Shipboard reference for an aircraft navigation system

• US 4,032,759 A
• Filed: 10/24/1975
• Issued: 06/28/1977
• Est. Priority Date: 10/24/1975
• Status: Expired due to Term

• Current Assignee: Kearfott Guidance and Navigation Corporation
• Original Assignee: Singer Company (SVP Holdings Ltd.)
• Inventors: Danik, Boris
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Krass, Errol A.
• Application Number:
  US05/625,429
• Time in Patent Office: 613 Days
• Field of Search: 235/150.25, 73/505, 73/511, 73/514, 73/517 R, 73/518, 73/178 R, 244/177, 244/179, 244/3.20, 244/3.21, 307/121, 318/648, 323/71, 323/72, 346/7, 114/43.5 R, 114/43.5 AC, 343/112 R, 343/112 C, 343/114
• US Class Current: 701/220
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A low cost shipboard reference system for carrying out the rapid alignment of aircraft inertial platforms in which an aircraft quality inertial reference is installed on shipboard and is operated in conjunction with a shipboard Kalman filter providing updating information thereto with the update connection from the Kalman to the shipboard inertial system normally kept opened and always kept opened during aircraft platform alignment to result in reference outputs for use in the aircraft system which are free of correlated noise but of sufficient accuracy for rapid alignment with a small azimuth error.

Claims

1. A method of rapidly aligning aircraft inertial platforms installed in aircraft located aboard an aircraft carrier which changes its location with time, said aircraft carrier thereby having a state vector containing as elements at least the velocity of said aircraft carrier and its position, comprising the steps of:

(a) installing a low-accuracy aircraft type inertial reference system on the aircraft carrier, said system including an inertial subsystem and a Kalman filter, said inertial subsystem providing as outputs quantities representing the velocity of the aircraft carrier,

(b) installing means on the aircraft carrier providing updating information regarding the state vector of the aircraft carrier to said Kalman filter;

(c) providing as a velocity reference to the aircraft the velocity outputs of the inertial subsystem of said inertial reference system;

(d) updating said inertial subsystem of said inertial reference system from said Kalman filter at intervals of the order of magnitude of two hours and never while providing a velocity reference to an aircraft.

2. The method according to claim 1 wherein said Kalman filter is updated using outputs of an electro-magnetic log.

3. The method according to claim 1 wherein said Kalman filter is updated using an electronic position indicating device.

4. The method according to claim 3 wherein said Kalman filter is updated using a Loran set.

5. Apparatus for rapidly aligning an aircraft inertial platform installed in an aircraft which is aboard a moving vehicle, said vehicle thereby having a state vector which includes at least components of velocity and position, comprising:

(a) a low accuracy aircraft type inertial reference system installed on the vehicle, said system including an inertial subsystem and a Kalman filter, said inertial subsystem providing velocity outputs;

(b) means installed on the vehicle coupled as inputs to said Kalman filter of said inertial reference system for providing updating information relating to the state vector of the vehicle;

(c) means for coupling the velocity outputs of said inertial subsystem of said inertial reference system to the aircraft inertial platform of the aircraft to provide a velocity reference thereto; and

(d) means coupling the outputs of said Kalman filter to said inertial subsystem including means for selectively opening and closing the connection therebetween to permit updating at infrequent intervals on the order of magnitude of two hours.

6. Apparatus according to claim 5 wherein said means for providing state vector information comprises an electronic log.

7. Apparatus according to claim 5 wherein said means for providing state vector information comprises electronic position indicating means.

8. Apparatus according to claim 7 wherein said position indicating means comprises a Loran set.

9. Apparatus according to claim 5 wherein said Kalman filter comprises a programmed digital computer.

10. Apparatus according to claim 5 wherein said vehicle is an aircraft carrier.