Exhaust Gas Filter Diagnosis via Pressure Quotient Feedback
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Solution Overview
Problem
Existing methods for diagnosing the state of a particle filter in exhaust gas cleaning devices are not reliable, as they are prone to errors due to component tolerances and dynamic operating conditions, leading to inaccurate determination of pressure losses and filter loading.
Innovation Solution
The method involves bandpass filtering and squaring of actual and model pressure loss values to form integral values, which are then used to calculate a pressure quotient, allowing for a more accurate diagnosis of the particle filter's state by accounting for component offsets and noise, and integrating values only under specific conditions to minimize short-term disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If actual pressure loss is determined using pressure sensors, then the state of the particle filter can be monitored, but component tolerances and dynamic operating conditions cause measurement errors reducing diagnosis reliability
Solution Approach 1:
The patent implements a feedback mechanism by continuously comparing the actual pressure loss (measured by sensors) with a model pressure loss (calculated from exhaust gas mass flow and temperature). This comparison generates a pressure quotient that feeds back into the diagnostic system, allowing continuous monitoring and correction of measurement deviations caused by component tolerances and dynamic operating conditions.
Solution Approach 2:
The patent transforms the raw pressure loss measurement into a dimensionless pressure quotient by dividing actual pressure loss by model pressure loss. This parameter transformation normalizes the data, making the diagnostic system insensitive to absolute pressure variations caused by component tolerances and enabling reliable diagnosis across different operating conditions.
2Productivity
If pressure quotient is calculated directly from actual and model pressure loss values, then diagnosis can be performed quickly, but short-term disturbances and noise lead to inaccurate results
Solution Approach 1:
The patent applies preliminary actions by bandpass filtering and squaring the pressure loss values before calculating the pressure quotient. These preprocessing steps remove short-term disturbances and noise from the raw measurements, ensuring that the subsequent quotient calculation is based on smoothed, reliable data while maintaining real-time diagnostic capability.
Solution Approach 2:
The patent introduces intermediate processing steps (bandpass filtering and squaring operations) as mediators between the raw pressure measurements and the final pressure quotient calculation. These intermediary operations act as a buffer that eliminates high-frequency noise and short-term disturbances while preserving the essential diagnostic information.
3Reliability
If pressure sensors are used to monitor particle filter loading, then filter state can be determined, but component offsets cause systematic errors in pressure loss determination
Solution Approach 1:
The systematic errors from pressure sensor offsets are compensated through feedback comparison with the model pressure loss. The model, which is calculated from exhaust gas mass flow and temperature without direct pressure sensor input, serves as a reference that cancels out systematic measurement errors when forming the pressure quotient.
Solution Approach 2:
The patent changes the measurement parameter from absolute pressure loss to a relative pressure quotient. This transformation eliminates the influence of constant offset errors in the pressure sensors, as the quotient of actual to model pressure loss remains accurate even when both measurements contain systematic offsets.
Data Source
Figure 1
AI summary
The invention relates to a method for operating an exhaust gas purification device with a particulate filter, wherein an actual pressure loss across the particulate filter is determined by means of pressure sensors. It is provided that a model pressure loss is determined based on at least one state variable, and a pressure ratio is calculated from the actual pressure loss and the model pressure loss. In a diagnostic mode, the condition of the particulate filter is determined based on this pressure ratio. The invention further relates to an exhaust gas purification device.