Christopher H. Onder

Control of an SCR catalytic converter system for a mobile heavy-duty application

Selective catalytic reduction (SCR) is well known for exhaust gas aftertreatment in power plant applications. In the near future, it will be introduced in Europe in mobile heavy-duty diesel applications. Stringent specifications and the dynamic operation mode of such applications demand advanced control strategies. Such a control strategy is presented here. It incorporates a model-based feedforward controller (FFC) which handles the known dynamics of the plant. It further contains a feedback controller (FBC) to compensate for disturbances and slowly varying parameters. The realization of the feedback control loop is possible only due to the use of a nitrogen oxide (NO/sub x/) sensor which is cross-sensitive against ammonia (NH/sub 3/), and the implementation of a procedure separating the detection of NO/sub x/ and NH/sub 3/.

Control of a Urea SCR Catalytic Converter System for a Mobile Heavy Duty Diesel Engine

An advanced controller for a urea SCR (Selective Catalytic Reduction) catalytic converter system for a mobile heavy-duty diesel engine is presented. The after-treatment system is composed of the injecting device for urea solution and a single SCR catalytic converter. The control strategy consists of three parts: A primary feedforward controller, a surface coverage observer, and a feedback controller. A nitrogen oxide (NO x ) gas sensor with non-negligible cross-sensitivity to ammonia (NH 3 ) is used for a good feedback control performance. The control strategy is validated with ESC and ETC cycles: While the average NH 3 slip is kept below 10 ppm, the emission of NO x is reduced by 82%.

Fuel-optimal control of CVT powertrains

Abstract Continuously Variable Transmissions (CYTs) offer the potential to improve the part-load fuel efficiency of Spark-Ignited (SI) engines by shifting the operating points towards higher loads and lower speeds. The control of CVTs has traditionally been designed using (quasi) static arguments, i.e., by identifying the best efficiency points in the engine map for each constant power requirement and by following that curve using some heuristics as much as possible also in transients. In this paper a complete analysis and solution of the fuel-optimal control problem for transient conditions is presented. The powertrain equations include a detailed engine and CVT model. Further a physically meaningful optimization criterion is defined. The optimal solution is found using the numerical optimization package DIRCOL. Based on this optimal solution a simplified control strategy is proposed which offers almost the same fuel economy benefits. Connections of this approach to well-known CVT control strategies are shown.

Modelling and optimizing two- and four-stroke hybrid pneumatic engines

Abstract Hybrid pneumatic engines, which are designed to follow the downsizing and supercharging paradigm, offer a fuel-saving potential that is almost equal to that of hybrid electric powertrains while inducing much lower additional mass and cost penalties. This paper presents a systematic optimization of the operation of such an engine system. Both two-stroke and four-stroke modes are analysed. The optimized valve and throttle actuation laws for all modes and operating areas lead to generic maps that are independent of the engine size. So far, the pneumatic hybridization of internal combustion engines was thought to require two-stroke operation. This paper presents a novel hybrid pneumatic engine configuration that entails fixed camshafts for both intake and exhaust valves while utilizing variable valve actuation for one charge valve per cylinder only. This configuration is operated entirely in four-stroke modes. Such a configuration requires a careful optimization of its operating strategy to achieve its fuel economy potential. Compared with a full two-stroke operation, only small efficiency losses result from using four-stroke modes with these new operating strategies. Initial measurement results with such an engine system are presented in this paper to confirm the validity of the principles of operation.

On the power split control of parallel hybrid vehicles: from global optimization towards real-time control

Abstract In this paper, the optimal power split control law of a parallel hybrid powertrain is calculated for various driving conditions. It is shown that this optimal feedforward control law corresponds to a real-time control design based on the concept of equivalence factors. Certain properties of these equivalence factors are presented, which will lead to the design of a real-time controller.

Real-time model for the prediction of the NO x emissions in DI diesel engines

This paper describes the development of a real-time model for the prediction of the NOx emissions in DI diesel engines.

