Bounded Back-Stepping Controller For Nonlinear Systems

Muhammad Nizam , Kamarudin (2015) Bounded Back-Stepping Controller For Nonlinear Systems. PhD thesis, Universiti Teknikal Malaysia Melaka.

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Abstract

Back-stepping controller is a recursive design approach that offers flexible design steps to stabilize nonlinear systems. However, the well known back-stepping control technique is a full state feedback that is highly dependent to system parameters and system dynamics. As such, back-stepping approach normally produces large magnitude control signal which at times implausible that may lead to actuator saturation. In order to overcome this drawback, this thesis proposes a new bounded back-stepping controller technique. The design is based on a classical Lyapunov with LaSalle invariance set principle. LaSalle invariance set principle relaxes the negative definiteness of the derivative of a Lyapunov function while deducing the asymptotic stability of closed loop system. Hence, system trajectories are confined inside the stability region. In the controller design, the universal Sontag’s formula is improved and merged with the back-stepping technique. To handle with the uncertainties and exogenous disturbances, a pseudo function is utilized during the Lyapunov redesign phase. In order to observe the efficacy of the proposed method, a strict feedback numerical nonlinear system with time varying exogenous disturbance is stabilized. The effectiveness of the proposed method is shown through control signal which can be bounded without impact to the closed loop stability and robustness. That is, the proposed control method guarantees global asymptotic stability upon perturbation in initial states with invariant set of solution. The proposed control method also guarantees the asymptotic disturbance rejection and it also robust towards uncertainties. In addition, the control law is smooth and continuous. The proposed method is used to develop a fixed pitch variable speed control for a numerical representation of a two-mass wind turbine system that focuses on the nacelle. Simulation results show that the proposed approach requires less control energy to guarantee the asymptotic tracking of turbine rotor speed for optimum tip-speed-ratio. Thus, it produces a maximum power output from the wind turbine while preserving robustness towards wind intermittent.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Control theory, Nonlinear systems
Subjects: Q Science > Q Science (General)
Q Science > QA Mathematics
Divisions: Library > Tesis > FKE
Depositing User: Mohd Hannif Jamaludin
Date Deposited: 05 Aug 2016 02:54
Last Modified: 05 Aug 2016 02:54
URI: http://eprints.utem.edu.my/id/eprint/16884
Statistic Details: View Download Statistic

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