Guided Vehicle Speed Measurement Using Eddy Current Feedback
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Solution Overview
Problem
Existing methods for determining the speed and position of guided vehicles, such as those using balises, global navigation satellites, tachometers, and Doppler radar, fail to accurately detect wheel slip/slide events and near-zero speeds, which are critical for safety, and are often complex.
Innovation Solution
A system and method employing a magnetic field device installed on-board the guided vehicle that induces Eddy currents in a conductive rail, using a feedback loop to control the magnetic field's displacement and minimize the reciprocal magnetic field measured, allowing precise speed determination by isolating the speed variable from other influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional techniques (balises, global navigation satellites, track circuits, tachometers, Doppler radar) are used to determine speed and position, then the system can provide speed and position information, but the system becomes complex and fails to detect wheel slip/slide events and near zero speed accurately
Solution Approach 1:
The patent replaces complex mechanical and electronic systems (tachometers, Doppler radar, track circuits) with a magnetic field-based sensing system. The device produces a magnetic field that interacts with the conductive rail to generate eddy currents, providing a simpler and more reliable method for speed and position detection that works accurately even during wheel slip/slide and near zero speed conditions
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the sensing device and the conductive rail. This magnetic field serves as a mediator that transfers information about vehicle speed and position to the sensor without requiring direct mechanical contact or complex electronic systems, enabling accurate detection of wheel slip/slide events and near zero speed
2Measurement precision
If a stationary magnetic field is used with two magnetic flux sensors to measure speed, then the speed can be determined from flux difference, but the method cannot accurately detect near zero speed and wheel slip/slide events
Solution Approach 1:
The patent transforms the stationary magnetic field approach into a dynamic system where the magnetic field is moved at a controlled speed. This dynamic approach allows the system to maintain accurate measurement capability across the full speed range including near zero speed, and to detect wheel slip/slide events by comparing the commanded field movement speed with the actual speed derived from the flux difference signal
Solution Approach 2:
The patent implements a feedback mechanism where the magnetic field movement speed is controlled based on measured flux differences. The system continuously adjusts the field movement to optimize the flux difference signal, enabling accurate speed measurement and detection of abnormal conditions such as wheel slip/slide and near zero speed events
3Loss of information
If complex systems are used to determine speed and position, then more comprehensive data can be obtained, but the system becomes difficult to operate and maintain
Solution Approach 1:
The patent extracts only the essential information needed for speed and position determination from the complex interaction between the magnetic field and conductive rail. By focusing on the flux difference signal and its relationship to speed, the system obtains comprehensive speed and position information while avoiding the operational complexity of processing multiple redundant signals from traditional systems
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
The solution provides a simple, precise method for determining the speed and position of guided vehicles, effectively addressing slip/slide and near-zero speed issues, and is insensitive to external factors like climatic conditions.
Implementation Method 1
A device for producing a magnetic field B capable of inducing Eddy current in the conductive rail when the system is installed on-board the guided vehicle
Implementation Method 2
producing a magnetic field B capable of inducing Eddy currents in the conductive rail; measuring a reciprocal magnetic field resulting from the Eddy currents
Data Source
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AI summary
System and method for measuring the speed of a guided vehicle. The present invention concerns a system (1) and a method for determining the speed of a guided vehicle (2) guided along a route by at least one conductive rail (3) extending according to its length along a direction R, the system (1) comprising: - a device (4) for producing a magnetic field B capable of inducing Eddy currents in the conductive rail (3), said device (4) being capable of displacing the magnetic field B at a time T_i according to a speed vector V that is parallel to the direction R of extension of the conductive rail (3) ; - a magnetic flux sensor configured for measuring a reciprocal magnetic field resulting from the Eddy currents created in the conductive rail by the magnetic field B; - a controller connected to the device (4) and to the magnetic flux sensor in order to control the magnitude of the speed vector V and its direction at said time T i in function of a value of the reciprocal magnetic field measured by said magnetic flux sensor so that at said time T_i, the reciprocal magnetic field measured by the magnetic flux sensor is minimized, leading to S = |V|