Nonlinear Model Predictive Control for the Starting Process of a Free-Piston Linear Generator

Abstract

Free-piston linear generators (FPLG) attract a lot of attention and are under ongoing investigation due to their fuel efficiency, low emissions and the compact design as generator unit. The main characteristic of FPLGs is the absence of a crankshaft, which poses a major challenge, because the piston moves freely. Hence, the locations of top dead center (TDC) and bottom dead center (BDC), have to be controlled precisely. In this contribution, an approach for modeling and control of a FPLG is presented. The combustion cylinder and the bouncing chamber on the opposite side are described with a physics-based, continuous-time thermodynamic model. For the starting process of the FPLG a nonlinear model predictive controller (NMPC) with multiple shooting discretization is designed for a safe and reliable starting process.