Magnetic Sensor Compensation for E-Bike Speed Detection
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Solution Overview
Problem
The increasing power densities of electric drive units in e-bikes, coupled with decreasing space for shielding elements, lead to interference with magnetic field sensors, compromising the accuracy of speed determination by magnetic field detection.
Innovation Solution
A method involving a control device to operate the electric drive unit at multiple load points, using a magnetic field sensor to measure the temporal profile, and a compensation device to compensate for interference based on a functional relationship between the drive unit's operating parameters, allowing for reliable speed determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If magnetic sensors are used to detect interfering magnetic fields, then detection capability is improved, but measurement precision deteriorates due to disturbances from drive units
Solution Approach 1:
The patent applies preliminary action by determining the functional relationship between drive unit operating variables and interfering magnetic fields before actual measurement. The system pre-calculates expected interference based on drive unit status, then uses this information to compensate for disturbances during sensor measurements, thereby maintaining both detection capability and measurement precision
Solution Approach 2:
The patent implements feedback by continuously monitoring drive unit operating variables and using this information to adjust magnetic field measurements. The system feeds back the relationship between drive unit status and magnetic interference to correct sensor readings in real-time, eliminating the precision deterioration caused by drive unit disturbances
2Area of stationary object
If magnetic sensors are installed near drive units for space efficiency, then device compactness is improved, but measurement precision deteriorates due to electromagnetic interference
Solution Approach 1:
By implementing feedback loops that continuously monitor drive unit operating variables and adjust magnetic field measurements accordingly, the system can maintain high measurement precision even with sensors positioned close to drive units. The feedback mechanism compensates for the electromagnetic interference that would otherwise degrade precision
Solution Approach 2:
The patent introduces an intermediary computational layer that processes the relationship between drive unit operating variables and magnetic fields. This intermediary system calculates expected interference and uses it to correct sensor readings, allowing compact sensor placement without sacrificing measurement precision
3Measurement precision
If multiple sensors are used to compensate for interfering magnetic fields, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by utilizing drive unit operating variables (such as current, speed, or position parameters) to characterize and compensate for interfering magnetic fields. By changing from physical sensor multiplication to parameter-based compensation, the system maintains measurement precision while reducing device complexity
Solution Approach 2:
The patent replaces the mechanical approach of using multiple physical sensors with a computational method that uses drive unit operating parameters. This substitution eliminates the need for additional sensor hardware and complex sensor arrays, reducing device complexity while maintaining measurement precision through mathematical compensation
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 speed measurement by compensating for interference from the drive unit's magnetic field, ensuring robust and reliable speed determination even in the presence of adjacent drive unit influences.
Implementation Method 1
a magnetic sensor (32) arranged to detect the interfering magnetic field (B)
Implementation Method 2
determining, by the processor (33), a functional relationship between at least one operating variable of the drive unit (1) and the interfering magnetic field (B)
Data Source
Figure 1~2
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AI summary
The invention relates to a method for ascertaining a speed of a vehicle and to a vehicle, in particular a single-track vehicle such as a pedelec, the vehicle having an electric drive unit, a magnetic field sensor and a magnet arranged on a wheel of the vehicle, comprising: – a control device, configured for operating the electric drive unit of the vehicle at a plurality of load points by varying at least one operating variable such as current intensity and/or rotational speed, – a first determining device, configured for determining a functional relationship between a specific interfering magnetic field and the at least one operating variable, – a measuring device, comprising the magnetic field sensor and configured for measurement of a temporal profile of a magnetic field by means of the magnetic field sensor and also of the at least one operating variable of the drive unit such as a current intensity of the drive unit and/or a rotational speed of the drive unit, – a compensating device, configured for compensation of the measured temporal profile of the magnetic field on the basis of the functional relationship and also of the at least one measured operating variable of the drive unit, – a second determining device, configured for determining the speed of the vehicle on the basis of the compensated temporal profile of the magnetic field.