Robot Teaching Point Correction Using Stereo Camera Depth Offset
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Solution Overview
Problem
Existing robot apparatuses face challenges in accurately correcting teaching points due to limitations in the depth of field of three-dimensional visual sensors, leading to inaccurate position measurements of indicators, especially when they are positioned at the edge of the sensor's view or out of its measurement range.
Innovation Solution
A method that involves positioning the working unit at an imaging point offset from the teaching point in the depth of field direction of the three-dimensional visual sensor, allowing for accurate measurement and correction of the teaching point by imaging and processing the indicator's position with the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the working unit is positioned at the teaching point for measurement, then the teaching point correction is performed, but the indicator may be out of the measurement range or at the edge of the angle of view, resulting in inaccurate position measurement
Solution Approach 1:
The patent introduces an offset in the depth of field direction (Z-axis) to create an imaging point that is spatially separated from the teaching point. This dimensional shift allows the indicator to be imaged within the optimal measurement range of the three-dimensional visual sensor while still enabling correction of the teaching point through coordinate transformation. The offset distance is carefully selected to ensure the indicator falls within the depth of field and away from the angle of view edges.
2Measurement precision
If the indicator is positioned within the measurement range of the three-dimensional visual sensor, then accurate position measurement is achieved, but the working unit cannot be positioned exactly at the teaching point for correction
Solution Approach 1:
The patent introduces an intermediate imaging point that serves as a mediator between the teaching point and the measurement capability of the visual sensor. The indicator is imaged at this intermediate position with offset in the depth of field direction, ensuring optimal measurement conditions. The measured position is then used to calculate the teaching point correction through coordinate transformation, effectively using the intermediate point as a bridge to achieve both accurate measurement and precise correction.
3Adaptability or versatility
If the three-dimensional visual sensor is used to image the indicator at the teaching point, then teaching point correction is enabled, but depth of field limitations cause measurement inaccuracies
Solution Approach 1:
The patent changes the imaging position parameter by introducing an offset in the depth of field direction. Instead of imaging the indicator exactly at the teaching point (Z=0), the system images it at an offset position (Z=offset_distance) where the indicator falls within the optimal depth of field range of the three-dimensional visual sensor. This parameter change ensures that the indicator is captured with high measurement precision while still enabling teaching point correction through coordinate transformation.
Data Source
AI summary
Indicators are set on a marker positioned on a working stage in conformity with a target teaching point. A stereo camera images the indicator in a state of being positioned on a robot hand, and measures the three-dimensional position of the marker. In robot arm controlling, the robot hand is positioned at the correction teaching point for off-line that is offset from an off-line teaching point in the depth of field direction of the stereo camera. In imaging, while the robot hand is positioned at the correction teaching point for off-line, the indicators are imaged by the stereo camera. In correcting, based on an imaging result of the indicator, the on-line teaching point is corrected toward the target teaching point to obtain the on-line teaching point.