CN108592873B - Vehicle-mounted altimeter based on LDV/INS combination and method thereof - Google Patents
Vehicle-mounted altimeter based on LDV/INS combination and method thereof Download PDFInfo
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Abstract
A vehicle-mounted altimeter based on LDV/INS combination comprises an inertial navigation system, a laser Doppler velocimeter, a signal resolving unit and an altitude information display unit; the inertial navigation system and the laser Doppler velocimeter are both arranged on a vehicle; the inertial navigation system measures a real-time pitch angle of the vehicle in the running process and transmits the measured real-time pitch angle information to the signal resolving unit; the laser Doppler velocimeter measures the real-time speed of the vehicle in the running process and transmits the measured real-time speed information to the signal resolving unit; and the signal calculating unit calculates to obtain the vehicle ascending height increment in a set unit time interval according to the speed information and the pitch angle information, accumulates all the height increments from the initial point to the point to be measured, and finally calculates the elevation of the point to be measured. The invention has the characteristics of no influence of meteorological change, small influence of atmospheric refraction, high working efficiency, high measurement precision and the like.
Description
Technical Field
The invention relates to the technical field of laser and precision measurement, in particular to a method for realizing a novel vehicle-mounted height gauge based on an Inertial Navigation System (INS) and a Laser Doppler Velocimeter (LDV), which is mainly used for measuring the land terrain height.
Background
Currently, there are various methods for measuring the elevation of a ground point, such as: leveling, GPS elevation measurement, triangulation elevation measurement, and barometric elevation measurement.
The leveling measurement utilizes a horizontal sight line, measures the height difference between two points on the ground by means of a ruler erected on a ground point, and calculates the elevation of a point to be measured according to the elevation of an initial point. The leveling has the highest precision and is mainly used for establishing an elevation control network of a country or an area. The basic principle of GPS elevation measurement is that geodetic height data of a measuring point is obtained through a GPS technology, normal height data of the measuring point is obtained through leveling, the difference value of the geodetic height and the normal height is elevation abnormity, a quasi-geodetic level surface can be fitted according to the elevation abnormity data, and then the elevation of a point to be measured in a measuring area is obtained. The accuracy of GPS elevation measurement can meet the requirements of three, four and other leveling measurements. The triangulation elevation measurement calculates the elevation difference between the survey station and the reference point based on the vertical angle observed from the survey station to the reference point and the horizontal distance between the two points. The triangulation elevation measurement is mainly used for replacing three, four and other leveling measurements. The barometric pressure elevation measurement utilizes a barometer to measure the barometric pressure difference between two points according to the rule that the atmospheric pressure changes along with the elevation, so as to calculate the elevation difference, and then utilizes the elevation of an initial point to calculate the elevation of a point to be measured.
Leveling instruments are divided into two major categories, optical leveling instruments and digital leveling instruments: the operation of the optical level is relatively complex in the measuring process, the measuring workload is large, the observation efficiency is low, and the actual requirements cannot be met at present due to the production stoppage of the instrument; in recent years, digital levels are more and more popularized due to automatic operation, but the digital levels are influenced by external complex environments, the measurement stability of the digital levels is slightly insufficient, and the phenomenon of rework and retest occurs at a high probability in actual measurement. Leveling measurement has a through-looking requirement, the length of a single-station leveling route is limited, the leveling alignment is influenced by atmospheric refraction when the leveling alignment is horizontal, and the farther the distance between two points is, the larger the measurement error is. The elevation of a ground point is measured by using a GPS, the normal height of a measuring point, the geodetic height of the GPS measuring point and the error of the fitting of the quasi-geodetic level all influence the precision of the GPS elevation measurement; proper measuring points are also selected to ensure uniform distribution and large workload; when the receiver is located in a tunnel, a bridge, a mountain area and a high-rise building, the ephemeris signal received by the GPS is insufficient, so that the positioning accuracy is reduced and even the positioning cannot be carried out. The triangulation of elevations is affected by atmospheric refraction, the horizontal distance and vertical angle of observation become larger, so that the height difference of the final measurement becomes larger, and the error increases as the distance between the survey station and the point of sight increases. When the barometric pressure is measured by the barometric altimeter, the barometric altimeter is greatly influenced by meteorological changes, has the lowest measurement accuracy, and is mainly used for exploration work of hilly lands and mountainous areas.
