DE1791093A1 - Device for target tracking for scanning radar systems - Google Patents

Description

Applicant Stuttgart, September 5, 1968 j

Hughes Aircraft Company ^g

Centinela and Teale Street
Culver City, Calif., V.St.A.

Device for target tracking for scanning radar systems

The invention relates to a device for target tracking for scanning Radar systems, with a memory for receiving a "track" called a signal, which the predicted position of a tracked target at a given time represents an arrangement for generating a signal called "recording", which reproduces the position of an object, and an arrangement for correlating the track contained in the memory with that generated with each scan Recording.

The great advances that have been made in the technology of data processing have led to the development of devices that enable target tracking with the aid of scanning radar systems. Be in such systems Similar to conventional radar systems, video signals that depend on exuded Iladar pulses are received from targets, used to determine position

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ORIGINAL

derive information for each target and on a viewing device in front of one Operator. One form of the representation of target information is the panoramic view, which is often referred to as a PPI and in which a target is represented as a marker whose distance from a starting point indicates the distance of the azimuth, whereas the angle between one of the Starting point and the line connecting the marking and a reference line equals the azimuth of the target. In addition to this usual arrangement includes a radar system that enables target tracking while scanning. light, a computer with a relatively large capacity that can keep track of each allows the operator selected target, which is in the range of a scanning movement executing radar antenna, the echo signals from the target catches. In short, after the operator supervising the vision device decides to pursue a target, the target position at a given scan is entered into the memory of the computer. Thereafter, during the following scans, during which video signals are received from the target the position of the target is continuously corrected. According to this, the target tracking is achieved through a continuous correction of the target information, as long as clear and undisturbed, i.e. discrete video signals are received from the target whose position is to be corrected.

In known radar systems that track targets while scanning enable the decision to pursue a specific goal even if the constant correction of the goal is automatic from Computer is made to be entered manually by an operator observing a viewing device. The operator's job is to find the To observe the position of each target shown and according to predetermined criteria, such as changes in the target position and changes in the target speed, to determine which of the goals is sufficiently interesting for a

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Persecution is. Having made the decision to pursue a goal the operator communicates with the computer using known input techniques to initiate automatic target tracking. This initiation process can take three to five sampling times per target after the entry of a target in the area monitored by the radar device when there is a single target. If several targets are in the surveillance at the same time. μ just enter, the time required is increased.

Although some of the known systems work with varying degrees of success, their -

Effectiveness is limited because an operator is responsible for observation and decision-making what is needed is which or which of the goals are to be pursued and then their corrected Must monitor position. However, there is a limit to the number of targets an operator can handle. As a result, the known target tracking systems for scanning radar systems that are used to track a large Number of targets are designed, a large number of operators and vision devices, thereby significantly increasing the manufacturing and operating costs of the system will. Furthermore, the decisions about the pursuit of a goal are because they are hit by the operator are subject to human error which increases with operator fatigue, thereby reducing the overall accuracy of the System when tracking targets and the mean system time during which targets are being tracked can be reduced. Furthermore, the response time of the system When starting target tracking, it depends to a large extent on the number of targets that arrive almost simultaneously at the border of the surveillance area.

The invention is based on the addressed disadvantages of the known To avoid devices for target tracking for abtstende radar systems and exists in that the device of the type described above has a memory

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for taking records, an initiation gate that generates correlation criteria for initiating a chase, and a record correlator which, in the absence of a correlation between the track contained in the memory and the recording, the recorded recording with each compares the record contained in the further memory and delivers signals, which is characteristic of the relative division of the two records to one another are, if one of the stored recordings correlates with the recorded ^ recording, and if there is a correlation to the

correlating stored record and the characteristic of the relative position Responds to signals and delivers a track start signal, and that one Device for writing the track start signal into the track recording Memory is provided for comparison with a subsequent recording.

The invention therefore provides a device for target tracking for scanning Radar systems created in which the decision to initiate target tracking is automatically based on previously automatically determined discrete Position information is taken, which is received and stored in the data processing system Device are stored, which forms part of the inventive device.

As can be seen from the above, the device according to the invention contains as well as the previously known devices an automatic detector, the video signals of each target is converted into target position information, for example target distance and target azimuth, and which are referred to here as "recording". Furthermore, the device according to the invention comprises a tracking computer which comprises a tracking memory and a tracking correlator. The correlator aligns any record received by the automatic detector with corrected targeting generated by the tracking computer are included in the trace memory. These corrected objectives represent

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ÖAD ORIGINAL. /.

present the predicted positions of the pursued goals to a particular one Time as calculated by the tracking computer.

