Self-adaptive IRU correction loop design interfacing with the target state estimator for multi-mode terminal handoff

• US 4,783,744 A
• Filed: 12/08/1986
• Issued: 11/08/1988
• Est. Priority Date: 12/08/1986
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: General Dynamics
• Inventors: Yueh, William R.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/939,509
• Time in Patent Office: 701 Days
• Field of Search: 364/423, 364/443, 364/453, 364/454, 364/457, 364/571, 364/462, 244/3.2, 342/62, 342/77, 235/412, 235/413
• US Class Current: 701/221
• CPC Class Codes: F41G 7/30 Command link guidance systems homing F41G7/2206

Abstract

A method and apparatus for identifying inertial reference unit (IRU) errors in a guided missile employing a multi-mode guidance system and constructing correction terms to recover the missile true position. Discrepancy parameters are introduced to indicate misalignment between missile and launching platform (or ship) inertial frames where the missile onboard executive computer simultaneously processes the data provided from missile onboard sensors and target relevant data uplinked from the launching platform. The discrepancy parameters are employed to construct correction factors used to reduce the discrepancies. This updated missile configuration is then coupled with the target state estimator outputs to reconstruct smoothed line-of-sight (LOS) angles for terminal homing engagement.

Claims

1. A target state estimation system in a missile for multi-mode guidance of said missile where measured range and range rate information and unavailable, wherein a missile launching platform having an established inertial frame of reference senses target radiation in the form of electromagnetic signals transmitted by a target, generates corresponding missile launching platform target line-of-sight (LOS) data referenced to said missile launching platform inertial frame of reference, and communicates said missile launching platform target LOS data to said missile, said missile target state estimator system comprising:

sensor means onboard said missile for sensing said target radiation and, in response thereto, for generating missile target LOS data;

inertial reference unit (IRU) means onboard said missile for establishing a missile coordinate frame of reference for said missile and for generating IRU missile state information with respect to said missile coordinate frame of reference;

a central control system onboard said missile connected to said sensor means and said IRU means, said central control system comprising Kalman filter means for receiving missile launching platform target LOS data, missile target LOS data and IRU missile state information for generating updated target state data based upon estimations of target state from previous missile launching platform target LOS data, missile target LOS data and IRU missile state information, updated subsequent missile launching platform target LOS data, missile target LOS data and IRU missile state information so as to provide estimates of current target state data corresponding to target acceleration, velocity, position, range-to-go, and reconstructed azimuth and elevation LOS angles, wherein said Kalman filter means comprises a multi-state horizontal filter and a multi-state vertical filter each kinematically modeled for expected target characteristics, said horizontal filter having a kinematic target model of a horizontal plane multi-state vector with one state of said horizontal plane multi-state vector defining a first range estimate discrepancy parameter and said vertical filter having a kinematic target model of a vertical plane multi-state vector with one state of said vertical multi-state vector defining a second range estimate discrepancy parameter, said horizontal and vertical filters coupled for crosstalk between said first and second range estimate discrepancy parameters; and

IRU adaptive correction means onboard said missile, connected between said central control system and said IRU means, and responsive to at least one input correction factor, with each input correction factor corresponding to a respective one of said first and second range estimate discrepancy parameters, and at least one corresponding geometry factor from said central control system, for generating a corresponding alignment correction factor which is provided to said IRU means, wherein said IRU means in response to said alignment correction factor provides corrected IRU missile state information to said Kalman filter means so as to correct unmodeled errors in said missile coordinate frame of reference and align said missile coordinate frame of reference with said missile launching platform inertial frame of reference.

2. The target state estimation system of claim 1

wherein said missile launching platform is a ship having a reference location and defining said missile launching platform inertial frame of reference;

and

wherein said IRU means established missile coordinate frame of reference is initially aligned with respect to said missile launching platform inertial frame of reference, to which the missile launching platform LOS data are related.

3. The target state estimation system of claim 2 further comprising:

means on said missile launching platform for determining missile launching platform azimuth and elevation target LOS data with respect to said target;

means for uplinking said missile launching platform target LOS data from said missile launching platform to said missile; and

wherein said uplinked missile launching platform target LOS data is employed by said central control system for target state estimation.

