Disclosure of Invention
The purpose of the invention is: aiming at the problems of unknown underwater sound velocity, large initial position error of an underwater vehicle or large position error at a certain moment and the like in underwater single beacon positioning, the underwater vehicle single beacon positioning method with global convergence is provided based on a state augmentation method.
The technical scheme of the invention is as follows: an underwater vehicle single beacon positioning method with global convergence is disclosed, wherein the underwater vehicle is provided with a hydrophone, a Doppler velocimeter, a depth meter, an attitude heading reference system and a GPS; the underwater sound beacon broadcasts the underwater sound signal periodically; the method comprises the following steps:
A. establishing an underwater local inertia coordinate system by taking any point in a positioning area as an origin and setting the east, north and sky directions as x, y and z axes respectively;
B. acquiring an initial position of the underwater vehicle in an underwater local inertial coordinate system through a carried GPS;
C. establishing a kinematics model and an observation model of an underwater vehicle, carrying out discretization, and establishing a nonlinear single beacon positioning model;
D. converting a discrete-state nonlinear single beacon positioning model into a linear time-varying model through state augmentation;
E. when the underwater vehicle receives the relative speed of the underwater vehicle and water under a satellite coordinate system obtained by a Doppler velocimeter and the vehicle attitude heading obtained by an attitude heading reference system, Kalman filtering prediction is carried out;
F. when the underwater vehicle receives an absolute speed observation measured by a Doppler velocimeter, the underwater vehicle calculates the self ground speed under an underwater local inertial coordinate system by combining an attitude heading angle of the underwater vehicle obtained by an attitude heading reference system so as to obtain a current speed observation, and updates the current speed through Kalman filtering;
G. when the underwater vehicle receives the observation of the depth meter, depth updating is carried out through Kalman filtering;
H. after the underwater vehicle receives the underwater sound signals, the underwater sound signal transmission time is obtained through the known underwater sound signal emission time, the square of the underwater sound signal transmission time is used as an observation variable, and the underwater sound signal transmission time is updated through Kalman filtering.
On the basis of the above scheme, specifically, in the step C, the method for establishing the kinematic model includes:
the position vector is defined as:
p=[x y z]T
wherein: x, y and z are space position coordinates of the underwater vehicle in an underwater local inertia coordinate system;
defining the ocean current velocity vector as:
vc=[vcx vcy vcz]T
wherein: v. ofcx,vcy,vczThe method comprises the following steps of (1) obtaining unknown ocean current velocities in x, y and z directions in an underwater local inertia coordinate system;
defining the underwater vehicle to water velocity vector as:
vw=[vwx vwy vwz]T
wherein: v. ofwx,vwy,vwzThe relative speeds of the underwater vehicle and the water in the directions of x, y and z in an underwater local inertia coordinate system are respectively obtained by calculation through data measured by an attitude heading reference system and a Doppler velocimeter, and the calculation formula is as follows:
wherein:
the relative velocity vector of the underwater vehicle and the water under the satellite coordinate system measured by the Doppler velocimeter,
the matrix elements of the rotation matrix are related to the attitude angle and the heading angle of the underwater vehicle measured by the attitude heading reference system;
the calculation formula of (2) is as follows:
wherein:
respectively measuring a roll angle, a pitch angle and a course angle of the underwater vehicle by an attitude course reference system;
note veIs an unknown effective acoustic velocity underwater;
solving for unknown p, vcAnd veAnd taking into account the corresponding uncertainty, obtaining a kinematic model of the underwater vehicle:
wherein: omegap=[ωpx ωpy ωpz]TIs the position uncertainty, omega, of the underwater vehicle in the x, y and z directionsc=[ωcx ωcy ωcz]TIs the uncertainty of the ocean current in the x, y and z directions; omegaeIs the effective sound speed uncertainty.
