Trajectory-Regulation-Based Segmented Control for Dead Center Positions Tracking of Free-Piston Linear Generator

Abstract

Free-piston linear generator (FPLG), as a novel energy converter, has attracted wide attention due to its unique operating characteristics. However, the high-precision and robust tracking of the dead center positions in the presence of frequent combustion variation is still a tricky problem. In this respect, in this article, we present a trajectory-regulation-based segmented control (TRBSC) to actively control the linear electric machine (LEM) of FP LG. The target stroke is divided into the high-speed zone and low-speed zone, where active tracking of the input reference trajectory of LEM and free damped motion are performed separately. Especially, the input trajectory is selected as a variable sinusoidal reference velocity profile, which is adjusted by the combinations of the dead center errors. The segmented control decouples the specific interaction between the dead center positions and velocity curve, reducing the heavy dependence of the algorithm on speed tracking accuracy. A full theoretical analysis is provided with emphasis on the regulation rules of the reference speed profile based on the modeling of the displacement profiles. The performance of the TRBSC is experimentally verified on an 18 kW permanent-magnet linear synchronous motor setup in motoring mode.