Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/003—Bistatic radar systems; Multistatic radar systems
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/66—Radar-tracking systems; Analogous systems
  • G01S13/72—Radar-tracking systems; Analogous systems for two-dimensional tracking, e.g. combination of angle and range tracking, track-while-scan radar
  • G01S13/723—Radar-tracking systems; Analogous systems for two-dimensional tracking, e.g. combination of angle and range tracking, track-while-scan radar by using numerical data
  • G01S13/726—Multiple target tracking
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar

Definitions

• Tracking method associating a passive radar with other sensors
• the invention relates to the general field of radar tracking and the fusion of the detection information produced by several sensors of different natures. It concerns in particular the improvement of the tracking capabilities of a passive radar (RP) through the use of tracking information from external sensors (active radars for example).
• RP passive radar
• Multi-radar or more generally multi-sensor data fusion strategies rely on a fusion of the detection information developed by each sensor, in a Cartesian coordinate system common to all of these sensors. In principle, these strategies do not take into account the bistatic nature of the measurements provided when one of these sensors is a passive radar. They therefore correspond to sub-optimum melting solutions for this type of sensor.
• the fusion of the information delivered by different sensors can be achieved either at the level of the elementary detections (merging of pads), or at the level of the tracking (fusion of tracks). It is known that the first of these strategies is the one that ensures the best performance at the cost of greater complexity than the second. Moreover, since for a passive radar system to be able to deliver consistent Cartesian tracks (that is, sufficiently relevant to be able to be merged with data from other sensors), it is necessary that the detected targets are simultaneously on many of the bistatic bases that constitute its configuration (ideally at least three bases), a track fusion type approach may be penalizing.
• the present invention aims to define a merger scheme that makes the best use of the internal architecture of the tracking of a passive radar to incorporate exogenous information (from other sensors) that can improve the quality of tracking and / or speed up the run.
• An object of the invention is to propose a solution making it possible, in the most efficient manner possible, to merge multi-sensor data, in the particular case where one of the sensors is a passive radar system. In other words, the object of the invention is to improve the restitution of an air situation by fusing at best the detections of the targets coming from a passive radar and those coming from other sensors.
• the invention relates to a data processing system for performing the fusion of the detection information developed by a passive radar system with detection information from an external sensor, the passive radar system comprising a set of bases. bistatic, each bistatic base being defined by a receiver and an opportunity transmitter, the transmitter having several transmission channels to which reception channels correspond in the receiver, the receiver developing a bistatic pad, or bistatic pad RP, for each detection carried out for a given channel, and transmitting these pads to the system, the bistatic pads RP transmitted being grouped according to the channel in which the corresponding detection has been performed, the external sensor transmitting to the system chained blocks over time, forming external tracks or SE tracks, assigned an identifier.
• the process according to the invention comprises at least:
• first tracking means SE for transforming each pad SE delivered by the external sensor into a set of bistatic pads synchronized on the measurement times of the passive radar RP, or bistatic pads SE, each bistatic pad SE being associated with a given bistatic base. , and in a Cartesian plot SE;
• fusion means for producing, for each of the bistatic bases considered, the fusion of the RP bistatic pads prepared for the different channels relating to this base and bistatic pads SE associated with this base to form merged pads, a merged pad being assigned a set of attributes determined by the nature of the bistatic pads RP and / or SE, merged to form the pad considered;
• second tracking means for producing, for each bistatic base, bistatic tracks of different types by time chaining of merged blocks, a bistatic track being assigned a set of attributes determined by the nature of the last merged pad dated who has been associated with him; the merged pads used to form a bistatic track being assigned an attribute indicating that they have been used for this purpose.
• Cartesian tracking means for developing, for all the bistatic bases formed from the same receiver, RP or RP + SE Cartesian tracks, and Cartesian tracks SE, these Cartesian tracks being produced from the merged blocks.
