Human-Powered Vehicle Control Device for Dynamic Transmission Ratio Stability
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Solution Overview
Problem
Existing human-powered vehicle control devices struggle to maintain optimal transmission ratios during varying human driving forces, leading to inefficient propulsion and potential transmission failures due to sudden load changes.
Innovation Solution
A control device with an electronic controller that adjusts the assist state and transmission ratio based on peak human driving force thresholds, change rates, and duration, ensuring stable propulsion by maintaining optimal assist force ratios and preventing transmission ratio changes during high loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transmission ratio is automatically changed in accordance with travel state, then propulsion efficiency is improved, but transmission stability deteriorates under high human driving force conditions
Solution Approach 1:
The control device dynamically adjusts transmission ratio based on real-time detection of human driving force parameters. When peak driving force exceeds threshold values or change rates exceed thresholds, the system dynamically maintains transmission ratio to prevent instability, while allowing ratio changes under stable conditions to optimize propulsion efficiency.
Solution Approach 2:
The system changes the control parameter from continuous transmission ratio adjustment to conditional maintenance. By monitoring multiple parameters (peak driving force, change rate, duration), the system determines when to maintain transmission ratio constant rather than continuously adjusting it, thereby preventing instability while preserving efficiency.
2Loss of energy
If transmission ratio changes are made to optimize propulsion, then energy efficiency is improved, but transmission failure risk increases due to sudden load changes
Solution Approach 1:
The control device performs preliminary detection of human driving force parameters before executing transmission ratio changes. By detecting peak driving force values and change rates in advance, the system identifies unsuitable conditions for transmission switching and prevents changes that would cause sudden load variations, thereby avoiding transmission failure while maintaining energy efficiency.
Solution Approach 2:
The system continuously monitors multiple parameters including peak driving force, change rate, and duration, using this feedback to determine whether transmission ratio changes are appropriate. When parameters indicate high load or rapid changes, the feedback mechanism prevents transmission switching, reducing failure risk while preserving energy-efficient operation under stable conditions.
3Productivity
If assist force is adjusted according to human driving force, then propulsion optimization is improved, but control complexity increases
Solution Approach 1:
The control device segments the control logic into distinct detection and determination phases. It separately detects peak driving force values, change rates, and duration, then determines transmission ratio maintenance based on these segmented parameters. This segmentation simplifies the control algorithm while achieving optimized propulsion by addressing each parameter independently.
Data Source
AI summary
A control device for a human-powered vehicle including a motor that applies a propulsion force to the human-powered vehicle, a crank axle, a driving wheel, and a transmission that automatically changes a transmission ratio of a rotational speed of the driving wheel to a rotational speed of the crank axle in accordance with a travel state of the human-powered vehicle. The control device includes an electronic controller that controls the motor in accordance with a human driving force input to the crank axle. The controller changes an assist state related to at least one of an assist ratio of an assist force by the motor to a predetermined human driving force and the assist force by the motor in accordance with the human driving force and controls the transmission to maintain the transmission ratio upon determining a parameter related to the human driving force satisfies a predetermined condition.