On the basis of the above scheme, specifically, in the step C, the method for establishing the observation model includes:
s1, establishing an observation model of underwater acoustic signal transmission time;
recording the time T of the underwater acoustic beacon for transmitting the underwater acoustic signaleWithout loss of generality, record the underwater acoustic beacon atThe space position coordinate in the underwater local inertia coordinate system is s ═ 000]TThe time when the underwater vehicle receives the underwater acoustic signal is Ta,TeAnd TaAre all known quantities, and the observation equation is:
wherein: v. oftCorresponding observation noise;
s2, establishing an ocean current flow velocity observation model;
according to the absolute speed of the underwater vehicle under the satellite coordinate system measured by the Doppler velocimeter
And (3) calculating to obtain the representation of the absolute speed of the underwater vehicle under an underwater local inertial coordinate system by combining the attitude and the heading of the underwater vehicle measured by the attitude and heading reference system:
wherein: v. ofg=[vgx vgy vgz]TThe method comprises the following steps of (1) obtaining components of the absolute speed of an underwater vehicle in x, y and z directions under a local inertial coordinate system;
according to vgAnd vwAnd calculating to obtain the observed quantity of the ocean current velocity as follows:
mc=vg-vw
wherein: m isc=[mcx mcy mcz]TRepresenting the observation of ocean currents in three directions;
the ocean current observation equation is linear and satisfies mc=vc+vvc;
Wherein: v. ofvcObserving the noise vector, v, for the ocean currentsvc=[vvcx vvcy vvcz]TWherein v isvcxCurrent in the x directionObserving noise; v. ofvcyObserving noise for the ocean current in the y direction; v. ofvczObserving noise for the ocean current in the z direction;
s3, establishing a depth observation model;
recording the observed quantity of a depth gauge carried by an underwater vehicle as mzThen its observation equation is
mz=ap+vz
Wherein: a ═ 001],vzNoise was observed for the depth gauge.
On the basis of the above scheme, specifically, in the step C, the discretization method of the kinematic model and the observation model includes:
s1, discretizing a kinematic model;
taking the variable plus subscript k as a discrete time index, taking Delta T as a discrete interval, and discretizing a kinematic model as follows:
pk+1=pk+ΔTvc,k+ΔTvw,k+ωp,k
vc,k+1=vc,k+ωc,k
ve,k+1=ve,k+ωe,k
wherein: omegap,k,ωc,k,ωe,kRepresenting process noise in discrete states;
s2, discretizing an observation model;
assuming that the underwater vehicle receives the underwater sound signal at the moment k, the discrete underwater sound signal transmission time observation equation is as follows:
wherein v ist,kObserving noise for underwater sound signal transfer time;
assuming that the ocean current velocity observation can be obtained at each discrete time point, the observation equation after the dispersion is as follows:
mvc,k=vc,k+vvc,k
wherein v isvc,kIs k atObserving noise by carving ocean current velocity;
also, assuming that depth gauge observations are available at each discrete time point, the post-discretization observation equation is:
mz,k=apk+vz,k
wherein v isz,kNoise was observed for the depth gauge at time k.
