Ride Comfort Values of Four Korean Cars in Highways

Abstract

Vibrations on the floor in a car are transmitted to the foot, hip, and back from the seat. Human body recognizes these vibrations, but the sensitivity for each vibration is different. To evaluate these vibrations, RMS(root mean square) of accelerations, VDV(vibration does value), percent vibration, and SEAT (Seat Effective Amplitude Transmissibility) value are commonly used. For the SEAT value calculation, the PSD (Power Spectral Density) of the accelerations at the seat and the PSD of the floor are used with the frequency weighting function. If the SEAT value is less than 1, the vibration level on the seat is less than the floor, which means seat is effective to reduce the vibration. In this paper, four types of cars, i.e., a small size car of 1300cc gasoline engine, a mid-size car of 1800 gasoline engine, a full-size luxurious car of 3600cc gasoline engine, and a SUV (sport utility vehicle) of 2900 diesel engine are used and compared ride comforts using SEAT values. Experiments were carried on a highway near the suburb of Busan metro-politan city in South Korea. To compare ride comforts, the SEAT values in dynamic state are compared. Several air cells are installed in the seat cushion to improve seat comfort and to adjust seat properties by changing the air pressure. From the real car experiments, optimum air cell pressure depending on the vehicle speeds and road conditions are recommended.