GPS/INS sensor fusion using GPS wind up model
A method of stabilizing an inertial navigation system (INS), includes the steps of: receiving data from an inertial navigation system; and receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites; calculating a phase wind up correction; correcting at least one of the finite number of carrier phase observables using the phase wind up correction; and calculating a corrected IMU attitude or velocity or position using the corrected at least one of the finite number of carrier phase observables; and performing a step selected from the steps consisting of recording, reporting, or providing the corrected IMU attitude or velocity or position to another process that uses the corrected IMU attitude or velocity or position. A GPS stabilized inertial navigation system apparatus is also described.
1. A method of stabilizing an inertial navigation system (INS), comprising the steps of:
performing the following steps in any order:
receiving data from an inertial navigation system having an inertial measurement unit (IMU); and
receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites;
performing the following series of calculations:
calculating a phase wind up correction;
correcting at least one of said finite number of carrier phase observables using said phase wind up correction; and
calculating a corrected IMU attitude or velocity or position using said corrected at least one of said finite number of carrier phase observables; and
performing a step selected from the steps consisting of recording said corrected IMU attitude or velocity or position, reporting said corrected IMU attitude or velocity to a user, and providing said corrected IMU attitude or velocity or position to another process that uses the corrected IMU attitude or velocity or position.
2. The method of stabilizing an inertial navigation system of claim 1 , further comprising the step of providing said corrected IMU attitude or velocity or position to said INS.
3. The method of stabilizing an inertial navigation system of claim 1 , wherein said step of calculating a corrected IMU attitude or velocity or position includes calculating a corrected IMU attitude or velocity or position using said corrected at least one of said finite number of carrier phase observables with full state observability.
4. The method of stabilizing an inertial navigation system of claim 1 , wherein said steps of calculating a phase wind up correction and correcting at least one of said finite number of carrier phase observables using said phase wind up correction are performed using the following equations:
ϕ
xi
=
tan
-
1
(
d
y
d
x
)
,
and
ϕ
xi
-
ϕ
_
xi
=
H
MGEKF
H
ϕ
i
H
D
δ
x
,
where
H
MGEKF
=
-
F
tan
-
1
(
Ψ
)
Ψ
,
and
H
ϕ
i
=
[
sin
(
β
~
i
)
-
cos
(
β
~
i
)
0
]
.
5. The method of stabilizing an inertial navigation system of claim 1 , wherein said steps of calculating a phase wind up correction and correcting at least one of said finite number of carrier phase observables using said phase wind up correction are performed using the following equations:
ϕ
_
xi
=
tan
-
1
(
D
_
y
D
_
x
)
,
and
ϕ
xi
-
ϕ
_
xi
=
H
A
H
B
H
D
δ
x
,
where
H
A
=
2
1
+
(
D
_
y
D
_
x
)
2
D
_
y
D
_
x
,
and
H
B
=
[
1
D
_
x
-
D
_
y
D
_
x
2
0
]
.
6. The method of stabilizing an inertial navigation system of claim 1 , wherein said step of receiving a finite number of carrier phase observables comprises receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites using a GPS receiver having a plurality of GPS antennas disposed at different angles with different dipole definitions in a coordinate reference system and wherein said step of performing the following series of calculations includes calculating a phase wind up correction for each of said plurality of GPS antennas disposed at different angles.
7. The method of stabilizing an inertial navigation system of claim 1 , wherein said step of receiving a finite number of carrier phase observables comprises receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites using a plurality of GPS antennas disposed substantially in a circle and wherein said step of performing the following series of calculations includes calculating includes calculating a phase wind up correction for each of said plurality of GPS antennas disposed substantially in a circle.
8. The method of stabilizing an inertial navigation system of claim 1 , wherein a GPS receiver having at least one GPS antenna is present on a first vehicle, and a second GPS receiver having at least one GPS antenna is configured to perform the method of claim 1 on a second vehicle different from said first vehicle, and further comprising a step of using a single or double differenced carrier phase measurement to provide a range between said first and said second vehicles.
9. The method of stabilizing an inertial navigation system of claim 1 , wherein said step of calculating a corrected IMU attitude or velocity or position provides an enhanced accuracy yaw angle.
10. The method of stabilizing an inertial navigation system of claim 1 , wherein said step of calculating a corrected IMU attitude or velocity or position includes calculation of an Extended Kalman Filter (EKF) or of a Square Root Information Filter (SRIF).
11. A GPS stabilized inertial navigation system apparatus comprising:
at least one GPS receiver having at least one GPS antenna;
an inertial navigation system (INS) having an inertial measurement unit (IMU);
a data processor communicatively coupled to said at least one GPS receiver and said IMU, said data processor configured to receive a plurality of GPS carrier phase observables from said GPS receiver and attitude and velocity data from said IMU, said data processor including a module having instructions in machine-readable form recorded therein, said data processor configured to perform, when operating under the control of said instructions, a process comprising the steps of:
calculating a phase wind up correction;
correcting at least one of said finite number of carrier phase observables using said phase wind up correction; and
calculating a corrected IMU attitude or velocity or position using said corrected at least one of said finite number of carrier phase observables; and
at least one device selected from the group of devices consisting of a device configured to record said corrected IMU attitude or velocity or position, a device configured to report said corrected IMU attitude or velocity or position to a user, and a device configured to provide said corrected IMU attitude or velocity or position to another process that uses the corrected IMU attitude or velocity or position.
12. The GPS stabilized inertial navigation system apparatus of claim 11 , wherein said INS is configured to receive said corrected IMU attitude or velocity or position to correct an INS attitude or velocity or position.
13. The GPS stabilized inertial navigation system apparatus of claim 11 , wherein said data processor is configured to calculate a corrected IMU attitude or velocity or position with full state observability.
14. The GPS stabilized inertial navigation system apparatus of claim 11 , further comprising a plurality of GPS antennas disposed at different angles.
15. The GPS stabilized inertial navigation system apparatus of claim 11 , further comprising a plurality of GPS antennas disposed substantially in a circle.
16. The GPS stabilized inertial navigation system apparatus of claim 11 , wherein said data processor is configured to provide an enhanced accuracy yaw angle.