Breaklock detection system and method

The present invention relates to trackers that track targets and to an improved system for detecting when a tracker is no longer locked on the target. A tracking system controls an aimed device () to keep it aimed at a target (). A control system () determines when the tracker has lost its lock on the target () by comparing the target's instantaneous acceleration with its median acceleration. When the difference exceeds a predetermined threshold, the system searches backwards through a chronological buffer until it finds position data which antedate the receipt of inaccurate position data from the tracker. A second-order filter such as a Kalman filter is used to provide estimated target states. The difference between a time updated output from the second-order filter () and the present measured state from the tracking device is low pass filtered to provide a measurement of the instantaneous acceleration of the target. The buffer () stores position, velocity, and median acceleration values covering a span of time at least about twice as long as the time required to determine that a breaklock has occurred.