• RP produced by the second bistatic tracking means and Cartesian pads SE produced by the first tracking means SE, a Cartesian track being assigned a set of attributes determined by the nature of the pads, merged pads RP and / or RP + SE and SE Cartesian blocks, which contribute to its formation and maintenance.
• the tracking means SE are configured to transform each pad SE delivered by the external sensor into a set of bistatic pads, or bistatic pads SE, synchronized with the instants of measurements.
• passive radar RP the coordinates of each bistatic stud SE being obtained by projection of the coordinates associated with the stud SE considered in the coordinate system associated with the considered bistatic base.
• the means for performing the tracking SE are further configured to form, from the studs developed by the external sensor, Cartesian pads SE whose attributes are defined relative to at a given Cartesian coordinate system, each Cartesian plot SE being assigned the identifier of the track SE to which the block SE at the origin of the Cartesian plot SE considered contributed.
• the melting means produce and transmit to the bistatic tracking means, fused bistatic pads divided into three categories:
• the merged pads RP constituted only from bistatic pads RP produced from each channel of the radar system, the attributes of each merged plot RP being determined from the attributes of the bistatic pads RP which gave rise to it;
• the merged RP + SE blocks constituted from RP bistatic blocks and a bistatic block SE, the attributes of each merged plot RP + SE being determined from the attributes of the bistatic pads RP and SE having given rise to it;
• the bistatic tracking means are configured to develop bistatic tracks divided into two categories:
• each bistatic track RP being constituted by all the merged pads RP used to initialize and maintain it;
• each bistatic track RP + SE being constituted by the set of merged + SE pads used to initialize and maintain.
• the bistatic tracking means is also configured to identify unused merged pads for developing the bistatic tracks.
• the Cartesian tracking means comprise:
• the means for maintaining the RP and RP + SE Cartesian tracks already formed comprise means that merge the tracks of the RP and RP + SE tracks already formed and the new tracks RP and RP + SE provided by the initialization means.
• the Cartesian tracks are assigned a Cartesian identifier
• the Cartesian tracking means comprise means which assign an identifier to each new initialized Cartesian track and which manage, over time, the list of identifiers already allocated by reassigning them. identifiers assigned to eliminated tracks to new initialized tracks.
• the Cartesian tracking means further comprise means for testing the consistency of the formed RP + SE Cartesian paths, these means determining the likelihood of the associations made and delivering three groups of tracks. :
• the consistency test consists of comparing the current position associated with the track RP + SE considered and the result of a location operation performed from the bistatic distances of the merged blocks RP associated with this track. .
• FIG. 1 a block diagram showing the arrangement of the various means constituting the system according to the invention, as well as the data exchanged by the various means;
• FIG. 2 a block diagram presenting the data exchanged by the means charged with tracking the pads transmitted to the system by an external sensor
• FIG. 3 a block diagram describing the different processing implemented by the means responsible for tracking pads transmitted to the system by an external sensor;
• FIG. 4 a block diagram showing the data exchanged by the means responsible for merging the bistatic pads originating from the different channels of the same bistatic base, and the means responsible for performing a bistatic tracking from these merged bistatic pads;
• FIG. 5 a block diagram describing the different processes implemented by the means responsible for constituting Cartesian tracks from the merged bistatic pads and formed bistatic tracks.
• a surveillance system taken as a non-limiting example, comprising a passive radar, (RP, or PCL according to the acronym of the English name " Passive Coherent Locator "), consisting of a receiver and operating multiple opportunity transmitters and a complementary sensor, or external sensor (SE).
• RP passive radar
• SE complementary sensor
• ADSB Automatic Dependent Surveillance Broadcast
• a primary radar a secondary radar
• a lidar for example, configured to deliver tracks in a standard geographic reference of the "World Geodetic Revision 1984" or WGS84 ("World Geodetic System 1984”.
• each opportunity transmitter transmits signals on several frequency channels each channel corresponding to a defined frequency band.
• the passive radar system, RP composed of a single receiver, is associated with a single external sensor.
