Multi-Coil Proximity Sensing for Distance and Bearing Detection
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Solution Overview
Problem
Conventional proximity sensors using alternating current magnetic fields can only detect the distance to a metal object and not its bearing, limiting their ability to provide positional information.
Innovation Solution
The use of multiple coils in a predetermined positional relationship, with a distance calculation unit and a position estimating unit to calculate and estimate the position of a detection object based on reception results from these coils, allowing for the detection of both distance and bearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single detection coil is used to detect metal objects, then the device complexity is reduced, but the measurement precision of position (including bearing) is insufficient
Solution Approach 1:
The detection system is segmented into multiple coils (detection coil and reference coil) with different functions. The detection coil detects the metal object while the reference coil compensates for external electromagnetic waves, allowing precise position measurement without excessive overall complexity
Solution Approach 2:
The system transitions from detecting only distance (one-dimensional) to detecting both distance and bearing (two-dimensional position information) by adding the reference coil and processing signals from multiple coils in different spatial orientations
2Measurement precision
If two detection coils are used for position detection, then the measurement precision of position is improved, but the device complexity increases
Solution Approach 1:
The detection coil serves multiple functions: it detects the metal object's position and also generates an eddy current that creates a reflection signal. This multi-functionality reduces the need for additional components, balancing measurement precision with device complexity
Solution Approach 2:
The reference coil acts as an intermediary that detects external electromagnetic waves and allows the system to compensate for them, enabling accurate position detection without requiring the detection coil to handle both object detection and noise rejection simultaneously
3Measurement precision
If detection coils are used to detect both distance and bearing, then the measurement precision is improved, but the difficulty of detecting and measuring increases
Solution Approach 1:
The system uses periodic excitation signals at different frequencies for different coils, which simplifies signal processing by allowing frequency-based separation of detection signals from reference signals, reducing the overall difficulty of measuring position parameters
Solution Approach 2:
The system measures more signal parameters than strictly necessary (including both in-phase and quadrature components), which provides redundant information that simplifies the calculation of distance and bearing through signal processing algorithms
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
Enables the detection of a metal object's position, including its bearing, improving the sensor's accuracy and convenience in mounting by distinguishing between objects on the central axis and those in the radial direction.
Implementation Method 1
a coil unit 10 having a circular coil 11 and a circular coil 12 which has a larger diameter disposed coaxially with the coil 11
Implementation Method 2
an eddy current is generated in a detection object made of a metal within a detection range due to a magnetic field generated by a current flowing through the detection coil
Data Source
AI summary
A proximity sensor is provided with coils (11, 12) disposed in a pre-set positional relationship, a first distance calculation unit (31) and a second distance calculation unit (32) for calculating first distance information (d1) and second distance information (d2), respectively, from the coils (11, 12) to a detection object (W) on the basis of reception results (voltages V1, V2) of the coils (11, 12), and a position estimating unit (33) for estimating the position, such as distance and azimuth, of the detection object (W) on the basis of the first distance information (d1), the second distance information (d2), and the positional relationship of the coils (11, 12).