Dual-Motor Reduction Ratio Control for EV Drive Mode Switching
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Solution Overview
Problem
Electric vehicles face reduced efficiency in low and high-speed ranges due to fixed gear ratios, leading to limited driving distance and performance issues, particularly when driven for extended periods at high speeds.
Innovation Solution
An electric vehicle control device and method that adjusts the reduction ratios of front and rear wheel motors based on driving speed and mode, allowing for different engagement of clutches to switch between front-wheel, four-wheel, and rear-wheel drive modes, optimizing efficiency across various speed ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed gear ratio reducer is used in electric vehicles, then the structure is simple and mid-speed drive efficiency is optimized, but fuel efficiency significantly reduces in low-speed and high-speed ranges
Solution Approach 1:
The patent applies dynamics by making the reduction ratio changeable rather than fixed. The system dynamically switches between different reduction ratios (first reduction ratio for low-speed, second reduction ratio for high-speed) based on the vehicle's operating conditions, allowing the transmission system to adapt to varying speed requirements and maintain optimal efficiency across the entire speed range.
Solution Approach 2:
The patent changes the parameter of reduction ratio from a fixed value to a variable parameter. By providing at least two different reduction ratios and switching between them based on speed conditions, the system optimizes energy efficiency in both low-speed and high-speed ranges while maintaining the simplicity of the overall structure.
2Productivity
If a fixed gear ratio is set for mid-speed range, then drive efficiency is optimized in practical driving range, but driving distance significantly reduces when driven in low-speed or high-speed range
Solution Approach 1:
The system dynamically selects appropriate reduction ratios based on driving conditions. When operating in low-speed or high-speed ranges, the system switches to the corresponding optimized reduction ratio, preventing significant energy loss and extending the effective driving duration and distance across all speed conditions.
Solution Approach 2:
By changing the reduction ratio parameter according to speed conditions, the system maintains high drive efficiency not only in the mid-speed range but also in low-speed and high-speed ranges, thereby extending the overall driving distance and preventing premature battery depletion.
3Speed
If electric vehicles are driven in high-speed range for long time, then speed performance is maintained, but output performance is limited due to counter-electromotive force generation
Solution Approach 1:
The patent changes the reduction ratio parameter when high-speed operation is detected. By switching to the second reduction ratio (optimized for high-speed range), the system maintains optimal torque multiplication and power output characteristics, counteracting the limitations imposed by counter-electromotive force generation in the motor.
4Duration of action of moving object
If battery capacity is increased to extend driving distance, then driving distance increases, but vehicle price and weight increase
Solution Approach 1:
By changing the reduction ratio parameter based on operating conditions, the system improves overall energy efficiency and reduces energy waste. This allows the vehicle to achieve extended driving distance using the existing battery capacity, eliminating the need to increase battery size and thereby avoiding increased vehicle weight and cost.
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
Improves fuel efficiency, increases driving distance, and enhances performance by adapting motor operation to different speed and driving conditions, addressing the limitations of fixed gear ratios in electric vehicles.
Implementation Method 1
An electric vehicle (EV) is provided with a battery comprised of a plurality of battery cells connected in series or parallel to provide operating power necessary for driving the vehicle. The electric vehicle is provided with a front wheel motor for driving/controlling a front wheel and a rear wheel motor for driving/controlling a rear wheel, and drives by driving the motors on the basis of the operating power supplied from the battery.
Implementation Method 2
In general, an EV drive motor may be used without a transmission, due to a wider usable speed range than internal combustion engines. Thus, each electric vehicle does not include a transmission, and uses a reducer with a fixed gear ratio. The first reducer may have a reduction ratio different from a reduction ratio of the second reducer.
Data Source
AI summary
Provided are an electric vehicle control device and method using the difference in the motor reduction ratio. An input part inputs data regarding driving mode. A sensor detects a driving speed. A processor sets different speed ranges according to the driving mode, controls engagement of a first clutch with respect to a first reducer and operation of a front wheel motor, controls engagement of a second clutch with respect to a second reducer and operation of a rear wheel motor, determines a speed range among the speed ranges corresponding to the driving speed, and controls an electric vehicle to operate in one of front-wheel drive, four-wheel drive, and rear-wheel drive. The clutch and motor driving is controlled variously on the basis of the difference in the reduction ratio of the front wheel and the rear wheel, thereby improving fuel efficiency and improving the driving performance and stability of the electric vehicle.