Inductive Sensor Phase Modulation for Robust Position Measurement
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Solution Overview
Problem
Inductive sensor devices face challenges in accurately determining position due to amplitude modulation sensitivity to relative orientation, excitation current fluctuations, and temperature variations, leading to measurement uncertainty and limited modulation depth.
Innovation Solution
The sensor device employs conductor strip loops with varying impedances and apparent resistances within modulation sections, using phase modulation to enhance position determination robustness against assembly errors and environmental influences, without requiring application-specific integrated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If amplitude modulation is used for position determination, then the measurement range can be extended, but the measurement precision deteriorates due to sensitivity to relative orientation, excitation current fluctuations, and temperature variations
Solution Approach 1:
The patent changes the modulation parameter from amplitude to phase. The scale elements are designed with different lengths to produce phase-modulated signals instead of amplitude-modulated signals. This phase modulation is inherently more robust against variations in relative orientation, excitation current fluctuations, and temperature changes, thereby maintaining measurement precision while preserving the extended measurement range.
Solution Approach 2:
The patent substitutes the amplitude-based detection mechanism with a phase-based detection mechanism. By using phase information instead of amplitude information for position determination, the system replaces a sensitive mechanical/electrical measurement approach with a more stable electromagnetic phase measurement approach that is less susceptible to environmental disturbances.
2Manufacturing precision
If the conductor strip loops have uniform impedance, then the manufacturing precision is improved, but the measurement precision deteriorates due to limited modulation depth
Solution Approach 1:
The patent applies local quality by making the conductor strip loops non-uniform in specific regions. The scale elements have varying lengths, creating local impedance variations along the scale body. These localized impedance differences produce sufficient phase modulation depth for accurate position determination while allowing uniform manufacturing processes to be used, thus maintaining manufacturing precision.
3Measurement precision
If phase modulation is used instead of amplitude modulation, then the measurement precision is improved by reducing sensitivity to environmental factors, but the device complexity increases
Solution Approach 1:
The patent replaces complex amplitude modulation/demodulation circuitry with simpler phase-based detection. The evaluation unit uses standard microcontroller phase measurement capabilities rather than requiring specialized amplitude modulation circuits. This substitution reduces device complexity while maintaining improved measurement precision through phase modulation.
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, robust, and accurate measurement range for absolute position determination, insensitive to assembly tolerances and environmental factors, using standard components and microcontrollers.
Implementation Method 1
a transmitter signal S is applied to a transmitter coil (25) of the sensor unit (13), thereby producing an oscillating magnetic field
Implementation Method 2
Each receiver coil (26, 27) provides a receiver signal E resulting from inductive coupling with at least one conductor strip loop (17)
Data Source
AI summary
An inductive sensor device has a scale body having a multiplicity of conductor strip loops arranged in a measurement direction in at least one scale line. A sensor unit is moveable along the scale body and has one coil group for each scale line, the coil group comprising a transmitter coil for producing a transmitter signal and at least one receiver coil. Each coil group provides at least one receiver signal for an evaluation unit for determination of an absolute relative position of the sensor unit relative to the scale body. At least one of the scale lines has at least one modulating section, within which the impedances and/or the apparent resistances of conductor strip loops change from one end of the modulating section to the other, whereby the at least one receiver signal is modulated with regard to its phase position relative to the transmitter signal.