Capacitive Encoder Layout for Absolute Rotary and Linear Position
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Solution Overview
Problem
Existing capacitative encoders are limited in their ability to detect absolute angular and linear positions due to mechanical wear, large dimensions, and the need for electrical connections, and they are not suitable for miniaturization or use as both rotary and translational devices.
Innovation Solution
A capacitative encoder design featuring a stator with multiple conductive sectors forming capacitors, a mobile element with a dielectric indicator that covers all capacitors except one, and a control unit to detect capacity variations, allowing for absolute position detection without electrical connections and enabling both rotational and translational functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical rotary friction contacts are used in encoders, then electrical signals can be generated corresponding to angular position, but the contact elements suffer from rapid wear and large dimensions
Solution Approach 1:
The patent replaces mechanical rotary friction contacts with a capacitive sensing system. The mobile element with conductive sectors forms capacitors with stator armatures, and position is detected by measuring capacitance variations rather than through mechanical contact. This eliminates wear while maintaining position detection capability.
Solution Approach 2:
The patent introduces a dielectric layer between the mobile element and stator armatures as an intermediary. This dielectric enables capacitive coupling for position sensing without requiring direct mechanical or electrical contact, thus eliminating wear while allowing position information to be transmitted.
2Measurement precision
If optical encoders are used for position detection, then angular position can be measured, but the device dimensions are difficult to miniaturize in the direction of the rotor axis
Solution Approach 1:
The patent changes the sensing parameter from optical to capacitive. By measuring capacitance variations between mobile element sectors and stator armatures, the system achieves angular position measurement with a much reduced axial dimension, as capacitive sensing requires minimal spacing compared to optical systems.
3Measurement precision
If capacitative encoders use multiple stator armatures, then resolution can be improved, but only one stator armature contributes to capacity variation analysis while others are screened by the conductive section
Solution Approach 1:
The patent inverts the traditional approach by making the mobile element conductive rather than the stator. The mobile element's conductive sectors form capacitors with all stator armatures simultaneously, ensuring that all armatures contribute to the capacitance measurement and none are screened, thus improving resolution without increasing 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 design enhances resolution, eliminates mechanical wear, and allows for significant size reduction, enabling reliable, easy-to-make encoders that can function as both rotary and push-button devices without electrical connections, improving position detection accuracy and versatility.
Implementation Method 1
an absolute angular and/or linear encoder based on a capacitative coupling principle
Implementation Method 2
detect the capacity of each capacitor generated by the conductive sectors
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An absolute capacitative encoder (1) comprising: a PCB (2), a plurality of conductive sectors (3) that generate capacitors (C), a rotor (6) mounted in revolving and/or axially translating mode with respect to the PCB (2), said rotor (6) being made of dielectric material and having a peripheral slot (61) in register with said conductive sectors, a control unit (4) electrically connected to said conductive sectors (3) in such manner to detect the capacity of each capacitor (C) generated by the conductive sectors, said control unit (4) being set in such manner to detect the capacity variation between the capacitors during the rotation and/or axial translation of the rotor (6) in order to detect the angular and/or axial position of the rotor.