Nonholonomic Multi-agent Systems Research Articles

Neurodynamics-based formation tracking control of leader-follower nonholonomic multiagent systems

This paper uses a bioinspired neurodynamic (BIN) approach to investigate the formation control problem of leader-follower nonholonomic multiagent systems. In scenarios where not all followers can receive the leader's state, a distributed adaptive estimator is presented to estimate the leader's state. The distributed formation controller, designed using the backstepping technique, utilizes the estimated leader states and neighboring formation tracking error. To address the issue of impractical velocity jumps, a BIN-based approach is integrated into the backstepping controller. Furthermore, considering the practical applications of nonholonomic multiagent systems, a backstepping controller with a saturation velocity constraint is proposed. Rigorous proofs are provided. Finally, the effectiveness of the presented formation control law is illustrated through numerical simulations.

Event-triggered prescribed-time consensus for nonholonomic multi-agent systems with external disturbances

This paper considers the prescribed-time event-triggered consensus for a class of nonholonomic multi-agent systems (MASs) with external disturbances. Firstly, the nonholonomic chained MASs are divided into two subsystems, and a switching control scheme is introduced. Secondly, a distributed prescribed-time continuous protocol is proposed to ensure that all agents reach average consensus within a prescribed finite-time. Moreover, to reduce the communication costs, an event-triggered consensus protocol is further established and some related theorems are given. In addition, the Zeno behaviour can be excluded by choosing parameters appropriately. Finally, two numerical examples are presented to demonstrate the effectiveness of the proposed protocols.

Adaptive Bearing-Only Formation Tracking Control for Nonholonomic Multiagent Systems

In this article, we consider the formation tracking problem of nonholonomic multiagent systems only using relative bearing measurements between the agents. Such a practical and important yet challenging issue has been taken into limited consideration by existing approaches, which usually requires additional measurements such as relative positions. The contributions of this article are two-fold. First, a fully distributed reference velocity estimator is proposed. Under the proposed adaptive estimator, each agent can estimate the time-varying reference velocity asymptotically. Second, an input-to-state stable controller is designed according to the bearing rigid theory. Under the proposed controller, the formation with bearing-only constraints can be achieved. Finally, the proposed scheme is demonstrated and its effectiveness is verified by presenting some simulation and experimental tests.

Distributed fixed-time leader-following consensus tracking control for nonholonomic multi-agent systems with dynamic uncertainties

The problem of distributed fixed-time leader-following consensus tracking control for nonholonomic chained-form dynamic systems with nonlinear disturbances is considered in this paper. Compared with the existing works, this paper considers a class of more general nonholonomic multi-agent systems where both the leader and the followers have nonlinear uncertainties. For undirected graphs, a distributed observer for each follower is investigated such that both the leader state and input can be estimated by the followers in a fixed time. Based on the distributed observers, a consensus tracking controller is proposed to ensure that the tracking errors convergence to zero within a fixed time. Lyapunov analysis proves the stability of the closed-loop system. A simulation example of wheeled mobile robots is given to demonstrate the effectiveness of the proposed controllers.

Finite-time consensus for nonholonomic multi-agent systems with disturbances via event-triggered integral sliding mode controller

This paper investigates the finite-time consensus problem for nonholonomic multi-agent systems with unknown external disturbances. Firstly, the chained-form nonholonomic multi-agent systems are converted into two subsystems, one is first-order and another second-order. Then, the integral sliding mode-based finite-time event-triggered control laws are proposed to ensure that the states of the agents achieve consensus in finite time in spite of external disturbances. Furthermore, the inter-execution time is proved lower-bounded and the Zeno behavior is therefore naturally avoided. Finally, numerical simulations demonstrate the effectiveness of the proposed protocols.

Formation control of non-holonomic multi-agent systems under relative measurements

This paper addresses a formation control problem for multi-agent systems with non-holonomic constraints under relative measurements. To overcome the issue of non-holonomic constraints, we design a feedback controller deriving rotational and translational motions according to formation error. A special form of formation error is employed here, which depends only on relative positions in a local frame. Hence, the designed controller is distributed and relative, meaning that only relative measurements of neighbors are used. Because a clique-based function is used, not an edge-based one, the best performance is yielded of all distributed, relative, gradient-based controllers. Moreover, we derive a necessary and sufficient condition of graphs under which a desired formation is achieved by such controllers. The proposed method is valid regardless of the dimension of the space, and thus it is applicable to not only unmanned ground vehicles (UGVs) but also unmanned aerial vehicles (UAVs). The effectiveness of the proposed method is demonstrated by simulations.

