Laser Tracker Calibration Fixture for Stable Reference Lengths
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Solution Overview
Problem
Current methods for calibrating laser trackers are time-consuming and prone to inaccuracies due to 'fixturing effects' such as gravity, loading, and thermal expansion, making it difficult to maintain precise and accurate positioning and orientation of measuring points.
Innovation Solution
A calibration and testing system utilizing a spherically mounted retro-reflective laser tracker target coupled with a lightweight, rigid carbon fiber composite artifact, supported by a kinematic mount system that minimizes elastic deformations and allows for easy orientation and alignment, using a ring brake and yoke mechanism for secure holding and alignment accessories for precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods using heavy artifacts and fixturing systems are used, then measurement accuracy can be maintained, but the calibration process becomes time-consuming and prone to fixturing effects
Solution Approach 1:
The patent extracts the measuring points from a traditional fixed artifact and relocates them to a portable artifact that can be independently positioned. This removes the artifact from constraints of heavy fixturing systems, eliminating fixturing effects while maintaining measurement accuracy through direct positioning of the portable artifact at desired locations.
Solution Approach 2:
The patent introduces a portable artifact as an intermediary between the laser tracker and the object being measured. This portable artifact carries the measuring points and can be freely positioned without requiring complex fixturing, thereby reducing calibration time while maintaining precision through its stable, portable design.
2Stability of the object's composition
If traditional fixturing systems are used to hold measuring points, then positioning stability can be achieved, but fixturing effects such as gravity, loading, and thermal expansion cause inaccuracies
Solution Approach 1:
The patent extracts the measuring points from traditional fixed fixturing systems and relocates them to a portable artifact that is not constrained by heavy fixturing. This eliminates fixturing effects including gravity-induced deformation, loading effects, and thermal expansion from fixturing components, while maintaining positioning stability through the portable artifact's inherent stability.
Solution Approach 2:
The patent changes the physical parameters of the measurement system by using a portable artifact with specific material properties and geometric design that minimize thermal expansion and maintain dimensional stability. This allows the measuring points to maintain stable positions without being subject to fixturing-induced parameter variations.
3Measurement precision
If calibrated artifacts are used to establish reference lengths, then measurement accuracy is improved, but thermal expansion and contraction affect the reference length stability
Solution Approach 1:
The patent changes the material parameters of the portable artifact by selecting materials with low thermal expansion coefficients and designing the artifact geometry to minimize thermal effects. This allows the reference length to remain stable across temperature variations, maintaining both accuracy and stability without requiring heavy fixturing or environmental control.
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 quick and accurate calibration of laser trackers by reducing fixturing effects and thermal uncertainties, improving positioning repeatability and maintaining accurate reference lengths, thus enhancing the precision and efficiency of measurement systems.
Implementation Method 1
a spherically mounted retro-reflective laser tracker target coupled with a lightweight, rigid carbon fiber composite artifact
Implementation Method 2
laser trackers are capable of providing extreme precision and accuracy, even when measuring the dimensions of large objects
Implementation Method 3
reducing fixturing effects and thermal uncertainties, improving positioning repeatability and maintaining accurate reference lengths
Implementation Method 4
supported by a kinematic mount system that minimizes elastic deformations
Data Source
AI summary
A system and method of calibrating a laser tracker is provided. The system includes a support system for quickly and easily moving an artifact to a desired position and orientation and for holding the artifact in the position and orientation. An adjustable alignment mirror is coupled to a first end of the artifact so that the more accurate ranging system of the laser tracker can be isolated to determine a reference length of the artifact. Additional measurements are then taken to exercise one or more error source within the tracker. The support system includes a positioner and a support beam for positioning and supporting the artifact. The artifact is coupled to the support beam using kinematic clamps that are designed to reduce or eliminate errors associated with over-constraining the artifact. The artifact is movable between a deployed configuration for use and a stowable configuration for ease of storage and transportation.