Global Output Regulation Research Articles

Global Cooperative Output Regulation of Linear Multiagent Systems With Limited Bandwidth

This article investigates the global cooperative output regulation problem of continuous-time linear multiagent systems (MASs), under the communication constraint of limited bandwidth. With a novel scaling function strategy, a distributed protocol based on the sampled and quantized data is designed to solve this problem. Compared with the existing works on quantized control of MASs, not only the boundedness assumption on initial conditions is removed, but also the communication graph is not restricted to be balanced or strongly connected. Moreover, the proposed quantized cooperative output regulation protocol does not rely on any global information of the communication graph. A simulation example is finally presented to illustrate the effectiveness of the proposed quantized cooperative output regulation protocol.

Global adaptive output regulation for nonlinear output feedback affine systems

In this paper, the global output regulation problem (ORP) for nonlinear output feedback affine systems with unknown functions (UFs) and unmeasured states is studied. Firstly, a Lemma is proposed to solve not only the global ORP of nonlinear systems, but also the ‘explosion of terms’ problem of backstepping. Secondly, the control scheme is designed based on backstepping method, which avoids an Assumption to solve the ORP. Therefore, the algorithm reduces the conservatism and increases the applicability. Finally, the algorithm is applied to Duffing system to verify the effectiveness of the algorithm.

Global adaptive output regulation for nonlinear systems with full-state constraints

ABSTRACT The paper investigates the global adaptive output regulation problem (ORP) for nonlinear systems with full-state constraints (FSCs). First, in order to avoid the disadvantages of barrier Lyapunov functions (BLFs) method and logarithmic constraint functions, radical constraint functions method is proposed to solve the FSCs problem of nonlinear systems. Second, a new internal model is designed based on the regulator equations. Third, the ORP of nonlinear systems is transformed into a stabilization problem. Then, according to the changing supply functions method and the Lyapunov analysis method, a non-backstepping control algorithm is proposed to ensure that all signals of the closed-loop system are globally asymptotically bounded, the tracking error is asymptotically stable, and all states of the system can be constrained. Finally, two simulation examples show the effectiveness of the control algorithm.

Adaptive output regulation of a class of nonlinear output feedback systems with unknown high frequency gain

This paper presents an output feedback design approach based on the adaptive control scheme developed for nonlinearly parameterized systems, to achieve global output regulation for a class of nonlinear systems in output feedback form. We solve the output regulation problem without the knowledge of the sign and the value of the high frequency gain a priori. It is not necessary to have both the limiting assumptions that the exogenous signal w and the unknown parameter μ belong to a prior known compact set and the high frequency gain has a determinate lower and upper bounds. The effectiveness of the proposed algorithm is shown with the help of an example.

Event-based cooperative global practical output regulation of multi-agent systems with nonlinear leader

This paper presents a distributed event-based high gain feedback design for the cooperative global practical output regulation problem of nonlinear multi-agent systems with unit relative degree subject to the general nonlinear leader system. We first convert global practical output regulation problem into global practical stabilization problem, then prove the input-to-state stability of the closed-loop system by regarding the sampling error and the steady-state of the actuator together as the external input. Based on the high gain feedback technique, the input-to-state gain function can be made sufficiently small, and hence the tracking error can converge to an arbitrary predefined small residual set around the origin. A distinguishing feature of our result is that, our controller is static and purely digital, thus, giving rise to quite a simple structure.

Global output regulation for a class of single input Port-controlled Hamiltonian disturbed systems

The problem of global output regulation for a class of single input Port-controlled Hamiltonian disturbed systems is studied. A composite control method is developed by combining the damping injection and the nonlinear disturbance observer techniques together. A series of coordinate transformation is presented to transform the system with mismatched disturbance into matched disturbance system. By means of Lyapunov stability theorems, global stability analysis for the closed-loop Hamiltonian system is presented. It is shown that the system output is regulated to zero asymptotically in the presence of mismatched disturbance without larger overshoots and longer settling time caused by integral action. Study on two examples with simulation results demonstrates the effectiveness of the proposed control method.

