  Besides parametric uncertainties and disturbances, the unmodeled dynamics and
time delay at the input are often present in practical systems, which cannot be
ignored in some cases. This paper aims to solve output feedback tracking
control problem for a class of nonlinear uncertain systems subject to unmodeled
high-frequency gains and time delay at the input. By the additive
decomposition, the uncertain system is transformed to an uncertainty-free
system, where the uncertainties, disturbance and effect of unmodeled dynamics
plus time delay are lumped into a new disturbance at the output. Sequently,
additive decomposition is used to decompose the transformed system, which
simplifies the tracking controller design. To demonstrate the effectiveness,
the proposed control scheme is applied to three benchmark examples.
