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This paper focuses on the stability analysis of the active disturbance rejection control (ADRC) for a class of uncertain systems. To overcome the difficulty of defining a reasonable Lyapunov function and setting limitations of system parameters, the converse Lyapunov theorem and the disturbance theory are employed. This paper proves that the estimation error of the extended state observer (ESO) and the tracking error of the closed-loop system using ADRC are uniformly ultimately bounded and monotonously diminishing with the increase of their respective bandwidth, so that the stability of the ADRC system could be performed. In order to further illustrate the relationship between the stability range and bandwidths, it analyzes quantitatively the performance of ESO and ADRC based on the root locus and the step response. Finally, an example based on a typical control system is carried out, and simulation results verify the theoretical analysis proved in this paper.

Purpose The aim of this paper is to propose a robust robot fuzzy logic proportional-derivative (PD) controller for trajectory tracking of autonomous nonholonomic differential drive wheeled mobile robot (WMR) of the type Quanser Qbot. Design/methodology/approach Fuzzy robot control approach is used for developing a robust fuzzy PD controller for trajectory tracking of a nonholonomic differential drive WMR. The linear/angular velocity of the differential drive mobile robot are formulated such that the tracking errors between the robot’s trajectory and the reference path converge asymptotically to zero. Here, a new controller zero-order Takagy–Sugeno trajectory tracking (ZTS-TT) controller is deduced for robot’s speed regulation based on the fuzzy PD controller. The WMR used for the experimental implementation is Quanser Qbot which has two differential drive wheels; therefore, the right/left wheel velocity of the differential wheels of the robot are worked out using inverse kinematics model. The controller is implemented using MATLAB Simulink with QUARC framework, downloaded and compiled into executable (.exe) on the robot based on the WIFI TCP/IP connection. Findings Compared to other fuzzy proportional-integral-derivative (PID) controllers, the proposed fuzzy PD controller was found to be robust, stable and consuming less resources on the robot. The comparative results of the proposed ZTS-TT controller and the conventional PD controller demonstrated clearly that the proposed ZTS-TT controller provides better tracking performances, flexibility, robustness and stability for the WMR. Practical implications The proposed fuzzy PD controller can be improved using hybrid techniques. The proposed approach can be developed for obstacle detection and collision avoidance in combination with trajectory tracking for use in environments with obstacles. Originality/value A robust fuzzy logic PD is developed and its performances are compared to the existing fuzzy PID controller. A ZTS-TT controller is deduced for trajectory tracking of an autonomous nonholonomic differential drive mobile robot (i.e. Quanser Qbot).

This paper investigates formation control of multiple nonholonomic differential drive wheeled mobile robots (WMRs). Assume the communication between the mobile robots is possible where the leader mobile robot can share its state values to the follower mobile robots using the leader-follower notion. Two approaches are discussed for controlling a formation of nonholonomic WMRs. The first approach is consensus tracking based on graph theory concept, where the linear and angular velocity input of each follower are formulated using first order consensus protocol, such that the heading angle and velocity of the followers are synchronized to the corresponding values of the leader mobile robot. The second is l-φ approach (distance angle) that is developed based on Lyapunov analysis, where the linear and angular velocity inputs of each follower mobile robot are adjusted such that the followers keep a desired separation distance and deviation angle with respect to the leader robot, and the overall system is asymptotically stable.The aim of this paper is to compare the performances of the presented methods for controlling a formation of wheeled mobile robots with matlab simulations.

This paper investigates the appointed-time consensus problem of multi-agent systems with Nomoto dynamics in vessel steering under directed and periodical switching topologies. The appointed-time means that the consensus arriving time can be off-line preassigned according to task requirements without conservative estimation and is independent of the initial conditions of agents states. From a motion-planning perspective and Pontryagin’ s principle, a novel distributed appointed-time algorithm is developed for a multi-agent system with Nomoto dynamics. Under the assumption that the union of the directed periodical switching topologies contains a directed spanning tree, the proposed distributed algorithms can guarantee the multi-agent system to achieve consensus at an appointed time. Finally, the effectiveness of the protocol is illustrated by numerical simulation.

