Aspects of tandem bogie axles from perspective of state-space modeling

Abstract

The main differences between tracked and wheeled vehicles are the cross-country capability, dependability, comfort, travel speed for the paved surfaces (roads) and last but not least -the amount of resistance which needs to be overcome in order to move the vehicle or its energy efficiency. In the past decade, these differences are growing thinner in favour of wheeled vehicles, due to clever design and modern technologies that enabled torque vectoring and suspension types that are far beyond the coil springs and ordinary dampers. The developments are so quick that somehow some designs are skipped and replaced by others, even before we reached its maximal potential. One such example are the leaf springs, the very old design which has its powerful benefits for the heavy trucks. Currently the researchers are focused on the enhancements for the material point of view, spring steel is being replaced by various composite materials, so it weighs less, its behaviour is more controllable and the unsprung mass is lower.But the power of the leaf spring lies elsewhereit is its utilization for the tandem suspensions, often called the tandem bogie, or walking beam -the leaf spring as the beam or equalizing suspension. For the driven axles, this layout greatly enhances the cross-country capability of wheeled vehicle, since it is able to equally distribute the normal forces, therefore the driving forces are higher and the vehicle can better move. This system works really well in real life muddy conditions, however, it is very complex for the simulations and modelling. Firstly, the leaf spring as it is and its dynamic nonlinear hysteretic behaviour is extremely complex, secondly, its implementation to the dynamic simulation is rather challenging. This paper will provide the insight to the differences between the independent suspension and the tandem one, from the perspective of the state-space models with 8 and 9 degrees of freedom.