Design Optimization of MagneShock Magnetorheological Shock Absorbers and Development of Fuzzy Logic Control Algorithms for Semi-Active Vehicle Suspensions

Abstract

Automotive ride quality and handling performance remain challenging design tradeoffs for modern, passive automobile suspension systems. Despite extensive published research outlining the benefits of active vehicle suspensions in addressing this tradeoff, the cost and complexity of these systems prohibit widespread commercial adoption. Semi-active suspensions offer reduced performance benefits over passive suspensions without the cost and complexity associated with fully active systems. This paper outlines the benefits of implementing real-time, fuzzy logic control (FLC) to a vehicle suspension equipped with commercially available magnetorheological (MR) shock absorbers, Carrera MagneShocks™.

MagneShocks™ utilize controllable electromagnets to change the MR fluid viscosity and vary the damping characteristics of the shock. The application of FLC to these components, based on the expertise of experienced engineers from the racing industry, was first tested and refined in simulation, then applied experimentally, resulting in the significant improvement of vehicle performance. Results include 25% reductions in sprung-mass absorbed power (U.S. Army 6 Watt Absorbed Power Criterion) as compared with typical original equipment (OE) shock absorbers over urban terrains in both simulation and experimentation. RMS sprung-mass accelerations were also reduced by as much as 9%, but usually with an increase in total suspension travel over the passive systems. Nominal degradations in RMS tire normal forces were documented through computer simulations. When compared to fixed-current MagneShocks™, FLC resulted in 2-9% reductions in RMS sprung-mass accelerations and comparable absorbed powers. Possible means for improving the performance of this semi-active suspension include reducing the suspension spring stiffness and increasing the dynamic damping range of the MagneShock™