Redundant Brake System for Automated Vehicles
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Solution Overview
Problem
Existing brake systems for vehicles with hydraulically operational wheel brakes lack the ability to operate without a mechanical and/or hydraulic linkage between the brake pedal and wheel brakes, compromising availability and safety in highly automated driving scenarios.
Innovation Solution
A brake system with two electrically controllable pressure sources, each connected to a separate brake circuit supply line via a separating valve, with independent electronic control units and actuators to ensure hydraulic separation and connection, allowing for autonomous operation and redundancy in case of failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a mechanical and/or hydraulic linkage between brake pedal and wheel brakes is eliminated for highly automated driving, then automation capability is improved, but system reliability deteriorates due to loss of redundant mechanical operation capability
Solution Approach 1:
The brake system is segmented into two independent brake circuits (first and second brake circuits), each with its own electrically controllable pressure source. This segmentation ensures that a failure in one circuit does not compromise the entire braking system, thereby maintaining reliability while enabling automated operation.
Solution Approach 2:
The system incorporates redundant pressure sources and electronic control units before failures occur. Each brake circuit has its own independent pressure source and control unit, providing a backup capability that cushions against potential failures, ensuring continued operation even when one component fails.
2Reliability
If two electrically controllable pressure sources with independent electronic control units are implemented, then system reliability is improved through redundancy, but device complexity increases
Solution Approach 1:
The control system is segmented into two independent electronic control units, each responsible for one pressure source and one brake circuit. This modular segmentation manages complexity by distributing control functions while maintaining system reliability through redundancy.
Solution Approach 2:
Each electronic control unit is designed to be multi-functional, capable of controlling both its assigned pressure source and monitoring system status. This universality reduces overall system complexity by avoiding the need for dedicated specialized components for each function.
3Reliability
If the first electronic control unit controls the first pressure source and the second electronic control unit controls the second pressure source with cross-control of separation valves, then system reliability is improved, but control complexity increases
Solution Approach 1:
The control architecture is designed to be dynamic and adaptive. Each electronic control unit can control its own pressure source and also control the separation valve of the other pressure source when needed. This dynamic cross-control capability allows the system to adapt to failures while managing control complexity through conditional activation of cross-control functions.
4Reliability
If hydraulic separation of brake circuits is implemented through a circular device, then safety is improved by preventing pressure loss to other circuits, but device complexity increases
Solution Approach 1:
The circular device extracts and isolates the hydraulic connection between the two brake circuits. By physically separating the hydraulic pathways and using the circular device to control connection and disconnection, the system prevents pressure loss from spreading to other circuits while managing hydraulic complexity through dedicated isolation mechanisms.
Data Source
Figure 1
AI summary
The invention relates to a braking system for a motor vehicle having at least four hydraulically actuatable wheel brakes (8a-8d), comprising a first electrically controllable pressure source (5), which is separably connected to a first brake circuit supply line (13a) via a first separating valve (26), a second electrically controllable pressure source (2), which is separably connected to a second brake circuit supply line (13b) via a second separating valve (27), at least four electrically actuatable inlet valves (6a-6d), each inlet valve being associated with one of the wheel brakes, the first brake circuit supply line (13a) being connected to two of the inlet valves (6c, 6d) and the second brake circuit supply line (13b) being connected to the two other inlet valves (6a, 6b), an electrically actuatable outlet valve (7a-7d) for each wheel brake, an electrically actuatable circuit separating device (60), by means of which the first and second brake circuit supply lines can be hydraulically separated and connected, a first electronic device (A), by means of which the first pressure source is actuated, and a second electronic device (B), by means of which the second pressure source is actuated, the second electronic device (B) being electrically independent of the first electronic device (A), the first separating valve (26) being actuated by the second electronic device (B) and the second separating valve (27) being actuated by the first electronic device (A). The invention further relates to a method for operating said braking system.