Eduardo V. L. Nunes

Global Exact Tracking for Uncertain Systems Using Output-Feedback Sliding Mode Control

This note presents a solution to the problem of global exact output tracking for uncertain linear plants with arbitrary relative degree using output-feedback sliding mode control. The key idea to overcome the relative degree obstacle is to introduce a hybrid compensator by combining, through switching, a standard lead filter with a robust exact differentiator, based on higher-order sliding modes, achieving uniform global exponential practical stability and asymptotic exact tracking.

Global tracking for robot manipulators using a simple causal pd controller plus feedforward

This paper shows that a well-known causal PD controller plus feedforward solves the global output feedback tracking control problem of robot manipulators, by requiring only the existence of the robot natural damping, no matter how small. To this end, we first demonstrate that a robot controlled by a causal PD is globally input-to-state stable (ISS) with respect to a bounded input disturbance. Then, we prove that the addition of a feedforward compensation renders the error system uniformly globally asymptotically stable. Furthermore, we present a possible extension to more general nonlinear systems and also to uncertain systems.

Mobile robot navigation using sensor fusion

This paper considers the localization and navigation of a mobile robot. The control strategy is based on a nonlinear model predictive control technique that utilizes the Newton method. The robot localization is obtained using information from odometric and ultrasonic sensors through a Kalman filter. Simulation and experimental results illustrate the efficacy of the proposed method.

Output-feedback sliding mode control for global asymptotic tracking of uncertain systems using locally exact differentiators

This paper generalizes and validates experimentally the applicability of a recently developed output-feedback sliding mode tracking controller based on a hybrid switching compensator. The proposed controller can deal with plants of arbitrary relative degree by using a locally exact differentiator of higher order based on second order sliding modes (SOSM). Global stability and asymptotic exact tracking are achieved by combining, through switching, a standard lead filter with the SOSM exact differentiator. Simulations and experimental results are presented to illustrate the applicability of the hybrid scheme in real conditions

Global exact tracking for uncertain MIMO linear systems by output feedback sliding mode control

Abstract This paper presents a solution to the problem of global exact output tracking for uncertain MIMO (multiple-input–multiple-output) linear plants with non-uniform arbitrary relative degree using output feedback sliding mode control. The key idea to overcome the relative degree obstacle is to generalize our previous hybrid estimation scheme to a multivariable version by combining, through switching, a standard linear lead filter with a non-linear one based on robust exact differentiators, achieving uniform global exponential practical stability and exact tracking.

Multivariable MRAC Design Without Gain Symmetry Conditions Using a Stabilizing Multiplier

A new multivariable MRAC design for plants of arbitrary relative degree, which does not require a stringent symmetry assumption related with the plant high frequency gain matrix, is presented. In contrast to previous results, the new solution does not involve additional parametrization and filtering, being thus close in structure and complexity to conventional solutions. Instead of the fragile symmetry assumption, a less restrictive and robust condition is required, which can be achieved using a multiplier.

Global output feedback tracking controller based on hybrid estimation for a class of uncertain nonlinear systems.

A global output-feedback tracking controller based on a hybrid estimation scheme is proposed for a class of uncertain nonlinear systems. The hybrid estimation scheme combines a general estimator, that provides an input-to-state practical stabilizing control law with a locally exact differentiator, based on higher-order sliding modes. The key idea is to design a switching law to select between both estimators in such a way that stability properties are preserved and in addition exact tracking is achieved. As an example, the proposed control scheme is shown to solve the global output feedback tracking control problem of a class of uncertain Euler-Lagrange systems.

Output-Feedback Multivariable Global Variable Gain Super-Twisting Algorithm

A novel output-feedback super-twisting algorithm design is proposed for uncertain multivariable plants. In order to allow global finite-time exact tracking in the presence of a rather general class of matched nonlinear disturbances which may depend on measured and/or unmeasured states, the algorithm is designed with variable gains. This represents a significant extension of a recently proposed nondecoupled multivariable super-twisting algorithm, based on state-feedback with fixed gains, to the case of output-feedback with variable gains.

Global exact tracking for uncertain multivariable linear systems by output feedback sliding mode control

This paper presents a solution to the problem of global exact output tracking for uncertain multivariable linear plants with non-uniform arbitrary relative degree using output feedback sliding mode control. The key idea to overcome the relative degree obstacle is to generalize our previous hybrid estimation scheme to a multivariable version by combining, through switching, a standard linear lead filter with a nonlinear one based on robust exact differentiators, achieving uniform global exponential practical stability and exact tracking.

Binary robust adaptive control for global tracking of uncertain systems with unknown high-frequency-gain sign

An adaptive output-feedback controller is proposed for uncertain linear systems without a priori knowledge of the plant high-frequency-gain sign. The system parametric uncertainties are compensated by a robust adaptive strategy named binary adaptive control which combines the good transient properties and robustness of Sliding Mode Control with the desirable steady-state properties of parameter adaptive systems. An important advantage with respect to sliding mode control is that the proposed controller generates a continuous signal so that control chattering is avoided. The effective way of tackling unknown high-frequency-gain sign is employing monitoring functions. The developed adaptive control guarantees global stability of the closed-loop system and exact tracking of a reference signal. Numerical simulations illustrate the efficacy of the proposed approach.