Cable-Driven Coordinate Measuring Device for Micron Precision
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Solution Overview
Problem
Existing coordinate measuring apparatuses face challenges in achieving high precision due to multiple components and sensitivity to temperature variations, with bulky and complex designs limiting their effectiveness.
Innovation Solution
A lightweight coordinate measuring device utilizing a base with a platform and pillar, a carriage, and a cross-arm translating along orthogonal axes, driven by cable and pulley mechanisms with electrical motors, and optionally manual operation, incorporating encoders for precise positioning and a sensing element like a probe or imaging apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a probe is mounted on an articulated, multi-axis measurement arm with multiple moving parts, then the device can be lightweight and portable, but high precision is seldom achieved and the device is sensitive to temperature variations
Solution Approach 1:
The patent replaces the traditional articulated mechanical arm with a cable-driven parallel mechanism where cables transmit motion from motors to a common carriage. This substitution eliminates the temperature-sensitive joints and linkages of conventional articulated arms while maintaining lightweight construction and achieving micrometer-level precision through direct mechanical coupling and encoder feedback.
2Measurement precision
If a multi-axis adjustable support with computer-controlled motors is used, then higher precision can be provided, but the device becomes bulkier, heavier and more complex
Solution Approach 1:
The patent merges the functions of multiple independent motors into a single motor that drives a common carriage through cable mechanisms. The carriage simultaneously positions the probe along three orthogonal axes (X, Y, and Z) by translating and rotating within a compact housing, thereby reducing the number of separate motor units and overall device complexity while maintaining multi-axis positioning capability and precision.
3Measurement precision
If a complex routing of cables is used to accommodate displacement of primary moving elements, then the device can maintain positioning accuracy, but the device structure becomes more complex
Solution Approach 1:
The patent resolves cable routing complexity by transitioning to a three-dimensional cable arrangement where cables are routed through the thickness of the housing and attached to the carriage in a vertical plane. This dimensional reorganization allows the cables to accommodate the carriage's displacement along orthogonal axes without requiring complex surface routing, thereby simplifying the overall structure while maintaining positioning accuracy through direct cable-carriage coupling.
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 device achieves diametral accuracy of no greater than two microns and linear accuracy of no greater than five microns, providing precise spatial measurements while being portable and adaptable for robotic applications.
Implementation Method 1
encoders for indicating the linear position of said carriage along said first axis
Implementation Method 2
the linear position of said arm along said second axis
Implementation Method 3
the angular position of said housing in relation to said base
Implementation Method 4
an encoder for indicating the angular position of said body about said third axis
Data Source
AI summary
A coordinate measuring device comprises a housing movably supported on a base and mounting a vertical pillar along which rides a carriage engaged by a horizontally translating arm. A turret at each end of the arm houses a rotating body connected to a probe. The rotation of the base, the vertical movement of the carriage, the horizontal movement of the arm and the rotation of the probes are driven by motors in the housing. The rotation of the motors are transmitted by a cable and pulley assembly to the arm and carriage. The cable controlling the transversal movement of the arm has its opposite ends attached to the opposite extremity of the arm, and is run respectively up and down the portion of the pillar above and below the carriage in order to maintain constant lengths and tension of the cables as the carriage moves up and down the pillar. The rotation of the probes and that of the base are coordinated to keep the probes at a constant angle in relation to the measured surface. Tools such as a laser beam emitter may be substituted for the probes turning the device into a robot. The motors can be omitted and the probe brought manually on the locus to be measured.