Knock Sensor Signal Threshold Adjustment for Engine Reliability
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Solution Overview
Problem
Existing knock control systems for internal combustion engines face challenges in accurately determining knocking occurrence due to manufacturing variations and temporal changes, leading to incorrect detection of knocking events, especially when a large number of high-intensity vibrations are detected.
Innovation Solution
A knocking state determination device that calculates a second value based on intensity values not exceeding a first value, corrects the first value to reduce deviation, and uses both values as thresholds to determine knocking occurrence, thereby preventing undercounting of knocking events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the knock determination level is set high to reduce false positives from manufacturing variations and temporal changes, then reliability improves, but measurement precision deteriorates because actual knocking events are missed
Solution Approach 1:
The knock determination level is made dynamic by automatically adjusting it based on the detected distribution characteristics (standard deviation and cumulative percentage point) of knock sensor signals. Instead of using a fixed threshold, the system calculates VKD=Sn×VP where Sn is the standard deviation and VP is the cumulative percentage point, allowing the threshold to adapt to changing engine conditions while maintaining consistent knock detection accuracy
Solution Approach 2:
The system changes the parameters used for knock determination from fixed values to dynamically calculated values based on the distribution profile of knock sensor signals. By using statistical parameters (standard deviation Sn and cumulative percentage point VP) derived from actual signal distribution, the system optimizes the knock determination level to match actual operating conditions, resolving the contradiction between reliability and precision
2Reliability
If the knock determination level is increased to account for manufacturing variations and temporal changes, then false knock detection is reduced, but the accuracy of determining knocking occurrence is degraded
Solution Approach 1:
The system uses feedback from the distribution profile of knock sensor signals to continuously optimize the knock determination level. By monitoring the standard deviation and cumulative percentage point of detected signals, the system adjusts the threshold VKD to maintain optimal detection accuracy, ensuring that both false positives and actual knocking events are correctly identified
Solution Approach 2:
The system performs preliminary analysis of the knock sensor signal distribution to determine appropriate determination levels before actual knock detection. By pre-calculating statistical parameters from signal distribution and setting VKD=Sn×VP in advance, the system prepares optimized thresholds that account for manufacturing variations and temporal changes, improving both reliability and accuracy
Data Source
AI summary
An engine ECU executes a program including a step of calculating intensity values LOG(V) based on signals transmitted from a knock sensor; a step of deciding a maximum value V(MAX) in frequency distribution of intensity values LOG(V) for N cycles (N is a natural number); a step of calculating a knock determination level V(KD) based on the frequency distribution; a step of, when the knock determination level V(KD) is smaller than the maximum value V(MAX), removing V(MAX) from the frequency distribution; and a step of counting the total frequency of removed maximum values V(MAX) as knock occupancy KC. Maximum values V(MAX) are removed until the knock determination level V(KD) and the maximum value V(MAX) coincide, and the knock determination level V(KD) is recalculated.