2-D path following for fixed wing UAV using global fast terminal sliding mode control.

This paper considers the finite time convergence problem of 2-D path following for fixed wing unmanned air vehicle. Firstly, the UAV path following model is divided into an outer guidance loop and an inner control loop. Then, the guidance loop and control loop controllers of the UAV are derived by global fast terminal sliding mode control technique, which is able to guarantee the system state variables converge to expected values in finite time and eliminate the chattering phenomenon caused by the switching control action. Furthermore, the stability of the two-loops system is proven by Lyapunov stability theory. Finally, the simulation results are shown to verify the performance of the proposed method.

Attack-Resilient Distributed Nash Equilibrium Seeking of Uncertain Multiagent Systems Over Unreliable Communication Networks.

This article investigates the distributed Nash equilibrium (NE) seeking problem of uncertain multiagent systems in unreliable communication networks. In this problem, the action of each agent is subject to a class of nonlinear systems with uncertain dynamics, and the communication network among agents will be affected by the nonperiodic denial of service (DoS) attacks. Note that, in this insecure network environment, the existence of DoS attacks will directly destroy the connectivity of the network, which leads to performance degradation or even failure of the most existing distributed NE seeking algorithms. To address this problem, we propose a two-stage distributed NE seeking strategy, including the attack-resilient distributed NE estimator and the neuroadaptive tracking controller. The estimator based on the projection subgradient method and the consensus protocol can converge exponentially to virtual NE against DoS attacks. Then, the neuroadaptive tracking controller is designed for uncertain multiagent systems with the output of the estimator as the reference signal such that the actual action of all agents can reach NE. Based on the Lyapunov stability theory and improved average dwell time automaton, the stability of the estimator and the controller is proven, and all signals in the closed-loop system are uniformly bounded. Numerical examples are presented to verify the effectiveness of the proposed strategy.

Decentralized coordinated optimal guaranteed cost control for a roll-to-roll web machine.

This article investigates a coordinated optimal guaranteed cost control (DCOGCC) for a multi-motor roll-to-roll web machine with time-varying and uncertain parameters. The state-space oriented DCOGCC law is designed to ensure that each subsystem of the web machine is stable and the upper bound of performance index is minimum. Linear matrix inequality (LMI) conditions to guarantee the stability of the systems with DCOGCC are derived. A decentralized model is adopted by regarding the entire machine as a synthetic system, then the original decentralized model is transformed into an equivalent one. By choosing appropriate information of consecutive subsystems as coordination variables, the DCOGCC scheme may attenuate the interaction effects between subsystems. The results of some simulations and experiments are given to verify the feasibility and effectiveness of the DCOGCC.

Distributed Algorithm Design for Nonsmooth Resource Allocation Problems.

This paper investigates resource allocation problems, where the cost functions of agents are nonsmooth and the decisions of agents are constrained by heterogeneous local constraints and network resource constraints. We design a distributed subgradient-based algorithm to achieve the optimal resource allocation. Moreover, we analyze the convergence of the algorithm to the optimal solution. The algorithm can solve resource allocation problems with strongly convex cost functions and weight-balanced digraphs, as well as resource allocation problems with strictly convex cost functions and connected undirected graphs. With the algorithm, the decisions of all agents asymptotically converge to the optimal allocation. Simulation examples verify the effectiveness of the algorithm.

Distributed Generalized Nash Equilibrium Seeking Algorithm Design for Aggregative Games Over Weight-Balanced Digraphs.

In this paper, two aggregative games over weight-balanced digraphs are studied, where the cost functions of all players depend on not only their own decisions but also the aggregate of all decisions. In the first problem, the cost functions of players are differentiable with Lipschitz gradients, and the decisions of all players are coupled by linear coupling constraints. In the second problem, the cost functions are nonsmooth, and the decisions of all players are constrained by local feasibility constraints as well as linear coupling constraints. In order to seek the variational generalized Nash equilibrium (GNE) of the differentiable aggregative games, a continuous-time distributed algorithm is developed via gradient descent and dynamic average consensus, and its exponential convergence to the variational GNE is proven with the help of Lyapunov stability theory. Then, another continuous-time distributed projection-based algorithm is proposed for the nonsmooth aggregative games based on differential inclusions and differentiated projection operations. Moreover, the convergence of the algorithm to the variational GNE is analyzed by utilizing singular perturbation analysis. Finally, simulation examples are presented to illustrate the effectiveness of our methods.

Robust H∞ attitude tracking control of a quadrotor UAV on SO(3) via variation-based linearization and interval matrix approach.

This paper deals with the attitude tracking control of quadrotor unmanned aerial vehicles (UAV) with uncertainties and external disturbances. The control system is expressed on the special orthogonal group, SO(3), to avoid singularities and ambiguities associated with Euler angles and quaternions respectively. It is also the basis for achieving large angle tracking and complex UAV maneuver. Meanwhile, it greatly reducing the complexity of the controller design via variation-based linearization. And the approach of interval matrix is introduced to solve problems of controller online calculation and reduced control accuracy caused by uncertain parameters in model. The proposed robust H∞ control system can exponential asymptotically follow a desired attitude trajectory in the presence of unstructured bounded disturbances. Finally, several simulation results are provided to validate the effectiveness, advantages and robustness of the proposed method.

Decentralized coordinated control of elastic web winding systems without tension sensor.

