Semi-active suspensions offer a large potential to improve essential vehicle properties like ride comfort, road-holding and vehicle handling compared to passive suspensions. The exploitation of this potential relies on suitable semi-active suspension control algorithms which consider the nonlinear control signal to damper force characteristic and the passivity constraint of the semi-active damper. In particular, the passivity constraint introduces a restrictive state-dependent actuator force limitation and should be explicitly considered during the control design. The design of high-performance semi-active damper controllers constitutes a challenging task due to the different requirements of an optimal control design regarding road disturbances and load disturbances induced by the driver inputs, and the needed full-vehicle control approach to realize the performance potential of vehicles equipped with semi-active suspensions. In contrast to the conventional quarter-vehicle based suspension control approaches commonly found in the literature, the full-vehicle control approach proposed in this dissertation aims at taking into account the body heave, roll and pitch motions. Moreover, the full-vehicle control approach facilitates the development of active fault-tolerant controllers by exploring the weak input redundancy provided by four semi-active dampers. The dissertation addresses this complex control problem by linear-parameter varying (LPV) control methods. The force constraints of the semi-active damper are modeled by saturation indicators and these are treated as scheduling parameters in the LPV design. Additionally, the LPV controller is augmented by a damper force reconfiguration such that the controller compensates for the damper force loss in case of saturation or failure by the remaining healthy dampers. The different requirements of an optimal control design regarding road disturbances and driver-induced disturbances are met by a two degree-of-freedom control approach comprised of an LPV feedback controller and an LPV feedforward filter. The LPV feedback controller focuses on the attenuation of road disturbances, while the LPV feedforward filter reduces the effect of driver-induced disturbances. In this way, the two-degree-of-freedom control provides good performance regarding both disturbances. The effectiveness of the proposed two-degree-of-freedom LPV controller is validated by experiments on a four-post test-rig and by road tests. The results show the improved trade-off between ride comfort and road-holding of the full-vehicle LPV controller. In particular, the full-vehicle LPV controller achieves a 10 % improvement of ride comfort and road-holding compared to a full-vehicle Skyhook-Groundhook controller. Furthermore, an experiment with an assumed damper failure emphasizes the benefit of the active fault-tolerant full-vehicle LPV controller. Finally, the results of the double lane change manoeuvers performed during the road tests illustrate the enhanced ride comfort and handling properties of the vehicle with two-degree-of-freedom LPV control compared to the set-up without feedforward filter.    «

Semi-active suspensions offer a large potential to improve essential vehicle properties like ride comfort, road-holding and vehicle handling compared to passive suspensions. The exploitation of this potential relies on suitable semi-active suspension control algorithms which consider the nonlinear control signal to damper force characteristic and the passivity constraint of the semi-active damper. In particular, the passivity constraint introduces a restrictive state-dependent actuator force limi...    »