Laser Welding Focal Shift Detection From Optical Signal Gradients
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Solution Overview
Problem
Existing methods for determining the processing state in laser welding, such as PTL 1, face challenges in accurately assessing why focal position shifts occur, leading to joint defects, as they primarily focus on detecting welding defects rather than detailing the shift of the focal position.
Innovation Solution
A determination method and device that utilize an optical sensor to detect heat radiation, visible light, and reflected light during laser processing, calculate feature quantities like the gradient of a signal waveform, and input these into a determination model to assess the shift of the focal position, including its farness and closeness, to determine the processing state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods detect welding defects using light intensity, then welding state determination is achieved, but detailed analysis of focal position shift is not provided
Solution Approach 1:
The patent segments the light signal into multiple wavelength bands (e.g., blue band, green band, red band, infrared band) to detect different characteristics. By analyzing the gradient of light intensity in each wavelength band separately, the system can precisely determine focal position shifts and distinguish between different processing states (focused, over-focused, under-focused), thereby resolving the contradiction between measurement precision and information loss.
2Loss of information
If only welding defect detection is performed, then simple determination is achieved, but detailed processing state analysis is lost
Solution Approach 1:
The patent adds a new dimension to the determination process by introducing wavelength band segmentation and gradient calculation. Instead of simply detecting light intensity, the system analyzes the rate of change (gradient) of light intensity across multiple wavelength bands, transforming the determination from a single-dimensional defect detection to a multi-dimensional processing state analysis that provides detailed focal position information.
3Measurement precision
If gradient of light signal is calculated for focal position determination, then detailed processing state is obtained, but measurement complexity increases
Solution Approach 1:
The patent replaces complex manual analysis of light signals with automated computational processing. The gradient calculation is performed algorithmically on the detected light intensity signals across different wavelength bands, and the determination model automatically classifies the processing state based on these gradients, substituting manual measurement complexity with automated computational analysis that achieves high precision.
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
Enables detailed determination of the processing state in laser processing for lap welding, specifically identifying shifts in the focal position, thereby preventing joint defects by accurately analyzing the processing state and providing a determination result.
Implementation Method 1
detecting, using an optical sensor, at least one of heat radiation light, visible light, and reflected light generated at a welded portion
Implementation Method 2
detecting, using an optical sensor, at least one of heat radiation light, visible light, and reflected light generated at a welded portion
Data Source
AI summary
A determination method for determining a processing state includes detecting, using an optical sensor, at least one of heat radiation light, visible light, and reflected light generated at a welded portion formed at a surface of a workpiece by emission of a laser beam on the workpiece, obtaining a signal indicating a change in at least one of heat radiation light, visible light, and reflected light in a time section corresponding to a welding time of each workpiece, calculating a feature quantity including a gradient of a straight line approximating a signal waveform of the signal in a predetermined section in the time section, determining, as the processing state, a shift including farness and closeness of a focal position of the laser beam in an emission direction of the laser beam by inputting the calculated feature quantity to a determination model that determines the processing state.