Inductive Sensor Circuit for Rotation Detection
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Solution Overview
Problem
Existing position and rotation sensors for applications like crankshafts in internal combustion engines face high costs and are susceptible to electromagnetic interference, which affects their performance.
Innovation Solution
A proximity sensor system utilizing a combination of sensor elements with geometrically symmetrical shapes to minimize mutual inductance in the absence of a target object, reducing noise interference and improving sensitivity, while maintaining low costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall Effect sensor is used to sense position, then position detection capability is improved, but cost increases
Solution Approach 1:
The patent replaces expensive Hall Effect sensors with a cost-effective inductive sensing system using planar coils and simple electronic components that can be manufactured at lower cost while maintaining adequate functionality for position and rotation detection
2Measurement precision
If traditional sensor structures are used, then position sensing is achieved, but susceptibility to electromagnetic interference increases
Solution Approach 1:
The patent converts the harmful effect of electromagnetic interference into a beneficial feature by using differential inductive sensing where two coils are positioned to detect opposite magnetic field changes, causing common-mode electromagnetic noise to cancel out while preserving the differential signal containing the position information
Solution Approach 2:
The patent uses asymmetric coil positioning and configuration where the first and second coils are arranged to detect magnetic field changes in opposite directions, creating an inherently noise-rejection differential measurement system that is less susceptible to electromagnetic interference
3Measurement precision
If sensor elements are positioned close to the target object, then sensitivity is improved, but mutual inductance interference increases
Solution Approach 1:
The patent extracts and removes the mutual inductance interference by using differential measurement where the output is taken as the difference between two coil signals, effectively canceling out the common-mode mutual inductance effects while preserving the differential position-dependent signal
Solution Approach 2:
The patent employs asymmetric coil positioning and geometric configurations where the coils are arranged to have different orientations or positions relative to the target object, creating differential sensitivity patterns that enhance position detection while the differential arrangement naturally rejects mutual inductance interference
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 sensor system effectively detects the position and direction of rotation with improved noise cancellation and sensitivity, reducing costs and enhancing performance in noisy environments.
Implementation Method 1
an excitation element configured to receive an a.c. signal from a sensor circuit and form a magnetic field
Implementation Method 2
a first receiver sensor configured to have a first mutual inductance with the excitation element... a second receiver sensor configured to have a second mutual inductance with the excitation element
Data Source
AI summary
In one embodiment, a sensor circuit may include a first receiver circuit that may be configured to receive a first signal that is representative of a first mutual inductance and form a first detection signal that is representative of the first mutual inductance, wherein the first variable mutual inductance varies in response to a position of a metal object. An embodiment may include a second receiver circuit configured to receive a second signal that is representative of a second mutual inductance and form a second detection signal that is representative of the second mutual inductance, wherein the second mutual inductance varies in response to the position of the metal object. In an embodiment, the sensor circuit may include a recognition circuit configured to assert a movement detected signal responsively to a first value of the first detection signal, configured to assert a movement direction signal responsively to a first value of the second detection signal.