Trajectory Control in Non-Minimum Phase Plants

Non-minimum phase plants are always difficult to control. Recently, the so-called Linear Algebra Based Control Design methodology has been used for trajectory control of linear and nonlinear plants, being initially limited to minimum phase plants. In this work, the approach is extended to deal with unstable zero dynamics plants. First, the case of linear plants is analyzed, considering the appearance of a non minimum phase zero. A solution is proposed to deal with the zero in the positive real axis, requiring a reference signal known in advance. Then, the approach is applied to nonlinear plants where the unstable zero dynamics is determined by a single parameter in the plant model. Simulations are included to illustrate the procedure.