Brake Control Unit Segmentation for Fault Isolation
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Solution Overview
Problem
Highly automated motor vehicles require reliable braking mechanisms to ensure safe standstill in case of system failures, such as power supply failures or errors in the brake control unit, which current fail-safe architectures cannot guarantee, leading to uncontrollable rolling or acceleration on slopes.
Innovation Solution
A control unit for the motor vehicle brake system with separate voltage supplies for service and parking brake functional assemblies, designed to maintain functionality of at least one brake assembly for a defined period in case of faults, allowing the vehicle to be braked to a standstill using the parking brake or transmission lock, ensuring safe engagement and holding of the vehicle at a standstill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a central brake control device with redundant computing and switch-off paths is used to achieve fail-safe operation, then safety is improved, but device complexity increases
Solution Approach 1:
The brake control device is divided into two independent functional assemblies: a service brake assembly and a parking brake assembly. Each assembly has its own microprocessor and control logic, allowing independent operation. This segmentation enables the system to maintain braking functionality even if one assembly fails, achieving fail-safe operation without requiring complex redundant computing paths within a single centralized controller.
Solution Approach 2:
The parking brake function is extracted from the service brake control system and implemented as a separate functional assembly with independent microprocessor control. This extraction allows the parking brake to operate autonomously when the service brake system fails, providing a simplified fail-safe mechanism that doesn't require complex inter-assembly communication or redundant computing paths.
2Device complexity
If the service brake and parking brake share a common voltage supply, then device complexity is reduced, but reliability decreases due to single point of failure
Solution Approach 1:
The voltage supply system is segmented into two independent power sources: a first voltage supply for the service brake assembly and a second voltage supply for the parking brake assembly. This segmentation ensures that a failure in one power supply does not affect the other brake function, allowing the vehicle to maintain braking capability even during power supply failures.
Solution Approach 2:
The system changes the electrical parameter configuration by providing separate voltage supplies with different ground references (first ground and second ground) for the two brake assemblies. This parameter change allows independent operation and fault isolation, enabling the parking brake to function even when the service brake power supply fails or has incorrect ground potential.
3Reliability
If separate functional assemblies with separate voltage supplies are used to ensure fault isolation, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The brake control system is segmented into two independently manufacturable functional assemblies, each with its own microprocessor, control circuitry, and voltage supply interface. This segmentation allows each assembly to be manufactured, tested, and validated separately, potentially simplifying the manufacturing process despite the increased component count, while ensuring fault isolation between assemblies.
Data Source
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AI summary
A controller for a motor vehicle brake system includes a first functional assembly for controlling a service brake and a second functional assembly for controlling a parking brake. The first and the second functional assemblies can be supplied by separate voltage supplies. The controller is configured in such a way that, in the event of a fault in or affecting the first or the second functional assembly, the respective other functional assembly remains ready for use for at least a defined period of time, and the motor vehicle can be braked by means of the ready-for-use functional assembly within the defined period of time in order to engage a transmission lock of the vehicle and/or in order to hold the vehicle at a standstill using the parking brake.