E-Bike Assist Motor Control for Reliable Electronic Shifting

Solution Overview

Problem

Existing automatic shifting algorithms for electric bicycles only allow shifting when the drivetrain is moving, and the pedal assist motor can cause unsafe conditions if the rider slows down faster than the motor can react, leading to unreliable electronic shifting.

Innovation Solution

A method for controlling electrically powered components on a bicycle that includes identifying rider engagement status through sensor data, such as orientation and wheel speed, to prevent movement of components like the assist motor when the rider is not riding, ensuring reliable shifting by preventing motor torque when the bicycle is not in use.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the pedal assist motor is active to assist the rider, then the motor can help push the ebike up steep inclines, but the rider may walk beside the ebike and push a button to enable motor assist at low speed, which may cause unsafe conditions if the rider slows down faster than the motor can react

Engineering Contradiction:

Improvemotor assist powerVSAvoidshifting reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The control system performs preliminary detection of rider engagement status using sensor data (crank speed, cadence, torque) before enabling motor assist. This preliminary action ensures the motor only activates when the rider is actually engaged with the bicycle, preventing unsafe conditions where the motor might activate while the rider is walking beside the bike

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors sensor data including crank speed, cadence, and torque to provide real-time feedback on rider engagement status. This feedback mechanism allows the control system to dynamically adjust motor assist activation, ensuring the motor responds appropriately to actual riding conditions and preventing unsafe activation scenarios

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If automatic shifting is enabled to maintain optimal gear ratios, then shifting can occur during riding, but shifting may only occur when the drivetrain is moving, which limits the functionality and reliability of electronic shifting

Engineering Contradiction:

Improveshifting functionalityVSAvoidelectronic shifting reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control system performs preliminary detection of rider engagement status using sensor data (crank speed, cadence, torque) before enabling motor assist. This preliminary action ensures the motor only activates when the rider is actually engaged with the bicycle, preventing unsafe conditions where the motor might activate while the rider is walking beside the bike

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors sensor data including crank speed, cadence, and torque to provide real-time feedback on rider engagement status. This feedback mechanism allows the control system to dynamically adjust motor assist activation, ensuring the motor responds appropriately to actual riding conditions and preventing unsafe activation scenarios

Inventive Principle:

Principle #23Feedback

3Speed

If the assist motor reacts quickly to rider input, then the motor can respond to changes in pedaling rate, but if the rider slows down faster than the motor can react, unsafe conditions may occur

Engineering Contradiction:

Improvemotor response speedVSAvoidunsafe conditions

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The control system performs preliminary detection of rider engagement status using sensor data (crank speed, cadence, torque) before enabling motor assist. This preliminary action ensures the motor only activates when the rider is actually engaged with the bicycle, preventing unsafe conditions where the motor might activate while the rider is walking beside the bike

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors sensor data including crank speed, cadence, and torque to provide real-time feedback on rider engagement status. This feedback mechanism allows the control system to dynamically adjust motor assist activation, ensuring the motor responds appropriately to actual riding conditions and preventing unsafe activation scenarios

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP3696073B1Bicycle control method

Publication Date: 2026.03.18 SRAM LLC

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AI summary

A bicycle with an electric pedal assist motor capable of driving a chainring independent of cranks includes wheel speed sensors and crank cadence sensors. The wheel speed sensors and the crank cadence sensors measure wheel speed and crank cadence, respectively, and provide the measured wheel speed and crank cadence to controller of the bicycle. The controller activates motor overdrive based on the measured wheel speed and/or the measured crank cadence.