EP0415587B1 - Early warning tracking system - Google Patents

Early warning tracking system Download PDF

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Publication number
EP0415587B1
EP0415587B1 EP19900308833 EP90308833A EP0415587B1 EP 0415587 B1 EP0415587 B1 EP 0415587B1 EP 19900308833 EP19900308833 EP 19900308833 EP 90308833 A EP90308833 A EP 90308833A EP 0415587 B1 EP0415587 B1 EP 0415587B1
Authority
EP
European Patent Office
Prior art keywords
predefined
height
plane
zone
intrusion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19900308833
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German (de)
English (en)
French (fr)
Other versions
EP0415587A3 (en
EP0415587A2 (en
Inventor
Patrick R. Williams
Mark J. Rentmeesters
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Co
Original Assignee
Hughes Aircraft Co
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Filing date
Publication date
Application filed by Hughes Aircraft Co filed Critical Hughes Aircraft Co
Publication of EP0415587A2 publication Critical patent/EP0415587A2/en
Publication of EP0415587A3 publication Critical patent/EP0415587A3/en
Application granted granted Critical
Publication of EP0415587B1 publication Critical patent/EP0415587B1/en
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G5/00—Traffic control systems for aircraft, e.g. air-traffic control [ATC]
    • G08G5/0073—Surveillance aids
    • G08G5/0082—Surveillance aids for monitoring traffic from a ground station