This paper investigates the distributed attitude tracking problem of multiple spacecraft with unknown external disturbances and inertia uncertainties when the time varying reference signal is available to only a subset of group members. Modified Rodriguez parameters are used for attitude representation. The external disturbances and inertia uncertainties are recast into the lumped uncertainties with unknown firstorder derivative upper bound. An adaptive law is proposed to estimate this upper bound. Based on this adaptive law, a distributed adaptive full order sliding mode controller is proposed to achieve attitude synchronization. Simulation results are presented to demonstrate the validity of proposed results.

For conventional adaptive control, time-varying parametric uncertainty and unmodeled dynamics are ticklish problems, which will lead to undesirable performance or even instability and nonrobust behavior, respectively. In this study, a class of discrete-time switched systems with unmodeled dynamics is taken into consideration. Moreover, nonlinear systems are here supposed to be approximated with the class of switched systems considered in this paper, and thereby switching control design is investigated for both switched systems and nonlinear systems to assure stability and performance. For robustness against unmodeled dynamics and uncertainty, robust model reference adaptive control (RMRAC) law is developed as the basis of controller design for each individual subsystem in the switched systems or nonlinear systems. Meanwhile, two different switching laws are presented for switched systems and nonlinear systems, respectively. Thereby, the authors incorporate the corresponding switching law into the RMRAC law to construct two schemes of switching control respectively for the two kinds of controlled systems. Both closed-loop analyses and simulation examples are provided to illustrate the validity of the two proposed switching control schemes. Furthermore, as to the proposed scheme for nonlinear systems, its potential for practical application is demonstrated through simulations of longitudinal control for F-16 aircraft.

This paper proposes a leader-following consensus control for continuous-time single-integrator multi-agent systems with multiplicative measurement noises and time-delays under directed fixed topologies. Each agent in the team receives imprecise information states corrupted by noises from its neighbours and from the leader; these noises are depending on the agents’ relative states information. Moreover, the information states received are also delayed by constant or time-varying delays. An analysis framework based on graph theory and stochastic tools is followed to derive conditions under which the tracking consensus of a constant reference is achieved in mean square. The effectiveness of the proposed algorithms is proved through some simulation examples.

This paper discusses consensus tracking of single-integrator multi-agent systems with a time varying reference state based on the least squares estimation theory to deal with the case of communications disturbance. Since none of the followers can communicate with the leader within the accepted time due to communications disturbance, least squares estimation is applied for online estimation of the time varying reference state and reducing the tracking errors occurred due to communications disturbance. A theoretical proof is provided under some assumptions while the necessary and sufficient conditions are demonstrated for which consensus is reached on the time-varying reference state in case of communications disturbance. Finally, a Matlab example is given to validate the effectiveness of the proposed approach.

this paper investigates trajectory tracking for an autonomous nonholonomic wheeled mobile robot with virtual robot as reference trajectory. The standard proportional integral derivative (PID) is used for regulating the velocity of the follower robot such that the tracking errors are minimized between the follower and the reference trajectory. However using the PID controller solely for trajectory tracking produces poor results in the presence of noise or external disturbances. Hence genetic algorithms (GA) is applied in this paper to improve the performance of the PID controller in terms of control precision and speed of convergence. Moreover, communication between the follower and the virtual robot may fail very often in practice due to many raisons such as noise or external disturbances. Therefore, GA is applied again to predict the reference trajectory in case of communication disturbance. The simulation results demonstrate the effectiveness of the proposed GA-PID controller compared with the PID controller.

This technical note is concerned with the leader following consensus problem for networked Lipschitz nonlinear multi-agent systems subject to undirected communication topology. We propose an event triggered strategy with the state-dependent triggering function to solve the problem. A distinct feature of this strategy is that the communication does not occur continuously in both controller updates and triggering condition monitoring. Next, by using matrix theory and appropriate Lyapunov techniques it is proved that the leader following consensus can be reached without exhibiting Zeno behavior. Finally, the effectiveness of the proposed strategy is confirmed by numerical simulation example.

The finite-time consensus problem of multi-agent system with Nomoto dynamics is considered in this paper. Based on the unmeasurable velocity and input saturation, a novel finite-time protocol is proposed with a second-order sliding mode observer. With the aid of both homogeneous systems theory and finite-time Lyapunov stability theorem, this paper demonstrates multiple vessels can achieve consensus under the given protocol within finite time. Finally, the effectiveness of the protocol is illustrated by numerical simulations.

