Regenerative Braking Torque Normalization via Friction Compensation
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Solution Overview
Problem
In hybrid and electric vehicles, the reduction or unavailability of regenerative braking torque leads to less than expected deceleration, especially when the energy storage system is fully charged or during wheel slip conditions, and in vehicles with dual dry clutch transmissions, deceleration from the driveline may be unavailable, resulting in a loss of normal coastdown deceleration.
Innovation Solution
A vehicle control system that determines the regenerative torque capacity and coastdown torque capability, calculates the desired torque amounts, and detects when these exceed a threshold, subsequently controlling the actuation of the friction braking system to compensate for the lack of regenerative torque and maintain consistent deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking torque is used to recharge the battery, then energy recovery efficiency is improved, but deceleration availability deteriorates when the energy storage system is fully charged
Solution Approach 1:
The system dynamically switches between regenerative braking mode and friction braking mode based on real-time battery state of charge conditions. When the battery is fully charged, the system transitions from regenerative braking to friction braking, allowing the braking mechanism to adapt its operation according to changing energy storage conditions and maintain consistent deceleration performance.
2Stability of the object's composition
If friction brakes are used to provide deceleration, then deceleration consistency is improved, but energy recovery capability deteriorates
Solution Approach 1:
The control system dynamically determines the optimal braking mode by monitoring battery state of charge. When battery charge level allows, regenerative braking is activated for energy recovery; when the battery is fully charged, friction braking is engaged to ensure deceleration consistency. This dynamic switching strategy optimizes both energy recovery and deceleration performance under different operating conditions.
3Reliability
If regenerative torque is inhibited during transmission shifting, then transmission reliability is improved, but vehicle deceleration performance deteriorates
Solution Approach 1:
The system applies friction braking in advance during transmission shifting operations to compensate for the inhibition of regenerative torque. By proactively engaging the friction braking mechanism when shifting is detected, the system maintains vehicle deceleration performance throughout the shifting process, preventing the deceleration drop that would otherwise occur when regenerative torque is temporarily disabled.
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 system ensures consistent and predictable vehicle deceleration by activating the friction braking system to compensate for the loss of regenerative braking torque, maintaining normal deceleration experiences for the driver and improving vehicle dynamics.
Implementation Method 1
a friction braking system for the road wheel
Implementation Method 2
an electric motor/generator mechanically coupled to the road wheel and electrically coupled to the energy storage system
Data Source
AI summary
A method of operating a vehicle having a friction braking system and a regenerative braking system is presented here. The method determines a regenerative torque capacity, calculates a desired regenerative torque amount for the braking system, detects that the desired regenerative torque amount exceeds the regenerative torque capacity by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting. Another operating method determines a coastdown torque capability of the vehicle, calculates a desired coastdown torque amount, detects that the desired coastdown torque amount exceeds the coastdown torque capability by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting.