Disclosure of Invention
In order to solve the technical problems, the invention provides a low-speed small target track filtering method and device based on interactive multi-model-Kalman filtering.
A low-slow small target track filtering method based on interactive multi-model-Kalman filtering comprises the following steps:
step 1: obtaining an estimated value X of a target initial state through a track initial algorithm0And initial state estimate covariance matrix P0;
Step 2: setting a target motion model set, and obtaining a corresponding state transition matrix and a radar measurement matrix according to the target motion state;
and step 3: calculating the prediction probability and the mixing probability of the target motion model corresponding to the kth moment;
and 4, step 4: calculating a target motion model mixed state and a mixed covariance corresponding to the kth moment;
and 5: calculating a one-step predicted value and a predicted covariance matrix of the mixed state of each target motion model at the (k + 1) th moment and a measured one-step predicted value and a predicted covariance matrix;
step 6: calculating a target state estimation value and an estimated covariance matrix at the (k + 1) th moment, and calculating a likelihood function and a target motion model probability;
the value of k is incremented by 1 and then step 3 is performed again.
In a preferred embodiment, the track initiation algorithm comprises: a logic track starting algorithm or a track starting algorithm based on Hough transformation; the detection form of the radar detector comprises the following steps: square rate detection or linear detection.
In a preferred embodiment, the set of object motion models is defined as [ M [ ]1,M2,...,Mn]The corresponding state transition matrix is defined as [ F ]1,F2,...,Fn]The radar measurement matrix is defined as [ H ]1,H2,...,Hn]Wherein n represents the number of target motion models in a target motion model set, the target motion model set is a target motion model set obtained according to different motion states and motion characteristics of a target, the target motion model comprises a uniform velocity linear motion model, a uniform acceleration linear motion model and a cooperative turning model, wherein M is the number of target motion models in the target motion model set, and M is the number of target motion models in the target motion modeliRepresenting the motion model of the ith object, FiRepresenting the state transition matrix corresponding to the ith object motion model, HiAnd (3) representing a radar measurement matrix corresponding to the ith target motion model, wherein i is a positive integer greater than or equal to 1.
In a preferred embodiment, the object motion model predicts a probability
And mixed probabilities
Is obtained by the following steps:
3a) wherein the object motion model predicts the probability
Representing the probability of the motion model of the ith object from time k to time k +1,
representing the probability of the occurrence of the jth target motion model at the kth time, and calculating the prediction probability of the target motion model by using the following formula
Wherein, gamma isi|j=Pr{rk+1=i|rkJ, wherein said Γ ″i|jRepresenting the probability of a transition from an object motion model j to an object motion model i when the object is moving, where rk、rk+1Respectively representing target motion models of a target at the k moment and the k +1 moment, Pr {. is used for solving the probability of occurrence of an event, and Σ is used for summing operation;
3b) wherein the probability of mixing
Representing the probability of transferring from the ith target motion model to the jth target motion model from the k time to the k +1 time when the target moves, and calculating the mixed probability by using the result obtained in the step 3a) and the following formula
Wherein c represents a normalization constant, the magnitude of c and
as a result of the calculation, k represents the kth time, and k is a positive integer of 1 or more.
In a preferred embodiment, the time k mixing state is obtained by the following steps
Sum and mixture covariance
4a) Wherein
And
representing the interaction result of the state and the covariance, and calculating the mixed state at the k-th time by using the result obtained in the step 3b) and the following formula
Sum and mixture covariance
Wherein
And
updated values representing the hybrid state and hybrid covariance of the target at time k (.)
TRepresenting a matrix transpose operation.
In a preferred embodiment, each target motion model M at the k +1 th moment is calculated by the following steps
iOne-step prediction of hybrid states
And a prediction covariance matrix
And one-step prediction value of measurement
And the prediction covariance momentMatrix of
Where i represents the ith object motion model:
5a) calculating a one-step predicted value of the mixing state at the k +1 th time by using the following formula
And the prediction covariance matrix
Wherein u isiRepresenting the process noise matrix of the ith target motion model, wherein the known process noise obeys the mean value of 0 and the standard deviation is sigmauNormal distribution of (2); qik+1|kRepresenting a process noise covariance matrix of an ith target motion model from a kth time to a (k + 1) th time;
5b) calculating a predicted value of one step measured from the k-th time to the k + 1-th time by using the result obtained in the step 5a) and the following formula
And a prediction covariance matrix
Wherein R isik+1|kRepresenting the measured noise covariance matrix of the ith target motion model from the kth moment to the (k + 1) th moment, wherein the measured noise covariance matrix has the following size: rik+1|k=wik+1|k(wik+1|k)TWherein w isik+1|kIndicating the movement of the ith objectMeasuring noise matrixes from the kth moment to the (k + 1) th moment of the model, wherein the known measuring noise obeys a mean value of 0 and a standard deviation of sigmawWhere i is 1,2, … n.
