Center-Tapped Inductive Position Sensing for Miniaturized EMC Stability
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Solution Overview
Problem
Conventional inductive position sensors face challenges in maintaining accurate signal strength and electromagnetic compatibility (EMC) immunity as they become smaller, making it difficult to achieve reliable noise resistance and miniaturization.
Innovation Solution
A center-tapped transmit coil system is used, inducing a single step of inductance imbalance to determine target position, utilizing a single transmit coil and three receive coils with a Clarke transformation to enhance signal amplitude and allow for miniaturized designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single TX coil and three RX coils system is used, then position sensing capability is achieved, but the received signal strength diminishes as the system size decreases
Solution Approach 1:
The transmit coil is center-tapped and divided into two parts (first part between first terminal and center-tap, second part between center-tap and second terminal). This segmentation allows the system to generate three distinct signals from a single coil, enabling position sensing while maintaining stronger signal strength through direct coupling to three receive inputs.
Solution Approach 2:
The patent combines the functions of multiple transmit coils into a single center-tapped transmit coil. By electrically connecting the first terminal, second terminal, and center-tap to three different receive inputs, the system achieves the functionality of multiple coils while using fewer physical components, thereby maintaining signal strength without requiring larger system size.
2Volume of moving object
If the coil system size is reduced for miniaturization, then device compactness is improved, but the received signal strength and noise resistance deteriorate
Solution Approach 1:
The center-tapped transmit coil is segmented into two functional parts that can be electrically connected to different receive inputs. This segmentation allows the system to maintain adequate signal strength for EMC immunity while using a smaller overall coil system, enabling miniaturization without sacrificing noise resistance.
Solution Approach 2:
The patent changes the electrical connection parameters by directly coupling the transmit coil terminals and center-tap to three different receive inputs through electrical couplings. This parameter change optimizes signal distribution and strength, allowing the system to achieve reliable EMC performance in a miniaturized configuration.
3Measurement precision
If conventional two-step induction mechanism is used, then position sensing is achieved, but the signal strength is insufficient for miniaturized designs
Solution Approach 1:
The patent extracts and eliminates the intermediate eddy current induction step from the conventional two-step mechanism. By directly coupling the transmit coil terminals and center-tap to receive inputs, the system obtains position-dependent signals without relying on the two-step induction process, thereby achieving stronger signal amplitudes suitable for miniaturized designs.
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 provides larger useful signal amplitudes, improves EMC performance, and enables miniaturization by reducing the number of coils and coupling steps, while maintaining accurate position sensing.
Implementation Method 1
an integrated circuit (IC) is used to excite a transmit (TX) coil, typically operating in the few MHz frequency range. This excitation induces eddy currents in the target. The eddy currents then induce currents in a set of three receive (RX) coils
Implementation Method 2
This excitation induces eddy currents in the target. The eddy currents then induce currents in a set of three receive (RX) coils
Data Source
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Figure 5~6
AI summary
A position sensor for determining the position of a target includes a center-tapped transmit coil with three terminals: a first terminal, a center-tap, and a second terminal. The sensor has a transmitter that applies an oscillating signal across the first and second terminals of the transmit coil. A receiver is connected to the first terminal, second terminal, and center-tap of the transmit coil. The processing circuit calculates the target's position by applying a transformation to the signals received from the three terminals.