Rotational Position Tracking for Spinning Projectiles
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Solution Overview
Problem
Guiding a spinning projectile, such as an artillery shell, requires knowledge of its rotational orientation in addition to spatial position for precise flight corrections, as the fins spin with the projectile, necessitating a method to determine and utilize its rotational position effectively.
Innovation Solution
The described techniques utilize a satellite positioning system to determine the rotational position of the projectile by averaging independent calculations of the antenna's 'up' time relative to multiple GPS satellites, smoothing noise and providing a reliable reference for flight control, applicable with both coarse/acquisition C/A code and precise P(Y) code signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If satellite positioning system signals are used to determine spatial position, then spatial position accuracy is improved, but rotational orientation information is lost
Solution Approach 1:
The patent uses an intermediary approach by introducing a signal processing mechanism that extracts rotational orientation information from the satellite positioning signals. The receiver processes the satellite signals to detect power modulation caused by antenna rotation, thereby deriving rotational orientation data without requiring separate sensors. This intermediary processing step bridges the gap between spatial position determination and rotational orientation measurement.
2Measurement precision
If power modulation tracking is used to determine rotational position, then rotational orientation accuracy is improved, but signal processing complexity increases
Solution Approach 1:
The patent extracts only the necessary rotational orientation information from the satellite signals by isolating the power modulation component. Rather than processing the entire signal spectrum, the system specifically tracks the amplitude/power variations caused by antenna rotation during projectile spin. This extraction approach focuses computational resources on the relevant signal characteristic, reducing overall processing complexity while maintaining rotational measurement accuracy.
Solution Approach 2:
The system employs feedback mechanisms through phase-locked loops (PLL) and frequency-locked loops (FLL) that continuously monitor and adjust tracking of the power modulation signal. These feedback circuits automatically lock onto the modulation frequency and phase, maintaining accurate rotational position detection without requiring complex computational algorithms. The feedback approach simplifies processing by using analog/digital control loops rather than intensive digital signal processing.
Data Source
AI summary
Apparatus and methods determine the rotational position of a spinning object. A satellite positioning system can be used to determine the spatial position of an object, which in turn can be used to guide the object. However, when the object is spinning, such as an artillery shell, then the rotational orientation should be known in order to properly actuate the control surfaces, such as fins, which will also be spinning.