Precise Estimation and Compensation of Antenna Lever Arm Flexure Using Auxiliary Inertial Sensors to Improve Ultra-Tightly Coupled GPS-IMU and ESM Performance

Paul Quinn, David Lewis, Michael Berarducci and Mikel Miller

Abstract:	Flexure of the body (e.g., aerospace vehicle) lever arm between a GPS antenna and the master inertial measurement unit (IMU) in an ultra-tightly coupled GPS navigation system lowers the receiver’s tracking threshold and degrades its precision navigation accuracy. Likewise, position and velocity errors induced into electronic support measures (ESM) systems due to dynamic lever arm flexure at the antennas degrade ESM emitter geolocation accuracies. A second IMU mounted close to or integrated with the antenna will make flexure of the antenna lever arm observable. In this article, the authors present the development and testing of a least-squares optimal method for combining inertial inputs from two IMUs, and using a simple model of restoring forces to bound long-term drift in the resulting flexure estimate. This method is fundamentally simple and addresses each degree of freedom of flexure separately. The authors present methods that extend the model to six simultaneous degrees of freedom, enabling the system integrator to exploit knowledge of platform flexure modes involving any combination of the three position and three attitude degrees of freedom. Methods for exploiting deterministically changing “static” lever arm position and changing mode characteristic models are also explored.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	951 - 960
Cite this article:	Quinn, Paul, Lewis, David, Berarducci, Michael, Miller, Mikel, "Precise Estimation and Compensation of Antenna Lever Arm Flexure Using Auxiliary Inertial Sensors to Improve Ultra-Tightly Coupled GPS-IMU and ESM Performance," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 951-960.
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