Disconnect Clutch Speed Synchronization for Smooth 4WD EV Engagement
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Solution Overview
Problem
Four-wheel drive electric vehicles experience increased driveline torque disturbances and reduced drivability when the driveline disconnect clutch decouples the electric machine, leading to potential wheel slip and loss of traction during transitions between different road surfaces.
Innovation Solution
A method for closing the driveline disconnect clutch in a four-wheel drive electric vehicle that involves a prescribed closing sequence with separate speed control phases, adjusting torque and rotational speed of the electric machine to synchronize the driveline without overshoot or undershoot, using distinct speed control phases and gain adjustments in a controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the driveline disconnect clutch is used to decouple the electric machine from the driveline, then vehicle efficiency is improved and driving range is extended, but driveline torque disturbances increase and drivability is degraded
Solution Approach 1:
The system performs preliminary speed synchronization of the electric machine to the driveline before closing the disconnect clutch. The controller monitors rotational speeds and adjusts the electric machine speed to match the driveline speed within a threshold range, ensuring smooth engagement and minimizing torque disturbances when the clutch is closed
Solution Approach 2:
The controller continuously monitors the rotational speed of the electric machine and the driveline, comparing these values to determine when speed synchronization has been achieved. This feedback mechanism allows the system to close the clutch at the optimal moment, reducing torque disturbances while maintaining efficiency
2Loss of time
If the driveline disconnect clutch is closed without speed synchronization, then the closing response is faster, but rotational speed differentials cause increased torque disturbances and wheel slip
Solution Approach 1:
The system performs preliminary speed synchronization of the electric machine to the driveline before closing the disconnect clutch. The controller monitors rotational speeds and adjusts the electric machine speed to match the driveline speed within a threshold range, ensuring smooth engagement and minimizing torque disturbances when the clutch is closed
Solution Approach 2:
The control system dynamically adjusts the electric machine speed based on real-time driveline conditions. The controller modifies the target speed profile during the synchronization phase to optimize both the speed matching accuracy and the timing of clutch closure, balancing speed synchronization quality with response time
Data Source
AI summary
Methods and system are described for closing a driveline disconnect clutch that selectively decouples an electric machine from wheels of a vehicle are described. In one example, closing of the driveline disconnect clutch is divided into three closing phases and one of the closing phases is divided into three speed phases to provide a desired level of driveline control.