Disclosure of Invention
Aiming at the defects of the existing elevation measurement method, the invention aims to provide a vehicle-mounted elevation meter based on LDV/INS combination and a method thereof. The invention uses LDV to measure the speed of the vehicle type carrier, and uses INS to measure the attitude angle of the vehicle type carrier, which is different from the four methods in the measuring principle. According to the method, firstly, the INS is used for accurately measuring the real-time attitude angle of the vehicle, meanwhile, the LDV is used for accurately measuring the running speed of the vehicle, further, the speed of the carrier in the vertical direction is calculated, the rising height of the carrier is obtained through integration, and the elevation of the point to be measured can be obtained by combining the elevation of the initial point, so that the measurement of the land terrain height is realized. The invention has the characteristics of no influence of meteorological change, small influence of atmospheric refraction, high working efficiency, high measurement precision and the like.
In order to realize the purpose of the invention, the following technical scheme is adopted for realizing the purpose:
an LDV/INS combination-based vehicle-mounted altimeter comprises an Inertial Navigation System (INS), a Laser Doppler Velocimeter (LDV), a signal resolving unit and an altitude information display unit; the inertial navigation system and the laser Doppler velocimeter are both arranged on a vehicle;
the output end of the inertial navigation system is electrically connected with the signal resolving unit, the inertial navigation system measures the real-time pitch angle of the vehicle in the running process and transmits the measured real-time pitch angle information to the signal resolving unit;
the output end of the laser Doppler velocimeter is electrically connected with the signal resolving unit, and the laser Doppler velocimeter measures the magnitude and direction of real-time speed in the running process of the vehicle and transmits the measured real-time speed information to the signal resolving unit;
the output end of the signal resolving unit is electrically connected with the elevation information display unit; the signal calculating unit calculates height increment of vehicle rising in a set unit time interval according to the speed information and the pitch angle information, accumulates all the height increments from an initial point to a point to be measured, obtains the elevation information of the initial point during initial alignment of the inertial navigation system, finally calculates the elevation of the point to be measured, and finally transmits the calculated elevation information of the point to be measured to the elevation information display unit for result output.
Furthermore, in order to improve the elevation measurement precision of the invention, the invention also comprises a Kalman filter, the output end of the laser Doppler velocimeter is connected with both the Kalman filter and the signal resolving unit, and the laser Doppler velocimeter transmits the measured real-time speed information to the Kalman filter and the signal resolving unit at the same time; the output end of the inertial navigation system is connected with both a Kalman filter and a signal resolving unit, the Kalman filter corrects the real-time pitch angle measured by the inertial navigation system by using the speed information measured by the laser Doppler velocimeter, and the real-time speed information measured by the laser Doppler velocimeter and the corrected pitch angle information are transmitted to the signal resolving unit for resolving the elevation of the point to be measured. The inertial navigation system can measure the angular velocity and the acceleration of the real-time movement of the vehicle, the Kalman filter corrects the angular velocity measured by the inertial navigation system by using the velocity information measured by the laser Doppler velocimeter, the output of the Kalman filter is the correction quantity of the angular velocity, the Kalman filter feeds the correction quantity of the angular velocity back to the inertial measurement unit, the inertial measurement unit corrects the angular velocity according to the feedback correction quantity to obtain the corrected angular velocity, and then integrates the corrected angular velocity to obtain three corresponding corrected attitude angles, namely a course angle, a roll angle and a pitch angle. The elevation measurement of the invention is used for measuring the pitch angle of the vehicle in the motion process measured by the inertial navigation system.
Furthermore, the vehicle-mounted altimeter can be integrally and completely installed on the vehicle, namely an Inertial Navigation System (INS), a Laser Doppler Velocimeter (LDV), a signal resolving unit and an elevation information display unit are all installed on the vehicle. The inertial navigation system and the laser Doppler velocimeter are both fixedly mounted on the outer side face of the vehicle through a fixing frame, and the laser outlet of the laser Doppler velocimeter faces the running face of the vehicle, namely the ground.
