Disclosure of Invention
Aiming at the problems that the communication burden is overlarge and the static event triggering condition is difficult to adapt to a dynamic scene in the existing collaborative navigation system, the invention provides a collaborative navigation filtering method based on the dynamic event triggering condition, an event triggering mechanism is introduced into a collaborative navigation filter, a carrier selectively communicates according to the event triggering condition at each sampling moment, and the communication mode is changed from periodic communication to event triggering communication, so that the communication frequency is reduced, and the event triggering estimation is corrected to ensure the navigation performance.
The invention is realized by the following technical scheme:
The invention relates to a collaborative navigation filtering method based on a dynamic event triggering condition, which comprises the following steps:
Step 1, an information sender calculates posterior estimation according to prior state estimation and absolute observation at each sampling moment, and calculates predictive estimation according to prior state estimation;
Step 2, calculating a weighted Euclidean norm of a posterior estimation and predictive estimation difference and judging whether the weighted Euclidean norm exceeds a dynamic trigger threshold, wherein after the posterior estimation is sent to an information receiver when the trigger threshold is exceeded, the information receiver carries out collaborative navigation calculation according to the received state estimation, otherwise, the information sender does not send information to the outside;
And 3, estimating the state of the information sender by the information receiver based on the system model to obtain event trigger estimation, and performing collaborative navigation calculation by utilizing the event trigger estimation and relative observation.
The trigger threshold consists of a constant and a dynamic variable, wherein the dynamic variable gradually converges to zero along with time and accords with the characteristic of convergence along with time of a filtering error, so that the trigger threshold can adapt to the dynamic change of a scene, and when the weighted Euclidean norm of the difference between the posterior estimation and the predictive estimation is larger than the trigger threshold, the trigger condition is met.
Technical effects
The invention introduces a time related variable in the event triggering condition, so that the triggering threshold is reduced along with time, the information sender judges whether the difference value between the posterior estimation and the event triggering estimation exceeds the triggering threshold at each sampling moment, and if the difference value does not exceed the triggering threshold, communication is not carried out, thereby reducing the communication frequency. Compared with the prior art, the method and the device have the advantages that the periodic communication is converted into the event triggering communication, the communication frequency is greatly reduced, and the characteristic that the filtering error in the collaborative navigation filter converges along with time can be well adapted because the triggering threshold is reduced along with time, so that the system robustness is enhanced.
Detailed Description
As shown in FIG. 1, this embodiment is a collaborative navigation system for implementing the method, which includes a prediction estimator, a posterior estimator and an event trigger condition judgment module located at an information sender, and a posterior estimator and a collaborative navigation filter module located at an information receiver, where the information sender and the information receiver sequentially pass through the posterior estimator and respectively calculate respective posterior estimates at each sampling time by using absolute observations, the information sender calculates the prediction estimate at each sampling time by using a system model through the prediction estimator, the event trigger condition judgment module judges whether a trigger condition is satisfied according to the prediction estimate and the posterior estimate, and when the trigger condition is satisfied, sends the posterior estimate to the information receiver, and when the trigger condition is not satisfied, does not send the posterior estimate to the information receiver, the collaborative navigation filter module calculates the event trigger estimate of the information sender according to the judgment result of the event trigger condition, and then performs collaborative navigation solution by using relative observations and the event trigger estimate, and updates the self posterior estimate.
The event trigger condition judging module comprises a difference value calculating unit, a trigger threshold calculating unit and a trigger condition judging unit, wherein the difference value calculating unit calculates a weighted Euclidean norm of the difference between the difference value calculating unit and the information sender according to posterior estimation and predictive estimation, the trigger threshold calculating unit calculates a numerical value of a dynamic trigger threshold according to time, and the trigger condition judging unit judges whether the event trigger condition is met according to the weighted Euclidean norm and the dynamic trigger threshold, and when the trigger condition is met, the information is sent to the information receiver.
The collaborative navigation filtering module comprises a relative observation acquisition unit, an event trigger estimation unit and a filtering unit, wherein the relative observation acquisition unit acquires relative observation between an information sender and the information receiver based on a sensor of the information receiver, the event trigger estimation unit estimates the state of the information sender according to an event trigger condition judgment result to obtain an event trigger estimation, and the filtering unit updates posterior estimation of the information receiver according to the relative observation and the event trigger estimation to obtain a collaborative navigation filtering result.