• RP passive radar system
• the scope of the invention is therefore not limited to the generic structure presented by way of example.
• the system according to the invention 11 comprises several treatment channels 12 each comprising means for melting bistatic pads 13 and bistatic tracking means 14. Each of the treatment channels 12 delivers the results of the treatment.
• Cartesian tracking means whose role is to build and maintain Cartesian tracks from the bistatic merged pads produced by each of the processing channels.
• these Cartesian tracks are defined in a common Cartesian frame, a marker centered on the position of the receiver of the passive radar system RP for example.
• the different functions performed by the different processing channels as well as those performed by the Cartesian tracking means can be performed by any known appropriate processing method. Also, the detailed operation of the different means is not described here. On the other hand, we are interested here in the structure and format characteristics of the data produced by each implemented means, structure and format that represent essential characteristics to allow the implementation of the architecture according to the invention.
• the system 1 1 is generally configured to process the data provided by the passive radar system RP in the form of bistatic pads.
• the bistatic pads originating from the same bistatic base that is to say having as origin the result of the signal processing of a frequency channel belonging to the bistatic base, are here treated by the same treatment channel 12.
• the system according to the invention comprises as many processing channels 12 as the radar system RP liability involves opportunity issuers.
• the opportunity transmitter transmitting on different frequency channels the receiver comprises a plurality of reception channels capable of producing bistatic pads. Consequently, each processing channel 12 according to the invention comprises, as illustrated in the figure, a plurality of input channels 17 from which the means 13 for melting the bistatic pads perform the melting operation.
• the system according to the invention is also configured to take into account in each processing channel 12 the detection information produced by an external sensor, 1 1 1 (SE).
• This detection information is here supposed to be transmitted to the system in the form of defined tracks, either in a proper reference system, or in a geographical reference point for example.
• Each track is formed of a temporal sequence of pads produced by the external sensor and assigned an identifier.
• it comprises means 16 for formatting the information transmitted by the external sensor so as to constitute in particular bistatic pads whose attributes are relative to the different bistatic bases of the passive radar system RP.
• the pads thus formed form at each of the processing channels a complementary input channel 18 separate from the radar channels 17.
• FIGS 2 and 3 illustrate the operating principle of the means 16 responsible for conditioning the data delivered to the system 1 1 by an external sensor.
• FIG. 2 identifies the characteristics of the inputs / outputs of the means 16 making it possible to trace the pads delivered by the external sensor (SE).
• each track is here formed by the sequence (ie the association, over time) of pads 1 1 1, each pad corresponding to the detection of an object at a given instant.
• Each track is also assigned an identifier, or SE identifier, which is unique to it.
• the pads 1 1 1 formed by the external sensor, or pads SE, and constituting a track are transmitted to the means 16 accompanied by the identifier of the corresponding track.
• the function of the tracking means SE, 16 is to form from each pad SE received bistatic pads whose attributes correspond to the different processing channels 12 implemented.
• This function consists mainly of projecting the attributes of the SE stud considered, position, speed, etc., attributes expressed in a general coordinate reference, the geographical reference WGS84 for example, in the different bistatic bases of the RP radar system.
• An information 21 relating to the configuration of the passive radar RP is for this purpose transmitted to the tracking means SE. This information includes, among other things, the positions of the receiver and the different opportunity transmitters in a Cartesian reference frame.
• the tracking means SE 16 From a single channel for transmitting pads through which the pads SE pass, the tracking means SE 16 thus produce a plurality of channels 18, through which the bistatic pads formed from the pads SE are transmitted to the different channels. 12.
• a stud SE gives rise to M bistatic pads. It should be noted here that according to the invention, the projection of a stud SE in the different bistatic bases can be carried out by any appropriate method.
• the means for SE 16 tracking is able to determine at which moments the bistatic pads must be transmitted to the different treatment channels. This is why the tracking means SE 16 are configured to take into account a date information 22 which serves as a common time reference to the various means constituting the system according to the invention.
