Complementary Filter to Estimate Inertial Velocity

Long appreciated advantageous stability and performance properties of “skyhook damping” are dependent on availability of an inertially referenced velocity signal. In this work a practical complementary filter using acceleration and position measurements is proposed to construct a high quality inertial velocity signal. The filter was used in a hydraulic suspension system, which isolates the cab of a semitractor from pitching motion of the frame. Low frequency pseudo-integration properties previously limited actual system performance on the vehicle. When the proposed complimentary filter was implemented, a nearly 10 dB improvement in resonant frequency attenuation was achieved while maintaining consistent stability margins.