Electro-Mechanical Bicycle Transmission Torque Control
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Solution Overview
Problem
The unpredictable nature of cyclist pedaling makes control and operation of electro-mechanical drive arrangements in pedal cycles problematic, as they differ significantly from engine control systems.
Innovation Solution
A method involving an electro-mechanical drive arrangement with an input electrical machine, an output electrical machine, and an epicyclic gear set, where the current in the input electrical machine is controlled to automatically change gear based on the angular position of the crank arms, ensuring the torque applied by the cyclist is within predetermined limits, thereby mimicking the behavior of a conventional geared cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If electro-mechanical drive arrangement is used in pedal cycle, then electrical assistance and energy recovery are provided, but control and operation become problematic due to unpredictable cyclist pedaling
Solution Approach 1:
The system automatically controls the input electrical machine as a generator to regulate torque within predetermined limits, eliminating the need for manual intervention. The controller autonomously manages energy recovery and transmission ratio changes based on cyclist pedaling input, making the system self-regulating despite unpredictable human operation patterns
Solution Approach 2:
The system continuously monitors torque applied by the cyclist and adjusts the input electrical machine's generator mode accordingly, maintaining torque within predetermined limits. This feedback loop enables automatic adaptation to varying pedaling forces while recovering energy efficiently
2Extent of automation
If current control in input electrical machine is implemented, then automatic transmission-ratio control is achieved, but device complexity increases
Solution Approach 1:
The input electrical machine serves multiple functions: it operates as a motor during electrical assistance, as a generator during energy recovery, and as a torque regulator for automatic transmission ratio control. This multi-functionality reduces the need for separate dedicated components for each function
Solution Approach 2:
The system combines the transmission control function with the electrical machine control by using the same input electrical machine for both torque regulation and driving the output. The epicyclic gear set integrates mechanical gear changing with electrical control, merging multiple functions into a unified system
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
This method provides automatic transmission-ratio control, allowing the pedal cycle to automatically change gears in response to varying cyclist torque, enhancing efficiency and ease of use by mimicking the behavior of conventional cycles, while also providing electrical assistance when needed.
Implementation Method 1
operating the input electrical machine as a generator to at least partly power the output electrical machine as a motor
Implementation Method 2
an input epicyclic gear set; wherein, of the input epicyclic gear set, a first component is coupled to be driven by crank arms of the cycle, a second component is coupled to one of the rotor and stator of the input electrical machine, the other of the rotor and stator being fixed relative to the cycle, and the third component is coupled to drive a wheel of the cycle
Data Source
AI summary
A method is provided for controlling operation of a pedal cycle (10) having a rear hub-mounted electro-mechanical transmission arrangement in which a chain-driven rear sprocket (80), an input electrical machine (120) and the hub (100) are each coupled to a respective branch of a three-branch epicyclic gear set (140). Allowing for natural variations in input torque by a cyclist over a cycle of the crank arms (50), a substantially constant current is caused to exist in the input electrical machine (120) such that a change in torque applied by the cyclist results in a change in transmission ratio between the rear sprocket (80) and the hub (100), thereby providing a form of automatic and continuously variable transmission for the pedal cycle (10).