The embodiment relates to a collaborative navigation filtering method based on the system, which comprises the following steps:
Step one, a posterior estimator of an information sender and an information receiver calculates posterior estimation of each sampling moment by using prior state estimation and absolute observation respectively, wherein the posterior estimator specifically comprises the following steps: Wherein T represents the transpose, -1 represents the inverse of the matrix, the subscript k represents the moment k, the subscript k|k represents the posterior estimate of the moment k, the subscript k|k-1 represents the prior estimate of the moment γk, the superscript 1 represents the sender of the information, the superscript 2 represents the receiver of the information, Representing a posterior estimate of the sender of the k-time information,Representing the a-posteriori estimated covariance,Representing an a priori estimate of the sender of the k time instant information,Representing a priori estimated covariance; representing a posterior estimate of the k-time information receiver, Representing the a-posteriori estimated covariance,Representing an a priori estimate of the receiver of the k time information,Representing a priori estimated covariance, the absolute observations of the information sender areAbsolute observations of information recipients are Representing an absolute observation of the sender of the k-time information,The measurement matrix is represented by a set of data,A state vector representing the sender of the k-time information,Representing the measurement noise and obeying zero-mean Gaussian distribution, the noise covariance isRepresenting an absolute observation of the receiver of the k moment information,The measurement matrix is represented by a set of data,A state vector representing the recipient of the k-time information,Representing the measurement noise and obeying zero-mean Gaussian distribution, the noise covariance is
Step two, a prediction estimator of the information sender calculates the prediction estimation of the information sender at each sampling moment by using a system model, specifically: Wherein the superscript 1, y denotes the predicted estimate of the sender of the information, Representing a predictive estimate of the sender of the k-time information,Representing predictive estimation covariance, the system model of the information sender is that A state transition matrix is represented and is used to represent,Representing process noise and obeying zero-mean Gaussian distribution, the noise covariance is
Step three, a difference value calculation unit of the information sender event triggering condition judgment module calculates Euclidean norms of difference values of the posterior estimation and the predictive estimation, wherein the Euclidean norms are specifically as follows: wherein: Is the euclidean norm.
And fourthly, a trigger threshold calculation unit of the event trigger condition judgment module calculates a value of a dynamic trigger threshold according to time, specifically, Λ=delta+ρe -σt, wherein Λ is the dynamic trigger threshold, delta is a constant, the value range is 1-10, ρe -σt is a dynamic variable, ρ is a constant, the value range is 1-10, sigma is a dynamic factor, the value range is 0-1, and t is time.
Step five, a trigger condition judging unit of the event trigger condition judging module judges whether a trigger condition gamma k is met according to the Euclidean norm and the dynamic trigger threshold, and sends posterior estimation to an information receiver when the trigger condition is met, specifically:
as shown in fig. 2, when δ=3, ρ=2, and σ=1, the time-dependent diagram is shown.
Step six, a relative observation acquisition unit of the information receiver collaborative navigation filtering module acquires relative observation between an information sender and the information receiver, specifically: representing a relative observation at the moment k, Representing a measurement matrix of relative observations about the status of the sender of the information,Representing a measurement matrix of relative observations about the status of the information receiver,Representing the measurement noise and obeying zero-mean Gaussian distribution, the noise covariance is
Step seven, an event trigger estimation unit of the collaborative navigation filtering module judges the value of a trigger condition gamma k according to whether information is received or not, and estimates the state of an information sender, specifically: wherein the superscript 1, e denotes the time-triggered estimation, An event trigger estimate representing the sender of the information,Representing event-triggered estimation covariance, when the information receiver receives the information, then Otherwise γ k =0.
Step eight, updating posterior estimation of an information receiver by a filtering unit of the collaborative navigation filtering module according to event trigger estimation and relative observation, wherein the method specifically comprises the following steps: wherein the relative observation is Representing a relative observation at the moment k,Representing a measurement matrix of relative observations about the status of the sender of the information,Representing a measurement matrix of relative observations about the status of the information receiver,Representing the measurement noise and obeying zero-mean Gaussian distribution, the noise covariance is Representing the updated information receiver state estimate of the collaborative navigation filtering,Representing the corresponding covariance.
As shown in fig. 3, through simulation experiments of double unmanned aerial vehicle formation, the method is operated by using the simulation parameters shown in table 2 under the sensor configuration shown in table 1 by using the periodic filtering and the static event triggering filtering method as a comparison, through the simulation experiments, the obtained collaborative navigation filtering result is shown in fig. 4, and the communication times of different filtering methods are shown in table 3.
TABLE 1
| Sensor configuration parameters |
Value of |
| Positioning noise standard deviation (m) of information sender satellite navigation receiver |
[3,3] |
| Information receiver satellite navigation receiver positioning noise standard deviation (m) |
[6,6] |
| Visual sensor azimuth measurement noise standard deviation (deg) |
1 |
| Ultra-wideband ranging noise standard deviation (m) |
1 |
TABLE 2
TABLE 3 Table 3
| Filtering method |
Number of communications |
| Periodic filtering |
100 |
| Static event triggered filtering |
33 |
| Collaborative navigation filtering based on dynamic event trigger conditions |
23 |
As shown in Table 3, compared with the periodic filtering method and the static event triggering filtering method, the collaborative navigation communication frequency can be greatly reduced, and the navigation performance is basically consistent.
Compared with the prior art, the method has the advantages that the selective communication is carried out through the dynamic event triggering condition, the collaborative navigation communication frequency can be greatly reduced, the adaptability of the system to dynamic scenes is enhanced, and the seventh step and the eighth step are realized through the event triggering estimation and the collaborative navigation filtering algorithm, and when the event triggering condition is not met, the relative observation is fused through the event triggering estimation, so that the collaborative navigation performance can be ensured not to be obviously reduced due to the reduction of the communication frequency.
The foregoing embodiments may be partially modified in numerous ways by those skilled in the art without departing from the principles and spirit of the invention, the scope of which is defined in the claims and not by the foregoing embodiments, and all such implementations are within the scope of the invention.