Electromagnetic Distance Sensing With Offset-Frequency Coil Filtering
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Solution Overview
Problem
Mutual inductance between multiple electromagnetic sensor coils in close proximity causes interference, impairing the performance of distance sensing in multi-sensor systems.
Innovation Solution
Employing a first and second electromagnetic sensor coil driven at offset frequencies, with a low-pass filter having a cut-off frequency below the offset amount to attenuate interference components, and using multiple sensors for redundancy and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple electromagnetic sensor coils are placed in close proximity to form a multi-sensor system, then the system can gather more information about target location and increase reliability, but mutual inductance between the coils causes interference that impairs distance sensing performance
Solution Approach 1:
The patent applies periodic action by driving each sensor coil at a different predetermined frequency. The first sensor coil is driven at frequency f1 and the second sensor coil at frequency f2, creating periodic excitation signals that allow the system to distinguish between sensors. This frequency differentiation enables the sensing system to identify and filter out mutual inductance interference while maintaining multiple sensors in close proximity for improved reliability and target localization.
2Reliability
If multiple electromagnetic sensor coils are placed in close proximity, then the system can provide redundancy and improved reliability, but the mutual inductance causes periodic interference that reduces measurement precision
Solution Approach 1:
The patent uses periodic action with frequency differentiation to resolve the contradiction between reliability and measurement precision. Each sensor operates at a distinct frequency, allowing the system to maintain multiple sensors for redundancy while precisely identifying and eliminating mutual inductance interference through frequency-based filtering, thus preserving measurement accuracy.
Solution Approach 2:
The patent introduces an intermediary approach by using frequency as a distinguishing characteristic between sensors. The different operating frequencies act as intermediaries that allow the system to separate the signals from multiple sensors, enabling the sensing circuitry to distinguish between the primary sensing signal and mutual inductance interference, thereby maintaining measurement precision.
3Measurement precision
If sensor coils are driven at offset frequencies to mitigate mutual inductance interference, then distance sensing accuracy is improved, but the system complexity increases due to the need for frequency offset management and filtering
Solution Approach 1:
The patent applies parameter changes by modifying the operating frequency parameter of each sensor coil. By assigning different predetermined frequencies to each sensor, the system transforms the single-frequency operation into a multi-frequency operation, which enables frequency-based interference rejection. This parameter change approach systematically manages the complexity through defined frequency relationships and corresponding filtering strategies.
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
Stabilizes and enhances the accuracy of distance sensing by mitigating interference, allowing for more responsive and reliable distance measurements.
Implementation Method 1
a first electromagnetic sensor coil; first drive circuitry for driving the first electromagnetic sensor coil with a first alternating current
Implementation Method 2
electromagnetic distance-sensing system; eddy-current sensors
Implementation Method 3
mutual inductance between the first and second electromagnetic sensor coils can cause interference
Implementation Method 4
filtering circuitry configured to apply a low-pass filter to the first signal, wherein the low-pass filter has a cut-off frequency that is below the offset amount such that a component of the first signal caused by mutual inductance
Data Source
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AI summary
An electromagnetic sensor system and a method for sensing distance to a conductive target (1230) are disclosed. The sensor system has filtering circuity (1252), a first sensor (1120) having a first electromagnetic sensor coil (1210) driven with a first alternating current at a first predetermined frequency, and a second sensor (1122) having a second electromagnetic sensor coil driven with a second alternating current at a second predetermined frequency. The second predetermined frequency is offset from the first predetermined frequency by an offset amount. The first sensor (1120) outputs a first signal having a component that is that is indicative of a distance from the first electromagnetic sensor coil (1210) to the conductive target (1230), and the filtering circuitry (1252) applies a low-pass filter to the first signal. The low-pass filter (1252) has a cut-off frequency that is below the offset amount such that a component of the first signal caused by mutual inductance between the first and second electromagnetic sensor coils is attenuated. The filtering circuitry outputs a first filtered signal indicative of the distance from the first electromagnetic sensor coil (1210) to the conductive target (1230).