Vehicle Brake Control for Smooth Regenerative Torque Handover
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Solution Overview
Problem
Existing brake systems in electric and hybrid vehicles exhibit unsteady braking behavior due to the lag time in initiating overrun regeneration torque, leading to uncomfortable driving experiences and potential overbraking.
Innovation Solution
A method for operating a brake system that initiates regenerative braking only after the difference between the actual drive torque and the setpoint overrun regeneration torque falls below a specified limit, ensuring smoother deceleration by synchronizing regenerative and overrun braking modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If regenerative braking is initiated immediately after detection of deceleration request, then energy recovery efficiency is improved, but braking stability deteriorates due to drive lag
Solution Approach 1:
The control unit delays the initiation of regenerative braking until the actual drive torque approaches the setpoint overrun regeneration torque. This preliminary waiting action allows the drive unit to first establish the baseline overrun torque, preventing the drive lag from causing unstable braking behavior while still enabling timely energy recovery.
Solution Approach 2:
The control unit continuously monitors the difference between actual drive torque and setpoint overrun regeneration torque, using this feedback to determine the optimal moment to initiate regenerative braking. When the difference falls below a threshold, regenerative braking is activated, ensuring stable and predictable braking behavior.
2Force
If overrun regeneration torque is set at drive unit, then deceleration force is improved, but response time deteriorates due to implementation lag
Solution Approach 1:
The drive unit is put into overrun mode first to establish the baseline deceleration force, and only after the actual drive torque approaches the setpoint value is regenerative braking initiated. This preliminary action ensures the drive unit is ready to provide stable deceleration force without delay.
Solution Approach 2:
The patent combines overrun regeneration and regenerative braking in a sequential manner, where overrun mode establishes the foundation and regenerative braking is added when conditions are optimal. This merging allows the system to achieve both immediate deceleration force and timely energy recovery.
3Power
If regenerative braking is activated without considering drive torque difference, then braking power is improved, but driving comfort deteriorates due to unsteady braking behavior
Solution Approach 1:
The control unit uses feedback from the torque difference between actual drive torque and setpoint overrun regeneration torque to determine when to activate regenerative braking. This feedback mechanism ensures that regenerative braking is activated at the optimal moment, providing smooth and predictable braking behavior that enhances driving comfort.
Solution Approach 2:
The system dynamically adjusts the timing of regenerative braking activation based on real-time torque conditions. By making the activation conditional on the torque difference threshold being met, the system adapts to the drive unit's response characteristics, ensuring smooth transitions and predictable braking behavior.
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
The method enhances the predictability and comfort of vehicle deceleration by preventing unsteady braking and overbraking, providing a smoother driving experience.
Implementation Method 1
the electric drive unit is operated as a generator. Some of the energy which is normally lost as frictional heat during braking can thus be fed in the form of electrical energy into an electrical energy storage device
Implementation Method 2
the friction brake can be called upon to decelerate the vehicle in addition to the regenerative braking
Data Source
AI summary
A method for operating a brake system of a vehicle, where the vehicle has an electric machine usable for a regenerative braking of the vehicle and a drive unit usable in an overrun operation for an overrun braking of the vehicle, includes detecting an initiation of deceleration of the vehicle and detecting a driving situation suitable for regeneration. The method further includes initiating the overrun operation of the drive unit and the overrun braking of the vehicle and activating the regenerative braking so as to achieve a setpoint total regeneration torque. The regenerative braking is activated only after a limit value for a difference between an actual overrun regeneration torque by the overrun braking and a setpoint overrun regeneration torque is undershot.