A Novel Force Control Method for Dead Centers Tracking of Free-Piston Linear Generator

Free-piston linear generator (FPLG) has attracted wide attention for its potential in electric vehicle applications. A significant characteristic of FPLG is that it cancels the crank-slider mechanism, allowing variable compression ratio and higher overall efficiency. However, the absence of mechanical limits makes the stable operation of engine so difficult. The control of piston motion needs to conquer the frequent combustion variations to ensure accurate dead center positions so that the engine can continuously stay within the normal operating range. This paper proposes a force control method for the linear generator of FPLG to accurately maintain the dead centers. The control variables are obtained through modeling of the piston motion profiles. The electromagnetic force of LEM is regulated by specifying the q-axis reference current through feedback mechanism. The control effect of the control scheme was verified through experimental tests.