This paper investigates distributed formation tracking of multi robots with virtual robot as reference trajectory subject to communication failure. The objective is to propose a control approach which improves the performances of the formation in term of stability and robustness. Suppose fixed and directed communication topology, the control law is developed for each robot using extended consensus algorithm with a time varying reference trajectory. Meanwhile, polynomial regression method is implemented for estimating the trajectory of the virtual robot to overcome communication failure. At the end, Matlab simulations are carried out and the comparative results demonstrate the effectiveness of the proposed approach.

Information exchange between agents in multi-agents systems is often inexact and delayed. This paper proposes a distributed leader-following consensus algorithm for continuous-time single-integrator multi-agent systems under measurement noises and time-delays in directed topologies. The information states received by an agent from its neighbors are delayed by uniform time-delays. In the meantime, they are corrupted by additive white noises. Based on graph theory and stochastic tools, conditions to ensure the tracking consensus in mean square for both directed fixed and switching topologies are derived. The effectiveness of the proposed algorithms is proved through some simulations.

For a class of discrete-time multi-variable systems with time-varying parametric uncertainty, the parameter identification method and switching control architecture are developed in this study to implement smooth switching control. Specifically, the identification algorithm based on the least geometric mean squares is derived for the multi-variable system. In addition, the switching control system, with model reference control technique as the basis of control design for each local model, is proposed to achieve satisfactory control performance, especially to eliminate the oscillations at the switching boundaries which can be attributed to the difference in the input–output dynamics between the pre- and post-switching closed-loop subsystems. Furthermore, the switching strategy based on neural network classifier is put forward for the accurate switching among a set of model reference controllers which are correspondingly designed for the identified subsystems. Finally, the feasibility and effectiveness of the proposed identification and control schemes are verified by numerical simulations, which show that the desirable identification and control performances are guaranteed under the proposed schemes. Moreover, the advantage of the presented switching control system in terms of smooth switching is validated through comparison with other kinds of control schemes.

This paper presents a consensus algorithm for continuous-time double-integrator multi-agent systems with measurement/communication noises under directed fixed and switching topologies. The paper employs the algebraic graph theory and the stochastic tools to develop a consensus protocol in which a time-varying consensus gain is introduced to attenuate the additive white noises corrupting the information exchange between agents. Each agent׳s control input relies on its own information state and its neighbors׳ inaccurate information states and does not need the neighbors׳ information state derivatives. Conditions to guarantee mean square asymptotic convergence under noisy measurement for both fixed and switching topologies are derived. The consensus protocols developed in the noisy measurement case are proved to be still valid in the noise-free case, and they can ensure asymptotic mean square convergence. Finally, to illustrate the approach presented, some numerical simulations are carried out.

For a class of unstable discrete-time multi-variable switched systems with parametric uncertainty, an identification scheme is developed in this paper. Specifically, the identification algorithm is derived to identify the parameter vectors of potential subsystems based on the idea of least geometric mean squares. Furthermore, an neural network classifier is put forward for partition of the identified subsystems. Finally, feasibility and effectiveness of the proposed identification scheme are verified by numerical simulations, which show that the desirable identification performance is guaranteed with the proposed scheme.

In this paper, the leader following consensus problem of general linear multi-agent systems is investigated, where undirected communication topology is considered. To solve the tracking consensus problem, a distributed event-triggered strategy is designed with state dependent threshold. It is shown that the tracking consensus can be achieved asymptotically without continuous communication in both controller updates and triggering condition monitoring. The feasibility of this proposed event triggered control strategy is further investigated by excluding the Zeno behavior for each agent. Finally, a simulation example is given to validate the theoretical results.

In this paper, we consider the leader-follower consensus problem of multi-agent systems governed by second order dynamics with nonlinear terms. Taking into account the external disturbances, a leader-follower consensus tracking algorithm for each agent with high-order sliding mode control method is proposed to make all the followers track the leader. Then we prove that each agent can follow the leader under the proposed tracking strategy by using graph theory and Lyapunov approach. Finally, a simulation is given to illustrate the effectiveness of proposed theoretical results.