If the record correlates with the corrected position of one of the targets, if it is used by the computer to generate a new corrected objective, which is stored in the tracking memory. If, on the other hand, the received record is not assigned to any of the corrected destinations can, i.e. it does not correlate with any of the objectives and thereby indicates that it if it is not a question of recording one of the objectives already pursued, it will within a chase opening gate compared to records that have been previously entered into a recording memory. If it is found that the received record does not match any of those in the record memory temporarily contained records is related, it is stored in the record for correlation with received during subsequent scans Records kept.

On the other hand, if the received record matches one of the records in correlates with the record memory, it is assumed that the received record and the previously stored record with which a correlation belong to a predictably moving target that is pursuing should be. As a result, the records are transferred to the tracking computer, where they are used to determine the position of the target predict the following samples. As a result, the decision becomes initiation automatically derived from the pursuit of a target.

In addition, any records in the record memory that are not

the
correlate with one of the records, 'during a certain number-vo'

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subsequent samples are received automatically in the recording memory turned off. The reason for deletion is based on the assumption that these records do not belong to already tracked targets because they did not correlate with corrected records from the tracking memory, and neither do they Records of new discrete targets to be pursued are because they do not have any Recordings in subsequent scans could be assigned so that they can only represent volatile signals that are not justified to track. fc Sample-to-sample correlation is an effective method for

Reduction of false targets that are captured during automatic detection or video processing.

Further details and configurations of the invention can be found in the following description refer to, in which the invention is described and explained in more detail with reference to the embodiment shown in the drawing. The the In other embodiments of the invention, features that can be derived from the description and the drawing can be used individually or collectively in any desired manner Combination find application. Show it:

fc Fig. 1 is a block diagram to explain the prior art,

Fig. 2 is a plan view of the screen of a panoramic display device,

Fig. 3 is the block diagram of a device according to the invention, which by the dashed line replaces the bounded area of the device according to FIG. 1,

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FIG. 4 shows the block diagram of one contained in the device according to FIG Correlators and

Fig. 5 is a diagram of a single memory address, the track bits and as Contains sampling bits serving counter.

The simplified block diagram of a known system for target tracking at scanning radar systems of Fig. 1 serves the fundamental Wirkungs- ä

How to explain such a target tracking system and to show the limits of the known systems. In the system shown, it is assumed that a radar transmitter 12 transmits radar pulses with a specific pulse repetition frequency (IFF). A radar receiver 14, which generates a certain level of noise, is used to receive the signals from an antenna 16 which carries out scanning movements and responds to the energy or echoes that are reflected from objects, for example from targets or moving objects, as a result of the irradiation with the emitted radar pulses or stationary clotter. As is known in the art, the received signals are frequently referred to as video signals treated in a unit 18 to the video processing, supplies the output signals in the form of messages or words, i representing the information about the position of targets, or random Clotter and location of energy-reflecting objects and of noise indicate what correlates with the integration of successive samples. It is known that the processing device 18 can contain a buffer memory 18a in which a number of the target messages or words can be stored. The information may be in the form of signals indicating the values of X and Y coordinates or in the form of signals for the distance R and the azimuth θ with respect to an origin, e.g. the location of the receiver, and a reference azimuth θ . In the following, for the purpose of explanation, it is assumed that the information about the target position, which is also referred to as recording in the following, is represented by distance and azimuth signals.

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In the tracking system shown in Fig. 1, the output signals are or records from processing device 18 are fed to a data processing device for target tracking while scanning, in its entirety is designated by 20. The data processing device 20 includes a tracking memory 21, a control unit 22 and a tracking correlator, the Correlation gates 24 are assigned. The task of the data processing Briefly, device 20 consists in tracking one or more targets selected by the operator by means of tracking logic 25 which automatically tracks the Position of each target correlated by the tracking correlator 23 is corrected. The information on the position of each target in the memory 21 becomes general referred to as a track, whereas the positional information received by the processing device 18 before it is assigned to one of the targets being tracked is called a recording will. Each record and track includes signals for distance R and azimuth 0.

If a recording is received and detected at a certain time, that it correlates with signals or one of the tracks contained in memory 21, the recorded data as well as the stored track data are used to correct the target position and to predict the position in the next scan. The correlation is carried out with the aid of correlation gates, the function of which is determined by prediction position data that determine the predicted position of a predict the goals at a given point in time. Briefly, when there is a correlation, the correlator 23 may include range and azimuth difference signals Δ Χ and Δ Y, respectively, provide the differences between the corresponding Signals of the recording and the predicted track coordinates with which correlate the recording signals. These difference signals, which are im hereinafter referred to as AR and Δ θ, are then stored in memory 21, so that in the following they are used together with the correlated trace by the logic for Creation of a corrected objective can be used and thus a further target prediction is possible.

