Wheel Magnet Hall Sensor Layout for Tamper-Resistant Speed Sensing
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Solution Overview
Problem
Existing velocity measurement systems for bicycles are vulnerable to manipulation, particularly in the context of electric bicycles, allowing users to bypass legal speed limits by falsifying or suppressing magnetic field signals.
Innovation Solution
Employing multiple Hall sensors arranged close together to quantitatively measure magnetic field strength changes at a high sampling frequency, enabling detection and prevention of manipulation by comparing data from different sensors and analyzing the magnetic field profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Reed contact is used for velocity measurement, then the device complexity is low and ease of manufacture is high, but the reliability is poor due to manipulation vulnerability
Solution Approach 1:
The patent divides the single sensor function into multiple Hall sensors arranged in a specific geometric pattern. Instead of using one Reed contact, multiple Hall sensors are segmented to detect magnetic field changes from different directions, making manipulation detection possible through comparative analysis of their outputs.
Solution Approach 2:
The patent replaces the mechanical Reed contact system with an electromagnetic field-based Hall sensor system. This substitution enables quantitative measurement of magnetic field strength and allows for manipulation detection through analysis of magnetic field profiles, significantly improving reliability.
2Reliability
If multiple Hall sensors are used to detect manipulation, then the reliability improves, but the device complexity increases
Solution Approach 1:
The patent merges multiple Hall sensors into a unified sensor unit that collectively performs both velocity measurement and manipulation detection. The sensors are positioned to form a geometric pattern, and their combined outputs are processed to determine both the velocity magnitude and the authenticity of the magnetic field signals.
Solution Approach 2:
The Hall sensor array serves dual functions: it measures the velocity of the vehicle through magnetic field changes and simultaneously detects manipulation attempts by analyzing the consistency and profile of magnetic field signals from multiple sensor perspectives.
3Measurement precision
If high sampling frequency is used to capture magnetic field changes, then the measurement precision improves, but the use of energy increases
Solution Approach 1:
The patent implements periodic sampling of magnetic field changes at high frequency only when needed for accurate velocity measurement and manipulation detection. The sampling is synchronized with the expected frequency of magnetic field changes from wheel rotation, allowing high precision measurement while minimizing overall energy consumption through targeted high-frequency sampling intervals.
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
Enhances the security of velocity measurement by detecting and preventing manipulation attempts, ensuring accurate and reliable speed data transmission.
Implementation Method 1
A sensor unit has at least one sensor for measuring a quantitative magnetic field strength change
Implementation Method 2
During a revolution of the wheel, the magnet is guided past the Reed contact, whereby it closes and an electrical circuit is thus briefly closed
Data Source
AI summary
The invention relates to a device for ascertaining data for determining a velocity of a vehicle having a magnet, which is attachable to a wheel and executes a circular movement upon rotation of the wheel. Furthermore, a sensor unit is provided for recording signals due to the circular movement of the magnet. The sensor unit has at least one sensor for measuring a quantitative magnetic field strength change. In this case, the sensor is configured to sample the magnetic field strength change at a sampling frequency of at least 200 Hz. In addition, the invention relates to a method for ascertaining data for determining a velocity of a vehicle.