NVH analysis for Rotary Regenerative Shock Absorber

In recent decades, increasing attention has been directed towards improving comfort and driving stability. In this context, the demand for suspension systems capable of effectively adapting to the excitations coming from the road irregularities became evident. This led to the development of semi-active and active suspensions, now available even in non-premium vehicles. In addition, the need to reduce CO2 emissions, and thus become sustainable for the planet, has led the automotive industry to considerable changes. In recent years, there has been a further push in the electrification direction. This is evidenced by the development of systems, which enhance the efficiency of the electric vehicle through energy harvesting. A glaring example is the Rotary Regenerative Shock Absorber (RRSA), which is the focus of this thesis. It is an electromagnetic damper provided of a Surface Permanent Magnet (SPM) motor, a gearbox and a leverage system linked with the vehicle suspension, which allows a linear-to-rotary motion conversion. In general, electrification has impacted all parts of the vehicle, but primarily the powertrain. The transition from the internal combustion engine (ICE) to the electric engine has eliminated the background noise that was generated by the ICE and predominated inside the passenger compartment. Electric engines in fact produce a typical tonal noise in the high frequency range. As a result, it has become of vital importance to carry out Noise, Vibration and Harshness (NVH) analysis not only for the powertrain but also for all other devices, such as the suspension system. All these new components for the active control purpose contribute to an increase of the generated noises. NVH analysis has become increasingly popular as “sound quality” now plays a crucial role in the consumer’s choice of vehicle. The main aim of this thesis is to carry out a NVH analysis of the RRSA in two different contexts: experimental and simulative. For the experimental one, two different prototypes will be tested. Both share the same electric motor, but they differ in the reducer type used: the first one is equipped with a planetary gearbox, the second one with a cycloidal gearbox. In parallel, a simulative analysis of the planetary prototype has been conducted in order to compare the experimental and the simulative results. The goal is to determine which configuration offers the best NVH performance.