In this paper, we study the tracking control problem for a nonlinear system in which the zero dynamics may be unstable. The objective here is to approximate the nonlinear system by another singularly perturbed system by using a small singular perturbation parameter  . The proposed approach is based on the methodology of exact input output linearization control, the integrator backstepping appr...

An important statement in Quantitative Feedback Theory(QFT) is that the nominal plant can be chosen arbitrarily whether or not it is a member of the plant set. Based on this statement, a design method for non-minimum phase and unstable plants proposed by Horowitz is to choose the stable minimum phase plant as the nominal plant. This report shows this statement is incorrect by several counterexa...

A new class of critical points, termed as perpetual points, where acceleration becomes zero but the velocity remains non-zero, are observed in dynamical systems. The velocity at these points is either maximum or minimum or of inflection behavior. These points also show the bifurcation behavior as parameters of the system vary. These perpetual points are useful for locating the hidden oscillatin...

A sliding mode control scheme is developed for nonlinear, non-minimum phase, uncertain, input-delay processes. The proposed scheme, which integrates a time-advanced nonlinear predictor and a statically equivalent output map, is able to compensate the process’s input-delay and to circumvent the negative effect of inverse response. The convergence properties of the proposed sliding mode control s...

In this paper, a modified local optimal control approach is proposed for multivariable systems. As for unknown plant dynamics, system identification must be performed to obtain a model based on which the local optimal controller is designed and implemented. The proposed method guarantee closed loop stability characteristic when dealing with non-minimum phase plant which is a considerable advant...

A new approach for the automatic generation of a dynamic feedforward control law for nonlinear dynamic systems represented by discrete-time local model networks (LMN) is proposed. The generic model structure of LMNs offers the opportunity to apply such a general and automated approach for model inversion, even when the overall model complexity may be high. LMNs can represent nonlinear dynamic s...

This paper presents a composite controller for tip position tracking of flexible link manipulators. The main control challenge for flexible link manipulators is the non-minimum phase characteristics of the system. In this regard, an inner/outer control structure is proposed. As opposed to previous research in this area, the desired reference trajectory is robustly modified in an online scheme t...

Recursive inverse filtering with non-stationary filters is becoming a useful tool in a range of applications, from multi-dimensional inverse problems to wave extrapolation. I formulate causal non-stationary convolution and combination and their adjoints in such a way that it is apparent that the corresponding non-stationary recursive filters are true inverse processes. Stationary recursive inve...

In the field of linear time-invariant systems, a process is identified as a nonminimum phase (NMP) system if its transfer function has at least one right half-plane (RHP) zero, or a RHP pole, or a time delay. Among others, systems with RHP zero(s) constitute a very important category of NMP systems, both from theoretical and practical point of view. Such zeros appear in many realworld systems s...