GPS Harmonic Spin Rate Tracking for Artillery Guidance
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Solution Overview
Problem
Conventional methods for determining the spin rate of artillery vehicles, such as precalculated aiding data and inertial sensors, suffer from significant errors, weight and volume constraints, and increased complexity, particularly in high-g-force environments, and require lengthy initialization times, which are critical in applications with short flight times like artillery shell guidance.
Innovation Solution
A system that uses a GPS receiver and antenna to derive the spin rate from harmonics produced in GPS signals, allowing for accurate spin rate measurement with minimal weight and volume impact, and reducing systemic complexity by eliminating the need for independent inertial sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inertial sensors (gyroscopes and accelerometers) are used to determine spin rate, then spin rate measurement capability is provided, but weight and volume of the vehicle increase
Solution Approach 1:
The patent extracts the spin rate measurement function from the inertial sensor system and implements it through GPS signal processing instead. By taking out the need for physical inertial sensors and using only the GPS receiver already present for navigation, the system eliminates the weight and volume penalty while maintaining spin rate measurement capability
Solution Approach 2:
The GPS receiver is made multi-functional by using it not only for navigation but also for spin rate determination. The same GPS antenna and receiver process both navigation signals and spin rate measurements by analyzing harmonic frequencies, eliminating the need for dedicated inertial sensors
2Measurement precision
If inertial sensors are used to determine spin rate, then spin rate data is obtained, but device complexity increases
Solution Approach 1:
The patent merges the spin rate measurement function with the existing GPS navigation system. By combining these functions into a single integrated system that processes GPS signals for both navigation and rotation rate determination, the overall device complexity is reduced compared to having separate inertial sensor systems
Solution Approach 2:
The GPS receiver performs multiple functions including navigation and spin rate measurement. This multi-functionality reduces system complexity by eliminating the need for separate dedicated sensors and processing systems for spin rate
3Ease of manufacture
If precalculated aiding data is used to determine spin rate, then spin rate can be calculated, but large errors occur in off-nominal conditions
Solution Approach 1:
The system uses actual measured GPS signal harmonics from the vehicle's own motion to determine spin rate, rather than relying on precalculated data based on models. This self-measuring approach adapts to actual flight conditions including off-nominal scenarios, providing accurate spin rate data without requiring precalculated aiding data
4Measurement precision
If Doty et al.'s GPS system is used to track rotation angle, then rotation tracking is achieved, but additional time is required for initialization and spin rate search
Solution Approach 1:
The system performs preliminary action by directly tracking spin rate harmonics from the outset rather than requiring an initialization phase to search for or estimate spin rate. The GPS receiver is configured to acquire and track the harmonic frequencies corresponding to vehicle rotation from the beginning of signal reception
Solution Approach 2:
The invention skips the time-consuming initialization and spin rate search steps required by Doty et al.'s system. By directly measuring spin rate through harmonic frequency analysis of GPS signals, the system rushes through the acquisition process without the lengthy initialization phase
Data Source
AI summary
A spin rate tracking system comprising a guidance system suitable for adjusting a flight path of a vehicle based on a spin rate of the vehicle, a signal reception system configured for receiving signal information from a global navigation system wherein a spin rate of the vehicle is derived from a substantially harmonic pattern produced amongst a global navigation signal.