Aspects of achievable performance for quarter-car active suspensions

In this paper, constraints on the transfer functions from the road disturbance to the vertical acceleration, the suspension travel, and the tire deflection are derived for a quarter-car active suspension system using the vertical acceleration and/or the suspension travel measurements for feedback. The derived constraints complement the similar constraints in the literature. By using the factorization approach to feedback stability, it is shown that tire damping couples the motions of the sprung and unsprung masses; and eliminates a constraint at the wheel-hop frequency. The influence of tire damping on the design of an active suspension system for a quarter-car model by a mixture of the LQG methodology and the interpolation approach is also illustrated.