In elastic web winding systems, precise regulation of web tension in each span is critical to ensure final product quality, and to achieve low cost by reducing the occurrence of web break or fold. Generally, web winding systems use load cells or swing rolls as tension sensors, which add cost, reduce system reliability and increase the difficulty of control. In this paper, a decentralized coordinated control scheme with tension observers is designed for a three-motor web-winding system. First, two tension observers are proposed to estimate the unwinding and winding tension. The designed observers consider the essential dynamic, radius, and inertial variation effects and only require the modest computational effort. Then, using the estimated tensions as feedback signals, a robust decentralized coordinated controller is adopted to reduce the interaction between subsystems. Asymptotic stabilities of the observer error dynamics and the closed-loop winding systems are demonstrated via Lyapunov stability theory. The observer gains and the controller gains can be obtained by solving matrix inequalities. Finally, some simulations and experiments are performed on a paper winding setup to test the performance of the designed observers and the observer-base DCC method, respectively.

Robust fuzzy tracking control of a quad-rotor unmanned aerial vehicle based on sector linearization and interval matrix approaches.

In this paper, the robust H∞ fuzzy tracking control strategy for a quad-rotor unmanned aerial vehicle (UAV) with strong coupling and highly nonlinear is put forward based on the Takagi-Sugeno(T-S) fuzzy error model. Firstly, the quad-rotor UAV system is divided into altitude subsystem, position subsystem and attitude subsystem. Through selecting appropriate premise variables, three T-S fuzzy error models, which are equivalent to the error dynamic model, are established by the sector linearization approach. Next, the uncertainties in drag coefficients, moments of inertia are taken into account, and the interval matrix is introduced to describe them in altitude, position and attitude T-S fuzzy error models. Then the robust H∞ fuzzy feedback controllers are designed to stabilize T-S fuzzy subsystems. Besides, according to the Lyapunov stability theorem, it is obtained that the LMI sufficient conditions of exponential stability with the prescribed H∞ performance for T-S fuzzy closed-loop subsystems. Meanwhile, the method for solving the gain matrices of controller is presented. Finally, simulation results are given to demonstrate the effectiveness, robustness and advantages of the proposed method. Then the feasibility of the proposed method is further verified by experimental results.

Observer based fault tolerant control for a class of Two-PMSMs systems.

In this paper, an observer-based state-feedback fault-tolerant controller is proposed for two coupling permanent magnet synchronous motors (PMSMs) system. The controller compensates the actuator faults and allows the system states to track the reference states corresponding to the output of the original two-PMSMs system. To design such a controller, the information of system actuator faults are required. Then, a robust adaptive observer is designed to estimate the system actuator faults firstly. Next, by setting the reference outputs the equilibrium control inputs and reference speeds are computed based on the mathematic model of the two-PMSMs system. Meanwhile, the variation dynamic model is derived. Additionally, the robust stability of the closed-looped system with fault-tolerant controller is analyzed via the Lyapunov theory and interval matrix. Sufficient stability conditions and the gain matrix of the fault-tolerant controller are obtained by solving the linear matrix inequalities (LMIs). Finally, simulation results are presented to illustrate the effectiveness of the proposed observer and fault tolerant control (FTC) scheme.

The design of delay-dependent wide-area DOFC with prescribed degree of stability α for damping inter-area low-frequency oscillations in power system.

In this paper, the delay-dependent wide-area dynamic output feedback controller (DOFC) with prescribed degree of stability is proposed for interconnected power system to damp inter-area low-frequency oscillations. Here, the prescribed degree of stability α is used to maintain all the poles on the left of s=-α in the s-plane. Firstly, residue approach is adopted to select input-output control signals and the schur balanced truncation model reduction method is utilized to obtain the reduced power system model. Secondly, based on Lyapunov stability theory and transformation operation in complex plane, the sufficient condition of asymptotic stability for closed-loop power system with prescribed degree of stability α is derived. Then, a novel method based on linear matrix inequalities (LMIs) is presented to obtain the parameters of DOFC and calculate delay margin of the closed-loop system considering the prescribed degree of stability α. Finally, case studies are carried out on the two-area four-machine system, which is controlled by classical wide-area power system stabilizer (WAPSS) in reported reference and our proposed DOFC respectively. The effectiveness and advantages of the proposed method are verified by the simulation results under different operating conditions.

Robust guaranteed cost tracking control of quadrotor UAV with uncertainties.

In this paper, a robust guaranteed cost controller (RGCC) is proposed for quadrotor UAV system with uncertainties to address set-point tracking problem. A sufficient condition of the existence for RGCC is derived by Lyapunov stability theorem. The designed RGCC not only guarantees the whole closed-loop system asymptotically stable but also makes the quadratic performance level built for the closed-loop system have an upper bound irrespective to all admissible parameter uncertainties. Then, an optimal robust guaranteed cost controller is developed to minimize the upper bound of performance level. Simulation results verify the presented control algorithms possess small overshoot and short setting time, with which the quadrotor has ability to perform set-point tracking task well.

Synchronization controller design of two coupling permanent magnet synchronous motors system with nonlinear constraints.

In this paper, two coupling permanent magnet synchronous motors system with nonlinear constraints is studied. First of all, the mathematical model of the system is established according to the engineering practices, in which the dynamic model of motor and the nonlinear coupling effect between two motors are considered. In order to keep the two motors synchronization, a synchronization controller based on load observer is designed via cross-coupling idea and interval matrix. Moreover, speed, position and current signals of two motor all are taken as self-feedback signal as well as cross-feedback signal in the proposed controller, which is conducive to improving the dynamical performance and the synchronization performance of the system. The proposed control strategy is verified by simulation via Matlab/Simulink program. The simulation results show that the proposed control method has a better control performance, especially synchronization performance, than that of the conventional PI controller.