Power Assisted Driving System Virtual Stroke Actuation
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Solution Overview
Problem
Conventional electric bicycles face inefficiencies in power transmission, particularly at low speeds, due to the reliance on speed sensors that provide maximum motor torque based on crankshaft RPM, leading to reduced power supplementation and increased energy consumption, along with mechanical torque sensors that are costly and difficult to install.
Innovation Solution
A power-assisted driving system utilizing virtual stroke actuation (VSA) measures both angle and torque of the crank to determine the necessary voltage or current for motor power supplementation, improving energy efficiency and reducing torque variations, thereby enhancing ride comfort and accelerating smoothly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a speed sensor operating in digital method is used to control motor output, then the device complexity is reduced, but it is difficult to use the speed sensor through conventional analog signal processing methods
Solution Approach 1:
The patent replaces the conventional analog signal processing method with a digital signal processing approach. The control unit is configured to receive and process digital pulse signals from the speed sensor, converting the mechanical/analog signal processing paradigm into a digital one, thereby enabling compatibility between digital speed sensors and motor control systems.
Solution Approach 2:
The patent changes the signal processing parameter from analog voltage levels to digital pulse frequency/counting. By transforming the signal domain from analog to digital, the system can effectively utilize digital speed sensors while maintaining precise motor control capability through pulse counting and frequency analysis.
2Ease of operation
If power is supplemented in proportion to crankshaft RPM measured by Hall sensor, then the ease of operation is improved, but power is rapidly reduced at low speed when high power is necessary
Solution Approach 1:
The patent implements dynamic motor control by making the motor torque proportional to the instantaneous crankshaft speed. The control unit continuously adjusts the motor torque based on real-time speed feedback from the Hall sensor, creating a dynamic response that supplements power effectively across the entire speed range, particularly improving low-speed performance while maintaining operational simplicity.
3Ease of operation
If motor is driven in phase angle section of crank where power transmission efficiency of rider is high, then the ease of operation is improved, but energy efficiency of total system is reduced
Solution Approach 1:
The patent employs feedback control by using the Hall sensor to detect crankshaft position and speed, then feeding this information back to the control unit which adjusts motor torque accordingly. This closed-loop feedback system enables the motor to supplement power in phases that optimize overall energy efficiency while maintaining pedaling smoothness, rather than operating in fixed phase angle sections.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The VSA system improves energy efficiency, reduces strange pedaling sensations, and enhances ride comfort by accurately predicting driver intent and optimizing motor power delivery, while maintaining output power with reduced weight.
Implementation Method 1
The speed sensor, which utilizes a Hall effect, is generally installed on a crankshaft of the electric bicycle and detects rotation of the crankshaft through a voltage generated due to the Hall effect
Data Source
AI summary
According to one embodiment of the present invention, provided is a power assisted driving system comprising: a measurement part for measuring an operation state of a crank; a control part for determining a voltage or current necessary for power assistance on the basis of the measured value of the measurement part; a motor part, to which the voltage or current is applied, for providing driving power; and a power supply part for providing electric power to components other than itself.