E-bike Push Assist Speed Control via Gear Ratio Detection
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Solution Overview
Problem
Existing electric bicycle systems require switching to a known transmission ratio for the gear shift to achieve a defined speed during push-assist operation, which is inconvenient and may not accurately maintain the maximum allowed speed.
Innovation Solution
A control method that uses sensors to detect the current speed and engine speed of an electric bicycle, determining the engaged transmission ratio, and adjusts the motor torque to maintain a constant speed without needing to switch transmission ratios, allowing the electric bicycle to operate comfortably and safely at the maximum allowed speed for push-assist, such as 6 km/h, while automatically activating the push-assist when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gear shift is switched to a known transmission ratio to achieve a defined speed during push-assist operation, then the speed can be controlled to match legal limits, but the operation becomes inconvenient and requires manual intervention
Solution Approach 1:
The control device automatically determines the engaged transmission ratio by detecting engine speed and bicycle speed, eliminating the need for manual gear shifting. The system self-adjusts the pushing aid speed based on detected parameters, making the operation convenient while maintaining precise speed control within legal limits.
2Reliability
If the transmission ratio is changed to a defined ratio for push-assist mode, then the speed can be maintained at legal limits, but the system complexity increases due to manual switching requirements
Solution Approach 1:
The control device continuously detects engine speed and bicycle speed, determines the current transmission ratio, and adjusts the pushing aid torque accordingly to maintain compliance with speed limits. This closed-loop feedback system ensures reliable speed limit adherence without requiring complex manual switching mechanisms.
3Speed
If a sensor with fast detection capability is used, then the speed detection response time is improved, but the device complexity and cost increase
Solution Approach 1:
The control device utilizes existing sensors (such as cadence sensors or speed sensors already present in the electric bicycle) for dual purposes: monitoring pedaling cadence during normal operation and detecting bicycle speed during push-assist operation. This multi-functional approach provides fast detection without adding dedicated sensors, thereby avoiding increased device complexity.
Data Source
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AI summary
The present invention relates to a control method for adjusting the speed of the push assist. The invention also relates to a control unit configured to perform this method, as well as an electric bicycle with the control unit. The control method comprises at least one detection of push assist activation. Upon detection of activation, a speed of the electric bicycle or a constant starting torque is generated in the subsequent step by controlling the electric motor. The speed of the push assist generated by the control depends on the selected gear ratio of the transmission. To adjust the speed, the control method includes detecting the current motor speed of the electric motor and detecting the current speed of the electric bicycle.The selected gear ratio is determined based on the detected motor speed and the detected vehicle speed. The speed of the e-bike is then adjusted by regulating the electric motor according to the determined gear ratio and the maximum speed, which is not exceeded.