4. The target state estimation system of claim 2 further comprising:

a third party aircraft;

means on said aircraft for determining aircraft target LOS data with respect to said target;

means for uplinking said aircraft target LOS data from said aircraft to said missile; and

wherein said uplinked aircraft target LOS data is employed by said central control system for target state estimation.

5. The target state estimation system of claim 2 further comprising:

a third party aircraft;

means on said aircraft for determining aircraft target LOS data with respect to said target;

means for coupling said aircraft target LOS data to said missile launching platform;

means for uplinking said aircraft target LOS data from said missile launching platform to said missile, said aircraft target LOS data being referenced with respect to said missile launching platform; and

wherein said uplinked aircraft LOS data is employed by said central control system for target state estimation.

6. The target state estimation system of claim 1 wherein said horizontal filter has seven states and said vertical filter has four states.

7. A method for target state estimation by a missile for multi-mode guidance of said missile where measured range and range rate information are unavailable, wherein a missile launching platform provides missile launching platform target line-of-sight (LOS) data referenced to an established missile launching platform inertial frame of reference, said method comprising the steps of:

sensing target radiations in the form of electromagnetic signals transmitted by a target by sensor means onboard said missile;

generating missile target LOS data from said sensed target radiations;

receiving onboard said missile, missile launching platform target LOS data;

providing a missile coordinate frame of reference onboard said missile from an inertial reference unit (IRU);

generating in said IRU, IRU missile state information with respect to said missile coordinate frame of reference;

providing a kinematic target model of a horizontal plane multi-state vector in a horizontal multi-state recursive Kalman-type filter wherein one of said horizontal plane vector states defines a first range estimate discrepancy parameter;

providing a kinematic target model of a vertical plane multi-state vector in a vertical multi-state recursive Kalman-type filter wherein one of said vertical plane vector states defines a second range estimate discrepancy parameter;

coupling said horizontal and said vertical filters together by crosstalking said first and second range estimate discrepancy parameters;

coupling said missile launching platform target LOS data and said missile target LOS data to said horizontal and vertical Kalman-type filters;

providing at least one input correction factor, each input correction factor corresponding to a respective one of said first and second range estimate discrepancy parameters, from said horizontal and vertical Kalman-type filters to an adaptive correction means;

providing at least one geometry factor, each corresponding to a respective one of said input correction factors, from said horizontal and vertical Kalman-type filters to said adaptive correction means;

generating at least one alignment correction factor, each alignment correction factor corresponding to corresponding input correction factors and geometry factors;

providing corrected IRU missile state information from said IRU means, in response to each alignment correction factor, to said horizontal and vertical Kalman-type filters so as to correct unmodeled errors in said missile coordinate frame of reference and align said missile coordinate frame of reference with said missile launching platform inertial frame of reference;

recursively providing, in said horizontal and vertical Kalman-type filters, updated target state data based on estimations of target state from previous missile launching platform target LOS data, missile target LOS data and IRU missile state information updated by subsequent missile launching platform target LOS data, missile target LOS data and IRU missile state information; and

providing estimates of target acceleration, velocity, position, range-to-go and reconstructed LOS angles for both azimuth and elevation angles, from said updated target state data.

8. The method of claim 7 further comprising the step of:

providing said missile launching platform in the form of a ship having a reference location and defining said missile launching platform inertial frame of reference, wherein said missile coordinate frame of reference is initially aligned with respect to said missile launching platform inertial frame of reference.

9. The method of claim 8 further comprising the steps of:

determining, on said missile launching platform, missile launching platform azimuth and elevation target LOS data; and

uplinking said missile launching platform target LOS data from said missile launching platform to said missile.

10. The method of claim 8 further comprising the steps of:

providing an aircraft;

determining, in said aircraft, aircraft target LOS data with respect to said target; and

uplinking said aircraft target LOS data from said aircraft to said missile, wherein said missile uses said aircraft target LOS data with said missile launching platform target LOS data for generating estimates of current target state data.

11. The method of claim 8 further comprising the steps of:

providing an aircraft;

determining, in said aircraft, aircraft target LOS data with respect to said target;

coupling said aircraft target LOS data to said missile launching platform;

uplinking said aircraft target LOS data from said missile launching platform to said missile, wherein said uplinked aircraft LOS data is referenced with respect to said missile launching platform and wherein said missile uses said aircraft target LOS data with said missile launching platform target LOS data for generating estimates of current target state data.