On the basis of the above scheme, specifically, the step D includes:
s1, processing a kinematic model;
defining discrete state variables:
from the discrete-time kinematics model of the underwater vehicle, one can obtain:
x1,k+1=x1,k+ΔTx3,kvw,k+ΔTx2,k+ω1,k
x2,k+1=x2,k+ω2,k
x3,k+1=x3,k+ω3,k
wherein: omega1,k,ω2,k,ω3,kRespectively corresponding process noise;
the discrete state variables are further defined:
obtaining:
x5,k+1=x5,k+ω5,k
wherein: omega4,k,ω5,k,ω6,kRespectively corresponding process noise;
defining a state vector and a noise vector:
x is thenkThe kinematic equation of (a) is:
xk+1=Akxk+ωk
wherein:
wherein: i is3Identity matrix representing three dimensions, 0m×nRepresenting a matrix with elements of 0 and dimension of m rows and n columns;
s2, processing an observation model;
from x1,k,x2,k,x3,k,x5,k,x6,kThe definition of (a) can be given as:
x2,k=vc,kx3,k
when the underwater vehicle obtains ocean current observation mvc,kWhen the method is taken as a known quantity, and combined with an ocean current observation equation, the method can obtain the following steps:
0=x2,k-mvc,kx3,k+vs1,k
wherein: v. ofs,1,vs,2And vs,3For the corresponding observation noise, the relationship between the observation noise of ocean current and the state of the linear augmentation model is as follows:
vs1,k=vvc,kx3,k
likewise, from x1,k,x3,kThe definition of (a) and the depth gauge observation equation can be obtained:
0=ax1,k-mz,kx3,k+vs4,kwherein: v. ofs,4To correspond to observed noise, and vs4,k=vz,kx3,k;
From x4,kThe definition of (a) can be given as:
wherein:
constructing an observation vector and an observation noise vector as follows:
the corresponding observation equation is:
m1,k=C1,kxk+v1,k
m2,k=C2,kxk+v2,k
m3,k=C3,kxk+v3,k
wherein:
on the basis of the above scheme, specifically, the method adopted in step E is:
recording the relative speed of the underwater vehicle and water under a satellite coordinate system obtained by the Doppler velocimeter received by the underwater vehicle at the moment k
And the attitude heading of the aircraft obtained by the attitude heading reference system
Constructing a rotation matrix
By
Obtaining the relative speed of the underwater vehicle and the water under the local inertial coordinate system, and further constructing a corresponding system matrix A
k;
The state prior estimation of the augmented linear model obtained by the prediction link of Kalman filtering is as follows:
wherein:
and P
k|kThe posterior state and the posterior variance at the moment k are respectively;
and P
k+1|kRespectively a prior state and a prior variance at the moment k + 1; q
kThe covariance matrix of the process noise at the time k is a symmetric positive definite matrix, and the specific parameters of the covariance matrix are the process noise omega
kThe statistical property decision of (a) can be obtained by offline modulation.
On the basis of the above scheme, specifically, the method adopted in step F is:
recording the absolute speed observation of the underwater vehicle under a satellite coordinate system measured by a Doppler velocimeter at the moment of k +1, and calculating the absolute speed of the vehicle under a local inertial coordinate system according to a vehicle attitude heading angle obtained by an attitude heading reference system:
according to known vw,k+1And constructing ocean current observation at the k +1 moment:
mvc,k+1=vg,k+1-vw,k+1
according to mvc,k+1Constructing an observation matrix C1,k+1And an observation vector m1,k+1;
According to the updating link of Kalman filtering, the state posterior estimation of the obtained augmented linear model is as follows:
Pk+1|k+1=Pk+1|k-Kk+1C1,k+1Pk+1|k
wherein: kk+1Is Kalman gain; r1,k+1A noise covariance matrix related to the observation of the current velocity at the moment k +1 is a symmetric positive definite matrix, and the specific parameters of the matrix are observed by the observation noise v1,k+1The statistical property decision of (a) can be obtained by offline modulation.
On the basis of the above scheme, specifically, the method adopted in step G is:
recording the depth m of the underwater vehicle measured by a depth meter received by the underwater vehicle at the moment of k +1z,k+1Constructing an observation matrix C based thereon2,k+1And an observed variable m2,k+1(ii) a According to the updating link of Kalman filtering, the state posterior estimation of the obtained augmented linear model is as follows:
Pk+1|k+1=Pk+1|k-Kk+1C2,k+1Pk+1|k
wherein: r2,k+1A noise covariance matrix related to the depth observation at the moment of k +1, which is a symmetric positive definite matrix with specific parameters of observation noise v2,k+1The statistical property decision of (a) can be obtained by offline modulation.
On the basis of the above scheme, specifically, the method adopted in step H is:
recording the underwater sound signal received by the underwater vehicle at the moment k +1, and calculating the transmission time m of the underwater sound signal at the momentt,k+1(ii) a Constructing an observation matrix C3,k+1And an observed variable m3,k+1According to the updating link of Kalman filtering, the state posterior estimation of the obtained augmented linear model is as follows:
Pk+1|k+1=Pk+1|k-Kk+1C3,k+1Pk+1|k
wherein: r3,k+1A noise covariance matrix related to the observation of the underwater sound signal transmission time at the moment k +1 is a symmetric positive definite matrix, and the specific parameters of the matrix are observed by the observation noise v3,k+1The statistical property decision of (a) can be obtained by offline modulation.
