Rolling Wheel Deflectometer Virtual Image Matching
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Solution Overview
Problem
Traditional rolling wheel deflectometers face challenges in achieving precise measurements due to the minute deflection caused in pavements, which is difficult to measure accurately at high speeds, especially when natural height variations of the pavement surface differ significantly from the deflection being measured.
Innovation Solution
The method involves comparing and matching virtual images from range sensors to identify corresponding regions on the pavement surface with high accuracy, using light intensity values in addition to range information, and applying the Harr algorithm to pixel values to calculate deflection, allowing for precise deflection measurements without the need for additional detectors and enabling calculations to be performed on a standard personal computer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional distance sensors are used to measure pavement deflection at high speed, then measurement speed is improved, but measurement precision deteriorates due to the minute deflection being lost against natural surface roughness
Solution Approach 1:
The patent creates virtual images (copies) of the pavement surface from multiple range sensor measurements taken at different positions. These virtual images are then processed using the Harr algorithm to extract deflection information. By working with image copies rather than direct sensor readings, the system can achieve precise deflection measurements while maintaining high measurement speed.
Solution Approach 2:
The patent transforms the one-dimensional distance measurements from range sensors into two-dimensional virtual images. This dimensional transformation allows the application of image processing techniques and the Harr algorithm, which can extract subtle deflection patterns that would be difficult to detect in simple distance readings, thereby improving measurement precision without sacrificing speed.
2Measurement precision
If the odometer and tracking precision are increased to improve measurement accuracy, then deflection measurement precision is improved, but device complexity increases
Solution Approach 1:
Instead of relying on complex physical tracking systems to precisely identify positions, the patent creates virtual images that contain embedded position information. The Harr algorithm processes these images to automatically identify corresponding positions and calculate deflections, eliminating the need for highly precise external odometers and tracking systems.
Solution Approach 2:
The patent introduces virtual images as an intermediary between the range sensors and the deflection calculation. These images serve as a mediator that encapsulates both the pavement surface information and the positional data, allowing the system to achieve precise measurements without requiring complex separate tracking systems.
3Reliability
If average values over large areas are used for comparison, then measurement robustness is improved, but measurement precision deteriorates due to loss of local deflection details
Solution Approach 1:
The patent segments the pavement surface into multiple pixels in the virtual images. The Harr algorithm then processes individual pixel values or small groups of pixels to calculate local deflections. This segmentation allows the system to maintain measurement robustness through statistical processing while preserving the precision of local deflection measurements that would be lost in area-averaged approaches.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves highly precise rolling wheel deflection measurements by smoothing out errors and improving identification rates, enabling accurate deflection calculations even when the rolling wheel deflectometer is turning, with the ability to calculate deflection values line by line and suppress noise from CCD cameras.
Implementation Method 1
a first virtual image of a sector of the pavement surface is recorded by a range sensor
Data Source
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AI summary
A method and an apparatus (1) for rolling wheel deflection measurement. The apparatus comprises: A rolling wheel (4) to be moved along a measuring surface (2) in a first direction. A frame (6) extending essentially along said measuring surface (2) in said first direction from at least said rolling wheel (4). Four spaced apart range sensors (7, 8, 9, 10). Means for scanning in a first time interval a number of lines using each of said range sensors (7, 8, 9, 10), so as to get a corresponding number of virtual images, in which the pixel values represent distances. Dataprocessing means adapted for comparing and matching said virtual images, so as to identify corresponding regions, and for calculating a deflection value using matched pixel values of virtual images from said virtual images based on said identification corresponding regions.