E-Bike Assist Force Calculation Using Variable Smoothing

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Solution Overview

Problem

Existing electrically assisted bicycle assist force calculation methods require complex mode settings to manage assist torque changes based on varying pedal loads, leading to cumbersome scenario-specific configurations.

Innovation Solution

An assist force calculation method that uses an instant pedaling force sensor and a crank advance angle sensor with high resolution to determine assist forces, combining instant and reference pedaling forces through a virtual pedaling force calculation, allowing for adaptive assist force output across different scenarios without the need for multiple mode settings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the smoothing factor is reduced to improve responsiveness of assist torque to input torque changes, then the assist force becomes weak at top dead center and bottom dead center when pedal load is small, but this creates the need for multiple mode settings to handle different scenarios

Engineering Contradiction:

Improveresponsiveness of assist torqueVSAvoidcontrol mode complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent applies dynamics by making the smoothing factor variable rather than fixed. The control unit dynamically adjusts the smoothing factor based on real-time detection of pedal load magnitude, allowing the system to adapt its responsiveness characteristics to current operating conditions without requiring manual mode selection or complex scenario-based configurations

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of smoothing factor from a static value to a dynamically adjustable parameter. By modifying the smoothing factor according to detected pedal load conditions, the system optimizes assist torque responsiveness for different scenarios automatically, eliminating the need for multiple predetermined control modes

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the smoothing factor is increased to smooth assist torque changes, then the assist force follows input torque changes more smoothly, but the responsiveness to sudden pedaling changes deteriorates

Engineering Contradiction:

Improvesmoothness of assist torqueVSAvoidresponsiveness to pedaling changes

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The system dynamically adjusts the smoothing factor based on real-time pedal load detection, allowing it to transition between smooth and responsive modes automatically. When pedal load indicates steady-state operation, higher smoothing is applied for stability; when sudden changes are detected, smoothing is reduced for responsiveness

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The smoothing factor parameter is changed from a fixed value to a variable that adapts to operating conditions. This allows the system to optimize the balance between smoothness and responsiveness by adjusting the parameter according to actual pedaling patterns rather than relying on predetermined modes

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11117640B2Electrically assisted bicycle assist force calculation method, electrically assisted bicycle control unit, electrically assisted bicycle power unit, and electrically assisted bicycle

Publication Date: 2021.09.14 YAMAHA MOTOR CO LTD

AI summary

An electrically assisted bicycle assist force calculation method includes obtaining from a pedaling force sensor an instant pedaling force applied to a pedal, obtaining a crank advance angle of a crankshaft from an advance angle sensor having a resolution of less than 90°, and determining an assist force based on at least the instant pedaling force and the crank advance angle.