Revisão e proposta de estratégia de controle de movimento para um gerador linear a ímã permanente movido a pistão livre para regime permanente

Abstract

This work investigates motion control in a free-piston linear generator (FPLG), with the objective of regulating electromagnetic energy extraction in order to ensure stable operation within mechanical limits and adequate performance in electrical power generation. For this purpose, the system is modeled as a combustion-excited mass–spring oscillator in which the electromagnetic force is represented as an equivalent damping proportional to the piston velocity, considering an electrical architecture composed of passive three-phase rectification followed by a DC–DC boost converter. Three control strategies are developed and evaluated under the same modeling and excitation conditions: (i) proportional–integral control with peak displacement detection, (ii) control based on the mechanical energy of the cycle, and (iii) nonlinear model predictive control (NMPC). The comparison is carried out in terms of piston stroke, oscillatory regime stability, energy balance, and DC power delivered to the load. The results show that PI control with peak detection achieves good steady-state performance, but with higher latency under disturbances; the mechanical-energy-based control regulates energy extraction throughout the oscillation cycle, contributing to stroke containment and robustness to combustion variations; and NMPC enables explicit handling of operational constraints, at the cost of increased command modulation and lower uniformity of the electrical power in the considered architecture. It is concluded that the strategies present different trade-offs between mechanical stability, robustness, and energy utilization, providing a comparative basis for controller design in FPLGs.