Practical Tracking Of Signals For A Class Of Nonminimum-phase Nonlinear Systems

As one of the major problems in control theory, signal tracking is to find suitable control laws to make the output of closed-loop system track the desired signal. Sampled-data control, which is different from conventional control methods for continuous signal, is to design a discrete controller to control continuous system by choosing a sufficiently small sampling interval. Recently, signal tracking problem is attracting more and more attention among researchers and has been widely used in many applications.While most of existing work on practical tracking is based on minimum-phase systems, this dissertation is focused on a class of nonminimum-phase nonlinear systems with lower-triangular structures and extends previous work to a solution of practical tracking by sampled-data control. The nonminimum-phase systems employed in this dissertation is composed of zero-dynamics and nonzero-dynamics. Following the procedure of output feedback control, with the assumption s that the nonlinear function of zero-dynamics satisfies global linear growth and the rest meets global lipschitz condition, a desired state observer is first designed and then controllers for zero-dynamics and nonzero-dynamics are derived. The third step is to analyze the stability of the whole system based on Lyapunov theory, which successfully obtains the continuous control law for this class of systems during practical tracking of desired signal. The next step is to discretize the continuous control law to derive the sampled-data controller and simulate these two controllers using Matlab. Finally, analysis and validation of theories obtained in this work is illustrated.The work of this dissertation is of great value in researches and can be widely used in many practical applications like power grid harmonic suppression and dynamic tracking to the robots of heart operations.