Crankshaft Inspection via Point Cloud Segmentation
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Solution Overview
Problem
Conventional methods for inspecting crankshafts are inefficient in accurately detecting partial defects like underfills and dent flaws while discriminating them from bending and torsion over the entire length of the crankshaft, leading to inconsistencies in inspection accuracy and time-consuming processes.
Innovation Solution
A method utilizing a three-dimensional shape measurement device to acquire point cloud data, divide it into subregions, and superpose each subregion onto a surface shape model to minimize distance, allowing for accurate detection of partial defects by calculating distances and evaluating bending and torsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual inspection using plate gauges is performed, then inspection can be conducted with simple equipment, but inspection accuracy varies due to personal differences and requires significant time
Solution Approach 1:
The patent replaces manual mechanical inspection using plate gauges and scales with an automated optical measurement system that captures images and automatically analyzes crankshaft geometry, eliminating human variability and reducing inspection time
Solution Approach 2:
The patent creates a three-dimensional digital model (copy) of the crankshaft from captured images and compares it with the ideal design model, enabling automated accuracy assessment without manual measurement
2Measurement precision
If the entire crankshaft is analyzed as a single unit, then bending and torsion can be evaluated, but partial defects like underfills and dent flaws cannot be accurately detected
Solution Approach 1:
The patent divides the crankshaft three-dimensional model into multiple segmentation regions corresponding to different structural components (crank arms, journals, counterweights), enabling localized defect detection while maintaining overall structural evaluation
Solution Approach 2:
The patent applies different evaluation criteria and measurement approaches to different regions of the crankshaft, such as evaluating roundness at journals, straightness at crank arms, and detecting surface defects like underfills and dents in specific locations
3Measurement precision
If conventional inspection methods are used, then both bending/torsion and partial defects must be detected, but the methods cannot discriminate between these different types of deviations
Solution Approach 1:
The patent segments the crankshaft into multiple regions and evaluates each region independently against appropriate criteria, allowing discrimination between global deformations (bending/torsion affecting multiple regions) and local defects (affecting specific regions)
Solution Approach 2:
The patent provides visual feedback by displaying the three-dimensional model with detected defects marked and highlighted, allowing operators to quickly identify and distinguish between different types of deviations without manual interpretation
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 enables precise discrimination and detection of partial defects, reducing the influence of bending and torsion, and significantly reducing the time required for inspection while maintaining high accuracy.
Implementation Method 1
an optical three-dimensional shape measurement device which is disposed to face a crankshaft in a direction perpendicular to a rotational center axis of the crankshaft, and is configured to measure a three-dimensional shape of a measurement object by projecting and receiving light to and from the measurement object
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3C
AI summary
The present invention provides a method for inspecting a crankshaft, which enables accurate detection of defects which occur partially in the crankshaft, such as underfills and dent flaws, by discriminating these defects from bending and torsion over an entire length of the crankshaft. The present invention includes steps of: acquiring three-dimensional point cloud data over an entire length of a measurement object region of a crankshaft S by an optical three-dimensional shape measurement device 1; dividing the acquired three-dimensional point cloud data to create a plurality of subregion three-dimensional point cloud data, each of the subregion three-dimensional point cloud data respectively corresponding to each of a plurality of subregions of the crankshaft along a direction parallel to the rotational center axis L of the crankshaft; translating and rotating each of the created subregion three-dimensional point cloud data to superpose each of the subregion three-dimensional point cloud data on a surface shape model of the crankshaft, such that a distance between each of the subregion three-dimensional point cloud data and the surface shape model becomes minimum; and detecting a partial defect such as an underfill of the crankshaft based on a distance between each of the subregion three-dimensional point cloud data after being superposed and the surface shape model.