Robot Tool Axis Control for Precise Laser Seam Tracking
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Solution Overview
Problem
The limited field of view of laser sensors in welding robots causes precision issues during seam tracking, especially when operating along curved lines with large curvature, as the operation line may exit the sensor's field of view, leading to decreased tracking precision.
Innovation Solution
A robot control apparatus that adjusts the angle of the working tool's axis to keep the operation line at the center of the laser sensor's field of view, using feedback control mechanisms like PID control to maintain precise tracking, even with changing curvatures, and limits sudden angle adjustments to prevent mechanical issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the operation line is curved with large curvature, then the seam tracking operation can follow complex geometries, but the operation line may exit the field of view of the laser sensor
Solution Approach 1:
The patent applies dynamics by making the laser sensor's field of view movable rather than fixed. The sensor rotates dynamically to track the operation line, allowing the field of view to adapt its position and orientation in real-time. This enables continuous tracking of curved operation lines with large curvature while preventing the line from exiting the field of view, thus resolving the contradiction between adaptability to complex geometries and reliability of continuous operation.
2Area of stationary object
If the tracking operation is performed while detecting the position of the operation line in the vicinity of the field of view, then the field of view can cover the operation line, but the precision of the tracking operation decreases
Solution Approach 1:
The patent implements feedback control by continuously monitoring the position of the operation line within the laser sensor's field of view and adjusting the sensor's orientation accordingly. The control unit receives detection results from the laser sensor and dynamically adjusts the sensor's viewing direction to keep the operation line centered in the field of view. This feedback mechanism ensures that the operation line is always detected at the center where precision is highest, while maintaining full coverage capability, thus resolving the contradiction between field of view coverage and tracking precision.
3Measurement precision
If feedback control is used to set the operation line at the center of the field of view, then tracking precision is improved, but sudden angle adjustments may cause mechanical issues
Solution Approach 1:
The patent applies beforehand cushioning by implementing speed limitation and acceleration control in the feedback control system. Before making angle adjustments to position the operation line at the center of the field of view, the control unit calculates and limits the adjustment speed and acceleration. This prevents sudden, large-angle adjustments that would cause mechanical stress or damage to the laser sensor and its mounting mechanism, while still achieving precise positioning over time. The cushioning effect protects the mechanical system from harmful forces while maintaining the precision benefit of centering the operation line.
Data Source
AI summary
A robot control apparatus for a more precise seam tracking operation, includes: a storage unit in which teaching data is stored; an accepting unit that accepts a sensing result of a laser sensor, from a robot including a working tool and the laser sensor attached to the working tool and configured to detect a shape of a working target before an operation of the working tool; and a control unit that moves the working tool based on the teaching data, corrects the movement of the working tool based on the sensing result, and adjusts an angle about a tool axis such that an operation point indicated by the sensing result is at a center of a field of view of the laser sensor. Accordingly, an operation line can be detected near the center of the field of view of the laser sensor, and thus more precise detection is possible.