On the basis of the above scheme, further, according to the posterior state estimation of the augmented linear model obtained in the step F, G, H, the posterior state estimation of the original nonlinear model can be calculated, and the calculation method is as follows:
wherein:
and
the posterior estimation of the effective sound velocity, the position and the ocean current velocity at the moment of k +1 respectively; in order to further ensure the stability of the positioning model, the estimation of the effective sound velocity is limited, that is, the following steps are selected:
wherein: v. ofmAnd vMThe lower bound and the upper bound of the effective sound velocity are respectively set according to the actual situation; sat (x, a, b) is the clipping function, whose output is:
has the advantages that: according to the method, through state augmentation, a nonlinear underwater acoustic signal transmission time observation model in an underwater single beacon positioning model is converted into a linear time-varying model, the linear time-varying single beacon positioning model is constructed, and position calculation is carried out through Kalman filtering. On the premise of meeting the observability of a positioning model, the method provided by the invention has global convergence. That is, when the initial position error of the underwater vehicle or the position error at a certain moment is large, the proposed method can still ensure the convergence of the positioning error.
Detailed Description
In embodiment 1, referring to fig. 1, an underwater vehicle single beacon positioning method with global convergence is provided, where the underwater vehicle is equipped with a hydrophone, a doppler velocimeter, a depth meter, an attitude and heading reference system, and a GPS; the underwater sound beacon broadcasts the underwater sound signal periodically; the method comprises the following steps:
A. and establishing an underwater local inertia coordinate system by taking any point in the positioning area as an origin and setting the east, north and sky directions as x, y and z axes respectively.
B. And acquiring the initial position of the underwater vehicle in an underwater local inertial coordinate system through the carried GPS.
C. And establishing a kinematics model and an observation model of the underwater vehicle, carrying out discretization, and establishing a nonlinear single beacon positioning model.
The establishment method of the kinematic model comprises the following steps:
the position vector is defined as:
p=[x y z]T
wherein: x, y and z are space position coordinates of the underwater vehicle in an underwater local inertia coordinate system;
defining the ocean current velocity vector as:
vc=[vcx vcy vcz]T
wherein: v. ofcx,vcy,vczThe method comprises the following steps of (1) obtaining unknown ocean current velocities in x, y and z directions in an underwater local inertia coordinate system;
defining the underwater vehicle to water velocity vector as:
vw=[vwx vwy vwz]T
wherein: v. ofwx,vwy,vwzThe relative speeds of the underwater vehicle and the water in the directions of x, y and z in an underwater local inertia coordinate system are respectively obtained by calculation through data measured by an attitude heading reference system and a Doppler velocimeter, and the calculation formula is as follows:
wherein:
the relative velocity vector of the underwater vehicle and the water under the satellite coordinate system measured by the Doppler velocimeter,
the matrix elements of the rotation matrix are related to the attitude angle and the heading angle of the underwater vehicle measured by the attitude heading reference system;
the calculation formula of (2) is as follows:
wherein:
respectively measuring a roll angle, a pitch angle and a course angle of the underwater vehicle by an attitude course reference system;
note veIs an unknown effective acoustic velocity underwater;
solving for unknown p, vcAnd veAnd taking into account the corresponding uncertainty, obtaining a kinematic model of the underwater vehicle:
wherein: omegap=[ωpx ωpy ωpz]TIs the position uncertainty, omega, of the underwater vehicle in the x, y and z directionsc=[ωcx ωcy ωcz]TIs the uncertainty of the ocean current in the x, y and z directions; omegaeIs the effective sound speed uncertainty.
