Rotatable Dual-IMU Calibration for Inertial Navigation Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inertial navigation systems face challenges in accurately calibrating sensors due to errors that drift over time, especially in dynamic environments, as traditional calibration methods require the system to be stationary, and external aiding data can be unreliable.
Innovation Solution
Employing two separate inertial measurement units (IMUs) with one rotatable relative to the other, allowing continuous calibration during motion by determining sensor errors simultaneously with main output measurements, using a controller to perform a sequence of maneuvers to estimate and correct biases, scale factors, and other errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used with the system stationary, then calibration accuracy is improved, but the system cannot be calibrated during motion and sensor errors drift over time
Solution Approach 1:
The patent applies the dynamics principle by enabling calibration during motion rather than requiring the system to be stationary. The rotatable IMU allows the system to perform calibration maneuvers while moving, transforming a static calibration process into a dynamic one that can occur during actual operation, thereby eliminating idle calibration time and reducing drift between calibrations.
Solution Approach 2:
The patent implements preliminary action by performing calibration maneuvers at predetermined intervals during motion. The system proactively schedules calibration sequences during flight or operation, ensuring calibration occurs before significant drift accumulates, rather than waiting for stationary conditions or reacting to performance degradation.
2Ease of operation
If external aiding data is used for calibration, then calibration can be performed during use, but the accuracy is reduced due to GPS inaccuracies, blocking, jamming, or spoofing
Solution Approach 1:
The patent uses a rotatable IMU mechanism as an intermediary to enable calibration during motion without relying on external aiding data. The physical rotation capability allows the system to perform self-calibration maneuvers independently, mediating between the need for continuous calibration and the unreliability of external GPS-based aiding, thereby achieving both ease of operation and high accuracy.
3Device complexity
If a single IMU is used, then the system is simpler, but calibration during motion cannot be performed
Solution Approach 1:
The patent applies universality by designing the rotatable IMU to serve multiple functions: it performs both navigation measurements and calibration maneuvers with the same sensor unit. The IMU is universally capable of operating in both measurement and calibration modes, eliminating the need for separate calibration hardware while enabling motion-based calibration, thus achieving versatility without proportionally increasing complexity.
4Adaptability or versatility
If the IMU is rotated during calibration, then calibration can be performed during motion, but the system requires rotatable mounting mechanism
Solution Approach 1:
The patent applies segmentation by separating the rotation function from the IMU sensor itself, placing the rotatable mechanism at the mounting level rather than integrating it into the sensor housing. This segments the calibration capability into a独立的 mounting structure, allowing the IMU to remain a standard off-the-shelf component while the mounting mechanism provides the rotation capability, thereby reducing overall system complexity.
Data Source
Figure 1a~3
AI summary
An inertial navigation system comprising: a first inertial measurement unit comprising at least a first sensor; and a second inertial measurement unit comprising at least a second sensor corresponding in type to the first sensor; wherein the first inertial measurement unit is rotatably mounted relative to the second inertial measurement unit; and wherein the inertial navigation system further comprises a controller arranged to: acquire a first set of measurements simultaneously from both the first inertial measurement unit and the second inertial measurement unit; rotate the first inertial measurement unit relative to the second inertial measurement unit; acquire a second set of measurements simultaneously from both the first inertial measurement unit and the second inertial measurement unit; and calculate from the first set of measurements and the second set of measurements at least one error characteristic of the first sensor and/or the second sensor. Using two separate IMUs rotatable relative to one another means that the orientation of some or all of the sensors in the first IMU can be changed with respect to their counterparts in the second IMU. With this arrangement the error characteristics of the sensors can be determined at the same time as obtaining measurements of the continually changing main sensor output. This allows the inertial measurement calibration to be performed while on the move rather than having to perform calibration while the IMU is at rest.