• FIG 3 describes in a synoptic manner the different operations performed by the tracking means SE 16, and their sequencing.
• the tracking means SE mainly perform four operations.
• the first operation 31 consists in expressing the attributes of the pads transmitted by the external sensor SE in a common Cartesian reference frame, a marker centered on the phase center of the receiver constituting the passive radar system RP for example.
• the tracking means SE 16 receive, as has been said previously, information 21 on the geographical position of this phase center. This operation produces SE pads whose attributes are expressed no longer in the reference of the external sensor but in the Cartesian reference reference of the passive radar RP.
• the second operation 32 carried out by the tracking means 16 SE consists in forming and maintaining tracks from the SE Cartesian blocks produced by the operation 31, each Cartesian SE block being already assigned the identifier of the initial SE block attaching this last to a track formed by the external sensor.
• the creation and maintenance operation of Cartesian tracks implements a linear filtering, a Kalman filtering for example, whose state model can be a model with constant speed or acceleration, assigned to an average noise defined in such a way that the weight of the measurements is always preponderant with respect to the result of the equations of state.
• the filtering algorithm implemented is chosen so that a prediction of the state of a Cartesian track is produced in the momentary absence of pads that can contribute to the maintenance of this track.
• the operation 32 thus produces Cartesian tracks which are maintained at the rate of appearance of the pads SE transmitted by the external sensor.
• Cartesian SE tracks are assigned identifiers characterizing the SE tracks to which they are attached, the creation and maintenance of Cartesian SE tracks are simplified. Indeed the maintenance of a given track can be generally achieved by considering only the pads that have the same identifier, the pads associated with other identifiers being a priori for the maintenance of other SE Cartesian tracks.
• a Cartesian SE track is also materialized, in the usual way, by the list of SE Cartesian points associated with it, this list being enriched over the time, that is to say the rate at which the pads SE are transmitted by the external sensor.
• the third operation 33 aims to establish a synchronization of the detection information constituted by the pads SE transmitted by the external sensor and detection information constituted by the bistatic pads transmitted by the receiver of the passive radar system RP.
• the passive radar system produces bistatic pads with a rate defined by its own operation. The same goes for the external sensor. Therefore, a synchronization is necessary otherwise the merging operation could lead to the merging of non-contemporary pads and the formation of erroneous bistatic tracks.
• synchronization is achieved by taking the passive radar system RP as a reference.
• the synchronous Cartesian SE pads thus produced are used by the tracking means SE to develop bistatic SE pads, as has been said previously. Moreover, they are also time-chained to form Cartesian SE tracks as shown in Figure 3.
• the fourth operation 34 consists of realizing the projection proper Cartesian SE pads in different bistatic bases and deliver synchronous bistatic SE pads bistatic RP pads. This projection concerns both the mean values and the uncertainties of Cartesian SE attributes.
• bistatic SE pads transmitted to the different bistatic treatment channels 12 are characterized by different attributes such as, for example, the bistatic distance and velocity, as well as the azimuth, the values of these attributes being each affected by an uncertainty.
• each bistatic SE pad is characterized by the identifier of the track SE which gave it birth.
• FIG. 4 which describes the signals exchanged by the means 13 and 14 constituting each of the bistatic treatment channels 12 according to the invention. It also describes the input / output signals exchanged with the other means.
• each channel 12 is dedicated to a given transmitter forming a bistatic base of the passive radar system RP. It comprises means 13 configured to perform the fusion of the bistatic pads 17 of all origins (RP passive radar or external sensor SE) between them.
• the fusion of the bistatic pads can be carried out by any known method of melting pads.
• this method must be implemented in order to produce three groups of distinct merged blocks:
• the radar merged pads, or merged pads RP, produced by the melting means 13 are characterized by attributes of the same nature as the attributes characterizing the bistatic RP pads which have been merged. These attributes are typically the bistatic distance, the bistatic velocity and the azimuth. Each of these attributes is associated with a precision (standard deviation of the measurement).
