eAWD Hybrid Mode Transition Control for Smooth Torque Handover
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electrically all-wheel drive (eAWD) hybrid vehicles experience torque disturbances and delays during mode transitions, particularly from electric-only to parallel modes, which can be noticeable to the driver due to unsynchronized engine and transmission speeds.
Innovation Solution
A control system and method that synchronizes engine and transmission speeds by depleting the torque reserve of the electric motor to provide expected acceleration, then transitions to engine-driven torque, optimizing drive torque distribution between axles to meet driver requests and recharge the battery system when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the vehicle operates in electric-only mode and then transitions to parallel mode, then the battery system can be recharged, but torque disturbances and delays occur during mode transition
Solution Approach 1:
The controller synchronizes engine and transmission speeds before the mode transition is completed, preparing the powertrain in advance to minimize torque disturbances. This preliminary synchronization ensures that when the transition occurs, torque delivery remains continuous without noticeable disruptions to the driver.
2Reliability
If the controller synchronizes engine and transmission speeds during mode transition, then torque disturbances are minimized, but transition time is extended
Solution Approach 1:
The controller dynamically adjusts torque distribution between the electric motor and engine during the transition process. By changing torque parameters in real-time and coordinating the depletion of electric motor torque reserve with engine torque buildup, the system achieves smooth transitions without excessive delay.
3Ease of operation
If the electric motor depletes torque reserve to provide expected acceleration feel, then driver acceleration expectation is met, but available torque for battery recharging is reduced
Solution Approach 1:
The controller maintains continuous useful action by coordinating the torque depletion of the electric motor with the simultaneous engagement and torque delivery of the engine. This ensures that acceleration feel is maintained throughout the transition while the engine begins charging the battery system, ensuring both driver expectation and energy recovery are achieved.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
Control techniques for an electrically all-wheel drive (eAWD) hybrid vehicle involve determining whether to transition from an electric-only mode to a parallel mode based on a driver torque request or a state of charge (SOC) of a battery system. During the electric-only mode, the electric motor is operated such that a torque reserve is maintained. When the driver torque request exceeds a maximum drive torque that the electric motor is capable of generating, the electric-only to parallel mode transition is performed. This involves the electric motor depleting the torque reserve to provide an expected acceleration feel for the driver while engine and transmission speeds are synchronized. When the SOC of the battery system falls below an SOC threshold, the drive torque of the electric motor is decreased to zero upon engine/transmission speed synchronization such that the battery system can be recharged.