Sensor Device with Compensation Coils for Magnetic Interference Rejection
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Solution Overview
Problem
Magnetic interference fields from electrical rail currents in railway technology pose a significant challenge for sensor devices, making them insensitive to magnetic interference fields while ensuring reliable object recognition.
Innovation Solution
A sensor device comprising a receiving coil, transverse current-powered intermediate power supply, and two compensation coils, where the compensation coils are arranged and connected in series to neutralize the magnetic disturbing field, with the receiving coil and compensation coils forming a series connection that cancels out induced voltages from the magnetic interference, allowing for reliable object recognition signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a receiving coil is used to detect magnetic field changes for object recognition, then object detection capability is improved, but sensitivity to magnetic interference fields from rail currents worsens
Solution Approach 1:
The patent introduces compensation coils as intermediary elements that generate counteracting magnetic fields to neutralize the harmful magnetic interference from rail currents. These compensation coils act as mediators between the receiving coil and the interference source, allowing the receiving coil to detect object-induced magnetic field changes while the compensation coils cancel out the rail current interference, thereby resolving the contradiction between detection capability and interference sensitivity
Solution Approach 2:
The patent applies preliminary anti-action by using the transmitting coil to generate a magnetic field that induces voltages in the compensation coils before the interference measurement occurs. The compensation coils are pre-configured with opposite polarity connections so that they generate counteracting voltages that cancel out the magnetic interference from rail currents during the detection process, enabling accurate object recognition despite the presence of strong magnetic interference
2Reliability
If compensation coils are added to suppress magnetic interference, then interference rejection is improved, but device complexity worsens
Solution Approach 1:
The patent merges the functions of multiple coils into a unified evaluation system. The transmitting coil, receiving coil, and two compensation coils are electrically connected in series to form a single evaluation circuit. This merging allows the system to achieve interference rejection through the combined voltage contributions of all coils while maintaining relatively simple device architecture, as the series connection naturally sums the voltages without requiring complex signal processing electronics
Solution Approach 2:
The patent utilizes parameter changes in the electrical connections of the coils to achieve interference suppression. By configuring the compensation coils with opposite polarity connections in the series circuit, the system changes the electrical parameters (voltage signs) of the coil connections to enable cancellation of interference voltages. This parameter-based approach allows complex interference rejection functionality to be achieved through simple electrical connection configurations rather than complex structural arrangements
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 solution effectively suppresses magnetic interference fields, enabling reliable detection of objects approaching or passing by, even in the presence of significant magnetic interference, by ensuring that the total induced voltage in the series connection of the receiving and compensation coils is approximately zero, thus minimizing detection errors.
Implementation Method 1
the two compensation coils (11, 12) generate the same, equally large voltages with opposite signs (corresponds to a phase offset of 180°) as the receiving coil (10)
Implementation Method 2
a magnetic disturbing field (M) acting on the receiving coil (10) and the two compensation coils (11, 12) induces in total in the two compensation coils a voltage with another sign
Data Source
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AI summary
The invention relates to a sensor device (1) for sensing a change in a magnetic field, which change is caused by an object approaching the sensor device (1) in a longitudinal direction (L) or moving past the sensor device (1) in the longitudinal direction (L). According to the invention, the sensor device (1) comprises at least one receiving coil (10), an AC-fed transmitting coil (30) arranged upstream or downstream of the receiving coil (10) based on the longitudinal direction (L) and two compensation coils (11, 12), one of which is arranged upstream of the transmitting coil (30) and the other of which is arranged downstream of the transmitting coil (30) based on the longitudinal direction (L), the two compensation coils (11, 12) are each permeated by the magnetic field generated by the transmitting coil (30) and are electrically connected in series in such a manner that the voltages induced in the two compensation coils (11, 12) by the magnetic field of the transmitting coil (30) have different signs, and the receiving coil (10) and the two compensation coils (11, 12) are electrically connected in series, wherein the electrical polarity of the coils is selected in such a manner that a magnetic interference field (M) acting on the receiving coil (10) and the two compensation coils (11, 12) induces a voltage in the receiving coil (10) with a sign which differs from that in the two compensation coils (11, 12).