Torque Estimation via Angular Velocity Fluctuations
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Solution Overview
Problem
Existing methods for recording pedal crank performance in electric bicycles are prone to errors due to the complexity and exposure of torsion sensors, and alternative approaches that simulate driving environments are not suitable for bicycles.
Innovation Solution
Estimating torque by analyzing fluctuations in pedal crank speed using an angular velocity sensor, which records the alternating component of the angular velocity and determines torque based on the deviation from a sinusoidal curve, leveraging the relationship between speed irregularity and torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torsion sensor is arranged directly on the pedal crank to mechanically detect torque, then torque measurement is achieved, but the device becomes complex and prone to errors due to exposure to external influences
Solution Approach 1:
The patent replaces the mechanical torsion sensor system with an optical/electronic system. Instead of mechanically detecting torque through a torsion sensor on the pedal crank, the system uses an angular velocity sensor to detect rotational speed and employs electronic evaluation to determine torque from speed fluctuations. This substitution eliminates the need for exposed mechanical sensors while maintaining measurement capability.
Solution Approach 2:
The patent introduces an intermediary evaluation system that indirectly determines torque through angular velocity measurements. Rather than directly measuring torque with an exposed sensor, the system uses angular velocity fluctuations as an intermediate parameter to infer torque values through electronic processing and comparison with characteristic curves.
2Measurement precision
If friction forces are used to simulate driving environment in bicycle training devices, then pedal power recording is achieved, but the pedal crank drive is braked strongly making it unsuitable for actual bicycles
Solution Approach 1:
The patent extracts the measurement function from the mechanical drive system itself. Instead of using friction forces that interfere with normal bicycle operation, the system extracts angular velocity information from the existing crank rotation and uses electronic evaluation to determine torque, allowing the bicycle to operate normally without braking or friction-based simulation.
3Productivity
If the speed curve of the bicycle is used to determine driver power contribution, then power estimation is possible, but the speed curve alone is not distinctive enough to accurately reflect actual pedal drive performance
Solution Approach 1:
The patent dynamically analyzes angular velocity fluctuations at multiple frequencies rather than relying on average speed. By examining the dynamic variations in angular velocity, particularly at the fundamental frequency of pedal rotation and its harmonics, the system can distinguish actual pedal drive performance from other speed-affecting factors, providing more accurate power estimation.
Solution Approach 2:
The patent performs preliminary characterization by storing characteristic curves that represent the relationship between angular velocity fluctuations and torque under various conditions. These pre-established reference curves enable the evaluation system to compare real-time measurements against known patterns, improving the accuracy of power estimation without requiring complex real-time calculations.
Data Source
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AI summary
The invention relates to a method for estimating a torque exerted on a pedal crank of an electric bicycle. The method provides for the detection of an angular velocity at which the pedal crank is driven, depending on the time. At least one signal property of the angular velocity is determined. The signal property is selected from the group consisting of the power of the AC component of the angular velocity, and the deviation of the signal shape of the AC component of the angular velocity from a sine curve which has the same frequency as the AC component of the angular velocity. Lastly, the torque is associated with the at least one determined signal property by means of a predetermined dependency between the at least one signal property and the associated torque. The invention further relates to an associated device and to an electronically retrievable memory which stores the link on which the association according to the invention is based.