Brake-by-Wire Threshold Adaptation for Pressure Point Shifts
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Solution Overview
Problem
Brake-by-wire systems using distance sensors for braking intention detection are susceptible to shifts in the pressure point due to temperature influences, leading to inaccurate braking torque initiation, which can cause driver irritation and hazardous situations.
Innovation Solution
A method and device using a control unit to determine a braking torque initiation based on a predetermined actuating travel, defining a pressure point as the maximum of the second derivative of the actuating force-actuating travel characteristic curve, allowing adaptation of the actuating threshold to this point without relying on expensive force sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a distance sensor is used to detect braking intention, then the cost is reduced compared to force sensors, but the measurement precision deteriorates due to pressure point shifts
Solution Approach 1:
The system performs preliminary characterization of the brake actuation system by storing reference values for actuating travel and actuating force at different brake pad wear stages. This pre-established data allows the control unit to later determine the current wear stage and adjust the actuating threshold accordingly, compensating for pressure point shifts without requiring expensive force sensors.
Solution Approach 2:
The system changes the parameter used for braking intention detection from a fixed actuating force threshold to a variable actuating travel threshold that is dynamically adjusted based on the determined brake pad wear stage. This parameter transformation allows the distance sensor to accurately detect braking intention despite pressure point shifts caused by wear.
2Device complexity
If the actuating threshold is fixed, then the device complexity is reduced, but the adaptability deteriorates due to brake pad wear and pressure point shifts
Solution Approach 1:
The system implements a feedback mechanism where the control unit continuously monitors the actuating travel of the braking element, compares it against stored reference values for different wear stages, determines the current wear stage, and automatically adjusts the actuating threshold accordingly. This closed-loop feedback enables the system to adapt to brake pad wear without increasing mechanical complexity.
Solution Approach 2:
The system performs self-diagnosis and self-adjustment by automatically determining the brake pad wear stage based on measured actuating travel and autonomously adjusting the actuating threshold. This self-service capability eliminates the need for manual calibration or complex mechanical adjustment mechanisms while maintaining high adaptability to wear conditions.
Data Source
AI summary
A method for the adaptation of an actuating threshold of a braking element of a brake-by-wire brake of a motor vehicle determines initiation of a braking torque of the brake-by-wire brake at a predetermined actuating travel of the braking element. A control unit regulates the brake-by-wire brake, wherein the actuating travel of the braking element is sensed continuously by way of a travel sensor when the braking element is manually actuated. A predetermined constant actuating force is set or an actuating force is determined continuously by way of a sensor. Furthermore, a characteristic curve is determined from at least the sensed actuating travel and the actuating force by way of the control unit and a characteristic property, in particular a maximum of a second derivative of the characteristic curve, is determined by way of the control unit.