Monocular Vision Displacement Measurement Decoupling
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Solution Overview
Problem
Existing methods for measuring planar motion displacement and trajectory have high complexity, poor flexibility, high cost, and limited measurement range, failing to meet the requirements for low-frequency and high-precision measurements.
Innovation Solution
A monocular vision-based method that decouples planar motion into single-component linear motion measurements using high-contrast feature marks, sub-pixel edge detection, and least-square fitting, allowing for precise displacement and trajectory analysis in both X and Y directions, and sine-approximation for trajectory calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser interferometric method is used for measuring displacement and trajectory, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the complex mechanical laser interferometric measurement system with a vision-based measurement system using a single camera. The camera captures images of feature marks on the measured object, and displacement is calculated through image processing and coordinate transformation, eliminating the need for complex interferometric hardware while maintaining measurement capability
Solution Approach 2:
The patent uses image copying of feature marks from different positions to determine displacement. By capturing images of the same feature mark at different locations and comparing their coordinates, the system calculates displacement without requiring direct physical measurement instruments, thereby simplifying the measurement system
2Device complexity
If sensor-based measuring method is used, then device complexity is reduced, but measurement precision is limited by sensor frequency
Solution Approach 1:
The patent replaces frequency-limited vibration sensors with a vision-based measurement system. Instead of using sensors that have inherent frequency limitations, the system uses a camera to capture images and calculate displacement through coordinate analysis, removing the frequency constraint while keeping the system simple
3Device complexity
If existing monocular vision method is used, then device complexity and cost are reduced, but measurement precision is limited to 10 μm
Solution Approach 1:
The patent introduces a calibration board with known spatial coordinates in the real world to establish a precise mapping relationship between image coordinates and real-world coordinates. By using the calibration board's known geometry, the system achieves higher measurement precision through coordinate transformation, overcoming the limitations of direct monocular vision measurement
Solution Approach 2:
The patent changes the measurement parameters by using sub-pixel edge detection algorithms to determine feature mark positions with precision beyond single pixel resolution. By detecting edges at sub-pixel levels and combining this with calibration data, the system achieves measurement precision better than the traditional 10 μm limit
4Speed
If laser interferometric method is used, then measurement range for high-frequency motion is improved, but adaptability for low-frequency large-displacement measurement deteriorates
Solution Approach 1:
The patent makes the measurement system dynamically adaptable by adjusting camera exposure time and frame rate according to the measurement requirements. For low-frequency large-displacement measurements, the camera uses longer exposure and lower frame rate, while for high-frequency measurements, it switches to shorter exposure and higher frame rate, providing versatile adaptability across different measurement scenarios
Data Source
AI summary
A monocular vision-based method for measuring displacement and trajectory of planar motion. In this method, a sequence image of a motion of a high-contrast feature mark fixed on a moving plane to be measured is collected using a camera. A sub-pixel coordinate of a feature edge of a linear motion of the sequence in an X direction and a Y direction is extracted using a sub-pixel edge detection method, and the sub-pixel coordinate is converted into a corresponding world coordinate. The world coordinate of the feature edge is fitted based on a least squares principle to obtain a straight line of the feature edge to realize decoupling measurement of a displacement in the X direction and the Y direction. The planar motion trajectory is obtained through measuring the displacement in the X direction and the Y direction.