Retroreflector-Based Coordinate Transformation for Articulated-Arm CMM Relocation
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Solution Overview
Problem
Articulated-arm coordinate measuring machines (CMMs) are limited in measuring hidden points and have a smaller measurement volume compared to laser trackers, lacking a convenient method to relocate and seamlessly integrate measurements across different positions.
Innovation Solution
A system combining a laser tracker, a retroreflector, and a moveable articulated-arm CMM, where the retroreflector is attached to the CMM, allowing measurements in both coordinate systems to be transformed into a common frame of reference, enabling the CMM to be relocated and measure positions accurately over a larger volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If an articulated-arm CMM is used to measure hidden points, then the ability to measure hidden points is improved, but the measurement volume is limited
Solution Approach 1:
A retroreflector is introduced as an intermediary object that can be measured by both the articulated-arm CMM and the laser tracker. The retroreflector serves as a common reference point that enables coordinate transformation between the two measurement systems, allowing the CMM to access hidden points while the laser tracker provides large-volume positioning.
Solution Approach 2:
The patent combines two different measurement systems (articulated-arm CMM and laser tracker) into a hybrid measurement approach. By merging the capabilities of both systems and using coordinate transformation through the retroreflector, the system achieves both hidden point measurement capability and large measurement volume coverage.
2Volume of stationary object
If a laser tracker is used to increase measurement volume, then the measurement volume is improved, but the ability to measure hidden points is reduced
Solution Approach 1:
The retroreflector acts as an intermediary that the laser tracker can measure from a distance while also being accessible to the articulated-arm CMM for hidden point measurement. This intermediary object bridges the gap between the two systems' capabilities.
Solution Approach 2:
The retroreflector serves multiple functions: it acts as a target for the laser tracker's distance and angle measurements, and simultaneously serves as a measurable point for the articulated-arm CMM. This multi-functionality allows a single object to enable both measurement systems to work together effectively.
3Volume of stationary object
If the articulated-arm CMM is relocated to measure different positions, then the measurement coverage is improved, but the integration of measurements across positions becomes complex
Solution Approach 1:
The retroreflector serves as a stable intermediary reference object that remains in the same position while the CMM is relocated. By measuring the retroreflector's coordinates in different CMM positions, the system establishes transformation relationships between coordinate systems, simplifying the integration process.
Solution Approach 2:
The system creates a coordinate transformation model (a mathematical copy or representation) that maps measurements from different CMM positions into a common coordinate system. This transformation model allows seamless integration of measurements taken at different positions without complex manual calibration.
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 convenient and accurate measurement of hidden points by transforming coordinates from the CMM and laser tracker systems into a common frame, allowing seamless relocation and integration of data across different positions, improving measurement efficiency and accuracy.
Implementation Method 1
The laser tracker determines the coordinates of the point by measuring the distance and the two angles to the retroreflector
Implementation Method 2
sends a laser beam to a retroreflector target that is in contact with the point
Data Source
AI summary
A measurement apparatus, system and method for measuring objects which is easily relocatable about the object is described. The system uses an articulated-arm coordinate measuring machine (CMM) and a laser tracker. A retroreflector for use with the laser tracker is located on the arm of the articulated-arm (CMM). A common coordinate frame of reference can be determined for the CMM and the laser tracker so that the CMM can be moved. Also, points hidden from the laser tracker can be measured for example with the CMM.