Modeling and control of flywheel mechanical hybrid powertrain for real world conditions

Abstract

This paper focuses on dynamical response characteristics of a flywheel mechanical hybrid powertrain (FMHP), comprising a continuously variable transmission (CVT) and a flywheel integrated into a conventional vehicle with an internal combustion engine. Having unique attractive features such as low cost, easy implementation to existing conventional vehicles, high fuel saving potential and mechanical maintenance-free long lasting components, FMHP is a very strong contender among other electric based hybrid powertrain solutions, especially for short-term and low investment conditions. FMHP is able to provide most important features of hybridization for fuel saving, that is regenerative braking, ICE load shifting for elimination of inefficient part load operation and engine shut-off during standstill. In the literature, promising results can be found about the fuel saving potential of the FMHP, mostly based on quasi-static drive cycle simulations. Various case studies and parameter studies exist, investigating the effect of gear ratio spread/selection, energy management strategy and powertrain layout. Hence it is addressed to discover/surpass fuel saving potential as much as possible although diminishing results may be obtained due to high progress already made, thus to the authors' knowledge dynamic response of powertrain on those studies is neglected and a dedicated study/investigation of it does not exist in the literature. This paper introduces key dynamical properties and possible solutions as a starting point including throttle and brake response in addition to driver modelling for throttle and brake response evaluation, delay characteristics and delay compensation algorithms with blended braking, furthermore drivetrain stiffness/damping properties and controller design for preventing oscillations and jerk for driver comfort. A quasi-static simulation of FMHP is also included without dynamics, for comparison of fuel saving capability with dynamical properties presented here, which is left for future work.