Inertial transformation matrix generator

• US 5,001,647 A
• Filed: 08/31/1989
• Issued: 03/19/1991
• Est. Priority Date: 08/31/1989
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: General Electric Company
• Inventors: Rapiejko, Stephen J., Chan, David S., Clark, Nancy M., Staver, Daniel A.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US07/401,372
• Time in Patent Office: 565 Days
• Field of Search: 364/433, 364/434, 364/447, 364/453, 364/454, 364/553, 364/559, 364/715.03, 364/725, 244/3.2, 244/3.21
• US Class Current: 701/220
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems

Abstract

An inertial transformation matrix generator generates a succession of Euler transformation matrices in inertial coordinates, and is useful for converting to inertial coordinates the responses of a sensor hard mounted on the hull of a craft (e.g., an aircraft). First, second and third rate-sensing gyros located proximately to said sensor are strapped down to the craft hull, and are oriented to sense the motion of the craft hull in three mutually orthogonal directions, for providing respective output signals indicative of components of craft hull motion in each of those three mutually orthogonal directions. The output signals of the gyros are digitized, and based on these digital signals successive incremental Euler transformation matrices are generated. Each successive incremental Euler transformation matrix and a respective other matrix are multiplied together to generate a respective product matrix, said other matrix initially being a initialization matrix and thereafter being the previously calculated Euler transformation matrix. Each successive current Euler transformation matrix is formed from each successive product matrix, which is done in preferred embodiments of the invention by adding to it at selected times a correction matrix derived by long term comparison of the matrices generated by the inertial transformation matrix generator and the inertial navigation system of the craft.

Claims

1. An inertial transformation matrix generator for generating an Euler transformation matrix in inertial coordinates, to be installed in a craft having an inertial navigation system, for use in converting to inertial coordinates the response of a craft-borne sensor hard mounted on the hull of a craft, said inertial transformation matrix generator comprising:

first, second and third rate-sensing gyros, located proximate to said sensor, for being strapped down to said craft hull, and oriented to sense motion of the craft hull in three mutually orthogonal directions, for providing respective output signals indicative of components of craft hull motion in each of said three mutually orthogonal directions;

analog-to-digital conversion circuitry for digitizing the output signals of said first, second and third gyros;

means for generating successive incremental Euler transformation matrices based on said digitized output signals of said first, second and third gyros;

means for matrix multiplying together each successive said incremental Euler matrix and a respective other matrix to generate a respective product matrix, said other matrix initially being an initialization matrix from said inertial navigation system and thereafter being the previously calculated Euler transformation matrix; and

means for forming each successive current Euler transformation matrix from each successive product matrix.

2. An inertial transformation matrix generator as set forth in claim 1, wherein said means for generating successive incremental Euler transformation matrices includes:

means for multiplying an orthogonalizing matrix by the digitized output signals of said first, second and third gyros, to compensate for any departure of the axes of said first, second and third gyros from mutual perpendicularity.

3. An inertial transformation matrix generator as set forth in claim 1 wherein said craft is an aircraft.

4. An inertial transformation matrix generator as set forth in claim 1 wherein said craft is a spacecraft.

5. An inertial transformation matrix generator as set forth in claim 1 wherein said craft is a seacraft.

6. An inertial transformation matrix generator as set forth in claim 1 wherein said craft is an underseacraft.

7. An inertial transformation matrix generator as set forth in claim 1 wherein said craft is a landcraft.

8. An inertial transformation matrix generator as set forth in claim 1 said inertial transformation matrix generator including:

means for periodically comparing the average values of successive ones of the generated Euler transformation matrices and of successive ones of the inertial navigation system matrices thereby to generate correction matrices; and

means for adding to the product matrix any concurrent correction matrix supplied from said means for periodically comparing averages, included within said means for forming each successive Euler transformation matrix from each successive product matrix.

9. An inertial transformation matrix generator as set forth in claim 8 wherein said means for periodically comparing the average values of successive ones of the generated Euler transformation matrices and of successive ones of the inertial navigation system matrices comprises:

means for supplying the generated Euler transformation matrices and the inertial navigation system matrices with corresponding elements of the matrice in temporal alignment;

means for subtracting each element of the generated Euler transformation matrix from the corresponding element of inertial navigation system matrix to generate a respective one of a succession of difference matrices; and

means for low-pass filtering said difference matrices to generate said correction matrices.

