Output Tracking Of Systems Research Articles

Robust Adaptive Nonlinear Control of Systems with time Varying Relay Nonlinearity

An approximate linearizing control scheme for obtaining output tracking of systems including the time varying relay nonlinearity is considered together with the observability assumption on state variables in this paper. In the first place, it is provided that the time varying relay nonlinearity can be approximately modeled as a smooth nonlinear functional form , depending linearly on an unknown constant parameter, and disturbed with a boundary uncertainty. Then we present that, while the parameter estimate error and the tracking error of closed-loop system are achieved in arbitrary small range, the regulator considered in this note ensures boundedness of all state variables, and robustness to the uncertainty bounded, using a robust adaptive control approach of nonlinear systems via approximate linearization , too.

Robust semi-global output tracking for nonlinear singularly perturbed systems

In this work, a robust controller design methodology for a broad class of singularly perturbed nonlinear systems with time-varying uncertainties is developed. When the fast subsystem is stabilizable and the slow subsystem is input/output linearizable with input-to-state stable (ISS) inverse dynamics, the developed state feedback controller guarantees boundedness of the trajectories of the closed-loop system and robust output tracking with arbitrary degree of asymptotic attenuation of the effect of uncertainty on the output, for initial conditions and uncertainties in an arbitrarily large compact set, so long as the singular perturbation parameter is sufficiently small. The controller is a continuous function of the state of the system and its construction requires the knowledge of bounding functions on the size of uncertainty. The developed method is applied to a non-isothermal continuous stirred tank reactor with fast jacket dynamics.

Decentralized stabilization and output tracking of large-scale uncertain systems

A method for the design of linear constant decentralized robust controllers for a class of uncertain interconnected systems is presented in this paper. The uncertainties are assumed to satisfy the general matching conditions for each decomposed subsystem, and both stabilizing control and output tracking control are considered here. In the former, the uncertainties may be time-varying, and the system can be exponentially stabilized. In the latter, with the assumption of time-invariant uncertainties, the system can approach the constant reference input and reject constant disturbances with a prescribed convergence rate.

A P-type iterative learning controller for robust output tracking of nonlinear time-varying systems

A P-type iterative learning controller using the concept of the forgetting factor and current error modification is proposed in this paper for a class of uncertain nonlinear time-varying systems. The robustness, convergence and performance of this P-type learning control scheme are completely studied. It is shown that the uniformly boundedness between the system output and the desired output is achieved in each iterate. Under some conditions on the uncertainties, the residual set of the tracking error on the final iterate can be shown to be a class K function of the forgetting factor. When all the uncertainties and the forgetting factor tend to zero, the system output will converge uniformly to the desired one.

Provident control of an electro-hydraulic servo with experimental results

In this study, we propose a novel variable structure control method for output tracking of uncertain nonlinear systems, with experimental application to an electro-hydraulic servo system. First we perform a state transformation to convert the system to the normal form. Then we apply a method that we have termed provident control, so called because of its frugal but judicious use of the input when compared to other variable structure methods which use large control authority to drive the state to the sliding surface. This method combines variable structure control with variable structure adaptation and performs switching with hysteresis between the structures so as to avoid a sliding mode. By completely separating the reaching and tracking phases, a two-degree-of-freedom controller is obtained. Experimental results indicate significant performance improvement over the well-known boundary layer sliding control, together with robustness against parametric uncertainty and external disturbances.

A different look at output tracking: control of a vtol aircraft

In this paper we propose a scheme for output tracking of nonminimum phase flat systems. The technique, which is applicable even in the minimum phase case, uses an inverse trajectory for feedforward which is stabilized by a state tracker built using the flat output. In contrast to approximate-linearization based control [Hauser, J., S. Sastry and G. Meyer (1992). Nonlinear control design for slightly nonminimum phase systems: application to v/stol aircraft. Automatica, 28, 665–679], which yields good performance in slightly nonminimum phase systems, our approach applies equally well to slightly and strongly nonminimum phase systems. The proposed control scheme and the approximate-linearization based controller are applied to a Vertical Take Off and Landing (VTOL) aircraft example and the performances are compared.

A new variable structure controller for affine nonlinear systems with non-matching uncertainties

The problem of output tracking in SISO uncertain non-autonomous nonlinear systems is treated in this study. It is shown that a nonlinear system experiencing non-matching disturbances and uncertainties can be transformed to a form similar to the normal form. Then, a novel variable structure controller with disturbance estimation and parameter adaptation is presented. This controller, while preserving the robustness properties of sliding control, avoids a sliding mode and generates a continuous control signal, which results in close output tracking.

On robust regulation via sliding mode for nonlinear systems

A robust control scheme for the output tracking of nonlinear systems is proposed. The scheme is based on the nonlinear regulator theory and the sliding mode approach. It is shown that if perturbations and/or uncertainties appear on the system, the sliding mode controller is able to perform approximate asymptotic tracking, in the sense that the output tracking error remains bounded, provided the upper bounds of the uncertain terms are known.

Unified adaptive control of non-minimum-phase systems Part 2. Target tracking and dynamic compensation

For discrete time-invariant non-minimum-phase deterministic linear systems, a class of unified adaptive control algorithms is presented and global convergence is established. Under suitable conditions, it is shown that this class of algorithms will ensure that the system input and output remain bounded for all time; the system output tracking error converges to zero; and on-line closed-loop poles eventually converge to the desired position.

Output tracking in multivariable nonlinear systems

In this note the class of functions which can appear as outputs is identified for a class of multivariable nonlinear systems. For these systems we construct right-inverse systems which act as prefilters.

Output regulation and tracking in linear multivariable systems

It is shown that the related questions of output tracking and output regulation (with and without input sensor measurement), all with associated internal stability, can be resolved via a single polynomial matrix formulation which employs the recently developed notion of skew prime polynomial matrices. In particular, the primary condition which must be satisfied in all cases is that <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R(s)</tex> , the plant numerator matrix, and a matrix where zeros represent the modes of the exogenous system, be externally skew prime. This observation is then elucidated in light of a new internal model principle.