Output regulation of switched nonlinear systems using incremental passivity

This paper studies the global output regulation problem for a class of switched nonlinear systems using incremental passivity, even though the output regulation problem for none of subsystems is solvable. Firstly, a concept of incremental passivity for switched nonlinear systems without the requirement of the incremental passivity property of individual subsystem is introduced. This incremental passivity property is shown to be invariant under compatible feedback interconnection. Secondly, a switched nonlinear system is rendered to be incrementally passive by the design of a set of dynamic error feedback controllers and a dynamic switching law. In particular, an error-dependent switching law is designed to guarantee a specific class of switched systems incrementally passive. Thirdly, the incremental passivity for switched nonlinear systems is applicated to solve the global output regulation problem by the dual design of the composite switching law and error feedback controllers. The key idea is to design an incrementally passive switched internal model. Two examples including a Switched Chua’s Circuit are presented to illustrate the effectiveness of the proposed approach.

Cooperative global output regulation for a class of non‐linear multi‐agent systems with a non‐linear exosystem

This study considers the cooperative global output regulation problem for a class of non-linear multi-agent systems. In particular, the authors consider the case that the exosystem is of a non-linear form. With a distributed non-linear observer of the exosystem and the solvability assumption of the regulator equations, the authors convert the problem into a global cooperative stabilisation problem. Sufficient conditions are derived for the global cooperative stabilisation problem under fixed directed network topologies and switching undirected network topologies, respectively. Finally, the validity of the proposed approach is illustrated by simulation results.

Robust nonlinear control approach to nontrivial maneuvers and obstacle avoidance for quadrotor UAV under disturbances

Abstract In this paper, we present an onboard robust nonlinear control approach for quadrotor Unmanned Aerial Vehicles (UAVs) in the environments with disturbances and obstacles. The complete framework consists of an attitude controller based on the solution of global output regulation problems for SO( 3 ), a backstepping-like position controller, a 6 -dimensional wrench observer to estimate the unknown force and torque disturbances, and an online trajectory planner based on a model predictive control method with obstacle avoiding constraints. We prove the strong convergence properties of the proposed method both in theory and via real-robot experiments. The control approach is onboard implemented on a quadrotor UAV, and has been validated through intensive experiments and compared with other nonlinear control methods for waypoint navigation and large-tilted path following tasks in the presence of external disturbances, e.g. wind gusts. The presented approach has also been evaluated in the scenarios with randomly located obstacles.

Cooperative Output Regulation of Heterogeneous Nonlinear Multi-Agent Systems With Unknown Control Directions

This technical note considers global cooperative output regulation for a class of heterogeneous nonlinear multi-agent systems. By using the internal model principle and the adaptive control technique, a novel distributed adaptive control scheme is developed. Contrary to most existing results, the proposed controller is applicable to multi-agent systems with agents of non-identical relative degrees and non-identical unknown control directions under a general digraph. Moreover, any existing Nussbaum-type functions can be adopted in the proposed control scheme, and the adopted Nussbaum-type functions can be non-identical for each agent. It is shown that global cooperative output regulation of the controlled multi-agent system can be achieved under some mild assumptions. A numerical example is finally presented to illustrate the effectiveness of the proposed controller.

Global output regulation for a class of lower triangular nonlinear systems: A feedback domination approach

An alternative but new nonlinear output regulation approach is proposed for a class of lower triangular nonlinear systems by using the tool of adding a power integrator. The invariant manifold is solved and represented in terms of various derivatives of disturbances and references. As such, it is unnecessary to suppose that the external disturbances being governed by certain exosystems anymore. The nonlinearities are not restricted to be sufficiently smooth due the utilization of feedback domination approach. It is shown that the time taken to reach the desired invariant manifold from any initial states under external disturbances is guaranteed to be finite time. The control law is concise in structure for implementation since the feedback domination is implemented in each of the recursive design step.

Incremental passivity and output regulation for switched nonlinear systems

ABSTRACTThis paper studies incremental passivity and global output regulation for switched nonlinear systems, whose subsystems are not required to be incrementally passive. A concept of incremental passivity for switched systems is put forward. First, a switched system is rendered incrementally passive by the design of a state-dependent switching law. Second, the feedback incremental passification is achieved by the design of a state-dependent switching law and a set of state feedback controllers. Finally, we show that once the incremental passivity for switched nonlinear systems is assured, the output regulation problem is solved by the design of global nonlinear regulator controllers comprising two components: the steady-state control and the linear output feedback stabilising controllers, even though the problem for none of subsystems is solvable. Two examples are presented to illustrate the effectiveness of the proposed approach.

