Hydraulic Free Piston Engine Enabled by Active Motion Control

This article explores various functional aspects of hydraulic free piston engine (FPE) enabled by action motion control. Given the potential for high efficiency and flexibility, the FPE is well suited for mobile applications such as on-road vehicles and off-road heavy machinery. The advantage of the active motion controller lies in its ability to precisely track and shape the piston trajectory. FPE has a great potential for energy saving and emission control, but its reliable operation is limited by the complex dynamic coupling among the engine subsystems and the lack of the crankshaft. This inherent technical barrier for FPE could be overcome by active control with today’s sensing, actuation and computing technologies. A prototype hydraulic FPE is used to demonstrate the capabilities of active piston motion control. Experimental results demonstrate the feasibility and promise of the technology. Engine power control will be combined with piston motion control in the future to achieve a wider range of engine operation and higher engine efficiency.