In a preferred embodiment of the present invention,
wherein σuRepresenting the process noise standard deviation, TsRepresenting the scan period of the radar antenna.
In a preferred embodiment, the target state estimate at time k +1 of the ith moving target model is calculated by
And estimate covariance matrix
And calculating likelihood functions
Probability of target motion model
6a) Calculating the target state estimation value of the ith moving target model at the (k + 1) th moment according to the calculation result of the step 5 and the following formula
And estimate covariance matrix
Wherein z isk+1Indicating the measured value of the target at the k +1 th time,(·)TFor matrix transposition operations, (.)-1Performing matrix inversion operation;
6b) calculating the likelihood function at the k +1 th time using the following formula based on the result obtained in step 6a)
Where exp (-) denotes solving a power series based on the natural logarithm e, det (-) denotes the value of the determinant,
represents the square root operation;
6c) calculating the probability of the target motion model at the k +1 th moment according to the likelihood function obtained by calculation in the step 6b) and the following formula
The target association algorithm comprises the following steps: a nearest neighbor data association algorithm, a probability data interconnection algorithm or a joint probability data interconnection algorithm.
The invention discloses a low-slow small target track filtering device based on interactive multi-model-Kalman filtering, which comprises:
a processor;
a memory in electronic communication with the processor, the memory having stored therein instructions that, when executed by the processor, are capable of causing the apparatus to perform the method of any one of claims 1-8.
The present invention discloses a computer readable storage medium having stored thereon instructions which, when executed by a processor, implement a method as in one of the above.
The invention has the beneficial effects that: the method can be applied to targets (such as unmanned aerial vehicles, birds and the like) which are low in flying height, low in flying speed and small in size and difficult to detect, and filtering operation after correlation is completed. According to the method, an interactive multi-model-Kalman filtering algorithm is added in the radar data processing process, so that smooth target tracks can be realized, the association accuracy is improved, and the radar detection precision is improved compared with the traditional process of directly taking the measured data as final track update data.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
Fig. 1 is a general flowchart of an implementation of a low-slow small target trajectory filtering method based on an interactive multi-model-kalman filtering, and as shown in the figure, the low-slow small target trajectory filtering method of the present invention includes the following steps:
step 1 is performed at block 101: obtaining an estimated value X of a target initial state through a track initial algorithm0And initial state estimate covariance matrix P0;
Step 2 is performed at block 102: setting a target motion model set, and obtaining a corresponding state transition matrix and a radar measurement matrix according to motion characteristics;
step 3 is performed at block 103: calculating model prediction probability and mixing probability corresponding to the kth moment;
step 4 is performed at block 104: calculating a mixing state and a mixing covariance at the kth moment;
step 5 is performed at block 105: calculating a one-step predicted value and a predicted covariance matrix of each model mixed state at the (k + 1) th moment and a measured one-step predicted value and a predicted covariance matrix;
step 6 is performed at block 106: calculating a target state estimation value and an estimated covariance matrix at the (k + 1) th moment, and calculating a likelihood function and a model probability;
the value of k is incremented by 1 and then step 3 is performed again.
The detailed calculation method of the present invention is described below: in step 1, firstly initializing parameters, setting the initial output of the detector to be 0, and waiting for the detector to receive signals; obtaining the initial state estimation X of the target track through the target track initial algorithm0And a state estimation covariance matrix P0(ii) a The target track initiation algorithm includes a logic track initiation algorithm and a track initiation algorithm based on Hough transformation, and the example selects but is not limited to the track initiation algorithm based on Hough transformation. The detection form of the radar detector includes square rate detection, linear detection, etc., and the square rate detector is selected but not limited in this example.
In step 2, a set of object motion models is set to [ M [ ]1,M2,...,Mn]According to the motion characteristics, the corresponding state transition matrix is obtained as [ F ]1,F2,...,Fn]The radar measurement matrix is [ H ]1,H2,...,Hn]Wherein n represents the number of models in the model set;
the target motion model is a model set obtained according to different motion states and motion characteristics of the target, and common target motion models comprise a uniform velocity linear motion model, a uniform acceleration linear motion model, a cooperative turning model and the like. In the embodiment, but not limited to, a uniform linear motion model and a uniform acceleration linear motion model are selected to form a target motion model set.