The inertial navigation system adopts a laser gyro inertial navigation system which is formed by orthogonally configuring three laser gyros and three accelerometers, the inertial navigation system is directly fixed on a vehicle, namely the three-dimensional angular velocity and the acceleration of the real-time motion of the vehicle can be measured by the inertial navigation system, and the three attitude angles, namely the course angle, the roll angle and the pitch angle, can be obtained by integrating the three-dimensional angular velocity. The invention measures the pitch angle of the vehicle in the moving process through the inertial navigation system.
The laser Doppler velocimeter comprises a laser, a semi-transparent and semi-reflective mirror, a diaphragm, an attenuation sheet, a reflector, an optical filter and a detector, wherein a laser beam with the wavelength of lambda emitted by the laser is divided into two beams of light with equal light intensity by the semi-transparent and semi-reflective mirror;
one beam of light is incident on the reflector after passing through the attenuation sheet, is reflected to the attenuation sheet again by the reflector to be attenuated and then is incident on the semi-transparent semi-reflective mirror, and the beam transmitted from the semi-transparent semi-reflective mirror is incident on a photosensitive surface of the detector after passing through the optical filter and is used as reference light;
the other beam of light is incident to the ground after passing through the diaphragm, and an included angle theta between the incident beam and the ground is a laser emission inclination angle; part of the scattered light on the ground returns along the original light path, namely, part of the scattered light on the ground is incident to the half-transmitting and half-reflecting mirror through the diaphragm, and the light beam reflected by the half-transmitting and half-reflecting mirror is incident to the photosensitive surface of the detector through the optical filter to be used as signal light;
the reference light and the signal light are mixed on the photosensitive surface of the detector, and the frequency difference between the signal light and the reference light is the Doppler frequency fD. Doppler frequency fDProportional to the speed v of movement of the vehicle
Wherein f isDIs the doppler frequency, λ is the laser wavelength, θ is the laser launch tilt angle, and v is the vehicle speed of motion.
By detecting Doppler frequency, the moving speed of the vehicle can be calculated
Since the doppler frequencies obtained when the vehicle moves forward and backward at the same speed are the same, the laser doppler velocimeter cannot distinguish the direction of the vehicle movement. The invention aims to realize the measurement of the elevation of an object to be measured, if a vehicle backs, the height increment in the backing process is a negative value and is subtracted, otherwise, the measurement of the elevation of the object to be measured is inaccurate.
Therefore, the invention further bonds piezoelectric ceramics on the reflector in the laser doppler velocimeter, the piezoelectric ceramics is electrically connected with a piezoelectric ceramics controller, the piezoelectric ceramics controller is used for generating a driving signal to act on the piezoelectric ceramics, and the piezoelectric ceramics pushes and pulls the reflector under the action of the driving signal. The piezoelectric ceramic and piezoelectric ceramic controller are arranged to distinguish the direction of vehicle motion. When the vehicle is stationary, the piezoelectric ceramic pulls the mirror under the action of the driving signal, so that the frequency of the reference light and the frequency of the signal light are different, that is, there is a frequency difference when the vehicle is stationary. Thus, when the vehicle moves forward or backward, the frequency of the output signal of the laser doppler velocimeter moves to the left or right by one doppler frequency based on the control frequency difference. And the Doppler frequency is used for resolving the motion speed of the vehicle, and the motion direction of the vehicle can be judged by judging whether the frequency of the signal moves leftwards or rightwards on the basis of the control frequency difference. The forward direction of the vehicle is defined as a positive direction, and the backward direction of the vehicle is defined as a negative direction. The calculated moving speed of the vehicle is a positive value when the vehicle moves forward, and is a negative value when the vehicle moves backward.
