For a simple vehicle active suspension system complete optimality and
zero steady state body displacements may be achieved if the axle and b
ody accelerations, and other easily measured quantities, are included
in the performance index. Apart from not requiring an observer, this a
lso allows the optimal feedback gains to be determined for an arbitrar
y body spring rate. In a theoretical example, model parameters matchin
g those of an experimental test rig are employed. The results of compu
ter simulations, with and without an electrohydraulic servovalve and a
ctuator, are compared to demonstrate the effects of inner loop gain on
force control. Aspects of the system behaviour including lockup are c
ommented upon.