Axle Assembly Shift Control for Rotor-Clutch Synchronization
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Solution Overview
Problem
Existing drive axle systems with electric motors face challenges in smoothly transitioning between gear ratios due to synchronization issues between the rotor speed and clutch speed, leading to potential unintended acceleration or deceleration when the clutch engages with the gears.
Innovation Solution
A method is implemented that includes a speed synchronization mode to adjust the rotor speed to match the clutch speed without altering the torque output, and a low torque synchronization mode to limit motor torque if initial synchronization is not achieved within predetermined time frames, ensuring safe and efficient gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotor speed is adjusted rapidly to match clutch speed during gear shifting, then the responsiveness of the axle assembly is improved, but unintended acceleration or deceleration may occur when the clutch engages with the gears
Solution Approach 1:
The system dynamically changes the torque output parameter of the electric motor based on the gear shifting state. During speed synchronization mode, full torque is maintained to enable rapid rotor speed adjustment. When the clutch approaches engagement, the controller reduces torque to prevent unintended acceleration, thus resolving the contradiction between responsiveness and stability
Solution Approach 2:
The controller continuously monitors the rotational speed difference between the rotor and clutch, and adjusts the motor torque accordingly. When the speed difference falls within a predetermined range indicating imminent engagement, the controller provides feedback to reduce torque output, preventing instability while maintaining rapid response capability
2Reliability
If the torque output is limited during synchronization to prevent unintended acceleration, then the stability during gear shifting is improved, but the responsiveness of the axle assembly deteriorates
Solution Approach 1:
The system dynamically adjusts torque output based on the real-time synchronization state. During most of the synchronization process, full torque is applied for rapid speed matching. Only when the speed difference enters a critical threshold range does the system reduce torque, creating a dynamic response that maintains both stability and responsiveness
3Adaptability or versatility
If multiple synchronization modes are implemented to handle different gear shifting scenarios, then the adaptability of the system is improved, but the device complexity increases
Solution Approach 1:
The synchronization process is segmented into distinct modes: speed synchronization mode for normal operations and low torque synchronization mode for critical engagement phases. Each mode has specific torque control characteristics, allowing the system to adapt to different scenarios while maintaining manageable control logic through clear mode transitions
Data Source
AI summary
A method of controlling an axle assembly. The method includes executing a speed synchronization mode and operating a clutch actuator to shift a clutch from a neutral position toward an engaged position. The method may also include executing a low torque synchronization mode when the clutch cannot be shifted from a neutral position to an engaged position within a first predetermined period of time.