Robot End Effector Positioning With Multi-Axis Optical Markers
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Solution Overview
Problem
Existing methods for determining the position and orientation of a robot's end effector in industrial environments are either complex and costly or unable to provide accurate data in all working positions, particularly due to visibility issues and temperature-induced errors.
Innovation Solution
A device and method using optical markers and a kinematic model, where an optical sensor acquires image data of markers on the robot arm, and an evaluation device determines the position and orientation of the end effector based on visible markers and the kinematic model, even when some markers are not visible, reducing errors and ensuring accuracy in all positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical markers are placed on the robot arm and tracked using an optical sensor, then the position and orientation of the end effector can be determined, but visibility problems occur when markers are obscured by robot parts or workpieces in certain working positions
Solution Approach 1:
The robot arm is divided into multiple segments (axes), and optical markers are placed on different segments. This segmentation allows the system to track at least one visible marker regardless of the robot's configuration, solving the visibility problem while maintaining measurement precision.
Solution Approach 2:
The system transitions from relying on a single marker to using multiple markers distributed across different spatial dimensions and robot axes. This dimensional distribution ensures that at least one marker remains visible from the optical sensor's perspective throughout the robot's workspace.
2Measurement precision
If constant recalibration of the robot model is performed to compensate for temperature-induced material expansion, then position accuracy can be maintained, but the system complexity and time expenditure increase
Solution Approach 1:
The system uses the robot's own structure (axes and joints) as reference elements for tracking. By placing markers on the robot's existing components rather than requiring external calibration artifacts, the system achieves temperature compensation without additional complex recalibration equipment.
Solution Approach 2:
The patent replaces mechanical recalibration systems with an optical tracking system. Instead of physically recalibrating the robot model through mechanical measurements, the system uses optical markers and image data to continuously determine position and orientation, eliminating the need for complex mechanical recalibration procedures.
3Adaptability or versatility
If multiple optical markers are placed on different axes of the robot arm, then visibility issues are reduced, but the device complexity increases
Solution Approach 1:
Different axes of the robot arm are selected for marker placement based on their specific visibility characteristics. The system strategically places markers on axes that are most likely to remain visible in different working positions, optimizing visibility coverage without uniformly increasing the number of markers on all components.
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 significantly increases accuracy by combining image data with a kinematic model, solving visibility problems and reducing errors caused by temperature influences, allowing precise determination of the end effector's position and orientation in all working positions without the need for complex correlation systems.
Implementation Method 1
an optical sensor which is configured to acquire image data of the first and/or second optical marker
Data Source
AI summary
A device for acquiring a position and orientation of an end effector of a robot is provided. The robot has a robot arm with axes coupled to one another by joints. The end effector is arranged on an end of the robot arm, optical markers are arranged on first and second axes, and a number of joints between the end effector and the first axis is lower than a number of joints between the end effector and the second axis. An optical sensor acquires image data of the optical markers. A storage device stores a kinematic model of the robot arm. An evaluation device, in a first case, determines a first position of a first optical marker and the position and orientation of the end effector and, in a second case, a second position of a second optical marker and the position and orientation of the end effector.