Rough Road Detection System for Vehicle Diagnostic Accuracy
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Solution Overview
Problem
Rough road conditions lead to false positive errors in vehicle diagnostic components, such as misfire monitors, due to misinterpretation of road surface irregularities as engine misfires, affecting accurate engine control operations.
Innovation Solution
An on-board diagnostic system with a rough road detector that uses wheel speed sensors to determine the average road surface roughness, comparing it to a threshold to disable false error outputs from diagnostic components, employing a high pass filter and rolling average filter to process signals and set a roughness flag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diagnostic components continuously monitor vehicle operating conditions to detect abnormalities, then diagnostic accuracy is improved, but false positive errors increase under rough road conditions
Solution Approach 1:
A rough road detector is introduced as an intermediary component between the wheel speed sensors and the diagnostic component. This detector processes wheel speed signals to determine road roughness levels and generates a rough road flag that mediates the diagnostic component's error output, preventing false positives while maintaining diagnostic accuracy through selective disabling during rough road conditions
Solution Approach 2:
The system changes the operational parameter of the diagnostic component based on road roughness detection. When the rough road detector determines that road roughness exceeds a predetermined threshold, it disables the diagnostic component's error output function. This parameter change (from active monitoring to disabled state) resolves the contradiction by adapting the diagnostic component's behavior to road conditions
2Reliability
If the misfire monitor operates continuously to detect engine misfires, then emission control is improved, but false misfire detection increases on rough roads
Solution Approach 1:
The rough road detector provides feedback to the misfire monitor by generating a rough road flag based on processed wheel speed signals. This feedback mechanism allows the misfire monitor to adjust its operation - disabling error output when rough road conditions are detected - thereby eliminating false misfire detections while maintaining emission control accuracy during normal conditions
3Reliability
If wheel speed signals are processed continuously to detect road roughness, then false positive reduction is improved, but system complexity increases
Solution Approach 1:
The signal processing function is segmented into distinct modular components: a high pass filter to extract roughness-related frequency components from wheel speed signals, a rolling average filter to smooth the extracted signal over time, and a comparator to determine rough road conditions. This segmentation reduces overall system complexity by breaking down the continuous processing into discrete, manageable stages
Data Source
AI summary
An on-board diagnostic system of a vehicle comprises disabling diagnostic operation, such as a misfire monitor, based on road roughness. In one example, the disabling of the diagnostic operation is based on brake actuation and degradation of an anti-lock braking system.