10. An inertial transformation matrix generator as set forth claim 8 wherein said means for generating successive incremental Euler transformation matrices includes:

means for multiplying an orthogonalizing matrix by the digitized output signals of said first, second and third gyros, to compensate for any departure of the axes of said first, second and third gyros from mutual perpendicularity.

11. An inertial transformation matrix generator for generating an Euler transformation matrix in inertial coordinates, to be installed in a craft having an inertial navigation system for use in converting to inertial coordinates the responses of a craft-borne sensor hard mounted on the hull of a craft, aid inertial transformation matrix generator comprising:

first, second and third rate-sensing gyros, located proximate to said sensor, for being strapped down to said craft hull, and oriented to sense motion of the craft hull in three mutually orthogonal directions, for providing respective output signals indicative of components of craft hull motion in each of said three mutually orthogonal directions;

analog-to-digital conversion circuitry for digitizing the output signals of said first, second ad third gyros;

means for generating successive incremental Euler transformation matrices based on said digitized output signals of said first, second and third gyros;

means for matrix multiplying together each successive said incremental Euler matrix and a respective other matrix to generate a respective product matrix, said other matrix initially being an initialization matrix from said inertial navigation system and thereafter being the previously calculated Euler transformation matrix;

means for periodically comparing the average values of successive ones of the generated Euler transformation matrices and of successive ones of the inertial navigation system matrices thereby to generate correction matrices; and

means for forming each successive current Euler transformation matrix from each successive product matrix, including

means for adding to the product matrix any concurrent correction matrix supplied from said means for periodically comparing averages, wherein said means for matrix multiplying comprises;

a multiplier having first and second input ports and an output port;

an accumulator including therein said means for adding, having an input port to which the output port of said multiplier is connected and having an output port;

a memory for temporarily storing the incremental Euler transformation matrix, as written thereto from said means for digitizing the output signals of said gyros, and as read therefrom in an element by element scanning to the first input port of said multiplier;

a memory for temporarily storing said other matrix, as read therefrom in an element by element scanning to the second input port of said multiplier; and

a memory for temporarily storing said updated Euler transformation matrix, as written thereto from the output port of said accumulator, and as read therefrom as said previously calculated Euler transformation matrix for writing said memory for temporarily storing said other matrix.

12. An inertial transformation matrix generator for generating an Euler transformation matrix in inertial coordinates, to be installed in a craft having an inertial navigation system for use in converting to inertial coordinates the responses of a craft-borne sensor hard mounted on the hull of a craft, said inertial transformation matrix generator comprising:

first, second and third rate-sensing gyros, located proximate to said sensor, for being strapped down to said craft hull, and oriented to sense motion of the craft hull in three mutually orthogonal directions, for providing respective output signals indicative of components of craft hull motion in each of said three mutually orthogonal directions;

analog-to-digital conversion circuitry for digitizing the output signals of said first, second and third gyros;

means for generating successive incremental Euler transformation matrices based on said digitized output signals of said first, second and third gyros;

means for matrix multiplying together each successive said incremental Euler matrix and a respective other matrix to generate a respective product matrix, said other matrix initially being an initialization matrix from said inertial navigation system and thereafter being the previously calculated Euler transformation matrix; and

means for forming each successive current Euler transformation matrix from each successive product matrix, wherein said means for matrix multiplying comprises;

a multiplier having first and second input ports and an output port;

an accumulator including therein said means for adding, having an input port to which the output port of said multiplier is connected and having an output port;

a memory for temporarily storing the incremental Euler transformation matrix, as written thereto from said means for digitizing the output signals of said gyros, and as read therefrom in an element by element scanning to the first input port of said multiplier;

a memory for temporarily storing said other matrix, as read therefrom in an element by element scanning to the second input port of said multiplier; and

a memory for temporarily storing said updated Euler transformation matrix, as written thereto from the output port of said accumulator, and as read therefrom as said previously calculated Euler transformation matrix for writing said memory for temporarily storing said other matrix.

