Multi-IMU guidance system and methods for high-accuracy location and guidance performance in GPS denied and/or degraded environments

• US 10,527,427 B1
• Filed: 01/12/2018
• Issued: 01/07/2020
• Est. Priority Date: 10/10/2017
• Status: Active Grant

• Current Assignee: Orbital Research, Inc.
• Original Assignee: Orbital Research, Inc.
• Inventors: Jankowski, Michael, Rapp, Edward J.
• Primary Examiner(s): Marc, Mcdieunel
• Application Number:
  US15/869,208
• Time in Patent Office: 725 Days
• CPC Class Codes: F42B 15/01 Arrangements thereon for guidance or control steering arrangements F42B10/60; aircraft flight control B64C; guidance systems other than those installed aboard F41G7/00, F41G9/00; locating by use of radio or other waves G01S; flight control in general G05D1/00; computer aspects G06]
• CPC Class Codes: F42B 30/10 Mortar projectiles
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 21/1654 with electromagnetic compass

Abstract

Systems and methods for providing location and guidance, and more particularly for providing location and guidance in environments where global position systems (GPS) are unavailable or unreliable (GPS denied and/or degraded environments), utilizing inertial measurement units (IMUs) to provide such location and guidance. A series of low-accuracy or low-resolution IMUs, in combination, are utilized to provide high-accuracy or high-resolution location and guidance results.

Claims

1. A guidance system adapted for accurately providing location and guidance in a global positioning system (GPS) denied and/or degraded environment, the system comprising:

at least one printed circuit board (PCB) comprising an upper surface, a lower surface and a plurality of inertial measurement units (IMUs) mounted on at least one of the surfaces, each IMU having a signal and comprising at least one three-axis accelerometer and/or at least one three-axis gyroscope, the IMUs adapted to be coupled together via firmware;

a processor adapted to receive the signal from each IMU; and

an algorithm comprised in the processor, the algorithm adapted to synchronize the signals from each of the IMUs, calculate a bias and a drift in the signal of each IMU, and to provide a guidance metric representative of the absolute or relative location of a munition guided by the guidance system and based on the signals of each of the IMUs.

2. The system of claim 1, wherein the at least four IMUs are divided into subgroups of four IMUs, each IMU of each subgroup adapted to be mounted to the at least one PCB in a different spatial orientation in the y- and z-axes relative to the surface of the PCB to which the IMUs are mounted and the different orientation of each IMU is adapted to offset the bias and drift of each IMU, where the x-axis is perpendicular to the surface of the PCB.

3. The system of claim 2, wherein the guidance system is adapted to be automatically calibrated by sampling the signal from each IMU in sequence, comparing the signals from each of the IMUs, and correlating those signals with respect to time and measured values from each IMU.

4. The system of claim 3, comprising at least one additional PCB adapted to be stacked with the at least one PCB with each of the IMUs coupled together across each of the PCBs creating a multiplied IMU measurement resolution based on the signal of each IMU, and the IMUs each provide redundant measurements.

5. The system of claim 4, wherein the system comprises at least one temperature sensor and each IMU further comprises at least one magnetometer, and the system is further adapted to compensate for temperature differences between each IMU.

6. The system of claim 5, further comprising a communication element adapted to transmit the guidance metric to a remote location for tracking of the munition in flight by a remote user.

7. The system of claim 1, wherein the guidance system exhibits an angular random walk less than or equal to 0.09°

/√

hour.

8. The system of claim 1, wherein a plurality of the individual IMUs has an angular random walk (ARW) of 0.78°

/√

hour or less, but the guidance system as a whole exhibits an angular random walk less than about ¼

the ARW of any individual IMU.

