Nested plant/controller optimization with application to combined passive/active automotive suspensions

This paper addresses the coupling between the plant and control optimization problems for a suspension comprising both passive and active components. Suspension dynamics are modeled using a two degree-of-freedom, linear and time-invariant quarter-car model whose ability to capture the influence of the passive stiffness on rattle space depends on the ground disturbance's spectral density. Nested optimization, a strategy that guarantees system optimality, is presented and used to find the optimal suspension system design. The design exhibits superior performance compared to its passive, active and sequentially optimized passive/active counterparts because it accounts for the coupling between the passive and active suspension optimization problems.