Vehicle Braking Control for Turning Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional braking force distribution control systems for vehicles, such as those described in Japanese Patent Application Laid-Open (kokai) No. 2018-62295, face challenges in maintaining vehicle stability during turning, as they rely on controlling rear wheel braking forces to balance slippage, which can lead to insufficient anti-spin yaw moment generation due to differences in vertical loads between wheels, resulting in potential oversteer or understeer.
Innovation Solution
A braking control apparatus that independently controls the braking forces of both front and rear wheels, using slippage degree detection and feedback control to adjust rear wheel braking forces based on deviations from a target slippage degree, and incorporates turning determination and correction mechanisms to generate an anti-spin yaw moment by adjusting the feedback controlled variables, thereby stabilizing vehicle turning behavior without relying on front wheel adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If braking force distribution control is performed by controlling rear wheel braking forces to balance slippage, then vehicle stability during braking is improved, but anti-spin yaw moment generation becomes insufficient during turning due to vertical load differences between wheels
Solution Approach 1:
The patent applies different control strategies to different wheels based on their local conditions. Specifically, it identifies the wheel with smaller vertical load (larger slippage degree) and applies enhanced braking force control to that specific wheel through correction amounts, rather than treating all wheels uniformly. This local quality approach ensures adequate anti-spin yaw moment generation while maintaining overall vehicle stability.
Solution Approach 2:
The patent dynamically adjusts braking force parameters based on detected wheel slippage degrees and vertical load conditions. By calculating correction amounts based on slippage degree differences and applying them to specific wheels, the system changes the braking force parameters in real-time to optimize both stability and anti-spin moment generation during turning maneuvers.
2Stability of the object's composition
If braking forces of left and right rear wheels are controlled to balance slippage degrees, then vehicle yawing is suppressed, but the braking force of the rear inner wheel becomes smaller than the rear outer wheel, potentially causing behavioral errors
Solution Approach 1:
The patent calculates correction amounts in advance based on the difference in slippage degrees between wheels and applies them as preliminary adjustments to the braking forces. This preliminary anti-action compensates for the potential behavioral errors before they occur, ensuring that the rear inner wheel receives adequate braking force while still suppressing vehicle yawing.
3Force
If larger braking force is distributed to front wheels, then braking effectiveness is improved, but the degree of correction of vehicle behavior by braking force control becomes rougher compared to rear wheels
Solution Approach 1:
The patent segments the vehicle behavior correction function between front and rear wheels based on their respective capabilities. It assigns the primary correction task to rear wheels where precise control is possible, while using front wheel braking primarily for generating stopping force. This segmentation allows the system to leverage the high braking force capability of front wheels without relying on them for precise behavioral correction.
Data Source
AI summary
A brake ECU sets target slippage degrees of three wheels other than the front outer wheel to the slippage degree of the front outer wheel and feedback-controls the braking forces of the three wheels such that the actual slippage degrees of the three wheels approach the target slippage degrees. The brake ECU computes a correction amount for the slip ratio deviation of the front inner wheel such that the slip ratio deviation becomes zero. The brake ECU multiplies the correction amount for the slip ratio deviation by a load ratio and uses the resultant value as a correction amount for the slip ratio deviation of the rear inner wheel. The brake ECU corrects the slip ratio deviation by using the computed correction amount.