The elevation calculation method of the vehicle-mounted altimeter based on the LDV/INS combination comprises the following steps:
setting an initial point A and a point B to be measured, wherein the elevation of the initial point A is known, and obtaining the elevation difference h between the initial point A and the point B to be measured by adopting a vehicle-mounted elevation meter based on an LDV/INS combinationAB；
If the pitch angle of the vehicle measured by the inertial navigation system, that is, the included angle between the motion direction of the vehicle and the horizontal direction, is α, and the real-time motion speed of the vehicle measured by the laser doppler velocimeter is v, the velocity component of the vehicle in the vertical direction is
v⊥＝vsinα (3)
Wherein v is⊥Is the velocity component of the vehicle in the vertical direction;
bonding of
Wherein f isDIs the Doppler frequency, λIs the laser wavelength, theta is the laser emission inclination angle, v is the vehicle movement speed; the velocity component of the vehicle in the vertical direction can be expressed as
Integrating the speed with the time to obtain the height difference between the corresponding position points of the starting time point and the ending time point in the set unit time interval
Wherein t is a set unit time interval, and Δ h is a height at which the vehicle ascends within the set unit time interval;
this makes it possible to measure the increase in height of the vehicle moving from one point to another within a set time interval: if the vehicle moves on a plane within a unit time interval, the height increment is 0; if the vehicle is moving on an incline within a unit time interval, there is a height increment;
the whole process that the vehicle moves from the initial point A to the point B to be measured is regarded as the motion process consisting of a plurality of continuous unit time intervals, the height increment of each unit time interval is calculated, and finally the height increments in all the unit time intervals in the whole process that the vehicle moves from the initial point A to the point B to be measured are accumulated, so that the height difference h from the initial point to the point B to be measured can be obtainedAB：
hAB＝∑Δh (6)
During measurement, the elevation of the initial point A is known, the initial point A with known elevation can be selected, or the elevation information of the initial point A can be obtained through INS initial alignment, and the elevation of the initial point A is set as HAAnd (6) calculating the elevation of the point B to be measured.
The invention has the following beneficial effects:
compared with the existing ground point elevation measurement method, the method has the advantages that:
the method provides a completely different principle from the prior elevation measurement technology, and is not influenced by the change of the aerial image and has small influence on atmospheric refraction.
(II) a laser gyroscope in the INS is a high-precision angle measuring device; the LDV measures the error of the speed of the moving carrier only 0.1% of the measured value, and has the advantages of high measurement precision, direction identification, good linearity, fast dynamic response, non-contact measurement and the like. The Kalman filter can correct the attitude angle measured by the INS according to the speed information output by the LDV; and the high accuracy of the INS and the LDV is combined, so that the accuracy of the elevation information measurement can be effectively improved.
And thirdly, measuring the elevation of the point to be measured according to the elevation of the initial point, wherein the elevation of the point to be measured can be obtained only by moving the carrier from the initial point to the point to be measured without looking through the initial point and the point to be measured, and the working efficiency is high.
Drawings
FIG. 1 is a schematic diagram of an application of the present invention;
in the figure: 1. a vehicle; 2. a fixed mount; 3. an inertial navigation system; 4. laser Doppler velocimeter
FIG. 2 is a block diagram of the overall principle architecture of the present invention;
FIG. 3 is a control block diagram of an attitude correction network in accordance with the present invention;
FIG. 4 is a diagram of the optical path structure of the laser Doppler velocimeter;
in the figure: 401. a laser; 402. a semi-transparent semi-reflective mirror; 403. a diaphragm; 404. an attenuation sheet; 405. a mirror; 406. an optical filter; 407. a detector; 408. a piezoelectric ceramic controller; 409. piezoelectric ceramics;
FIG. 5 is a schematic diagram of the present invention in which the vehicle travels on a flat surface;
fig. 6 is a schematic diagram of the vehicle of the present invention traveling on a slope.
Detailed Description
In order to make the technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1 and 2, the vehicle-mounted altimeter based on the LDV/INS combination comprises an inertial navigation system 3, a laser doppler velocimeter 4, a signal calculating unit and an altitude information display unit. The vehicle-mounted height gauge can be integrally and completely installed on the vehicle 1, namely, the inertial navigation system 3, the laser Doppler velocimeter 4, the Kalman filter, the signal resolving unit and the height information display unit are all installed on the vehicle 1. The inertial navigation system 3 and the laser Doppler velocimeter 4 are both fixedly mounted on the outer side surface of the vehicle 1 through the fixing frame 2, and the laser outlet of the laser Doppler velocimeter 4 faces the running surface of the vehicle, namely the ground. As shown in fig. 1, the inertial navigation system 3 and the laser doppler velocimeter 4 are both fixedly mounted on the outer side surfaces of the left/right sides of the vehicle 1, such as the outer side surfaces of the doors of the left/right sides, through the fixing frame 2. The fixing frame 2 is not limited in structural form, the fixing frame can be an integral fixing frame, an installation platform of the inertial navigation system and the laser Doppler velocimeter is arranged on the fixing frame, the inertial navigation system and the laser Doppler velocimeter can be fixedly installed on the vehicle, and the fixing frame is integrally detachably installed on the vehicle and can be installed on the vehicle in the forms of screw connection, suction and the like.
