Dual-Motor Drivetrain Torque Coordination for Clunk and Shuffle
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Solution Overview
Problem
Existing drivetrain systems in electric vehicles face challenges in managing clunk and shuffle phenomena due to backlash and compliance, especially in dual motor vehicles with separate drivetrains, where differing backlash and compliance levels between axles contribute to these issues.
Innovation Solution
A system comprising a first prime mover for the front axle and a second prime mover for the rear axle, with a controller that coordinates torque shaping to command the axles to cross lash zones sequentially, compensating for one axle's lash using the other axle's prime mover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If torque shaping is applied to minimize clunk in dual motor vehicles, then clunk reduction is achieved, but coordinating torque between separate drivetrains becomes challenging
Solution Approach 1:
The patent merges the control of two separate drivetrains under a unified coordination strategy. The controller integrates torque shaping commands for both front and rear motors, synchronizing their lash zone crossings to minimize clunk. This combines previously independent control systems into a coordinated whole, addressing the complexity challenge while achieving clunk reduction.
Solution Approach 2:
The controller performs preliminary torque shaping before the drivetrain crosses the lash zone. By anticipating the lash crossing event and pre-adjusting torque commands for both motors, the system minimizes clunk generation. This preliminary action allows smooth traversal through the lash zone without abrupt torque changes that would cause clunk.
2Adaptability or versatility
If wheel-end disconnect hub is equipped on one axle, then drivetrain flexibility is improved, but backlash increases
Solution Approach 1:
The patent applies different control strategies to different axles based on their specific characteristics. The axle with the wheel-end disconnect hub receives tailored torque shaping commands that account for its larger backlash. This local quality approach allows the system to optimize for both flexibility and stability by treating each axle according to its individual properties.
Solution Approach 2:
The controller dynamically adjusts torque parameters for the axle with the disconnect hub to compensate for increased backlash. By changing torque magnitude and rate-of-change parameters in response to detected lash zone conditions, the system maintains stable operation despite the flexibility-induced backlash variations.
3Speed
If torque is increased rapidly in response to accelerator pedal input, then acceleration response is improved, but clunk and shuffle phenomena occur
Solution Approach 1:
The controller performs preliminary torque shaping before rapid acceleration occurs. When accelerator pedal input is detected, the system pre-adjusts torque commands to navigate through the lash zone smoothly before applying full acceleration torque. This preliminary action eliminates clunk and shuffle while preserving the overall acceleration response.
Solution Approach 2:
The patent implements dynamic torque adjustment based on real-time drivetrain conditions. The controller continuously monitors lash zone proximity and adapts torque rate-of-change accordingly. This dynamic approach allows rapid acceleration when conditions permit while preventing clunk and shuffle when the drivetrain is near the lash zone.
Data Source
AI summary
Methods and systems are provided for a drivetrain system comprising: a first prime mover for supplying a torque to a front axle; a second prime mover for supplying a torque to a rear axle; and a controller configured to, in response to a torque reversal, command the front axle and the rear axle to cross lash zones sequentially.