A new integrated fault detection and control scheme of islanded DC microgrids: A resilient approach.

This paper presents a new resilient integrated fault detection and control module for a DC microgrid operating in islanded mode. The proposed design is unique in its ability to simultaneously improve microgrid reliability and mitigate variations through a multi-objective approach that considers both control and diagnosis objectives in the form of Linear Matrix Inequalities through a presented algorithm. The module is designed by setting out desired performance indices to ensure system stability, mitigate disturbances and uncertainties, and detect faults while controlling the DC-link voltage. Additionally, the module is robust to its own variations and capable of detecting non-compensable faults for further diagnosis. The efficacy of the proposed approach is demonstrated through a comparative study that highlights the vulnerability of robust design to parameter variations.

Adaptive backstepping quantized control for a class of unknown nonlinear systems.

In this paper, the stability problem for a class of nonlinear systems in the form of strict-feedback with applying input quantization has been addressed. By considering a sector-bounded hysteresis quantizer, signal quantization has been achieved. The employed quantizer can reduce the potential chattering which can occur in some approaches. By using a common Lyapunov function (CLF) and the backstepping method, a control scheme has been introduced to stabilize the uncertain nonlinear system. Compared with the recent papers, in order to handle the quantization error, one of the sector-bounding features has been utilized straightly instead of decomposing the quantized input into linear and nonlinear parts, in this case, the possible disturbance-like term has been ignored. The designed control scheme does not need the global Lipschitz assumption over the system mismatched nonlinearities. Besides, the asymptotic stability of system trajectories to the origin is guaranteed and the imposed restrictions over quantization design parameters such as quantization density have been eliminated. Finally, in the simulation results, the accuracy and efficiency of the this control scheme are shown.

Interconnection and damping assignment control based on modified actor-critic algorithm with wavelet function approximation.

Passivity-based control (PBC) is model-based, and as a result, it is affected by uncertainties. Besides, for some PBC designs, partial differential equations (PDEs) should be solved in order to obtain the parameters of the controller. Actor-critic (AC) algorithm has been used to regulate PBC parameters instantaneously and solve PDEs online. Despite the benefits of this algorithm, it cannot handle disturbance. The main purpose of this paper is to modify the AC algorithm with an online wavelet function approximation to improve its performance. The proposed method uses PBC and the modified AC algorithm to attenuate the effects of uncertainties. Moreover, the stability analysis is investigated for a nonlinear system. The results show that the new method can handle disturbance and uncertainties more proper than other methods.

Adaptive synchronization of chaotic systems with hysteresis quantizer input.

This paper proposes two new designing methods of adaptive controllers in order to synchronize uncertain nonlinear chaotic systems with input quantization. The hysteresis quantizer, which is a class of sector-bounded quantizers, has been used to quantize the control signal. This can avoid the possible chattering caused by some conventional controllers. Two adaptive robust schemes are proposed to accomplish chaos synchronization of master and slave systems in presence of unknown parameters and uncertainties. The proposed controllers in this paper do not require the restrictive conditions for quantized parameters in contrast to some available control techniques for systems with input quantization. In addition, asymptotic stability of the proposed adaptive controllers is also verified analytically. Finally, the proposed controller is applied to a chaotic gyroscope and also to a Micro-Electro-Mechanical-System to validate its efficiency and robustness.

Dual-user nonlinear teleoperation subjected to varying time delay and bounded inputs.

A novel trilateral control architecture for Dual-master/Single-slave teleoperation system with taking account of saturation in actuators, nonlinear dynamics for telemanipulators and bounded varying time delay which affects the transmitted signals in the communication channels, is proposed in this paper. In this research, we will address the stability and desired position coordination problem of trilateral teleoperation system by extension of (nP+D) controller that is used for Single-master/Single-slave teleoperation system. Our proposed controller is weighted summation of nonlinear Proportional plus Damping (nP+D) controller that incorporate gravity compensation and the weights are specified by the dominance factor, which determines the supremacy of each user over the slave robot and over the other user. The asymptotic stability of closed loop dynamics is studied using Lyapunov-Krasovskii functional under conditions on the controller parameters, the actuator saturation characteristics and the maximum values of varying time delays. It is shown that these controllers satisfy the desired position coordination problem in free motion condition. To show the effectiveness of the proposed method, a number of simulations have been conducted on a varying time delay Dual-master/Single-slave teleoperation system using 3-DOF planar robots for each telemanipulator subjected to actuator saturation.