Electro-magnetic suspension for automotive applications

Semi-active electromagnetic suspension technologies are becoming an increasingly attractive topic for scientists and engineers throughout the world. Their dual-purpose adaptability can improve the vibration suppression of vehicle body while offering energy harvesting features. Various technological design concepts have been presented to improve the filtering and regeneration functions in automotive dampers. Although a large number of concepts and models have been developed on damping and regeneration performances, most of them represent significantly simplified models that do not consider nonlinear material behaviour and limitations such as magnetic saturation. The present thesis work reports an integrated (experimental and numerical) methodology which combines the development of a finite element multiphysics model with an experimental strategy to optimally design an electromagnetic semi – active damper for automotive suspensions. The multiphysics model couples the whole set of timedependent electromagnetic, thermal, mechanical, and fluid dynamics partial differential equations. The developed FE model was validated against both literature model predictions and in-house experimental data. The electromagnetic model takes into account the magnetic material characteristics of the ferromagnetic material and iron poles. Jiles - Atherton hysteresis models were applied to obtain an accurate magnetic flux distribution over back iron, and a loss separation method was applied for ferromagnetic materials to determine the heat generated in the soft iron parts. The computation of the fluid dynamics in the air gap between magnetic piston and stator tubes allowed the temperature field across the solid materials, including the magnets, to be predicted. The design of the electromagnetic damper addresses the effects of the geometries of the stator and rotor, as they are the most critical geometries for maximising the conversion efficiency. The magneto-thermal simulations suggested that the heating of the permanent magnets remains within a safe region over the investigated operational frequency range of the electromagnetic damper. Moreover, multibody dynamics analysis, aimed at verifying the key performance indexes, showed that the limitations, which were mostly due to electromagnetic losses of the back iron in the new electromagnetic damper did not change the road holding index to any great extent and performed within safe limits. The developed electromagnetic damper combines the performance of a passive eddy current damper with slotless generator functions. It has been demonstrated that by varying the load resistance, power, and damping performance of the damper changes. The power output is maximum when load resistance matches internal coil resistances, while the short circuit offered the highest level of damping.