Brake-By-Wire Redundancy Circuits for Single-Fault Braking
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Solution Overview
Problem
Existing electronically controllable brake systems for vehicles lack robustness and residual availability to continue driving to its destination in case of single faults, with limited deceleration performance and potential instabilities when the driver is unavailable to intervene manually.
Innovation Solution
A redundant braking system is introduced with parallel construction to the service brake system, featuring independent redundant brake circuits and control modules for the front and rear axles, along with a parking brake circuit, allowing for wheel-specific control and implementing ABS and ESC functions, with separate compressed air supplies and independent power sources for each subsystem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single service brake control module is used to control both front and rear axle service brakes, then the device complexity is reduced, but the reliability decreases because a single point of failure can disable the entire service braking system
Solution Approach 1:
The brake control system is segmented into two independent service brake control modules: a front axle service brake control module controlling front axle service brakes, and a rear axle service brake control module controlling rear axle service brakes. This segmentation eliminates the single point of failure present in centralized control systems, as a failure in one module does not affect the other axle's braking capability.
Solution Approach 2:
Each axle's service brake circuit is equipped with its own dedicated control module and compressed air supply, creating locally independent control systems. The front axle has its own control module and compressed air reservoir, while the rear axle has its own control module and compressed air reservoir, allowing localized failure isolation.
2Reliability
If the parking brake circuit is used as a fallback for service brake failure, then the reliability improves, but the deceleration performance deteriorates because spring-applied brakes provide limited braking force
Solution Approach 1:
The braking system is divided into functionally independent circuits: service brake circuits for primary braking with high deceleration performance, and a parking brake circuit for fallback operation. Each circuit has its own control module and compressed air supply, allowing the service brakes to handle normal braking demands while the parking brake provides reliable fallback capability without being overloaded.
Solution Approach 2:
The system prepares fallback braking capability in advance through the independently controlled parking brake circuit. In the event of service brake failure, the parking brake control module can immediately engage spring-applied brakes on the affected axle, providing a pre-prepared safety net that maintains braking availability without compromising normal deceleration performance.
3Reliability
If electrical power supply for parking brake is independent of service brake power supply, then the reliability improves for fallback operation, but the device complexity increases due to additional power supply requirements
Solution Approach 1:
The power supply system is segmented into independent electrical power sources: the service brake control modules receive power from the vehicle's main electrical system, while the parking brake control module has its own independent electrical power supply. This segmentation ensures that electrical failures affecting the service brake system do not disable the parking brake fallback capability.
Data Source
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AI summary
The invention relates to an electronically controllable braking system (100) for a utility vehicle (200), at least comprising a service brake sub-system (102), having a front axle service brake circuit (2a) with front axle service brakes (3a), a rear axle service brake circuit (2b) with rear axle service brakes (3b), and a service brake control module (110). The brake system (100) furthermore comprises a redundancy brake sub-system (104), having a front axle redundancy brake circuit (4a), a rear axle redundancy brake circuit (4b), and a redundancy brake control module (210). A front axle redundancy brake pressure (pRVA) can be applied to the front axle service brakes (3a) and a rear axle redundancy brake pressure (pRHA) can be applied to the rear axle service brakes (3b), and the redundancy brake control module (210) is designed to generate a redundancy brake control signal (Sr) depending on a braking specification (VAB, VB), wherein the front axle and rear axle redundancy brake pressure (pRVA, pRHA) can be generated depending on the redundancy brake control signal (Sr) and specified to the front axle and rear axle service brakes (3a, 3b) to allow implementation, electrically controlled by the redundancy brake control module (210), of the braking specification (VAB, VB) via the front axle redundancy brake circuit (4a) and the rear axle redundancy brake circuit (4b).