Extended Stroke Position Sensor Using Waveguide Saturation
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Solution Overview
Problem
Conventional non-contacting position sensors, such as Hall sensors, face limitations in stroke length and accuracy beyond 20mm, requiring complex and expensive systems, and are prone to measurement inaccuracies in fast-moving applications and environments like oil or liquids.
Innovation Solution
An extended stroke position sensor using a waveguide with a spiral-wound connector, a signal generator, and a magnetically soft material, which induces localized saturation to create an impedance discontinuity, allowing phase and time measurements for precise magnet position determination, while being electrically shielded to reduce environmental interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall or magnetostrictive sensors are used for position measurement, then non-contacting measurement is achieved, but the stroke length is limited to about 20mm with reduced sensitivity and accuracy beyond this length
Solution Approach 1:
The patent transitions from direct magnetic field sensing in one dimension to electromagnetic wave propagation in a waveguide structure, adding spatial dimensionality to the measurement approach. The waveguide extends the measurement capability along its length while maintaining signal integrity through controlled electromagnetic propagation.
Solution Approach 2:
The waveguide acts as an intermediary between the magnet and the sensing system. Instead of directly sensing the magnetic field over long distances, the system uses electromagnetic waves propagating through the waveguide as a mediator to transmit position information from the magnet location to the measurement point.
2Measurement precision
If the magnet length is increased to match the stroke length for accurate measurement, then measurement coverage is improved, but the cylinder size must be increased
Solution Approach 1:
The waveguide structure allows the sensing system to extend along the stroke length without requiring a proportional increase in magnet size or cylinder volume. The electromagnetic wave propagation along the waveguide provides measurement coverage over the extended stroke length while maintaining a compact overall structure.
3Length of moving object
If magnetostrictive magnet-waveguide solution with torque pulse is used, then extended measurement range is achieved, but measurement inaccuracies occur in fast-moving applications due to sound speed limitations
Solution Approach 1:
The patent changes the propagation mechanism from mechanical torque pulse transmission at sound speed to electromagnetic wave propagation at the speed of light. This parameter change in wave propagation speed enables accurate measurement in fast-moving applications while maintaining extended measurement range.
4Adaptability or versatility
If position sensors are designed to detect liquid level by interacting with local environment, then liquid level detection is achieved, but measurement accuracy is affected in environments containing oil or other liquids
Solution Approach 1:
The patent extracts the sensing mechanism from direct interaction with the liquid environment. By using electromagnetic wave propagation through the waveguide that is shielded from or isolated from the liquid medium, the system eliminates the harmful interaction between the sensing field and the liquid, thereby maintaining measurement accuracy in liquid-containing environments.
Solution Approach 2:
The waveguide structure serves as an intermediary that isolates the electromagnetic sensing field from direct contact with liquid environments. This mediator protects the measurement system from environmental interference while still enabling position detection.
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 position measurement over extended lengths without environmental interference, improving sensitivity and accuracy, and reducing the need for complex systems, even in fast-moving and liquid-containing environments.
Implementation Method 1
A magnet is provided which is closely positioned to the magnetic material and which is relatively movable thereto. The magnet is of sufficient strength to induce a localized full or partial magnetic saturation in the magnetic material.
Implementation Method 2
The local saturation in the magnetic material causes an impedance discontinuity in the waveguide and creates a reflection point for a signal in the waveguide.
Data Source
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AI summary
A method of obtaining position information and system comprising: a waveguide (12, 112); a quantity of soft or semi-soft magnetic material (14) positioned in close proximity to the wave (14, 114), a magnet (22), movable relative to the waveguide and magnetic material, closely positioned to the magnetic material and configured to generate a local magnetic field sufficient to locally saturate magnetic material, wherein the local magnetic field configures to create a reflection point on the waveguide to reflect the first signal, a signal generator (20, 40) for impressing a determinable first signal upon the waveguide at a first location and a signal receiver (22, 42), located proximate the first position for sensing a characteristic of the first signal or its reflection; a processor or electric circuit for correlating the sensed characteristic to the relative position of the magnet.