Train Presence Detection via Phase Shift and Amplitude Analysis
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Solution Overview
Problem
Existing railway track occupancy detection systems face challenges in accurately identifying the presence of trains due to signal disturbances, particularly in environments with phase shifts and amplitude variations close to the frequencies of the local and field voltages, leading to incorrect energization or de-energization of relays.
Innovation Solution
A computer-implemented method that acquires local and field voltages, calculates cross-correlation, and determines phase shifts to accurately differentiate between train occupancy and disturbances, using a normalized cross-correlation approach to isolate noise and determine the presence of trains reliably.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electromechanical or electronic relays are used to detect train presence by comparing local voltage and field voltage, then the system can identify occupancy under ideal conditions, but the relay may be incorrectly de-energized or re-energized due to signal disturbances with frequencies close to the local signal frequency, leading to false occupancy detection
Solution Approach 1:
The patent segments the detection process into multiple independent measurement components: phase shift measurement, amplitude measurement, and frequency measurement. Each component is processed separately through specific calculation formulas, allowing the system to evaluate multiple parameters independently and make a综合 determination about train presence, thereby reducing the impact of any single disturbed parameter
Solution Approach 2:
The patent introduces an intermediary processing system that receives both the local voltage signal and field voltage signal, performs cross-correlation analysis to determine phase shifts, and applies multiple measurement formulas before controlling the relay. This intermediary processing layer filters out direct disturbances by analyzing the relationship between signals rather than reacting to absolute voltage levels
2Productivity
If the relay responds to any voltage difference or phase shift, then the system can quickly detect train presence, but it cannot distinguish between actual train occupancy and signal disturbances, leading to incorrect relay operation
Solution Approach 1:
The patent changes from a simple voltage level comparison to a multi-parameter analysis approach, measuring phase shift, amplitude, and frequency simultaneously. By monitoring multiple parameters and requiring consistent changes across parameters to trigger relay operation, the system maintains fast response while improving detection precision and distinguishing actual occupancy from disturbances
Solution Approach 2:
The patent replaces the traditional electromechanical relay comparison mechanism with electronic signal processing that calculates cross-correlation, phase shifts, and amplitude ratios. This substitution allows for more sophisticated analysis of the voltage signals, enabling the system to distinguish between genuine occupancy signals and disturbances through mathematical relationships rather than simple threshold comparisons
Data Source
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AI summary
Method for detecting presence of a train on a track section inserted in a track circuit, comprising an initial step of acquiring (300) the local voltage Vin_L and the field voltage Vin_C, equal to the sum of a periodic signal VC(t) and a noise N(t), for an integration interval T, wherein the method: calculates (340, 345) the effective values of the local voltage Vin_L and field voltage Vin_C; determines (330) a phase shift ϕ of the field voltage Vin_C with respect to the local voltage Vin_L on the basis of a cross-correlation at the origin of the local voltage Vin_L and field voltage Vin_C and its derivative at the origin; compares (335) the phase shift ϕ with a predetermined maximum phase shift threshold R and, if it exceeds the predetermined maximum phase shift threshold R, signals (390) the presence of a train on said track section, otherwise it executes the following steps; calculates (370) an effective value VCeff of the periodic field signal VC(t) on the basis of a maximum value Cmax of the cross-correlation normalised to the product VLeff_mis ∗ VCeff_mis of the effective values, depending on the phase shift ϕ, and on the effective value VLeff_mis of the local voltage Vin_L; compares (380) the effective value VCeff of the periodic field signal VC (t) with the effective value VLeff_mis of the local voltage Vin_L acquired in the initial phase and, if they differ by more than a predetermined maximum effective value difference threshold S, signals (390) the presence of a train on said track section.