Model Based Diagnosis of the Intake Manifold Pressure on a Diesel Engine
Stronger environmental awareness as well as actual and future
legislations increase the demands on diagnosis and supervision of any
vehicle with a combustion engine. Particularly this concerns heavy
duty trucks, where it is common with long driving distances and large
engines. Model based diagnosis is an often used method in these
applications, since it does not require any hardware redundancy.
Undesired changes in the intake manifold pressure can cause increased
emissions. In this thesis a diagnosis system for supervision of the
intake manifold pressure is constructed and evaluated. The diagnosis
system is based on a Mean Value Engine Model (MVEM) of the intake
manifold pressure in a diesel engine with Exhaust Gas Recirculation
(EGR) and Variable Geometry Turbine (VGT). The observer-based
residual generator is a comparison between the measured intake
manifold pressure and the observer based estimation of this
pressure. The generated residual is then post treated in the CUSUM
algorithm based diagnosis test.
When constructing the diagnosis system, robustness is an important
aspect. To achieve a robust system design, four different observer
approaches are evaluated. The four approaches are extended Kalman
filter, high-gain, sliding mode and an adaption of the open model. The
conclusion of this evaluation is that a sliding mode approach is the
best alternative to get a robust diagnosis system in this
application. The CUSUM algorithm in the diagnosis test improves the
properties of the diagnosis system further.
Christoffer Bergström and Gunnar Höckerdal
2009
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