Double-Layer Floating Grating Head for High-Precision Displacement
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Solution Overview
Problem
Existing grating measurement devices face challenges in high-precision six-degree-of-freedom measurement, particularly for long-stroke applications, due to environmental sensitivity and error accumulation issues in laser interferometry, and slow calculation speeds in redundant and collaborative sensing methods.
Innovation Solution
A grating displacement measurement device using a double-layer floating reading head with a substrate, light-through member, first and second measurement grating groups, and a control unit, where reading components collect position information from both grating layers to generate position parameters and calculate translational and rotational displacements with high precision and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If laser interferometry is used for long-stroke measurement, then measurement capability is improved, but measurement precision deteriorates due to environmental sensitivity
Solution Approach 1:
The patent replaces laser interferometry (optical system sensitive to environment) with grating interferometry using zero expansion material substrates (mechanical system with environmental immunity). The grating substrate made of zero expansion material eliminates sensitivity to temperature, humidity, and air pressure changes, maintaining measurement precision over long strokes without requiring strict environmental control.
2Productivity
If multiple reading heads are used for collaborative sensing measurement, then measurement speed is improved, but measurement precision deteriorates due to error accumulation
Solution Approach 1:
The patent divides the measurement system into two independent layers: a first measurement grating layer and a second measurement grating layer, each with their own reading heads. The first reading head measures displacement of the first grating, and the second reading head measures displacement of the second grating. By segmenting the measurement into independent layers rather than using multiple reading heads on a single grating, the system achieves fast measurement speed while eliminating error accumulation through independent measurement channels.
3Reliability
If redundant measurement with three or more reading heads is used, then measurement completeness is improved, but productivity deteriorates due to slow calculation speed
Solution Approach 1:
The patent extracts and eliminates the need for solving high-order nonlinear equation groups by using a simplified two-layer grating configuration. Instead of using three or more reading heads that require redundant measurement and complex nonlinear calculations, the system uses two reading heads with two separate grating layers, where each reading head independently measures its respective grating. This extraction of the complex calculation requirement maintains measurement completeness while dramatically improving calculation speed and productivity.
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
Enables high-speed and high-precision detection of translational and rotational displacements across multiple degrees of freedom, reducing error accumulation and environmental sensitivity, suitable for long-stroke measurements in compact systems.
Implementation Method 1
grating interferometry
Data Source
AI summary
Disclosed are a grating displacement measurement device and a grating displacement measurement method using a double-layer floating reading head, a medium, and an apparatus. A first measurement grating group is arranged on two first side edges of a substrate working surface, and a second measurement grating group is symmetrically arranged on both sides of a first reference line and close to a light-through member. A reading component is provided between a first measurement grating and a second measurement grating arranged on the same side, and each reading component is used to collect a first position information of the first measurement grating and a second position information of the second measurement grating. In the technical solutions, by using multi-channel position information output by two reading components in combination with a displacement solution algorithm.