Motion control of free piston engine generator based on LQR

As an alternative power resource of Hybrid Electric Vehicle (HEV), the Free Piston Engine Generator (FPEG) is investigated for its potential advantages in terms of fuel efficiency and fuel flexiblity. Precise control of piston motion is important for reliable operation of free piston engine. In this paper, a discrete-time control-oriented model of free piston system is derived based on the energy conservation equation. An optimal controller based on LQR technique is designed to control piston position. Concerning the impact of disturbance due to transient load requirement, the system is augmented with an integrator to stabilize the steady state error. Finally, effectiveness of the designed controller is tested in a high fidelity simulation model established in the AMESim environment and the results are satisfying.