Method and apparatus controlling a semi-active suspension

The present invention relates to a method and apparatus for controlling a controllable suspension system (12) a controllable force generator (13) said controllable suspension system (12) being interconnected between a first element (14) and a second element (15) in order to optimize the vertical dynamics, either in comfort or safety, of one of said first and second elements (14,15). A characteristic of the present invention is that of recognizing through the method and the controlling apparatus if the first element (14) or the second element (15) show high or low frequency dynamics, considering the value of the ratio between one first signal (Sl) squared and a second signal (S2) squared, said first signal (Sl) being representative of the acceleration of said first element (14), and said second signal (S2) being representative of the speed of said first element (14).