Bicycle Drive Motor Freewheel Synchronization for Smooth Pushing
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Solution Overview
Problem
Modern bicycles with drive motors face challenges in synchronizing motor speed with wheel speed during pushing, leading to undesirable effects such as excessive strain, noise, and jerky engagement due to uneven pushing speeds and frequent changes in propulsion demands, particularly affecting physically disabled users and heavy cargo bikes.
Innovation Solution
A method involving a freewheel mechanism that connects the drive motor to the bicycle output element, allowing variable target speed gradients to be determined and controlled to smoothly synchronize motor speed with the freewheel's synchronous speed, using a control device to adjust motor torque and power supply based on pushing dynamics and selected assistance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the drive motor synchronizes with the wheel speed quickly, then the motor assistance engages rapidly, but this causes sudden engagement, loud noises, and excessive strain on drivetrain components
Solution Approach 1:
The patent applies dynamics by making the speed gradient adaptive rather than fixed. The control device adjusts the speed gradient in real-time based on the current speed difference between motor and wheel, using a higher gradient when the difference is large and reducing it as synchronization approaches, thereby achieving rapid yet smooth engagement without damaging the drivetrain
Solution Approach 2:
The patent changes the parameter of speed gradient from a constant value to a variable parameter that depends on the speed difference. By dynamically adjusting this parameter based on real-time speed measurements, the system optimizes the balance between engagement speed and mechanical stress, preventing noise and strain while maintaining rapid assistance engagement
2Object-affected harmful factors
If the drive motor takes too long to synchronize with the pushing speed, then the synchronization is smooth, but the user experiences poor performance and the bike becomes too strenuous to use
Solution Approach 1:
The system dynamically adjusts the speed gradient based on the current state, allowing rapid initial synchronization to quickly provide motor assistance and reduce user strain, then smoothly transitioning to maintain synchronization. This dynamic approach ensures both rapid response and smooth operation
Solution Approach 2:
The control device performs preliminary action by anticipating the need for motor assistance and initiating the synchronization process immediately when pushing is detected. The adaptive speed gradient ensures the motor prepares to engage rapidly while automatically adjusting to prevent mechanical stress, thus reducing user strain without causing damage
3Adaptability or versatility
If the drive motor uses a fixed speed gradient for synchronization, then the control is simple, but it cannot adapt to varying pushing speeds and causes either excessive strain or prolonged synchronization
Solution Approach 1:
The patent changes the speed gradient from a fixed parameter to a variable parameter that adapts to different pushing conditions. The control device calculates the appropriate speed gradient based on the current speed difference between motor and wheel, enabling the system to adapt to varying pushing speeds while maintaining a relatively simple control structure
Solution Approach 2:
The system implements feedback by continuously monitoring the speed difference between the motor and wheel, then using this information to adjust the speed gradient in real-time. This feedback mechanism enables adaptive control that responds to varying pushing conditions without requiring complex control algorithms
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: - activating (8) a pushing aid by the drive motor; - 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.