Planar Inductive Position Sensor With Reduced Blind Zone
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Solution Overview
Problem
Miniaturization of inductive sensor devices to achieve dimensions roughly corresponding to their measuring range is challenging due to variations in complex impedance and resonant frequency, as well as difficulties in reducing blind zones and providing adequate sensing range in compact spaces.
Innovation Solution
An inductive sensor device with a planar exciting coil and a parallel receiving coil, where the sensor electronics determine parameters of electrical signals and induced voltages to calculate the longitudinal position of an object, utilizing the inductive backward effect to compensate for distance dependence without additional receiving coils, allowing for a compact configuration with a measuring range of up to 10 mm and a housing size of 15 mm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the sensor device is miniaturized to reduce housing size, then the housing dimensions are reduced, but the complex impedance of the exciting coil varies significantly leading to resonant frequency shifts and reduced measurement reliability
Solution Approach 1:
The patent implements dynamic frequency adaptation by continuously adjusting the excitation frequency based on the measured complex impedance of the exciting coil. This allows the sensor to maintain optimal resonant operation despite miniaturization-induced impedance variations, thereby preserving measurement reliability in a compact housing
Solution Approach 2:
The patent changes the operating parameter (excitation frequency) dynamically to compensate for the effects of miniaturization. By adapting the excitation frequency to the actual resonant frequency determined from complex impedance measurements, the system maintains accurate position sensing despite reduced housing dimensions
2Measurement precision
If additional receiving coils are added to improve position determination accuracy, then the measurement precision is improved, but the device complexity and housing size increase
Solution Approach 1:
The patent makes the exciting coil multi-functional by using it both for excitation and for position sensing through complex impedance measurement. This eliminates the need for separate receiving coils while maintaining measurement precision, thereby reducing device complexity and housing size
Solution Approach 2:
The patent merges the excitation function and sensing function into a single coil system. The exciting coil serves dual purposes: generating the magnetic field for excitation and detecting position changes through its complex impedance variations, thus eliminating redundant components
3Length of stationary object
If the measuring range is extended to increase the sensing distance, then the useful measurement range is improved, but the housing dimensions and blind zones increase
Solution Approach 1:
The patent extends the measuring range by dynamically adjusting the excitation frequency to track resonant frequency shifts that occur with changing object distances. This allows accurate position determination over a longer range without proportionally increasing housing dimensions
Solution Approach 2:
The patent uses periodic excitation signals and measures the complex impedance at different frequencies to map the resonant characteristics. This periodic measurement approach enables extended measuring range by capturing frequency-dependent impedance variations that correlate with object position
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 device achieves precise position determination with a short response time and high output transfer rate, suitable for gripping systems and rotating objects, and can be integrated into existing equipment with minimal space requirements.
Implementation Method 1
a substantially planar exciting coil, by means of which an alternating magnetic field for inducing eddy currents and/or magnetic polarization can be generated in the object
Implementation Method 2
an alternating magnetic field for inducing eddy currents and/or magnetic polarization can be generated in the object
Implementation Method 3
an alternating magnetic field for inducing eddy currents and/or magnetic polarization can be generated in the object
Implementation Method 4
a first substantially planar receiving coil, which is arranged substantially parallel to and overlapping the exciting coil
Data Source
AI summary
An inductive sensor device has a coil arrangement and sensor electronics for determining a longitudinal position of an at least partially electrically conductive and/or magnetically polarizable object moveable at a distance from a device end face along a device sensitive axis. The arrangement has a substantially planar exciting coil for producing an alternating magnetic field for inducing eddy currents and/or magnetic polarization in the object and a first substantially planar receiving coil substantially parallel to and overlapping the exciting coil. The coils are substantially parallel to the end face. The sensor electronics determine at least one parameter of an exciting coil electrical signal, which is variable owing to an inductive backward effect of the object, at least one parameter of a voltage inducible in the at least first receiving coil based on this effect, and the longitudinal position from the determined signal parameter and the determined voltage parameter.