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Since the first development of radar systems that tracked targets during of scanning, various techniques have been developed to optimize target tracking accuracy. Various of these Techniques and related things have been used in some publications described, which are known to the person skilled in the art. An example of such a publication is an essay entitled "Optimizing the Dynamic Parameters of a Track-While-Scan-System "by Jack S. Klansky, RCA Review 1957, Volume 18. Another relevant publication is the Essay ™

"Synthesis of an Optimal Set of Radar Track-While-Scan Smoothing Equations" by TRBenedict and GW Bordner in "IRE Transactions on Automatic Control", 1962. Various technical papers on target tracking with scanning radars were presented at a target tracking symposium which was sponsored by Miter Corporation. These papers were published in the Proceedings of the Miter Tracking Symposium, September 29, 1958. One of the published papers is entitled "Picture of Track-While-Scan-Smoothing" and is by NP Nelson. This article describes the use and function of speed and position smoothing parameters, which are described below with β and <h. are designated.

In these known systems, the decision to pursue a target is made by an operator who observes a viewing and input device 30, although the actual tracking of the selected target with the aid of the data processing device 20 takes place automatically. Such a viewing and input device contains a display device, for example a cathode ray tube with a screen on which the relative positions of the various objects that supply video signals are displayed. Usually, the output signal of the receiver 14, which represents such video signals, the view and

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Input device 30 supplied. In this device, the signals for feeding the Display device used, so that all video signals are supplied by this device Objects are represented. A type of display known as a panoramic display is illustrated in FIG. 2, which is an enlarged top view of the screen 30a. On this screen the position of an object is through the mark X is reproduced. The distance between the marking X and the center 0 of the screen is for the distance and the relative position characteristic of the azimuth of the target with respect to a reference azimuth θ.

It will be understood that each scanned object that provides video signals creates a different mark on the screen. The operator observing the screen notices the changes in position of the various markers and determines which of the markers represent moving targets that may be of interest to track. If the decision is made that a particular label is an interesting target, the operator with the data-processing device is connected to the target tracking initiate. Any known manual input technique can be used here. The manual initiation of tracking is illustrated in FIG. 1 by the line 35 which connects the viewing and input device 30 to the data processing device 20. Essentially, it is necessary to enter the current position and / or speed of the target into the data processing device and to determine the area in which the tracking correlator looks for records which can be assigned to the entered track during the next scanning period of the antenna.

Upon the operator's input, the data processing device saves the original operator recording of the specific destination in memory 21. This recording then forms the data with which the following recordings from the video

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-.11-

Processing device 18 in tracking correlator 23 are compared to determine whether such records are of the particular to be traced Target so that its position can be corrected. As you can read above, it is highly disadvantageous that the selection of the target and the initiation of target tracking must be carried out by an operator because of the Operator can only observe and monitor a limited number of targets in order to decide which of the targets are to be tracked automatically or manually target. As a result, if a larger number of goals are to be pursued |

and monitor is required the use of several operators, one of which each requires its own viewing and input device 30, which reduces the costs and the Complexity of the target tracking system is significantly increased.

Monitoring goals and initiating goal tracking is a very tedious task and time consuming. It was further found that the operator in monitoring areas where for long periods of time There are no goals, it takes a long time to get an emerging goal discover, which significantly reduces the duration of a possible early warning period. As a result, the problems with manual initiation are a big one

Time required, severe fatigue, a low response speed, low λ

Accuracy and high cost associated with the main drawbacks of this solution form.

According to the invention, on the other hand, the pursuit of a target is initiated automatically, so that the task of an operator in viewing the screen 30a is limited to only monitoring the various targets and their Observe changes in posture, which are automatically tracked. Consequently a single operator can monitor a large number of targets being tracked.

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Since each operator can monitor a larger number of targets, requires fewer vision and input devices, which can greatly reduce both the cost and complexity of these target tracking systems, without affecting their tracking capacity or accuracy. In a practical embodiment of the invention, the capacity could be one Operators for target monitoring can be almost doubled. The accuracy of the position input of a target to be tracked was reduced by the deactivation any time delay increased many times over. The response time P of the system has been improved by 1 to 5 minutes, depending on the number of targets

which enter the observation area of the radar device almost simultaneously. Finally, the observation time that an observer could reasonably be expected to observe could be increased because the monitoring task is less tiring than the task of spotting newly emerging targets.

