Strapdown inertial navigation system using high order

• US 5,422,817 A
• Filed: 08/13/1991
• Issued: 06/06/1995
• Est. Priority Date: 08/13/1991
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Tazartes, Daniel A., Mark, John G.
• Primary Examiner(s): Cain, David C.
• Application Number:
  US07/744,178
• Time in Patent Office: 1,393 Days
• Field of Search: 364/571.01, 364/571.03, 364/454, 364/566
• US Class Current: 702/93
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems

Abstract

Sculling error correction means, using third or higher order correction to correct for sculling errors in apparatus for converting angle measuring and acceleration measuring signals from a vehicle set of coordinates into a stabilized set of navigation coordinates.

Claims

1. Apparatus for converting signals from vehicle-referenced coordinates into stabilized navigation coordinates, comprising:

angle measuring means for producing first angle signals, sampled at a first sampling frequency, in a first set of movable coordinates;

attitude integration means, connected to receive said first sampled angle signals and to transform them into second sampled angle signals in a second set of stabilized navigation coordinates;

accelerometer means for producing first acceleration signals, sampled at said first frequency, that are measures of changes in velocity in said first set of coordinates;

sculling correction means of order higher than the first, receiving said first acceleration signals and creating incremental velocity correction signals;

means for subtracting said incremental velocity correction signals from said first acceleration signals to produce first compensated incremental velocity signals that are measures of changes in velocity, corrected for sculling errors, in said first set of coordinates; and

coordinate transformation means, connected to receive said second sampled angle signals and said compensated incremental velocity signals for transforming said compensated incremental velocity signals into second incremental velocity signals that are measures of changes in velocity, corrected for sculling errors, in said second set of coordinates.

2. Apparatus as recited in claim 1 in which said sculling correction means is of the third order, and in which the third order compensated incremental velocity signals are

3. Apparatus as recited in claim 1 in which said sculling correction means is of the (2j+1)th order, and in which the (2j+1)th order compensated incremental velocity signals are

4. Apparatus for converting signals from vehicle-referenced coordinates into stabilized navigation coordinates, comprising:

angle measuring means for producing first angle signals, sampled at a first sampling frequency, in a first set of movable coordinates;

attitude integration means, connected to receive said first sampled angle signals and to transform them, at a second lower frequency, into second sampled angle signals in a second set of stabilized navigation coordinates;

accelerometer means for producing first acceleration signals, sampled at said first frequency, that are measures of changes in velocity in said first set of coordinates;

sculling correction means of order higher than the first, receiving said first acceleration signals and creating first incremental velocity correction signals;

means for subtracting said first incremental velocity signals from said first acceleration signals to produce first compensated incremental velocity signals that are measures of changes in velocity in said first set of coordinates;

combiner means for combining a number of consecutive samples of said sampled angle signals to produce a modified angle change signal, said number being equal to the ratio of said first sampling frequency to said second sampling frequency;

sculling cross product apparatus, connected to create cross product signals which are the cross product of said first compensated incremental velocity signals and said modified angle change signal;

first and second accumulator means to accumulate, respectively, said cross product signals and said first compensated incremental velocity signals to said lower second frequency;

means for subtracting said accumulated cross product signals from said first accumulated compensated incremental velocity signals to produce second compensated incremental velocity signals; and

coordinate transformation means, connected to receive said second sampled angle signals and said second compensated incremental velocity signals for transforming said second compensated incremental velocity signals into third compensated incremental velocity signals that are measures of changes in velocity, corrected for sculling errors, in said second set of coordinates.

5. Apparatus as recited in claim 4 in which said sculling correction means is of the third order, and in which the compensated incremental velocity signals are

6. Apparatus as recited in claim 4 in which said sculling correction means is of the (2j+1)th order, and in which the (2j+1)th order compensated incremental velocity signals are