The establishment method of the observation model comprises the following steps:
s1, establishing an observation model of underwater acoustic signal transmission time;
recording the time T of the underwater acoustic beacon for transmitting the underwater acoustic signaleWithout loss of generality, the spatial position coordinate of the underwater acoustic beacon in the underwater local inertial coordinate system is recorded as s ═ 000]TThe time when the underwater vehicle receives the underwater acoustic signal is Ta,TeAnd TaAre all known quantities, and the observation equation is:
wherein: v. oftCorresponding observation noise;
s2, establishing an ocean current flow velocity observation model;
according to the absolute speed of the underwater vehicle under the satellite coordinate system measured by the Doppler velocimeter
And (3) calculating to obtain the representation of the absolute speed of the underwater vehicle under an underwater local inertial coordinate system by combining the attitude and the heading of the underwater vehicle measured by the attitude and heading reference system:
wherein: v. ofg=[vgx vgy vgz]TThe method comprises the following steps of (1) obtaining components of the absolute speed of an underwater vehicle in x, y and z directions under a local inertial coordinate system;
according to vgAnd vwAnd calculating to obtain the observed quantity of the ocean current velocity as follows:
mc=vg-vw
wherein: m isc=[mcx mcy mcz]TRepresenting the observation of ocean currents in three directions;
the ocean current observation equation is linear and satisfies mc=vc+vvc;
Wherein: v. ofvcObserving the noise vector, v, for the ocean currentsvc=[vvcx vvcy vvcz]TWherein v isvcxObserving noise for the ocean current in the x direction; v. ofvcyObserving noise for the ocean current in the y direction; v. ofvczObserving noise for the ocean current in the z direction;
s3, establishing a depth observation model;
recording the observed quantity of a depth gauge carried by an underwater vehicle as mzThen its observation equation is
mz=ap+vz
Wherein: a ═ 001],vzNoise was observed for the depth gauge.
The discretization method of the kinematic model and the observation model comprises the following steps:
s1, discretizing a kinematic model;
taking the variable plus subscript k as a discrete time index, taking Delta T as a discrete interval, and discretizing a kinematic model as follows:
pk+1=pk+ΔTvc,k+ΔTvw,k+ωp,k
vc,k+1=vc,k+ωc,k
ve,k+1=ve,k+ωe,k
wherein: omegap,k,ωc,k,ωe,kRepresenting process noise in discrete states;
s2, discretizing an observation model;
assuming that the underwater vehicle receives the underwater sound signal at the moment k, the discrete underwater sound signal transmission time observation equation is as follows:
wherein v ist,kObserving noise for underwater sound signal transfer time;
assuming that the ocean current velocity observation can be obtained at each discrete time point, the observation equation after the dispersion is as follows:
mvc,k=vc,k+vvc,k
wherein v isvc,kObserving noise for the ocean current velocity at the moment k;
also, assuming that depth gauge observations are available at each discrete time point, the post-discretization observation equation is:
mz,k=apk+vz,k
wherein v isz,kNoise was observed for the depth gauge at time k.
D. And converting the discrete-state nonlinear single beacon positioning model into a linear time-varying model through state augmentation.
S1, processing a kinematic model;
defining discrete state variables:
from the discrete-time kinematics model of the underwater vehicle, one can obtain:
x1,k+1=x1,k+ΔTx3,kvw,k+ΔTx2,k+ω1,k
x2,k+1=x2,k+ω2,k
x3,k+1=x3,k+ω3,k
wherein: omega1,k,ω2,k,ω3,kRespectively corresponding process noise;
the discrete state variables are further defined:
obtaining:
x5,k+1=x5,k+ω5,k
wherein: omega4,k,ω5,k,ω6,kRespectively corresponding process noise;
defining a state vector and a noise vector:
x is thenkThe kinematic equation of (a) is:
xk+1=Akxk+ωk
wherein:
wherein: i is3Identity matrix representing three dimensions, 0m×nRepresenting a matrix with elements of 0 and dimension of m rows and n columns;
s2, processing an observation model;
from x1,k,x2,k,x3,k,x5,k,x6,kThe definition of (a) can be given as:
x2,k=vc,kx3,k
when the underwater vehicle obtains ocean current observation mvc,kWhen the method is taken as a known quantity, and combined with an ocean current observation equation, the method can obtain the following steps:
0=x2,k-mvc,kx3,k+vs1,k
wherein: v. ofs,1,vs,2And vs,3For the corresponding observation noise, the relationship between the observation noise of ocean current and the state of the linear augmentation model is as follows:
vs1,k=vvc,kx3,k
likewise, from x1,k,x3,kThe definition of (a) and the depth gauge observation equation can be obtained:
0=ax1,k-mz,kx3,k+vs4,k
wherein: v. ofs,4To correspond to observed noise, and vs4,k=vz,kx3,k;
From x4,kThe definition of (a) can be given as:
wherein:
constructing an observation vector and an observation noise vector as follows:
the corresponding observation equation is:
m1,k=C1,kxk+v1,k
m2,k=C2,kxk+v2,k
m3,k=C3,kxk+v3,k
wherein:
E. and when the underwater vehicle receives the relative speed of the underwater vehicle and water under the satellite coordinate system obtained by the Doppler velocimeter and the vehicle attitude heading obtained by the attitude heading reference system, Kalman filtering prediction is carried out.
