Bicycle Motor Control for Downshift Assistance
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Solution Overview
Problem
Electrically assisted bicycles experience a decrease in pedaling force and assistance force from the drive assistance electric motor during downshifts, leading to insufficient assistance when climbing, which affects riding comfort.
Innovation Solution
A bicycle control apparatus that includes a pedaling force detector and a controller to increase the output ratio of the drive assistance electric motor relative to pedaling force after a downshift, and subsequently decrease it, ensuring consistent assistance force and reducing electric power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive assistance electric motor controls assistance force based on pedaling force, then the assistance force responds to rider input, but the assistance force decreases when pedaling force decreases during downshift
Solution Approach 1:
The control section dynamically adjusts the assistance force output ratio based on gear shift state. When a downshift is detected, the control section increases the assistance force output ratio to compensate for the decrease in pedaling force, making the assistance force characteristics changeable according to operating conditions rather than fixed based solely on pedaling force detection
Solution Approach 2:
The control section uses feedback from gear shift detection to modify the assistance force control strategy. By detecting the downshift state and responding with increased assistance force ratio, the system creates a feedback loop that maintains assistance force consistency across different gear states, preventing the assistance force drop that would otherwise occur during downshifts
2Force
If the transmission downshifts, then the gear ratio changes to provide more torque, but the pedaling force decreases causing insufficient assistance force
Solution Approach 1:
The control section anticipates the assistance force deficiency that will occur during downshift by increasing the assistance force output ratio in response to detected downshift. This preliminary counter-action compensates for the expected drop in pedaling force, ensuring that the overall assistance force remains sufficient even though the rider's pedaling force has decreased
Solution Approach 2:
The control section changes the assistance force output ratio parameter based on gear shift state. By increasing this ratio during downshift, the system adjusts the motor's contribution to compensate for the reduced pedaling force, thereby maintaining adequate total assistance force despite the parameter change in gear ratio
3Reliability
If the ratio of motor output to pedaling force is increased after downshift, then the assistance force is maintained, but electric power consumption increases
Solution Approach 1:
The control section applies increased assistance force output ratio temporarily only during and immediately after the downshift event. Once the gear shift is complete and normal pedaling resumes, the control section returns the assistance force output ratio to its original level. This periodic application of increased motor output limits energy consumption to only when necessary for maintaining assistance force consistency during gear transitions
Data Source
AI summary
A bicycle control apparatus is configured to control a bicycle having a transmission and a drive assistance electric motor that drives a wheel. The bicycle control apparatus includes a pedaling force detector and a controller. The pedaling force detector detects a pedaling force. The controller includes a control section that controls the drive assistance electric motor according to a pedaling force detected by the pedaling force detector. The control section increases a ratio of an output of the drive assistance electric motor with respect to the pedaling force upon completion of a downshift of the transmission, and subsequently decreasing the ratio of the output of the drive assistance electric motor with respect to the pedaling force.