Capacitive Position Sensor Using Dielectric Shuttle
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Solution Overview
Problem
Position sensing devices like LVDTs and RVDTs are prone to high failure rates due to environmental factors such as temperature and vibration, and are costly, especially when used in applications like fuel metering systems, where they often require specialized sourcing.
Innovation Solution
A capacitive position sensor system using a dielectric shuttle with varying dielectric constants and electrodes arranged on the actuator bore wall, which measures changes in capacitance to determine the position and direction of the shuttle, offering integrated position sensing and potential for reduced failure rates and lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LVDTs and RVDTs are used for position sensing, then measurement precision is achieved, but reliability deteriorates due to high failure rates from temperature and vibration
Solution Approach 1:
The patent replaces the mechanical core components of LVDTs/RVDTs (magnetic slugs, inductive coils, iron cores) with a capacitive sensing system using dielectric shuttles and electrode arrays. This substitution eliminates the mechanical elements that are susceptible to temperature and vibration damage, while maintaining position measurement capability through electrical field-based capacitance sensing.
Solution Approach 2:
The patent changes the fundamental measurement parameter from inductive coupling (magnetic field-based) to capacitive coupling (electrical field-based). By measuring capacitance changes between electrode subsets as the dielectric shuttle moves, the system achieves position sensing without the mechanical vulnerabilities of traditional inductive transformers.
2Measurement precision
If LVDTs and RVDTs are used for position sensing, then measurement precision is achieved, but device complexity increases
Solution Approach 1:
The patent divides the sensing system into modular components: a dielectric shuttle attached to the actuator and stationary electrode arrays mounted on the actuator bore wall. This segmentation simplifies construction by allowing independent optimization of moving and stationary parts, and facilitates integration into the fuel metering system assembly.
Solution Approach 2:
The dielectric shuttle serves multiple functions: it is attached to the actuator for position tracking, provides the dielectric material necessary for capacitance sensing, and acts as a mechanical coupling element. This multi-functionality reduces the number of separate components needed, thereby reducing overall device complexity.
3Measurement precision
If LVDTs and RVDTs are used for position sensing, then measurement precision is achieved, but cost increases
Solution Approach 1:
The patent employs standard capacitive sensing components (electrodes, dielectric materials) that are significantly cheaper than the specialized inductive coils and magnetic components of LVDTs/RVDTs. These components can be manufactured using conventional techniques and are not limited to specialized suppliers, thereby reducing cost.
Solution Approach 2:
By replacing expensive mechanical components (magnetic slugs, precision-wound inductive coils, iron cores) with simpler capacitive elements, the patent achieves cost reduction. The capacitive system uses basic electrical components that are easier and cheaper to manufacture at scale.
4Measurement precision
If LVDTs and RVDTs are used for position sensing, then measurement precision is achieved, but weight increases
Solution Approach 1:
The patent replaces heavy magnetic components (iron cores, magnetic slugs, substantial inductive coils) with lightweight capacitive elements. The dielectric shuttle and electrode arrays have significantly lower mass than the ferromagnetic materials used in LVDTs/RVDTs, thereby reducing the weight of the fuel metering system assembly.
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 capacitive position sensor system provides accurate position measurement with reduced susceptibility to environmental factors and lower costs, potentially replacing traditional LVDTs and RVDTs by using less expensive and more robust materials, while maintaining or improving reliability.
Implementation Method 1
A set of electrodes is arranged such that movement of a dielectric shuttle causes the capacitance between subsets of the electrodes to change
Implementation Method 2
A capacitive position sensor system using a dielectric shuttle with varying dielectric constants
Data Source
AI summary
A transducer includes a plurality of electrodes and a dielectric shuttle. The dielectric shuttle passes between a subset of the electrodes, modifying the capacitance between them. By measuring the capacitance of subsets of the electrodes, the position of the dielectric shuttle may be determined.