Underbody Railway Speed Detection With Chirp Doppler Processing
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Solution Overview
Problem
Conventional railway vehicle speed detection methods using millimeter waves face challenges such as the need for large-sized antennas, requiring multiple detection devices, and optimizing reflection control members based on vehicle shape, while also suffering from accuracy degradation due to vehicle vibrations and multiple reflections.
Innovation Solution
A railway vehicle speed detection device using a chirp signal transmission and reception system with digital processing to calculate Doppler velocity and vehicle speed, employing a wide-angle antenna placement directly above the rail to avoid vibration effects and multiple reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens antenna is used to generate a narrow-angle beam for accurate speed detection, then measurement precision is improved, but the antenna size increases
Solution Approach 1:
The patent changes the signal transmission method from continuous wave to chirp signal, and processes the received signal using Fourier transform to extract Doppler frequency. This parameter change in signal processing allows the use of a wide-angle antenna instead of a narrow-angle lens antenna, achieving accurate speed detection without requiring a large antenna size.
2Measurement precision
If two speed detection devices are used to compensate for vibration-induced angle errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and processes the Doppler frequency component from the received signal using Fourier transform. By focusing on the Doppler frequency extraction from a single device's signal, the system achieves vibration compensation without requiring multiple detection devices, thereby reducing device complexity while maintaining measurement precision.
3Measurement precision
If millimeter wave speed detection is used to avoid wheel spin effects, then measurement precision is improved, but the system becomes sensitive to vehicle vibrations and multiple reflections
Solution Approach 1:
The patent uses Fourier transform to analyze the received signal and extract the Doppler frequency component. This feedback processing method allows the system to identify and measure the actual Doppler shift caused by vehicle motion while filtering out interference from vibrations and multiple reflections, thereby maintaining measurement precision in complex environments.
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 allows for a downsized antenna and accurate speed detection by minimizing the impact of vehicle vibrations and multiple reflections, ensuring precise speed measurement.
Implementation Method 1
a transmission portion to transmit a chirp signal whose frequency changes over time
Implementation Method 2
a digital processing portion to perform a Fourier transform on the reception signal received by the reception portion and calculate a distance to the target and the Doppler velocity of the target
Data Source
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AI summary
It is necessary to downsize an antenna required for railway vehicle speed detection using millimeter waves and avoid degraded speed detection accuracy due to vehicle vibrations and multiple reflections occurring at the bottom of the vehicle. For this purpose, a railway vehicle speed detection device includes a transmission portion to transmit a chirp signal whose frequency changes over time; a reception portion to receive the chirp signal, as a reception signal, reflected from a target; and a digital processing portion to perform a Fourier transform on the reception signal received by the reception portion and calculate a distance to the target and the Doppler velocity of the target. The transmission portion and the reception portion are placed at the bottom of the railway vehicle and are located directly above a rail. The digital processing portion not only equates a Doppler velocity for the rail as a target with the highest Doppler velocity, which is included in Doppler velocities for the targets positioned at equal distances calculated to the targets and corresponds to the reception signal indicating the peak intensity out of reception signals from the targets but also calculates a vehicle speed of the railway vehicle from the Doppler velocity for the rail.