Wheel Sensor Phase Shifter for Eddy Current Interference
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Solution Overview
Problem
Inductively working wheel sensors in railway systems are sensitive to interference from eddy current brakes, leading to incorrect wheel detection due to similar magnetic field influences, and existing solutions for improving interference immunity are complex, unreliable, or impractical.
Innovation Solution
The method involves maximizing the level difference between useful and interference signals by exploiting the phase difference between transmission and reception signals, using an adjustable phase shifter to regulate the received signal, thereby reducing the impact of eddy current brake interference without requiring precise adjustments or additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the resonant frequency of the receiver resonant circuit is changed relative to the transmit frequency, then the interference of the eddy current brake is suppressed, but the device complexity increases and the solution becomes unreliable
Solution Approach 1:
The patent changes the phase angle parameter of the receiver signal relative to the transmitter signal. By adjusting the phase angle to specific values (e.g., 90 degrees), the receiver becomes insensitive to eddy current brake interference while remaining sensitive to wheel signals, thus suppressing interference without increasing device complexity
Solution Approach 2:
The patent applies preliminary phase shifting to the receiver signal before evaluation. The phase angle is adjusted in advance to optimize the signal-to-interference ratio, allowing the system to preemptively cancel out eddy current brake interference rather than dealing with it after detection
2Object-affected harmful factors
If the switching threshold is adjusted to exclude eddy current brake influence, then interference immunity improves, but the system becomes expensive and unreliable due to requiring accurate measurement and individual adjustment
Solution Approach 1:
Instead of adjusting the switching threshold, the patent changes the phase angle parameter of the receiver signal. This parameter change inherently filters out eddy current brake interference through phase orthogonality, eliminating the need for complex threshold calibration and individual adjustment for each sensor
Solution Approach 2:
The phase-shifted receiver signal automatically rejects eddy current brake interference without requiring external calibration or adjustment. The system self-regulates by exploiting the phase difference between wheel signals and eddy current interference, making the sensor inherently immune without additional complexity
3Object-affected harmful factors
If eddy current brakes are adjusted to limit their influence, then interference is reduced, but the solution is complex, unreliable, and impractical
Solution Approach 1:
The patent converts the harmful eddy current brake interference into a beneficial filtering mechanism by exploiting its phase characteristics. The receiver is phase-shifted to be orthogonal to the interference, effectively using the interference's own properties (phase consistency) against it, thereby eliminating the need to adjust the eddy current brakes themselves
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 interference immunity of wheel sensors, ensuring accurate wheel detection without complex adjustments or individual eddy current brake modifications, by optimizing the phase relationship between transmitted and received signals.
Implementation Method 1
a transmission signal is generated in at least one sensor channel which is inductively coupled to a reception signal
Implementation Method 2
The magnetic field influencing effect of the iron wheels of the rail vehicles is mainly used
Implementation Method 3
One source of this is the eddy current brakes that have been used for a number of years
Data Source
Figure 1~2
AI summary
The invention relates to a method for increasing the interference resistance of a wheel sensor, in particular for a track clear detection system, wherein a transmission signal (13) is produced in at least one sensor channel, said signal being inductively coupled (4) to a reception signal (5) that is fed to an evaluation device (10) for detection of a magnetic field change as a result of a railway vehicle having traveled over the track (3), and a corresponding wheel sensor. In order to counteract the interference effect using eddy current braking, it is provided that a level separation between a utility signal to be evaluated and an interference signal is maximized in relation to a phase difference (16) between the transmission signal (13) and the reception signal (5), said difference being specific to the interference signal.