Particulate Matter Sensor Verification via Elevated Voltage
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Solution Overview
Problem
Existing particulate sensors face challenges in distinguishing between faulty states, such as sensor poisoning by non-conductive contaminants, and normal states, especially when the diesel particulate filter (DPF) is functioning properly, leading to difficulties in accurately verifying sensor operation and DPF effectiveness.
Innovation Solution
A method involving the application of an elevated voltage to the sensor after DPF regeneration, monitoring resistance changes, and perturbing engine conditions to increase soot emissions for verification, allowing for accurate measurement of soot accumulation and differentiation between sensor states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DPF is functioning properly, then soot emissions are reduced to very low levels, but this makes it difficult to verify sensor operation and distinguish between sensor faults and normal operation
Solution Approach 1:
The system performs sensor verification at predetermined times (e.g., after DPF regeneration) when soot levels are naturally low, before normal operation begins. This preliminary verification captures the sensor's baseline performance when the DPF is functioning properly, enabling accurate fault detection during subsequent operation.
Solution Approach 2:
The verification process is executed periodically at specific intervals or conditions (such as after regeneration events), allowing repeated assessment of sensor functionality under known low-soot conditions. This periodic verification ensures continuous monitoring of sensor health while the DPF maintains proper function.
2Measurement precision
If the sensor is poisoned by non-conductive contaminants, then resistance between electrodes becomes very high, but this presents the same electrical signature as a properly operating sensor with low soot levels
Solution Approach 1:
The system introduces an intermediary verification process that uses electrical characteristics (such as capacitance or resistance change rates) to distinguish between high resistance caused by soot accumulation and high resistance caused by contaminant poisoning. This intermediary measurement method provides additional information that resolves the ambiguity between normal and faulty states.
Solution Approach 2:
The verification process monitors changes in electrical parameters (resistance, capacitance, or their rates of change) over time rather than relying on single-point measurements. By analyzing the dynamic behavior and rate of change of these parameters, the system can distinguish between legitimate soot-related resistance changes and abnormal resistance patterns indicative of sensor poisoning.
3Use of energy by moving object
If the sensor operates at nominal voltage, then energy consumption is low, but the sensor cannot accurately measure soot accumulation under certain operating conditions
Solution Approach 1:
The system dynamically adjusts the sensor's operating voltage based on verification needs and environmental conditions. During verification periods or when measurement accuracy is critical, the voltage is elevated to enhance soot detection sensitivity. During normal operation or when soot levels are high, the voltage returns to nominal levels to conserve energy, optimizing both accuracy and energy efficiency.
Solution Approach 2:
The verification method involves temporarily changing the electrical parameters (voltage level) of the sensor to improve measurement capability. By switching between nominal and elevated voltage states, the system can perform accurate verification measurements while maintaining low energy consumption during normal operation, thus resolving the contradiction between energy use and measurement precision.
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
This approach enhances the ability to verify proper sensor operation and detect soot levels even in low soot environments, reducing the risk of false fault indications and ensuring accurate DPF functionality assessment.
Implementation Method 1
The operating principle of the particulate sensor is based on the conductivity of the particulates (e.g., soot) deposited between the sensing electrodes. The electrical resistance between the sensing electrodes is relatively high when the sensor is clean but such resistance decreases as soot particulates accumulate.
Implementation Method 2
The electrical resistance between the sensing electrodes is relatively high when the sensor is clean but such resistance decreases as soot particulates accumulate.
Implementation Method 3
These sensors also have a heater that can be selectively activated to burn off the soot particulates to 'reset' the sensor to a known, base 'clean' state.
Data Source
AI summary
A method for verifying the validity of an output of a particulate matter sensor mounted in an engine exhaust system downstream of a diesel particulate filter, the particulate matter sensor including a pair of electrodes spaced apart from each other, includes initiating regeneration of the diesel particulate filter, applying and maintaining a higher than nominal voltage across the electrodes following the step of initiating regeneration of the diesel particulate filter, and measuring an electrical parameter across the electrodes while the higher voltage is applied across the electrodes, where the electrical parameter is indicative of an amount of soot accumulated on the sensor. The reading of accumulated soot is evaluated to determine whether the sensor is indicating that the amount of accumulated soot is within an expected range based on a clean diesel particulate filter and the elevated applied voltage.