E-bicycle Drive Device Cadence-Based Assistance Control
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Solution Overview
Problem
Existing drive devices for electric bicycles with a single electric motor lack the ability to vary assistance power, as it is proportional to the rider's torque, preventing users from selecting different assistance levels.
Innovation Solution
A drive device with an electronic control unit that allows users to select from predefined assistance levels, specifying a nominal cadence for the bottom bracket shaft, which determines the maximum driving torque provided by the electric motor, enabling different assistance levels without defined additional torque support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electric motor is used with assistance power proportional to rider torque, then the device complexity is reduced, but the ability to vary assistance power levels is lost
Solution Approach 1:
The patent applies parameter changes by linking assistance power to pedaling cadence (speed parameter) rather than only to rider torque. The control unit adjusts the electric motor's driving torque based on the detected cadence, enabling multiple assistance levels (e.g., Eco, Tour, Sport, Boost) with a single motor. This transforms the control parameter from torque-proportional only to cadence-dependent, resolving the contradiction between simplicity and versatility.
2Ease of operation
If assistance power is made proportional to rider torque only, then the control system is simplified, but the user cannot select different assistance levels
Solution Approach 1:
The patent implements dynamics by making the assistance power dynamically adjustable through cadence detection. The control unit continuously monitors the bottom bracket shaft's rotation speed and adjusts the electric motor's torque output in real-time based on the detected cadence. This dynamic control enables users to experience different assistance levels by varying their pedaling speed, maintaining operational simplicity while adding versatility.
3Adaptability or versatility
If multiple predefined assistance levels are introduced with different nominal cadences, then the adaptability to different rider types is improved, but the control system complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple assistance levels with specific nominal cadence values (e.g., 60 rpm for Eco, 80 rpm for Tour, 100 rpm for Sport, 120 rpm for Boost). These predetermined cadence thresholds are stored in the control unit, allowing it to automatically determine the appropriate assistance level based on detected cadence without requiring complex real-time calculations. This pre-programming approach enhances adaptability while keeping the control system manageable.
Data Source
AI summary
It is provided a drive device for an electric bicycle, comprising a bottom bracket shaft for driving a wheel of the electric bicycle by muscle power, an electric motor for providing an additional driving torque for driving the wheel, and an electronic control unit for controlling the electric motor. Via the control unit a nominal cadence can be specified for the bottom bracket shaft by a user of the electric bicycle by selecting one of at least two different predefined assistance levels, from which a maximum driving power is provided by the electric motor.