Brake Pressure Characteristic Curves for Stable Emergency Response
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Solution Overview
Problem
In autonomous driving, pressure-medium-actuated brake systems face challenges in maintaining safety and reliability due to inertia in electro-pneumatic systems and the need for complex control loops, which can lead to instability and increased risk of underbraking or uncontrolled braking.
Innovation Solution
A method is introduced to define characteristic curves that map brake pressure to brake demand, dividing the demand range into sections where maximum brake pressure is automatically applied in emergency situations, reducing the need for complex calculations and ensuring stability by using redundant components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a closed control loop is used to achieve precise brake control, then brake precision is improved, but controller speed and stability deteriorate due to electro-pneumatic inertia
Solution Approach 1:
The brake demand value range is segmented into multiple brake demand ranges with different characteristic curve sections. Each section handles specific operating conditions differently, allowing the system to switch between precise control (when time permits) and rapid response (when inertia constraints exist), thus resolving the contradiction between precision and speed.
Solution Approach 2:
The characteristic curve is made dynamic by defining multiple sections that can be selectively applied based on current operating conditions. The system dynamically selects which characteristic curve section to use, transitioning between different control strategies to optimize both precision and response speed under varying conditions.
2Measurement precision
If complex control loops are implemented for autonomous driving, then brake precision is improved, but system stability deteriorates due to electro-pneumatic inertia
Solution Approach 1:
The control system is segmented into different characteristic curve sections, each optimized for specific operating conditions. This segmentation prevents the need for a single complex control loop to handle all scenarios, thereby improving stability while maintaining precision where needed.
Solution Approach 2:
The system changes control parameters by selecting different characteristic curve sections based on operating conditions. Instead of using a fixed complex control loop, the system adapts its control characteristics by switching between predefined sections, improving stability while maintaining precision.
3Reliability
If error checks and complex calculations are performed before braking, then safety is improved, but response time deteriorates
Solution Approach 1:
The characteristic curves are predefined and stored in advance, representing pre-calculated optimal brake pressure profiles for different operating conditions. When a brake demand occurs, the system simply selects the appropriate pre-defined curve section rather than performing complex calculations in real-time, thus maintaining safety while reducing response time.
Solution Approach 2:
Instead of performing complex error checks and calculations in real-time, the system uses pre-stored characteristic curve sections that represent validated control strategies. This copying of proven control profiles eliminates time-consuming real-time computations while maintaining safety through the use of pre-validated data.
4Reliability
If maximum brake pressure is applied in emergency situations, then safety is improved, but control precision deteriorates
Solution Approach 1:
The characteristic curve is segmented to include a third brake demand range with a vertical characteristic curve section specifically for emergency situations. This segmentation allows the system to apply maximum brake pressure when safety is critical while maintaining precise control for normal operating conditions, thus resolving the contradiction between safety and precision.
Solution Approach 2:
Different parts of the characteristic curve have different properties: the first and second sections provide precise control for normal operations, while the third section provides maximum pressure response for emergencies. This local differentiation of control characteristics allows the system to optimize for precision where appropriate and safety where critical.
Data Source
AI summary
A method for defining at least one characteristic curve which, in a pressure-actuated brake system of a vehicle, represents 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 brake pressure, and in which the brake 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 brake pressure.