Bicycle Gearshift Actuator Control Using Reference Wheel Calibration
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Solution Overview
Problem
Existing bicycle gearshift systems struggle to quickly and efficiently adapt to manufacturing and assembly tolerances, as well as geometric differences in the bicycle frame and components, leading to misalignments and complex adjustments.
Innovation Solution
A method for electronically controlling a bicycle gearshift that uses two reference toothed wheels to determine actual command values, allowing for precise positioning of the chain by computing actual command values based on nominal values, taking into account size differences and tolerances, through a linear transformation and normalization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nominal command values are used for actuator control, then the gearshift system can operate with standard factory settings, but manufacturing and assembly tolerances cause misalignments between the chain and toothed wheels
Solution Approach 1:
The patent transforms the fixed nominal command values into adjustable actual command values by detecting the real positions of toothed wheels and calculating correction values. This parameter transformation allows the system to adapt to manufacturing tolerances while maintaining ease of manufacture, as the correction values automatically compensate for dimensional variations without requiring manual adjustment of each component.
Solution Approach 2:
The system implements feedback by detecting the actual positions of toothed wheels during operation and using this information to calculate corrected command values for the actuator. This closed-loop approach ensures that manufacturing and assembly tolerances do not affect chain positioning accuracy, as the system continuously adapts to the real geometric conditions of the bicycle.
2Manufacturing precision
If adjustment offset is set at each toothed wheel to compensate for misalignments, then chain positioning accuracy is improved, but the adjustment operation becomes long and complex
Solution Approach 1:
The patent merges the adjustment operation into a single unified process by detecting the positions of only two reference toothed wheels and calculating correction values for all other toothed wheels based on these two measurements. This eliminates the need for separate adjustment operations at each toothed wheel, significantly reducing adjustment time while maintaining positioning accuracy.
Solution Approach 2:
The system performs preliminary detection of two reference toothed wheels to establish correction values before normal operation begins. This preliminary action allows all subsequent gearshift operations to use the pre-calculated correction values, avoiding the need for time-consuming adjustments at each toothed wheel during actual use.
3Manufacturing precision
If setting at a single toothed wheel is performed, then some misalignments are compensated, but manufacturing and assembly tolerances of the gearshift group and bicycle frame are not fully accounted for
Solution Approach 1:
The patent segments the adjustment process by selecting two specific reference toothed wheels (typically the smallest and largest diameter wheels) as measurement points. This segmentation allows the system to capture the geometric variations across the entire gearshift range, providing better adaptability to manufacturing and assembly tolerances compared to single-point setting, while keeping the measurement process simple and quick.
Data Source
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AI summary
A method for electronically controlling a bicycle gearshift (8) is disclosed, comprising the steps of: a) detecting (110, 120) a first actual command value of an actuator such as to position a motion transmission chain in engagement with a first of at least three coaxial toothed wheels (11, 12), and a second actual command value of the actuator (14, 15) such as to position the chain in engagement with a second of said toothed wheels, b) for each toothed wheel, determining (130) a nominal command value of the actuator theoretically such as to position the chain in engagement with said toothed wheel, and c) computing (140) an actual command value of said actuator at least for each of said toothed wheels other than the first and second toothed wheel, based on said nominal command values and on said first and second actual command value. An electronically servo-assisted bicycle gearshift is also disclosed, comprising modules adapted to implement the method outlined above.