This paper focuses on adaptive robust vibration control for flexible riser systems affected by input nonlinearities and unknown external disturbances. An auxiliary system is constructed and adjusted to develop a boundary adaptive robust control for restraining the vibrational offset and eliminating the effect of input nonlinearities. Besides, an adaptive law of boundary disturbance upper-bound is constructed together with the vibration control strategy to estimate the magnitude of unknown boundary disturbance. Further, the convergence of states and stability of the system are ensured with the developed control scheme. By choosing the proper control parameters, the control performance is verified with the obtained simulation results.

This article presents a robust ${H_{∞}}$ feedback compensator design approach for semilinear parabolic distributed parameter systems (DPSs) with external disturbances via mobile actuators and sensors. An ${H_{∞}}$ performance constraint is introduced to deal with the external disturbances from the model and measurement noise. Two types of feedback compensators are designed in terms of the collocated and noncollocated mobile actuators and sensors. By the Lyapunov direct technique, some sufficient conditions based on LMI constraints are proposed for the exponential stability under ${H_{∞}}$ performance constraints in the L²-norm. Moreover, the open-loop and closed-loop well-posedness of the semilinear DPSs with external disturbances are analyzed via the ${C_{0}}$ -semigroup theory approach. Finally, extensive numerical simulation results for semilinear DPSs with external disturbances via collocated and noncollocated mobile actuators and sensors are shown to verify the effectiveness of the proposed method.

This paper presents a framework of output feedback stabilization of an axially moving accelerated system influenced by exogenous disturbances. Based on the flexible-rigid coupled dynamical model of the system, a boundary output feedback control is developed to reduce the vibration and estimate the boundary disturbance by fusing Lyapunov's synthetic approach, disturbance rejection theory, and observer technique. Under the developed control, the exponential convergence of system state observer errors and uniformly ultimately bounded stability of the controlled system can be demonstrated adopting rigorous theoretical analysis, and the control performance of the developed control method is verified by simulation results.

A new efficient root-propagator method based on a uniform linear antenna array is proposed to estimate the directions of arrival (DOAs) and ranges of near-field sources with-out a priori knowledge of the source number. A non-Hermitian matrix is firstly designed which allows the applications of rooting methods. Then by constructing two propagators, the parameter estimation for near-field sources can be achieved through rooting methods in a decoupled way without eigenvalue decomposition (EVD) and spectrum searches. At last, the importance of the priori source number to source localization problems is studied, and specifically, an improvement is proposed to get rid of this dependence. Numerical examples are carried out to show the effectiveness and validate the theoretical analysis of the proposed root-propagator method. The results show that the proposed method provides more superior performance for near-field source localization than other existing similar methods. Even in the case without a priori knowledge of the source number, the performance of the proposed method is still satisfactory.