The Effect of Front and Rear Ride Rate Ratios to the Pitch Angle of a Midibus

Abstract

Ride comfort and handling of a vehicle are relevant to front and rear ride rates. Consistency of comfort and handling come with the
harmony of these two phenomenon. A vehicle has several reactions against the base excitations of irregular road inputs. Pitch motion is one
of the most annoying reactions according to human perception. Since the road inputs excide the front wheels of the vehicle first, pitch
motions occur even during small obstacle transitions. The effect of front and rear ride rate ratios to the pitch angle of a midibus is
investigated in this paper. Several ratios are defined and a half vehicle model is generated. Modal analysis is performed, the natural
frequencies of pitch modes are found. A pulse input is defined as base excitation in order to simulate road profile. Transient analyses are
carried out and the vertical displacements of front end and rear end of the vehicle body are obtained. Pitch angles are calculated from the
vertical displacements. Change in the pitch angle according to change in the ride rate ratios is demonstrated. Thus, an optimum ratio is
determined that allows to form minimum pitch angle.