2. EQUIPMENT AND PROCEDURE
The test vehicle was a mid-size Malaysian executive vehicle,
Proton Perdana, with a V-6 engine. It is a four-door sedan
with a curb weight of 1336 kg. With 16-inch rims and Lotustuned
suspension settings, the car handles well through tight
corners and is a good high-speed cruiser. The vibration signals
were measured while driving over four flat road surfaces, and
the speed was controlled manually by the driver. As shown
in Fig. 2, the selected roads were highway, pavement, suburban,
and bumpy. Characteristics of the road surfaces are presented
in Table 1. The highway had a flat, smooth surface
and occasional unevenness, which resulted in minimum disturbances.
The pavement road was a cobbled street made by
similar smooth stones with 5-mm thickness. The similar gap
between the adjacent stones caused harmonic excitations with
different periods at each axis. The suburban road had frequent
random irregularities from 3 mm to 25 mm, which produced
excessive casual vibration. The bumpy road was a suburban
rough surface with high and sharp bumps up to 50 mm, which
resulted in shock responses. The vehicle was driven at 20, 40,
60, and 80 km/h over all roads except the bumpy road. The
driving speed over the bumpy road was only 20 km/h. The
vehicle was also tested at 100 km/h on the highway.