EV Driveline Disconnect Shift Sequencing for Predictable 4WD Engagement
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Solution Overview
Problem
In electric four-wheel drive vehicles, the randomness of left versus right wheel connection during shifting between two-wheel and four-wheel drive configurations is undesirable due to sophisticated control systems and sensors, which traditional simultaneous shifting does not address.
Innovation Solution
Implementing a sequential and overlapping shift process for driveline actuators, where one wheel disconnect is initiated first, followed by the second after a controlled time delay, ensuring predictable engagement order and minimizing overall shift time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If simultaneous shifting of left and right wheel disconnects is used, then the shifting process is simple to implement, but the engagement order becomes random which is undesirable in electric vehicles with sophisticated control systems
Solution Approach 1:
The simultaneous shifting operation is segmented into two separate sequential operations. The left wheel disconnect is actuated first, then the right wheel disconnect is actuated after a predetermined time delay. This segmentation eliminates the randomness of engagement order while maintaining systematic control, directly resolving the contradiction between operational simplicity and engagement predictability.
2Reliability
If sequential shifting with time delay is implemented, then engagement order predictability is improved, but the total shifting time increases
Solution Approach 1:
The control system initiates the left wheel disconnect actuation first as a preliminary action, then after a predetermined time delay (shorter than the total shifting time), initiates the right wheel disconnect actuation. This preliminary sequencing ensures predictable engagement order while the optimized time delay minimizes total shifting duration, resolving the contradiction between reliability and time loss.
3Device complexity
If traditional simultaneous shifting is used in internal combustion engine vehicles, then the control system complexity is reduced, but the randomness of connection order cannot be controlled
Solution Approach 1:
The control system dynamically adjusts the actuation timing of wheel disconnects based on vehicle type. For electric vehicles, it implements sequential actuation with predetermined time delays to ensure predictable engagement order. For internal combustion engine vehicles, it can revert to simultaneous actuation. This dynamic adaptability resolves the contradiction between control system complexity and connection order control by optimizing the approach for each vehicle type.
Data Source
AI summary
In general, this disclosure relates to a system and method of control for driveline actuators (DLAs) in the powertrain of an electric vehicle to perform shifting between two-wheel drive (2WD) and four-wheel drive (4WD) configurations. Sequential and overlapping shift process is used. The first disconnect is instructed by a vehicle control system to begin its shift, which takes approximately 100 milliseconds to complete. A short period of time after the first disconnect is instructed to begin its shift, but before it has completed the shift, the second disconnect is instructed to begin.