Second order complementary global positioning system/inertial navigation system blending filter

Abstract

A second-order filter that blends accurate position information from a one source, and velocity information from another source, both suitably scaled, in a second-order complementary filter. The filter is arranged such that an internal integrator maintains a value that represents the difference in the rate of change of the accurate position information, and the velocity input of the other source. This velocity difference is applied to another integrator outside the filter, whose initial condition is the position error between the two sources to the second order filter. The output of this latter integrator is a correction signal that grows at a rate equal and opposite to the rate of error build-up of position data from the source whose velocity is used in the second order filter. This correction signal is summed with the original position signal. In addition, the output of the second order filter may be used as a highly accurate position signal.

Description

[0001] This application claims priority to Provisional Application, Serial No. 60, 221,314, filed Jul. 28, 2000.[0002] 1. Field of the Invention (Technical Field)[0003] This invention relates to navigation systems, and, in particular, airborne navigation and guidance systems utilizing the computation of position and velocity for automatic guidance.[0004] 2. Background Art[0005] Modern navigation systems utilize extremely accurate signals from a constellation of satellites that comprise the Global Positioning System (GPS) to compute position. However, while such signals provide excellent long-term position accuracy, they are noisy in the short-term. This is particularly true of the velocity data provided. Velocity data as well as position data is required to provide smooth, stable guidance. A further disadvantage of GPS is that the data rate of the position solution is lower than desirable for smooth, stable aircraft guidance.[0006] Current practice is to augment the GPS signals with...

AI Technical Summary

Problems solved by technology

However, while such signals provide excellent long-term position accuracy, they are noisy in the short-term.

A further disadvantage of GPS is that the data rate of the position solution is lower than desirable for smooth, stable aircraft guidance.

The INS signals exhibit excellent short-term accuracy and smoothness, but they suffer from long-term drift that produces position errors that are unbounded with time.

This prior art solution is very costly and complex.

Kalman filters may solve the problem of correcting the INS data for drift and drift rate, but that is not necessarily their primary purpose.

However, such filters cannot provide correction for INS drift rate, and may limit the effectiveness of the guidance system in which they are used.

However, such filters to not use the velocity error that may be available in such devices to correct for drift rate of the INS.

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