In this paper, we discuss the relationship between consensus on node voltage in electric networks and consensus on node value in graphs. According to the topology of a graph, we construct two kinds of networks: an RC network and an RLC network, corresponding to single-integrator dynamics and double-integrator dynamics respectively. Then we investigate three classic problems: leader following, consensus tracking, formation maintaining using RC networks and discuss consensus of networks with switching topology. An upper bound of convergence speed was given in view of energy, and we found that the energy decrease of average consensus is proportional to the variance of the initial voltages of capacitors. The energy analysis in electric networks is similar to the Lyapunov function. Simulations are provided at last to demonstrate the theoretical results.

The critical design for the control system of the ship-borne photoelectric tracking equipment is how to isolate the internal uncertainty and external disturbance. To obtain the stabilization and tracking of the target, servo control system of the photoelectric tracker becomes the key of the new designing measurement and control system. In this paper, the coordinate transformation technology is used to conduct the real-time compensation to the attitude angle caused by ship-swaying. And the multi-loop (double speed loop and a position loop) structure of servo system was modeled, and linear active disturbance rejection controller is designed to improve the anti-disturbance ability and control performance. The simulation results show that the proposed method is effective and it has better control effect and stronger anti-disturbance ability compared with traditional control method.

In this study, the consensus problem is discussed for a class of multi-agent systems with unknown Lipschitz nonlinear dynamics, external disturbances, and parameter uncertainties under a fixed directed graph. By some model transformations, the consensus problem becomes a reduced-order H∞ control problem. Based on the reduced-order control problem, sufficient conditions to achieve the consensus with the desired H∞ performance are presented. These conditions are to check the solvability of only one linear matrix inequality (LMI) and the dimension of the LMI independent of the number of agents in the network. Moreover, an algorithm is proposed to design the dynamic output feedback controller. Simulation on networked multi-agents is provided to show the effectiveness of the theoretical results.

This paper addresses the cooperative control problems of multiple quadrotor systems under fixed directed communication topologies. Dynamic surface control (DSC) is utilized to design nonlinear consensus controllers to make multiple quadrotors construct and keep a formation during flying. The control scheme is distributed so that each quadrotor updates the values of its information states based on the information states of its neighbors and its own states. Moreover, the leader–follower case is also discussed. In this case, distributed continuous schemes are also proposed with distributed sliding-mode observers, whose function is to estimate two linear combinations of the leader’s velocity and acceleration accurately in finite time. Finally, the effectiveness of the theoretical results is demonstrated via two examples.

The distributed leadless consensus problem for multiple quadrotor systems under fixed and switching topologies is investigated. The objective is to design protocols achieving consensus for networked quadrotors' positions and attitudes. Because the model of a quadrotor is a strong high-order nonlinear coupling system, the approach of feedback linearization is employed to transform the model into a group of four linear subsystems among which there is no coupling. Then, a consensus algorithm is proposed which consists of a local feedback controller and interactions from the finite neighbors under fixed undirected topologies. Especially, the problem of choosing the parameters in the consensus algorithm is also addressed, enlightened by the results of the robust control theory. Furthermore, it is proved that the proposed algorithm also guarantees the consensus under undirected switching topologies. Simulation results show the effectiveness of the proposed algorithm.

Two distributed consensus problems, including leadless consensus and tracking consensus, for multiple quadrotors with bounded disturbances under a directed topology are solved in this study. First, the model of a single quadrotor is divided into two subsystems. Some coupling terms between the two subsystems are regarded as external perturbations. For the case of leadless consensus, a distributed sliding-mode controller for the first subsystem and a state-feedback controller for the second subsystem are proposed to guarantee that the consensus is achieved with bounded errors that are only associated with disturbances. For the case of tracking consensus, by using the proposed sliding-mode consensus protocols combining with two sliding-mode observers, it is shown that all quadrotors can track the leader with bounded errors which can be manipulated suitably. Simulations show the effectiveness of the proposed control protocols.

This paper presents a novel dynamic hysteresis model for the piezoceramic actuators. The model is based on two new phenomena discovered in this paper, the geometric similarity and the time-scale similarity. In order to improve the accuracy of the model, the method of virtual extremum is proposed to amend the similarity. In the experiments, four kinds of input signals with different frequencies are used to test the proposed model. And the outputs predicted from the proposed model are compared with those obtained from the Preisach model. The results show that the proposed model gives good accuracy and performs better than the Preisach model. Especially, with the help of the time-scale similarity it is much easier to build a dynamic model.

Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a common axis. Due to the existence of the rotating mode, the desired relative position between every two agents is time-varying, and a Lyapunov-based approach is employed to solve the rotating formation control problem. Finally, simulation results are provided to illustrate the effectiveness of the theoretical results.

In order to reduce the number and difficulty of parameters being set, a method based on an improved particle swarm optimization (PSO) algorithm which can be used to tune ADRC parameters accurately is proposed. Meanwhile, to decrease the number of parameters, we optimize the state observer by designing several second or third-order state observers with the same parameters in series according to the system order. In order to verify the effectiveness and veracity of the proposed method, it is used to tune third-order ADRC, fourth-order ADRC, fifth-order ADRC and sixth-order ADRC. Simulation results show that the proposed PSO-based modified ADRC controller makes controller tuning easier and more effective and has strong robustness and adaptability for use in systems with many uncertain factors.

In this paper, transport control and synchronization are investigated between two periodically driven non-identical, inertial ratchets that are able to exhibit directed transport. One of the two ratchets is acting as a drive system, while the other one represents the response system. Based on the Lyapunov stability theorem, the essential conditions, under which the error nonlinear system is transformed into an equivalent passive system and globally asymptotically stabilized at equilibrium points, are established. With these results, synchronization, not only between two non-identical ratchets with known parameters but also between two different uncertain ratchets, are realized via adaptive passive controllers and parameter update algorithm. The direction of transporting particles can be dominated along expected one and it is useful to control the motion of tiny particles, ratchetlike devices in nanoscience.

This paper discusses robot formations in a distributed framework. The most important contribution is the incorporation of robustness into robot formation systems. When robots carry out tasks in a poor environment, the parameters in their models fluctuate around the nominal values, which may destroy the stability of the formation system. By modeling the group of robots as an interconnected system, we aim to develop a set of robust distributed controllers such that the overall system is robust to external disturbance as well as parameter uncertainty. Based on the graph rigidity theory, we also consider the rotation of a formation that plays an important role in real-time applications. Both simulations and real-time experiments are carried out to validate the effectiveness of the proposed framework.

This paper presents a comprehensive investigation on the $${{\mathcal H}_{\infty}}$$ control problem of linear multidimensional (nD) discrete systems described by the nD Roesser (local) state-space model. A Bounded Real Lemma consisting of a series of conditions is first established for general nD systems. The proposed nD conditions directly reduce to their 1D counterparts when n = 1, and besides several sufficient conditions which include the existing 2D results as special cases, some necessary and sufficient conditions are also shown to explore further insights to the considered problem. By applying a linear matrix inequality (LMI) condition of the nD Bounded Real Lemma, the nD $${{\mathcal H}_{\infty}}$$ control problem is then considered for three kinds of control laws, namely, static state feedback (SSF) control, dynamic output feedback (DOF) control and static output feedback (SOF) control, respectively. The nD $${{\mathcal H}_{\infty}}$$ SSF and DOF control problems are formulated in terms of an LMI and LMIs, respectively, and thus tractable by using any available LMI solvers. In contrast, the solution condition of the nD $${{\mathcal H}_{\infty}}$$ SOF controller is not strictly in terms of LMIs, therefore an iterative algorithm is proposed to solve this nonconvex problem. Finally, numerical examples are presented to demonstrate the application of these different kinds of nD $${{\mathcal H}_{\infty}}$$ control solutions to practical nD processes as well as the effectiveness of the proposed methods.

The purpose of this paper is to develop an analytic way for designing optimal PI-controllers for the interval plant family. Optimality means that the coefficient intervals of the plant stabilized by a PI-controller is maximized. It will be shown that the optimization problem can be formulated in terms of an eigenvalue minimization problem of matrix pairs of the form (H(h0, g0), H(δ1,κ, δ2,κ)), where κ = 1, 2, 3, 4 and both H(h0, g0) and H(δ1,κ, δ2,κ) are frequency independent Hurwitz-like matrices. A numerical example is provided to illustrate that optimal controller parameters can be successfully obtained by a two-dimensional search.

This paper presents a new constructive procedure for coprime realization of 2-D systems by means of the Fornasini-Marchesini second (FM-II) local state-space model. By exploiting the structural properties of an FM-II model realization, the proposed method can reduce the upper bound on the realization order for a large class of 2-D systems to about half of that obtained by the realization procedure given by the authors recently. It is also revealed that the new procedure is able to obtain minimal realizations for a much larger class of 2-D systems than the existing methods. Nontrivial examples are presented to illustrate the basic ideas and the effectiveness of the proposed method.