An embodiment of a target tracking system according to the invention during the scan, the block diagram of Fig. 3 illustrates how can be seen, the output signal of the video processing device 18, which represents information or records about the target position, from the buffer memory 18a fed to a data processing device 40, which is " is similar to the data processing device 20 described in that it comprises a tracking memory 21, a control unit 22, a tracking correlator 23, correlation gates 24 and a tracking logic 25. The data processing device however, also includes a recording memory 41, a recording correlator 43 and an introductory gate 44. The function of these components is described in detail below. The control unit 22 is connected to the buffer

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memory 18a, the tracking correlator 23 and the recording correlator connected to supply them with control signals and receive signals from them. Furthermore, the control unit 22 is connected to the correlation gate 24 and the initiation gate 44 connected to control the elective function of these gates. Farther the control unit 22 is connected to the memories 21 and 41 via lines 22a and 22b to allow rewriting of the information in the memory during to control normal rewrite cycles. Finally, the logic also responds to the control unit 25. The memories 21 and 41 each contain a register f

and control logic unit 21a or 41a. The gates 24 and 44 each contain one Gate selection logic 24a or 44a. The tracking correlator 23 includes a register 23a and a subtracter and logic unit 23b. Also contains also the recording correlator 43 has a register 43a and one of subtractors and Logic existing unit 43b.

According to the teachings of the invention, the data processing device 40 works to this extent in the same way as the data processing device 2P as, after receiving a recording (R, Θ) from the video processing device 18, each of the in the tracking memory 21 compared with the recording in the correlator 23 to determine whether the newly received recording corresponds to one of the tracks I. heard. If there is a correlation, the record is from one of the targets being pursued and is used by the logic to determine the location or trace of the particular one To correct the target in the same way as in the data processing device 20.

In the known devices, if a record did not correlate with any of the tracks contained in the trace memory 21, it was deleted. According to the invention

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however, a record becomes identical to none of those contained in the memory 21 Traces led to a correlation, fed to the recording correlator 43, in which they according to the criteria supplied by the initiation gate 44 with all Records contained in the record memory 41 is compared are. If the new record correlates with one of the records contained in the record memory 41, it is stored in the record memory inscribed and temporarily stored therein as a temporary record. The reason for temporarily storing the record in the record memory 41 is based on the assumption that a record, which does not belong to any of the tracks contained in the tracking memory 21, does not come from one of the targets already tracked, but the recording of a new goal to be pursued. Therefore, this recording is temporarily stored in the recording memory 41, so that in the following it can be determined whether this record is related to another record received during the next sample period. the Use this temporary record for an instant correlation is prevented by a time delay which is a fraction of a sampling time, for example half the sampling time.

On the other hand, if the new record stored in the record correlator is compared with one of the temporary ones contained in the recording memory 41 This indicates that the two recordings belong to the same destination. The positive correlation has the effect that the record contained in the record memory 41 and that of the Recording correlator 43 formed difference signals are fed to the tracking logic, so that a starting position or track for a newly discovered Target can be written into the tracking memory 21 so that they can be used in the Correction of subsequent records received during subsequent scans can be used.

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From the foregoing it can be seen that each new record is used, either to correct the positions or traces of targets already being pursued, or to possibly initiate the pursuit of a new target. For this purpose, the new record is compared with the temporary tracks in the record memory 41 to determine whether it forms a record of a new destination along with any of the data contained in the record memory 41 or whether it needs to be written into the record memory 41 in order to do so they during subsequent scans to determine their i

Relationship to a trackable goal can be used. Any transient track in record memory 41 which correlates with any of the records during a certain number of consecutive scans, usually 2.5 scans, is considered to be non-traceable target and as a result is automatically erased in record memory. To improve system accuracy, it is important that a new record correlates multiple times, once in an introductory gate and twice in a tracking gate, before it is accepted as a system track. Any lack of correlation in this sequence, which persists for 2.5 consecutive scans, results in the automatic elimination of the track from further processing. This method of three-fold correlation of consecutive i

Samples prevent any generated by the video processing device 18, records due to noise or accidental clotter can be traced.

