Robot Tool-Tip Measurement Fixture for Visual Coordinate Alignment
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Solution Overview
Problem
Existing robot systems face challenges in accurately determining the position of a tool tip, particularly in spot-welding applications, due to limitations in visual sensor alignment and coordinate system recognition, which affects precision and efficiency in positioning the tool tip at multiple welding positions.
Innovation Solution
A robot system equipped with a measurement fixture and a controller that uses visual sensor data to calculate the positional coordinates of the tool tip in a reference coordinate system, incorporating a gripping portion and extension portion with grooves and holes for precise alignment and image processing to determine the tool tip's position and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a visual sensor with vertical line of sight is used to determine tool tip position by moving the center of the tool in the vertical direction and changing robot orientation, then the tool tip position can be determined, but the measurement precision and alignment accuracy are insufficient
Solution Approach 1:
A measurement fixture is introduced as an intermediary component between the tool and the visual sensor. The fixture includes a positioning portion that attaches to the tool tip and an extension portion with imaging targets (holes or marks). This intermediary structure provides known geometric features that the visual sensor can easily detect and use to calculate the tool tip position through coordinate transformation, eliminating the need for complex direct alignment between the sensor and tool.
Solution Approach 2:
The measurement approach transitions from direct vertical line-of-sight measurement to a multi-dimensional coordinate transformation system. The measurement fixture establishes a fixture coordinate system that can be transformed into the robot's reference coordinate system through detected position data and pre-stored positional relationships. This dimensional transformation allows the visual sensor to determine tool tip position through image data analysis rather than requiring precise vertical alignment.
2Measurement precision
If a laser tracker with reflector is used to detect reflector position, then tool position can be measured, but the system complexity and cost increase significantly
Solution Approach 1:
The patent replaces the mechanical laser tracker system with an optical visual sensor system. Instead of using a laser tracker to detect reflector position, the invention uses a visual sensor to capture images of the measurement fixture's imaging targets (holes or marks). The controller then calculates tool tip position based on these image data and coordinate transformations. This substitution reduces system complexity and cost while maintaining measurement capability.
Solution Approach 2:
The measurement fixture creates an optical copy or representation of the tool tip position through its imaging targets. The visual sensor captures an image of the measurement fixture, and the controller uses this image data to determine the tool tip position indirectly. This copying approach allows the system to measure tool position without requiring direct mechanical contact or complex laser tracking infrastructure.
3Measurement precision
If the measurement fixture includes a gripping portion with grooves and an extension portion with holes or marks, then the visual sensor can accurately detect the fixture position, but the fixture structure becomes more complex
Solution Approach 1:
The measurement fixture is segmented into distinct functional portions: a gripping portion with grooves for securing the tool, and an extension portion with imaging targets (holes or marks). This segmentation allows each portion to perform its specific function efficiently - the gripping portion provides secure attachment while the extension portion provides detectable features for the visual sensor. The segmentation also simplifies the overall design by separating the attachment mechanism from the measurement features.
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 configuration enhances precision and facilitates efficient work by accurately calculating the tool tip's position and orientation, improving the robot's ability to perform tasks like spot welding with increased accuracy and ease.
Implementation Method 1
acquire an image of the measurement fixture by means of a visual sensor
Data Source
AI summary
A robot including an arm, a tool attached to the arm, a measurement fixture to be attached to a tip portion of the tool detachably, and a controller that recognizes a reference coordinate system used to control the arm, and that controls the arm. The controller stores data indicating a positional relationship between a tip of the tool and the measurement fixture or data to be used to calculate the positional relationship, and the controller calculates positional coordinates of the tip of the tool in the reference coordinate system based on position data of the measurement fixture and the positional relationship, where the position data is detected by using acquired image data from a visual sensor whose position is associated with the reference coordinate system.