The suspension systems can be categorised according to external power input and/or control bandwidth. A passive suspension consists of non-controlled springs and shock-absorbing dampers. In a semi-active system the body movement is sensed and the characteristics of the passive suspension components are switched to either soften or stiffen the suspension. In an active suspension actuators supply additional forces by feedback control law using data from sensors attached to the vehicle. After some introductory background, history and facts on the state of the art of suspensions are presented. In adaptive suspensions the rates of the springs and/or the dampers are switched between discrete hard and soft settings of a passive spring-damper system. Switchable dampers employ motor- or solenoid-driven bypass valves within the body of the unit. Adaptive spring rates necessitate a fluid spring medium, i.e. oil or air. In slow-levelling air systems extra volume canisters and pneumatic solenoid valves are used at each wheel. In hydraulic suspensions hydraulic/nitrogen high-pressure accumulators are switched in and out. In the active anti-roll system of Citroen one end of each of the anti-roll bars is manipulated by a linear ram to keep the car body roll-free in corners. In wrap control the front-to-rear roll couple reaction ratio is manipulated in response to yaw rate measurements to determine whether the car understeered or oversteered through corners. In skyhook damping the actuation force, i.e. the damping is proportional to the absolute body velocity.
Active suspensions: some background
Aktive Radaufhängungen: Eine Einführung
IEE Proceedings - Control Theory and Applications ; 142 , 2 ; 123-128
1995
6 Seiten, 3 Bilder, 6 Quellen
Article (Journal)
English
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