In this paper, formation tracking of multiple robots is studied. The communication between robots may fail due to the noise and external disturbances. In order to overcome the communication failure between followers and leader, particle swarm algorithm is applied to estimate online the trajectory of the leader. Finally simulations are curried out to verify the effectiveness of the proposed algorithm.

This paper addresses the cooperative consensus problem for nonlinear strict-feedback systems under directed graph topologies. For the case of multi-agent systems with unmatched nonlinear, we adapt a dynamic surface control which is a recursive and Lyapunov-based control design procedure yet avoid the problem of "explosion of terms". A new error surface based on graph theory is introduced to reduce the number of first-order filters which can simplify the recursive procedure. As an application of our algorithm, we study the problem of leaderless coordination of multiple quad rotors. The effectiveness of the theoretical result is demonstrated via simulations.

In the last decades Model predictive control (MPC) is the leading paradigm for high-performance and cost-effective control of complex systems. MPC contains powerful technique for optimizing the performance of constrained systems on state and control variables. For this reason, we use a distributed controller to coordinate a fleet of moving robots with unicycle kinematics. The proposed algorithm is based on the concept of robust MPC control with tube based strategy (i.e. It imposes low complexity and conservativeness). Using this approach we are able to guarantee that the real controlled system, on which a bounded disturbance is supposed to act, remains constrained in a neighborhood of the trajectory of the ideal system, which is defined by neglecting the effect of uncertainties. Obstacle avoidance function introduced for prevent collision between robot coordination. Mat lab implementation and real robot results are used to show the efficacy of the proposed control strategy.

The idea belong to presented work is to use a MPC (Model Predictive Control) controller combined with the feedback linearization in order to manage the control problem of a single robot with unicycle Kinematics and obstacle avoidance function. To guarantee the obstacle avoidance of wheeled mobile robot we use the widely popular concept of artificial potential field that perfectly integrates with MPC. This approach can be naturally used for defining a proper cost function in the MPC framework. The proposed algorithm is based on the concept of robust MPC control that guarantees the single robot to avoid collision in the presence of only fixed obstacles. The proposed control algorithm has been validated using a simulation environment. Some of the most relevant results are presented in the simulation section. In the end some possible future research directions are underlined.

This paper considers the robust stability analysis problem of multidimensional (nD) discrete systems. It is shown that the problems of stability test and stability margin computation for an nD system described by Roesser model can be recast into μ analysis problems in a unified way, thus can be solved effectively by using the commercially available software package. Several numerical examples are presented to illustrate the new methods.

This paper studies the tracking and obstacle avoidance control of a second-order multi-robot system. First, a Leader-Follower dynamic model is formulated and robots are divided into a leader and some followers according to the Lead-Follower method. Second, a sliding mode controller (SMC) is designed in the obstacles-free environment to track a predetermined trajectory. Third, a controller for obstacle avoidance is designed, which is combined together with the former SMC to formulate a global formation maintaining and obstacle avoidance control algorithm. Last, some simulation examples for tracking of a predetermined trajectory with or without obstacles are given. Simulation results demonstrate that the tracking and shape-maintaining algorithm turn out to be effective.

In this paper, we present a distributed leaderless consensus protocol for continuous time single-integrator multi-agent systems with multiplicative measurement noises in time-varying topologies. The consensus has been proved to achieve mean square convergence under restricted conditions on the network topology than those established in the literature for the same problem. That is in our study, the topology is required to have a spanning tree between any two consecutive switching times and no need to be balanced. The analysis followed here is based mainly on graph theory, stochastic tools, and some results about the stability of switching systems. At the end of the paper, some numerical simulations have been derived to demonstrate the effectiveness of our approach.

In this paper, the consensus and formation tracking control for multiple quad rotors are discussed. The dynamic model of the quad rotor is presented using the Newton-Euler formalism. Because the presence of the external disturbance in the quad rotor dynamic model, the design of the control law is Based on sliding mode control combined with fixed communication topology. With a good choice of parameters in the control law, the consensus and formation tracking are asymptotically achieved and the external disturbance is rejected. The system stability analysis is conducted through the Lyapunov theory and asymptotic tracking stability is demonstrated. The analytic results are supported by simulation tests.

