Integrity-optimized receiver autonomous integrity monitoring (RAIM) for vertical integrity monitoring

• US 7,956,802 B1
• Filed: 05/21/2007
• Issued: 06/07/2011
• Est. Priority Date: 05/21/2007
• Status: Active Grant

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Hwang, Patrick Y., Brown, R. Grover
• Primary Examiner(s): Keith; Jack
• Assistant Examiner(s): Shafi; Muhammad
• Application Number:
  US11/804,830
• Time in Patent Office: 1,478 Days
• Field of Search: 701/214, 701/3, 701/213, 701/215, 701/200, 701/207, 701/211, 701/220, 701/221, 701/1, 701/9, 701/14, 701/17, 701/210, 701/218, 701/219, 342/357.31, 342/358, 731/78.T, 455/12.1, 455/427, 455/456.1, 340/970, 340/990, 340/995
• US Class Current: 342/357.58
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment

Abstract

A vertical integrity monitoring method and system are described. The vertical integrity monitoring method includes determining a noise sigma ratio parameter. The method also includes determining two vertical protection limit slopes and an associated covariance matrix. The method further includes determining a vertical integrity limit and set of weights based on the VPL slopes, covariance and the parameter; and applying the set of weights based on the parameter to calculate a vertical solution. An integrity monitoring system may have hardware and/or software embodying the one or more methods described.

Claims

1. An integrity monitoring system for an aircraft, comprising:

receivers for providing two independent position measurements;

a noise parameter generation subsystem configured to determine a ratio of the noise standard deviations for the two independent position measurements;

a slope determination subsystem configured to use the ratio of the noise standard deviations and a scaling parameter to determine two vertical protection limit (VPL) slopes and an associated covariance matrix, wherein each of the two VPL slopes are associated with a failure affecting one of the two independent position measurements;

a vertical integrity limit subsystem configured to determine a vertical integrity limit by analyzing the VPL slopes;

wherein the vertical integrity limit subsystem is further configured to search for the scaling parameter estimated to minimize the vertical integrity limit using the two VPL slopes and the associated covariance matrix, wherein the scaling parameter represents a non-uniform weighting for the two independent position measurements; and

a vertical solution subsystem configured to determine if a navigation system for the aircraft is available by determining whether the vertical integrity limit is less than a threshold.

2. The system of claim 1, wherein the covariance matrix is the covariance of the noise distribution in the parity-error (P-E) space.

3. The system of claim 1, wherein results from the slope determination subsystem and the vertical integrity limit subsystem are stored in a one-dimensional lookup table having the ratio of the noise standard deviations for the two independent position measurements as the input and the vertical integrity limit as an output.

4. The system of claim 1,

wherein the receivers comprise a first receiver configured to receive a first position from a first positioning system and a second receiver configured to receive a second position from a second positioning system.

5. The system of claim 4, wherein the first positioning system is a GPS system and the second positioning system is another GNSS.