Gear-Shifting Control for Power-Assisted Bicycles
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Solution Overview
Problem
Conventional power-assisted bicycles perform gear-shifting operations while the cyclist is pedaling, leading to confusion between the cyclist's pedaling force and the motor's assisting power, resulting in poor gear engagement and potential damage to the chain and transmission.
Innovation Solution
A gear-shifting system that detects pedal positions to reduce assisting power during gear-shifting operations, using a microcomputer, a gear-shifting driver, and a pedal position sensing module to minimize the risk of damage by controlling the gear-shifting based on crank angular positions and pedaling torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the microcomputer performs gear-shifting operation while the cyclist is pedaling, then the gear-shifting function is realized, but the cyclist's pedaling force and motor's assisting power cause poor gear engagement and potential damage to chain and transmission
Solution Approach 1:
The system performs preliminary actions by reducing the assisting power output before the gear-shifting operation begins. The microcomputer detects when gear-shifting is needed and proactively reduces motor power to a lower level before the actual gear change occurs, preparing the system for smooth gear engagement without the interference of high assisting power
Solution Approach 2:
The system applies preliminary anti-action by reducing the assisting power output in advance to counteract the harmful effect of excessive power during gear-shifting. This preemptive reduction prevents the chain and transmission from experiencing damaging forces during the gear engagement process
2Power
If the microcomputer outputs adequate assisting power during gear-shifting, then the cyclist experiences adequate power support, but the chain and transmission are at risk of damage due to poor gear engagement
Solution Approach 1:
The microcomputer takes preliminary action by reducing the assisting power output before the gear-shifting operation begins. This proactive power reduction ensures that when the gear change occurs, the motor is not applying excessive force that could damage the transmission components
Solution Approach 2:
The system applies beforehand cushioning by reducing the assisting power to a lower level prior to gear-shifting. This creates a cushioning effect that protects the chain and transmission from sudden shock loads during gear engagement, while still maintaining operational power after the shift is complete
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
Ensures smooth gear-shifting and reduces the risk of damaging the chain and transmission by minimizing the assisting power during gear changes, thereby preventing chain breakage and transmission damage.
Implementation Method 1
a pedal position sensing module, deposited on the power-assisted bicycle and aligned with at least one crank of the power-assisted bicycle, and electrically connected to the microcomputer, so that the microcomputer can learn the angular position of the at least one crank from the pedal position sensing module
Data Source
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AI summary
A gear-shifting system (10)(10') for a power-assisted bicycle (90) includes: a power supply module (11); a microcomputer (21)(21'); a gear-shifting driver (31); and a pedal position sensing module (41) for detecting an angular position of a crank (95) of the power-assisted bicycle (90). The microcomputer (21)(21') has a gear-shifting operation logic (22)(22') and is configured to execute the gear-shifting operation logic (22)(22') before performing a gear-shifting operation. Steps for executing the gear-shifting operation logic (22) include: (1) when the angular position of the crank (95) passes through a first angular position (P1), reducing the assisting power output by the motor (91) to a first power value; (2) when the angular position of the crank (95) leaves the first angular position (P1) and passes through a dead point (Pd), minimizing the assisting power output by the motor (91); (3) performing the gear-shifting operation; (4) when the gear-shifting operation is finished, returning the assisting power output by the motor (91) to a level of the assisting power before the step (1).