Trailer Brake Pressure Sensor Plausibility Check for Over-Braking
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Solution Overview
Problem
In motor vehicle brake systems with electronic trailer control, incorrectly functioning actual-pressure sensors can lead to full braking due to continuous opening of the inlet valve when the sensor measures 0 bar, causing undesired full braking even when the desired pressure is below 1 bar.
Innovation Solution
A plausibility check is initiated at the beginning of each braking operation to verify if a minimum outlet pressure is reached within a predetermined time, automatically switching off the electronic trailer braking control and transitioning to a mechanical redundancy mode to prevent over-braking, without requiring additional sensors and without the driver's awareness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inlet valve is continuously opened to reach the desired brake pressure when the sensor measures 0 bar, then the brake pressure increases, but this causes undesired full braking and system instability
Solution Approach 1:
The plausibility check is performed before normal brake pressure regulation to detect sensor defects early. By checking whether the outlet pressure reaches a predetermined value within a specified time period after inlet valve actuation, the system identifies defective sensors before they cause full braking, preventing the harmful effect while maintaining normal operation.
Solution Approach 2:
The system uses feedback from the outlet pressure measurement to determine sensor plausibility. If the outlet pressure does not reach the expected value within the time period, the system receives feedback that the sensor is defective and switches to a safe operating mode, preventing continuous inappropriate valve actuation.
2Reliability
If the electronic trailer control system uses plausibility checks to detect sensor defects, then sensor reliability is improved, but the system complexity increases
Solution Approach 1:
The system uses its own existing components (inlet valve, outlet pressure sensor, electronic control unit) to perform the plausibility check without requiring additional sensors or external diagnostic equipment. The electronic control unit utilizes already available signals to determine sensor plausibility, making the system self-diagnostic.
Solution Approach 2:
The electronic control unit performs multiple functions: normal brake pressure regulation, outlet pressure measurement, and plausibility check evaluation. By making the control unit multi-functional, the system achieves sensor defect detection without adding separate diagnostic hardware, thus avoiding increased device complexity.
3Reliability
If the system switches to mechanical redundancy mode upon detecting sensor defects, then safety is improved, but the braking performance and precision are reduced
Solution Approach 1:
The plausibility check is performed in advance during the initial phase of brake application to detect sensor defects before they affect normal braking operation. By identifying defects early, the system can switch to mechanical redundancy mode only when necessary, maintaining precise electronic control during normal operation and ensuring safety only when defects are detected.
Data Source
AI summary
A method for checking an actual-pressure sensor of a motor vehicle brake system includes establishing the duration of a reaction interval, establishing a threshold value, operating the motor vehicle brake system in an electronic braking mode where the brake system delivers a braking pressure for operation of a trailer brake of a trailer connected to the motor vehicle. The reaction interval starts at the beginning of the braking process and pneumatic actual braking pressure values are measured by means of an actual-pressure sensor, where a starting braking pressure is measured by the actual-pressure sensor at the beginning of a braking process carried out in the electronic braking mode for the trailer. Pneumatic reaction braking pressures are measured within the reaction interval and compared to a threshold value. Brake system operation is discontinued in the electronic operating mode if none of the measured reaction braking pressures exceeds the threshold value.