A particulate matter On-Board Diagnostics method based on temperature sensing is demonstrated. The concept applies a detection filter downstream of the main particulate filter and a flow diversion pipe. A small fraction of the main exhaust flow is diverted through the detection filter. In case the main soot filter has some leakage, soot will collect on the detection filter where it reduces the filter's permeability. As a result the diverted flow is reduced. This effect is sensed by a temperature sensor placed downstream of the detection filter because the change of diverted mass flow results in a change of heating rate. This principle allows particulate filter diagnostics based on cost-effective and readily available sensing technology.
Comprehensive diagnostics software is developed to interpret and assess the temperature signal. The developed diagnostics software detects particulate filter filtration inefficiency and performs plausibility checks. The concept is demonstrated using an instrumented test vehicle with purposely damaged particulate filter. The diagnostics prove successful in detecting a filtration inefficiency fault that leads to particulate matter emissions close to the 12 mg/km 2017 Euro 6 OBD Threshold Limit.
