Brake Pressure Characteristic Curves for Stable Electro-Pneumatic Control
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Solution Overview
Problem
Autonomous driving systems face challenges in ensuring high safety and reliability in brake control due to the inertia of electro-pneumatic braking systems and the complexity of controlling vehicle deceleration, leading to potential under-braking or uncontrolled braking scenarios.
Innovation Solution
The method involves defining multiple characteristic curve sections to map brake demand to brake pressure, allowing for different gradients and maximum pressure application, independent of vehicle deceleration distribution, and enabling redundant systems to compensate for faults, ensuring reliable brake pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a closed control loop is used in autonomous driving mode, then control quality improves, but controller speed requirements cannot be met due to electro-pneumatic braking system inertia
Solution Approach 1:
The brake demand value range is divided into multiple brake demand ranges, with each range having its own characteristic curve section. This segmentation allows the system to use simpler control logic for each segment while maintaining overall control quality, avoiding the need for complex high-speed closed-loop control.
Solution Approach 2:
Characteristic curves are pre-defined for different brake demand ranges, establishing the relationship between brake demand and brake pressure in advance. This preliminary action eliminates the need for real-time complex calculations, allowing the system to meet controller speed requirements while maintaining control quality.
2Speed
If a linear relationship between brake demand and output brake pressure is used, then controller speed requirements are met, but safety and reliability decrease due to inability to compensate for disturbances
Solution Approach 1:
The system uses multiple characteristic curve sections with different gradients for different brake demand ranges, making the brake pressure response dynamic rather than linear. This allows the system to adapt to different operating conditions and compensate for disturbances while maintaining controller speed.
Solution Approach 2:
The gradient of the characteristic curve is changed across different brake demand ranges. By adjusting the parameter (gradient) of the characteristic curve according to the brake demand range, the system achieves both speed requirements and safety compensation.
3Device complexity
If the brake demand value range is processed uniformly, then device complexity is reduced, but manufacturing precision of brake pressure control deteriorates
Solution Approach 1:
The brake demand value range is segmented into multiple ranges, each with its own characteristic curve section. This segmentation improves brake pressure control precision by allowing optimized control for each range while keeping the overall device complexity manageable through standardized curve definitions.
Data Source
AI summary
A method for defining at least one characteristic curve of a pressure-medium-actuated brake system of a vehicle, the curve representing a relationship between a brake pressure and a brake demand, and for operating a pressure-actuated brake system of a vehicle, in which at least one brake cylinder can be supplied with a pressurized medium under a braking pressure, and in which the braking pressure is formed based on at least one such characteristic curve, and to a pressure-actuated brake system of a vehicle in which at least one brake cylinder can be supplied with a pressurized medium under a braking pressure.