NDI Inertial Sensor Drift Correction via Frame Markings
Solution Overview
Problem
Inertial sensors in non-destructive inspection systems suffer from integration drift, leading to position uncertainty and image distortion over time, making it difficult to obtain accurate and clear images of structures during scanning.
Innovation Solution
A low-cost frame with unique physical patterns on its edges, detectable by the NDI sensor, is used to correct measurement distortions caused by inertial sensors, allowing periodic re-zeroing and re-orientation of the sensor, thereby minimizing drift and improving image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inertial sensors are used to determine position and orientation during scanning, then the system can operate portably and cost-effectively, but integration drift causes position uncertainty and image distortion over time
Solution Approach 1:
The patent introduces a frame with detectable markings as an intermediary object between the inertial sensor and the scanning environment. These markings serve as reference points that allow the system to periodically correct accumulated position errors from inertial integration, thereby maintaining measurement precision without sacrificing the portability and cost-effectiveness of inertial sensors
Solution Approach 2:
The system implements feedback by detecting the known markings on the frame and using them to correct drift in the inertial sensor measurements. The computer processes the detected marking positions to calculate correction factors that are applied to the accumulated position data, creating a closed-loop system that maintains accuracy over time
2Ease of operation
If inertial sensors are used for positioning during scanning, then the system can be made portable, but integration drift increases position uncertainty over time
Solution Approach 1:
The frame with markings acts as a mediator that enables reliable position determination in a portable system. By providing known reference points that the sensor can detect, the frame allows the portable system to periodically reset and correct its position estimates, maintaining reliability without requiring heavy fixed infrastructure
Solution Approach 2:
The frame is prepared in advance with known marking patterns at specific locations. This preliminary setup allows the system to predict where markings should appear and use these pre-established references to correct drift, ensuring reliable positioning throughout the scanning process
3Area of stationary object
If inertial sensors are used for scanning, then the system can achieve wide coverage area, but integration drift causes image distortion that renders images unusable
Solution Approach 1:
The system uses periodic detection of frame markings to correct drift at regular intervals during scanning. This periodic correction approach allows the system to maintain image quality over large scan areas by resetting accumulated errors whenever a marking is detected, enabling wide coverage without sacrificing image usability
Data Source
AI summary
A free-hand inspection apparatus for non-destructively inspecting a structure includes an array and an inertial sensor. The array includes a plurality of elements for transmitting and receiving inspection signals to/from a structure being inspected. The inertial sensor measures acceleration and angular rotation rate in three dimensions. A frame with a unique physical pattern on its edges, which are detectable by the system, is provided. In one embodiment, the frame comprises a special appliqué including a plastic sheet that has periodic edge features, or markings. The markings are detectable by the sensor and allow the system to correct the measurement distortions caused by the inertial sensors used for positioning while making scans. A computer-based process is provided to correct for drift when the sensor encounters one of these markings, thereby solving the problem of error accumulation and the resulting position inaccuracy.