Hydraulic Brake Pressure Differential Control for μ-Split Stability
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Solution Overview
Problem
In μ-split braking situations, where differing coefficients of friction cause yawing of vehicles, existing brake systems either lead to underbraking on high-friction sides or require excessively long braking distances, necessitating improved hydraulic-pressure management to balance braking forces across wheels.
Innovation Solution
A method and system for operating a hydraulic motor-vehicle brake system that creates and maintains a hydraulic-pressure difference across opposite wheel brakes using slip-regulating valve devices, allowing for adjustable pressure settings and overflow mechanisms to ensure balanced braking forces, even when the driver increases pressure, thereby reducing yawing and braking distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If select-low regulation is implemented to avoid yawing by setting braking force at rear wheels according to low-friction side, then vehicle controllability is preserved, but braking distance is considerably lengthened due to underbraking on high-friction side
Solution Approach 1:
The patent applies local quality by allowing different braking forces on different sides of the vehicle. Specifically, it permits a braking-force difference up to a defined threshold (e.g., 20% of total braking force) between left and right wheels on the same axle, enabling the high-friction side to contribute more braking force while the low-friction side maintains stability, thus optimizing both braking distance and vehicle control
2Stability of the object's composition
If braking-force difference is gradually increased up to a defined value to delay yawing moment build-up, then driver has sufficient time to compensate yawing by steering, but braking distance is still longer than optimal
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the braking-force difference as a controllable parameter. It allows the braking-force difference to vary within a defined range (0-20% of total braking force) and introduces a side-slip angle parameter (0.5°-8°) to optimize the balance between yawing control and braking efficiency, thereby reducing braking distance while maintaining stability
3Extent of automation
If conventional ABS slip-regulating valves are closed to decouple driver from braking-force regulation in μ-split situation, then braking-force regulation is achieved, but driver experiences hard pedal feedback
Solution Approach 1:
The patent introduces a pressure sensor as an intermediary element that mediates between the driver's brake pedal input and the actual braking-force regulation. The sensor detects master-cylinder pressure changes and transmits this information to the control unit, which then adjusts braking forces accordingly while maintaining soft pedal feedback, thus combining automated regulation with driver feedback
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces the braking distance in μ-split situations by maintaining hydraulic-pressure differences across wheels, allowing for timely driver reaction to yawing and improving vehicle stability without the 'hard' pedal feedback issue, enhancing the overall braking performance.
Implementation Method 1
building up a hydraulic pressure at the wheel brakes by transfer of hydraulic fluid from the hydraulic-pressure generator to the wheel brakes
Implementation Method 2
creating a hydraulic-pressure difference across opposite wheel brakes of a vehicle axle
Data Source
AI summary
Proposed is a technique for operating a hydraulic motor vehicle brake system in an operating situation which requires the formation of a hydraulic pressure difference at opposite wheel brakes of a vehicle axle. Here, each wheel brake is assigned a first slip regulating valve device for decoupling the respective wheel brake from a hydraulic pressure generator, and a second slip regulating valve device for dissipating hydraulic pressure at the respective wheel brake. A method implementation of this technique comprises the steps of building up a hydraulic pressure at the opposite wheel brakes during the course of a braking process, detecting a requirement for forming a hydraulic pressure difference at the opposite wheel brakes, actuating one or more of the slip regulating valve devices assigned to the opposite wheel brakes so as to form the hydraulic pressure difference by virtue of different hydraulic pressures being set at the opposite wheel brakes, and, in reaction to a driver demand, increasing the hydraulic pressure at the opposite wheel brakes, including the wheel brake at which a relatively low hydraulic pressure is to be set, while maintaining the hydraulic pressure difference by transferring hydraulic fluid from the hydraulic pressure generator via the first slip regulating valve devices to the opposite wheel brakes.