Hybrid GPS/inertially aided platform stabilization system

• US 6,122,595 A
• Filed: 06/17/1999
• Issued: 09/19/2000
• Est. Priority Date: 05/20/1996
• Status: Expired due to Term

• Current Assignee: Benhov GmbH, LLC (Intellectual Ventures LLC)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Varley, Robert F., Maney, John J.
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/334,738
• Time in Patent Office: 460 Days
• Field of Search: 701/213, 701/214, 701/215, 701/220, 701/221, 342/450, 342/357.01, 342/375.02, 342/357.03, 342/357.06, 342/357.11, 342/359
• US Class Current: 701/220
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry
• CPC Class Codes: H01Q 1/18 Means for stabilising antennas on an unstable platform
• CPC Class Codes: H01Q 1/3233 particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
• CPC Class Codes: H01Q 3/08 for varying two co-ordinates of the orientation

Abstract

A hybrid system for stabilizing the attitude of an instrument relative to a dynamic platform includes a plurality of (roll, pitch and yaw) inertial rate sensors, whose outputs are sampled at a rate sufficient to provide real time tracking of changes in orientation of the platform, and a global positioning system (GPS) receiver, whose precision platform attitude output is updated periodically, but at a rate less than the rate of change of attitude of the platform. The inertial rate sensors provide effectively continuous motion (e.g., angular rate) data signals representative of three-dimensional changes in attitude (position derivative signals) of the platform. The inertial rate output are integrated to provide output signals representative of the dynamic orientation of the platform. Sequential outputs of the integration-processing circuitry are also coupled to a sample buffer, which is controllably read-out in accordance with the periodic updates from the GPS receiver. The integrated inertial sensor (attitude) data is compared with the GPS update data to generate error signals which are used to adjust the inertial sensor data. By employing a sample buffer in an inertial sensor output integration feedback loop with the GPS receiver, the hybrid system of the present invention avoids what would otherwise be a staleness problem with the data provided by the GPS receiver.

Claims

1. A system for stably positioning the attitude of an instrument relative to a platform upon which the instrument is mounted, said platform having an orientation that is subject to dynamic variations, comprising:

a platform orientation sensor coupled to said platform and being operative to generate a first signal representative of the orientation of said platform;

at least one angular rate sensor coupled to said platform and being operative to generate a second signal representative of a rate of change of orientation of said platform; and

a signal processor which is operative to adjust said second signal in accordance with said first signal.

2. A system according to claim 1, further including an instrument positioning control mechanism which is operative to control the orientation of said instrument relative to said platform in accordance with said adjusted second signals.

3. A system according to claim 2, wherein said platform orientation sensor comprises a global positioning system (GPS) platform orientation sensor, which periodically generates said first signal at a rate less than that of said second signal, and wherein said signal processor is operative to generate a third signal representative of said orientation of said platform based upon said second signal, and to compare first signals with third signals to derive error signals for adjusting said second signal.

4. A system according to claim 1, wherein said signal processor includes a coordinate system conversion mechanism which is operative to cause said second signals output by said GPS receiver and said second signals to be defined in terms of a common coordinate system.

5. A method of stably positioning an instrument relative to a platform upon which the instrument is mounted, said platform having an orientation subject to dynamic variations, comprising the steps of:

(a) coupled to said platform an inertial angular rate sensor that is operative to generate first signals representative of a rate of change of orientation of said platform;

(b) providing a global positioning system (GPS) receiver which is operative to generate second signals representative of orientation of said platform; and

(c) adjusting said first signals in accordance with said second signals.

6. A method according to claim 5, wherein step (c) further includes performing a coordinate system conversion operation so as to cause said second signals output by said GPS receiver and said first signals generated by said at least one inertial rate sensor to be defined in terms of a common coordinate system.

7. A method of stably orienting an instrument relative to a platform upon which the instrument is mounted, said platform having an orientation that is subject to dynamic variations, comprising the steps of:

(a) attaching to said platform a plurality of angular rate sensors that are operative to provide first, real-time signals representative of rate of change of a respectively different orientation parameter of said platform;

(b) providing a platform orientation sensor which is operative to generate second signals representative of respectively different orientation parameters of said platform;

(c) adjusting said first signals in accordance with said second signals; and

(d) controlling the orientation of said instrument relative to said platform in accordance with said adjusted first signals.

8. A method according to claim 7, wherein said platform orientation sensor is operative to measure the orientation of said platform relative to gravity and geographic north, and wherein said second signals are representative of respectively different instrument gimbal angles of said platform.

9. A method according to claim 7, wherein said platform orientation sensor comprises a global position system (GPS) receiver.

10. A method according to claim 9, wherein said angular rate sensors are operative to generate said first signals representative of rate of roll, pitch and yaw of said platform at a rate sufficient to provide effectively real time tracking of changes in orientation of said platform, and wherein said second signals generated by said GPS receiver are representative of roll, pitch and yaw orientations of said platform and are updated periodically at a rate less than the rate of change of attitude of the platform.