Modeling and Identification of Electro-pneumatic VNT Actuator for Simulation and Control A. Mehmood * S. Laghrouche * M. El Bagdouri * * Laboratoire S.E.T, Universite de Technologie de Belfort-Montbeliard, Belfort, France.( e-mail: adeel.mehmood@utbm.fr, salah.laghrouche@utbm.fr, mohammed.el-bagdouri@utbm.fr). Abstract: An accurate non-linear model based control of the electro-pneumatic actuator adjoined to a Variable Nozzle Turbocharger (VNT) is proposed in this paper. Electro-pneumatic actuator is composed of electro-pneumatic pressure converter (EPC) coupled to pneumatic actuator. A precise physical model which captures fundamental dynamics of pneumatic actuator and its interaction with EPC is proposed. Dynamics of the pressure inside the actuator chamber are modeled, considering variation in volume and the temperature, along with EPC controlled air mass flow to the actuator. Modeling of air-leakage phenomenon in the EPC is also addressed. Comparison between simulation and experimental results shows the effectiveness of the proposed model. 1. INTRODUCTION In compliance with the new laws of pulsion control and better performance, turbocharger control is essential re- quirement of the automotive industry. Electro-pneumatic actuators are widely used for the control of Variable Nozzle Turbocharger (VNT). Their high power to weight ratio and low cost make them more useful for automotive industry, robotics and many other industrial applications ( See for example Wang et al. [2007] and Garrett et al. [2001]). VNT is a special type of turbocharger that can regulate air charge, by changing the opening angle of its vanes. Electro pneumatic actuator is connected to these vanes via rotating unison ring that actuates all vanes together. Electro-pneumatic actuators are the unification of electro- pneumatic pressure converter (EPC) and pneumatic actu- ators. Pressure inside the pneumatic actuator is controlled with the help of EPC. See Fig.1 for more comprehension. EPC, a solenoid actuator, connect the pneumatic actuator chamber either with source reservoir (vacuum) or with atmosphere. This paper concerns with the application of the Electro-pneumatic actuators for the VNT. In the literature, physical models for EPC and pneumatic actuators are addressed separately. kotwicki and Russell [1998] proposed an adiabatic thermodynamic vacuum ac- tuator model for pneumatic actuator without considering its interaction with EPC. Carneiro and Almeida [2006] pre- sented and compared different thermodynamic models for pneumatic actuator chamber (See also White [1994]). But, dynamics of the diaphragm and EPC were not considered. Simplified model of temperature and air mass flow are also presented, in Messina et al. [2005], Smaoui et al. [2005] and Laghrouche et al. [2005], to propose different control laws. Physical models, based on solenoid actuators, for the EPC are discussed in the work by Taghizadeh et al. [2009] and Topcu et al. [2006]. To avoid parameter identification, a static model for magnetic force acting on the EPC is proposed by Galindo et al. [2009]. In his work, several characterization tests were performed to obtain relevant information from the vacuum system. Galindo et al. [2009] also proposed 1D model of vacuum circuit but the physical model was developed with some assumption like constant volume and temperature within the pneumatic actuator. Leakage phenomenon is not addressed in any of these works. An accurate model of VNT system is presented, that captures fundamental dynamics of the actuator and inter- action between its subsystems (EPC and pneumatic ac- tuator). Experiments were carried out to determine static model for magnetic force as a function of PWM. This force controls effective air mass flow area between atmosphere, actuator and reservoir chamber. Effective flow area is also parameterized, as a function of plunger position, from mechanical equation of the EPC (plunger). Variation in the actuator pressure is also considered into account by considering variable volume, temperature and air mass flow. Moreover, air-leakage phenomenon in the EPC which is due to flaws in the sealing is also considered in this work. The paper is organized as follow; In the section II work- ing and parameter identification of the electro-pneumatic pressure converter is discussed. Physical modeling of the pneumatic actuator along with dynamics of pressure, air mass flow area and leakage phenomenon is addressed in section III. In section IV, simulation results are compared with measurements obtained from experimental setup. It is shown that simulation results predict the experimental results with accuracy. At the end, Some simplifications are proposed to adopt the model for control. 2. SYSTEM MODELING EPC controls pressure in the pneumatic actuator. Due to change in pressure in the pneumatic actuator diaphragm moves back and forth to open vanes of the turbocharger. 8th IFAC Symposium on Nonlinear Control Systems University of Bologna, Italy, September 1-3, 2010 978-3-902661-80-7/10/$20.00 © 2010 IFAC 897 10.3182/20100901-3-IT-2016.00264