Theoretical investigation of the performances of the passive and semi-active suspension systems with air springs and comparision with mechanical suspensions

vTHEORETICAL INVESTIGATION OF THE PERFORMANCES OF THEPASSIVE AND SEMI-ACTIVE SUSPENSION SYSTEMS WITH AIRSPRINGS AND COMPARISION WITH MECHANICAL SUSPENSIONS(M.Sc. Thesis)Hakan BALGAZI UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYApril 2006ABSTRACTIn this study, two different quarter vehicle models, one with apassive and the other with a semi-active suspension system, bothwith air springs were considered. A suitable set of state variableswas defined and state equations were obtained for each system.Mathematical expressions describing the spring characteristics ofthe air spring with and without auxiliary chambers were obtained.An integral performance index involving a weighted combination ofmean square sprung mass acceleration and mean squaresuspension deflections was defined, and closed loop optimumcontrol was obtained by using Pontryagin principle. Performancesof the passive and optimally controlled semi-active systemssubjected to initial conditions, measured road profile and sinusoidalinputs were investigated, and performance of the optimallycontrolled system was compared to that of the passive system.Results show that, i-performance of the semi-active suspensionsystem with air spring is hardly better than that of passivesuspension system with air spring, ii- suspension deflections insuspension systems with air springs are acceptable, but bigger thanvithose of mechanical suspension systems, and are in allowablereagon, iii- accelerations in suspension systems with air springs aremuch smaller than those of mechanical suspension systems.: 914.1.091Science CodeKey Words : Semi-active suspensions, variable stiffnesssuspensions, bilinear systems, optimum controlPage Number : 109Adviser : Asst. Prof. Dr. Metin Uymaz SALAMCI,Prof. Dr. Yücel ERCAN