Vehicle Brake Regeneration Torque Limiting for Stability
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Solution Overview
Problem
In vehicles with hybrid or electric drives, the additional recuperation torque from the electric motor can cause overbraking of the rear axle, leading to loss of driving stability and increased pump and valve activities in the braking system, as conventional strategies often stop recuperation only when electronic brake force distribution control intervenes.
Innovation Solution
The method limits the recuperation torque on the rear axle to prevent slip exceeding a first threshold, and adjusts it based on slip detection, allowing for variable thresholds and dynamic changes in torque distribution between conventional and regenerative brakes to maintain optimal adhesion and reduce EBD interventions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the recuperation torque is increased to maximize energy recovery, then the energy recovery efficiency is improved, but the vehicle driving stability deteriorates due to overbraking of the rear axle
Solution Approach 1:
The patent dynamically adjusts the recuperation torque by changing the slip threshold parameter from a fixed value to a variable that adapts to different driving conditions. When the rear axle slip exceeds the threshold, the system reduces the recuperation torque to prevent overbraking, thus maintaining driving stability while still achieving energy recovery.
Solution Approach 2:
The patent implements a feedback control mechanism where the slip detection unit continuously monitors the slip of each wheel and provides this information to the control unit. The control unit then adjusts the recuperation torque based on the detected slip, creating a closed-loop control system that maintains driving stability while maximizing energy recovery.
2Stability of the object's composition
If the recuperation torque is limited to prevent overbraking, then the driving stability is improved, but the energy recovery efficiency deteriorates
Solution Approach 1:
The patent makes the slip threshold dynamic rather than fixed. The threshold is adjusted in real-time based on the detected slip and driving conditions, allowing the system to maximize energy recovery when conditions permit while preventing overbraking when slip exceeds the dynamic threshold. This dynamic approach resolves the contradiction by adapting the limitation to actual operating conditions.
Solution Approach 2:
The patent applies preliminary action by proactively limiting the recuperation torque before overbraking occurs. The slip detection and control mechanism prevents the rear axle from entering an overbraked state by adjusting the torque in advance, thus maintaining both stability and energy recovery efficiency without waiting for corrective intervention.
3Device complexity
If the conventional brake force distribution is used without slip-based recuperation torque adjustment, then the system complexity is reduced, but the frequency of EBD interventions increases
Solution Approach 1:
The patent introduces a slip-based parameter adjustment mechanism that modifies the recuperation torque based on detected wheel slip. This additional parameter control prevents excessive EBD interventions by proactively managing the braking force distribution, thus reducing the frequency of corrective EBD actions while maintaining acceptable system complexity.
4Stability of the object's composition
If the slip threshold is set low to prevent overbraking, then the driving stability is improved, but the adhesion utilization deteriorates
Solution Approach 1:
The patent makes the slip threshold dynamic rather than fixed at a low value. The threshold adapts to driving conditions, allowing higher values (better adhesion utilization) when conditions permit and lower values (better stability) when slip risk increases. This dynamic adjustment resolves the contradiction by optimizing both stability and adhesion utilization according to real-time 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 ensures stable vehicle operation by maintaining adhesion utilization, reducing the frequency of EBD interventions, and minimizing pump and valve activities, while allowing for effective energy recovery by redistributing torque between axles.
Implementation Method 1
the electric motor is operated as a generator during recuperation of braking energy and thereby exerts a braking recuperation torque on the respective axle
Implementation Method 2
This braking torque of the electric motor arises from the well-known regenerative effect of electric motors, which, when driven mechanically without the supply of electrical current, act as a dynamo or generator and generate electrical current. This creates a counterforce that counteracts the mechanical drive and, in this case, acts as a braking torque.
Data Source
Figure 1
Figure 2a~2b
Figure 3~4
AI summary
The present invention relates to a method for operating a vehicle brake system and a corresponding vehicle brake system, particularly for motor vehicles. The vehicle wheels of the motor vehicle associated with an axle are at least partially driven by an electric motor (16) that can be operated as a generator during regeneration of braking energy, thus exerting a braking regeneration torque on the respective axle. To prevent overbraking on the rear axle, the invention proposes that the regeneration torque acting on at least one rear axle (HA) be limited such that the slippage (20) present on the at least one vehicle wheel of said rear axle (HA) does not exceed or only negligibly exceeds a first slippage threshold (21) individually associated with said respective vehicle wheel.