  In this paper, a new control scheme, called additive state decomposition
based tracking control, is proposed to solve the tracking (rejection) problem
for rotational position of the TORA (a nonlinear nonminimum phase system). By
the additive state decomposition, the tracking (rejection) task for the
considered nonlinear system is decomposed into two independent subtasks: a
tracking (rejection) subtask for a linear time invariant (LTI) system, leaving
a stabilization subtask for a derived nonlinear system. By the decomposition,
the proposed tracking control scheme avoids solving regulation equations and
can tackle the tracking (rejection) problem in the presence of any external
signal (except for the frequencies at +1 or -1) generated by a marginally
stable autonomous LTI system. To demonstrate the effectiveness, numerical
simulation is given.
