Wireless Magnetic Sensor Parking Detection with Self-Calibrating SOM
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Solution Overview
Problem
Existing vehicle detection systems in parking arrangements face challenges with inaccurate calibration of magnetic field sensors due to erratic changes in the earth's magnetic field caused by vehicles, which are influenced by the type and position of vehicles, and ambient factors, leading to unreliable detection of vehicle presence or absence.
Innovation Solution
The use of a self-organizing map (SOM) method to continuously determine and cluster the quiescent value of the magnetic field at each parking space, allowing for accurate detection of small deviations and distinguishing between occupied and vacant states by forming clusters of measuring values, with magnetic sensors measuring the earth's magnetic field in three dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic field sensors are used to detect vehicles by measuring disturbances in the earth's magnetic field, then vehicle detection capability is provided, but measurement precision deteriorates due to erratic changes in magnetic field caused by vehicle type, position, and ambient factors
Solution Approach 1:
The system performs preliminary calibration by determining the quiescent value of the magnetic field at each parking space before vehicle detection begins. This baseline establishment allows subsequent measurements to be referenced against a known state, compensating for ambient variations and enabling more precise detection of vehicle-induced disturbances.
Solution Approach 2:
The system continuously monitors and compares current magnetic field measurements against the calibrated quiescent value, using feedback to identify deviations that indicate vehicle presence. This closed-loop approach allows the system to adapt to changing ambient conditions and maintain measurement precision over time.
2Measurement precision
If calibration is performed manually by adding and displacing cars in a controlled manner, then measurement precision can be improved, but loss of time increases due to laborious calibration procedures that must be repeated after installations modifications
Solution Approach 1:
The system performs self-calibration by automatically determining the quiescent magnetic field value at each parking space during operational periods when no vehicles are present. This eliminates the need for manual calibration procedures, allowing the system to calibrate itself without human intervention and without requiring controlled vehicle movements.
Solution Approach 2:
The calibration process continues throughout the operational life of the parking system, with the quiescent value being determined periodically to account for changes in ambient conditions and installation modifications. This continuous calibration ensures measurement precision is maintained without requiring periodic manual recalibration.
3Measurement precision
If the surface area of induction loops is increased to improve detection accuracy, then measurement precision improves, but device complexity increases due to more extensive cable work and installation labor
Solution Approach 1:
The patent replaces the mechanical induction loop system with wireless magnetic field sensors that measure disturbances in the earth's magnetic field. This substitution eliminates the need for extensive cable work and complex installation procedures while maintaining or improving detection accuracy through the use of sensitive magnetic sensors positioned at each parking space.
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 reliable and energy-efficient vehicle detection system that accurately determines the presence or absence of vehicles, reducing the need for laborious calibration and minimizing interference from neighboring vehicles or fouling, and can be combined with other sensors for enhanced accuracy.
Implementation Method 1
The sensors measure the strength of the earth's magnetic field in one or more dimensions
Implementation Method 2
use of magnetic field sensors to detect moving or stationary vehicles, as trains or cars
Implementation Method 3
a self-organizing map (SOM) method to continuously determine and cluster the quiescent value of the magnetic field at each parking space
Data Source
Figure 1~4
Figure 2~3
AI summary
A parking arrangement with parking places for vehicles and with an automatic vehicle detection system which comprises a central computer system and a wirelessly operating parking sensor module for determining the presence or absence of a vehicle in the parking place, which parking sensor module comprises at least one vehicle sensor, which provides measuring values which are representative of the presence or absence of a vehicle, provided with calibration means for determining the quiescent value, representing the absence of a vehicle, of the measuring values from the vehicle sensor, which calibration means by a self-organizing map method divide the measuring values into clusters of mutually close values, wherein the cluster having the largest number of measuring values is selected as representative of the quiescent value of the measuring values at a parking place, wherein each time an adjusted quiescent value is determined, and wherein a measuring value which differs from the quiescent value by more than a predetermined threshold value indicates that a vehicle is situated in the parking place.