Radar Navigator Alignment Using Doppler Echo Analysis
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Solution Overview
Problem
Current GPS-aided Inertial Navigation Systems (INS) struggle to accurately correct heading errors during straight, level, and constant velocity flight, requiring additional instrumentation or maneuvers like S-turns, which are disruptive and costly, especially for aircraft like dirigibles and blimps.
Innovation Solution
A radar system determines the direction of flight by analyzing Doppler frequency and bandwidth of radar echoes, allowing for the correction of heading errors without additional instrumentation, by identifying the squint angle with maximum Doppler frequency and minimum bandwidth, and aligning the IMU accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional GPS-aided INS is used during straight, level, constant velocity flight, then the system operates normally, but heading error becomes unobservable and cannot be corrected
Solution Approach 1:
The patent applies artificial horizontal accelerations (vibrations) to the platform to make heading error observable. By introducing controlled oscillatory motions, the system generates measurable effects that reveal heading errors without requiring complex maneuvers like S-turns, thus maintaining operational simplicity while enabling correction.
Solution Approach 2:
The patent changes the motion parameters of the platform by introducing controlled horizontal accelerations. This transforms the system from a state where heading error is unobservable (constant velocity) to a state where it becomes observable through the introduced accelerations, enabling error correction while maintaining flight stability.
2Measurement precision
If S-turn maneuvers are performed to correct heading error, then alignment accuracy is improved, but mission disruption and passenger discomfort increase
Solution Approach 1:
Instead of performing disruptive S-turn maneuvers, the patent uses small-amplitude oscillatory motions to generate the necessary horizontal accelerations for making heading error observable. This achieves alignment accuracy while minimizing disturbance to the mission and passenger comfort.
Solution Approach 2:
The patent applies partial action by using small, controlled oscillations rather than full S-turn maneuvers. This provides just enough acceleration to make heading error observable and correctable, achieving the necessary alignment accuracy without the excessive disruption of complete S-turns.
3Measurement precision
If additional instruments like digital flux-gate compass are used to detect platform attitude, then heading error measurement capability is improved, but system complexity and cost increase
Solution Approach 1:
The patent makes the existing radar system self-sufficient by enabling it to measure its own heading errors through analysis of radar echo Doppler characteristics. This eliminates the need for additional heading measurement instruments, maintaining measurement capability while reducing system complexity.
Solution Approach 2:
The patent enables the radar system to perform multiple functions: its primary surveillance function plus heading error measurement and correction. By making the radar multi-functional, the system achieves heading measurement capability without adding dedicated instruments, thus reducing overall system complexity.
4Measurement precision
If GPS-based Attitude Determination Unit with multiple antennas is deployed, then platform attitude determination accuracy is improved, but hardware requirements and platform burden increase
Solution Approach 1:
The patent enables the existing radar system to determine its own attitude and heading information by analyzing Doppler characteristics of radar echoes. This self-service capability eliminates the need for additional GPS antennas and ADU hardware, maintaining attitude determination accuracy while reducing hardware requirements.
Solution Approach 2:
The patent merges the attitude determination function with the existing radar system. By combining these functions, the system achieves accurate attitude determination without the need for separate ADU hardware and multiple GPS antennas, thus reducing overall hardware requirements and platform burden.
5Reliability
If higher grade navigation grade IMU is used instead of tactical grade IMU, then alignment maintenance capability is improved, but cost and platform burden increase significantly
Solution Approach 1:
The patent implements a feedback mechanism using radar Doppler measurements to detect and correct heading errors in real-time. This continuous feedback allows tactical grade IMUs to maintain alignment accuracy that would otherwise require more expensive navigation grade IMUs, improving reliability while reducing cost and platform burden.
Solution Approach 2:
The system uses the radar to provide self-correction of heading errors, enabling the tactical grade IMU to maintain alignment without the need for upgrading to navigation grade IMU. This self-service capability improves alignment maintenance while avoiding the increased cost and platform burden of higher-grade IMUs.
6Measurement precision
If ground alignment is performed to achieve initial alignment, then alignment accuracy is improved, but operational flexibility and response time decrease
Solution Approach 1:
The patent uses artificial oscillations to accelerate the alignment process, enabling rapid initial alignment without requiring extended ground alignment periods. This achieves sufficient alignment accuracy while dramatically reducing the time required, improving operational flexibility and response time.
Solution Approach 2:
The patent changes the motion state of the platform by introducing controlled oscillations during alignment. This transforms the alignment process from a static ground-based procedure to a dynamic in-flight process, achieving accurate alignment quickly and enabling immediate operational response.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables accurate and efficient initial alignment of GPS-aided IMU navigators during flight, reducing the need for disruptive maneuvers and additional hardware, while maintaining alignment accuracy for both tactical and navigation-grade IMUs.
Implementation Method 1
determining a direction of flight of the aircraft based on a Doppler frequency and a Doppler bandwidth of a plurality of radar echoes
Data Source
AI summary
The various technologies presented herein relate to the determination of and correction of heading error of platform. Knowledge of at least one of a maximum Doppler frequency or a minimum Doppler bandwidth pertaining to a plurality of radar echoes can be utilized to facilitate correction of the heading error. Heading error can occur as a result of component drift. In an ideal situation, a boresight direction of an antenna or the front of an aircraft will have associated therewith at least one of a maximum Doppler frequency or a minimum Doppler bandwidth. As the boresight direction of the antenna strays from a direction of travel at least one of the maximum Doppler frequency or a minimum Doppler bandwidth will shift away, either left or right, from the ideal situation.