• the merged RP + SE blocks are characterized by three types of attributes:
• a bistatic treatment channel also comprises means 14 for performing a multi-purpose bistatic tracking consisting mainly of forming and maintaining bistatic tracks from the merged pads RP, RP + SE and SE formed by the means of FIG. fusion 13
• the formation and maintenance of bistatic tracks by the bistatic tracking means 14 may be carried out using any appropriate known method, but this method must be implemented so as to define three groups of separate bistatic tracks:
• Each track being materialized by a structure corresponding to the estimation, over time, of the bistatic parameters of the target it represents, this structure containing:
• Cartesian identifier typically a number of the track, assigned to the track at its creation (by the means 55 or 54), a vector representing the state of the track at the current time,
• the plot RP, RP + SE or SE used to update the track at the current time the identifier SE if the track has been updated with a merged plot of RP + SE type or by a bistatic stud of type SE,
• the nature of a track is fixed by the nature of the last type of bistatic stud which served to update it.
• the bistatic tracking means 14 and realize the grouping of the pads in various categories, each pad being identified by the category to which it belongs, merged pads RP 1 12 having contributed to the formation of bistatic tracks RP, pads SE bistatic 1 15 having contributed to the formation of a bistatic track SE, merged blocks RP + SE 1 13 having contributed to the formation of bistatic tracks RP + SE, or merged blocks RP 1 14 having contributed to form no track bistatic.
• the pads thus identified are transmitted, as shown in FIG. 1 to the Cartesian tracking means 15. All the pads contributing to bistatic tracks are transmitted together with the identifier of this track.
• Figure 5 shows a block diagram of the various operations performed by the Cartesian tracking means.
• the main function of these means consists, overall, in forming and maintaining tracks referenced in a general Cartesian reference, or Cartesian tracks.
• These tracks are formed from the bistatic tracks formed by the various channels 12 which constitute the system, from the bistatic pads not used to form these bistatic tracks and from the Cartesian tracks SE produced by the tracking means 16 SE.
• the Cartesian tracking means comprise two processing chains whose function is to form and maintaining RP Cartesian tracks and Cartesian RP + SE tracks on the one hand and Cartesian SE tracks on the other hand.
• the Cartesian tracking means are mainly configured to form and maintain Cartesian tracks. This function is first ensured by developing and maintaining Cartesian tracks, then realizing when possible the fusion of formed tracks. The result is the formation of merged tracks that can be classified into three groups:
• the RP Cartesian tracks are initialized, maintained and managed by means 54, 51 and 52, from the plots-tracks associations made by association means 53.
• the Cartesian tracks SE and RP + SE are initialized. by means 55, from plots-tracks associations made by association means 53.
• the plots-tracks association means can implement known association methods that are not detailed here. However, these methods are implemented so as to take into account the different types of tracks formed and to minimize track interruptions including ensuring transitions between the different types of tracks, a Cartesian track RP + SE can for example to a moment turn into a Cartesian RP or SE track.
• association depend in particular on the types of blocks and tracks that one associates with a given moment.
• association concerns SE pads and SE Cartesian tracks only, the association can be simply performed on the basis of the identifier of the track SE produced by the external sensor, or SE identifier, a bistatic stud. SE being associated with an existing Cartesian track SE when this identifier is the same for the bistatic SE pad and the Cartesian track SE that we want to associate.
• a first step consists in attempting and realizing, by solving potential plots-tracks association conflicts, when possible, the association of the merged bistatic blocks 1 12 to 1 15, and Cartesian tracks of the same type, the bistatic pads RP, 1 12 and 1 14, with the Cartesian RP tracks, the bistatic pads RP + SE, 1 13, with the Cartesian RP + SE tracks, and the pads SE, 1 or 15, with the Cartesian tracks SE .
