1. Field of the Invention
The present invention concerns a method and system for tracking clusters of objects based on a random set-based algorithm. More specifically the invention concerns performing random-set based cluster tracking of observable objects in a system having a plurality of detection sensor devices and a tracking processor unit, wherein a group of random objects (cluster) is tracked by utilizing group tracks, each group track having multiple tracks assigned to it for tracking multiple objects. A set of state parameters are maintained for the group track and when a new dataframe is received from one of the detection sensor devices, the state parameters are propagated forward in time to correspond to time of the dataframe measurements, and the propagated results are used to determine all feasible object and track assignments for the measured objects in the dataframe. Each group track is analyzed to resolve it into subtracks, if possible, and a joint assignment problem is solved to select the best set of track assignments.
2. Description of the Related Art
Tracking systems are used in a variety of capacities. In one use, tracking systems are used for monitoring airspace and space over a given geographic region of the earth for the presence of ballistic objects, such as missiles and missile warheads, and also space-borne objects, such as satellites. Such known systems can be implemented on multiple aircraft or satellites in a distributed fashion so as to provide sufficient tracking coverage over the given geographic region.
It can be appreciated that such tracking systems must be reliable and reasonably accurate in order to be of value when used for purposes such as national defense against a missile attack. In known systems, multiple platforms, such as satellites, are positioned in orbit, wherein each satellite has one or more sensors onboard which are directed at the desired portion of earth. When a sensor detects an object within its field of view, data is generated corresponding to the position of the object with respect to the sensor. Typically, the position data from all sensors in the tracking system is processed on a frequent basis, either by a common processor on a satellite or on earth, or by several processors distributed among the satellites. The path of the tracked object, as well as other pertinent information about the object, can then be used in a monitoring system, and/or provided to an anti-missile system which can attempt to destroy the object.
Many known tracking systems are designed to track a single type of object by positively identifying the object on a constant basis, and then tracking its movement by comparing location data of the object from one sensor reading to the next. These systems can be inadequate in a missile tracking system, because missiles can have the capability to release large numbers of decoy objects in addition to warheads, in an effort to confuse the defensive tracking system. Such decoys include balloons, chaff, and other clutter which can be released in large numbers at once to form clusters. In addition, a group of warheads may be released at the same time in a cluster. In such situations, known tracking systems may become unable to distinguish between the objects in the cluster, and are then unable to determine a track for each object from one sensor reading to the next.
Some existing tracking systems implement tracking methods which attempt to track clusters of objects based on the location information provided by the sensors, however the sensor location information can vary in quality from one sensor to the next. This is because each sensor may have a different resolution level due to the individual sensor characteristics, and due to the relative position of the sensor to the object being measured. Accordingly, object location data that shows up in one sensor reading may not appear in the next sensor reading, thereby resulting in an inability to track the objects in the cluster. In addition, known tracking systems are not believed to address the random nature of the relative movement of the objects within a cluster, whereby some objects may appear as one for a while, and whereby some objects may appear as two separate objects, from one sensor reading to the next. The aforementioned problems result in inadequate tracking of the objects in the cluster, thereby leading to an inadequate tracking of the objects of interest, such as warheads, for example.