Vehicle Torque Vectoring Control for Slippery Road Traction
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Solution Overview
Problem
Conventional torque vectoring devices struggle to ensure consistent driving force transmission to the road, especially on slippery surfaces, due to differential rotation between drive wheels, leading to reduced traction and stability.
Innovation Solution
A driving force control system with a differential mechanism, a differential motor, and a limited slip differential that allows for differential rotation control between wheels, using a controller to switch between differential and differential limit modes by gradually adjusting torque ratios and applying frictional braking to maintain traction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a torque vectoring device is used to vary torques delivered to each drive wheel, then turning performance is improved, but driving force transmission reliability deteriorates on slippery roads
Solution Approach 1:
The system dynamically switches between two operating modes: differential mode for normal conditions and differential limit mode for slippery conditions. The controller monitors wheel speed differences and automatically transitions between modes to optimize both turning performance and driving force transmission reliability based on real-time road conditions.
Solution Approach 2:
The system changes the torque distribution parameters by adjusting the differential limit torque value. In differential mode, the differential limit torque is set to allow free differential rotation for turning. In differential limit mode, the differential limit torque is increased to prevent wheel slip on slippery surfaces, thereby changing the system's torque distribution characteristics to match road conditions.
2Reliability
If differential rotation between drive wheels is limited to improve driving force transmission, then traction reliability is improved, but turning performance deteriorates
Solution Approach 1:
The system uses dynamic mode switching to adapt differential rotation limitation to actual driving conditions. The controller calculates wheel speed differences and automatically selects between differential mode (for turning) and differential limit mode (for traction), ensuring that turning performance is maintained when needed while traction reliability is improved when required.
Solution Approach 2:
The controller continuously monitors wheel speed signals from sensors and uses this feedback to determine the appropriate operating mode. By comparing the speed difference between drive wheels against predetermined thresholds, the system receives real-time feedback about driving conditions and adjusts the differential limit torque accordingly, balancing turning performance and traction reliability.
3Speed
If the operating mode is switched abruptly between differential mode and differential limit mode, then response speed is improved, but system stability deteriorates
Solution Approach 1:
The controller prepares for mode transitions by continuously monitoring wheel speed differences and pre-calculating the appropriate differential limit torque values. When a mode switch is needed, the system has already prepared the necessary control parameters, allowing for rapid yet stable transitions without abrupt changes that would destabilize the system.
Solution Approach 2:
The system uses dynamic control to smoothly manage mode transitions. The controller adjusts the differential limit torque gradually during transitions rather than making abrupt changes, maintaining system stability while still responding quickly to changing driving conditions. The dynamic adjustment ensures continuous and stable operation during mode switching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system ensures smooth shifting between operating modes, reduces backlash, and maintains stable driving force transmission, enhancing vehicle stability and traction on various road conditions.
Implementation Method 1
a limited slip differential that limits the differential rotation between the right wheel and the left wheel by applying a frictional braking force to a rotary member between the differential motor and the limited slip differential thereby applying differential limit torque to the rotary member
Data Source
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AI summary
The invention relates to driving force control system for a vehicle (Ve) comprising a differential mechanism (7, 14), a differential motor (10, 17) allowing torque vectorinbg between the right and left wheel coupled to the differential (7, 14), and a frictiopn brake (8) to provide a limited slip funtion. To avoid a shock during mode change, a controller (51) equalizes the torques applied by the motor (10) and the brake (8). This is done by gradually reducing the difference between these torques.