Definitions

  • This invention relates generally to computerized methods to provide early warning of collision for a tracking system and pertains more particularly to a process for predicting the probability that an object being tracked will intrude into a predefined polygonal zone.
  • a variety of computerized systems have been developed that are capable of predicting if and when an approaching object will intrude into a predefined region of space. Such systems are typically employed to protect secure zones, such as, for example military installations, to enable appropriate counter measures to be invoked on a timely basis. In addition, these systems are employed in air traffic control systems to assist air traffic controllers in discerning which amongst a potentially large number of objects being tracked are likely to present the possibility of a collision with the ground, restricted airspace or off designated air routes.
  • Performance of previous systems especially those with relatively simple tracking and collision prediction algorithms, often is limited in that in order to solve the probabilities presented by modern vehicle performance envelopes and a relatively large number of closely spaced vehicles being tracked, large amounts of calculations are performed for too many of the objects being tracked. Since the data processing resources available are generally limited, this naturally serves to limit the number of objects such systems can process and increases the probability that false alarms of intrusion or collision will increase, especially when the objects are moving at high speeds, or are capable of rapid and unpredicted changes in path. All of these limitations are exacerbated by uncertainties in the positon or velocities of the vehicle being tracked.
  • a significant aspect of the shortcomings of some prior art systems is the manner in which the uncertainty of positional determinations and velocity vector determinations are accommodated in the calculations.
  • buffer zones are placed both inside and outside the predefined polygonal region to be protected to take into consideration the probable extent of potential tracking errors. If a tracked object is predicted to pierce the inside zone, then a sure lateral intrusion is declared. If, on the other hand, a tracked object is predicted not to pierce the outside zone, then a sure non-intrusion is declared. An unsure intrusion is declared if the object is predicted to penetrate somewhere between the peripheries of the inside and outside buffer zones. The problem with this method is determining the actual boundaries of the buffer zones. An accurate construction of the zones based on track variances has proved intractable. Not only do such systems have trouble accommodating large numbers of objects, especially ones moving at high velocities, but often false alarms and undetected intrusions result.
  • the general purpose of the invention is to provide an early warning tracking system that is quickly able to discern whether an approaching object will intrude into a predefined polygonal zone.
  • the present invention first projects an uncertainty region in the instantaneous direction of travel of each approaching object and then makes decisions regarding the potential for intrusion, depending on the location of the predefined polygonal zone and its relationship to the location of the uncertainty region.
  • the coordinate system is reoriented along the velocity vector for each approaching object.
  • the new coordinates of the periphery of the predefined polygonal zone resulting from the reorientation are then considered with respect to the uncertainty region of each approaching object.
  • the limits of the uncertainty regions are determined by the variances associated with the positional and dynamic determinations of the objects being tracked.
  • the potential for intrusion is first considered in two dimensions to simplify processing. If no lateral intrusion is indicated, no further consideration is given to that particular object. Only after a possible lateral intrusion is indicated, is the object's perceived height and rate of change of height considered to further determine whether an intrusion into the predefined polygonal zone is probable.
  • Fig. 1 generally illustrates the situation and conditions for which the deployment of the system and methods of the present invention are intended.
  • Schematically illustrated in a top plan view is the airspace in and around a predefined polygonal region 61 (having vertices 69-74) in which a multitude of objects are moving at different speeds and directions. Each such object's position is depicted by a dot 63 while its velocity vector, depicted by an arrow 65, is an indication of the speed and direction of its trajectory.
  • This system and its methods can for example assist air traffic controllers in monitoring and controlling the air space in and around a busy airport by directing attention to only those aircraft that are on direct approach, or, help prioritize the deployment of countermeasures for the protection of a restricted military zone.
  • Figure 2 illustrates the overall flow of decisions and logic employed to issue a timely alert regarding an impending intrusion.
  • the system of the present invention Upon detection of the presence of an object by an associated tracking system, the system of the present invention first makes a determination 91 whether the object is sure to intrude laterally, will surely not intrude laterally, or might intrude laterally. This determination is based on the object's perceived position and track velocity as projected onto a horizontal plane presumes that it will not deviate from its flight path and also takes into consideration the uncertainty inherent in the tracking measurements. At this point only the lateral intrusion into the predefined region is of concern and therefore, position and movement are considered only in two dimensions as depicted in Figure 1.
  • the tracking system provides an object's position (x,y) in a horizontal plane as well as its horizontal velocity vector (X,Y). If the object's perceived track speed is below a predefined level: X 2 + Y 2 ⁇ Q1 the object is considered to be moving too slowly to warrant attention and no further processing is performed. If however the object's track speed is above the predefined level Q1, processing continues by reorienting the entire coordinate system along the object's velocity vector to simplify subsequent calculations.
  • Figure 4 illustrates an object at 75 approaching a predefined polygonal region 79.
  • the position of each vertex (80-83) of the region 79 is initially defined by (a i ,b i ) coordinates.
  • each vertex is redefined as (A i ,B i ) while the object's position would necessarily be defined by (O,O).
  • the uncertainty of the object's positional and velocity measurements are interrelated in the denominator of Equation 5 and in effect serve to project an uncertainty zone 84 out in front of the moving object 78 as illustrated in Figure 5.
  • a number of different combinations and permutations are then possible regarding the relationship of a particular predefined region relative to the uncertainty zone 84, i.e., the region can either lie wholly outside 85,86 or wholly inside 87 the zone 84. Alternatively, the region 88,89 can lie partly inside and partly outside the zone or the region 90 can wholly envelope the uncertainty zone.
  • the next step for either a sure intrusion 90 or an unsure intrusion (87, 88, 89) condition entails calculating the lateral entry time 93 of the approaching object 78 into the predefined polygonal region. This is accomplished by considering the vertex closest to the approaching object i.e. the smallest A i which shall be designated A j .
  • the time delay filter 97 is invoked when an unsure intrusion (87, 88, 89) had been indicated in the lateral intrusion determination 91. If T1 > T min then no alert is indicated. If T1 ⁇ T min , processing continues on towards the height final alert process 105.
  • a decision whether to indicate an alert condition or not is made depending on whether missed detections are to be controlled at the expense of false alarms or vice versa. If missed detections are to be controlled at the expense of false alarms, and if: J i > Q7 for any i then processing continues. Otherwise no alert is issued. If on the other hand, false alarms are to be controlled at the expense of missed detections, a second predefined parameter Q8 is considered and if for any two indices j and k: J j > Q8 J k > Q8 and the sign of B j equals the sign of B k then processing continues. Otherwise no alert is issued.
  • the entry time of lateral intrusion T 1 As well as the exit time of lateral intrusion T2.
  • the knowledge that an approaching object is above the predefined region at the time of lateral entry does not preclude the possibility of an intrusion. It must therefore also be determined whether the approaching object still has sufficient altitude at the time the predefined polygonal zone is laterally exited.
  • the lateral exit time T2 is calculated 101 in a manner analogous to the calculation of the entry time T1 93.
  • the vertex furthest from the approaching object i.e.
  • the height variance HP, height rate variance HV and height-height rate covariance HC are considered in conjunction with the upper height limit HU and lower height limit HL to provide the final decisions regarding the potential for intrusion.
  • E 1 Q10 (HP + 2HC ⁇ T + HV ⁇ T 1 2 ) 1/2
  • E 2 Q11 (HP + 2HC ⁇ T + HV ⁇ T 1 2 ) 1/2 wherein Q10 and Q11 are predefined parameters.
  • an alert will be issued at 105 if any of the following conditions (equations 29-32) are satisfied: HL ⁇ h + H ⁇ T 1 ⁇ HU HL ⁇ h + H ⁇ T 2 ⁇ HU h + H ⁇ T 1 ⁇ HU and h + H ⁇ T 2 ⁇ HL h + H ⁇ T 1 ⁇ HL and h + H ⁇ T 2 ⁇ HU otherwise no alert will be issued.
  • the alert is turned off if a lateral sure non-intrusion is indicated (Equations 7 & 8) or if either of the following conditions regarding the approaching objects height dynamics are indicated: HL - E 1 > h + H ⁇ T 1 and HL - E 2 > h + H ⁇ T 2 HV + E 1 ⁇ h + H ⁇ T 1 and HU + E 2 ⁇ h + H ⁇ T 2
  • the system and methods of the present invention are employed in conjunction with a tracking system which is capable of supplying positional as well as dynamic data for a plurality of moving objects.
  • the perimeter of the predefined polygonal zone is precisely known. The first consideration made is whether a particular object is moving fast enough and in fact toward the predefined polygonal zone. Each object that survives these two considerations then in effect has an uncertainty region projected along its velocity vector.
  • the predefined polygonal zone is then considered in relation to the uncertainty region and depending on its positional relationship the determination whether a sure intrusion exists, a sure non-intrusion exists, or an unsure intrusion is indicated can then be made. If an intrusion is possible, the time for lateral entry and exit is calculated after which the height position and dynamics are taken into consideration.
  • the various parameters employed in the various calculations and determinations are selected according to the requirements of a specific installation. Appropriate adjustment of the values of these various parameters will ultimately determine whether tracking errors will tend to yield false alarms or undetected intrusions.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar Systems Or Details Thereof (AREA)
EP19900308833 1989-08-29 1990-08-10 Early warning tracking system Expired - Lifetime EP0415587B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US40025889A 1989-08-29 1989-08-29
US400258 1989-08-29

