Brake-by-Wire Pressure Control During Sensor Failure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In brake-by-wire systems, the immediate switch to a mechanical fallback level when a pressure sensor fails disrupts braking force assistance, causing noticeable performance loss to the driver.
Innovation Solution
The method involves calculating and storing an efficiency value for the pressure-generating device based on braking requests and actual pressure, using other sensors to estimate hydraulic pressure, and compensating for sensor failures by controlling the device based on this efficiency value, allowing continued braking force assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure sensor fails in a brake-by-wire system, then the system switches to mechanical fallback level, but braking force assistance is lost and performance loss is noticeable to the driver
Solution Approach 1:
The system pre-calculates and stores efficiency values during normal operation when the sensor is functional. These pre-computed efficiency characteristics enable the control unit to estimate actual pressure without sensor input when failure occurs, maintaining braking assistance through predictive compensation rather than immediate fallback.
Solution Approach 2:
The efficiency value acts as an intermediary parameter that bridges the gap between braking request and actual pressure when the sensor fails. Instead of directly switching to mechanical fallback, the system uses the stored efficiency characteristic to mediate pressure estimation, allowing continued electronic braking assistance through indirect pressure determination.
2Reliability
If the pressure sensor fails, then the system switches to mechanical fallback level immediately, but this causes disruption to braking force assistance
Solution Approach 1:
The system performs preliminary calculations of efficiency values during normal operation and stores them for later use. This advance preparation ensures that when sensor failure occurs, the system can immediately continue operation using stored efficiency data without time loss or immediate fallback activation.
Solution Approach 2:
The system maintains continuous braking force assistance by transitioning from sensor-based pressure determination to efficiency-value-based estimation. This continuity approach ensures that the useful action of braking assistance never中断, even during sensor failure, by seamlessly switching between different pressure determination methods.
3Duration of action of stationary object
If the pressure-generating device efficiency changes over time due to wear, then pressure generation becomes less accurate, but no compensation is made without sensor feedback
Solution Approach 1:
The system continuously pre-calculates and updates efficiency values during normal operation to capture changes in pressure-generating device performance over time. This ongoing preliminary characterization allows the system to adapt to wear and efficiency degradation, maintaining pressure generation accuracy throughout the device service life even without external sensor feedback during failure modes.
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
Maintains optimal braking performance and pedal feel by smoothly transitioning to a mechanical fallback level when necessary, ensuring the driver retains braking force assistance even with a sensor malfunction.
Implementation Method 1
a pressure-generating device is generally used, which can be driven by an electric motor and is controlled depending on a detected braking request in order to provide a hydraulic pressure necessary to implement the requested braking force in a brake circuit
Implementation Method 2
the brake circuit is assigned at least one sensor for detecting an actual hydraulic pressure in the brake circuit
Data Source
AI summary
A method for operating a braking system for a motor vehicle. The braking system includes at least one hydraulically actuatable wheel brake, a controllable pressure-generating device for providing a hydraulic pressure in a brake circuit including the at least one wheel brake, and an actuating element that is actuatable by a driver and is intended for specifying a braking request. The brake circuit is assigned a sensor for detecting an actual hydraulic pressure in the brake circuit. The pressure-generating device is controlled depending on the braking request and the actual hydraulic pressure detected in the brake circuit by the sensor. An efficiency value of the pressure-generating device is ascertained and stored depending on the braking request and the detected actual pressure. In the event of a function error of the sensor, the pressure-generating device is controlled at least depending on the braking request and the stored efficiency value.