13. A combination including

a craft-borne sensor hard mounted on the hull of a craft having an inertial navigation system;

apparatus for generating an Euler transformation matrix in inertial coordinates; and

a matrix multiplier for multiplying data from said sensor by said Euler transformation matrix in inertial coordinates, wherein said apparatus for generating an Euler transformation matrix in inertial coordinates is an inertial transformation matrix generator comprising;

first, second and third rate-sensing gyros, located proximate to said sensor, strapped down to said craft hull, and oriented to sense motion of the craft hull in three mutually orthogonal directions, for providing respective output signals indicative of components of craft hull motion in each of said three mutually orthogonal directions;

analog-to-digital conversion circuitry for digitizing the output signals of said first, second and third gyros;

means for generating successive incremental Euler transformation matrices based on said digitized output signals of said first, second and third gyros;

means for matrix multiplying together each successive said incremental Euler matrix and a respective other matrix to generate a respective product matrix, said other matrix initially being an initialization matrix from said inertial navigation system and thereafter being the previously calculated Euler transformation matrix; and

means for forming each successive current Euler transformation matrix from each successive product matrix.

14. A combination as set forth in claim 13 wherein said means for generating successive incremental Euler transformation matrices includes:

means for multiplying an orthogonalizing matrix by the digitized output signals of said first, second and third gyros, to compensate for any departure of the axes of said first, second and third gyros from mutual perpendicularity.

15. An inertial transformation matrix generator as set forth in claim 13, wherein said means for matrix multiplying comprises:

a multiplier having first and second input ports and an output port;

an accumulator including therein said means for adding, having an input port to which the output port of said multiplier is connected and having an output port;

a memory for temporarily storing the incremental Euler transformation matrix, as written thereto from said means for digitizing the output signals of said gyros, and as read therefrom in an element by element scanning to the first input port of said multiplier;

a memory for temporarily storing said other matrix, as read therefrom in an element by element scanning to the second input port of said multiplier; and

a memory for temporarily storing said updated Euler transformation matrix, as written thereto from the output port of said accumulator, and as read therefrom as said previously calculated Euler transformation matrix for writing said memory for temporarily storing said other matrix.

16. A combination as set forth in claim 13 wherein said craft is an aircraft.

17. A combination as set forth in claim 13 wherein said inertial transformation matrix generator includes:

means for periodically comparing the average values of successive ones of the generated Euler transformation matrices and of successive ones of the inertial navigation system matrices thereby to generate correction matrices; and

means for adding to the product matrix any concurrent correction matrix supplied from said means for periodically comparing averages, included within said means for forming each successive Euler transformation matrix from each successive product matrix.

18. A combination as set forth in claim 17 wherein said means for periodically comparing the average values of successive ones of the generated Euler transformation matrices and of successive ones of the inertial navigation system matrices comprises:

means for supplying the generated Euler transformation matrices and the inertial navigation system matrices with corresponding elements of the matrice in temporal alignment;

means for subtracting each element of the generated Euler transformation matrix from the corresponding element of inertial navigation system matrix to generate a respective one of a succession of difference matrices; and

means for low-pass filtering said difference matrices to generate said correction matrices.

19. A combination as set forth in claim 17, wherein said means for multiplying comprises:

a multiplier having first and second input ports and an output port;

an accumulator including therein said means for adding, having an input port to which the output port of said multiplier is connected and having an output port;

a memory for temporarily storing the incremental Euler transformation matrix, as written thereto from said means for digitizing the output signals of said gyros, and as read therefrom in an element by element scanning to the first input port of said multiplier;

a memory for temporarily storing said other matrix, as read therefrom in an element by element scanning to the second input port of said multiplier; and

a memory for temporarily storing said updated Euler transformation matrix, as written thereto from the output port of said accumulator, and as read therefrom as said previously calculated Euler transformation matrix for writing said memory for temporarily storing said other matrix.

20. A combination as set forth in claim 17 wherein said means or generating successive incremental Euler transformation matrices includes:

means for multiplying an orthogonalizing matrix by the digitized output signals of said first, second and third gyros, to compensate for any departure of the axes of said first, second and third gyros from mutual perpendicularity.