Referring to fig. 2, the output end of the laser doppler velocimeter is connected to both the kalman filter and the signal resolving unit, and the laser doppler velocimeter measures the magnitude and direction of the real-time speed of the vehicle during the running process and transmits the measured real-time speed information to both the kalman filter and the signal resolving unit; the output end of the inertial navigation system is connected with the Kalman filter and the signal resolving unit, and the inertial navigation system measures the real-time pitch angle in the running process of the vehicle and transmits the measured real-time pitch angle information to the Kalman filter and the signal resolving unit; the Kalman filter corrects the real-time pitch angle measured by the inertial navigation system by using the speed information measured by the laser Doppler velocimeter, and the real-time speed information measured by the laser Doppler velocimeter and the corrected pitch angle information are transmitted to the signal resolving unit.
The output end of the signal resolving unit is electrically connected with the elevation information display unit; the signal calculating unit calculates height increment of vehicle rising in a set unit time interval according to the speed information and the pitch angle information, accumulates all the height increments from an initial point to a point to be measured, obtains the elevation information of the initial point during initial alignment of the inertial navigation system, finally calculates the elevation of the point to be measured, and finally transmits the calculated elevation information of the point to be measured to the elevation information display unit for result output.
Regarding to a Kalman filter, the pitch angle measured by an inertial navigation system is corrected by using speed information measured by a laser Doppler velocimeter, and the specific correction method is as follows:
the inertial navigation system can measure the angular velocity and the acceleration of the real-time movement of the vehicle, the Kalman filter corrects the angular velocity measured by the inertial navigation system by using the velocity information measured by the laser Doppler velocimeter, the output of the Kalman filter is the correction quantity of the angular velocity, the Kalman filter feeds the correction quantity of the angular velocity back to the inertial measurement unit, the inertial measurement unit corrects the angular velocity according to the feedback correction quantity to obtain the corrected angular velocity, and then integrates the corrected angular velocity to obtain three corresponding corrected attitude angles, namely a course angle, a roll angle and a pitch angle. The elevation measurement of the invention is used for measuring the pitch angle of the vehicle in the motion process measured by the inertial navigation system.
Specifically, in the kalman filter, real-time velocity information measured by a doppler velocimeter is used as measurement, an equivalent accelerometer zero offset and a laser gyro drift are used as a feedback network correction amount, and a control block diagram of an attitude correction network is shown in fig. 3. In the figure VcxAnd VcyThe components of the output speed of the Doppler velocimeter in the east direction and the north direction; hx(s) and Hy(s) is east, north horizontal correction network; y isx、Yy、YzAnd forming an attitude correction network. The attitude correction is performed on the basis of the horizontal correction. And integrating the obtained corrected angular rate to obtain a finally obtained corrected attitude angle, wherein the finally obtained corrected attitude angle comprises a corrected pitch angle.
The inertial navigation system adopts a laser gyro inertial navigation system which is formed by orthogonally configuring three laser gyros and three accelerometers, the inertial navigation system is directly fixed on a vehicle, namely the three-dimensional angular velocity and the acceleration of the real-time motion of the vehicle can be measured by the inertial navigation system, and the three attitude angles, namely the course angle, the roll angle and the pitch angle, can be obtained by integrating the three-dimensional angular velocity. The invention measures the pitch angle of the vehicle in the moving process through the inertial navigation system.
