Stephan Stadlbauer

SCR Ammonia Dosing Control by a Nonlinear Model Predictive Controller

Abstract To deal with the demanding goals of the restricted Diesel emission legislation the focus in the application of exhaust after treatment systems to fulfill these strict requirements moves more and more to model based design, optimization and control. Against this background a nonlinear model predictive control (MPC) for an exhaust after treatment system consisting of a DOC (Diesel oxidation catalyst), a DPF (Diesel particulate filter) and a SCR (selective catalytic reduction) is proposed. Similar to standard ammonia control schemes also in this study the dosing amount is the only adjustable input variable. But in contrast to these usually simple feed forward dosing approaches in this proposal also information about the nonlinear temperature behavior and the storage effects of the SCR - included in a nonlinear SCR model - can be considered for the ammonia control. Based on these improved knowledge of the system a nonlinear model predictive controller, also applicable for real time tests on the engine, is applied for SCR control leading to promising results in simulation.

Fast Measurement of Soot by In-Situ LII on a Production Engine

The contribution of transient emissions to total emissions is becoming more important in view of the improvement of steady state emissions and after-treatment systems. For a critical pollutant, namely soot, there is no commercially available measurement system able to measure sufficiently fast on production engines. This paper presents a measurement setup based on in-situ Laser Induced Incandescence (LII) allowing high speed, frequent soot measurements in a production engine. The setup consists of a pulsed laser system, a fast optical detector and a special, compact designed in-situ optical LII probe which makes it possible to change the measurement location easily. System speed is assessed among other approaches, by using eleven well defined soot steps obtained by injection pulses under controlled conditions on a highly dynamic test bench. The effect of these pulses for a production four-cylinder 2 lt. Euro 5 Diesel engine is measured at three different positions (at tailpipe, downstream of the turbine and in exhaust manifold). The features of LII intensity are extracted by principle component analyses (PCA) and compared with a fast and commercially available device (AVL Opacimeter) at last. The results show that the measurements with the proposed setup are able to detect all peaks in contrast to the commercially available device.Copyright

Indicated pressure-based data-driven diesel engine NOx modeling

This article addresses the design and evaluation of virtual NO x sensors for heavy-duty off-road diesel engines based on static polynomial black box modeling. Three approaches, differing in the chosen sets of regressors, are analyzed regarding their NO x prediction capability. As regressor sets only quantities available on standard production-type electronic control units, features extracted from the in-cylinder pressure trace via singular value decomposition extended by the engine speed as well as geometric values from the pressure trace and heat release curves are utilized, respectively. It is shown that while each of the approaches alone has its drawbacks, a systematic combination, especially of the first two methods, results in high-accuracy NO x models while at the same time keeping the number of regressors low.

Validation of a virtual control oriented cylinder selective soot sensor

The improved steady state performance of engine control and aftertreatment makes the transient contribution to the total emissions increasingly important. As several control mechanism, e.g. the exhaust recirculation, are set for all cylinders at a time, misbalancing represents a practical limit to the achievable emission control. This paper tackles both issues at a time using a virtual soot sensor. The virtual soot sensor is based on piecewise principal components analysis (PCA) of the in-cylinder pressure measurements and on their representation by a polynomial structure which has been proposed in a previous work. The peaks detected by sensor during transient working condition cannot be confirmed as standard PM or soot measurement systems are too slow. In this paper we use an in-situ laser induced incandescence (LII) system to provide a fast soot reference and to validate the performance of the virtual soot sensor. The results confirm the ability of the proposed virtual sensor to recognize soot changes - also between individual cylinders - with sufficient speed without requiring any additional hardware.

Improving the transient emission performance of a Diesel engine by input shaping techniques

Caused by the demanding and more and more stringent legislated emission limits for passenger car engines, the effect of transient emission peaks becomes more and more important for the overall emission limits. In case of Diesel engines, the two main concerned pollutants are NOx and PM and typically the compliance with the legislation is achieved by a suitable control of the fuel and air system of the engine. Especially during transients the coordination of both loops is crucial for the overall performance. Typically the control is separated in the two loops, where coupling effects and different time scales and dynamics can lead to undesired overshoots during transients. Against this background in this work an input shaping technique to reduce the transient emission peaks is proposed. The input shaping is based on an identified response model of the transient emission profile and used to determine suitable correction trajectories which can be applied to an existing calibration and reduce undesired effects during transients while allowing to keep the base calibration and control structure of the engine control unit. In this study input shaping is applied for the rail pressure and injection parameters to reduce the NOx emissions while the PM emissions, efficiency and noise levels should be kept similar to the nominal operation. The proposed strategy is evaluated on a 2l turbocharged common rail passenger car Diesel engine mounted at a dynamic engine testbench and promising results are achieved.

Design and Evaluation of Control-Oriented Diesel Oxidation Catalyst Models

Abstract This paper presents different strategies for Diesel Oxidation Catalyst (DOC) modeling. Starting from the commonly used approach of describing the chemical and energy balances by first principles and fitting a small set of parameters often unknown, special emphasis is placed on data driven DOC modeling. Considering black as well as grey box approaches it is shown that the data driven methods provide a better model quality and, in the specific case, are easier to fit since the considered model class are polynomial NARX models, which are linear in parameters.