Alois Amstutz

Control of diesel engines

This article is intended to give control engineers an overview of models and controls of diesel engines. The main emphasis is on the engines torque generation, including all necessary ancillary devices (turbocharger, injection-system, etc.), pollutant emission and model-based controls. The paper gives a brief introduction of the basic working principles and the salient features of diesel engines and their main differences to Otto (gasoline or spark-ignited) engines are shown. The most important control tasks are then identified and their implications on engine performance are analyzed. An overview of the current state-of-the-art in industrial diesel control applications is given. It also discusses models for the simulation of transient macroscopic effects, and how these models can be simplified to be useful for controller synthesis. Finally. an outlook on possible future control issues and their role in diesel engine evolution is presented.

EGO sensor based robust output control of EGR in diesel engines

In diesel engines, exhaust gas recirculation (EGR) is an efficient method for reducing NO/sub x/. EGR rates are commonly set according to the expected engine behavior, without considering the actual composition of the exhaust gases. In this paper, a new control system for EGR in passenger cars is presented, based on an exhaust gas oxygen (EGO) sensor as indicator of the combustion state as well as on a robust design approach to cope with the parameter variations. The proposed control has been designed for and tested on an Audi TDI engine and has been found to yield a similar performance as the conventional controllers for the standard engine, in spite of the transport delays between combustion process and measurement. Due to the presence of feedback, reduced sensitivity and/or detectability of wear, production irregularities, changes of operating conditions and calibration faults are expected from long-time measurements. >

CAE tools for quasi-static modeling and optimization of hybrid powertrains

Hybrid vehicles offer larger flexibility than conventional powertrains and, therefore, opportunities for improved fuel economy, but they need systematic design and optimization procedures to realize that potential. Especially choosing the best system structure, parametrization, and supervisory control algorithms is not trivial. This paper presents a tool which supports these tasks and which is based on a somewhat unusual system description. With this approach, fast simulations over entire test cycles are achieved on standard computer platforms. To demonstrate the benefits of the proposed tool, three case studies are shown, one including experimental data.

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.

A Novel Interface for Hybrid Mock Circulations to Evaluate Ventricular Assist Devices

This paper presents a novel mock circulation for the evaluation of ventricular assist devices (VADs), which is based on a hardware-in-the-loop concept. A numerical model of the human blood circulation runs in real time and computes instantaneous pressure, volume, and flow rate values. The VAD to be tested is connected to a numerical-hydraulic interface, which allows the interaction between the VAD and the numerical model of the circulation. The numerical-hydraulic interface consists of two pressure-controlled reservoirs, which apply the computed pressure values from the model to the VAD, and a flow probe to feed the resulting VAD flow rate back to the model. Experimental results are provided to show the proper interaction between a numerical model of the circulation and a mixed-flow blood pump.

A Physiological Controller for Turbodynamic Ventricular Assist Devices Based on a Measurement of the Left Ventricular Volume

The current article presents a novel physiological control algorithm for ventricular assist devices (VADs), which is inspired by the preload recruitable stroke work. This controller adapts the hydraulic power output of the VAD to the end-diastolic volume of the left ventricle. We tested this controller on a hybrid mock circulation where the left ventricular volume (LVV) is known, i.e., the problem of measuring the LVV is not addressed in the current article. Experiments were conducted to compare the response of the controller with the physiological and with the pathological circulation, with and without VAD support. A sensitivity analysis was performed to analyze the influence of the controller parameters and the influence of the quality of the LVV signal on the performance of the control algorithm. The results show that the controller induces a response similar to the physiological circulation and effectively prevents over- and underpumping, i.e., ventricular suction and backflow from the aorta to the left ventricle, respectively. The same results are obtained in the case of a disturbed LVV signal. The results presented in the current article motivate the development of a robust, long-term stable sensor to measure the LVV.

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.

Model-based feedback control of the air-to-fuel ratio in diesel engines based on an empirical model

This paper discusses the application of a model-based feedback control loop for the air-to-fuel (AF) ratio instead of the standard exhaust gas recirculation (EGR) control loop that utilizes the hot-film air-mass meter (HFM) as control variable. A comparison between the model-based controller that contains information about the plant dynamics and the standard EGR controller is carried out. In terms of performance and driveability the results of the AF ratio controller match those of a standard EGR controller. Moreover, with this new configuration, production tolerances and drift of sensors and actuators, such as the HFM and the injectors, can be detected and compensated. The starting point for the controller design is an empirical linear engine model with the EGR valve control signal as input signal and the AF ratio as the output signal

Modeling and model-based control of supercharged SI-engines for cars with minimal fuel consumption

One approach to realize spark ignited (SI) engines with very low fuel consumption is to use small displacements and boosting. For several reasons conventional turbochargers are not the best choice for such systems. Instead, pressure wave superchargers offer the potential for very fast and accurate load control. In this paper a control oriented model of such an engine system is presented. The model validation is described and the main nonlinearities are identified. Using this model, a suitable control structure is derived and verified by both simulations and measurements.

Control of diesel engines using NOx-emission feedback

Variations of engine-out emissions due to ageing, component drift or production tolerances pose serious problems to meet legislative restrictions on exhaust tailpipe pollutant emissions. This paper addresses feedback of the raw emissions for improved control of diesel engines. A discussion of issues regarding the inclusion of raw-emission feedback into the engine control structure is provided, and a novel control structure for combined feedback control of the air-path variables boost pressure and exhaust gas recirculation rate and of the NOx emissions is presented. The proposed control structure basically consists of an optimal linear output feedback controller and a setpoint-adaption loop on the exhaust gas recirculation rate. With this approach, a simple control structure is available requiring a marginal calibration effort to meet desired NOx-emission values. Unfavourable injection timing in connection with NOx control is minimized by adapting the exhaust gas recirculation rate setpoint. The performance of the proposed approach is demonstrated by experimental results.