Rationalizing Brake Signals via Torque Validation
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Solution Overview
Problem
In vehicles with autonomous driver assistance systems, the brake pedal position signal and master cylinder pressure signal do not accurately indicate all braking events, as autonomous braking occurs independently of the driver pressing the pedal, leading to challenges in rationalizing these signals for onboard diagnostics and control routines.
Innovation Solution
A method is implemented in an electronic control unit to rationalize the brake pedal position signal, master cylinder pressure signal, and brake torque signal by recording maximum and minimum values during specific learn periods and comparing them against set points, with fail flags set when differences are not sufficient, enabling or disabling the use of the brake torque signal as a brake event input signal based on successful rationalizations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the brake pedal position signal or master cylinder pressure signal is used as the brake event signal, then the signal accurately indicates driver-initiated braking events, but it fails to indicate autonomous braking events where the autonomous driver assistance system applies brakes independently
Solution Approach 1:
The brake torque signal is used as a universal indicator that covers both driver-initiated braking (via brake pedal) and autonomous braking events. The signal serves multiple functions by detecting torque application regardless of the source, making the brake event detection system adaptable to different braking scenarios including autonomous driver assistance system operations
2Adaptability or versatility
If the brake torque signal is used as the brake event signal, then all braking events including autonomous braking are indicated, but the signal may cause false failures in diagnostics due to variations in vehicle conditions
Solution Approach 1:
The system changes the parameter being monitored from position or pressure to brake torque, which provides a more direct and reliable indication of actual braking occurrence. This parameter change enables accurate detection of all braking events while reducing false failures, as torque directly reflects the mechanical action of brake application regardless of the initiation source
3Measurement precision
If rationalization routines compare brake pedal position and master cylinder pressure signals, then driver-initiated braking events are correctly identified, but autonomous braking events are missed causing diagnostic failures
Solution Approach 1:
The invention extracts the brake torque signal from the anti-lock braking system as a separate, independent indicator of braking events. This extracted signal is then used to supplement or replace the traditional rationalization approach, providing direct information about brake application that is not dependent on brake pedal position or master cylinder pressure, thereby capturing autonomous braking events that would otherwise be missed
Data Source
AI summary
In a method, a master cylinder pressure signal, a brake pedal position signal and a brake torque signal provided by an electronic control unit of an anti-lock braking system are rationalized. The master cylinder pressure signal is rationalized against the brake pedal position signal, the brake pedal position signal is rationalized against the master cylinder pressure signal and the brake torque signal is rationalized against the brake pedal position signal. The rationalizations utilize a difference between a maximum value of the signal being rationalized recorded during a maximum value learn period and a minimum value of the signal being rationalized recorded during a minimum value learn period. The rationalization is successful when this difference is greater than a rationalization value.