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In this study, a structure of a five degree of freedom flywheel energy storage system (FESS) is introduced. A nonlinear model of active magnetic bearing (AMB) system in the FESS is obtained by Lagrange's equation. In this model, the current in each coil is treated as a state variable and the control input is the voltage applied to each coil, this approach offers more advantages than current control input approach. PID controllers with decentralized structure are proposed to control the nonlinear multiple-input multiple-output (MIMO) system. Dynamic behavior of the flywheel in magnetic bearings and performance of the controller is discussed in simulation results.

As a branch of the Hydraulic Hybrid Vehicle (HHV) technology, Series Hydraulic Hybrid Vehicle (SHHV) has been an important research object of institutions and automotive manufacturers all over the world. With the flexibility of engine management and regenerative braking characteristics SHHV is expected to be a short-term solution to develop a higher efficiency, cleaner, and safer transportation. In this work, the function and parameter determination of key components for SHHV are discussed. Based on the analytical analysis, the suitable set of component parameters is selected. The model of SHHV is implemented via Simulink/MATLAB mostly based on SimScape toolbox. The proposed model can be used as a development tool to quickly simulate the real hybrid system when it allows applying different parameter sets and in various conditions. The performance of the system is evaluated through some specific cases and the capability of braking energy recovery of the system is also investigated. Simulation results indicate that for a 2.5 ton truck case, more than 86% of braking energy can be captured and more than 72% of that energy can be returned to the kinetic energy of vehicle motion.

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