Complete E-Drive NVH analysis, in time domain, using state-space representation

In the last 20 years, with the purpose to reduce the CO2 emissions, the main trend in mobility has been a progressive electrification, meaning the transition from Internal Combustion Engines (ICEs) vehicles to Electric Vehicles (EVs). Noise, Vibration and Harshness (NVH) analysis is the study and measurement of aural and tactile feedback in an object and in the context of Electric Machines (EMs) introduction, the acoustic noise and vibration emitted by EMs plays an important role in the design of mechatronics systems and it has to be studied to guarantee high performances also in terms of safety and comfort; reducing the noise and vibration levels, it is possible to increase the driving comfort rating. In EMs, the forces are generated by the electric currents and electromagnetic fields inside them. Finite Element Analysis (FEA) is the method generally used for NVH purposes. As first step, it is possible to perform the system Modal Analysis which provides a general idea of the model structural dynamics; the second step is represented by the introduction of the forces, evaluating the Forced Response. The main drawback of this method is represented by the fact that, changing the system operating conditions, it is requested to repeat the whole procedure from the beginning, leading to a not so flexible model, costly from a computational point of view. The main purpose of this thesis project, therefore, is to find an alternative path to study the same problem in time domain, faster than the previous, without losing accuracy in the results. For time-domain problems, State Space representation (SS) can be considered a good way to deal with. The workflow can be considered mainly split in two blocks: electromagnetic study and structural dynamics study. In the electromagnetic study the forces inside the airgap are considered. They can handle different consequences: radial forces generate Magnetic Noise; tangential forces mostly influence the machine performances in terms of speed and torque. Structural dynamic study aims to compute the system natural frequencies and the relative modes, together with system vibrational response, both in frequency and in time domains.