In this paper, a class of nonlinear systems with parametric uncertainties in the control inputs are taken into consideration and several control design approaches are investigated and compared by simulation studies. As for nonlinearity, one popular method is gain-scheduling, of which the main idea is to linearize the system at many operation points and then adopt linear control design. However, it could not achieve good performance in the presence of uncertainties. Augmenting the gain-scheduling controller with adaptive control law may improve the closed-loop dynamics, but another disadvantage is the large quantities of data processing in advance resulting from linearization which would be impossibly addressed once we take the gain-scheduling as control strategy. Therefore, nonlinear control technique of less dependence on the mathematical model is our best choice. ADRC (active disturbance rejection control) benefits from its ESO (extended state observer) to cope with the disturbance and uncertainties. Moreover, the nonlinear feedback control based on ESO upgrades the performance of the closed-loop system. Simulations are conducted to validate the effectiveness of ADRC, and comparison is carried out to figure out advantages and disadvantages for each control law.

This paper considers the shape control of a group of mobile robots. The desired formation is only constrained by a shape with a flexible scale. An algorithm is proposed that optimizes the geometric performance during formation attainment. It is shown that the introduction of time varying scale function on the real time positions of robots improves the reliability of estimation in sensor-target localization. The algorithm is validated on the Pioneer wheeled robots platform where feedback linearization is introduced to overcome the nonlinearity of the robots kinematics.

This paper studies the distributed containment control problem for networked multiple quadrotors with multiple stationary leaders under a directed graph which is the communication topology between the leaders and the followers for arbitrary initial states. Necessary and sufficient conditions on the communication topology are shown. The model of a quadrotor is divided into two subsystems, one is under-actuated with the states of horizontal coordinates, the other is fully-actuated with the states of vertical position and the yaw angle. For the first subsystem, we present a new control law using backstepping technique such that all followers' states, horizontal coordinates, converge to the minimal hyperrectangle spanned by the corresponding states of the leaders asymptotically. For the second subsystem, due to the existence of uncertainties, a sidling-mode controller is given to compensate the uncertainty items. Furthermore, with the proposed controller, altitudes and the yaw angles of followers are driven to the minimal hyperrectangle formed by the leaders. Simulation results on networked multiple quadrotors are provided to show the effectiveness of the proposed protocols.

Automatic flight control system is the core on Unmanned Aerial Vehicles (UAV). The flight performance of UAV depends on the quality of designed flight control law to a great extent. Therefore, it is of great significance to study automatic flight control system. The paper discusses the application of Hierarchical Dynamic Inversion (HDI) in the design of a flight control system for fixed-wing UAV. Aiming at the DHC-2 'Beaver', flight simulation involving the Bookshaped trajectory tracking is carried out. Ultimately, the HDI system was compared with the PID system and the results showed that the former has better performance in terms of stability, operability, and accuracy.

This paper addresses the problem of robust control of spatially interconnected systems (SISs) subject to both exogenous disturbances and time-varying norm-bounded parameter uncertainties. A sufficient condition to the well-posedness, stability and attractiveness of an SIS with respect to all admissible uncertainties is presented in terms of a set of matrix inequalities. For the synthesis of distributed dynamic output feedback controllers, the nominal system is expanded in its output space so as to eliminate the uncertainties in the system matrices. In reference to the standard distributed scaled H ∞ control, the synthesis of distributed robust H ∞ controllers is proposed based on the system model in the expanded space. Numerical examples validate the effectiveness of the method.

In this paper, an efficient architecture is proposed to achieve finite time containment control of second-order perturbed directed networks with the introduction of distributed estimators. Two cases of dynamic leaders with constant velocity and variable velocity are analyzed based on finite time stability theory. In particular, we propose homogeneous and sequential estimators to guarantee accurate desired position and velocity estimation of followers in finite time. Then the accurate estimations obtained are employed to achieve robust finite time containment control. Distributed control protocols are developed by applying homogeneity theory and sliding mode control so as to make followers converge and remain within the dynamic convex hull spanned by the leaders in finite time and suppress perturbation effectively. Finally, several simulation results are presented as a proof of theoretical analysis.