Regenerative Braking Torque Control for Yaw Stability
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Solution Overview
Problem
Existing regenerative braking systems in electrified vehicles face challenges in maintaining braking stability and efficient energy recuperation, particularly when independent torque control is applied to individual wheels, as excessive yaw moment can lead to instability and dynamic issues like spinning or drifting.
Innovation Solution
A vehicle regenerative braking system with a pair of electric machines, each coupled to a laterally-opposing wheel, uses a controller to command a combined regenerative braking torque output based on the lesser torque capability of each wheel, with a predetermined threshold to manage yaw rate, ensuring the torque is within a predetermined range to prevent excessive yaw moment and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If independent torque control is applied to individual wheels for regenerative braking, then braking responsiveness and energy recuperation are improved, but vehicle stability deteriorates due to excessive yaw moment
Solution Approach 1:
The system dynamically adjusts the regenerative braking torque parameters based on vehicle operating conditions. The controller monitors yaw rate and actively modifies the torque distribution between wheels, changing the torque magnitude and differential to maintain stability while preserving braking effectiveness. This parameter adaptation resolves the contradiction by allowing high torque application when stable and reducing torque differential when yaw becomes excessive.
2Loss of energy
If regenerative braking torque is maximized for energy recuperation, then energy recovery is improved, but braking stability deteriorates due to wheel slip and yaw
Solution Approach 1:
The controller implements feedback control by continuously monitoring wheel slip conditions, yaw rate, and braking torque application. When wheel slip or excessive yaw is detected, the controller adjusts the regenerative braking torque to prevent instability while maximizing energy recovery within safe operating limits. This feedback mechanism ensures energy recuperation is optimized without compromising braking reliability.
3Adaptability or versatility
If torque differential between wheels is increased for torque vectoring, then vehicle dynamics control is improved, but yaw stability deteriorates
Solution Approach 1:
The system dynamically adjusts the torque differential between wheels based on real-time vehicle state. The controller allows torque vectoring when beneficial for vehicle control but actively reduces or eliminates torque differential when yaw rate exceeds thresholds, maintaining yaw stability. This dynamic adjustment resolves the contradiction by adapting torque distribution to current vehicle dynamics conditions.
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 enhances regenerative braking responsiveness and energy recuperation while ensuring vehicle stability by proactively controlling the total regenerative braking torque and its allocation between wheels, preventing excessive yaw and improving overall braking performance.
Implementation Method 1
an electric machine for vehicle propulsion may have the ability to operate the electric machine as a generator during regenerative braking to recover energy
Data Source
AI summary
A vehicle includes a pair of electric machines each coupled to a laterally-opposing wheel to output a wheel torque. The vehicle also includes a controller programmed to command a combined regenerative braking torque output of the electric machines based on a lesser of a braking torque limit of each individual electric machine. The controller is also programmed to command a regenerative braking torque from each electric machine to be within a predetermined torque threshold of each other in response to a yaw rate exceeding a yaw threshold.