Dynamic behavior of a 5-DOF vehicle system with semiactive on-off damper is studied for improving ride comfort as it travels on a road of random surface characteristics.
The criterion for the on-off action of the damper is the sign of the multiplication of relative displacement and velocity, and the damping force is assumed proportional to the square of the relative velocity. The object function is variance of the acceleration response at seat weighted by the frequency-dependent human sense. The design variables are damping coefficients at on and off actions. Due to the nonlinearlity of the system, the acceleration response is calculated by a numerical integration method, Runge-Kutta, in time domain, transformed into frequency domain by using FFT algorithm, and then weighted by the weighting function.
The results of this study shows that an optimized semiactive on-off suspension system can improve ride comfort by about 20-30 % compared with an optimum passive one.