Instead, the simplest model of track-induced unevenness with non-sine periodicity has been chosen at this stage. For simplicity, the variation in surface profile over which a wheel traverses can be estimated as a finite series of half sine wave pulses with a frequency f corresponding to the ratio of the vehicle forward velocity V to the track pitch ___ สูตร . By carrying out a simple Fourier integration over a certain time interval T, this input signal can be represented in the frequency domain: _. The corresponding expression for Zr and ZW take the form