The teachings of the invention will now be explained in more detail using a specific example will. Assume that the recording received by the video processing device 18 includes the range and azimuth signals R and d

η η

includes, of which R and θ the distance BSW. the azimuth signal are the Index M indicates that the signals are currently measured, and

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the index η indicates the time η. Suppose further - that one of the 21 contains the signals R and 6, in which

η η

the index P indicates that it is the signal of a predicted position which was determined by the tracking logic 25 on the basis of the previous correlations. If the track removed from the memory with the new recording in the correlator 23 meets the correlation criteria provided by the correlation gate 24, the correlator 23 generates distance and azimuth difference signals, which are denoted in FIG. 3 by Δ R and Δ θ. Here poses

AR the difference between R_, and R ,, and Θ the difference between η PMn

η η

^Θ Ρ Μ

η η

These signals are controlled in the trace memory 21 to an address which associated with the correlated trace (R and θ). Then something becomes one

η η

later point in time at which the tracking logic 25 for arithmetic operations is available, the correlated recording (R and θ) and the development

n η

Distance and azimuth difference signals (Δ R and Δ θ) fed to this logic. These

η η

Signals are then processed into corrected system target signals, the data lines fed w-> rdon. In addition, the tracking logic 25 provides a corrected one Trace represented by the signals R and θ and the

l ml

predicted values for range and azimuth of the specific target at time nl form, i.e. the predicted position for the next scan. This corrects ο Track is then stored in memory 21 for subsequent use at time nl for comparison with a new record that appears in the correct timelessness and positionlessness.

? Ü 9 B 3 Ί / U 1 7 Π

BAD ORiGiNAL

enrolled.

However, if none of the tracks contained in the tracking memory 21 match the Record R, θ correlates, causes the control unit 22 to record

n η
drawing correlator 43 to compare this new record with all records temporarily contained in the record memory 41.

The target message, which is held in the buffer memory 18a, is sent to the

Memory registers 23a and 43a at the beginning of the correlation cycle to the two f

Correlators 23 and 43 transmitted. If there is a correlation in the tracking correlalor 23 is present, then the line 22b blocks the rewrite cycle, so that difference signals are written into the memory 21, which for the formation corrected records are used. Conversely, if in the tracking correlator 23 no correlation is achieved, the control unit 22 is supplied with a signal that sends a signal to the recording correlator 43 for executing a Correlation transmitted. If a record correlation is achieved, then memory 41 and tracking logic 25 via control unit 22 are turned on Signal supplied to cause the transfer of the record from the memory 41 to the trace memory 21. It should be noted that both memories

21 and 41 normally in a read-write or rewrite mode '

work in which the information runs through the associated correlator.

Through the initiation, the trace memory 21 is received from the control unit 22 a signal is sent that causes the word to be written in a suitable memory location. When the recording in the recording correlator 43 leads to no correlation, the recording memory 41 on the line a "record new track" signal is fed to the memory for the uncorrelated Record. When operating the system, a correlation cycle and a correction cycle can be provided alternately. The correlation of the track and

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the recording takes place during the correlation period, whereas the correction, the initiation and entry of new messages into the recording memory 41 take place during the rectification cycle. For the next one Correlation and correction cycle is a new message in the register 23a and 43a of the two correlators 23 and 43 are written over the existing data, so that the old message is effectively deleted. The correlation in the recording correlator 13 takes place according to specific correlation criteria, the can be provided by the initiation gate 44. If none of the records in memory 41 correlates with the new record Ii, θ ■ or if the Recording memory is empty, i.e. no recordings in it,

are stored, the record correlator 43 makes the new record to the recording memory 41 for temporary storage. this fact is illustrated in Fig. 3 by the broken line connecting the correlator 43 and the memory 41 with the dash sequence long-short.

If at a later time a new record IL, θ from the

Video processing device 18 is received, the

Correlation process repeated. Assume that none of the traces in tracking memory 21 is correlated with this new record so that this new record is in turn compared in the record correlator 43 with each of the records temporarily contained in the record memory 41 i.e., with the records R, θ previously written. the

η η

corresponding connection is illustrated in Fig. 3 by the broken line with the line sequence long-short-short. It is assumed that these records correlate with one another, so that the record correlator 43 supplies distance and azimuth difference signals Δ R -, Δ θ. AR ₊ ..

represents the difference between VL and R, while A θ represents the difference between

η n + 1

Θ ,, and ö represents. The difference signals are temporarily

MM

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.A BAD ORIGINAL

Drawing memory 41 stored and at a later time together with the original record of the tracking logic contained in record memory 41 25 supplied. These signals are processed in the tracking logic 25 so that signals can be fed to the tracking memory 21. In a certain sense, these signals represent the first corrected signals of a new target. Furthermore, the tracking logic 25 supplies the tracking memory 21 with an output track for a new target, which is indicated by the signals R

η-2

and θ and the predicted distance signals Λ

n + 2 "

and the predicted azimuth of the new target at a following time η »2 represent. In order to increase the accuracy, the traces are initiated automatically it is desirable to have the corrected signals before they are fed to the data lines and display devices as a system trace new target should be correlated with recordings in subsequent scans to ensure that the new corrected signals from a true goal originate. In one implemented embodiment of the invention had to correlate the corrected signals with recordings made during two subsequent sampling intervals before they were fed to the line as a new target became.

