Step-control and vibration characteristics of a hybrid vehicle suspension system considering energy consumption

This paper proposes a hybrid suspension system, consisting of a linear electric motor (LM) and a semi-active mono-tubed magnetorheological damper (MRFD), to improve vehicle dynamics with lower power demand. For determining the damping force directly and concisely, a modified bi-viscosity magnetorheological fluid (MRF) model that explicitly includes the current parameter is developed. The fabricated LM and MRFD are calibrated and tested for validation of the implemented mathematical models. The simulation results show that the modified bi-viscosity model is able to calculate the experimental MRFD external forces very well. Thereafter, the hybrid suspension system is integrated into a 2-DOF (degree-of-freedom) quarter-vehicle dynamic model for simulation analysis, considering bump and pothole road profiles and the wheel bounce movements. Moreover, the two step-control methods, namely SC1 and SC2, are modelled for enhancing vibration mitigation and reducing power demand. The MRFD current influences on the root mean square (RMS) of the vehicle body vibration amplitudes are studied. Results reveal that the optimal MRFD current is ranged from 1 to 2.2A considering the SC1 method. Finally, the energy efficiency of the step-control methods is proved to be much higher than the PID method especially at low vehicle speed and in large road heave situations.