Dynamic Gain Switching for Abnormal Combustion Detection
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Solution Overview
Problem
Existing abnormal combustion detection systems in internal combustion engines face difficulties in accurately detecting small abnormal combustion due to gain settings that attenuate both large and small waveforms, leading to delayed gain switching and improper detection of micro knocks.
Innovation Solution
An abnormal combustion detection apparatus with a gain switching unit that switches the gain from a small to a large value at the ignition timing, utilizing the dynamic range of the AD conversion circuit and employing a shift register to cancel gain differences and prevent ringing, allowing for effective detection of both small and large abnormal combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gain of the gain circuit is set to a small value to attenuate large abnormal combustion waveforms, then large abnormal combustion can be detected without overflow, but small abnormal combustion becomes very difficult to detect due to excessive attenuation
Solution Approach 1:
The gain of the gain circuit is dynamically switched between a first gain value and a second gain value based on the detection results of the large abnormal combustion determination unit and small abnormal combustion determination unit. This dynamic adjustment allows the system to adapt to different combustion conditions, preventing overflow for large abnormalities while maintaining sensitivity for small abnormalities.
Solution Approach 2:
The abnormal combustion detection is segmented into two separate determination units: a large abnormal combustion determination unit and a small abnormal combustion determination unit. Each unit operates with appropriate gain settings, allowing simultaneous detection of both large and small abnormal combustion events without mutual interference.
2Measurement precision
If the gain of the gain circuit is set to a large value to detect small abnormal combustion, then small abnormal combustion can be detected with sufficient sensitivity, but large abnormal combustion causes overflow of the AD conversion circuit
Solution Approach 1:
The gain switching unit dynamically adjusts the gain based on real-time detection results. When large abnormal combustion is detected, the gain is set to the first (smaller) value to prevent overflow. When only small abnormal combustion is present, the gain is set to the second (larger) value to enhance detection sensitivity.
Solution Approach 2:
The system changes the gain parameter of the gain circuit based on the amplitude characteristics of the detected waveform. By monitoring the waveform amplitude and comparing it against thresholds, the system selects appropriate gain values to optimize detection for both small and large abnormal combustion conditions.
3Reliability
If gain switching is performed after detecting waveform size, then overflow of knock detection signal can be prevented, but micro knock detection is delayed due to gain switching delay in violently changing knock detection signal amplitude
Solution Approach 1:
The system performs preliminary detection using the large abnormal combustion determination unit before final determination. This preliminary action allows early identification of large abnormalities, enabling proactive gain switching to prevent overflow while maintaining rapid response for micro knock detection through the parallel small abnormal combustion determination unit.
Data Source
AI summary
An abnormal combustion detection apparatus detects an abnormal combustion of an internal combustion based on a vibration waveform from a vibration sensor attached to the internal combustion engine. A gain circuit of the apparatus amplifies or attenuates the vibration waveform from the vibration sensor, an AD conversion circuit converts a waveform provided by the gain circuit to digital data, and a gain switching unit switches a gain of the gain circuit from a small gain value to a large gain value at a gain switch timing. The gain switching unit separates a large abnormal combustion from a small abnormal combustion in an abnormal combustion determination period for maximizing a dynamic range of an AD conversion circuit and for securely detecting a change of waveform amplitude in case of gain switching in an abnormal combustion detection operation.