An improved method and apparatus is provided for estimation of absolute velocity in active or semi-active suspension systems. A controller produces a signal estimate of absolute velocity which can be implemented by a control algorithm to attenuate motion between spaced members, such as in vehicular suspension...http://www.google.com/patents/US4953089?utm_source=gb-gplus-sharePatent US4953089 - Hybrid analog digital control method and apparatus for estimation of absolute velocity in active suspension systems
