Laser Tracker Calibration Fixture With Kinematic Artifact Mounting
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Solution Overview
Problem
Current methods for calibrating laser trackers are time-consuming and prone to inaccuracies due to 'fixturing effects' and thermal expansion uncertainties, making it difficult to achieve precise and repeatable 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 positioning and alignment accessories for accurate reference length determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional fixtures and mounting systems are used to position measuring points, then the measuring points can be securely held, but elastic deformations and fixturing effects cause positioning inaccuracies and reduce measurement precision
Solution Approach 1:
The patent removes traditional fixtures and mounting systems from the calibration setup. Instead of using external fixtures to hold measuring points, the system uses freely suspended artifacts with attached retro-reflective targets, eliminating the harmful elastic deformations and fixturing effects that traditional mounting systems introduce.
Solution Approach 2:
The patent employs counterweights to balance the artifacts, preventing them from sagging or deforming under their own weight. This counteracts the gravitational force that would otherwise cause elastic deformations, maintaining the artifacts' dimensional stability and measurement accuracy.
2Reliability
If artifacts are held in fixed positions using traditional mounting methods, then they can be stabilized, but thermal expansion uncertainties and fixturing effects compromise measurement reliability
Solution Approach 1:
The patent transitions from static, fixed mounting to a dynamic system where artifacts are freely suspended and can move independently. This dynamic approach allows the artifacts to naturally compensate for thermal expansion and other environmental variations, improving calibration reliability without introducing fixturing effects.
Solution Approach 2:
The patent introduces wire suspensions as intermediaries between the support structure and the measuring point artifacts. These wire suspensions provide minimal constraint while allowing the artifacts to maintain their dimensional stability, isolating them from thermal expansion uncertainties in the mounting structure.
3Measurement precision
If complex alignment procedures are used to position measuring points, then measurement accuracy can be improved, but the calibration process becomes time-consuming and reduces productivity
Solution Approach 1:
The patent replaces complex mechanical alignment procedures with an optical alignment system using laser trackers and retro-reflective targets. The laser tracker automatically measures the positions of the targets, eliminating the need for manual mechanical alignment while maintaining high measurement accuracy and significantly reducing calibration time.
Solution Approach 2:
The patent creates a universal calibration system where the same freely suspended artifact with retro-reflective targets can be used for multiple measurement configurations and orientations. This multi-functional approach eliminates the need for different fixtures and alignment procedures for different measurement scenarios, improving both accuracy and productivity.
4Stability of the object's composition
If heavy-duty fixtures are used to ensure stable positioning, then measurement stability is improved, but the system complexity and difficulty of operation increase
Solution Approach 1:
The patent uses thin wire suspensions instead of heavy-duty fixtures to hold the measuring point artifacts. These wire suspensions provide sufficient stability for precise measurement while being lightweight and easy to adjust, dramatically simplifying system operation and setup compared to rigid fixture systems.
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
The system 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 laser tracker measurements.
Implementation Method 1
a spherically mounted retro-reflective laser tracker target
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.