Regenerative Braking Torque Control for Vehicle Stability
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Solution Overview
Problem
Existing regenerative braking systems in electric vehicles face challenges in maintaining vehicle stability during braking maneuvers, particularly in avoiding excessive rear wheel braking, which can lead to instability.
Innovation Solution
A method that senses steering wheel angle, vehicle speed, brake pedal position, and wheel slips to determine commanded lateral acceleration, allowing controlled application of regenerative brake torque based on predetermined slip limits to prevent brake instability, by maintaining constant regenerative brake torque when rear wheel slip exceeds certain limits relative to front wheel slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking torque is increased to maximize energy recovery, then energy efficiency is improved, but vehicle stability deteriorates due to rear wheel over-braking
Solution Approach 1:
The system dynamically adjusts the regenerative braking torque by changing the slip limit parameter based on commanded lateral acceleration. As lateral acceleration increases during cornering, the slip limit decreases, which reduces the regenerative braking torque applied to rear wheels, thereby maintaining vehicle stability while still recovering energy
Solution Approach 2:
The patent implements a dynamic control system that continuously monitors steering wheel angle and vehicle speed to calculate commanded lateral acceleration, which then dynamically adjusts the rear wheel slip limits for regenerative braking. This dynamic adjustment prevents rear wheel over-braking during cornering maneuvers while maximizing energy recovery during stable braking conditions
2Duration of action of moving object
If regenerative braking is applied during cornering to extend driving range, then driving range is improved, but vehicle stability deteriorates due to excessive rear wheel slip
Solution Approach 1:
The system changes the slip limit parameter based on commanded lateral acceleration calculated from steering wheel angle and vehicle speed. During cornering when lateral acceleration is high, the slip limit is reduced, which limits regenerative braking torque and prevents excessive rear wheel slip, maintaining vehicle stability while still allowing energy recovery
Solution Approach 2:
The control system uses feedback from steering wheel angle sensors and vehicle speed sensors to continuously calculate commanded lateral acceleration, which then feeds back to adjust the slip limits for regenerative braking. This closed-loop feedback mechanism ensures that regenerative braking is modulated appropriately during cornering maneuvers to maintain stability
Data Source
AI summary
The present disclosure relates to a method for controlling an application of regenerative brake torque to a plurality of wheels of at least one of a hybrid electric vehicle or an electric vehicle, to avoid brake instability. The method may involve sensing variables such as an angle of a steering wheel of the vehicle, a speed of the vehicle, a brake pedal rate as an operator engages a brake pedal, and a wheel slip of each of the front and rear wheels. A commanded lateral acceleration may be determined representing a steady state lateral acceleration that the vehicle would reach at an actual vehicle speed and with a presently sensed steering wheel angle. The application of regenerative brake torque can then be controlled based on the sensed wheel slips relative to at least one predetermined wheel slip limit. The predetermined wheel slip limit is determined based at least in part on the determined commanded lateral acceleration.