Gear-Shift Control During Regenerative Braking Oversteer
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Solution Overview
Problem
Conventional hybrid vehicles face challenges in maintaining fuel efficiency while preventing oversteering in rear-wheel drive vehicles during regeneration operations, as reducing regeneration torque to address oversteering negatively impacts fuel efficiency and can lead to vehicle instability.
Innovation Solution
A vehicle gear-shifting control apparatus that adjusts the regeneration torque and interrupts motive power transmission between the input and output shafts of the automatic transmission to maintain regeneration while stabilizing the vehicle, preventing oversteering and ensuring fuel efficiency by dynamically controlling the gear-shifting points based on vehicle state and sensor inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the motor performs a regeneration operation during deceleration in a rear-wheel drive vehicle, then fuel efficiency is improved, but the lateral force of the rear wheels decreases causing the vehicle to fall into an oversteered state
Solution Approach 1:
The automatic transmission serves as an intermediary device between the motor and rear wheels. By controlling the transmission gear ratio during regeneration operation, the system can modify the torque delivery to the rear wheels, thereby maintaining lateral force while still enabling regenerative braking to improve fuel efficiency.
Solution Approach 2:
The system dynamically changes the transmission gear ratio parameter during regeneration operation. By selecting appropriate gear ratios, the control apparatus can adjust the torque characteristics delivered to the rear wheels, preventing oversteering while maintaining regeneration effectiveness for fuel efficiency improvement.
2Stability of the object's composition
If the regeneration operation is stopped when the vehicle falls into an oversteered state, then the oversteered state is resolved, but the fuel efficiency performance decreases
Solution Approach 1:
The system dynamically adjusts the transmission gear ratio in real-time during regeneration operation. Rather than simply stopping regeneration when oversteering occurs, the control apparatus continuously modifies the gear ratio to maintain vehicle stability while preserving the regeneration operation for fuel efficiency benefits.
Solution Approach 2:
The control apparatus monitors vehicle behavior and regeneration operation status, using this feedback to dynamically adjust the transmission gear ratio. This closed-loop control ensures that regeneration continues to improve fuel efficiency while vehicle stability is maintained through appropriate gear ratio selection.
3Speed
If the automatic transmission performs a downshift while the regeneration amount is reduced, then the rotation speed increases, but the torque of the rear wheels fluctuates due to the moment of inertia causing vehicle behavior to become unstable
Solution Approach 1:
The control apparatus performs preliminary assessment of vehicle state before allowing a downshift. By checking whether the vehicle is in an oversteered state or has unstable behavior, the system prevents downshifts that would cause torque fluctuations and instability, while still enabling downshifts when safe to improve rotation speed.
Solution Approach 2:
The system temporarily suspends the downshift operation when vehicle stability is compromised. Rather than forcing a downshift that would cause instability, the control apparatus delays the gear change until vehicle behavior stabilizes, prioritizing stability over immediate rotation speed increase.
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 solution effectively stabilizes the vehicle's behavior, maintains regeneration efficiency, and prevents engine stall by dynamically managing regeneration torque and gear shifts, thereby enhancing both stability and fuel efficiency during deceleration.
Implementation Method 1
a motor which generates another travel drive force of the vehicle and which supplies a battery with regenerative energy during deceleration of the vehicle
Implementation Method 2
an automatic transmission of which an input shaft is connected to the engine and the motor and an output shaft is connected to rear wheels and which subjects an input rotation to gear-shifting at a transmission gear ratio corresponding to a selected shift stage and outputs the gear-shifted input rotation
Implementation Method 3
a friction brake system which distributes a braking force to front wheels and the rear wheels in order to realize braking in accordance with a brake pedal operation by a driver
Data Source
AI summary
A vehicle gear-shifting control apparatus is equipped with an engine, a motor, an automatic transmission, a friction brake system, and a controller which executes, during deceleration during which the friction brake system is distributing a braking force to front and rear wheels, a regeneration control of imparting a regenerative braking torque to the rear wheels and a gear-shifting control of changing a shift stage of the automatic transmission by outputting a gear-shifting signal in accordance with the rotation speed of an input shaft to the transmission. When the controller determines an oversteered state of the vehicle during the regeneration control, the controller increases an input torque of the input shaft so that the regenerative braking torque decreases while maintaining the regeneration operation of the motor and, at the same time, interrupts motive power transmission between the input shaft and an output shaft of the transmission.