Disturbance observer-based delayed robust feedback control design for a class of uncertain variable fractional-order systems: Order-dependent and delay-dependent stability.

This work addresses the stabilization of variable fractional-order (VFO) neutral-type systems with structure perturbations and unknown disturbance signals using the feedback control approach. The goal is to design disturbance-observer-based delayed state- and output-feedback controllers to achieve robust stability of such VFO systems. The proposed controller consists of two parts, namely a primary controller based on the linear feedback technique, and an auxiliary controller based on the disturbance observer. A disturbance observer is developed to estimate the disturbance signal, which is generated by an exogenous system. Based on matrix inequalities, order-dependent and delay-dependent conditions are formulated via FO Lyapunov theory that guarantee the robust stability of the closed-loop system. Simulations verify the main results.

Compound FAT-based prespecified performance learning control of robotic manipulators with actuator dynamics.

In the framework of the backstepping algorithm, this article proposes a new function approximation technique (FAT)-based compound learning control law for electrically-driven robotic manipulators with output constraint. The Fourier series expansion is adopted in the learning-based design to approximate unknown terms in the system description. The accuracy of FAT approximation is also studied by defining an identification error, which is derived from a serial-parallel identifier. Furthermore, the output constraint is taken into account by integrating the error transformation, the performance function and the dynamic surface control in a compact framework. Following this idea, new compound adaptation laws are then constructed. The proposed compound learning controller confirms that all the signals of the overall system are uniformly ultimately bounded, ensuring the tracking error within the predefined bounds during operation. Different simulation scenarios applied to a robotic manipulator with motor dynamics illustrate the capability of the control algorithm.

Guaranteed cost-based feedback control design for fractional-order neutral systems with input-delayed and nonlinear perturbations.

Time delay in actuators is mainly caused by electrical and mechanical components. The effect is visible in the system response particularly when changing in the input command. Therefore, input delay is a problem in the control system design that must be taken into account. Besides, ignoring uncertainty in the dynamic models may compromise the controller design. Thus, how to mitigate the effect of this issue on the system stability and performance is a challenging topic. This article deals with the stabilization of fractional neutral systems considering input-delayed and nonlinear perturbations using the guaranteed cost-based feedback control technique. The main focus is to design the state- and output-feedback controllers to achieve a good performance. The stability criteria are formulated in the Lyapunov sense, which are described in terms of matrix inequalities. The proposed idea is validated using simulations.

LMI-Based Delayed Output Feedback Controller Design for a Class of Fractional-Order Neutral-Type Delay Systems Using Guaranteed Cost Control Approach.

In this research work, we deal with the stabilization of uncertain fractional-order neutral systems with delayed input. To tackle this problem, the guaranteed cost control method is considered. The purpose is to design a proportional-differential output feedback controller to obtain a satisfactory performance. The stability of the overall system is described in terms of matrix inequalities, and the corresponding analysis is performed in the perspective of Lyapunov's theory. Two application examples verify the analytic findings.

Robust stability of uncertain fractional order systems of neutral type with distributed delays and control input saturation.

Time delay occurs naturally due to the limited bandwidth of any real-world system. However, this problem can deteriorate the system performance and can even result in system instability. Input saturation is also an essential issue due to the energy constraint in real actuators that makes the control design procedure more difficult. This article concerns with the stability of uncertain fractional order (FO) delay systems of neutral type including structured uncertainties, distributed delays and actuator saturation. A Lyapunov-Krasovskii functional allows the formulation of the conditions to insure the asymptotic robust stability of such systems via the linear matrix inequalities (LMI) and to compute the gain of a state feedback controller. In addition, by using the cone complementarity linearization method, we obtain the controller gains that extend the domain of attraction. Several simulations validate the theoretical analysis.

Stochastic H∞ finite-time control of networked cascade control systems under limited channels, network delays and packet dropouts.

Communication channel in the control loop brings new challenging topics that cause the controller design for the system very complicated. Data packet dropout, delay and limited channel are the main inevitable problems that can significantly degrade the system performance. Besides, stability analysis of such systems over infinite time interval using the Lyapunov stability concept imposes significant restrictions in practice due to control input saturation. The purpose of this paper is to introduce a control algorithm for stabilizing the discrete-time networked cascade control systems to suppress the detrimental effects of limited channel, delay and data packet dropout by means of finite-time H∞ control. Non-uniformly distributed nature of the delay together with packet dropout are modeled as a Bernoulli distributed white sequence. Finite-time boundedness and stochasticH∞finite-time stability are demonstrated by designing a switching state-feedback controller. Simulations are given to show the proposed controller under the network imperfections.

Delay-dependent stability analysis of the QUAD vector field fractional order quaternion-valued memristive uncertain neutral type leaky integrator echo state neural networks.

This paper studies the robust stability analysis for a class of memristive-based neural networks (NN). The NN consists of a fractional order neutral type quaternion-valued leaky integrator echo state with parameter uncertainties and time-varying delays. First, the quaternion-valued leaky integrator echo state NN with QUAD vector field activation function is transformed into a real-valued system using a linear mapping function. Then, the Lyapunov-Krasovskii functional is adopted to derive the sufficient conditions on the existence and uniqueness of Filippov solution of the NN equilibrium point. The delay-dependent robust stability analysis of such NN is provided with the help of linear matrix inequality technique. Finally, the theoretical results are validated by means of a numerical example.

Finite-time H∞ control of uncertain networked control systems with randomly varying communication delays.

This paper is concerned with the problem of finite-time H∞ stability analysis of uncertain discrete-time Networked Control Systems (NCSs) with varying communication delays in a random fashion. Both measurement and actuation delays are modeled by two independent Bernoulli distributed white sequences. A dynamic output feedback controller is designed to realize finite time control for this class of NCSs with prescribed H∞ performance level. An iterative algorithm is developed to compute the controller's parameters by means of the Cone Complementarity Linearization Method (CCLM). The validity and feasibility of the proposed stability criterion are confirmed via numerical simulation examples.