Spinning Projectile Inertial Navigation With Physics-Model Error Bounding
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Solution Overview
Problem
Spinning projectiles face unbounded angular rate measurement errors due to scale factor errors in inertial sensors, leading to inaccurate navigation solutions, as these errors accumulate continuously without cancellation, affecting position, velocity, and attitude estimates.
Innovation Solution
A model-based inertial navigation system that utilizes two aiding sources: a spinning projectile physics model and an upfinding navigation aid to compute navigation corrections, bounding errors in velocity and attitude components by integrating dynamics equations and angular measurements, respectively, to provide accurate trajectory following.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inertial sensors are used to measure angular rates and specific force in spinning projectiles, then navigation data can be obtained, but unbounded angular rate measurement errors accumulate due to scale factor errors in the spin direction
Solution Approach 1:
The patent implements a feedback mechanism where a propagator-estimator filter continuously processes inertial sensor data alongside a spinning projectile physics model to generate navigation corrections. This closed-loop feedback system detects and corrects accumulated angular rate errors by comparing predicted versus actual projectile states, thereby bounding the unbounded error growth that would otherwise occur due to gyroscope scale factor errors during high-speed rotation
Solution Approach 2:
The patent introduces a propagator-estimator filter as an intermediary processing layer between the inertial sensors and the navigation solution. This intermediary component acts as a mediator that reconciles the conflicting data from spinning inertial sensors by filtering and correcting the measurements through a physics-based model, thereby eliminating the direct harmful effect of scale factor errors on navigation accuracy
2Reliability
If a spinning projectile physics model and upfinding navigation aid are integrated to compute navigation corrections, then velocity and attitude errors can be bounded, but the system complexity increases
Solution Approach 1:
The patent merges multiple navigation aiding sources (spinning projectile physics model, upfinding navigation aid, and inertial sensor data) into a unified propagator-estimator filter framework. By combining these diverse data sources and processing them through a single integrated filter, the system achieves bounded velocity and attitude errors while avoiding the complexity of managing separate correction systems for each data source
Solution Approach 2:
The propagator-estimator filter serves multiple functions simultaneously: it processes inertial sensor data, applies physics model corrections, integrates upfinding navigation aid measurements, and generates comprehensive navigation corrections for position, velocity, and attitude. This multi-functional approach consolidates what would otherwise require multiple separate systems into a single versatile navigation solution
Data Source
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AI summary
Model based inertial navigation for a spinning projectile is provided. In one embodiment, a navigation system comprises: a strapdown navigation processor; a propagator-estimator filter, the processor inputs inertial sensor data and navigation corrections from the filter to generate a navigation solution comprising projectile velocity and attitude estimates; an upfinding navigation aid that generates an angular attitude measurement indicative of a roll angle; and a physics model performing calculations utilizing dynamics equations for a rigid body, the model inputs 1) projectile state estimates from the navigation solution and 2) platform inputs indicative of forces acting on a projectile platform, and outputs a set of three orthogonal predicted translational acceleration measurements based on the inputs; the filter comprises a measurement equation associated with the physics model and the upfinding navigation aid and calculates the navigation corrections as a function of the navigation solution, the predicted translational acceleration measurements, and attitude measurement.