From the above it can be seen that the last-mentioned signals are a new one Show recording for a target to be tracked. These signals won't generated by an operator who with the data processing device 40 educated chasers, but automatically from the Tracking logic 25 depending on the signals from the circuit combination is stored and / or generated, the <Vn recording memory 41, den Record correlator 43 and the introduction ;; - ;; atter 44 includes. So while

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BATH

-20-

in known arrangements, a new recording is discarded if ■

it does not correlate with any of the traces in the tracking memory, according to _;

the invention such a record for correlation with the following new?

'■ i

Records used. If then there is a correlation between these two responses

Drawings are available, they are used to calculate distance and azimuth /

Generate difference signals, which then go along with the first recording
can be used to create an exit track for the new target. Farther
according to the teachings of the invention, each of the temporary records
which are contained in the recording memory 41 are automatically removed from the recording memory 41 if they do not correlate with each of the new recordings during 2.5 sampling periods and thereby indicate that
that she does not belong to a new purpose. Similarly, the first corrected symbols (R _p and θ) are discarded after 0.5 sample periods if

n + 2 n + 2

they do not correlate with recordings during the following two sample intervals.

The recording correlator 43 operates in the same way as the correlator 23

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and generates range and azimuth difference signals when the two pull it- · ί

fe kept records according to the correlation criteria that correlate from the I.

Initiation gate 44 are supplied. The introduction gate 44 works in the same I-

Like the two correlation gates 24 and provides a level for comparison t

the range and azimuth signals fed to the correlator 43 and enables the ■■

Correlator to deliver difference signals if the compared signals are within \

certain values lie, I.

The mode of operation of the recording correlator 43 can be seen on the basis of FIG. 4 explain better. As can be seen from FIG. 4, the correlator comprises two subtractors 50 and 52, which refer to the contents of the message storage register 43a respond, as has been explained with reference to FIG. The subtracter 50, the is referred to as a distance subtracter, speaks to the distance signal,

R of the new recording at time n + 1 and the distance signal R _M of

n + 1 η

current recording from memory 41 to a distance difference signal R. Zu deliver, which is fed to a distance visual wave value circuit 54

will. The latter circuit is also supplied with a signal IG from the initiation gate 44. The signal IG_ represents the distance correlation criterion which is decisive for the correlation of the distance signals. Only when AR _{1 is} not greater than IG_ does the circuit 54 supply an output signal that corresponds to its input signal AR. is equal to. The signal IG is generated in the initiation gate as a function of the permissible range error of the system and the expected maximum speed of the target to be pursued. In a practical embodiment of the invention, IG became equal to + 3 <r Ην -_. At, where oL is the root mean square value of the distance error max R ^

of the system and V the expected maximum speed of each tracking target and At the time between the records to be correlated was. With a hit-to-sample ratio of 1, At is equal to the sample time. It

it was found that by multiplying d ~ by the constant 3 a high ■ Ii

Degree of availability reliability has been reached (Stf failure point).

From Fig. 4 it can also be seen that the distance difference signals such as AR ... are fed to the recording memory 41 only if the difference between the two correlating distance signals is not greater than

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the distance signal supplied by the initiation gate 44. In the same way the subtracter 52 compares the two azimuth signals such as θ and θ

η n + 1

and supplies an azimuth difference signal ÖÖ ,, which the memory 41 via a

n + i

Azimuth threshold circuit 56 is supplied only when the azimuth difference signal is not greater than an azimuth signal IG, which from the input

line gate 44 is supplied. The azimuth correlation signal is

fe V Af 180 '■ * Tr - <i ^ ι. ^max '

where σ is the root mean square of the azimuth error of the system, R the ent- Θ

removal of the special new record being correlated and 180/11 of the Conversion factor from radians to degrees. The subtractors 50 and 52 and the threshold value circuits 54 and 56 can be parts of the subtracter and logic unit 43b form.

From the above it can be seen that the function of the introductory gate 44 is the distance correlation signal IG and the azimuth correlation signal IG. to form which signals are from the root mean square

the system failure and other factors. It is for the average person skilled in the art seen that numerous circuit arrangements as well as special arithmetic circles can be used to generate these two signals according to the equations given above.

