Reducing bias impact on GNSS integrity

Patent metadata

Field	Value
Publication number	US-11143765-B2
Application number	US-201916394988-A
Country	US
Kind code	B2
Filing date	Apr 25, 2019
Priority date	Apr 25, 2019
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

Systems and methods for reducing bias impact on GNSS integrity are described herein. In certain embodiments, a method includes determining a phase of travel of a vehicle. The method also includes determining a probability of hazardously misleading information (PHMI) for the corresponding phase of travel. Further, the method includes determining a protection level (PL) using based on the PHMI, wherein the PL is calculated based on a standard deviation of position error plus a standard deviation of bias along an axis of interest. Additionally, the method includes comparing the protection level against an alert limit.

First claim

What is claimed is:

1. A method comprising:
determining a phase of travel of a vehicle by a processor;
determining a probability of hazardously misleading information (PHMI) for the phase of travel by the processor;
determining a protection level (PL) using pseudorange measurements based on the PHMI by the processor, wherein the PL is calculated based on a standard deviation of position error plus a standard deviation of bias along an axis of interest; and
comparing the protection level against an alert limit by the processor.

2. The method of claim 1 , wherein determining the PL further comprises using equation

Q
⁡

(

P
⁢
L

σ

new
,
0

)

+

∑

i
=
1

Nss

⁢

P

fault
,
i

·

Q
⁡

(

P
⁢
L

-

T
i

σ

new
,
i

)

=
PHMI

;

wherein Q(⋅) is a complementary error function;
wherein Nss is a number of different position solutions computed using a subset of a full set of measurements;
wherein P fault,i is a probability of fault mode i;
wherein T i is a fault detection threshold on the fault mode i;
wherein σ new,0 is the standard deviation of position error plus bias of a solution using the full set of measurements;
wherein each position solution using the subset of the full set of measurements is characterized by σ new,i ; and
wherein σ new,i is the standard deviation of position error plus the standard deviation of bias along the axis of interest.

3. The method of claim 1 , further comprising entering a reversionary mode for the phase of travel when the PL exceeds the alert limit.

4. The method of claim 1 , further comprising upper-bounding the standard deviation of bias.

5. The method of claim 4 , wherein upper-bounding the standard deviation of bias comprises multiplying a variance of bias along the axis of interest by a bounding factor.

6. The method of claim 5 , wherein the variance of bias along the axis of interest is calculated using equation bf√{square root over (ΣS i (k) 2 )}, wherein bf is the bounding factor and S i (k) defines one or more projections of pseudorange errors into a navigation solution.

7. The method of claim 6 , wherein the vehicle receives information from a plurality of GNSS satellites.

8. The method of claim 1 , wherein the vehicle is an aircraft.

9. A system comprising:
a receiver configured to receive a plurality of signals transmitted from a plurality of transmitters; and
a processor operatively coupled to the receiver, the processor configured to perform a method of integrity monitoring, wherein executable instructions cause the processor to:
determine a phase of travel of a vehicle;
determine a probability of hazardously misleading information associated with the phase of travel; and
calculate a protection level associated with the probability of hazardously misleading information, wherein the protection level is calculated based on a standard deviation of position error plus a standard deviation of bias along an axis of interest.

10. The system of claim 9 , wherein the processor calculates the protection level using equation

Q
⁡

(

P
⁢
L

σ

new
,
0

)

+

∑

i
=
1

Nss

⁢

P

fault
,
i

·

Q
⁡

(

P
⁢
L

-

T
i

σ

new
,
i

)

=
PHMI

;

wherein Q(⋅) is a complementary error function;

Assignees

• Honeywell Int Inc

Inventors

• Orejas Martin
• Skalicky Jakub
• Raasakka Jussi

Classifications

• G01S19/40 Primary

  Correcting position, velocity or attitude · CPC title

• G01S19/20 Primary

  Integrity monitoring, fault detection or fault isolation of space segment · CPC title