Use of An Active Electro-Hydrostatic Actuation System for Vehicle Vibration Damping Applications

Conventional vibration damping in wheeled vehicles is mainly performed by means of passive hydraulic systems. Active and semi-active solutions are adopted when there is particular interest in varying the damping response of the shock absorbers for vehicle handling and comfort. To this end, electro-hydrostatic actuation (EHA) devices represent a promising alternative in active vibration control. In these systems, an electric motor is employed to drive a fixed-displacement hydraulic pump. The flow generated by the pump is then conduced into a hydraulic piston that acts as a conventional damper. The use of a motor as a primary actuation device eases the control task and offers a large output bandwidth. This feature represents an advantage with respect to active hydraulic technologies, which attain limited bandwidth frequencies and use highly nonlinear servo-valves. Moreover, the reversible nature of the electric machine in EHA actuators allows part of the energy exchanged during damping to be recovered. When compared to electromechanical shock absorbers, EHA devices offer higher output power densities and higher efficiencies. In this context, the present paper describes the design, modelling and control of an active EHA system utilized for vehicle damping purposes. An overview of the current active solutions and a comparison with the EHA technology are revised. Results in terms of damping response and energy harvesting capabilities are then discussed.