Initial Heading Alignment Using Virtual Trajectory Matching
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Solution Overview
Problem
Existing methods for determining the initial heading angle in integrated GNSS/INS systems are costly, require additional hardware, and are not applicable to vehicles moving non-tangentially to their body axis, particularly affecting aerial and sea vehicles.
Innovation Solution
A method involving defining multiple virtual instances of a mobile body with random initial heading angles, propagating these instances using inertial navigation data, and comparing their positions to absolute measurements to determine the best-fit instance for accurate heading estimation without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple antennas are used to estimate orientation from double differenced phase measurements, then heading alignment accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates multiple virtual instances of the mobile body, each with a different assumed initial heading angle. These virtual instances propagate through the same inertial navigation data to generate multiple candidate trajectories. The system then compares these trajectories against absolute position measurements to identify the best-fit initial heading, eliminating the need for multiple physical antennas while achieving accurate heading alignment.
Solution Approach 2:
The patent divides the heading estimation problem into multiple independent virtual instances, each representing a possible initial heading angle. By segmenting the solution space into discrete candidate headings and evaluating them separately through propagation and comparison, the system achieves accurate heading determination without requiring additional physical sensors or antennas.
2Measurement precision
If magnetometers are used to measure magnetic field direction, then absolute heading value is obtained, but reliability deteriorates due to environmental interference and distortion
Solution Approach 1:
The patent introduces absolute position measurements from GNSS as an intermediary reference. Instead of directly measuring heading using magnetometers that are susceptible to environmental interference, the system uses the GNSS absolute position to indirectly determine heading by comparing propagated positions of virtual instances against the actual GNSS position. This intermediary approach eliminates magnetic field interference while maintaining heading accuracy.
Solution Approach 2:
The patent replaces the magnetic field-based measurement system (magnetometers) with a position-based measurement system (GNSS). By substituting the physical magnetic sensing mechanism with satellite-based position measurement, the system eliminates the reliability issues associated with magnetic interference and distortion while obtaining accurate absolute heading values.
3Measurement precision
If high-performance gyrocompasses are used to provide accurate heading measurement, then measurement precision is improved, but device complexity, size, and weight increase
Solution Approach 1:
The patent uses multiple virtual copies of the mobile body, each with a different initial heading angle, to explore the solution space. These virtual instances propagate through inertial navigation data and are compared against absolute position measurements to identify the correct heading. This virtual replication approach achieves high-precision heading measurement without requiring the physical size and weight of high-performance gyrocompasses.
Solution Approach 2:
The patent employs simple virtual instances that can be easily created and discarded during the heading estimation process. These virtual bodies are computational constructs that require minimal resources compared to high-performance gyrocompasses. By using these disposable virtual models rather than expensive physical instruments, the system achieves accurate heading measurement with reduced device complexity, size, and weight.
4Measurement precision
If dual-polarized antenna is used for heading estimation, then heading accuracy is improved, but device complexity increases due to specialized hardware requirements
Solution Approach 1:
The patent creates multiple virtual instances with different initial heading angles to explore the solution space computationally. By propagating these virtual instances through inertial navigation data and comparing them against absolute position measurements, the system achieves accurate heading estimation without requiring specialized dual-polarized antenna hardware. The virtual replication approach replaces complex physical antenna systems with computational models.
Solution Approach 2:
The patent substitutes the mechanical dual-polarized antenna system with a computational approach using virtual instances and inertial navigation data processing. Instead of using specialized hardware that requires precise polarization handling and complex signal processing, the system uses software-based virtual models to achieve the same heading estimation accuracy, thereby reducing device complexity.
5Loss of time
If multiple virtual instances are propagated using inertial navigation data, then computational effort increases, but convergence time is reduced
Solution Approach 1:
The patent performs preliminary propagation of multiple virtual instances through inertial navigation data before final heading determination. By pre-computing the trajectories of these virtual instances and storing their positions, the system enables rapid comparison against absolute position measurements to quickly identify the correct heading. This preliminary action reduces the time needed for final convergence while keeping computational effort manageable through efficient data structures and algorithms.
Data Source
AI summary
A method of determining a heading angle of a mobile body may include determining an initial position of the body and defining different initial heading angles and virtual instances of the body. Each of the virtual instances is initialized with one of the initial heading angles and with the initial position. The body is moved along a trajectory and inertial navigation data associated with the body is collected. The virtual instances are propagated by updating a position of each of them based on the inertial navigation data. An absolute position measurement is performed along the trajectory to determine an absolute position of the body. The absolute position is compared with the position of each of the virtual instances to find a best-fit instance that best fits the absolute position. The heading angle of the mobile body is determined based on a heading angle associated with the best-fit instance.