Axle Torque Distribution via Lateral Force Constraints
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Solution Overview
Problem
Achieving optimal vehicle lateral performance in limit-handling scenarios is challenging due to uncertainties in road conditions and conflicting sensor data, leading to inefficient torque distribution between axles, which can result in understeer, oversteer, or loss of traction.
Innovation Solution
An axle torque distribution system that uses a control module to determine steering angle, lateral forces, and torque capacities based on tire capacities, redistributing torque between the front and rear axles to maximize lateral forces and maintain yaw moment equilibrium, while limiting forces to prevent saturation and ensure maximum grip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque is distributed between axles based on traditional control methods, then the vehicle can maintain basic stability, but lateral performance is suboptimal in limit-handling scenarios due to uncertainties in road conditions and conflicting sensor data
Solution Approach 1:
The torque distribution system dynamically adjusts torque allocation between axles based on real-time vehicle state parameters (steering angle, slip angles, longitudinal velocity, yaw rate) to optimize lateral performance in limit-handling scenarios. The control module continuously recalculates torque capacities and redistributes torque to maximize tire grip while maintaining stability, adapting to changing road conditions and vehicle dynamics.
2Force
If torque is increased to one axle to improve lateral grip, then lateral forces are maximized, but the other axle may become saturated leading to understeer or oversteer
Solution Approach 1:
The system calculates torque capacities for each axle based on tire friction coefficients, normal forces, and current longitudinal forces. By continuously monitoring and adjusting these parameters, the control module determines optimal lateral force distribution that maximizes grip while preventing saturation. The available longitudinal capacity is recalculated based on lateral force requests, and torque is redistributed to maintain yaw moment equilibrium and prevent understeer or oversteer conditions.
3Speed
If torque distribution is optimized for maximum lateral forces, then corner-exiting speeds can be increased, but the system complexity increases due to multiple sensor inputs and control calculations
Solution Approach 1:
The control module serves multiple functions: it processes steering angle input, calculates lateral acceleration requests, determines slip angles, computes torque capacities for each axle, and executes torque redistribution. This multi-functional approach consolidates complex control operations into a single integrated system that optimizes lateral performance while managing vehicle stability and preventing saturation across multiple operating conditions.
Data Source
AI summary
An axle torque distribution system includes a memory and a control module. The memory stores a steering angle and a toque distribution algorithm. The control module executes the torque distribution algorithm to: obtain the steering angle; based on the steering angle, determine total lateral force requested for axles of a vehicle; based on the total lateral force requested, determine lateral forces requested for the axles while constraining lateral force distribution between the axles, where the constraining of the lateral force distribution includes, based on maximum lateral force capacities of tires of the vehicle, limiting the lateral forces requested for the axles; determine available longitudinal capacities for the axles based on the lateral forces requested respectively for the axles; determine torque capacities of the axles based on the lateral forces requested respectively for the axles; and control distribution of torque to the axles based on the torque capacities of the axles.