Referring to fig. 4, the laser doppler velocimeter in the present invention includes a laser 401, a half mirror 402, a diaphragm 403, an attenuator 404, a reflector 405, an optical filter 406, and a detector 407, wherein a laser beam with a wavelength λ emitted by the laser 401 is divided into two beams of light with equal intensity by the half mirror 402;
one beam of light enters the reflecting mirror 405 after passing through the attenuation sheet 404, is reflected to the attenuation sheet 404 again through the reflecting mirror 405 to be attenuated and then enters the half-mirror 402, and the beam of light transmitted from the half-mirror 402 enters a photosensitive surface of the detector 407 after passing through the optical filter 406 to be used as reference light;
the other beam of light is incident to the ground after passing through the diaphragm 403, wherein an included angle theta between the beam incident to the ground and the ground is a laser emission inclination angle; a part of the scattered light on the ground returns along the original optical path, that is, a part of the scattered light on the ground is incident to the half mirror 402 through the diaphragm 403, and a light beam reflected by the half mirror 402 is incident to the photosensitive surface of the detector 406 through the optical filter as signal light;
the reference light and the signal light are mixed on the photosensitive surface of the detector, and the frequency difference between the signal light and the reference light is the Doppler frequency fD. Doppler frequency fDProportional to the speed v of movement of the vehicle
Wherein f isDIs the doppler frequency, λ is the laser wavelength, θ is the laser launch tilt angle, and v is the vehicle speed of motion.
By detecting Doppler frequency, the moving speed of the vehicle can be calculated
Since the doppler frequencies obtained when the vehicle moves forward and backward at the same speed are the same, the laser doppler velocimeter cannot distinguish the direction of the vehicle movement. The invention aims to realize the measurement of the elevation of an object to be measured, if a vehicle backs, the height increment in the backing process is a negative value and is subtracted, otherwise, the measurement of the elevation of the object to be measured is inaccurate.
Therefore, in the invention, the piezoelectric ceramic 409 is bonded on the reflecting mirror 405 in the laser doppler velocimeter, the piezoelectric ceramic 409 is electrically connected with the piezoelectric ceramic controller 408, the piezoelectric ceramic controller 408 is used for generating a driving signal to act on the piezoelectric ceramic 409, and the piezoelectric ceramic 409 pushes and pulls the reflecting mirror 405 under the action of the driving signal. Piezo 409 and piezo controller 408 are arranged to distinguish the direction of vehicle motion. When the vehicle is stationary, the piezoelectric ceramic pulls the mirror under the action of the driving signal, so that the frequency of the reference light and the frequency of the signal light are different, that is, there is a frequency difference when the vehicle is stationary. Thus, when the vehicle moves forward or backward, the frequency of the output signal of the laser doppler velocimeter moves to the left or right by one doppler frequency based on the control frequency difference. And the Doppler frequency is used for resolving the motion speed of the vehicle, and the motion direction of the vehicle can be judged by judging whether the frequency of the signal moves leftwards or rightwards on the basis of the control frequency difference. The forward direction of the vehicle is defined as a positive direction, and the backward direction of the vehicle is defined as a negative direction. The calculated moving speed of the vehicle is a positive value when the vehicle moves forward, and is a negative value when the vehicle moves backward.
The elevation calculation method of the vehicle-mounted altimeter based on the LDV/INS combination comprises the following steps:
if the pitch angle of the vehicle measured by the inertial navigation system, that is, the included angle between the motion direction of the vehicle and the horizontal direction, is α, and the real-time motion speed of the vehicle measured by the laser doppler velocimeter is v, the velocity component of the vehicle in the vertical direction is
v⊥＝vsinα (3)
Wherein v is⊥Is the velocity component of the vehicle in the vertical direction.
Bonding of
Wherein f isDIs the doppler frequency, λ is the laser wavelength, θ is the laser launch tilt angle, and v is the vehicle speed of motion. The velocity component of the vehicle in the vertical direction can be expressed as
Integrating the speed with the time to obtain the height difference between the corresponding position points of the starting time point and the ending time point in the set unit time interval
Where t is the set unit time interval (typically 10ms) and Δ h is the height at which the vehicle ascends within the set unit time interval.
