Experimental evaluation of an unsophisticated two state semi-active damper

Abstract This paper describes the experimental evaluation of a two-state damper, used as the variable force element in a semi-active suspension. The study was necessary to establish the influence of non-ideal operating conditions when existing control strategies were evaluated in a practical environment. Three existing control strategies, each derived by using a different approach, were chosen for evaluation purposes and to experimentally determine the feasibility of semi-active suspensions. The control valve used to switch between states consisted of a pressure-dependent logic element and a directional spool valve. Characterization of the valve revealed a highly non-linear behaviour when switching between states. Experimental results indicated that two state semi-active dampers, which should offer a substantial cost saving over continuous variable dampers, especially in heavy wheeled vehicle applications, provide significant ride improvement potential. Furthermore, it was established that more complex phenomena existed than those normally taken into account during the usual theoretical evaluation of semi-active dampers.