Vehicle Brake Force Distribution Under High Coasting Deceleration
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Solution Overview
Problem
Existing vehicle braking systems face challenges in achieving a desired front-rear distribution ratio of wheel braking force during high coasting deceleration, as they do not adequately account for the additional deceleration generated by coasting deceleration, leading to instability and suboptimal vehicle attitude control.
Innovation Solution
The system includes an electronic control unit that adjusts the front-rear distribution of braking force by considering both the requested deceleration and the coasting deceleration, distributing a corrected target braking force when coasting deceleration exceeds a threshold, ensuring the total deceleration is accounted for in determining the front-rear distribution ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the front-rear distribution ratio is determined based on requested deceleration without considering coasting deceleration, then the braking control is simple, but the desired front-rear distribution ratio cannot be attained when high coasting deceleration is generated
Solution Approach 1:
The electronic control unit continuously monitors actual deceleration (including coasting deceleration) and uses this feedback to dynamically adjust the front-rear braking force distribution. When coasting deceleration is detected, the system modifies the target braking force distribution ratio to compensate, ensuring accurate attainment of the desired front-rear distribution ratio despite the additional complexity of feedback processing.
2Ease of operation
If the braking device operates without accounting for coasting deceleration, then the control process is straightforward, but vehicle stability deteriorates under high coasting deceleration conditions
Solution Approach 1:
The electronic control unit performs preliminary assessment of coasting deceleration magnitude before executing braking force distribution. When coasting deceleration exceeds a threshold, the system proactively adjusts the front-rear braking force distribution ratio in advance, preventing vehicle instability rather than reacting after instability occurs. This preliminary action maintains vehicle stability while keeping the control process relatively simple.
3Device complexity
If the front-rear distribution ratio is calculated using only requested deceleration, then the calculation is simple, but the braking force distribution does not correspond to actual vehicle deceleration
Solution Approach 1:
The system dynamically changes the parameters used in braking force distribution calculation based on operating conditions. When coasting deceleration is present, the electronic control unit switches from using only requested deceleration to using actual deceleration (requested deceleration plus coasting deceleration) as the basis for calculating the front-rear distribution ratio. This parameter change ensures accurate correspondence between braking force distribution and actual vehicle deceleration while maintaining calculation simplicity through conditional logic.
Data Source
AI summary
The electronic control unit is configured to, when braking by the braking device is performed in a deceleration state where the coasting deceleration is equal to or less than a threshold value, distribute target braking force corresponding to requested deceleration to front-wheel braking force and rear-wheel braking force in accordance with a front-rear distribution ratio determined from the requested deceleration and the braking force distribution characteristics, and when the braking is performed in a deceleration state where the coasting deceleration is higher than the threshold value, distribute corrected target braking force to the front-wheel braking force and the rear-wheel braking force in accordance with the front-rear distribution ratio determined from total deceleration and the braking force distribution characteristics, the corrected target braking force being a sum of the target braking force and braking force that generates the coasting deceleration.