This makes it possible to measure the increase in height of the vehicle moving from one point to another within a set time interval: if the vehicle is moving on a flat surface for this period of time (as shown in FIG. 5), the height increment is 0; if the vehicle is moving on an incline during this time (as shown in FIG. 6), there is an increase in height. Setting an initial point A and a point B to be measured, regarding the whole process of the vehicle moving from the initial point A to the point B to be measured as a moving process consisting of a plurality of continuous unit time intervals, calculating the height increment of each unit time interval, and finally accumulating the height increments in all the unit time intervals in the whole process of the vehicle moving from the initial point A to the point B to be measured, thus obtaining the height difference h from the initial point to the point B to be measuredAB：
hAB＝∑Δh (6)
During measurement, the elevation of the initial point A is known, the initial point A with known elevation can be selected, or the elevation information of the initial point A can be obtained through INS initial alignment, and the elevation of the initial point A is set as HAAnd (6) calculating the elevation of the point B to be measured.
In summary, although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (8)
1. An on-vehicle altimeter based on LDV/INS combination which characterized in that: the vehicle-mounted altimeter comprises an inertial navigation system, a laser Doppler velocimeter, a signal resolving unit and an elevation information display unit; the inertial navigation system and the laser Doppler velocimeter are both arranged on a vehicle,
the output end of the inertial navigation system is electrically connected with the signal resolving unit, the inertial navigation system measures the real-time pitch angle of the vehicle in the running process and transmits the measured real-time pitch angle information to the signal resolving unit;
the output end of the laser Doppler velocimeter is electrically connected with the signal resolving unit, and the laser Doppler velocimeter measures the magnitude and direction of real-time speed in the running process of the vehicle and transmits the measured real-time speed information to the signal resolving unit; the laser Doppler velocimeter comprises a laser, a semi-transparent semi-reflective mirror, a diaphragm, an attenuation sheet, a reflector, an optical filter and a detector, wherein piezoelectric ceramics are bonded on the reflector, the piezoelectric ceramics are electrically connected with a piezoelectric ceramic controller, the piezoelectric ceramic controller is used for generating a driving signal to act on the piezoelectric ceramics, the piezoelectric ceramics push and pull the reflector under the action of the driving signal, and the piezoelectric ceramics and the piezoelectric ceramic controller are arranged for distinguishing the motion direction of a vehicle; the output end of the signal resolving unit is electrically connected with the elevation information display unit; the signal calculating unit calculates height increment of vehicle rising in a set unit time interval according to the speed information and the pitch angle information, accumulates all the height increments from an initial point to a point to be measured, obtains the elevation information of the initial point during initial alignment of the inertial navigation system, finally calculates the elevation of the point to be measured, and finally transmits the calculated elevation information of the point to be measured to the elevation information display unit for result output.
2. The combination LDV/INS-based on vehicle altimeter of claim 1, wherein: the inertial navigation system and the laser Doppler velocimeter are both fixedly mounted on the outer side face of the vehicle through a fixing frame, and the laser outlet of the laser Doppler velocimeter faces the running face of the vehicle, namely the ground.
3. The combination LDV/INS-based on vehicle altimeter of claim 1, wherein: the output end of the laser Doppler velocimeter is connected with both the Kalman filter and the signal resolving unit, and the laser Doppler velocimeter transmits the measured real-time speed information to the Kalman filter and the signal resolving unit at the same time; the output end of the inertial navigation system is connected with both a Kalman filter and a signal resolving unit, the Kalman filter corrects a pitch angle measured by the inertial navigation system by using speed information measured by a laser Doppler velocimeter, and real-time speed information measured by the laser Doppler velocimeter and the corrected pitch angle information are transmitted to the signal resolving unit for resolving the elevation of a point to be measured.
4. The combination LDV/INS-based on vehicle altimeter of claim 1, wherein: the inertial navigation system adopts a laser gyro inertial navigation system which is formed by orthogonal configuration of three laser gyros and three accelerometers, the inertial navigation system is directly fixed on a vehicle, namely, the three-dimensional angular velocity and the acceleration of the real-time motion of the vehicle can be measured by the inertial navigation system, and the three attitude angles, namely a course angle, a roll angle and a pitch angle, are obtained by integrating the three-dimensional angular velocity.
