Radar-Assisted Strapdown Inertial Navigation Initial Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current airborne strapdown inertial navigation systems face challenges in initial alignment, especially when GPS is unavailable, due to inaccuracies in using direct position information from radar, which leads to significant alignment errors as distance increases.
Innovation Solution
A method utilizing slant distance and angular position information from radar for initial alignment, constructing a nonlinear measurement equation and employing the unscented Kalman filter to estimate and compensate inertial navigation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct position information from radar is used to construct the measurement equation, then the device complexity is reduced, but the alignment precision deteriorates significantly as distance increases
Solution Approach 1:
The patent transforms the measurement parameters from direct position coordinates to slant distance and angular position. This parameter transformation changes the mathematical characteristics of the measurement model, making it more suitable for radar measurement characteristics and maintaining measurement precision across larger distance ranges without increasing device complexity
Solution Approach 2:
The patent replaces the traditional linearized position measurement model with a nonlinear measurement model based on slant distance and angle. This substitution better reflects the actual radar measurement mechanism and improves alignment precision while keeping the system structure unchanged
2Ease of manufacture
If the linearized position model is used, then the calculation simplicity is improved, but the alignment error increases with distance
Solution Approach 1:
The patent changes the measurement parameters from linearized position coordinates to slant distance and angular position, which better matches radar measurement capabilities and maintains accuracy over larger distances without complicating the model construction process
3Measurement precision
If GPS assisted alignment is used, then the alignment accuracy is improved, but the system reliability deteriorates due to GPS blockage vulnerability
Solution Approach 1:
The patent introduces radar measurement (slant distance and angle) as an intermediary to achieve alignment without relying on GPS. This intermediary measurement method provides a reliable alternative that maintains alignment capability under GPS-denied conditions
Solution Approach 2:
The patent segments the alignment problem into two parts: using radar for coarse alignment through slant distance and angle measurements, and then refining the alignment. This segmentation allows the system to achieve reliable alignment without GPS dependency
Data Source
AI summary
The invention provides a method for initial alignment of radar assisted airborne strapdown inertial navigation system. By calculating the slant distance and angular position between the radar and the airborne inertial navigation equipment, a nonlinear measurement equation for the initial alignment of the radar assisted inertial navigation system is obtained. The unscented Kalman filter algorithm is used to estimate and compensate the error amount of strapdown inertial navigation system to complete the initial alignment task. The significance of the present invention is to provide an in-flight initial alignment solution when the global positioning system is limited, which has fast convergence speed and high estimation accuracy and has high engineering application value.