Coordinate Positioning Leg Constraint for Gravity-Stable Metrology
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Solution Overview
Problem
Non-Cartesian coordinate positioning machines face challenges in maintaining the accuracy of metrology measurements due to gravitational-induced bending of extendable legs, which affects the orientation of encoder scales, leading to measurement errors.
Innovation Solution
A constraint member is used to maintain a predetermined part, such as an encoder scale, in a substantially constant orientation relative to gravity within the working volume, preventing unwanted rotation and bending that can distort measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If extendable legs are used to position components in a non-Cartesian coordinate machine, then the machine can achieve complex positioning and orientation capabilities, but gravitational bending of the legs causes orientation changes in encoder scales leading to measurement errors
Solution Approach 1:
A constraint member is introduced as an intermediary element between the extendable leg and the encoder scale. This constraint member prevents unwanted rotation and bending of the leg, thereby maintaining the encoder scale's orientation relative to gravity and eliminating measurement errors while preserving the leg's extendability and positioning capability
Solution Approach 2:
The patent changes the physical state or parameters of the extendable leg by adding rotational constraints. The constraint member limits the leg's rotational degrees of freedom, maintaining the encoder scale at a constant orientation angle relative to gravity throughout the leg's extension and retraction movements, thus resolving the measurement accuracy issue
2Ease of operation
If the extendable leg is allowed to move freely during extension, then the machine operates with greater flexibility, but the encoder scale orientation varies due to gravitational bending
Solution Approach 1:
The constraint member is designed to dynamically maintain the encoder scale's orientation throughout the leg's range of motion. It allows the leg to extend and retract freely while actively preventing rotation that would change the encoder scale's orientation relative to gravity, thus maintaining measurement precision across all operational positions
3Device complexity
If no constraint is applied to the extendable leg, then the structure remains simple and inexpensive, but measurement errors occur due to gravitational-induced bending
Solution Approach 1:
A relatively simple constraint member is introduced as an intermediary component that prevents unwanted rotation of the extendable leg. This constraint member maintains the encoder scale's orientation without requiring complex active control systems or redundant metrology infrastructure, thus improving measurement accuracy with minimal added complexity
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 consistent and accurate metrology measurements by maintaining the orientation of metrology elements relative to gravity, reducing errors caused by gravitational bending and improving positional accuracy and repeatability.
Implementation Method 1
maintain a predetermined part, such as an encoder scale, in a substantially constant orientation relative to gravity
Data Source
Figure 1
Figure 2A~3B
Figure 4
AI summary
A non-Cartesian coordinate positioning machine is provided that comprises an extendable leg assembly (60) for positioning a component such as a measurement probe (14) within a working volume of the machine, and a constraint member (50) associated with the extendable leg assembly (60) for providing a predetermined part (10) of the extendable leg assembly (60) with substantially a same orientation relative to gravity for a same position of the component (14) within the working volume. In a preferred embodiment, the orientation relative to gravity is maintained substantially constant, so that a plane defined by the predetermined part (10) is substantially aligned with gravity, as the component (14) is moved around the working volume.