Rotary Regenerative Shock Absorber for Automotive Applications: Control Strategies and Hardware-In-the-Loop Implementation

Active and semi-active suspensions are devices designed to improve the comfort and road-holding performance of the vehicle. Considered as one of the most advanced technologies in the automotive field, they allow to control the suspension motion by acting on its damping characteristics (semi-active and active), to perform energy recovery functions (active) and to provide active forces to the suspension (active). The semiactive device can induce a variable damping without requiring high energy levels and with reduced costs. The active system, instead, needs more supplied energy, higher costs and produces an overall actuation force for controlling the suspension motion. In the last years both solutions have been studied and developed in different forms with peculiar features, with the common purpose of enhancing the performance of a conventional fixed-damping suspension system. One of these active technologies is the subject of this Thesis Work: a Rotary Regenerative Shock Absorber (RRSA) for automotive application. This prototype has been designed as a pure electro-mechanical active device installed in the vehicle suspension to replace the traditional passive damper. By means of a properly designed linkage system, the forces exchanged between ground and tire are transmitted to the RRSA device, which in turns is able to provide active and passive forces, with potential energy recovering capacity in the second case. This study, in particular, has focused on the RRSA prototype introduced in a physical Hardware-In-the-Loop (HIL) installation. The active device has been connected to an actuation testbench and simulated in different conditions imposed by a Quarter Car SimulinkTM Model implemented in a dSpaceTM Unit. First, the entire HIL system has been modelled in Matlab/SimulinkTM. Then, the limited testbench-bandwidth has been extended by using properly designed Compensation Methods, experimentally validated in actual HIL Testing. After that, simulations and tests have been conducted to the HIL Model to prove its robustness. Finally, specific analyses have been carried out to the RRSA Model for evaluating the most suitable control strategy for optimizing the performance of the Quarter Car Model.