Model-Based Actuator Trajectories Optimization for a Diesel Engine Using a Direct Method

This paper proposes a novel optimization method that allows a reduction in the pollutant emission of diesel engines during transient operation. The key idea is to synthesize optimal actuator commands using reliable models of the engine system and powerful numerical optimization methods. The engine model includes a mean-value engine model for the dynamics of the gas paths, including the turbocharger of the fuel injection, and of the torque generation. The pollutant formation is modeled using an extended quasi-static modeling approach. The optimization substantially changes the input signals, such that the engine model is enabled to extrapolate all relevant outputs beyond the regular operating area. A feedforward controller for the injected fuel mass is used to eliminate the nonlinear path constraints during the optimization. The model is validated using experimental data obtained on a transient engine test bench. A direct single shooting method is found to be most effective for the numerical optimization. The results show a significant potential for reducing the pollutant emissions during transient operation of the engine. The optimized input trajectories derived assist the design of sophisticated engine control systems.

Engine thermomanagement with electrical components for fuel consumption reduction

Abstract This paper proposes a solution for advanced temperature control of the relevant temperature of a combustion engine. It analyses the possibility of reducing vehicle fuel consumption by improving engine thermomanagement. In conventional applications, combustion engine cooling systems are designed to guarantee sufficient heat removal at full load. The cooling pump is belt-driven by the combustion engine crankshaft, resulting in a direct coupling of engine and cooling pump speeds. It is dimensioned such that it can guarantee adequate performance over the full engine speed range. This causes an excessive flow of cooling fluid at part-load conditions and at engine cold-start. This negatively affects the engine efficiency and, as a consequence, the overall fuel consumption. Moreover, state-of-the-art cooling systems allow the control of the coolant temperature only by expansion thermostats (solid-to-liquid phase wax actuators). The resulting coolant temperature does not permit engine efficiency to be optimized. In this paper, active control of the coolant flow as well as of the coolant temperature has been realized using an electrical cooling pump and an electrically driven valve which controls the flow distribution between the radiator and its bypass. For this purpose, a control-oriented model of the whole cooling system has been derived. Model-based feedforward and feedback controls of coolant temperature and flow have been designed and tested. With the additional actuators and the model-based control scheme, a good performance in terms of fast heat-up and small temperature overshoot has been achieved. The improvements in fuel consumption obtained with the proposed configuration have been verified on a dynamic testbench. Both engine cold-start under stationary engine operation and the European driving cycle MVEG-A with engine cold-start were tested. The fuel consumption reductions achieved during these tests vary between 2.8 and 4.5 per cent, depending on the engine operating conditions. Compared to vehicle mass reduction or internal engine improvements, engine thermomanagement is a simple, flexible and cost efficient solution for improving system performance, i.e. fuel consumption.

A Real-Time Soot Model for Emission Control of a Diesel Engine*

Upcoming stringent emissions legislations more and more require feedback control of diesel engines raw emissions. For controller design, control oriented, easily identifiable, and portable models of the plant are needed. This paper presents a novel model for diesel engines particulate matter (PM) emissions that aims to achieve the aforementioned requirements. The PM emissions are modeled as relative deviations of stationary base maps. A polynomial approach is used to estimate the influence of the deviation of each input on the PM emissions. The model is easily extendable and can be refined to the users needs.

Engine Emission Modeling Using a Mixed Physics and Regression Approach

This paper presents a novel control-oriented model of the raw emissions of diesel engines. An extended quasistationary approach is developed where some engine process variables, such as combustion or cylinder charge characteristics, are used as inputs. These inputs are chosen by a selection algorithm that is based on genetic-programming techniques. Based on the selected inputs, a hybrid symbolic regression algorithm generates the adequate nonlinear structure of the emission model. With this approach, the model identification efforts can be reduced significantly. Although this symbolic regression model requires fewer than eight parameters to be identified, it provides results comparable to those obtained with artificial neural networks. The symbolic regression model is capable of predicting the behavior of the engine in operating points not used for the model parametrization, and it can be adapted easily to other engine classes. Results from experiments under steady-state and transient operating conditions are used to show the accuracy of the presented model. Possible applications of this model are the optimization of the engine system operation strategy and the derivation of virtual sensor designs.