Electric Vehicle Braking Torque Distribution for Stability
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Solution Overview
Problem
Regenerative operation of the electric motor in electric vehicles can impair directional stability, especially when the motor is exclusively associated with one axle, leading to reduced driving dynamics and efficiency.
Innovation Solution
A method for braking an electric vehicle that dynamically adjusts the deceleration torque distribution between the electric motor and friction brake system based on directional stability, reducing the electric motor's deceleration torque as stability diminishes, and prioritizing friction brake system deceleration for the second axle to maintain stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor provides deceleration torque through regenerative operation, then energy efficiency is improved, but directional stability deteriorates
Solution Approach 1:
The brake system dynamically adjusts the distribution of deceleration torque between the friction brake system and the electric motor based on real-time driving conditions, vehicle speed, and stability requirements. This dynamic allocation allows the system to maximize regenerative braking when conditions permit while maintaining directional stability, resolving the contradiction between energy efficiency and stability.
Solution Approach 2:
The control device modifies operational parameters by adjusting the deceleration torque provided by the electric motor based on the state of charge of the vehicle battery and current driving conditions. When the battery is fully charged, regenerative braking is reduced or disabled to prevent stability issues; when the battery has capacity, regenerative braking is maximized to improve energy efficiency.
2Device complexity
If the electric motor is exclusively associated with one axle, then device complexity is reduced, but directional stability deteriorates
Solution Approach 1:
The brake system is segmented into two independent parts: a friction brake system that can apply torque to both axles, and an electric motor associated with one axle for regenerative braking. This segmentation allows the friction brake system to compensate for the single-axle electric motor to maintain directional stability while keeping the overall system relatively simple.
Solution Approach 2:
The friction brake system serves a dual function: it provides primary braking and also compensates for the single-axle electric motor to maintain directional stability during regenerative braking. This multi-functionality allows the system to achieve stability without adding complex control mechanisms to the electric motor itself.
3Loss of energy
If regenerative deceleration torque is increased, then energy recovery is improved, but driving dynamics deteriorate
Solution Approach 1:
The system applies partial regenerative braking torque rather than maximum possible torque, adjusting the level of regenerative braking to achieve sufficient energy recovery while maintaining acceptable driving dynamics. The control device modulates the electric motor's deceleration torque to balance energy recovery with vehicle performance requirements.
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 method enhances directional stability and efficiency by optimizing deceleration torque distribution, allowing for high regenerative efficiency while preventing overbraking and maintaining vehicle control through adaptive control of the electric motor and friction brake system.
Implementation Method 1
The electric motor can typically be operated as a generator in a second operating mode, to which generator a torque is applied by the wheels of the electric vehicle, and the kinetic energy from said wheels is converted into electric power to charge the vehicle battery.
Implementation Method 2
a hydraulic friction brake system, which is configured to provide a deceleration torque for wheels of the electric vehicle by applying a friction force to the wheels
Data Source
AI summary
A method for braking an electric vehicle in which a first axle of an electric vehicle is decelerated by an electric motor of the electric vehicle and/or by a friction brake system of the electric vehicle.