Bicycle Drive Motor Synchronization via Variable Speed Gradients
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Solution Overview
Problem
Modern bicycles with drive motors face challenges in synchronizing motor assistance with uneven pedaling, leading to undesirable effects such as strenuous start-up, sudden engagement, noise, and component strain due to fluctuating pedaling speeds.
Innovation Solution
A method involving a freewheel clutch that automatically switches between locked and released states, combined with a variable target speed gradient control to synchronize the drive motor with the pedal crankshaft, adjusting acceleration based on pedaling dynamics to ensure smooth engagement and reduce jerky movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the drive motor synchronizes with the pedaling speed too quickly, then the motor assistance becomes available faster, but it causes loud noises, excessive strain on drive train components, and unpleasant jolts for the user
Solution Approach 1:
The patent applies dynamics by making the speed gradient variable rather than fixed. The control device adjusts the target speed gradient dynamically based on the current speed difference between motor and pedal crankshaft, using higher gradients when the difference is large and lower gradients when approaching synchronization, thereby resolving the contradiction between fast synchronization and avoiding mechanical harm
Solution Approach 2:
The patent changes the parameter of speed gradient from a constant value to a variable value that adapts to the synchronization progress. By modifying the target speed gradient parameter based on real-time speed difference measurements, the system achieves both rapid synchronization and smooth engagement without excessive strain or noise
2Object-affected harmful factors
If the drive motor takes too long to synchronize with the pedaling speed, then the synchronization is smooth and strain-free, but the user experiences reduced motor assistance performance and the start-up process becomes too strenuous
Solution Approach 1:
The system dynamically adjusts the speed gradient based on the current state, allowing aggressive acceleration when the motor is far from synchronization speed (maintaining productivity) and gentle approach when near synchronization (reducing mechanical strain), thus resolving both requirements simultaneously
Solution Approach 2:
The control device performs preliminary action by proactively adjusting the target speed gradient before synchronization occurs. It anticipates the synchronization point and prepares the motor speed in advance, ensuring both rapid response and smooth engagement by planning the acceleration profile ahead of time
3Device complexity
If the drive motor uses a fixed speed gradient to synchronize with the pedal crankshaft, then the control is simple, but it cannot adapt to fluctuating pedaling speeds and causes sudden engagement or excessive strain
Solution Approach 1:
The patent changes the control parameter from a fixed speed gradient to a variable one that responds to pedaling fluctuations. The target speed gradient is continuously adjusted based on the measured speed difference, enabling the system to adapt to varying pedaling conditions while maintaining relatively simple control logic
Solution Approach 2:
The system implements feedback by continuously monitoring the speed difference between motor and pedal crankshaft and using this information to adjust the target speed gradient. This closed-loop approach enables adaptation to pedaling variations without significantly increasing control complexity
Data Source
Figure 1~4
AI summary
The present invention relates to a method for controlling a drive motor of a bicycle. The drive motor is mechanically operatively connected to an output element of the bicycle by means of a freewheel. The method comprises at least the following steps: - determining (10) a variable target speed gradient for the drive motor; and - controlling (12) the drive motor as a function of the determined variable target speed gradient in order to approximate a motor speed (22) to a synchronous speed (20) of the freewheel. The invention also relates to a control device and a bicycle.