Four-Wheel EV Brake Control for Maximized Regenerative Torque
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Solution Overview
Problem
Current Battery Electric Vehicles (BEVs) face limitations in maximizing the second share of regenerative braking torque, which restricts battery charging efficiency and increases heat dissipation and wear in the braking system, while also requiring larger braking systems to compensate for limited regenerative capabilities.
Innovation Solution
A control unit programmed to dynamically manage the operation of electric machines as both motors and generators, optimizing torque distribution between axles and wheels to enhance regenerative braking, using specific formulas to process and communicate electrical power and torque values, ensuring efficient energy recovery and reduced heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the braking system is sized to deliver all braking torque without regenerative braking, then braking reliability is ensured, but the second share of regenerative braking torque is limited and battery charging efficiency is reduced
Solution Approach 1:
The brake control unit dynamically adjusts the distribution of braking torque between the hydraulic braking system and electric machines based on real-time operating conditions. The control unit processes the requested braking torque value and dynamically determines the first share (hydraulic) and second share (regenerative) of braking torque, allowing the system to adapt to varying battery charge levels, vehicle speed, and driver braking patterns to maximize energy recovery while ensuring braking reliability
Solution Approach 2:
The system changes the operational parameters of the electric machines between motor mode and generator mode depending on acceleration or braking conditions. During braking, the electric machines operate as generators with variable torque output based on battery state of charge and system requirements, enabling flexible optimization of regenerative braking contribution without compromising overall braking performance
2Use of energy by moving object
If regenerative braking torque is increased, then battery charging is enhanced, but heat dissipation and wear in the braking system must be managed
Solution Approach 1:
The system converts the kinetic energy that would otherwise be wasted as heat during braking into useful electrical energy through regenerative braking. The electric machines capture the energy that would be dissipated by the hydraulic braking system and convert it into electrical power to charge the battery, transforming a harmful energy loss into a beneficial energy recovery opportunity
Solution Approach 2:
The control unit optimizes the second share of braking torque generated by electric machines based on battery state of charge and system capabilities. When battery charge level is high or battery acceptance is limited, the control unit reduces regenerative braking torque to prevent overcharging, allowing the hydraulic system to handle the remaining braking torque, thus avoiding excessive energy recovery that could lead to battery damage
3Loss of energy
If the second share of braking torque from electric machines is maximized, then the first share from the braking system decreases, but braking system size and weight can be reduced
Solution Approach 1:
The electric machines serve multiple functions: they act as motors during acceleration to drive the vehicle, and as generators during braking to recover energy and provide braking torque. This multi-functionality eliminates the need for a dedicated braking system sized for 100% braking torque, as the electric machines share the braking function with the hydraulic system, allowing for a smaller, lighter overall braking system
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
This approach maximizes regenerative braking torque, enhancing battery charging, reducing heat dissipation and wear in the braking system, and optimizing torque distribution for improved vehicle performance and range without external charging.
Implementation Method 1
When they operate as electric generators, the electric machines convert a share of the kinetic energy of the motor vehicle into an electric current that becomes available to the battery
Implementation Method 2
Said electric current charges the high-voltage electric battery
Data Source
AI summary
A motor-vehicle, comprising a first and a second wheel, a third and a fourth wheel, a first and a second reversible electric machine connected to the first and second wheel; a third and a fourth reversible electric machine connected to the third and fourth wheel; and a rechargeable electrical power source; a control unit programmed to: process electrical power values available for the regenerative engine brake simulation based on the amount of electrical power still storable in the source and on first operating parameters of the motor vehicle; communicate said available power values to the respective first, second, third and fourth electric machine and receive, from them, values of a first, second, third and fourth torque available for the regenerative engine brake simulation associated with second parameters of the electric machines; and cause the first, second, third and fourth electric machine to implement a respective first, second, third and fourth braking torque acting upon the respective wheels.