Hybrid analog digital control method and apparatus for estimation of absolute velocity in active suspension system

An improved method and apparatus is provided for estimation of absolute velocity in active or semi-active suspension systems. A controller (12) produces a signal estimate of absolute velocity which can be implemented by a control algorithm to attenuate motion between spaced members (14,16), such as in vehicular suspension systems. The controller (12) performs time integration of an accelerometer input signal by an analog integrator means (36) comprising a first-order low-pass filter. A digital feedback or offset means (38) is utilized to stabilize the signal and constrain the constant and relatively low frequency components of the analog integrated signal about an oscillatory voltage range. A digital filter means (40) receives the stable signal and removes selected constant and low frequency components of the signal to produce a signal indicative of absolute velocities for a frequency range of interest further stabilized about a selected mid-range voltage value.