Super Positioning Torque Vectoring Differential Speed Control
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Solution Overview
Problem
Conventional torque vectoring differentials in vehicles face challenges in effectively managing wheel speed differences and handling during various driving conditions, particularly on split-μ surfaces and during cornering, where the tire with least traction receives most driving torque, limiting vehicle acceleration and handling.
Innovation Solution
A super positioning torque vectoring differential system that includes a controller operating in speed control mode to reduce wheel speed differences and switch to torque control mode based on vehicle acceleration and driver input, utilizing a combination of traction and vectoring motors to actively control wheel speed differences, with a closed-loop control system incorporating feedforward and feedback algorithms to achieve target wheel speed and yaw rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional torque vectoring differential is used, then torque can be varied to each wheel to improve launch and handling, but the tire with least traction receives most driving torque which limits vehicle acceleration
Solution Approach 1:
The system dynamically switches between torque control mode and speed control mode based on real-time wheel speed difference detection. When wheel speed difference exceeds a threshold, the system transitions to speed control mode to prevent the low-traction tire from receiving excessive torque, thereby resolving the contradiction between improving acceleration and controlling torque distribution.
Solution Approach 2:
The controller changes the control parameter from torque-based control to speed-based control when wheel speed difference exceeds the threshold. This parameter change allows the system to prioritize speed equalization over torque distribution, preventing loss of acceleration while maintaining controlled torque distribution.
2Speed
If speed control mode is implemented to reduce wheel speed difference, then wheel speed control is improved, but system complexity increases
Solution Approach 1:
The control system is segmented into two distinct modes: torque control mode for normal operation and speed control mode for when wheel speed difference exceeds threshold. This segmentation allows the system to implement complex speed control functionality only when needed, reducing overall system complexity while maintaining improved wheel speed control capability.
Solution Approach 2:
The system automatically detects wheel speed difference and self-regulates by switching between control modes without requiring external intervention. The controller monitors wheel speeds and autonomously transitions between torque control and speed control modes, simplifying the user interface while maintaining complex control functionality.
3Adaptability or versatility
If torque control mode is used during turning, then torque distribution is optimized for cornering, but wheel speed difference management is limited
Solution Approach 1:
The system dynamically transitions from torque control mode to speed control mode during turning when wheel speed difference exceeds the threshold. This dynamic adaptation allows the system to maintain optimized torque distribution for cornering while simultaneously managing wheel speed differences when they become excessive, combining the benefits of both control strategies.
Data Source
AI summary
An electrified axle system includes a pair of wheels, a super positioning torque vectoring differential coupled between the wheels, and a controller. The super positioning torque vectoring differential includes a traction motor and a vectoring motor. The controller operates the vectoring motor in speed control mode to reduce a speed difference between the wheels responsive to the difference exceeding a threshold, and operates the vectoring motor in torque control mode responsive to the difference falling within a target range and an accelerator pedal position achieving a value that depends on lateral acceleration associated with the system.