Redundant Brake-Steering Control for Wheel-Specific Yaw Stability
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Solution Overview
Problem
Existing brake and steering systems in electric vehicles, particularly for highly automated and autonomous driving, lack redundancy and efficiency, leading to issues such as increased braking distances, pedal sensation changes, and reduced vehicle stability, especially in heterogeneous road conditions.
Innovation Solution
A driving dynamics system with dual electrohydraulic pressure supply devices and redundant hardware/software architecture, enabling wheel-specific pressure adjustments and yaw moment interventions, ensuring fault-tolerant operation through redundant actuators and controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single electrohydraulic pressure supply device is used in the brake system, then the device complexity is reduced, but the reliability decreases due to lack of redundancy in automated driving modes
Solution Approach 1:
The brake system is divided into two independent brake circuits (first and second brake circuits), each with its own electrohydraulic pressure supply device. This segmentation provides functional redundancy so that if one circuit fails, the other can still provide braking capability, thereby improving reliability while managing complexity through modular design.
Solution Approach 2:
The system implements redundancy by providing a second electrohydraulic pressure supply device as a backup for the first. This beforehand cushioning ensures that if the primary pressure supply device fails, the system can switch to the backup device, maintaining brake functionality and improving reliability before failure occurs.
2Loss of time
If wheel-specific pressure control is implemented, then the braking distance is reduced, but the device complexity increases due to additional pressure adjustment valves and control mechanisms
Solution Approach 1:
The system applies different brake pressures to different wheels through wheel-specific pressure control. Each wheel can receive optimized pressure based on its specific conditions (road surface, loading, etc.), improving braking efficiency and reducing braking distance while maintaining overall system control.
Solution Approach 2:
The electrohydraulic pressure supply devices are designed to perform multiple functions: they can provide pressure for normal braking, emergency braking, and wheel-specific pressure control. The brake pressure adjustment valves can operate in different modes (normal operation, fault mode, automated intermittent brake mode), reducing the need for separate dedicated components for each function.
3Reliability
If the automated intermittent brake function is activated, then the vehicle deceleration is maintained in fault cases, but the pedal sensation changes and wheel locking may occur when the driver actuates the pedal
Solution Approach 1:
The system continuously monitors the operational state of the brake system, including pressure levels, valve positions, and circuit integrity. When a fault is detected, the feedback mechanism triggers a switch to automated intermittent brake mode, maintaining deceleration while isolating the fault to prevent wheel locking and preserve pedal sensation for the driver.
Solution Approach 2:
The brake system dynamically adapts its control strategy based on operational conditions. In normal operation, the system provides smooth pressure control with proper pedal sensation. When faults are detected, the system dynamically switches to automated intermittent brake mode, adjusting the control approach to maintain safety while minimizing impact on driver operation.
4Stability of the object's composition
If the electric steering actuator is supported by pressure supply devices for yaw moment intervention, then the vehicle stability is improved, but the device complexity increases due to integration of steering and brake systems
Solution Approach 1:
The system merges the steering and brake systems by allowing the electrohydraulic pressure supply devices to support both steering actuation and brake functions. This integration enables coordinated control of steering and braking for enhanced vehicle stability, particularly in automated driving modes, while sharing common hardware resources.
Solution Approach 2:
The electrohydraulic pressure supply devices are designed with multi-functionality, serving both the brake system and the steering system. This universal design allows a single component to perform multiple functions, improving vehicle stability through coordinated control while avoiding the need for completely separate systems, thereby managing 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
Enhances vehicle stability and reduces braking distances by providing redundant wheel-specific pressure control and yaw moment interventions, ensuring safe and efficient operation even in failure scenarios.
Implementation Method 1
a first electrohydraulic pressure supply device (DV1) and a second electrohydraulic pressure supply device (DV2); four hydraulically actuable wheel brakes (RB1-RB4) that are assigned to wheels (R1-R4)
Implementation Method 2
electrically actuable brake pressure adjustment valves
Implementation Method 3
an, in particular electric, steering actuator for actuating at least one axle
Implementation Method 4
wheel-specific pressure adjustments and yaw moment interventions
Data Source
AI summary
A driving dynamics system for a vehicle may include a primary control unit for detecting and/or generating steering commands and braking commands; a brake system having first and second electrohydraulic pressure supply units; four hydraulically actuable wheel brakes of respective wheels; electrically actuable brake pressure adjustment valves; and an electric steering actuator for actuating at least one axle. The driving dynamics system may implement a steering command during normal operation to actuate at least one of the pressure supply units and the steering actuator and/or, to implement a braking command during normal operation, to actuate at least the second pressure supply unit and at least the brake pressure adjustment valves for a wheel-specific pressure adjustment and, in a fault case, to actuate at least the first pressure supply unit and at least the brake pressure adjustment valves for a wheel-specific pressure adjustment.