Matthias Mrosek

Control Oriented NOx and Soot Models for Diesel Engines

Abstract The further improvement of Diesel engine control and diagnosis requires information on the dynamical soot and NO x formation. Investigations of the air and exhaust path show that process and sensor dynamics play an important role for emission modelling. The simplified combustion process and the emission formation is modelled as a stationary batch process. The air path states and the location of mass fraction burned 50% introduce external dynamics to the stationary model structure. It is shown that the main dynamic influences in emission formation come from the air path states at the engine intake. Additional dynamics result from the gas propagation in the exhaust system and the emission sensors. The presented emission models overcome the measurement dynamics leading to relatively fast dynamic models.

Identification of Emission Measurement Dynamics for Diesel Engines

Abstract Dynamic emission models for Diesel engines are important for future engine development. Emission formation takes place in the cylinder, while the emissions are usually measured downstream the exhaust pipe. Besides operation point dependent gas transportation delays the emission sensors themselves possess a significant dead time and sensor time constant varying for different measured quantities. These sensor individual dynamic measurement characteristics complicate the chronological assignment of cause and effect in emission modelling. Therefore the dynamic characteristics of a NO x , a micro soot sensor and an opacimeter are investigated. Models for the measurement dynamics are derived to separate the measurement dynamics from the engine dynamics. Hence excitation signals which strongly excite the emission formation and only weakly excite the intake and exhaust system are presented. Model results for the measurement dynamics are shown and validated with testbed data.

On the Parametrisation of Turbocharger Power and Heat Transfer Models

Abstract A semi-physical turbocharger power and heat transfer model built in a CR-Diesel engine is presented. The model is based on physical parameters described by Eulers equation. For the dependency of the turbine power from the VGT-actuator a polynomial approach is chosen. A method for measurement and model parametrisation separating aerodynamic power from heat transfer is given. Further an analytical analysis for choosing ramp times of quasi stationary measurements is included. The model quality and the proportion of heat transfer in the measured temperatures is demonstrated with measured data from the testbed. Finally the parameters of the modelled GT1749MV turbocharger are included in this contribution.

Stationary Global-Local Emission Models of a CR-Diesel Engine with Adaptive Regressor Selection for Measurements of Airpath and Combustion

Abstract A model structure for stationary emission models is presented. The emissions NO x , soot and opacity are separately modeled. Model inputs are the air mass flow rate, charge air pressure, intake temperature, the location of mass fraction burned 50% and the engine operation point. Local polynomials are trained for each operation point, defined by engine speed and injection quantity. To increase accuracy a selection algorithm of the significant regressors is presented. The local models are composed by means of weighting functions, depending on the engine operation points, to global emission models. For a rasterized operation range, the weighting can be interpreted as a linear interpolation of local models. This enables an easy implementation to common electronic control units (ECUs). Measurements from a CR-Diesel engine show the quality of the models.

Model-Based Optimisation of a Step in Acceleration for a CR-Diesel Engine

Abstract Due to more and more stringent emission regulations the optimisation of transient engine operation becomes necessary for future Diesel engine developments. Exemplary for the transient operation a step in acceleration pedal is investigated and optimised with respect to the engine emissions. This gives insights about the emission formation at transient driving and a benchmark for the design of open and closed-loop controls. A model structure to simulate the engine emissions and the engine torque is presented. It consists of a dynamical mean value air path model and a stationary combustion model. Thus the relevant outputs NO x , soot and torque are simulated with respect to the engine actuators. For optimisation the calibrated emission values for steady state are regarded. The actuators of the air path and the crank angle of the main injection are optimised such that the emissions follow a desired trajectory. The results are compared to a non-optimised step in acceleration and to a nonlinear closed loop control of the air path.

Dynamic Reference Value Generation for the Control of a Diesel Engine With HP- and LP-EGR

A combination of a low-pressure EGR and a high-pressure EGR for Diesel engines can effectively reduce the NOx emissions. In comparison to a conventional high-pressure EGR, the combination with a low-pressure EGR introduces an additional degree of freedom for the air path control. From control perspective the weaker couplings with the charging pressure and the dynamics of the gas composition in the intake and exhaust system are the major differences between the low-pressure and the high-pressure EGR. The lower gas temperature of the low-pressure EGR further reduces the emissions. A control oriented model is presented to control the gas composition in the intake system. Therefore a reference value transformation converts a desired air mass flow rate into a desired gas composition in the intake system. Depending on the dynamical gas compositions in the intake and exhaust system, the reference value of the desired gas composition results in a setpoint for a high-pressure EGR mass flow rate controller. Due to the faster dynamics of the high-pressure EGR, this controller accounts for the fast dynamical effects in the gas system. The presented control structure in combination with the reference value generation is invariant to model and sensor uncertainties and results stationary in an air mass flow rate control. As additional control variable, the intake temperature is controlled by the low-pressure EGR mass flow rate. A calibrated desired temperature delivers the setpoint for a low-pressure EGR mass flow rate controller.Copyright

A Global-Local Emission-Model for NOx and Soot Emissions of Turbocharged CR-Diesel Engines

Stationary and dynamic models for the emissions of a CR-Diesel engine are developed using a global-local model approach. Results for the NOx and soot emissions are presented. All model inputs are measurable air path states and combustion parameters. They determine the emission formation before the combustion takes place. Therefore the model can be used for emission prediction and simulation. The combustion process is regarded as a batch process, such that the dynamics are introduced as external dynamics to the model via the inputs. Thus a stationary model structure can be applied. As the space of possible air path states varies widely for different engine operation points, several input and output transformations are given that linearize the input and output space. This improves the model quality and extends the operation range of the model. Modeling results are shown for stationary and dynamic data as well as for local and global model operation.Copyright

System Properties and Control of Turbocharged Diesel Engines with High and Low-Pressure EGR

An extension of the air- and exhaust-system with a two path EGR-system consisting of a conventional cooled high-pressure EGR and a cooled low-pressure EGR has the potential to significantly reduce the NOx-emissions. Model based control structures and model based controller calibration can handle the increasing complexity of the air-system. An automated controller calibration based on a semi-physical mean value model of reduced complexity is presented. The system configuration of a two path EGR system is introduced. Its static and dynamic properties are investigated. Additional to the static couplings in the classical air-path new couplings appear. Also the systems dynamic properties are investigated. A decentralised gain scheduled PI(D)-control approach is chosen to control the variables air mass flow rate, high-pressure EGR mass flow rate and charge-air pressure. The controller maps depend on the engine operation point and are calibrated by a local linearisation of the semi-physical model. Couplings resulting on the low-pressure EGR-path are compensated by a semi-physical feed forward control.