Dynamic inertial coordinate system maneuver detector and processing method

• US 5,631,653 A
• Filed: 04/25/1996
• Issued: 05/20/1997
• Est. Priority Date: 04/25/1996
• Status: Expired due to Fees

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Reedy, Robert W.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/637,913
• Time in Patent Office: 390 Days
• Field of Search: 342/62, 342/63, 342/77, 342/81, 342/90, 342/95, 342/96, 342/97, 342/102, 342/162, 342/195
• US Class Current: 342/62
• CPC Class Codes: G01S 13/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 13/723 by using numerical data

Abstract

A maneuver detector and processing method for use in target trackers employed in weapon guidance systems, and the like, that employs multidimensional measurements and a set of inertial coordinate systems. The maneuver detector and processing method are implemented as follows. Time-delayed target position and velocity estimates of the target are maintained in a history file. These estimates are continuously updated, in that they are transformed 24 into intermediate north, east, down (NED) range Cartesian coordinate systems by correcting for aircraft motion. For each measurement time, the histories are used to predict the position and velocity of the target in an "observation-relative" inertial coordinate system aligned with the line-of-sight to the target. The error between the prediction and observation is calculated and used with the measurement accuracies to calculate a maneuver probability.

Claims

1. A maneuver detection method for use in a target tracking system disposed in a vehicle that is employed to detect a maneuvering target, said method comprising the steps of:

determining time-delayed target position and velocity estimates of a moving target and storing the time-delayed target position and velocity estimates in a history file;

continuously updating the time-delayed target position and velocity estimates by transforming them into an intermediate Cartesian coordinate system and correcting for motion of the vehicle;

for each measurement time, processing the updated time-delayed target position and velocity estimates to predict the position and velocity of the target in an observation-relative inertial coordinate system aligned with the line-of-sight between the aircraft and the target;

calculating an error between the predicted position and velocity of the target and the current observed position and velocity of the target; and

calculating a maneuver probability that is indicative of whether the target is maneuvering using the error and predetermined measurement accuracies of the target tracking system.

2. A maneuver detection method for use in a target tracking system disposed in a vehicle that is employed to detect a maneuvering target, said method comprising the steps of:

estimating a predetermined parameter associated with a target at a time prior to a present observation time of the target;

predicting the predetermined parameter at the time of observation of the target, assuming constant-velocity, straight line motion of the target;

comparing the predicted parameter to an actual observation measurement of the parameter at the time of observation and processing residuals derived from the comparison to determine the probability that the target is maneuvering; and

outputting a signal derived from the residual processing to provide a maneuver indication.

3. The method of claim 2 wherein the step of determining the probability that the target is maneuvering comprises the steps of:

comparing values derived from an observation to those predicted from histories of a best estimate of target position and velocity, which histories correspond to smoothed position and velocity values; and

estimating maneuver probabilities indicative of the probability that the target is maneuvering.

4. The method of claim 3 wherein the smoothed position and velocity values correspond to a best estimate of target position and velocity.

5. The method of claim 3 wherein the step of estimating maneuver probabilities include probabilities corresponding to position along a line-of-sight direction to a target (Z_x), position in a cross-line-of-sight direction (Z_y), and velocity along the line-of-sight direction (V_zx).

6. A maneuver detection method for use in a target tracking system disposed in a vehicle that is employed to detect a maneuvering target, said method comprising the steps of:

generating a trackfile database that contains smoothed position and velocity estimate data of a moving target;

generating a navigation database that contains velocity and acceleration data for the vehicle;

processing the data from the trackfile and navigation databases to generate an updated history file containing target position and velocity estimates in platform-relative coordinates;

rotating the target position and velocity estimates from the history file into observation-relative inertial coordinates;

generating an observation database that contains observed data comprising range, range-rate, azimuth and elevation data of the target;

transforming the observed data into observation-relative inertial coordinates; and

comparing the transformed data target position and velocity estimates to observed target position and velocity values and calculating probilities and confidence values indicative of whether the target is maneuvering.

7. A maneuver detector for use in a target tracking system disposed in a vehicle that is employed to detect a maneuvering target, said maneuver detector comprising:

a trackfile database that contains smoothed position and velocity estimate data of a moving target;

a navigation database that contains velocity and acceleration data for the vehicle;

an observation database that contains observed data comprising range, range-rate, azimuth and elevation data of the target; and

a processor for processing the data from the trackfile and navigation databases to generate an updated history file containing target position and velocity estimates in platform-relative coordinates, for rotating the target position and velocity estimates from the history file into observation-relative inertial coordinates, for transforming the observed data into observation-relative inertial coordinates, and for comparing the transformed data target position and velocity estimates to observed target position and velocity values and calculating probilities and confidence values indicative of whether the target is maneuvering.