Design Methodology of Electro-Hydrostatic Shock Absorbers for Automotive Suspensions

Conventional damping systems in wheeled vehicles are constituted by passive hydraulic devices that offer limited versatility and poor adaptability to road conditions. Specific applications demand a suspension system that is capable of damping or yielding different amounts of mechanical power, thus favouring vehicle handling and ride comfort. For this purpose, electro-hydrostatic actuation (EHA) systems offer an optimal solution. In these systems, an electric motor is employed to drive a fixed-displacement hydraulic pump. The flow generated by the pump is then conducted into a hydraulic piston that acts as a conventional damper. The use of an electric motor guarantees a simple control scheme that allows system reversibility; hence it can perform auto-levelling and damping tasks. Moreover, it is possible to recover part of the energy involved during damping if the system is used as an active-controlled shock absorber. When considering a solution of this type, it is fundamental to follow a systematic approach to guide the entire design process. The adequate selection of each component is important to guarantee mechanical robustness and compactness, while meeting dynamic performance and power density requirements. Different sources in literature have studied this problem for specific applications \cite{manring,kangl}. In addition, the growing interest in applying active control techniques to vibration control remarks the necessity of introducing a particular procedure for developing EHA systems in this context. To this end, the present work thoroughly explains and applies a generalized design methodology of an electro-hydrostatic system for vehicle vibration damping applications.