Rail Track Resonance Detection for Reliable Vehicle Presence Sensing
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Solution Overview
Problem
Existing methods for detecting rail vehicles in track sections, particularly trams, suffer from inaccuracies and reliability issues due to interference from road vehicles and variations in vehicle wheelbase and body conductivity, which affect resonant frequency and damping.
Innovation Solution
A method involving a complex transfer function analysis of digitized transmit and receive signals using a digital Fourier transform to calculate transimpedance, with a digital measuring unit operating independently of the oscillator, to determine the presence of a vehicle by analyzing transimpedance magnitude and phase within predefined frequency and amplitude windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resonant circuit is excited with a transmit signal at adjustable frequency, then the detection sensitivity is improved by maintaining resonance, but the system complexity increases due to continuous frequency regulation requirements
Solution Approach 1:
The patent implements continuous frequency regulation by feeding back the evaluated resonant frequency to the transmit signal generator. The digital measuring unit continuously evaluates the resonant frequency from the receive signal and adjusts the transmit frequency accordingly, ensuring the system remains at resonance throughout the measurement period, thereby maintaining high detection sensitivity without requiring complex manual tuning
Solution Approach 2:
The system automatically maintains resonance through self-regulation. The frequency control unit uses the evaluated resonant frequency information to automatically adjust the transmit frequency without external intervention, making the system self-adjusting and reducing the need for complex external control mechanisms
2Reliability
If digital signal processing with Fourier transform is used to calculate transimpedance, then the reliability of vehicle detection is improved by reducing interference susceptibility, but the computational complexity and processing time increase
Solution Approach 1:
The patent replaces analog signal processing methods with digital signal processing. Instead of using analog filters and circuits to analyze the resonant circuit response, the system uses digital Fourier transform to calculate the complex transfer function and transimpedance, providing more reliable interference rejection through digital signal manipulation
Solution Approach 2:
The patent transforms the time-domain signals into frequency-domain spectra using Fourier transform. This parameter transformation allows the system to analyze frequency components and calculate transimpedance magnitude and phase, enabling more reliable detection by examining the frequency characteristics rather than raw time-domain signals
3Measurement precision
If the transmit frequency is regulated continuously to the resonant frequency, then the signal amplitude is maintained at high levels for better detection, but the energy consumption increases due to continuous frequency adjustment
Solution Approach 1:
The patent maintains continuous resonance by continuously regulating the transmit frequency to match the resonant frequency throughout the measurement period. This ensures the resonant circuit always operates at maximum amplitude, providing optimal detection conditions continuously rather than intermittently, thereby maintaining high signal quality throughout the measurement
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
Enhances detection accuracy and reliability by maintaining resonance throughout the measurement, providing a high-amplitude, easily analyzable signal and reducing interference susceptibility.
Implementation Method 1
the two short-circuiting connectors and the intervening rail sections then form an electrical circuit that exhibits a certain ohmic resistance as well as a certain capacitance and inductance, and therefore behaves like an electrical (parallel) resonant circuit
Data Source
Figure 1
Figure 2~4
Figure 5~7
AI summary
1. Method for detecting a rail vehicle in a track section (10) configured as an electrical resonant circuit (16), wherein the presence of a vehicle in the track section is detected by electronic evaluation of changes in the resonant frequency and the damping of the resonant circuit (16), characterized by the following steps: - Exciting the resonant circuit (16) with a transmit signal (I_s) having an adjustable transmit frequency f_s, - Receiving a receive signal (U_e) representative of an oscillation of the resonant circuit (16), - Controlling the transmit frequency f_s to the resonant frequency of the resonant circuit (16), and - Deciding whether a vehicle is in the track section based on a criterion that includes an evaluation of the transmit signal (I_s) and the receive signal (U_e) while continuously controlling the transmit frequency.