RAIV Hybrid Filter Set for Terrain-Resistant Vertical Navigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing navigation solutions for uncrewed aircraft systems (UAS) and urban air mobility (UAM) vehicles face challenges in accurately handling terrain variations, leading to inconsistencies in inertial and radar-based measurements, which can result in failure to meet navigation requirements during landing.
Innovation Solution
A system comprising a radar altimeter, an aided inertial navigation system (INS) or Attitude and Heading Reference System (AHRS), an air data system, and a processor with a barometric inertial vertical (BIV) hybrid filter and a radar altimeter inertial vertical (RAIV) hybrid filter set. The RAIV hybrid filter set operates with multiple hybrid filters in parallel, each processing partially overlapping, time-limited intervals of input measurements to mitigate terrain variation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If terrain uncertainty is included in the hybrid filter as a state, then measurement inconsistencies are addressed, but the uncertainty of estimated vehicle kinematic states increases, reducing performance
Solution Approach 1:
The filter is segmented into multiple parallel instances, each processing a subset of measurements over a limited time interval. This segmentation allows the system to address terrain variations locally in time without propagating uncertainty across the entire measurement sequence, thus maintaining estimation accuracy while handling measurement inconsistencies.
Solution Approach 2:
The system performs preliminary filtering operations in parallel across multiple filter instances before combining results. By pre-processing measurements through multiple independent filter slots with staggered intervals, the system prepares refined estimates that reduce uncertainty before final integration, improving overall measurement consistency without sacrificing precision.
2Reliability
If a terrain database is used together with horizontal vehicle position information to compensate for terrain variations, then measurement inconsistencies are reduced, but the navigation system complexity significantly increases
Solution Approach 1:
The solution extracts and eliminates the need for complex terrain databases and horizontal position integration by focusing solely on vertical parameter estimation. The parallel filter slots process vertical measurements directly without requiring external terrain information or horizontal position data, thereby reducing measurement inconsistencies while significantly simplifying the navigation system architecture.
Solution Approach 2:
Instead of relying on expensive and complex terrain databases, the system uses multiple inexpensive, temporary filter instances that process measurements over limited time intervals. These short-lived filter slots are created and discarded as needed, providing terrain variation compensation through computational redundancy rather than through complex data structures or external databases.
3Measurement precision
If multiple hybrid filters operate in parallel with time-limited staggered intervals, then terrain variation effects are mitigated, but computational resources increase
Solution Approach 1:
The parallel filter slots operate with periodic, time-limited intervals rather than continuously. Each filter instance is activated for a specific duration and then deactivated, creating a periodic pattern of computation. This approach maintains high measurement precision through multiple parallel processing windows while reducing overall computational energy consumption compared to continuous operation of a single filter or perpetual parallel operation.
Data Source
AI summary
A system comprises a radar altimeter that produces range-to-ground measurements; an aided INS or AHRS that produces vertical acceleration, roll, and pitch measurements; an air data system that produces barometric altitude measurements; and a processor including a BIV hybrid filter, and a RAIV hybrid filter set. The BIV hybrid filter receives the vertical acceleration measurements and the barometric altitude measurements. The RAIV hybrid filter set receives input measurements comprising the vertical acceleration, roll, and pitch measurements, BIV hybrid filter statistics, and the range-to-ground measurements. The RAIV hybrid filter set comprises a plurality of hybrid filters that operate in parallel with each other in respective filter slots. A hybrid filter in each filter slot operates on partially overlapping, time limited staggered intervals of the input measurements, with respect to other hybrid filters in other filter slots. Estimated vertical navigation statistics are computed based on input statistics processed in the filter slots.