Regenerative Braking Disengagement Thresholds
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Solution Overview
Problem
Vehicle brake systems that offer both frictional and regenerative braking capabilities often prematurely cancel regenerative braking operations when sensing potential instability, leading to reduced fuel economy, increased wear on frictional components, and loss of deceleration.
Innovation Solution
A method that determines wheel slip and compares it to speed-based thresholds to differentiate between situations warranting disengagement of regenerative braking and those that do not, using individual and collective wheel slip evaluations to minimize unnecessary disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If regenerative braking operations are cancelled immediately when wheel slippage is detected, then vehicle stability is maintained, but fuel economy is reduced and frictional braking components experience increased wear
Solution Approach 1:
The patent applies parameter changes by using speed-based thresholds that vary according to vehicle speed to determine when to disengage regenerative braking. Instead of using a fixed threshold, the system adjusts the wheel slip threshold dynamically based on the current speed, allowing for more nuanced decision-making that preserves regenerative braking in low-speed scenarios while maintaining stability at higher speeds.
Solution Approach 2:
The patent implements partial action by evaluating wheel slip against speed-based thresholds to determine the appropriate level of regenerative braking disengagement. Rather than immediately and completely cancelling regenerative braking upon detecting any wheel slip, the system partially maintains regenerative braking when slip remains below the speed-based threshold, thereby reducing unnecessary energy loss while still responding to stability concerns.
2Reliability
If regenerative braking is cancelled immediately upon wheel slippage detection, then vehicle stability is maintained, but wear on frictional braking components increases
Solution Approach 1:
The system uses speed-based parameter changes to dynamically adjust the wheel slip threshold, allowing regenerative braking to continue in low-speed conditions where minor slip is normal, thereby reducing unnecessary frictional braking engagement and component wear.
Solution Approach 2:
By implementing partial disengagement based on threshold comparisons, the system avoids complete and immediate cancellation of regenerative braking, thereby minimizing unnecessary frictional braking usage and reducing wear on frictional components.
3Reliability
If regenerative braking is cancelled immediately upon wheel slippage detection, then vehicle stability is maintained, but deceleration performance is reduced
Solution Approach 1:
The patent uses speed-based threshold adjustments to optimize the balance between stability and deceleration performance. By changing the threshold parameter according to vehicle speed, the system allows regenerative braking to continue in scenarios where deceleration is still effective, thereby maintaining better deceleration performance while preserving stability.
Solution Approach 2:
The system applies partial disengagement of regenerative braking based on threshold comparisons, maintaining regenerative braking contribution to deceleration in appropriate conditions while still responding to stability concerns, thereby optimizing overall deceleration performance.
Data Source
AI summary
A method for operating a vehicle brake system having both frictional and regenerative braking capabilities. According to one embodiment, the method monitors wheel slip at a number of vehicle wheels, evaluates individual wheel slip at a single wheel as well as collective wheel slip involving multiple wheels, compares the wheel slips to one or more speed-based thresholds that are based on vehicle speed, and uses the comparisons to help distinguish between those situations that warrant disengagement of regenerative braking operations and those that do not.