The correlation gates contained in the data processing device according to FIG may include one or more gates, each of which is a range correlation signal and provides an azimuth correlation signal. As is known to those skilled in the art, when pursuing a non-maneuvering target, i.e. a

209832/0120 · ^ν \

BATH ORIGINAL

Target that seems to follow a straight path has a stricter correlation used as a maneuvering target. The gates 24 can consequently comprise at least two gates, one of which is described below referred to as a no-maneuver gate and range and azimuth correlation

signals G_ and G _n
.; rv ö

Signals can get through

NM NM "

Provides signals G_ and G _n , in which NM denotes non-maneuvers. The two

, NM.
¹ row

eel k and
R ρ

be expressed. In these expressions, c is a constant and

ρ (4-2X ^ / 3)

The range and azimuth correlation signals of the maneuver gate can can be reproduced by

> ^d

^M - ™ k . JLAt ^{2 /} ß 180

In these equations, M is the designation for a maneuvering gate, c a constant, Λ the calculated acceleration of the target being pursued and / 3 the speed smoothing parameters. Very satisfactory results were obtained when c was equal to the 3 rf error point.
ο ·

to '

* · * ■ ·. The tracking correlator 23 is the same as the recording correlator 43 in that it contains two subtractors in the subtracter and logic unit 23b (FIG. 3), ο ■

· - * around the distance and azimuth difference signals ^ R ^and ΔΑ (Fig. 3) only then η η

O to be supplied if they do not have the corresponding correlation signals from gate 24 exceed. The correlator 23 interacts with the register 23a in the form shown in FIG described way together. If there is a correlation only in the maneuvering gate

· "■., - ^> BADOBiGINAL

takes place, this fact is communicated to the control unit 22 by the tracking correlator 23 to indicate that the tracked target is maneuvering. The control unit 22. marks a bit in the data word (Fig. 5) which is in the register and Control unit 21a is stored. The information given in this way is used by the Control smoothing system used, the general technique of correlating incoming records with each one in tracking memory 21 stored track in maneuver and non-maneuver gates is «« the same as the technology, as known from known tracking systems for scanning radar systems is. Likewise, the operations performed by the tracking logic 25 are known. In short, the logic contains circuitry that acts on the stored Tracks and the range and azimuth difference signals respond to the target position to correct and provide a new trace that the predicted objective represents. According to the explanations in the article "Investigation of a Double Integrator, Digital Tracker Used in a Track-While-Scan System "by H. Poritsky et al., Published on page 45 of the aforementioned Proceedings the tracking process can be described by the following equations:

X = Χ _π - X (X „- X. = Χ _π / 4X
η PP mn) P η

η η 'η

χ_ = χ + χ τ,

P- η η
η + 1

20983 2/0120

in which

X .. - the smoothed X position coordinate at sampling time n,

X - the predicted X position coordinate at sample time n,

X - the measured X position coordinate at the sampling time η,

X - the X component of the speed at sampling time n,

X ■ - the X component of the speed at sampling time n-1, n-1

X - the predicted X position coordinate at sample time n + 1,

n + 1

- the time between scans producing hits,

■ - the sampling time of the receiving organ of the system, in the following

also referred to as T,
scan

- the position smoothing parameter and

- mean the speed smoothing parameter.

If the hit-to-sample ratio is 1, then ^ t = T. Likewise, the Smoothed Y position coordinate at sampling time n, d. H. Y, and the predicted Y position coordinate at sampling time n + 1 using a similar set of equations Are defined. Since it was assumed in the foregoing description that the tracking logic 25 is supplied with range and azimuth position signals R and θ , these signals must be converted into X and Y coordinates before the

209832/0120

above equations can be calculated. Likewise, after determining

of X and Y, i.e. the predicted X and Y coordinates of the target n + 1 n + 1

at time n + 1, these signals into the predicted range and azimuth signals

R and θ are converted.
n + 1 n + 1

The preceding description makes it clear that the mode of action of the inventive System can also be described by a sequence of operation commands of the type that are generally supplied to a computer, to effect the automatic initiation of target tracking and a technique to automatically eliminate unwanted recordings and track beginnings due to clotter or noise.

