Particulate Matter Sensor Diagnostics via Resistance Phase Analysis
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Solution Overview
Problem
Existing particulate sensors face challenges in accurately distinguishing between various operating states, such as faulty, normal, false positive, and actual soot particulate states, due to similar resistance readings caused by soot accumulation, water vapor condensation, and electrical issues.
Innovation Solution
A diagnostic method and system that detects water vapor condensate between electrodes, subjects it to evaporation conditions, and measures resistance changes to determine the sensor's working condition, with secondary diagnostics involving heat application to differentiate between substrate heating and cooling responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a particulate sensor measures electrical resistance between electrodes to detect soot accumulation, then the sensor can monitor particulate matter levels, but it cannot distinguish between different causes of resistance changes (soot accumulation, water vapor condensate, electrical faults)
Solution Approach 1:
The diagnostic process is segmented into multiple distinct phases: initial resistance measurement, heated resistance measurement, and cooled resistance measurement. Each phase provides specific information about different aspects of sensor condition, allowing the system to distinguish between soot accumulation, water condensate, and electrical faults based on the pattern of resistance changes across phases.
Solution Approach 2:
The sensor operating parameters are dynamically changed by controlling the temperature of the sensor substrate through the heater element. By measuring resistance at different temperature states (cold, heated, cooled), the system exploits the different thermal responses of soot, water condensate, and electrical components to identify the actual cause of resistance changes.
2Ease of operation
If the sensor heater is activated to burn off soot particulates and reset the sensor, then the sensor returns to a clean state, but the high resistance reading after cleaning is indistinguishable from an electrical open circuit fault
Solution Approach 1:
Before attempting to diagnose a fault or reset the sensor, the system performs preliminary actions by measuring resistance in multiple temperature states. This preliminary diagnostic measurement pattern allows the system to distinguish between a clean sensor state and an electrical fault state before any reset operation is performed, preventing misdiagnosis and inappropriate reset operations.
Solution Approach 2:
The system uses feedback from the resistance measurements taken during heated and cooled states to determine the appropriate action. If the resistance pattern matches that of a clean sensor, the system confirms proper operation; if it matches an electrical fault pattern, the system identifies the fault without incorrectly triggering a reset, thereby improving reliability.
3Measurement precision
If the sensor presents low resistance due to water vapor condensate on electrodes, then the sensor indicates soot accumulation (false positive), but applying heat to evaporate the condensate uses additional energy and time
Solution Approach 1:
The system applies partial heating - just enough to evaporate water condensate and observe the resistance response, rather than excessive heating used for complete soot burnoff. This partial action is sufficient to distinguish water condensate from soot accumulation while consuming minimal energy and time, addressing the false positive issue without excessive energy expenditure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately diagnoses the operating condition of particulate sensors, differentiating between proper functioning and failure states, thereby enhancing the reliability of particulate matter detection and emission monitoring.
Implementation Method 1
subjecting the sensor to conditions sufficient to evaporate any water vapor condensate
Implementation Method 2
detecting whether Relect increases in a manner consistent with evaporation of water vapor condensate
Implementation Method 3
providing heat to the sensor in an amount sufficient to modify the electrical resistance of the substrate
Implementation Method 4
removing the heat provided in step (d) to cool the substrate; detecting whether Relect changes in a manner consistent with cooling of the substrate
Implementation Method 5
The operating principle of the particulate sensor is based on the conductivity of the particulates (e.g., soot) deposited on (or over) the sensing electrodes
Data Source
AI summary
A diagnostic method and system is described for diagnosing an operating condition of a conductive particulate matter sensor. The sensor has a substrate and two electrodes on the substrate adapted to collect particulate matter between the electrodes, thereby establishing an electrically conductive path through collected particulate matter between the electrodes that can be detected by measuring electrical resistance between the electrodes, Relect. The diagnosis is performed by detecting whether water vapor condensate may be present between the electrodes and if it is, then measuring resistance between the electrodes while subjecting the sensor to conditions sufficient to evaporate any water vapor condensate and diagnosing a validation that the sensor is in proper operating condition if resistance increases in a manner consistent with evaporation of condensate.