Portal Positioning Device Crossbeam Reference Measurement
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Solution Overview
Problem
Existing positioning devices in portal designs face challenges in achieving precise position detection and control due to heat input and deformation caused by drive forces, leading to vibrations and inaccuracies in positioning, especially in applications requiring sub-20 nanometer deviations from ideal straight lines.
Innovation Solution
A positioning device with two parallel linear axes and a crossbeam system where a second, thermally and mechanically stable crossbeam serves as a reference for precise position measurement, allowing for fine positioning corrections through additional drives, eliminating deformation effects and maintaining precise positioning across all degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single crossbeam is used to carry the carriage, then the device structure is simple, but heat input and drive forces cause deformation and vibrations that reduce positioning precision
Solution Approach 1:
The crossbeam function is segmented into two independent parts: a first crossbeam that carries the carriage and handles driving functions, and a second crossbeam that serves exclusively as a stable reference for position measurement. This segmentation allows the measuring reference to be isolated from thermal and mechanical disturbances generated by the drive system.
Solution Approach 2:
The second crossbeam acts as an intermediary reference element between the moving carriage and the measurement system. It provides a stable, undisturbed reference frame for position detection, mediating between the dynamic first crossbeam and the measurement requirements without being directly affected by drive forces or heat input.
2Device complexity
If position measurement is performed relative to the first crossbeam, then the measurement system is simple, but deformation from heat and drive forces makes precise position control impossible
Solution Approach 1:
The measurement reference is separated from the driven structure. The second crossbeam provides a dedicated, stable reference for position measurement that is not coupled to the thermal and mechanical disturbances affecting the first crossbeam, enabling precise position control despite the simplicity of the overall measurement system.
3Measurement precision
If additional drives for fine positioning are added, then positioning precision in all degrees of freedom is improved, but device complexity increases
Solution Approach 1:
Additional fine positioning drives are introduced to dynamically compensate for residual errors and achieve sub-20 nanometer precision. These drives operate in all six degrees of freedom, providing active correction capabilities that adapt to varying positioning requirements while maintaining overall system functionality.
Data Source
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AI summary
A portal-type positioning device is described, comprising two linear guides (FX1, FX2) arranged parallel to each other on a base (G), which movably support a first crossbeam (FY1) and a second crossbeam (FY2) in a first direction (X). A carriage (LY) with a functional element (T) is movably supported on the first crossbeam (FY1) in a second direction (Y). Position measuring devices (Mxy, Mz, Mx, AKx1, AKx2, AKx3, AKy, AKz1, AKz2) are arranged on the carriage (LY) and on the second crossbeam (FY2) for measuring the position of the carriage (LY) relative to the second crossbeam (FY2).