Recording the relative speed of the underwater vehicle and water under a satellite coordinate system obtained by the Doppler velocimeter received by the underwater vehicle at the moment k
And the attitude heading of the aircraft obtained by the attitude heading reference system
Constructing a rotation matrix
By
Obtaining the relative speed of the underwater vehicle and the water under the local inertial coordinate system, and further constructing a corresponding system matrix A
k;
The state prior estimation of the augmented linear model obtained by the prediction link of Kalman filtering is as follows:
wherein:
and P
k|kThe posterior state and the posterior variance at the moment k are respectively;
and P
k+1|kRespectively a prior state and a prior variance at the moment k + 1; q
kThe covariance matrix of the process noise at the time k is a symmetric positive definite matrix, and the specific parameters of the covariance matrix are the process noise omega
kThe statistical property decision of (a) can be obtained by offline modulation.
F. When the underwater vehicle receives an absolute speed observation measured by the Doppler velocimeter, the self ground speed under an underwater local inertial coordinate system is calculated by combining an underwater vehicle attitude heading angle obtained by the attitude heading reference system, so that a current speed observation is obtained, and the current speed is updated through Kalman filtering.
Recording the absolute speed observation of the underwater vehicle under a satellite coordinate system measured by a Doppler velocimeter at the moment of k +1, and calculating the absolute speed of the vehicle under a local inertial coordinate system according to a vehicle attitude heading angle obtained by an attitude heading reference system:
according to known vw,k+1And constructing ocean current observation at the k +1 moment:
mvc,k+1=vg,k+1-vw,k+1
according to mvc,k+1Constructing an observation matrix C1,k+1And an observation vector m1,k+1;
According to the updating link of Kalman filtering, the state posterior estimation of the obtained augmented linear model is as follows:
Pk+1|k+1=Pk+1|k-Kk+1C1,k+1Pk+1|k
wherein: kk+1Is Kalman gain; r1,k+1A noise covariance matrix related to the observation of the current velocity at the moment k +1 is a symmetric positive definite matrix, and the specific parameters of the matrix are observed by the observation noise v1,k+1The statistical property decision of (a) can be obtained by offline modulation.
G. And when the underwater vehicle receives the observation of the depth meter, the depth is updated through Kalman filtering.
Recording the depth m of the underwater vehicle measured by a depth meter received by the underwater vehicle at the moment of k +1z,k+1Constructing an observation matrix C based thereon2,k+1And an observed variable m2,k+1(ii) a According to the updating link of Kalman filtering, the state posterior estimation of the obtained augmented linear model is as follows:
Pk+1|k+1=Pk+1|k-Kk+1C2,k+1Pk+1|k
wherein: r2,k+1A noise covariance matrix related to the depth observation at the moment of k +1, which is a symmetric positive definite matrix with specific parameters of observation noise v2,k+1The statistical property decision of (a) can be obtained by offline modulation.
H. After the underwater vehicle receives the underwater sound signals, the underwater sound signal transmission time is obtained through the known underwater sound signal emission time, the square of the underwater sound signal transmission time is used as an observation variable, and the underwater sound signal transmission time is updated through Kalman filtering.
