Non-Linear and Multi-Domain Modelling of an Opposed-Piston Free Piston Engine during Motoring

Abstract

When coupling the Free Piston Engine (FPE) to the Permanent Magnet Linear Synchronous Machine (PMLSM) to produce electrical energy, its intrinsic multidirectional and non-linear dynamics have been typically described in a simplified mono-directional and linear fashion when considering a system-level modelling approach.This paper presents a detailed, multi-directional, multi-domain model of the FPE and PMLSM. The model was implemented in an opposed-piston free-piston engine configuration and validated against experimental data captured from a prototype with identical parameters. The simulation results indicate a strong correlation to the experimental data, which captured the dominant dynamics of the FPE and proved the satisfactory accuracy and performance of the model.This study considers the characteristic multidirectional nature and non-linearity of the machine dynamics and its interactions with multi-physical domains such as electrical, mechanical, and pneumatic.