Gear-Shift Torque Control for Oversteer During Regenerative Downshifts
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Solution Overview
Problem
Rear-wheel drive vehicles experience oversteering issues during regeneration operations, leading to decreased fuel efficiency and instability, as the regenerative braking torque primarily affects the rear wheels.
Innovation Solution
A vehicle gear-shifting control apparatus that includes an engine, a motor, an automatic transmission, a friction brake system, and a controller. The controller manages regeneration control and gear-shifting by adjusting the input torque of the automatic transmission to balance regenerative braking torque and maintain vehicle stability during downshifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the motor performs a regeneration operation during deceleration, then fuel efficiency performance is improved, but the lateral force of the rear wheels decreases causing the vehicle to fall into an oversteered state
Solution Approach 1:
The control apparatus dynamically adjusts the regenerative braking torque as a controllable parameter based on vehicle state (straight running vs. turning). During straight running, maximum regenerative torque is applied to improve fuel efficiency. During turning, the regenerative torque is reduced or suspended to maintain adequate lateral force and prevent oversteering. This parameter-based control resolves the contradiction by adapting the regeneration level to operational context.
Solution Approach 2:
The system transitions from a static regeneration mode to a dynamic control mode that continuously monitors vehicle state (steering angle, lateral acceleration) and adjusts regenerative braking torque in real-time. The control apparatus dynamically switches between different regeneration strategies (full regeneration, reduced regeneration, or suspended regeneration) based on whether the vehicle is in a straight-running or turning state, thereby maintaining both fuel efficiency and behavioral stability.
2Stability of the object's composition
If the regeneration operation is stopped to resolve the oversteered state, then vehicle stability is improved, but fuel efficiency performance decreases
Solution Approach 1:
Instead of completely stopping regeneration to resolve oversteering, the control apparatus applies partial regenerative braking torque during turning operations. The regenerative torque is reduced to a level that maintains sufficient lateral force for stability while still providing some energy recovery. This partial action approach resolves the contradiction by achieving adequate stability improvement without fully sacrificing fuel efficiency benefits.
Solution Approach 2:
The system implements dynamic regulation of regenerative braking torque rather than binary on/off control. During turning, the torque is modulated to an appropriate level that prevents oversteering while maintaining partial regeneration. This dynamic adjustment resolves the contradiction by finding an optimal intermediate state that balances stability requirements with energy recovery objectives.
3Ease of operation
If the automatic transmission performs a downshift during an oversteered state, then gear-shifting control is executed, but the torque fluctuation destabilizes the vehicle behavior
Solution Approach 1:
The control apparatus detects the oversteered state in advance and preemptively suspends or reduces regenerative braking torque before executing a downshift during turning. By applying preliminary anti-action (reducing the destabilizing regenerative torque) before the downshift occurs, the system prevents the torque fluctuation from causing further behavioral instability. This resolves the contradiction by preparing the system in advance to accommodate the upcoming gear change safely.
Solution Approach 2:
Before executing a downshift during an oversteered state, the control apparatus performs preliminary actions by adjusting the regenerative braking torque to an appropriate level. This preliminary adjustment ensures that the torque fluctuation during downshift will not exacerbate the oversteering condition. By taking preliminary action, the system resolves the contradiction between executing gear-shifting control and maintaining behavioral stability.
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 effectively suppresses oversteering while maintaining regeneration efficiency, ensuring both stability and improved fuel efficiency by dynamically adjusting the regenerative braking torque and input torque during gear shifts.
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 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 regeneration control and gear-shifting control during deceleration of the vehicle with a braking force to front and rear wheels. The controller increases an input torque of an input shaft according to a downshift so that an accompanying acceleration fluctuation equals a target acceleration fluctuation. When the controller determines an oversteered state during the regeneration control and during a downshift, the controller increases the input torque so that a regenerative braking torque decreases while maintaining a regeneration operation of the motor and, at the same time, the controller causes the automatic transmission to perform the downshift in a state where an amount of increase of the input torque in accordance with the downshift has been increased compared to during a non-determination of the oversteered state.