Braking Force Control System for Split-μ Road Stability
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Solution Overview
Problem
Existing vehicle braking force control systems are unstable when tire characteristics differ between wheels or when driving on split μ roads, leading to unintended vehicle deflection and instability.
Innovation Solution
A braking force control system that individually adjusts wheel braking forces to equalize slip conditions between right and left wheels by setting an upper limit for braking force deviation, prohibiting increases at outer wheels during turns and reducing braking forces at both inner and outer wheels when deviations exceed this limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If braking force distribution control is executed to equalize slip conditions between right and left wheels, then braking stability is improved, but vehicle behavior stability deteriorates when braking force deviation exceeds certain limits during turns or deflection
Solution Approach 1:
The patent dynamically adjusts the upper limit of braking force deviation based on vehicle operating conditions including deflection angle, yaw rate, and lateral acceleration. When these parameters indicate turning or deflection states, the system modifies the allowable braking force difference between right and left wheels, enabling adaptive control that maintains braking stability while preventing vehicle behavior instability.
Solution Approach 2:
The system transitions from static braking force distribution to dynamic adjustment by continuously monitoring vehicle state parameters (deflection angle, yaw rate, lateral acceleration) and real-time braking force deviations. This dynamic control approach allows the braking system to adapt to changing vehicle conditions, equalizing slip conditions while maintaining overall vehicle stability during turns and deflection.
2Stability of the object's composition
If the upper limit of braking force deviation is set low to maintain vehicle stability, then vehicle behavior stability is improved, but braking performance deteriorates under high deceleration conditions
Solution Approach 1:
The patent implements variable upper limits for braking force deviation that change according to deceleration magnitude and vehicle state. During high deceleration events, the system increases the allowable braking force deviation to maintain braking performance, while during normal operation it maintains lower limits for stability. This parameter adaptation resolves the contradiction between stability and performance.
Solution Approach 2:
The system dynamically adjusts braking force distribution based on real-time deceleration rates and vehicle state parameters. When high deceleration is detected, the control system permits larger braking force differences between wheels to achieve maximum braking performance, while automatically returning to conservative distribution for stability during normal conditions.
3Productivity
If braking force is increased at outer wheels during turns to improve braking performance, then braking efficiency is improved, but vehicle deflection increases causing instability
Solution Approach 1:
The patent employs feedback control by continuously monitoring deflection angle, yaw rate, and lateral acceleration during braking operations. When these parameters indicate excessive vehicle response to outer wheel braking, the system automatically adjusts the braking force distribution, reducing force at outer wheels or increasing force at inner wheels to maintain orientation stability while preserving acceptable braking efficiency.
Solution Approach 2:
The system proactively prevents excessive vehicle deflection by monitoring turning conditions and preemptively adjusting braking force distribution before instability occurs. During detected turn conditions, the control system limits the maximum braking force deviation between right and left wheels, preventing the development of destabilizing lateral forces while maintaining sufficient braking capability.
Data Source
AI summary
A braking device and a controller are provided. The braking device individually adjusts braking forces that are respectively generated at wheels of a vehicle. The controller executes braking force distribution control for individually controlling the braking forces at the right and left wheels of the vehicle such that slip conditions of the right and left wheels are equal to each other through control of the braking device. The controller executes the braking force distribution control on the basis of an upper limit of a right and left braking force deviation that is a deviation in braking force between the right and left wheels.