5. The combination LDV/INS-based on vehicle altimeter of claim 1, wherein: a laser beam with the wavelength of lambda emitted by a laser in the laser Doppler velocimeter is divided into two beams of light with equal light intensity by a semi-transparent semi-reflecting mirror;
one beam of light is incident on the reflector after passing through the attenuation sheet, is reflected to the attenuation sheet again by the reflector to be attenuated and then is incident on the semi-transparent semi-reflective mirror, and the beam transmitted from the semi-transparent semi-reflective mirror is incident on a photosensitive surface of the detector after passing through the optical filter and is used as reference light;
the other beam of light is incident to the ground after passing through the diaphragm, and an included angle theta between the incident beam and the ground is a laser emission inclination angle; part of the scattered light on the ground returns along the original light path, namely, part of the scattered light on the ground is incident to the half-transmitting and half-reflecting mirror through the diaphragm, and the light beam reflected by the half-transmitting and half-reflecting mirror is incident to the photosensitive surface of the detector through the optical filter to be used as signal light;
the reference light and the signal light are mixed on the photosensitive surface of the detector, and the frequency difference between the signal light and the reference light is the Doppler frequency fDBy detecting the Doppler frequency fDThe moving speed of the vehicle can be calculated.
6. The LDV/INS combination-based on-board height gauge of claim 5, wherein: doppler frequency fDProportional to the speed v of movement of the vehicle
Wherein f isDIs the doppler frequency, λ is the laser wavelength, θ is the laser launch tilt angle, v is the vehicle speed of movement;
therefore, there are:
7. the combination LDV/INS-based on vehicle altimeter of claim 1, wherein: the method for distinguishing the moving direction of the vehicle is as follows:
when the vehicle is static, the piezoelectric ceramic pushes and pulls the reflector under the action of the driving signal, so that the frequency of the reference light and the frequency of the signal light are different when the vehicle is static, namely, the frequency difference exists, and the frequency difference is controlled by the driving signal and is called as control frequency difference;
when the vehicle moves forwards or backwards, the frequency of the output signal of the laser Doppler velocimeter moves one Doppler frequency leftwards or rightwards on the basis of the control frequency difference; the Doppler frequency is used for resolving the motion speed of the vehicle, and the motion direction of the vehicle can be judged by judging whether the frequency of the signal moves leftwards or rightwards on the basis of controlling the frequency difference;
defining the forward direction of the vehicle as a positive direction and the backward direction of the vehicle as a negative direction; the calculated moving speed of the vehicle is a positive value when the vehicle moves forward, and is a negative value when the vehicle moves backward.
8. The method for calculating the elevation of the LDV/INS combination-based vehicle-mounted altimeter as recited in any one of claims 1 to 7, wherein an initial point A and a point B to be measured are provided, wherein the elevation of the initial point A is known, and the LDV/INS combination-based vehicle-mounted altimeter is used to obtain the elevation difference h between the initial point A and the point B to be measuredAB；
If the pitch angle of the vehicle measured by the inertial navigation system, that is, the included angle between the motion direction of the vehicle and the horizontal direction, is α, and the real-time motion speed of the vehicle measured by the laser doppler velocimeter is v, the velocity component of the vehicle in the vertical direction is:
v⊥＝vsinα (3)
wherein v is⊥Is the velocity component of the vehicle in the vertical direction;
bonding of
Wherein f isDIs the doppler frequency, λ is the laser wavelength, θ is the laser launch tilt angle, v is the vehicle speed of movement;the velocity component of the vehicle in the vertical direction is then expressed as:
integrating the speed with the time to obtain the height difference between the corresponding position points of the starting time point and the ending time point in the set unit time interval:
wherein t is a set unit time interval, and Δ h is a height at which the vehicle ascends within the set unit time interval;
this measures the incremental height of the vehicle rising from one point to another within a set time interval: if the vehicle moves on a plane within a unit time interval, the height increment is 0; if the vehicle is moving on an incline within a unit time interval, there is a height increment;
the whole process that the vehicle moves from the initial point A to the point B to be measured is regarded as the motion process consisting of a plurality of continuous unit time intervals, the height increment of each unit time interval is calculated, and finally the height increments in all the unit time intervals in the whole process that the vehicle moves from the initial point A to the point B to be measured are accumulated, so that the height difference h from the initial point to the point B to be measured is obtainedAB：
hAB＝∑Δh (6)。
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