• a second step is to try and achieve, when possible, by resolving any conflicts, the association of free tracks (that is to say, not associated with pads) with free pads of different types.
• the first association step is performed by first discarding from any association the Cartesian pads SE already associated with tracks RP + SE. Then we perform the following three association operations:
• the first association step can be carried out with conventional association algorithms pads / tracks.
• the second association step consists in making cross associations free tracks-free pads between different types. These associations implement the following operations:
• association-free RP + SE cartesian paths have identifiers SE which correspond to the identifiers SE of free SE bistable blocks.
• the free RP + SE Cartesian track is requalified in Cartesian track SE without its Cartesian identifier changing.
• the bistatic pad SE which is associated with the new track SE is removed from the list of free bistatic pads SE.
• the association means 53 thus deliver, as illustrated in FIG. 5, in addition to updated Cartesian tracks, unmodified Cartesian tracks as well as merged free pins of any association which contribute to creating the group 1 19 of the non-associated RP fused pads, the latter serving for example in configurations of the invention where the passive radar RP is multi-receivers, for receptor receiver combinations.
• the merged plots RP + SE and the association-free SE bistatic pads are transferred to means 55 loaded with the initialization of new tracks, Cartesian tracks RP + SE or Cartesian tracks SE, while the merged pads RP are transferred to means 54 responsible for the initialization of new Cartesian radar tracks.
• the initialization methods implemented, known elsewhere, are not described here.
• the initialization means 55 create new Cartesian tracks RP + SE or SE for each free pad transmitted.
• the initialization of the state vector of the track RP + SE or SE thus formed is carried out directly by copying the information of the Cartesian plot 19, produced by the module 16, having the same identifier SE.
• the Cartesian RP tracks as well as the Cartesian RP + SE tracks are transmitted to means 51 1 whose role consists in checking the consistency of the tracks RP + SE, ie the merits of the association. studs and tracks.
• This verification is performed by comparing the current position associated with the track in question and the result of a location operation performed from the bistatic distances of the merged pads RP associated with the track.
• the location is realized in considering the distances associated with the RP bistatic pads involved in updating the track in question. Consequently, if the location made from these pads is judged to be compatible with the position associated with the track, the external sensor and the radar system are considered to deliver concordant measurements and the associations are validated.
• the means 51 1 perform an analysis to determine if some of the studs considered are erroneous (ie badly associated). As a result if some blocks appear as erroneous, they are excluded from all the pads to associate with the track in question. Moreover, if all RP bistatic pads are considered erroneous, the considered RP + SE cartesian track is transformed into a Cartesian track SE and if possible into a Cartesian track RP. Only one of the two Cartesian tracks RP and SE thus formed retains the Cartesian identifier of the RP + SE Cartesian track dismantled:
• RP + ES were derived from at least three different bistatic bases, and if the bistatic distances associated with the RP pads that contributed to the track lead to the initialization of a correct RP Cartesian track, this one takes up the identifier of the RP + Cartesian track. SE dismantled.
• the identifier of the dismantled RP + SE Cartesian track is taken up by the Cartesian track SE.
• Cartesian tracks SE are in turn maintained by means 56, the function of which consists in updating the state vector, and the associated covariance matrix, of each Cartesian track SE before proceeding with a merger 53 with pads. newly transmitted.
• the maintenance of the track is advantageously simple, the state vector being constructed by simply copying the most recent associated Cartesian SE blocks transmitted in the stream 19.
• Cartesian tracking means also comprise means 57 for realizing, when possible, the merge of the RP Cartesian tracks and the Cartesian RP + SE tracks. This fusion can be carried out according to any known track fusion method.
• the Cartesian tracking means further comprise means 59 for managing the Cartesian identifiers attributed to the different tracks formed.
• each initialized track is assigned a Cartesian identifier, a number for example, which it keeps as long as it remains alive.
• this means transmits to the means 59 the Cartesian identifier of the track declared dead. This identifier is then assigned later to a new track.

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