Inductive Position Signal Processing With Synchronized Integration
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Solution Overview
Problem
Conventional inductive position sensors face challenges in efficiently and precisely evaluating the position of moving targets due to noise and signal distortion, particularly in magnetic field interference scenarios, which affect the accuracy of position feedback in applications like throttle control for motorbikes.
Innovation Solution
A signal processing unit for inductive position sensors that utilizes a frequency-synchronized integration scheme to calculate the position of a moving target from sine and cosine phase-shifted position signals, incorporating an integrator that acts as an analogue finite impulse response filter, and includes an oscillator for generating AC excitation signals, an analog-to-digital converter, and a digital signal processor for precise amplitude evaluation and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RC low-pass filters are used for signal evaluation, then circuit implementation is simple, but measurement precision and noise reduction are insufficient
Solution Approach 1:
The patent replaces conventional RC analog filtering with a digital signal processing approach. The receiver coil signals are amplified and rectified, then processed through a digital low-pass filter implemented via microcontroller or DSP. This substitution of analog filtering with digital processing achieves superior noise reduction and measurement precision while maintaining reasonable circuit complexity through integrated digital signal processing algorithms.
2Measurement precision
If signal processing complexity is increased to reduce noise, then measurement precision improves, but processing time and computational load increase
Solution Approach 1:
The patent employs periodic sampling of the receiver coil signals synchronized with the transmitter coil excitation frequency. By sampling at optimal intervals and using periodic correlation techniques, the system achieves high measurement precision without requiring continuous complex processing. The digital low-pass filter uses a finite impulse response (FIR) algorithm with predetermined tap coefficients that can be efficiently computed in discrete time steps, reducing processing time while maintaining accuracy.
3Reliability
If magnetic field shielding is added to protect against interference, then reliability against magnetic disturbance improves, but device complexity and size increase
Solution Approach 1:
The patent converts the potential harmful effect of magnetic field interference into a beneficial filtering mechanism. By using digital signal processing with band-pass and low-pass filtering algorithms, the system selectively passes only the frequency components corresponding to the intended inductive coupling signals while rejecting magnetic field interference at different frequencies. This approach achieves high reliability against magnetic disturbance without adding physical shielding components, maintaining device simplicity.
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
This approach enhances the precision and robustness of position detection by reducing noise and signal ripples, providing a more accurate and reliable position feedback even in noisy environments, while maintaining a comparable circuit implementation effort and size to traditional RC low-pass filters.
Implementation Method 1
an oscillator that generates a radio-frequency signal, which is applied to the transmitter coil to create a static high frequency magnetic field. This static high frequency magnetic field is picked up by the receiver coils
Implementation Method 2
Inductive position sensors implement a magnet-free technology, utilizing the physical principles of eddy currents or inductive coupling to detect the position of a target that is moving above a set of coils
Data Source
AI summary
A signal processing unit for an inductive position sensor is provided. The inductive position sensor provides a first position signal and a second phase-shifted position signal, such as, a sine position signal and a cosine position signal. The signal processing unit has an integrator for integrating an integer number of periods of the first position signal respectively an integer number of periods of the second phase-shifted position signal. The position of the moving target of the position sensor is calculated from the integrated first position signal and the integrated second phase-shifted position signal.