Wallace M. Bessa

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Sliding mode control, due to its robustness against modelling imprecisions and external disturbances, has been successfully employed to the dynamic positioning of remotely operated underwater vehicles. In order to improve the performance of the complete system, the discontinuity in the control law must be smoothed out to avoid the undesirable chattering(More)
The dynamic behavior of underwater robotic vehicles can be greatly influenced by the nonlinear dynamics of the vehicle thrusters. In this way, the implementation of a good control strategy for the thruster subsystem is essential for the accurate control of the entire robotic vehicle. It was already shown in the literature that without compensation for(More)
Sliding mode control is a very attractive control scheme because of its robustness against modelling imperfections and external disturbances. It has been successfully employed to the dynamic positioning of remotely operated underwater vehicles. In such situations, the discontinuities in the control law must be smoothed out to avoid the undesirable(More)
This paper presents a detailed discussion about the convergence properties of a variable structure controller for uncertain single-input–single-output nonlinear systems (SISO). The adopted approach is based on the sliding mode control strategy and enhanced by an adaptive fuzzy algorithm to cope with modeling inaccuracies and external disturbances that can(More)
This paper presents a nonlinear controller for uncertain single-input–single-output (SISO) nonlinear systems. The adopted approach is based on the feedback lineariza-tion strategy and enhanced by a fuzzy inference algorithm to cope with modeling inaccuracies and external disturbances that can arise. The boundedness and convergence properties of the tracking(More)
The development of accurate control systems for underwater robotic vehicles relies on the adequate compensation of thruster dynamics. Without compensation, the closed-loop positioning system can exhibit limit cycles. This undesired behaviour may compromise the overall system stability. In this work, a fuzzy sliding-mode compensation scheme is proposed for(More)
The dead-zone is one of the most common hard nonlinearities in industrial actuators and its presence may drastically compromise control systems stability and performance. Due to the possibility to express specialist knowledge in an algorithmic manner, fuzzy logic has been largely employed in the last decades to both control and identification of uncertain(More)