KSME International Journal, Vol. 13, No. ~ pp. 459--469, 1999 459 Automotive Seat Vibration Control via Hydraulic Semiactive Vibration Absorbers (SAVA) Changki Mo*, Myoungho Sunwoo** and W. N. Patten*** (Received September 21, 1998) The paper examines the ride performance enhancement that can be obtained by applying hydraulic semiactive vibration absorbers (SAVA) to alter the compliance characteristics of the seat/wheel suspension system. The work relies on a consistent model of the (nonlinear) hydrau- lics of the SAVA. A recently developed Lyapunov control scheme is used for regulation. The performance is examined assuming a quarter car with a seat/seat mounted mass. The paper then employs a quarter car/seat with a two mass ISO model of the seated human. Two road conditions are employed in the simulations; a ride swell and a road surface with a white noise velocity profile. The results show 45% reduction of of the vertical acceleration. Key Words: Semiactive, Vibration Absorber, Ride Comfort Modeling, Lyapunov Control Nomenclature Apl,z Avl,2 Avmaxl,2 Avrnlnl,2 Cdl)2 Ca Cb,h ka k b,h k~ ku ma mb,h ms mu 71,2 Effective area of the actuator : Valve opening area : Maximum value opening area : Minimum value opening area : Discharge coefficient : Damping coefficient of the seat :Damping coefficient of the lower/ upper mass : Stiflhess of the seat : Stiffness of the lower/upper mass : Stiffness of the sprung mass : Stiffness of the unsprung mass : Occupant/seat mass : Lower/upper mass of a human : Sprung mass : Unsprung mass : Volume of the actuator chamber 1,2 * Dept. of Automotive Engineering Sangju National University 386 Gajang-Dong Sangju, Kyungbuk 742-711, Korea E mail:ckmo@sam- back.sangj u.ac.kr ** Dept. of Automotive Engineering Hanyang Univeristy 17 Haengdang Dong, Sungdong-Ku Seoul 133-791, Korea E-mail:msunwoo @email. hanyang.ac,kr. *** School of Aerospace and mechanical Engineer- ing University of Oklahoma 865 Asp Ave. Rm 212 Norman, OK73019, U.S.A. X~ Xd Xs,u ,~PI,2 : Displacement of the seat 9 Road input, displacement :Displacement of the sprung/ uns- prung mass : Bulk modulus of the fluid : Differential pressure of the actuator 1,2 1, Introduction Ride comfort is a key objective in the design of an automobile. Vibration in a vehicle can cause discomfort, annoyance, and even chronic health problems for automobile occupants. The princi- pal interface between occupants and the vehicle is the automobile seat. it is becoming increasingly clear to automobile manufacturers that as the real cost of the auto rises relative to the earning power of the customer, there is an increased expectation of performance and comfort. Whole body vibra- tion experienced during traveling in an auto is very often perceived as a source of discomfort. There are now extensive efforts by researchers to understand the nature of ride vibration and its effect on perceived comfort. Traditionally, auto makers have relied on the optimized passive design to achieve acceptable levels of ride com- fort. But what was acceptable a decade ago is not