Instantaneous Speed Determination Using Doppler Shift
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Solution Overview
Problem
Conventional systems for determining the instantaneous speed of a train, such as those based on electro-mechanical devices, are extremely expensive and rely on costly components like axle rotation sensors and single-axis accelerometers, which are not cost-effective for safety-critical applications in the railway industry.
Innovation Solution
A system utilizing GNSS satellite signals to calculate instantaneous speed by measuring the Doppler effect-induced frequency shift, combining data from multiple satellites to ensure safety and accuracy without the need for expensive components like atomic clocks or mechanical parts, using antennas and electronic modules to receive signals and determine vector differences in speed between the train and satellites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electro-mechanical devices (axle rotation sensors, accelerometers, radars) are used to determine instantaneous speed, then reliability is improved, but cost increases significantly
Solution Approach 1:
The patent replaces mechanical speed determination devices (axle rotation sensors, accelerometers, radars) with an electronic system that uses GNSS satellite signals and Doppler effect calculations. This substitution eliminates mechanical components while achieving the same speed determination function, thereby reducing cost while maintaining reliability
Solution Approach 2:
The patent uses multiple independent GNSS signal measurement channels to obtain redundant speed determination results. By combining measurements from multiple satellites and multiple receiving antennas, the system creates redundant information paths that enhance reliability without requiring expensive mechanical backup systems
2Measurement precision
If multiple GNSS satellites and signal combinations are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the speed determination process into distinct functional modules: signal reception by multiple antennas, independent Doppler effect calculation for each satellite signal, and a combining module that integrates results from multiple measurement channels. This segmentation allows complex multi-satellite processing to be managed through systematic modular operations, reducing perceived complexity while maintaining high precision
3Reliability
If signals from multiple satellites are processed independently and combined, then reliability is improved, but calculation time increases
Solution Approach 1:
The patent performs preliminary processing of GNSS signals by continuously tracking and pre-calculating Doppler shifts from multiple satellites before speed determination is critically needed. The system maintains ready-computed signal characteristics and prepares measurement data in advance, allowing rapid final speed calculation when required without sacrificing the reliability benefits of multi-satellite processing
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 provides a cost-effective method for determining instantaneous speed with high safety and accuracy, reducing the probability of error to levels comparable to or better than existing systems, without the need for expensive hardware, thus offering a more economical solution for safety-critical applications.
Implementation Method 1
measurement of the offset of the frequency of the received signal with respect to the predetermined frequency of the transmitted signal, determination of the vector difference of the speeds of the object and of the satellite according to the satellite-object direction by calculation of the Doppler effect having generated the frequency offset
Data Source
Figure 1~2
Figure 3~4
AI summary
The system has a signal analyzing and calculating unit (8) with a frequency offset measuring unit (10) to measure the frequency offset of a received signal. A speed difference determining unit determines the vectorial difference of the speeds of an object and a satellite by calculating Doppler effect that generates the frequency offset. An instantaneous speed calculating unit calculates the instantaneous speed from the vectorial difference. The frequency offset measurements and the instantaneous speed calculations are repeated independently on signals issued from different satellites. An independent claim is also included for a method of determining the instantaneous speed of an object moving on a known path.