Method for checking the reliability of nominal position indications

• US 6,271,789 B1
• Filed: 01/05/2000
• Issued: 08/07/2001
• Est. Priority Date: 04/10/1997
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litef GmbH (Northrop Grumman Corporation)
• Inventors: Beerhold, Jens Rainer
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/402,851
• Time in Patent Office: 580 Days
• Field of Search: 342/357.14, 701/220, 701/221
• US Class Current: 342/357.3
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial

Abstract

A method for checking the reliability of nominal position findings on the basis of propagation time measurements. The method is characterized by the use of inertial systems to increase the measurement redundancy of the available measured values. The dimension of the measurement matrix of the nominal system is advantageously increased for such purpose. The method is primarily suitable for hybrid inertial/satellite navigation systems.

Claims

1. In a method for checking the reliability of nominal position findings on the basis of propagation time measurements in which inertial systems are employed to increase measurement redundancy of measured values available for error identification, the improvement comprising the step of employing said inertial systems to increase dimension of a measurement matrix of a nominal system based on the propagation time measurements.

2. A method as defined in claim 1, further including the step of utilizing an inertial vertical component to increase the measurement redundancy of the measurement matrix of the nominal system.

3. A method as defined in claim 1 including the step of using at least one inertial horizontal component to increase the measurement redundancy of the measurement matrix of the nominal system.

4. A method as defined in claim 1 including the step of introducing the ratio of noise in nominal pseudo-range measurements to the noise in an inertial component into the measurement matrix of the nominal system.

5. A method as defined in claim 1 including the step of expanding a linearized n×

4 measurement matrix of the nominal system by one line, in which one element contains a value which represents an inertial measurement, to increase dimension.

6. A method as defined in claim 5 wherein the linearized n×

4 measurement matrix of the nominal system has at least one line comprising the elements σ

_sat/σ

x_in, 0, 0, 0 added, σ

_sat being the noise in the nominal pseudo-range measurement and σ

x_in being the noise in the horizontal x-component of the inertial measurement.

7. A method as defined in claim 5 wherein the linearized n×

4 measurement matrix of the nominal system has a line comprising the elements 0, σ

_sat/σ

y_in, 0, 0 added, σ

_sat being the noise in the nominal pseudo-range measurement and σ

y_in being the noise in the horizontal y-component of the inertial measurement.

8. A method as defined in claim 5 wherein the linearized n×

4 measurement matrix of the nominal system has a line comprising the elements 0, 0, σ

_sat/σ

z_in, 0 added, σ

_sat being the noise in the nominal pseudo-range measurement and σ

z_in being the noise in the vertical component of the inertial measurement.

9. A method as defined in claim 1 wherein the nominal position finding is carried out by means of a satellite navigation system.

10. A method as defined in claim 1 wherein the n×

4 measurement matrix (G) of the nominal system in general has the following appearance, before its dimension is increased;

$\underset{\_}{G}=\left[\begin{array}{cccc}{c}_{11}& c_{12}& c_{13}& 1\\ c_{21}& c_{22}& c_{23}& 1\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ c_{\mathrm{n1}}& c_{\mathrm{n2}}& c_{\mathrm{n3}}& 1\end{array}\right].$

11. A method as defined in claim 1 wherein said method is used as an instance for error identification in a hybrid inertial/satellite navigation system.