Vehicle Driving Force Control via D-μ Map Friction Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional four-wheel drive vehicles face challenges in accurately calculating the maximum road surface friction coefficient, which is crucial for optimal driving force distribution and fuel economy, especially in varying environments, due to the complexity of determining the friction circle reflecting the grip capacity of tires.
Innovation Solution
A driving force control method and system that utilize a D-μ map or formula to establish a linear correlation between driving stiffness and maximum road surface friction coefficient, allowing for accurate calculation of the maximum road surface friction coefficient based on slip ratio, enabling precise driving force control and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the friction circle corresponding to grip capacity of tires is used to determine slip possibility, then driving force distribution can be controlled, but the calculation of maximum road surface friction coefficient becomes complex and inaccurate in varying environments
Solution Approach 1:
The patent transforms the complex friction circle calculation into a simplified parameter-based approach by establishing a linear relationship between driving stiffness and maximum road surface friction coefficient. The control device calculates driving stiffness from readily available sensor data (wheel speeds, vehicle speed) and uses this to determine the maximum friction coefficient, avoiding complex environmental modeling while maintaining accuracy.
Solution Approach 2:
The patent replaces the mechanical/conceptual friction circle model with a computational approach based on driving stiffness calculation. Instead of modeling tire-road interaction physics directly, the system uses the relationship F=μ×W and calculates driving stiffness as the ratio of driving force to slip ratio, substituting complex mechanical analysis with straightforward mathematical computation.
2Reliability
If driving force is distributed early to subordinate wheels, then grip capacity is ensured, but fuel economy deteriorates due to increased drive loss
Solution Approach 1:
The patent implements feedback control by continuously monitoring driving stiffness and comparing it against thresholds to determine optimal driving force distribution. The system adjusts the engagement of the driving force distribution mechanism based on real-time calculation of maximum friction coefficient, ensuring grip capacity is maintained only when necessary while minimizing energy loss during two-wheel drive operation.
Solution Approach 2:
The patent employs dynamic adjustment of driving force distribution based on calculated driving stiffness. Rather than using fixed distribution strategies, the system adaptively modulates the coupling ratio of the driving force distribution mechanism according to real-time road surface conditions, allowing optimal balance between grip and fuel efficiency across varying operating conditions.
Data Source
AI summary
A driving force control device 1 for a vehicle V comprises: a D-μ map M1 defining a linear correlation between a driving stiffness D and a maximum road surface μ; a slip ratio calculation circuit 21 for calculating a slip ratio S of one of a pair of front road wheels 10L, 10R; a DS calculation circuit 22 for calculating the driving stiffness D corresponding to a value the slip ratio S calculated by the slip ratio calculation circuit 21; a maximum road surface μ calculation circuit 23 for assigning a value of the driving stiffness D calculated by the DS calculation circuit 22 to the D-μ map M1 to calculate the maximum road surface μ; and a driving force distribution circuit 24 for controlling a driving force, using a value of the maximum road surface μ calculated by the maximum road surface μ calculation circuit 23.