Abstract: An adaptive active suspension system for a wheeled vehicle in which a powered actuator supplies a force between an unsprung wheel assembly and the vehicle body. The actuator is controlled by a signal from a feedback control system whose dynamic properties are determined by control gain values stored in a memory. The stored control gain values are calculated to simultaneously reduce vehicle body acceleration, tire deflection and suspension displacement (stroke). A road profile estimator provides an indication of predicted road roughness and, as road roughness varies, the effective stiffness of the suspension system is adaptively altered while maintaining a substantially constant ratio between tire deflection and suspension stroke. To reduce the computational burden on the system, the control gains are pre-computed for a range of varying road conditions and stored in memory.