Electric Motor Mode Switching Under Battery SOC Constraints
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Solution Overview
Problem
Existing battery electric vehicles face limitations in driving modes due to battery state of charge (SOC), which can lead to overcharge or overdischarge, constraining the driver's experience when switching between manual transmission (MT) and electric vehicle (EV) modes.
Innovation Solution
A battery electric vehicle system with an electric motor, accelerator pedal, shifter, mode selector, and control device that allows switching between MT and EV modes, controlling the electric motor based on SOC to maintain optimal battery conditions and driver experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the driver selects MT mode to drive like a manual transmission vehicle, then the driver can enjoy manual transmission driving experience, but the SOC may become close to overcharge or overdischarge regions causing power limitations
Solution Approach 1:
The control mode dynamically changes based on battery SOC conditions. When SOC is within the predetermined range, the system allows selective switching between MT mode and EV mode. When SOC exceeds the range, the system automatically transitions to a different control strategy that prioritizes battery protection while maintaining drivability.
Solution Approach 2:
The control device acts as an intermediary between the driver's mode selection and the actual motor control. It mediates by monitoring SOC and automatically adjusting the control mode when necessary, preventing direct conflict between driver intent and battery safety requirements.
2Reliability
If the driver selects EV mode for normal battery electric vehicle driving, then the supplied and regenerative power are controlled with reference to SOC, but the driver's desire to drive like an MT vehicle is constrained
Solution Approach 1:
The system dynamically adapts its behavior based on SOC conditions. Within the predetermined SOC range, the system provides full adaptability allowing selection between MT and EV modes. Outside this range, the system transitions to a protective mode that maintains basic drivability while preventing harmful battery states.
3Reliability
If the supplied power is limited by allowable discharge power to prevent overdischarge, then the battery is protected from overdischarge, but the acceleration performance is reduced
Solution Approach 1:
The system establishes a predetermined SOC range in advance that defines the operational boundaries. By keeping SOC within this range, the system proactively prevents overdischarge conditions before they occur, maintaining both battery protection and adequate power availability for acceleration.
4Reliability
If the regenerative power is limited by allowable charge power to prevent overcharge, then the battery is protected from overcharge, but the deceleration energy recovery is reduced
Solution Approach 1:
The system pre-defines the upper boundary of the predetermined SOC range to prevent overcharge conditions. By maintaining SOC below this threshold, the system ensures that regenerative braking can operate effectively without risking battery damage, balancing energy recovery with battery protection.
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
Enables the driver to enjoy both MT and EV driving experiences while minimizing the impact of SOC limitations, ensuring consistent acceleration and deceleration feelings by limiting modes when SOC is out of range.
Implementation Method 1
an electric motor configured to run on power supplied from a battery
Implementation Method 2
stores regenerative power in the battery
Data Source
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AI summary
A battery electric vehicle includes an accelerator pedal, a shifter, a mode selector, and a control device. The mode selector selects either an EV mode or an MT mode as a control mode for an electric motor according to a mode selection operation by a driver. When the SOC of a battery is within a predetermined range, the control device controls the electric motor in the control mode selected by the mode selector. When the SOC is out of the predetermined range, the control device controls the electric motor in the EV mode regardless of the control mode selected by the mode selector.