Uncertainties Investigation and µ-Synthesis Control Design for a Full Car with Series Active Variable Geometry Suspension

Abstract

Linear robust control schemes, for example the H∞ control, are commonly utilized in the control design of an active suspension system, with a linearized and time-invariant state-space model of the system adopted. However, the vehicle parameter uncertainties are mainly ignored and their effect on the control robustness is not investigated. In this paper, a µ-synthesis-based control scheme is synthesized for a full car with the recently introduced Series Active Variable Geometry Suspension (SAVGS), to mainly enhance the ride comfort and road holding performance, with two significant practical uncertainties in the sprung mass and the suspension damping taken into account. Numerical simulations with a high fidelity nonlinear vehicle model are performed, with the cases of the fixed and swept values of the sprung mass tested, to assess the control robustness and performance of the developed scheme against the passive suspension as well as the H∞ -controlled SAVGS. The proposed µ-synthesis control scheme is proved to be more effective for realistic applications as it is capable of maintaining the suspension performance improvement regardless of variations of system parameters associated with the uncertainties, while the H∞ control performance tends to deteriorate when a notable deviation from the nominal values occurs.