The MSK method is described in Figu

The MSK method is described in Figure 6(b), where two low-pass filters with a pass-band
edge frequency of 80 rad s1 are used to condition the measured signal. For this control
method, the relative displacement and acceleration are used as feedback signals. Here we
use
...
x s instead of  xs to determine the velocity direction of the sprung mass. Since the value
of
...
x s can be easily obtained by differentiating the filtered sprung mass acceleration  xs, it
makes this method more practical than the traditional MSK method, which, as discussed
above, needs to determine the sprung mass velocity by designing a complicated observer
or by integrating the acceleration. Since the acceleration differentiation brings noise to the
signal, a post low-pass filter is needed.