IMU Calibration via Common Reference Direction
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Solution Overview
Problem
Inertial measurement units (IMUs) face challenges in maintaining accurate absolute orientation over time due to gyroscopic drift, leading to variations in orientation measurements across different IMUs placed on a hinged body, which affects the assessment of relative motion between body parts.
Innovation Solution
A method and system that utilize a processor to obtain direction measurements from multiple IMUs, determine a common reference direction, and calculate new orientations for each IMU to align with this reference, thereby correcting for drift without additional sensors or environmental modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple IMUs are placed on different parts of a hinged body to detect motion at different parts, then the ability to assess relative motion between body parts is improved, but gyroscopic drift causes orientation measurements to diverge over time, deteriorating measurement precision
Solution Approach 1:
The system continuously monitors orientation measurements from multiple IMUs and uses feedback algorithms to detect and correct drift deviations. By comparing relative orientations between IMUs and identifying inconsistencies, the system applies corrective transformations to maintain measurement accuracy over time.
Solution Approach 2:
The system introduces an intermediary reference frame or virtual reference that mediates between multiple IMUs. This virtual reference serves as a common coordinate system that all IMUs can reference, allowing the system to detect and correct individual IMU drift by comparing their measurements against the collective data from all sensors.
2Measurement precision
If corrections are applied to IMU orientations to account for drift, then measurement precision is improved, but the system complexity increases due to the need for additional processing and coordination between multiple IMUs
Solution Approach 1:
The system merges data from multiple IMUs into a unified orientation solution. By combining measurements from all sensors and processing them collectively, the system achieves better accuracy than any single IMU could provide alone, while distributing the computational workload across the sensor network.
Solution Approach 2:
The multiple IMUs collectively serve to correct each other's drift through mutual comparison. Each IMU's measurements contribute to the overall calibration of the system, allowing the sensors to self-correct without requiring external reference instruments or additional calibration equipment.
3Measurement precision
If additional sensors are used to correct IMU drift, then measurement precision is improved, but the device complexity and cost increase
Solution Approach 1:
The system uses the IMUs themselves to correct their own drift through mutual comparison and collective processing. Each sensor's data contributes to calibrating the others, eliminating the need for external reference sensors or additional calibration equipment while maintaining measurement accuracy.
Solution Approach 2:
The IMU system performs multiple functions: it simultaneously measures absolute orientation, detects relative motion between body parts, and self-calibrates to correct drift. This multi-functionality eliminates the need for separate dedicated calibration sensors or reference instruments.
Data Source
AI summary
Inertial measurement units attached to a non-rigid body may measure a common motion event when the body changes direction of travel. Acceleration measurements made by the inertial measurement units of the event are used to determine a common reference direction which in turn can be used to derive, individually for each inertial measurement unit, a new orientation intended to be a better representation of the actual orientation of the inertial measurement unit.