinate system of the body measured for the accelerometer;
aiming at the alignment problem in the air dynamic environment, because the method of providing initial absolute reference information by using the gravity acceleration under the static state of the ground cannot be used, another absolute reference information needs to be searched, and the specific force vector f under the local geographic coordinate systemnAccording to a gravity field data model and a micro aircraft carrier current motion velocity vector vnDetermining, based on the Coriolis acceleration theorem, a specific force f on a geographical coordinate systemnWith acceleration in a geographical coordinate systemAnd acceleration of gravity gnThe following relationship is satisfied:
in the formula (I), the compound is shown in the specification,the rotation angular speed of the geographic coordinate system;projecting the rotational angular velocity of the earth on a geographic coordinate system; measurement for carrier with small motion speed and low-cost MEMS navigation systemThe limitation of the precision is that the precision is limited,negligible, so the following formula:
s3, velocity information, namely the current motion velocity vector v of the micro aircraft carriernThe measurement is obtained through a GNSS system;
s4 magnetic field intensity vector under assumed measurement vector machine body coordinate systemSpecific force vector of body coordinate systemThe vectors are not parallel, and if the two vectors are parallel, the measurement can be performed when the two vectors are not parallel, such as the next measurement time, and the like, by judging that the two vectors are parallel, so that a third vector equation is obtained by the vector cross product of the two vectors as follows:
wherein the content of the first and second substances,is a posture conversion direction cosine matrix of the vector coordinate conversion from the body coordinate system to the geographic coordinate system;
s5, calculating a vector m in three known calculation vectorsn、fnAnd mn×fnAnd three measurement vectorsAndin combination with the above formula, the following formula is given:
the orientation transformation direction cosine matrix from the computer body coordinate system to the geographic coordinate system is as follows:
s6, rolling angle phi, pitching angle theta and yaw angle psi of the aircraft and attitude transformation direction cosine matrix from the body coordinate system to the geographic coordinate systemThe relationship of (a) to (b) is as follows:
converting a direction cosine matrix according to attitudeThe initial attitude angle (namely the roll angle phi) during the coarse alignment is calculated through an inverse trigonometric function0Angle of pitch theta0And yaw angle psi0The following were used:
in conclusion, the invention obtains the initial attitude angle in the air dynamic environment.
The method obtains the initial attitude angle in the air dynamic environment, can provide calculation initial information for a subsequent navigation system, and meets the requirement of initial coarse alignment of a low-cost navigation system of a micro aircraft in the air dynamic environment.
Example 2
The present embodiment is different from embodiment 1 in that:
in the step S4, since the speed information is obtained by GNSS system measurement, but the sampling rate of the MEMS inertial device is fast, and the sampling rate of the GNSS navigation system is slow, time correction is required for the speed data to solve the problem of sampling rate mismatch, and by correcting the comparison data at the sampling time, the error caused by inconsistency of the sampling times of the GNSS system and the inertial device can be reduced. The method for time correction of the speed information measured by the GNSS system comprises the following steps:
if the output acceleration signal of the inertia device is at tk-1And tkObtained while the neighboring GNSS measurement speed information isAndthe velocity information of the GNSS measurement obtained above isAndmethod for obtaining micro aircraft at time t by using linear interpolationk-1And tkUpper velocity estimation information vn(tk-1) And vn(tk) The method comprises the following steps:
time interval of sampled data according to MEMS inertial navigation sensor, namely accelerometer, is delta t, velocity derivative on geographic coordinate systemCan be obtained by correcting the corrected speed information vn(tk-1) And vn(tk) Time difference obtaining is carried out, namely:
the rest is the same as in example 1.
Claims (4)
1. The initial coarse alignment method of the low-cost navigation system of the micro aircraft in the dynamic environment is characterized in that the micro aircraft is provided with sensor equipment such as a three-axis inertial device, a magnetometer and a satellite navigation system GNSS, the initial alignment is carried out by adopting the combined information of the inertial device, the magnetometer and the satellite navigation system GNSS, the three-axis inertial device and the magnetometer on the aircraft respectively measure the acceleration and the magnetic field intensity information under a coordinate system of the aircraft body, the GNSS of the satellite navigation system measures the current longitude and latitude of a carrier and the speed information relative to a geographic navigation coordinate system, a direction cosine matrix is converted from the coordinate system of the aircraft body to the initial attitude of the geographic navigation coordinate system through calculation, and then the initial attitude angle of the aircraft relative to the geographic navigation coordinate system is determined to complete the initial.
