Active Torque Distribution via ELSD for Vehicle Stability
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Solution Overview
Problem
Existing vehicle stability control systems, particularly those based on brake intervention, face limitations in maintaining longitudinal motion on split-friction surfaces and degrade lateral dynamics, while brake-based systems compromise speed performance and conflict with driver intentions.
Innovation Solution
An active vehicle stability control system using electronically controlled limited-slip differentials (ELSDs) that distributes torque between wheels, engaging the differential based on vehicle operating parameters and yaw rate differences to enhance lateral dynamics while preserving longitudinal motion, incorporating a stability-enhanced traction controller and yaw damping controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If brake-based stability control systems are used to correct vehicle yaw dynamics, then vehicle stability is improved, but speed performance deteriorates and conflicts with driver actions
Solution Approach 1:
The patent replaces the brake-based mechanical stability control system with an active torque distribution system that uses the electronically controlled limited-slip differential to generate corrective yaw moments. Instead of applying braking forces to wheels, the system modulates torque delivery to the driven wheels through the ELSD, achieving stability control without the speed-limiting effects of brake intervention.
Solution Approach 2:
The ELSD acts as an intermediary device between the powertrain and the wheels, enabling torque redistribution to achieve both traction control and stability control functions. The differential apparatus mediates the torque flow to generate yaw-damping effects without directly interfering with the driver's acceleration inputs through brake application.
2Force
If fully locked differentials are used to achieve best longitudinal traction, then longitudinal motion is improved, but lateral dynamics are degraded and deviate from driver intended direction
Solution Approach 1:
The system dynamically adjusts the torque distribution through the ELSD based on real-time vehicle operating conditions, including yaw rate feedback. Rather than maintaining a fixed locked state, the differential engagement is modulated to provide traction when needed while allowing sufficient slip to maintain lateral stability and respond to driver steering inputs.
Solution Approach 2:
The stability controller uses feedback from the yaw rate sensor to continuously monitor vehicle rotational motion and adjusts the ELSD torque distribution accordingly. When undesired yaw motion is detected, the system modifies differential engagement to generate corrective moments, preventing lateral dynamics degradation while maintaining longitudinal traction.
3Force
If brake intervention is used for traction control on split-friction surfaces, then traction is improved, but energy is dissipated equal to that spent in biasing the high-friction wheel
Solution Approach 1:
The patent replaces the brake-based traction control mechanism with an ELSD-based torque distribution system. Instead of using brake forces to prevent wheel spin, the system uses the limited-slip differential to actively manage torque delivery to each wheel, reducing energy dissipation while maintaining effective traction on split-friction surfaces.
Data Source
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AI summary
A control system (50) for a vehicle having first and second wheels (28, 30) is provided that includes a differential apparatus (22) adapted to distribute torque between the first and second wheels (28, 30) and a traction controller (52) for controlling operation of the differential apparatus (22) from vehicle launch up to a predetermined vehicle speed. The traction controller (52) is configured to engage the differential apparatus (22) in a first operating state according to at least one vehicle operating parameter indicative of a low traction operating condition and to further control engagement of the differential apparatus (22) in a second vehicle operating state during the low traction operating condition according to a difference between an actual vehicle yaw rate and a predetermined target vehicle yaw rate. The control system (50) also includes a stability controller (54) for controlling engagement of the differential apparatus (22) at or above the predetermined vehicle speed.