Vehicle Braking Control for Cascade Lock Detection on Low-μ Roads
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
During braking in a four-wheel drive vehicle on a low μ road, cascade lock can occur, leading to rapid decreases in wheel speeds and making it difficult to determine if the vehicle is on a low μ road, as the vehicle body speed cannot be appropriately derived.
Innovation Solution
A vehicle braking control device that includes wheel speed sensors and an anteroposterior acceleration sensor to derive wheel deceleration values, an average value of these decelerations, and determine if a slip increase state has occurred, thereby detecting the occurrence of cascade lock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel speed difference method is used to determine low μ road, then low μ road detection is possible under normal braking, but cascade lock cannot be detected when all wheels lock simultaneously
Solution Approach 1:
The patent changes the detection parameter from wheel speed difference to wheel deceleration increase rate. By monitoring how rapidly wheel deceleration increases during braking, the system can detect cascade lock even when all wheels lock simultaneously, as the sudden increase in deceleration rate serves as a distinctive signature of this phenomenon.
Solution Approach 2:
The patent introduces wheel deceleration as an intermediary parameter between wheel speed and vehicle state. Instead of directly observing wheel speed differences, the system uses wheel deceleration (the rate of change of wheel speed) as a mediator to indirectly detect the occurrence of cascade lock, enabling detection of this subtle phenomenon.
2Measurement precision
If vehicle body speed is derived from wheel speeds during braking, then vehicle speed estimation is possible, but derivation becomes inaccurate when cascade lock occurs
Solution Approach 1:
The patent performs preliminary detection of cascade lock conditions by monitoring wheel deceleration increase rates before attempting vehicle body speed derivation. When cascade lock is detected through the characteristic increase in wheel deceleration rate, the system can take preliminary actions to adjust speed derivation methods or apply corrections, ensuring accurate vehicle speed estimation even during cascade lock events.
Data Source
AI summary
A braking control device includes: a wheel deceleration deriving section that derives decrease rates of wheel speed detection values as wheel deceleration calculation values; an average value deriving section that derives an average value of the wheel deceleration calculation values of wheels FL, FR, RL, and RR as a wheel deceleration average value; a determination section that determines, based on the wheel deceleration average value and an anteroposterior deceleration detection value, whether or not a slip increase state has been occurring for a determination time or longer; and a detection section that detects occurrence of cascade lock when it is determined that the slip increase state has been occurring for the determination time or longer during vehicle braking.