Cooperative Output Regulation for Uncertain Nonlinear Multi-Agent Systems with Unknown Control Directions

Abstract: This paper concerns the global cooperative output regulation problem for a class of nonlinear multi-agent systems with unknown control directions and unknown exosystem. The communication among agents makes it difficult to implement the Nussbaum gain technique to handle the non-identical unknown control directions. Moreover, the unknown parameter in the exosystem, which cannot be easily handled by the estimators in existing results, makes our problem more intricate. To overcome these challenges, we employ a novel internal model candidate to develop a two-layer control scheme for an adaptive distributed controller design. Theoretic stability analysis is presented and a numerical example is given to show the effectiveness of the proposed controller.

Cooperative Global Output Regulation of Second-Order Nonlinear Multi-Agent Systems With Unknown Control Direction

This technical note addresses the cooperative global output regulation problem for second-order nonlinear multi-agent systems without a priori knowledge of the control direction. We will propose both the graph-dependent and graph-independent distributed controllers based on the combination of the internal model, the Nussbaum-type dynamic gain, and the adaptive control technique. Comparing with some existing results, our novel design can handle the multi-agent system with not only the arbitrary and non-identical unknown control direction but also the uncertain parameter that belongs to any unknown and non-compact set.

Leader‐Following Output Synchronization for a Class of Uncertain Nonlinear Multi‐Agent Systems Under Uniformly Connected Network

AbstractIn this paper we study the cooperative global output regulation problem of a class of uncertain nonlinear multi‐agent systems under dynamic network topology. Distributed dynamic observers are introduced to estimate the states of the leader system or the called exosystem. Furthermore, we propose a multi‐channel input version of the changing supply rate theorem, through which the changing supply rate technique can be applied to the subsystem with multiple channels of the control inputs, and therefore control laws can be designed in a fully distributed way. As opposed to the existing results, in the current paper we allow the communication network topology to be uniformly connected. Finally, we apply our result to a group of well‐known Lorenz systems.

Global Optimal Output Regulation of Partially Linear Systems via Robust Adaptive Dynamic Programming

A non-model-based robust adaptive dynamic programming (RADP) approach is developed to solve the global optimal output regulation problem (GOORP) of partially linear systems with nonlinear dynamic uncertainties. By converting the output regulation problem into a global robust optimal stabilization problem, a robust optimal controller is designed by means of the RADP for the transformed system. Nonlinear small-gain theory is applied to conclude the global asymptotic stability for the closed-loop system and thus solves the original GOORP. Simulation results illustrate the effectiveness of the proposed methodology.

Cooperative Global Adaptive Output Regulation for Nonlinear Uncertain Multi‐Agent Systems with IISS Inverse Dynamics

AbstractThe cooperative global adaptive output regulation of nonlinear multi‐agent systems with unity relative degree was studied recently for the case where the inverse dynamics of the follower subsystems are input‐to‐state stable (ISS). In this paper, we present a further result by relaxing the ISS assumption to the integral ISS (iISS) assumption. As the iISS condition is strictly weaker than the ISS condition, our result applies to a larger class of nonlinear multi‐agent systems.

Global output regulation of a class of lower triangular nonlinear systems with unknown control direction via output feedback

In this paper, we study the global output regulation problem of a class of lower triangular systems under measurement output feedback. A novel high-gain filter is proposed to estimate the unmeasured states of the systems. Furthermore, we integrate the robust stabilisation technique and Nussbaumgain technique to achieve asymptotic regulation when the control direction is unknown. The simulation results illustrate the effectiveness of the proposed method.

Global output regulation for strict-feedback nonlinear systems with mismatched nonvanishing disturbances

Summary This paper concerns the problem of global output regulation for a class of strict-feedback nonlinear systems subject to mismatched nonvanishing disturbances. A composite control scheme is developed using a nonlinear disturbance observer-based control approach. A novel idea is that the disturbance estimation is introduced into the design of virtual control laws in each step. Global stability analysis for the closed-loop system is presented by the direct Lyapunov function method. It is shown that the system output asymptotically converges to zero in the presence of mismatched nonvanishing disturbances without the requirement of solving any partial differential equations involved with the traditional output regulation theory. An application design example of a single-machine infinite-bus system with static var compensator is presented with simulation results to demonstrate the effectiveness of the proposed method. Copyright © 2014 John Wiley & Sons, Ltd.

Cooperative Global Output Regulation for a Class of Nonlinear Multi-Agent Systems

In this technical note, we consider the cooperative global robust output regulation problem for nonlinear multi-agent systems in output feedback form by distributed output feedback control. The main result can be summarized as follows: if the information of the leader can reach every follower through a path and the communication flows among the followers are bidirectional, then the problem can be solved by a distributed output feedback control law if the global robust output regulation problem for each subsystem can be solved by an output feedback control law.