Adaptive Forgetting Factor for Angular Velocity Sensor Offset Correction
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Solution Overview
Problem
Existing angular velocity sensors in navigation systems face challenges in accurately correcting offset values and conversion coefficients, especially during short startup times and in environments with poor GPS reception, leading to reduced precision in angular velocity calculations.
Innovation Solution
An angular velocity sensor correcting apparatus that includes an obtaining unit for measurement data, an angular velocity conversion coefficient deriving unit, and a filter process unit that adjusts a forgetting factor based on past coefficients and temporary values to improve the precision of angular velocity calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the number of samples is increased to stabilize the offset value, then the stability of offset value improves, but the time required to obtain accurate angular velocity conversion coefficient increases
Solution Approach 1:
The patent applies dynamics by making the forgetting factor adaptive rather than static. The forgetting factor changes dynamically based on the variance of temporary conversion coefficients, allowing the system to adjust its memory characteristics in real-time. This resolves the contradiction by enabling rapid adaptation when coefficients are unstable while maintaining stability when coefficients converge, thus reducing the overall time required without sacrificing accuracy.
Solution Approach 2:
The patent changes the parameter of the forgetting factor based on the variance of temporary conversion coefficients. When variance is high (unstable state), a smaller forgetting factor is used to prioritize recent measurements. When variance is low (stable state), a larger forgetting factor is used to smooth results. This parameter adaptation resolves the time-stability contradiction by optimizing the filtering characteristics for each operational phase.
2Ease of operation
If correction is performed during straight running, then the ease of operation improves, but the measurement precision deteriorates due to road shape and driving state influences
Solution Approach 1:
The patent uses feedback by calculating the variance of temporary conversion coefficients and using this variance information to adjust the forgetting factor. This feedback mechanism allows the system to detect when measurements are reliable (low variance) and when they are not (high variance), automatically adjusting its behavior accordingly. This resolves the contradiction by enabling correction during straight running only when the feedback indicates sufficient precision.
Solution Approach 2:
The system dynamically adjusts the forgetting factor based on real-time variance calculations. During straight running, if the variance indicates stable measurements, the system accepts corrections with appropriate weighting. If variance is high, the system reduces the influence of such measurements. This dynamic adjustment resolves the contradiction between ease of operation and measurement precision.
3Adaptability or versatility
If GPS orientation change amount is used for conversion coefficient derivation, then the adaptability improves, but the measurement precision deteriorates in areas with poor GPS reception
Solution Approach 1:
The patent dynamically adjusts the forgetting factor based on the variance of temporary conversion coefficients derived from GPS data. When GPS reception is poor and variance is high, the system automatically reduces the influence of these unreliable measurements through a smaller forgetting factor. When GPS reception is good and variance is low, the system can rely more heavily on these measurements with a larger forgetting factor. This dynamic adaptation resolves the contradiction between versatility and precision.
Data Source
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AI summary
A measuring unit (10) obtains measurement data of an object measured on the basis of a signal from a GPS satellite and angular velocity of an object output from an angular velocity sensor (26). An offset value computing unit (28) estimates a running condition of the object. The offset value computing unit (28) sequentially derives temporary offset values while changing combination of the measurement data and the angular velocity in accordance with the estimated running condition of the object and, after that, executes statistical process on the temporary offset values, thereby deriving an offset value. An angular velocity conversion coefficient computing unit (30) sequentially derives temporary angular velocity conversion coefficients on the basis of the measurement data and the angular velocity and, after that, executes statistical process on the temporary angular velocity conversion coefficients, thereby deriving an angular velocity conversion coefficient.