Publications (3)

Publication Number Publication Date
EP0415587A2 EP0415587A2 (en) 1991-03-06
EP0415587A3 EP0415587A3 (en) 1992-12-23
EP0415587B1 true EP0415587B1 (en) 1996-01-03

Family

ID=23582869

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900308833 Expired - Lifetime EP0415587B1 (en) 1989-08-29 1990-08-10 Early warning tracking system

Country Status (6)

Country Link
EP (1) EP0415587B1 (fi)
AU (1) AU612082B1 (fi)
CA (1) CA2022313A1 (fi)
DE (1) DE69024563T2 (fi)
FI (1) FI904196A0 (fi)
HK (1) HK105496A (fi)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19843799A1 (de) * 1998-09-24 2000-03-30 Euro Telematik Gmbh Verfahren und Anordnung zur Verringerung der Kollisionsgefahr von Luftfahrzeugen
EP1517281B1 (en) * 2003-09-16 2007-10-31 COMSOFT GmbH Safety nets for alerting of hazardous situations in air traffic

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4196474A (en) * 1974-02-11 1980-04-01 The Johns Hopkins University Information display method and apparatus for air traffic control
US4839658A (en) * 1986-07-28 1989-06-13 Hughes Aircraft Company Process for en route aircraft conflict alert determination and prediction
US4823272A (en) * 1987-03-06 1989-04-18 International Business Machines Corporation N-Dimensional information display method for air traffic control
US4899161A (en) * 1988-07-21 1990-02-06 International Business Machines Corporation High accuracy coordinate conversion method for air traffic control applications
US5058024A (en) * 1989-01-23 1991-10-15 International Business Machines Corporation Conflict detection and resolution between moving objects

Also Published As

Publication number Publication date
DE69024563T2 (de) 1996-09-05
HK105496A (en) 1996-06-28
EP0415587A3 (en) 1992-12-23
CA2022313A1 (en) 1991-03-01
AU612082B1 (en) 1991-06-27
DE69024563D1 (de) 1996-02-15
EP0415587A2 (en) 1991-03-06
FI904196A0 (fi) 1990-08-24

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