Model Based Control of Turbochargers: Application to a Diesel HCCI Engine

Abstract

The recent developments in Diesel engines tend towards new types of combustion, such as Homogeneous Charge Compression Ignition (HCCI) which looks promising with respect to the pollutant emissions. However, these new technologies require a faster and more accurate control of the gas mixture in the cylinder due to its higher sensitivity to thermodynamic conditions and composition. A major issue in the development of these new types of Diesel engines lies in the architecture and the control of the air intake system. In this context many setups are envisaged, and in particular the turbocharging systems are becoming more and more complex: variable geometry turbines, double stage turbochargers, variable geometry compressors. The associated control laws have to be modified: the conventional strategies based on steady static maps and proportional integral controllers have to be improved in order to address the new challenges. This paper proposes a model based control strategy for a variable geometry turbocharger. This strategy is based on a physical representation of the system (turbocharger, intake and exhaust manifolds). The approach has two main advantages: it is easy to calibrate, and it can be adapted to other types of architecture. The first part of this paper describes the architecture of the system and its model. The second part details the strategies designed and the results carried out in simulation and on an engine test bed.

Control Oriented Model of a Variable Geometry Turbocharger in an Engine with Two EGR Loops

“…This work complements previous works already published or submitted ( [3,4] and [1]). Experimental validation results are presented, justifying the assumptions made in the model reduction process.…”

“…In [3], it was applied to gasoline engines fitted with fixed geometry turbines. The application to variable geometry turbines was first tried in [4] where it was validated mostly outside the EGR operating area. The purpose in this paper is to extend this approach, and to show that the model proposed can easily be adapted for a system with two EGR circuits.…”

Simulation Support for Control Issues in the Context of Modern Diesel Air Path Systems

“…The model-based control laws studied in this section are described in [4]. A control strategy based on a physical model of the turbocharger system is proposed.…”

“…For all these reasons, the standard linear controller cannot be implemented without a large calibration effort. In this context, the model-based EGR and turbocharger control are preferred to deal with these issues [4].…”

“…Even if some of those tests (1, 2) could have been performed on a real test bed, the use of simulation has provided a way of accelerating and facilitating the development process. However, in some cases, the tests would not have been possible on a real engine: it would either require damaging some components (3), or a very high number of tests (4,5). As a matter of fact, the use of simulation tools for those tests is not only necessary, but also provides information that would not be available otherwise.…”