Inertial Sensor Calibration via Coordinate Transformation Matrix
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Solution Overview
Problem
Existing methods for calibrating inertial sensors installed in arbitrary positions on vehicles often result in measurement errors, particularly concentrating errors on one axis, which compromises the functionality of applications relying on accelerometer data.
Innovation Solution
A calibration method that acquires real-measured data from inertial sensors and reference-measured data from a separate detector, such as a GPS receiver, to generate a coordinate-transformation matrix, ensuring all elements are computed by comparing data under various driving conditions, and adjusting values to enforce orthogonality, thereby distributing errors evenly across the matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a mixed calibration approach is used where six coefficients are directly determined from measurements and three coefficients are calculated using mathematical orthogonality constraints, then the calibration process can be completed with fewer physical measurements, but measurement errors are propagated to the three calculated coefficients and may concentrate excessive error on one measurement axis
Solution Approach 1:
The patent changes the calibration approach by determining all nine coefficients through a system of linear equations derived from comparing sensor measurements with reference measurements under multiple driving conditions. This parameter change ensures that all coefficients are computed from actual measurements rather than mixing measurements with mathematical constraints, thereby distributing measurement errors evenly across all coefficients and avoiding excessive error concentration on any single axis.
2Ease of operation
If the sensor device is installed in an arbitrary position to facilitate installation, then installation ease is improved, but the alignment between sensor axes and vehicle main axes becomes difficult to ensure
Solution Approach 1:
The patent introduces a coordinate-transformation matrix as an intermediary that relates the arbitrary sensor reference system to the vehicle main axis reference system. This matrix, computed through calibration by comparing sensor measurements with reference measurements under multiple driving conditions, enables accurate representation of vehicle dynamics regardless of sensor installation position, thereby maintaining manufacturing precision while preserving installation ease.
3Device complexity
If direct determination of six coefficients is used based on orthogonality relationships, then the calibration process is simplified, but measurement errors are propagated and may significantly compromise application functionality
Solution Approach 1:
The patent implements a feedback mechanism by comparing sensor measurements with reference measurements from a GPS receiver or other reference system under multiple driving conditions. This feedback loop allows the system to compute coordinate-transformation coefficients that accurately reflect the relationship between sensor and vehicle reference frames, ensuring reliable accelerometer data for applications while maintaining calibration process simplicity.
Data Source
AI summary
A method calibrates an inertial-sensor device installed in an arbitrary position on board a vehicle and adapted to detect at least one entity indicative of vehicle dynamics along at least one direction of a local reference-coordinate system. The method includes steps of: acquiring by the inertial-sensor device at predetermined measuring times real-measured data indicative of the vehicle dynamics in the local reference-coordinate system; acquiring by a calibrating detector different from the inertial-sensor device, at sampling times coinciding with the measuring times, reference-measured data indicative of the vehicle dynamics in a vehicle-coordinate system; and generating a coordinate-transformation matrix adapted to correlate the entity measured in the local reference-coordinate system with a corresponding entity in the vehicle-coordinate system. Also, a sensor system of dynamics of the vehicle is able to be installed on board in an arbitrary position.