Second order complementary global positioning system/inertial navigation system blending filter

• US 20020019701A1
• Filed: 06/20/2001
• Published: 02/14/2002
• Est. Priority Date: 07/28/2000
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Miller, Ronald J.
• Granted Patent: US 6,442,481 B2
• Time in Patent Office: Days
• US Class Current: 701/214
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial

Abstract

A second-order filter that blends accurate position information from a one source, and velocity information from another source, both suitably scaled, in a second-order complementary filter. The filter is arranged such that an internal integrator maintains a value that represents the difference in the rate of change of the accurate position information, and the velocity input of the other source. This velocity difference is applied to another integrator outside the filter, whose initial condition is the position error between the two sources to the second order filter. The output of this latter integrator is a correction signal that grows at a rate equal and opposite to the rate of error build-up of position data from the source whose velocity is used in the second order filter. This correction signal is summed with the original position signal. In addition, the output of the second order filter may be used as a highly accurate position signal.

Claims

1. A second order complementary filter for correcting position errors and velocity errors in an inertial navigation system (INS) comprising:

a blending filter for blending a position signal from a first navigation source with a velocity signal from a second navigation source;

a means for generating an output from the blending filter comprising a rate of change of position error of the first navigation source from the second navigation source;

an integrator for inputting the rate of change of position error when the first navigation source becomes invalid and outputting a dynamic position error signal; and

a means for summing said dynamic position error signal and an inertial navigation system position signal to output a dynamically corrected inertial navigation system position.

2. The invention of claim 1 wherein said first navigation source comprises a global positioning system and said second navigation source comprises the INS.

3. The invention of claim 1 wherein said integrator comprises an INS correction loop for continuous compensation for an INS drift rate when the first navigation source becomes invalid.

4. The invention of claim 3 further comprising a switch for rendering the correction loop operational when the first navigation source becomes invalid.

5. The invention of claim 3 wherein said switch further comprises a hold position for making the output of said integrator constant.

6. A method of correcting position and velocity errors with a second order complementary filter in an inertial navigation system, the method comprising the steps of:

a) blending a position signal from a first navigation source with a velocity signal from a second navigation source with blending filter;

b) generating an output from the blending filter comprising a rate of change of position error of the first navigation source from the second navigation source;

c) creating a position correction signal from the generated output; and

d) applying the corrected signal to the inertial navigation system.

7. The method of claim 6 further comprising the step of continuously repeating steps a) through d).

8. The method of claim 6 further comprising the step of capturing a last value of position error when the first navigation source becomes invalid.

9. The method of claim 6 further comprising the step of switching the second order complimentary filter on when the first navigation source becomes invalid.

10. The method of claim 9 further comprising placing the second order complimentary filter on hold so that the generated output is constant.

11. A second order complementary filter for correcting position errors and velocity errors in an inertial navigation system (INS) comprising:

a blending filter for blending a position signal from a first navigation source with an inertial navigation velocity signal from a second navigation source;

a means for generating a dynamic error signal from said blending filter comprising a rate of change of position error of the first navigation source from the second navigation source;

a means for disconnecting a position input and a position feedback from said blending filter when said input position signal becomes invalid;

a means for summing said dynamic error signal and said inertial navigation system velocity signal to produce a dynamically corrected inertial navigation system velocity signal; and

a means for integrating said inertial navigation velocity signal to produce a corrected inertial navigation system position signal.

12. The invention of claim 11 wherein said first navigation source comprises a global positioning system and said second navigation source comprises the INS.

13. The invention of claim 11 wherein said means for integrating is part of said second order complementary filter.