E-bike Motor Torque Limiting Control for Stopped Crank
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Solution Overview
Problem
Existing control devices for human-powered vehicles with assist motors lack efficient control mechanisms to limit propulsion force when the crank axle is stopped, leading to unnecessary energy consumption and inefficient power management.
Innovation Solution
A control device with an electronic controller that drives the motor to maintain rotational torque within specific limits (1 Nm to 10 Nm) when the crank axle is stopped, and adjusts current values and transmission ratios to optimize propulsion force and reduce energy consumption, including conditions for derailleur operation and vehicle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the motor is driven without torque limitation when the crank axle is stopped, then the motor can provide sufficient propulsion force, but energy consumption increases unnecessarily
Solution Approach 1:
The control device changes the motor's operational parameters by implementing torque limitation (1-10 Nm) and current limitation (5A or less) when the crank axle is stopped, transforming the motor from high-power propulsion mode to low-power maintenance mode, thereby resolving the contradiction between providing sufficient propulsion force and reducing energy consumption
2Power
If the motor provides high propulsion force when the crank axle is stopped, then the vehicle can be moved, but the motor consumes excessive energy
Solution Approach 1:
The control device applies partial action by limiting the motor's power output to specific ranges (torque: 1-10 Nm, current: 5A or less) when the crank axle is stopped, providing just enough power for maintenance positioning or minor movement while avoiding excessive energy consumption, thus resolving the contradiction between propulsion power and energy waste
3Stability of the object's composition
If the motor is continuously driven to maintain vehicle position, then positioning accuracy is improved, but energy consumption increases
Solution Approach 1:
The control device implements periodic action by activating the motor only when specific conditions are met (crank axle stopped, derailleur operating, or vehicle speed below threshold) rather than continuous operation, maintaining position stability during critical moments while minimizing energy consumption during normal operation
4Force
If the motor operates at high current values, then the motor can deliver sufficient driving force, but power management efficiency decreases
Solution Approach 1:
The control device changes the motor's current parameter from unrestricted high current operation to limited current operation (5A or less) when the crank axle is stopped, maintaining sufficient driving force for position maintenance while significantly improving power management efficiency by preventing excessive current draw
Data Source
AI summary
A control device is provided for a human-powered vehicle that includes a crank axle configured to receive a human driving force, a first rotational body connected to the crank axle, a second rotational body connected to a wheel, a transmission body engaged with the first and second rotational bodies to transmit a driving force between the first and second rotational bodies, and a motor configured to drive the transmission body. The control device includes an electronic controller configured to control the motor. Upon a predetermined condition being satisfied, the electronic controller drives the motor so that a rotational torque of the first rotational body produced by the motor is kept less than or equal to a predetermined torque which is 1 Nm or greater and 10 Nm or less. The predetermined condition includes a first condition in which rotation of the crank axle is stopped.