DC Track Circuit Occupation Detection Using Digital Code Modulation
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Solution Overview
Problem
Existing methods for detecting the occupation state of a direct current track circuit in railway lines are unreliable in noisy environments, particularly due to interference from traction noise and non-zero current readings when no train is present, leading to potential misinterpretation of signal information.
Innovation Solution
Modulating the low alternating voltage signal with an unambiguous digital code word in direct current track circuits, allowing for orthogonal coding that enables clear identification of the signal presence or absence of a train by maximizing signal power when correlated with the specific code word.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an unambiguous digital code word is added to the voltage signal to improve detection reliability, then the ability to identify signal presence/absence improves, but the system complexity increases due to encoding and correlation processing requirements
Solution Approach 1:
The patent applies preliminary action by pre-associating unambiguous digital code words with each track circuit before signal transmission. The encoding process prepares the signal in advance with unique identifiers, and the correlation processor is pre-configured with these code words to enable rapid and reliable detection when signals are received, thus improving reliability while managing complexity through advance preparation.
2Device complexity
If traditional voltage detection is used in noisy environments, then the measurement method is simple, but the detection precision deteriorates due to traction noise and dispersion resistance
Solution Approach 1:
The patent converts the harmful effect of noise into a beneficial filtering process. By using correlation processing with pre-associated digital code words, the system transforms noisy voltage signals into reliable detection results. The correlation processor effectively separates the desired signal from traction noise and dispersion resistance interference, turning the challenging noisy environment into an opportunity for robust signal identification through pattern recognition.
3Reliability
If dispersion resistance between insulating joints and tracks is present, then the current supplied is non-zero when no train is present, but this creates measurement errors that reduce detection accuracy
Solution Approach 1:
The patent introduces an intermediary digital code word as a mediator between the voltage signal and the detection process. Instead of directly interpreting the noisy voltage level (which is affected by dispersion resistance), the system uses the pre-associated digital code word as an intermediary reference. The correlation processor compares the received signal against this intermediary code, enabling accurate identification of signal presence/absence regardless of the non-zero current caused by dispersion resistance.
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 ensures accurate detection of the occupation state by minimizing noise interference and distinguishing between signal presence and absence with high reliability, even in noisy conditions.
Implementation Method 1
a voltage detector is applied parallel at the end opposite to such power supply point
Implementation Method 2
the low alternating voltage signal is modulated in amplitude and/or in phase with an unambiguous digital code word
Data Source
Figure 1
AI summary
Apparatus for verifying the presence of a train on a direct current track circuit in a railway line provided with a plurality of direct current track circuits adjacent to each other, such circuit comprising a pair of tracks (R) made up of parallel metal sections (B) between which an electric voltage may be applied, each direct current track circuit is separated from the adjacent one by means of electrically insulating joints (G).