Positioning Device Articulation Constraint for Accuracy
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Solution Overview
Problem
Existing positioning devices with notch-type flexure hinges are mechanically underconstrained, leading to reduced positioning accuracy during large strokes or displacement distances, which is inadequate for applications requiring high precision.
Innovation Solution
A positioning device with six degrees of freedom, utilizing three pairs of length-variable electrically driven leg elements connected via articulation elements such as cardan, universal, or ball joints, which allow pivotal and tilting movements while preventing rotational movement about the longitudinal axis, ensuring high rigidity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If notch-type flexure hinges are used to provide degrees of freedom, then the positioning device can achieve arbitrary pivotal and tilting movements, but the system becomes mechanically underconstrained leading to reduced positioning accuracy during large strokes
Solution Approach 1:
The invention changes the constraint parameters by using articulation elements with exactly two perpendicular rotation axes, transforming the system from underconstrained (flexure hinge allowing 3+ DOF) to properly constrained (exactly 2 DOF per articulation element). This parameter change ensures mechanical unequivocal constraint while maintaining the necessary mobility for positioning operations.
2Ease of operation
If flexure hinges allow rotations about longitudinal axis, then the articulation flexibility is increased, but additional rotational movements cause instability and reduce positioning precision
Solution Approach 1:
The invention extracts and removes the unwanted rotational degree of freedom about the longitudinal axis by designing articulation elements with exactly two perpendicular rotation axes. This extraction eliminates the source of instability while preserving the necessary pivotal and tilting movements for positioning operations.
3Length of moving object
If rotational drives are used for length-variable leg elements, then large displacement distances are achieved, but rotational drives cause unintended leg element rotation about longitudinal axis
Solution Approach 1:
The invention applies preliminary action by designing the articulation elements with exactly two perpendicular rotation axes before the rotational drive is activated. This preliminary constraint design prevents unintended rotation about the longitudinal axis from occurring in the first place, eliminating the need for additional corrective precautions during operation.
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 solution provides a mechanically constrained system with enhanced positioning accuracy and larger displacement capabilities, allowing precise adjustments even during large strokes, and supports the use of rotational drives without additional precautions.
Implementation Method 1
each of the two articulation elements associated with a leg element has only two axes of rotation, which are arranged perpendicular to each other, so that the articulation elements allow pivotal movements or tilting movements of the respective leg element
Data Source
AI summary
A positioning device is disclosed which can include a base and a positioning element, which is configured to be adjusted with respect to six degrees of freedom relative to the base, wherein the positioning element is coupled to the base via at least three pairs of length-variable and electrically driven leg elements, and each leg element is connected, at its respective ends, to the base and the positioning element via an articulation element. A respective pair of legs projects through another pair of legs and each pair of legs is arranged perpendicular to the respective other pairs of legs. According to exemplary embodiments, each of the articulation elements associated with a leg element has only two axes of rotation (DA), which are arranged perpendicular to each other, so that the articulation elements allow pivotal movements of each respective leg element in precisely two planes that are perpendicular to each other and run through a longitudinal axis of the leg element, and at the same time prevent a rotational movement about a longitudinal axis of the leg element.