GPS-aided inertial navigation method and system

1. A GPS-aided inertial navigation method comprising: providing multiple sensors including multiple inertial measurement units (IMUs) and at least one global positioning system (GPS), each GPS comprising a receiver and an antenna, said IMUs and at least one GPS being fixedly installed on a rigid body, said at least one GPS providing position and velocity solutions; and

providing a computer with navigation software;

wherein the computer performs the following activities:

(a) interfacing with all IMUs and all GPS receivers;

(b) running, in parallel, multiple standard inertial navigation (IN) schemes, one per each IMU;

(c) computing a mean of all the INs, thus obtaining a fused IN solution for a mean location of the IMUs;

(d) computing a mean of all the GPS solutions, thus obtaining a fused GPS solution for a mean location of the GPS antennas;

(e) applying lever-arm corrections, with the vector from the mean location of the IMUs to the mean location of the GPS antennas;

(f) feeding the fused IN solution and the lever-arm corrected fused GPS solution, regardless of whether the fused GPS solution is based on a single GPS or multiple GPSs of the at least one GPS, to a single navigation filter, and the single navigation filter operates with the same number of filter states as it would with a single IMU/IN and a single GPS;

(g) computing angular acceleration of the rigid body; and

(h) running an IMU/IN/GPS correction module which, based on rigid-body physics and on the computation of the angular acceleration of the rigid body, computes appropriate individual:

(i) linear acceleration and angular rate corrections for each IMU,

(ii) position, velocity and attitude corrections for each IN, and

(iii) position, velocity, attitude, linear acceleration and angular rate aiding-message for each GPS receiver.

2. The method of claim 1 , wherein the rigid body's angular acceleration is computed using a least-squares method, using data from all the IMUs.

3. The method of claim 2 , wherein, for computation purposes, the IMUs are paired in all possible IMU pairs and the least-squares method uses linear acceleration and angular rate data from all of said IMU pairs.

4. The method of claim 1 , wherein individual IMU-corrections are computed as increments to prior corrections, and mathematically integrated.

5. The method of claim 1 , wherein individual IMU-corrections are computed entirely anew after each navigation filter update, without mathematical integration.

6. The method of claim 1 , wherein the computation of individual corrections to all the sensors uses:

a. angular rate and angular acceleration lever-arm correction terms, and

b. filter-updated and lever-corrected linear accelerations at the individual locations of the IMUs, to define either local IMU correction-increments or to define whole local IMU corrections.

7. The method of claim 1 , wherein at least one of the IMUs and the GPS antennas are not co-located.

8. The method of claim 7 , wherein all of the IMUs and the GPS antennas are not co-located.

9. The method of claim 1 , wherein the number of IMUs and the number of GPSs are independent of each other.

10. A GPS-aided inertial navigation system (INS) comprising multiple sensors including multiple inertial measurement units (IMUs) and a computer with navigation software, and at least one global positioning system (GPS), each GPS comprising a receiver and an antenna, said IMUs and at least one GPS being fixedly installed on a rigid body, said at least one GPS providing position and velocity solutions, and wherein the computer is configured to:

(a) interface all IMUs and all GPS receivers;

(b) run, in parallel, multiple standard inertial navigation (IN) schemes, one per each IMU;

(c) compute a mean of all INs, thus obtaining a fused IN solution for a mean location of the IMUs;

(d) compute a mean of all the GPS solutions, thus obtaining a fused GPS solution for a mean location of the GPS antennas;

(e) apply lever-arm corrections, with the vector from the mean location of the IMUs to the mean location of the GPS antennas;

(f) feed the fused IN solution and the lever-arm corrected fused GPS solution regardless of whether the fused GPS solution is based on a single GPS or multiple GPSs of the at least one GPS, to a single navigation filter, and the single navigation filter operates with the same number of filter states as it would with a single IMU/IN and a single GPS;

(g) compute angular acceleration of the rigid body; and

(h) run an IMU/IN/GPS correction module which, based on rigid-body physics and on the computation of the angular acceleration of the rigid body, computes appropriate individual:

(i) linear acceleration and angular rate corrections for each IMU,

(ii) position, velocity and attitude corrections for each IN, and

(iii) position, velocity, attitude, linear acceleration and angular rate aiding-messages for each GPS receiver.

11. The system of claim 10 , wherein the computer computes the rigid body's angular acceleration using a least-squares method, using data from all the IMUs.

12. The system of claim 11 , wherein using data from all the IMUs further comprises using respective locations of the IMUs fixedly installed on the rigid body.