Redundant EV Brake Pressure Supply for Fault-Tolerant Deceleration
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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 redundancy, modularity, and reliability, particularly in avoiding dormant faults and ensuring precise control under dynamic conditions, while also accommodating the unique demands of electric drive motors.
Innovation Solution
A braking system with a pressure supply device featuring redundant electronic control and regulating units, hydraulically supported electromechanical brakes, and electromechanical brakes, combined with electric drive motors, operates in a closed brake circuit and uses multiplex methods to ensure redundancy and precise pressure control, allowing for dynamic control and redundancy even in the event of component failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure supply device with electric-motor drive is used to build up pressure in the brake circuit, then the braking system can support highly automated driving (HAD) and fully automated driving (FAD) levels, but the system requires high redundancy and availability which increases complexity
Solution Approach 1:
The pressure supply device is divided into two mutually independent electronic control units (DV-ECU1 and DV-ECU2), each capable of controlling the electric-motor drive separately. This segmentation ensures that if one control unit fails, the other can maintain pressure control, thereby improving reliability without requiring a complete system redesign
Solution Approach 2:
The system incorporates redundant components (dual control units, redundant winding or phase systems) before failures occur. This beforehand cushioning ensures that latent faults do not compromise system availability, as the redundant components are already in place to take over immediately upon failure
2Reliability
If redundant components are implemented to ensure high availability, then system reliability improves, but the device complexity and cost increase
Solution Approach 1:
The two independent electronic control units share common hardware components such as the electric-motor drive, piston-cylinder unit, and brake circuit connections. This merging approach allows redundancy to be achieved at the control software and logic level while minimizing the increase in physical components, thereby reducing overall system complexity
Solution Approach 2:
Each electronic control unit is designed to be universal and can perform all braking control functions independently. The control units can operate in various modes (normal operation, degraded mode with one unit, emergency braking) making the redundant system adaptable to different operational requirements without adding specialized components for each scenario
3Device complexity
If the pressure supply device controls brake pressure precisely without pressure sensors, then system complexity is reduced, but measurement precision may be compromised
Solution Approach 1:
The electronic control units utilize feedback from the electric motor's current draw, position sensors on the piston, and knowledge of the brake circuit's pressure-volume characteristics to infer and control pressure. This indirect feedback mechanism achieves precise pressure control without requiring direct pressure sensor measurements, maintaining precision while reducing component complexity
Solution Approach 2:
The system replaces mechanical pressure sensing (with pressure sensors) with an electromechanical control approach. By using the electric motor's controlled displacement of the piston and monitoring the associated electrical and positional parameters, the system substitutes direct mechanical pressure measurement with an equivalent electromechanical control method that achieves the same precision
4Ease of operation
If solenoid valves and piston seals are used in the braking system, then pressure control is achieved, but safety issues and dormant faults increase
Solution Approach 1:
The patent eliminates solenoid valves and piston seals from the high-pressure brake circuit by using an electrically driven piston-cylinder unit that directly controls pressure. This extraction of problematic components (solenoid valves and seals) removes the sources of dormant faults and safety issues while maintaining full pressure control capability through the electric motor-driven mechanism
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 ensures high availability and performance by maintaining almost maximum deceleration and driving stability even with component failures, achieving redundancy and precise control through redundant components and integrated electric drive motors, supporting torque vectoring and energy recuperation.
Implementation Method 1
a pressure supply device (DV1) having an electrically driven piston-cylinder unit for building up, maintaining or reducing pressure in the brake circuit (BK1, BK2)
Implementation Method 2
Hydraulic connection to at least one brake circuit (BK1, BK2) and/or to the wheel brakes (RB1-RB4)
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.