Train Speed Control Device Using AC Voltage Frequency for Low-Speed Accuracy
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Solution Overview
Problem
Conventional speed control devices using tacho-generators face challenges in accurately calculating train speed in low speed regions due to voltage drop, leading to decreased calculation accuracy and increased costs with the use of pulse generation circuits.
Innovation Solution
A speed control device that employs a calculating unit to determine train speed using notch information, route database, and car characteristic data when pulse count signals from a tacho-generator are undetectable, and calculates speed using pulse count signals when they are detectable, thereby maintaining accuracy without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pulse generation circuit is used to generate pulse signals in low speed region, then measurement precision of train speed is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the measurement parameters by using frequency information of the AC voltage signal from the tacho-generator instead of relying on pulse generation. By calculating train speed based on the frequency characteristics of the AC voltage signal, the system achieves accurate low-speed measurement without requiring additional pulse generation circuits, thus maintaining measurement precision while avoiding increased device complexity
Solution Approach 2:
The patent replaces the mechanical/electrical pulse generation approach with a computational method that processes the AC voltage signal characteristics. Instead of using hardware circuits to generate pulses, the system uses a calculation unit to derive speed information from the frequency parameters of the existing AC signal, substituting a computational solution for a hardware-based solution
2Measurement precision
If a pulse generation circuit is used to generate pulse signals in low speed region, then measurement precision of train speed is improved, but reliability deteriorates
Solution Approach 1:
The patent makes the existing AC voltage signal from the tacho-generator serve dual purposes: both for indicating wheel rotation and for providing frequency information for speed calculation. The system uses the signal already present in the system rather than requiring separate dedicated circuits, achieving self-sufficiency and improving reliability by reducing the number of additional components that could fail
3Measurement precision
If pulse count signal is used for speed calculation, then measurement precision is improved, but it becomes inapplicable in low speed region where voltage drops
Solution Approach 1:
The patent changes from using pulse count (amplitude-based detection) to using frequency information of the AC voltage signal. This parameter change allows the system to operate effectively across the entire speed range including low speeds, because frequency detection does not suffer from the same voltage threshold limitations as pulse generation and counting methods
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
Enables accurate train speed calculation in low speed regions using a tacho-generator, preventing cost increases and reliability deterioration, and ensuring safe and efficient train operation.
Implementation Method 1
a tacho-generator (1) that generates an AC voltage signal (1a) corresponding to a number of revolutions of the wheel (10)
Data Source
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AI summary
A speed control device 8 that controls a speed of a train 100 using a tacho-generator 1 includes a calculating unit that calculates, when a pulse count signal 3a obtained by conversion from an AC voltage signal 1a that is outputted from the tacho-generator 1 and corresponds to a rotating speed of a wheel 10 of the train 100 cannot be detected, a first speed using notch information 4a, route data 5a, and car characteristic data 6a and calculates, when the pulse count signal 3a can be detected, a second speed using the pulse count signal 3a. The speed control device 8 includes a position calculating unit that calculates a position of the train 100 using the speed calculated by the calculating unit.