Steady-State Energy Transfer of a Semi-Active Suspension Under Hybrid Control

Magnetorheological (MR) fluids are often characterized by their field-dependent yield stress. Upon the activation of a magnetic field, the fluid has the ability to change from a fluid state to a semi-solid state in milliseconds. The field-dependent yield stress and the fluid’s fast response time make MR fluid an attractive technology for many applications. One such application that has gained considerable attention is in MR fluid dampers. The real-time control possibilities make MR dampers attractive alternatives to conventional viscous dampers. In comparing passive dampers with MR dampers, an equivalent viscous damping coefficient is often found from the energy dissipated by the MR damper with a fixed current applied to the damper. In contrast, this study investigates energy dissipation of the MR damper under a semi-active hybrid control policy. Hybrid control is a linear combination of skyhook and groundhook control. This study investigates the system energy under steady-state conditions at three frequencies, and how the system energy varies with varying contributions from skyhook and groundhook. A quarter-car rig was used to evaluate the dynamics of the hybrid suspension using an MR damper. Previous studies have shown that hybrid control can offer advantages to both the sprung and unsprung masses; however the relationship between energy dissipation and performance is not clear. In this study, we compare control policy performance to several energy-based measures. Results indicate that there is a strong correlation between sprung mass RMS acceleration and unsprung mass RMS acceleration to several of the energy-based measures.Copyright © 2004 by ASME