Extendable Leg Encoder Constraint for Precise Coordinate Positioning
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Solution Overview
Problem
Non-Cartesian coordinate positioning machines face inaccuracies due to gravitational bending affecting encoder scales mounted on extendable legs, leading to measurement errors as the orientation of these scales changes with leg adjustments.
Innovation Solution
A constraint member is used to maintain the encoder scale in a substantially constant orientation relative to gravity, preventing unwanted rotation and bending-induced distortions by constraining its motion within a defined plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the encoder scale is mounted on the extendable leg, then the leg extension can be measured, but the encoder scale orientation changes with leg adjustment causing measurement errors
Solution Approach 1:
A constraint member is introduced as an intermediary between the extendable leg and the encoder scale. This constraint member maintains a constant orientation relationship with the encoder scale while allowing the leg to extend and retract, thereby mediating between the leg's motion and the encoder scale's need for stable orientation to eliminate measurement errors caused by orientation changes
2Measurement precision
If the encoder scale is mounted on the extendable leg, then the position can be monitored, but gravitational bending causes distortion of the encoder scale
Solution Approach 1:
The constraint member serves as a mediator that supports the encoder scale in a fixed orientation relative to gravity, preventing the gravitational bending that would otherwise occur when the encoder scale is directly mounted on the extendable leg. This intermediary structure eliminates the harmful gravitational effect while preserving the measurement function
3Adaptability or versatility
If the extendable leg is allowed to rotate freely, then the working volume can be accessed, but the encoder scale orientation varies leading to measurement errors
Solution Approach 1:
The system is segmented into two independent functional parts: the extendable leg that provides motion and accessibility to the working volume, and the encoder scale that is constrained to maintain constant orientation for accurate measurement. The constraint member creates this segmentation by coupling the two parts while allowing independent optimization of each function
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 solution ensures accurate and repeatable measurements by maintaining the encoder scale's orientation relative to gravity, reducing measurement errors caused by gravitational bending and allowing for precise positioning within the working volume.
Implementation Method 1
A constraint member associated with the extendable leg assembly for providing a predetermined part of the extendable leg assembly with substantially a same orientation relative to gravity
Data Source
Figure 1
Figure 2A~3B
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AI summary
An extendable leg assembly for a non-Cartesian coordinate positioning machine is described. The extendable leg assembly comprises an elongate member (66), with an end of the elongate member (66) being provided with a bearing arrangement having three contact points, or at least substantially point-like contact surfaces, for bearing against an at least part spherical bearing surface provided on the machine, where a plane defined by the contact points or areas is substantially perpendicular to a longitudinal axis of the elongate member (66).