Hydraulic Brake System Redundancy via Third Pressure Generator
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Solution Overview
Problem
Hydraulic motor vehicle brake systems for autonomous or semi-autonomous driving lack sufficient redundancy, as they cannot assume a driver's presence or prompt brake pedal actuation, necessitating additional redundant braking functions to ensure operational safety.
Innovation Solution
A dual-circuit hydraulic motor vehicle brake system with independently actuable first and second brake circuits, an electric parking brake system, and a third hydraulic pressure generator, along with a controller that detects functional losses and requirements for control interventions to actuate appropriate components for assistance or intervention, including actuators and pressure generators, to maintain braking functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a driver-operated brake system with a single master cylinder is used, then the system is simple and easy to operate, but it lacks sufficient redundancy for autonomous or semi-autonomous driving
Solution Approach 1:
The brake system is divided into two independent brake circuits (first brake circuit and second brake circuit), each capable of independently actuating wheel brakes. This segmentation ensures that if one circuit fails, the other can still provide braking functionality, thereby improving redundancy without requiring a complete system redesign
Solution Approach 2:
Each brake circuit is designed to be universally capable of performing all braking functions including service braking, emergency braking, and control interventions (ABS, ESP, hill holder). This multi-functionality allows either circuit to take over completely if one fails, maximizing redundancy while maintaining system simplicity
2Reliability
If electric actuators are added to provide redundant braking function, then operational safety is improved, but the device complexity increases
Solution Approach 1:
Electric actuators are integrated into the existing brake circuit architecture, combining electrical actuation capability with the hydraulic brake system. The actuators are merged with the brake circuits such that they can directly generate hydraulic pressure without requiring separate redundant master cylinders, thereby reducing overall component quantity
Solution Approach 2:
The electric actuators are designed to autonomously detect and respond to brake requirements through the controller, which monitors brake pressure and actuator status. When a functional loss is detected in one brake circuit, the controller automatically activates the appropriate actuator in the other circuit to maintain braking functionality, eliminating the need for complex manual intervention systems
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
Enhances redundancy and operational safety by ensuring continued braking functionality even with partial or complete failures in brake circuits, enabling effective control interventions such as anti-lock braking, traction control, and vehicle dynamics control.
Implementation Method 1
a first brake circuit which acts on one or more first wheel brakes, and is provided with a first hydraulic pressure generator which can be actuated electrically for control interventions
Implementation Method 2
a second brake circuit which acts on one or more second wheel brakes, and is provided with a second hydraulic pressure generator which can be actuated electrically for control interventions and can be actuated independently of the first hydraulic pressure generator
Implementation Method 3
an electric parking brake (EPB) system with an electrically actuable first actuator which is assigned to one of the first wheel brakes, and an electrically actuable second actuator which is assigned to one of the second wheel brakes
Implementation Method 4
an electrically actuable third hydraulic pressure generator which is configured to generate a hydraulic pressure for at least one of the two brake circuits
Data Source
AI summary
A hydraulic motor vehicle brake system comprises a vehicle dynamic control system which comprises a first brake circuit which acts on at least one first wheel brake, and a second brake circuit which acts on at least one second wheel brake, the first brake circuit comprising a first hydraulic pressure generator and the second brake circuit comprising a second hydraulic pressure generator, which can be actuated electrically for control interventions. Furthermore, the hydraulic motor vehicle brake system comprises an electrically actuable third hydraulic pressure generator, and a controller which is configured to detect failure of at least one of the two brake circuits and a requirement of a control intervention on the at least one brake circuit, to actuate at least the third hydraulic pressure generator for assisting the control intervention.