Design of nonlinear controllers for active vehicle suspensions using parameter-varying control synthesis

Nonlinear suspension controllers have the potential to achieve superior per formance compared to their linear counterparts. A nonlinear controller can focus on maximizing passenger comfort when the suspension deflection is sma ll compared to its structural limit. As the deflection limit is approached, the controller can shift focus to prevent the suspension deflection from e xceeding this limit. This results in superior ride quality over the range o f road surfaces, as well as reduced wear of suspension components. This pap er presents a novel approach to the design of such nonlinear controllers, b ased on linear parameter-varying control techniques. Parameter-dependent we ighting functions are used to design active suspensions that stiffen as the suspension limits are reached. The controllers use only suspension deflect ion as a feedback signal. The proposed framework easily extends to the more general case where all the three main performance metrics, i.e., passenger comfort, suspension travel and road holding are considered, and to the des ign of road adaptive suspensions.