Inductive Position Sensor Using Resonant Intermediate Device
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Solution Overview
Problem
Existing displacement detectors, such as LVDTs and Inductosyns, are expensive, delicate, and limited in application due to their requirement for precise winding and electrical connections, which restricts their use in high-speed and multi-target position measurements.
Innovation Solution
A low-cost, high-speed, and robust inductive displacement detector using transmit and receive windings with an electrically resonant intermediate device comprising a capacitor and inductor in series, where the inductor's width varies transversely to the displacement axis, allowing for accurate measurement of relative positions between two bodies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional LVDT or Inductosyn constructions are used, then measurement accuracy is maintained, but device cost, weight, and complexity increase due to precision winding requirements
Solution Approach 1:
The patent replaces complex precision windings with planar serpentine windings that replicate the functional effect through a simplified geometric pattern. The serpentine configuration copies the inductive coupling function of traditional windings while eliminating the need for manual precision winding, thereby reducing manufacturing complexity and cost while maintaining measurement accuracy.
Solution Approach 2:
The invention changes the physical parameters of the winding structure from three-dimensional coiled windings to two-dimensional planar serpentine traces. This parameter change transforms the manufacturing process from complex precision winding to simple PCB-like fabrication, significantly reducing device complexity while preserving the electromagnetic coupling function necessary for accurate position measurement.
2Ease of manufacture
If Inductosyn planar windings are used, then manufacturing cost and robustness improve, but application scope is limited due to requirement for electrical connections
Solution Approach 1:
The patent extracts the electrical connection requirement from the measurement system by using a passive target that does not need electrical connections. The measurement is achieved through electromagnetic coupling between the driven winding and the passive target, eliminating the need for sliding contacts, brushes, or complex connection mechanisms, thereby expanding application scope to high-speed and rotary applications.
Solution Approach 2:
The passive target acts as an intermediary element that transfers position information from the moving component to the stationary sensor without requiring electrical connections. The target modulates the electromagnetic field from the driven winding, enabling contactless signal transmission and significantly broadening the range of applicable scenarios including high-speed linear and rotary displacements.
3Measurement precision
If high frequency input signals are applied to achieve sufficient signal-to-noise ratio, then measurement accuracy improves, but electromagnetic emissions increase
Solution Approach 1:
The patent employs dynamic modulation where the passive target's position modulates the electromagnetic coupling between the driven winding and the output winding. This dynamic interaction creates a position-dependent signal that achieves high signal-to-noise ratio without requiring excessively high input frequencies, thereby reducing electromagnetic emissions while maintaining measurement precision.
Solution Approach 2:
The system uses periodic AC excitation of the driven winding at optimized frequencies that balance signal-to-noise ratio with electromagnetic emission levels. The periodic nature of the excitation allows for synchronous detection techniques that enhance signal extraction while limiting broadband electromagnetic emissions, resolving the contradiction between measurement accuracy and emission levels.
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 accurate and robust measurement of relative positions between multiple bodies across various topologies, including linear and rotary displacements, with improved signal-to-noise ratio and reduced electromagnetic emissions, while being cost-effective and adaptable to diverse applications.
Implementation Method 1
a first body which further comprises an arrangement of transmit and receive windings and a second body which comprises an electrically resonant intermediate device whose inductor width, measured at right angles to the measurement axis, varies such that the level of mutual inductance between the transmit and receive windings varies according to the position of the two bodies
Implementation Method 2
an electrically resonant intermediate device comprising a capacitor and inductor in series
Data Source
AI summary
A system to measure the displacement of relatively moveable bodies along an axis comprising: a resonant electrical intermediate device further comprising an inductor, whose width varies along the displacement axis, and a capacitor in electrical series which co-operates with an antenna comprising transmit and receive windings whose mutual inductance varies according to the position of the electrical intermediate device relative to the antenna.