Regenerative Braking Torque Scheduling for Hybrid Vehicle Drivability
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Solution Overview
Problem
Hybrid vehicles with electric motors experience unacceptable drivability due to uncontrolled transient characteristics of regenerative braking, particularly in vehicles without transmission or clutch, leading to excessive negative torque application that impairs smooth deceleration and power generation.
Innovation Solution
A method and system for scheduling regenerative braking torque by sensing the accelerator pedal position, determining a torque limit based on motor/generator speed, and generating a regenerative braking command to limit negative torque application, thereby controlling the conversion of kinetic energy into electrical energy for storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking torque is not limited, then energy recovery efficiency is improved, but drivability deteriorates due to excessive negative torque application
Solution Approach 1:
The patent implements dynamic torque scheduling that adjusts regenerative braking torque limits based on real-time operating conditions including motor speed, accelerator pedal position, and brake pedal status. This dynamic adjustment allows the system to optimize energy recovery while maintaining smooth deceleration characteristics across different driving scenarios.
Solution Approach 2:
The system changes torque parameter limits based on operating conditions. Specifically, it applies different torque thresholds depending on motor speed ranges and pedal positions, allowing aggressive torque recovery at high speeds while limiting torque at low speeds to prevent drivability issues.
2Speed
If electric motor provides fast response for acceleration, then drivability is improved, but uncontrolled transient characteristics during regenerative braking cause unacceptable drivability
Solution Approach 1:
The system applies preliminary anti-action by preemptively limiting negative torque before excessive regenerative braking can occur. When the accelerator pedal is released, the controller immediately applies torque limits based on current operating conditions to prevent the electric motor from generating excessive negative torque that would cause drivability issues.
Solution Approach 2:
The system uses feedback from accelerator pedal position sensors, brake pedal sensors, and motor speed sensors to continuously monitor operating conditions and adjust regenerative braking torque in real-time, ensuring smooth transient response during deceleration events.
3Ease of operation
If regenerative braking torque is limited to ensure smooth deceleration, then drivability is improved, but energy recovery efficiency decreases
Solution Approach 1:
The system dynamically adjusts torque limits based on motor speed, applying more aggressive regenerative braking at higher speeds where energy recovery potential is greater, while applying stricter limits at lower speeds where drivability concerns dominate. This dynamic approach optimizes the trade-off between energy recovery and smooth deceleration.
Solution Approach 2:
The system applies partial regenerative braking torque rather than full torque in certain conditions. By applying controlled amounts of negative torque rather than maximum possible torque, the system recovers a significant portion of energy while maintaining acceptable drivability, accepting that not all available energy can be recovered in every scenario.
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 improves drivability by limiting excessive negative torque, balancing power generation and smooth deceleration, ensuring acceptable drivability while allowing for efficient energy storage during regenerative braking.
Implementation Method 1
converting kinetic energy from regenerative braking into electrical energy
Data Source
AI summary
A method is provided for scheduling regenerative braking torque, comprising: sensing a position of an accelerator pedal; generating a torque request value in response to the sensed accelerator pedal position; determining a speed of operation of a motor/generator; determining a torque limit in response to the torque request value and the determined speed of the motor/generator; generating a regenerative braking command in response to the torque limit; and outputting the regenerative braking command to the motor/generator.