Recording the underwater sound signal received by the underwater vehicle at the moment k +1, and calculating the transmission time m of the underwater sound signal at the momentt,k+1(ii) a Constructing an observation matrix C3,k+1And an observed variable m3,k+1According to the updating link of Kalman filtering, the state posterior estimation of the obtained augmented linear model is as follows:
Pk+1|k+1=Pk+1|k-Kk+1C3,k+1Pk+1|k
wherein: r3,k+1A noise covariance matrix related to the observation of the underwater sound signal transmission time at the moment k +1 is a symmetric positive definite matrix, and the specific parameters of the matrix are observed by the observation noise v3,k+1Determination of statistical characteristics ofAnd (4) modulation under the threading line.
Further, according to the posterior state estimation of the augmented linear model obtained in the step F, G, H, the posterior state estimation of the original nonlinear model can be calculated, and the calculation method is as follows:
wherein:
and
the posterior estimation of the effective sound velocity, the position and the ocean current velocity at the moment of k +1 respectively; in order to further ensure the stability of the positioning model, the estimation of the effective sound velocity is limited, that is, the following steps are selected:
wherein: v. ofmAnd vMThe lower bound and the upper bound of the effective sound velocity are respectively set according to the actual situation; sat (x, a, b) is the clipping function, whose output is:
example 2 the method described in example 1 was verified by simulation data.
By way of comparison, the present embodiment also shows the positioning result of the conventional underwater single beacon positioning method based on Extended Kalman Filtering (EKF) to perform position solution. The total simulation time length is 5000 seconds, the simulated effective sound velocity is 1500 m/s in the whole movement process, and the simulated ocean current velocities in the three directions are-0.1 m/s, 0.2 m/s and 0.1 m/s respectively. The simulated underwater sound signal emission period is 10 seconds, namely the transmission time updating period of the underwater sound signal is 10 seconds. The sampling periods of the simulated Doppler velocimeter, the simulated attitude heading reference system and the simulated depth meter are all 0.1 second (equivalent to 10Hz sampling frequency), namely the system discrete period, the ocean current velocity updating period and the aircraft depth updating period are all 0.1 second.
The simulated individual sensor noise parameters are as follows:
in the process of numerical verification, the initial parameters of the filter are set as follows: (1) the initial errors of the positions in the x direction and the y direction are both 500 meters; (2) the initial error of the position in the z direction is 50 m; (3) the initial values of the ocean currents in the x direction, the y direction and the z direction are both 0 m/s; (4) the initial value of the effective sound speed is 1450 m/s; (5) the ocean current uncertainty standard deviation is 1 m/s; (6) the uncertainty standard deviation of the water velocity observation of the aircraft is 10-4M/s; (7) the standard deviation of the uncertainty of the effective sound velocity of the proposed method is 10-7Meter/second, standard deviation of effective sound velocity uncertainty of EKF-based traditional underwater single beacon positioning system is 10-5M/s; (8) the standard deviation of the underwater acoustic signal transmission time observation noise is 10-5Second; (9) the standard deviation of ocean current observation noise is 0.002 m/s; (10) the standard deviation of the observation noise of the depth meter is 0.001 meter; (11) upper and lower bounds v of effective acoustic velocityMAnd vm1600 m/s and 1400 m/s, respectively.
The results of 500 independent sub-Monte Carlo simulations were used to verify the proposed method. The evaluation index of the positioning performance of the two positioning methods is mean square positioning error RMS
ΔHAnd mean square effective acoustic velocity error
The two calculation methods are as follows:
wherein:
and
real and estimated vehicle position coordinates in the ith Monte Carlo simulation,
and
the real and estimated effective sound velocities in the ith Monte Carlo simulation, respectively, where M-500 represents the total number of simulations. According to fig. 2 and fig. 3, it can be seen that the proposed method can converge to a smaller value faster under the condition of a larger initial position error, whereas the conventional EKF-based single beacon positioning method cannot converge and filtering divergence occurs.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.