An example of a sequence of operation commands is given below for the purpose given for explanation. It goes without saying that additional commands are introduced and changes in the sequence can be made without departing from the scope of the invention. When a new recording is received, the following Computer commands can be provided:

1. Generate correlation gates for each stored track and record.

2. Scan the trace memory by reading out each one in turn Track.

209832/0120

3. Correlation of each track with the new record.

4. If there is a correlation with a trace, failure of the smallest gate correlation.

5. If there is no correlation, create a track lead-in gate.

6. Scanning the recording memory by reading out sequentially | the temporary records stored therein.

7. Correlate each temporary record with the new record.

8. If there is a correlation, store the difference signals in the recording memory.

9. Transmission of correlated transient records and differential signals to tracking logic.

0. Creation of the beginning of a track. *

11. Save the beginning of the track in the tracking memory. .

12. If there is no correlation, store the recording in the recording memory for correlation at the following sampling intervals.

13. Repeat operations 1 to 4 during two correlation cycles and the Formation of tracking signals for forwarding on data lines and to display devices.

209832/0120 ./·

As stated above, a new trail must be created before going to one indicating a new destination System trace collected will correlate with recordings in two subsequent scans. This measure is desirable to prevent that volatile noise signals are interpreted as a target. When the new track does not correlate with the records in two subsequent scans, it is deleted from the trace memory 21. To this end, everyone can trace sampling time units are assigned in the memory, which are used as counters which is reset every time the trace is corrected. Another-

* On the other hand, the counter reading is increased if the track does not start with a subsequent recording correlated. When the counter reaches a certain value such as 2, it indicates that the track has two consecutive records has not been correlated and must therefore be deleted. Fig. 5 illustrates a track and its associated counter in a memory address, namely the track bits 70 and the sampling bits 71 serving as counters. It is understood that various Logical circuitry can be used to clear the track bits when it is determined that the track does not contain two subsequent records correlated. Likewise, each temporary recording in the recording memory 41 (FIG. 3) can also be provided with sampling bits, so that if the temporary recording does not start with an input recording during 2,

^ - Correlated sampling intervals, as described above, is deleted in the recording memory.

Although it was previously believed that the new record was distance and Azimuth signals R and θ, respectively, which are compared with each track in the tracking memory or with each temporary record in the recording memory 41 the new record may contain other signals, for example signals representing a selective identification code. Furthermore, everyone can

209832/0120

Track and each recording in memory 21 or 41 include such signals, which are useful for further differentiating between goals being pursued and better associating new records with the correct goal enable. Such code signals have proven particularly useful in those cases in which a new recording with the tracks of different Targets are correlated so that the code signals enable the determination to which of the destinations the new recording is assigned.

Furthermore, the system can be operated to allow the use of a prevents new recordings to correct the position of each target pursued, if the record correlates with more than one track and it is not possible to determine which of the tracks needs to be corrected. This situation can occur when targets are in close proximity and there is no identification code is used to distinguish the goals. Therefore a new record is better eliminated than to correct the position of one used with the wrong aim. The technique of associating identifying code signals with tracked targets and the problems of differentiating between densely neighboring targets are in radar technology and their special application well known in tracking targets while scanning. ^

The foregoing makes it clear that the invention does not the illustrated embodiment of a device for automatic initiation target tracking is limited in scanning radar systems, but numerous and varied changes are possible without departing from the scope of the invention to leave.

2098 3 27 0 120 _BA D

Claims (5)

PATENT CLAIMS 1. Device for target tracking for scanning radar systems, with a Memory for recording a signal called "track" which represents the predicted position of a tracked target at a specific time, an arrangement for generating a signal called "recording" which Ik represents the position of an object, and an arrangement for correlation the track contained in the memory with the recording made with each scan, characterized in that it has a memory (41) for receiving records, an introductory gate (44), the correlation criteria generated to initiate tracking, and a record correlator (43) has, which in the absence of a correlation between that contained in the memory (21) Track and record the incoming record with each compares the records contained in the further memory (41) and supplies signals (AR, Aß ^, which are used for the relative position of the two records are characteristic of each other if one of the stored records correlates with the incoming recording, and continues with * Presence of a correlation on the correlating stored record (R, θ) and the signals characteristic of the relative position CdR ^ ₁ »MM n + i η η Λθ) responds and supplies a track start signal, and that a device n + 1 (25) for writing the track start signal into the track recording Memory (21) is provided for comparison with a subsequent recording. 209832/0120 2. Device according to claim 1, characterized in that the device (25) the track start signal automatically to write the track start signal switches off if the track start signal does not correlate with any of the recordings, which are received during a certain time interval. 3. Device according to claims 1 and 2, characterized in that the Time interval is greater than twice the sampling time. 4. Device according to one of the preceding claims, characterized in that " net that the further memory (41) is provided with an arrangement for deleting the written records that were made during a certain Do not correlate the time interval with an incoming recording. 5. The device according to claim 4, characterized in that the time interval is greater than twice the sampling time. 209832 / 012G Blank page