The suspension system of a vehicle contributes significantly to road-holding and ride comfort by providing simultaneously a sufficient tire to road contact and a good isolation of the vehicle body from road excitations. Generally, design of suspension systems means finding a compromise between these two conflicting demands since optimal ride comfort and optimal road-holding imply different requirements. Compared to merely passive suspensions, semi-active suspensions enable a mitigation of the abovementioned design conflict by allowing the continuous control of the damper force within the force limits. However, in the design of control laws for semi-active dampers, the actuator’s inherent force limits constitute major performance restrictions. In this challenging context, generic high-performance semi-active damper controllers are being developed for multiple testing vehicles available to the institute, namely the ROboMObil and the SC³-Bulli (Safety Critical Connected Control - Bulli; based on a VW T5 van, see plant in figure below) as well as vehicles of the industrial partner KW automotive GmbH.
The two institute-owned testing vehicles have contrasting properties and thus cover a broad application spectrum. While the ROboMObil is a light electric vehicle with in-wheel motors, the SC³-Bulli is the institute’s general purpose experimental vehicle for safety critical connected control, in which semi-active damper control is the first application. Therefore, the SC³-Bulli was equipped with sensors, rapid control prototyping hardware, semi-active dampers, and a Car2X communication radio. In particular, the institute investigated the benefits of LPV-based robust control in a full-vehicle context. The control structure of the LPV controller with an observer, feedback controller, and inverse damper model (see figure below) provides guaranteed stability and performance over the specified scheduling parameter range.