9. A guidance system adapted for accurately providing location and guidance in a global positioning system (GPS) denied and/or degraded environment, the system comprising:

at least one printed circuit board (PCB) comprising an upper surface, a lower surface and a plurality of inertial measurement units (IMUs) mounted on at least one of the surfaces, each IMU having a signal and comprising at least one three-axis accelerometer and/or at least one three-axis gyroscope, the IMUs adapted to be coupled together via firmware;

a processor adapted to receive the signal from each IMU; and

an algorithm comprised in the processor, the algorithm adapted to synchronize the signals from each of the IMUs, calculate a bias and a drift in the signal of each IMU, and to provide a guidance metric representative of the absolute or relative location of a munition guided by the guidance system and based on the signals of each of the IMUs,

wherein the guidance system exhibits an angular random walk less than or equal to 0.09°

/√

hour.

10. The system of claim 9, wherein the at least four IMUs are divided into subgroups of four IMUs, each IMU of each subgroup adapted to be mounted to the at least one PCB in a different spatial orientation in the y- and z-axes relative to the surface of the PCB to which the IMUs are mounted and the different orientation of each IMU is adapted to offset the bias and drift of each IMU, where the x-axis is perpendicular to the surface of the PCB.

11. The system of claim 10, wherein the guidance system is adapted to be automatically calibrated by sampling the signal from each IMU in sequence, comparing the signals from each of the IMUs, and correlating those signals with respect to time and measured values from each IMU.

12. The system of claim 11, comprising at least one additional PCB adapted to be stacked with the at least one PCB with each of the IMUs coupled together across each of the PCBs creating a multiplied IMU measurement resolution based on the signal of each IMU, and the IMUs each provide redundant measurements.

13. The system of claim 12, wherein the system comprises at least one temperature sensor and each IMU further comprises at least one magnetometer, and the system is further adapted to compensate for temperature differences between each IMU.

14. The system of claim 13, further comprising a communication element adapted to transmit the guidance metric to a remote location for tracking of the munition in flight by a remote user.

15. A guidance system adapted for accurately providing location and guidance in a global positioning system (GPS) denied and/or degraded environment, the system comprising:

at least one printed circuit board (PCB) comprising an upper surface, a lower surface and a plurality of inertial measurement units (IMUs) mounted on at least one of the surfaces, each IMU having a signal and comprising at least one three-axis accelerometer and/or at least one three-axis gyroscope, the IMUs adapted to be coupled together via firmware;

a processor adapted to receive the signal from each IMU; and

an algorithm comprised in the processor, the algorithm adapted to synchronize the signals from each of the IMUs, calculate a bias and a drift in the signal of each IMU, and to provide a guidance metric representative of the absolute or relative location of a munition guided by the guidance system and based on the signals of each of the IMUs,

wherein a plurality of the individual IMUs has an angular random walk (ARW) of 0.78°

/√

hour or less, but the guidance system as a whole exhibits an angular random walk less than about ¼

the ARW of any individual IMU.

16. The system of claim 15, wherein the at least four IMUs are divided into subgroups of four IMUs, each IMU of each subgroup adapted to be mounted to the at least one PCB in a different spatial orientation in the y- and z-axes relative to the surface of the PCB to which the IMUs are mounted and the different orientation of each IMU is adapted to offset the bias and drift of each IMU, where the x-axis is perpendicular to the surface of the PCB.

17. The system of claim 16, wherein the guidance system is adapted to be automatically calibrated by sampling the signal from each IMU in sequence, comparing the signals from each of the IMUs, and correlating those signals with respect to time and measured values from each IMU.

18. The system of claim 17, comprising at least one additional PCB adapted to be stacked with the at least one PCB with each of the IMUs coupled together across each of the PCBs creating a multiplied IMU measurement resolution based on the signal of each IMU, and the IMUs each provide redundant measurements.

19. The system of claim 18, wherein the system comprises at least one temperature sensor and each IMU further comprises at least one magnetometer, and the system is further adapted to compensate for temperature differences between each IMU.

20. The system of claim 19, further comprising a communication element adapted to transmit the guidance metric to a remote location for tracking of the munition in flight by a remote user.