Linear Displacement Sensor with Correction Coil for Offset Compensation
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Solution Overview
Problem
Existing linear-displacement sensors face inaccuracies due to tilting and changes in spacing between the sensor coil and conductive tracks, particularly in cases of lateral offset, which affects measurement precision and robustness.
Innovation Solution
A linear-displacement sensor design featuring a base element with a sensor coil and excitation coil, along with a conductive sliding element, utilizes opposite-sense partial turns and a correction coil to compensate for lateral offsets, allowing for precise measurement of relative position and minimizing errors through inductive coupling and amplitude analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor coil is used for linear displacement measurement, then the device complexity is reduced, but measurement precision deteriorates due to sensitivity to lateral offsets and spacing changes
Solution Approach 1:
The sensor coil is segmented into multiple independent coils (first sensor coil and second sensor coil) arranged at different positions. Each coil generates a measuring signal that is processed separately, allowing the system to compensate for lateral offsets and spacing variations through signal combination, thereby maintaining measurement precision while avoiding excessive complexity
Solution Approach 2:
A correction coil is introduced as an intermediary element to sense lateral offsets between the sensor coils and the conductive track. The correction coil generates a correction signal that is combined with the measuring signals to compensate for positioning errors, improving measurement precision without requiring high-precision mechanical mounting
2Reliability
If multiple sensor coils and conductive tracks are used to ensure robustness against tolerance variations, then reliability improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The sensor coils serve multiple functions: they generate the primary measuring signal for displacement detection and simultaneously provide information for lateral offset compensation when arranged in multiple positions. The correction coil also serves dual purposes by detecting lateral offsets and enabling compensation without requiring separate dedicated components for each function
Solution Approach 2:
The system changes the parameter of coil arrangement by positioning sensor coils at different lateral locations and using a correction coil at a specific position. This parametric approach allows the system to maintain reliability across tolerance variations by selecting optimal positions rather than increasing the number of components
3Measurement precision
If sensor coils are positioned closer to the conductive track to improve measurement sensitivity, then measurement precision improves, but sensitivity to spacing variations and tilting increases
Solution Approach 1:
The sensing function is segmented across multiple coils positioned at different distances and lateral positions from the conductive track. The first and second sensor coils provide primary measurement with enhanced sensitivity, while the correction coil positioned at a different location detects spacing and tilting variations, allowing the system to maintain both sensitivity and reliability
4Measurement precision
If a correction coil is added to compensate for lateral offsets, then measurement precision improves, but device complexity increases
Solution Approach 1:
The correction coil is merged with the sensor coil assembly in a compact arrangement where all coils are positioned close to each other on the same side of the conductive track. The evaluation unit merges the correction signal with the measuring signals through signal processing, combining the compensation function with the measurement function in an integrated manner that minimizes additional 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
The solution provides a cost-effective, accurate, and compact linear-displacement sensor capable of handling installation tolerances, reducing measurement inaccuracies and enabling robust mounting technology, while maintaining high precision in detecting relative positions and offsets.
Implementation Method 1
an AC voltage is induced in the sensor coil when an AC voltage is applied to the excitation coil
Implementation Method 2
The sensor coil induces in the track an eddy current which results in a change in inductance of the sensor coil
Data Source
AI summary
A linear-displacement sensor includes a base element arranged with a sensor coil and an excitation coil in such a manner that an AC voltage is induced in the sensor coil upon application of an AC voltage to the excitation coil. An at least partly electrically conductive sliding element is configured to be shifted relative to the base element in a direction along the measurement path. The sliding element has a variable geometry along the measurement path to inductively couple partial turns of the sensor coil with the excitation coil. A correction coil is arranged above a geometry of the sliding element so that an inductive coupling of the correction coil and hence an amplitude of an AC voltage induced in the correction coil is dependent on a lateral offset of the sliding element in relation to the base element.