Performance analysis of semi-active suspension with control of variable damping and stiffness

The problem considered in this paper is the study and the control strategy design of semi-active suspensions, featuring the regulation of both damping and stiffness. The first contribution of this paper is the introduction and the analysis of two architectures based on the use of only controllable dampers, which make possible the emulation of an ideal suspension with controllable-damping-and-stiffness. This work presents an evaluation of the performances and drawbacks achieved by such suspension architectures, also in a nonlinear setting (explicitly taking into account the stroke limits of the suspension). This paper then proposes a new comfort-oriented variable-damping-and-stiffness control algorithm, named stroke–speed–threshold–stiffness–control, which overcomes the critical trade-off between the choice of the stiffness coefficient and the end-stop hitting. The use of a variable-damping-and-stiffness suspension, together with this algorithm, provides a significant improvement of the comfort performances, if compared with traditional passive suspensions and with more classical variable-damping semi-active suspensions.