Capacitive Linear Encoder Absolute Positioning
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Solution Overview
Problem
Capacitive linear encoders face errors in absolute position localization due to noisy scanning signals and require complex error correction measures, especially for long measuring paths, which are costly and precision-dependent.
Innovation Solution
A capacitive linear encoder design with multiple offset coupling signal phases, capacitive position reference markers, and simplified electrical shielding, allowing for incremental position determination and verification using a capacitive operating principle, reducing the need for precise scale manufacturing and complex error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex error correction measures and electrical shielding are used to improve absolute position accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-defining phase permutation intervals (P-intervals) in the scale structure, where each interval contains a specific sequence of phases. This pre-structured approach allows the reading head to inherently identify position references without requiring complex real-time error correction algorithms, thus improving absolute position accuracy while reducing device complexity
Solution Approach 2:
The patent uses copying by creating multiple identical phase permutation intervals along the scale. Each P-interval contains the same phase sequence pattern, allowing the reading head to identify position references by recognizing these repeated patterns. This approach provides robust absolute positioning without complex shielding or error correction measures
2Measurement precision
If high precision manufacturing is used to reduce position determination errors, then measurement precision improves, but manufacturing cost increases
Solution Approach 1:
The patent changes parameters by using electrical phase sequences instead of physical dimensional variations to encode position information. The phase permutation intervals use temporal phase relationships (electrical parameters) rather than requiring extremely precise physical spacing, allowing accurate position determination with relaxed manufacturing tolerances
Solution Approach 2:
The patent replaces mechanical precision requirements with electrical signal processing. Instead of relying on mechanically precise feature spacing, the system uses capacitive coupling and phase-based signal evaluation, substituting mechanical precision demands with electrical measurement and computation
3Measurement precision
If magnetic or inductive position reference markers are used, then absolute reference point detection improves, but energy consumption and structural complexity increase
Solution Approach 1:
The patent applies universality by making the capacitive coupling system serve multiple functions: both incremental position measurement and absolute reference point detection. The same capacitive coupling electrodes and phase permutation structure used for incremental measurement also encode absolute position references, eliminating the need for separate magnetic or inductive reference markers and reducing overall system energy consumption
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 accurate and cost-effective absolute position determination with reduced precision demands on the scale, enabling flexible scale modifications and energy-efficient operation, while eliminating the need for complex shielding and specialized receiver electrodes.
Implementation Method 1
time-varying coupling signals are exchanged between the first and second coupling electrodes by capacitive coupling
Data Source
Figure 1~2b
Figure 2c
Figure 3
AI summary
A capacitive linear encoder (100) for determining positions, comprising a scale (3) and a read head (1) for capacitively scanning the scale (3), wherein the scale (3) and the read head (1) are movable relative to each other. The scale (3) and the read head (1) have first and second transfer electrodes. The read head (1) has shielding electrodes for electrically shielding the first transfer electrodes.