Redundant EV Brake Pressure Supply for Fault-Tolerant Control
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Solution Overview
Problem
Existing braking systems for electric vehicles and vehicles with automated driving levels 3 to 5 face challenges in achieving high availability, redundancy, and precise control while managing complex interactions with electric drive motors, particularly in maintaining pedal feel and preventing dormant faults.
Innovation Solution
A braking system with a redundant pressure supply device, hydraulically supported electromechanical brakes, and electric drive motors, combined with a central control unit, ensures high redundancy and precise pressure control, using multiplex methods and redundant components to maintain functionality even in the event of component failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant pressure supply device with dual independent electronic control and regulating units is implemented, then system reliability and availability are improved for HAD/FAD levels, but device complexity and cost increase
Solution Approach 1:
The pressure supply device is segmented into two mutually independent electronic control and regulating units, each capable of independently controlling the electric-motor drive. This segmentation ensures that if one unit fails, the other can maintain system functionality, thereby improving reliability without requiring complete system redundancy
Solution Approach 2:
The system incorporates redundant control units and diagnostic capabilities that prepare for potential failures before they occur. The dual-unit architecture provides a backup control path that is already in place and can immediately take over if one unit fails, cushioning against system unavailability
2Reliability
If closed brake circuits are used in ABS operation, then safety is improved by preventing dormant faults, but ease of manufacture and system complexity increase
Solution Approach 1:
The brake system dynamically switches between open and closed circuit configurations based on operational requirements. During ABS operation, the system transitions to a closed brake circuit configuration to prevent dormant faults, while allowing open configuration during normal operation for easier manufacturing and maintenance
Solution Approach 2:
The electronic control and regulating units act as intermediaries that manage the complexity of closed brake circuit operations. They provide intelligent control that simplifies the implementation of safety-critical closed circuits by automating the management of brake fluid pressure and valve actuation
3Ease of operation
If pedal position sensors and pedal simulators are maintained for HAD/FAD levels, then pedal feel characteristics are preserved, but device complexity and cost increase
Solution Approach 1:
The pedal simulator unit is designed to serve multiple functions: providing pedal feel feedback to the driver, sensing pedal position, and communicating with the electronic control units. This multi-functionality reduces the need for separate dedicated components, thereby maintaining pedal feel characteristics while limiting the increase in overall system complexity
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
The system provides high availability and precise control, ensuring safe and reliable braking with minimal performance loss even in the event of component failures, supporting various driving levels and electric vehicle types.
Implementation Method 1
The pressure supply device (DV1) has an electric-motor drive (M1), which is controlled by the control and regulating device (DV-ECU)
Implementation Method 2
The piston (KB) delimits a pressure chamber (DR) in order to build up, maintain or reduce pressure therein
Implementation Method 3
A hydraulic line (HL1) leads from the pressure chamber (DR) to the brake circuit (BK1, BK2)
Data Source
AI summary
A brake system for a vehicle may contain redundant components that permit braking force to be applied in case of partial or complete failure of a primary braking mechanism. The system may include at least one hydraulic brake circuit having at least one hydraulically operating wheel brake; a pressure supply device driven by an electric-motor drive; at least one electronic control and regulating device; a valve assembly having valves for setting wheel-specific brake pressures and/or for (dis)connecting the wheel brakes (from) to the pressure supply device; a piston-cylinder unit actuable by an actuating device, which can be connected to the at least one hydraulic brake circuit, to at least one brake unit comprising an electric drive motor, to an electric parking brake, to a hydraulically supported electromechanical brake, and/or to an electromechanical brake; at least one electric drive motor for at least one axle or wheel; and a central control unit.