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The present work focused on the application of innovative damping technologies in order to improve railway vehicle performances in terms of dynamic stability and comfort. As a benchmark case-study, the secondary suspension stage was selected and different control techniques were investigated, such as skyhook, dynamic compensation, and sliding mode control. The nal aim was to investigate which control schemes are suitable for optimal exploitation of the non-linear behavior of the actuators. The performance improvement achieved by adoption of the semi-active dampers on a standard high-speed train was evaluated in terms of passenger comfort. Different control strategies have been investigated by comparing a simple SISO (single input single output) regulator based on the skyhook damper approach with a centralized regulator. The centralized regulator allows for the estimation of a near optimal set of control forces that minimize car-body accelerations with respect to constraints imposed by limited performance of semi-active actuators. Simulation results show that best results is obtained using a mixed approach that considers the simultaneous applications of model based and feedback compensation control terms.

The present paper proposes a methodology to design and manufacture optimized turbomachinery components by leveraging the potential of Topology Optimization (TO) and Additive Manufacturing (AM). The method envisages the use of TO to define the best configuration of the rotoric components in terms of both static and dynamic behavior with a resultant reduction of overall weight. Eventually, the topology-optimized component is manufactured by using appropriate materials that can guarantee valid mechanical performances. The proposed strategy has been applied to a 2D impeller used for centrifugal compressors to prove the effectiveness of a TO+AM-based approach. Although this approach has never been extensively used before to centrifugal compressors and expanders, its application on rotor and stator components might unlock several benefits: tuning the natural frequencies, a reduction in the stress level, and a lighter weight of the rotating part. These objectives can be reached alone or in combination, performing a single analysis or a multiple analyses optimization. Finally, the introduction of AM technologies as standard manufacturing resources could bring sensible benefits with respect to the time to production and availability of components. Such aspects are essential in the Oil and Gas context, when dealing with new projects but also for service operations.

In the last years magneto-rheological dampers have been successfully used to realize semi-active suspension systems for automotive applications. Due to their dimension flexibility and the wide range of forces they can exert, these devices can be used even for railway applications, such as in the present work. This paper is focused on the design, evaluation and comparison of different control strategies for semi-active suspension system on the secondary suspension stage of an high speed train. In particular, the classical simulation of mechanical impedance, also known as "skyhook damper", and a "sliding mode" control exploiting the gradient projection method in order to cope with linear constraints on the forces, have been compared to a traditional passive suspension system. In order to test the proposed control strategies and to simplify the control gain refinement, a multi-body model of the railway vehicle have been built by means of Matlab/Simulink TM . Moreover, in order to fairly compare the different control strategies, a performance index has been defined, which is based on the comfort test that is usually done on real trains.