This example was verified based on measured data with the following model parameters:
three-dimensional uniform linear motion model state transition matrix F1Comprises the following steps:
wherein T issIndicating the scanning period of the radar antenna, in this example T is chosens=3s。
The three-dimensional uniform linear motion model measurement matrix is as follows:
three-dimensional uniform acceleration linear motion model state transition matrix F1Comprises the following steps:
the three-dimensional uniform acceleration linear motion model measurement matrix is as follows:
step 3, obtaining the model M according to the step 2
i(where i ═ 1, 2.. times, n) and the corresponding model prediction probabilities are calculated by the measurement matrix
And mixed probabilities
3a) Calculating model prediction probability using the following equation
Wherein, gamma isi|j=Pr{rk+1=i|rkJ, the probability of the transition from model j to model i when representing the object motion is Γi|j,rk、rk+1Respectively representing target motion models of a target at the k moment and the k +1 moment, Pr {. is used for solving the probability of occurrence of an event, and Σ is used for summing operation;
3b) calculating a mixture probability using the result obtained in step 3a) and the following formula
Wherein c represents a normalization constant, magnitude and
the calculation results are related;
step 4, calculating the mixing state at the kth moment according to the model prediction probability and the mixing probability obtained in the step 3
Sum and mixture covariance
4a) Calculating the mixing state at the k-th time by using the result obtained in the step 3b) and the following formula
Sum and mixture covariance
Wherein
And
represents the state update value of the target at time k (.)
TRepresenting a matrix transpose operation.
Step 5, calculating each model M at the k +1 th moment according to the state transition matrix obtained in the step 2 and the mixed state obtained in the step 4
i(where i ═ 1, 2.., n) one-step predictive value of the mixing regime
And covariance matrix
5a) Calculating a one-step predicted value of the mixing state at the k +1 th time by using the following formula
And the prediction covariance matrix
Wherein u isiRepresenting a process noise matrix, known as the process noise obeys a mean of 0 and a standard deviation of σuNormal distribution of (2); qik+1|kRepresents the process noise covariance matrix from time k to time k +1, in this example taking the form:
wherein σuExpressing the process noise standard deviation, take σp=0.1。
Step 6, calculating the one-step prediction of the measurement at the k +1 th moment according to the measurement matrix obtained in the step 2 and the state one-step prediction state and covariance matrix obtained in the step 5
And variance
6a) Calculating a predicted value measured at the k +1 th moment by using the result obtained in the step 5 and the following formula
And a prediction covariance matrix
Wherein R isik+1|kRepresenting the measured noise covariance matrix of the ith model from the kth time to the (k + 1) th time, with the magnitude: rik+1|k=wik+1|k(wik+1|k)TWherein w isik+1|kRepresenting the measurement noise matrix of the ith model from the kth time to the kth +1 time, wherein the known measurement noise obeys a mean value of 0 and a standard deviation of sigmawNormal distribution of (2);
step 7, updating the target state estimation at the (k + 1) th moment according to the results of the step 5 and the step 6 by a track association algorithm
And estimate covariance
And calculating likelihood functions
7a) Calculating the estimated value of the target state at the k +1 th moment according to the calculation results of the step 5 and the step 6 and the following formula
And estimate covariance matrix
Wherein z isk+1Represents the measured value of the target at the k +1 th time, (.)TFor matrix transposition operations, (.)-1A matrix inversion operation is performed.
7b) Calculating the likelihood function at the k +1 th time using the following formula based on the result obtained in step 7a)
Wherein,
representing the probability of the occurrence of the ith moving object model at the time point k +1, exp (-) representing the solution to the power series based on the natural logarithm e, det (-) representing the value of the determinant,
indicating a square root operation.
The target association algorithm comprises a nearest neighbor data association algorithm, a probability data interconnection algorithm, a joint probability data interconnection algorithm and the like, and because the relative clutter density of the experimental simulation environment is low and the target is a single target, the nearest neighbor data interconnection algorithm is selected but not limited in the embodiment.
Step 8, calculating the model probability of the k +1 th moment
Returning to the step 4 to carry out the operation at the next moment.
8a) Calculated according to step 7a)The probability of the model at the k +1 th time is calculated by the following formula
The effect of the present invention will be further explained with the simulation experiment. According to the simulation experiment result, wherein the simulation data source is as follows: the data signals mainly contain distance measurement information of x, y and z axes of a target under a Cartesian three-dimensional rectangular coordinate system. The simulation content comprises: the motion state of the simulation target is not subjected to the data processing of the invention and is compared with the motion state of the simulation target after the data processing of the invention. As can be seen from the simulation results, after the data processing of the invention, the track can be seen to be obviously smooth on the x-z plane reflecting the target pitching precision; and due to the serious irregularity of the original track, part of the traces deviate from the real international distance to be too large to be associated, so that the radar detection probability is reduced. After the track is smooth, the observed point track is more stable relative to the track, so that the point track association success rate is improved to a certain extent, and the aims of improving the radar detection precision and the tracking precision are finally fulfilled. In conclusion, the simulation experiment verifies the correctness, the effectiveness and the reliability of the method.
It will be evident to those skilled in the art that the embodiments of the present invention are not limited to the details of the foregoing illustrative embodiments, and that the embodiments of the present invention are capable of being embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the embodiments being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. Several units, modules or means recited in the system, apparatus or terminal claims may also be implemented by one and the same unit, module or means in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the embodiments of the present invention and not for limiting, and although the embodiments of the present invention are described in detail with reference to the above preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the embodiments of the present invention without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.