2. The method for initial coarse alignment of a low-cost navigation system of a micro-aircraft in a dynamic environment according to claim 1, comprising the steps of:
s1, the magnetic field intensity vector of the real-time current position of the micro aircraft is obtained by inquiring an earth magnetic field distribution table according to the GNSS positioning data or directly calculated according to an earth magnetic field model,
the vector relationship between the measurement data of the airborne measuring magnetometer and the magnetic field intensity under the local geographic coordinate system is as follows:
in the formula, mnIs the magnetic field intensity vector under the local geographical navigation coordinate system,the vector of the magnetic field intensity under the coordinate system of the machine body is measured by the magnetometer,converting a direction cosine matrix from a body coordinate system to a geographical navigation coordinate system;
the origin of the geographic navigation coordinate system is located at the center of mass of the aircraft, and the three-dimensional coordinate axes respectively point to the fixed directions of the north, the east and the ground; the origin of the body coordinate system is positioned at the mass center of the aircraft, and the three-dimensional coordinate axes point to the reference directions of the carrier, namely the front, the right and the lower sides;
s2, for the accelerometer measuring data, since the accelerometer measures the specific force, the specific force is not the motion acceleration of the carrier, but the difference between the absolute acceleration of the carrier relative to the inertia space and the gravity acceleration of the earth, wherein the inertia space is the difference between the motion and the rest of the object described by newton' S law relative to a special reference frame, there is the following relationship:
in the formula (f)nA specific force vector under a local geographical navigation coordinate system;a specific force vector of a coordinate system of the body measured for the accelerometer;
aiming at the alignment problem in the air dynamic environment, because the method of providing initial absolute reference information by using the gravity acceleration under the static state of the ground cannot be used, another absolute reference information needs to be searched, and the specific force vector f under the local geographic coordinate systemnAccording to a gravity field data model and a micro aircraft carrier current motion velocity vector vnDetermination based on Coriolis accelerationTheorem, determining specific force f on geographical coordinate systemnWith acceleration in a geographical coordinate systemAnd acceleration of gravity gnThe following relationship is satisfied:
in the formula (I), the compound is shown in the specification,the rotation angular speed of the geographic coordinate system;projecting the rotational angular velocity of the earth on a geographic coordinate system; for a carrier with a small moving speed, and the measurement accuracy limit of a low-cost MEMS navigation system,negligible, so the following formula:
s3, velocity information, namely the current motion velocity vector v of the micro aircraft carriernThe measurement is obtained through a GNSS system;
s4 magnetic field intensity vector under assumed measurement vector machine body coordinate systemSpecific force vector of body coordinate systemNon-parallel, if the two are judged to be in fact in the air because the carrier continuously moves in the airWhen the vectors are parallel, the measurement can be carried out again when the two vectors are not parallel, such as the next measurement time, and therefore, a third vector equation is obtained through the vector cross product of the two vectors as follows:
wherein the content of the first and second substances,is a posture conversion direction cosine matrix of the vector coordinate conversion from the body coordinate system to the geographic coordinate system;
s5, calculating a vector m in three known calculation vectorsn、fnAnd mn×fnAnd three measurement vectors Andin combination with the above formula, the following formula is given:
the orientation transformation direction cosine matrix from the computer body coordinate system to the geographic coordinate system is as follows:
s6, rolling angle phi, pitching angle theta and yaw angle psi of the aircraft and attitude transformation direction cosine matrix from the body coordinate system to the geographic coordinate systemThe relationship of (a) to (b) is as follows:
converting a direction cosine matrix according to attitudeThe initial attitude angle (namely the roll angle phi) during the coarse alignment is calculated through an inverse trigonometric function0Angle of pitch theta0And yaw angle psi0The following were used:
in conclusion, the invention obtains the initial attitude angle in the air dynamic environment.
3. The method for initial coarse alignment of a low-cost navigation system of a micro-aircraft in a dynamic environment according to claim 2, wherein said step S1 is preceded by the step of:
and S0, the micro aircraft is powered on after being launched from the ground or thrown in the air, and after a period of time and the standby navigation sensor equipment is started to work normally, the airborne inertial device, the magnetometer and the satellite navigation system GNSS work normally, and the micro aircraft navigation system starts to run.
4. The initial coarse alignment method for the low-cost navigation system of a micro-aircraft under the dynamic environment according to any one of claims 1 to 3, wherein in the step S4, the velocity information measured by the GNSS system is time-corrected by:
if the output acceleration signal of the inertia device is at tk-1And tkObtained while the neighboring GNSS measurement speed information isAndthe velocity information of the GNSS measurement obtained above isAndmethod for obtaining micro aircraft at time t by using linear interpolationk-1And tkUpper velocity estimation information vn(tk-1) And vn(tk) The method comprises the following steps:
according to the sampling data time interval of the MEMS inertial navigation sensor, namely the accelerometer, as delta t, the speed derivative on the geographic coordinate system, namely the acceleration informationCan be obtained by correcting the corrected speed information vn(tk-1) And vn(tk) Time difference obtaining is carried out, namely:
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CN113218423A (en) * | 2021-05-25 | 2021-08-06 | 上海机电工程研究所 | Aerial coarse alignment method without reference attitude information during transmitting |
CN113740890A (en) * | 2021-08-31 | 2021-12-03 | 普宙科技(深圳)有限公司 | Course angle correction method, system, computer equipment and storage medium |
CN114018255A (en) * | 2021-11-03 | 2022-02-08 | 湖南国天电子科技有限公司 | Intelligent integrated navigation method, system, equipment and medium for underwater glider |
CN117968681A (en) * | 2024-03-29 | 2024-05-03 | 北京大学 | Positioning method, positioning device, medium-crossing aircraft and storage medium |
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