Payload Navigation Kalman Filter Transfer Alignment Bias Correction
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Solution Overview
Problem
During transfer alignment, the onboard navigation system of a payload faces challenges in handling step changes in measurement updates from the aircraft's navigation system, which can lead to rejection or incorrect interpretation of measurement errors due to drift corrections.
Innovation Solution
A navigation system that includes a local Kalman filter receiving Precision Transfer Alignment Messages (PTAM) and Reset Transfer Alignment Messages (RTAM) from a master Kalman filter, where the RTAM bias correction is used to adjust the local navigation states, preventing additional residuals and ensuring accurate navigation solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the aircraft navigation system applies bias correction resets to correct accumulated drift error, then navigation accuracy is improved, but the payload navigation system experiences step changes that cause measurement update rejection or incorrect error interpretation
Solution Approach 1:
The payload navigation system proactively applies the same bias correction to its navigation solution before receiving the corrected measurement updates from the aircraft. This preliminary action ensures that when the corrected measurements arrive, there is no step change or discontinuity, allowing the Kalman filter to accept the updates without rejection while maintaining navigation accuracy.
Solution Approach 2:
The system uses feedback from the aircraft navigation system's bias correction values to adjust the payload navigation system's own navigation solution. By monitoring and applying the same corrections that the master system applies, the payload system maintains synchronization and avoids measurement rejection issues.
2Productivity
If the payload navigation system accepts step change measurement updates, then measurement updates are continuously received, but the system faces difficulty in correctly interpreting measurement errors and allocating sensor errors
Solution Approach 1:
The payload navigation system pre-applies bias corrections from the aircraft navigation system before processing measurement updates. This ensures continuous acceptance of updates while maintaining accurate error interpretation, as the system has already compensated for the expected step changes.
Solution Approach 2:
The bias correction values act as an intermediary mechanism that bridges the gap between the aircraft and payload navigation systems. By using these corrections as a reference, the payload system can distinguish between actual measurement errors and artifacts caused by master system resets, enabling accurate error allocation.
Data Source
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AI summary
Systems and methods to incorporate master navigation system resets during transfer alignment are provided. In one embodiment, a system comprises: a set of local inertial sensors; a local navigation processor coupled to local inertial sensors, the local navigation processor receiving inertial navigation data from local inertial sensors and converting the data into a navigation solution; a local Kalman filter (LKF) coupled to the local navigation processor and a master Kalman filter (MKF), the LKF receiving the navigation solution. The LKF receives from the MKF a Precision Transfer Alignment Message (PTAM) that includes at least one navigation aid measurement. The LKF inputs the navigation aid measurement into a measurement formation algorithm and calculates a measurement residual. The LKF receives from the MKF a Reset Transfer Alignment Message (RTAM) that includes a bias correction. The LKF inputs the bias correction into a state propagation algorithm to add to a navigation state.