Active Motion Control of a Hydraulic Free Piston Engine

Precise piston trajectory control for a free piston engine

“…Therefore, to support the abovementioned explanation, we implement the three controllers in a high fidelity model of the hydraulic FPE, which was validated previously (Li et al, 2014), with a supply pressure of 414 bar. The simulation result of tracking the 50 mm displacement sinusoid trajectory is shown in Fig.…”

“…The piston motion is mainly driven by the combustion force, whereas the hydraulic force is only controlled to compensate the cycle-to-cycle variations. For a more detailed description of the engine operation, readers are referred to the previous publication (Li et al, 2014).…”

“…However, the complex interactions between the gas dynamics and the load in real time make the calibration a tedious task, and the resulting controllers are sensitive to variation of the operating conditions and disturbances. To address the challenge, an active piston motion controller, which seamlessly coordinates the combustion and the load so that piston follows prescribed reference trajectories, was designed (Li, Sadighi, & Sun, 2014). Since the controller acts as a crankshaft but not an actual mechanism, it was named the virtual crankshaft which is implemented digitally on the FPE.…”

A control-oriented model for piston trajectory-based HCCI combustion

“…Previously, an active piston motion control, named as "virtual crankshaft", was designed and verified experimentally by the authors. Such a control coordinates the combustion and engine load in real time to regulate the piston following prescribed reference trajectories precisely [11], so that continuously variable compression ratio (CR) as well as adjustable motion pattern between the bottom dead center (BDC) and the top dead center (TDC) can be achieved. Hence conventional slidercrank mechanism is inappropriate to describe this piston motion and a new description is desired.…”

“…This method is enabled by free piston engines (FPE), Chen whose piston motion is not constrained by the crankshaft mechanism [11,12]. As a result, the interaction between the chemical kinetics and the in-cylinder gas dynamics can be adjusted intelligently through the combustion chamber volume profiles and the optimal combustion outcome can be achieved (Fig.…”