Bearing-based formation manoeuvre control of nonholonomic multi-agent systems

ABSTRACTThis paper concerns on the bearing-based leader–follower formation manoeuvre control problem for two- (2D) and three-dimensional (3D) multi-agent systems with nonholonomic constraint. The target formation is defined by relative-bearing measurements, which, for example, can be obtained from onboard cameras. The contributions of this paper are twofold. Firstly, a distributed formation manoeuvre control law is proposed for 2D nonholonomic agents according to the inter-bearing measurement. The multi-agent systems can achieve the desired formation which is defined by the bearings information. The formation manoeuvre can be achieved by steering at least two leaders. Secondly, the control law is nontrivially extended to 3D nonholonomic multi-agents systems. The leader–follower formation tracking problem can also be solved by the proposed proportional-integral control scheme. Simulation results for 2D and 3D nonholonomic multi-agents systems are presented. Experiments that used ground mobile robots verify the effectiveness of the proposed control laws.

Globally Stable Formation Control of Nonholonomic Multiagent Systems With Bearing-Only Measurement

In this article, the formation control problem of multiagent systems with nonholonomic constraints by bearing-only measurements is studied. Many previous works used the notation of infinitesimal rigidity to define the communication topology in formation control, but the global stability is difficult to achieve without leaders. To overcome this shortage, the maximal clique graph is used to define the topological relationship between agents. By minimizing the designed cost function, a novel distributed bearing-only formation controller is designed. Then, the close-loop system can achieve the global stability due to the existence of common agents between the maximal cliques under the designed controller. Besides, the global collision avoidance control strategy is also investigated with assistant distance measurement, which can prevent collisions between agents during the whole formation process. In addition, the embedded rotation angles between the final formation and the target formation are presented to optimize the motion process in real time. Finally, the simulation results verify the effectiveness of the designed controllers.

Tracking control of nonholonomic mobile agents with external disturbances and input delay

This paper investigates the tracking control problem of chained-form nonholonomic multiagent systems (MASs). In contrast to the existing works in which some algorithms have been designed for ideal conditions, the destructive factors including external disturbances and input delay are considered in the dynamics of the agents in this work. Two distributed controllers are proposed such that the states of the controlled agents can track the states of the target in the presence of external disturbances and input delay. For this purpose, a distributed controller is firstly suggested based on a switching method to solve the tracking control problem for nonholonomic MASs with external disturbances. Then, the proposed control law is extended based on a state predictor for the tracking control of agents in the presence of input delay. The stability analysis of the two distributed controllers is also provided. Simulation results show the promising performance of the proposed algorithms.

Distributed estimation and control of multiple nonholonomic mobile agents with external disturbances

This paper investigates the tracking control problem of nonholonomic multiagent systems with external disturbances. For this purpose, distributed finite time controllers (DFCs) based on the terminal sliding mode method are proposed to ensure that states of the agents track the states of the target in a finite time. Furthermore, a distributed estimator (DE) is designed for each agent to estimate the target's states. The stability analysis of DFCs and DE is also considered. Simulation examples demonstrate the promising performance of the proposed algorithms.

Distributed optimal integrated tracking control for separate kinematic and dynamic uncertain non‐holonomic mobile mechanical multi‐agent systems

This study addres,ses a distributed optimal integrated tracking control method with disturbance rejection for separate kinematic and dynamic uncertain non-holonomic mobile mechanical multi-agent ( N M 3 ) systems. Initially, based on the graph theory, the overall tracking systems of agents are defined and the distributed optimal tracking problem of separate kinematics and dynamics is transformed into an equivalent distributed optimal regulation problem of the integrated affine system. Then, neural network (NN)-based adaptive dynamic programming and cooperative differential game theory is utilised for control, in which only one NN is required for each agent. The NN weight-tuning law and the online algorithm is developed to approximate the value function, and synchronously update both optimal control and worst disturbance laws in only one iterative loop. The tracking errors and function approximation errors are proven to be uniformly ultimately bounded using Lyapunov theory. Finally, as applications of the proposed method, control of the wheeled mobile multi-robot system is discussed. The effectiveness of the method is demonstrated by the results of the comparative numerical simulation.

Avoiding the local-minimum problem in multi-agent systems with limited sensing and communication

In this paper, we consider a control problem for nonholonomic multi-agent systems in which agents and obstacles operate within a circular-shaped work area. We assume that agents only have limited sensing and communication ranges. We propose a novel control scheme using potential functions that drives agents from the initial to the goal configuration while avoiding collision with other agents, obstacles, and the boundary of the work area. The control scheme employs an avoidance strategy that ensures that the agents are never trapped at local minima that are typically encountered with most potential function-based approaches. A numerical simulation is presented to demonstrate the validity and effectiveness of the proposed control scheme.

LPV Formation Control of Non-Holonomic Multi-Agent Systems

This paper studies a formation control problem for nonlinear multi-agent systems; specifically non-holonomic vehicles represented as linear parameter-varying (LPV) models are of interest here. The objective of this study is twofold. First, we demonstrate the applicability of a novel approach to distributed control for LPV decomposable systems (Hoffmann et al., 2013). Second, we investigate different LPV representations of non-holonomic vehicles. We consider a group of agents in a leader-follower configuration which communicate through a directed time-varying but diagonalizable interconnection topology, where follower vehicles must achieve a desired formation and track the path determined by the leader agent. In addition, the leader vehicle is equipped with an LPV flatness-based controller to track a reference trajectory. The problem is formulated in terms of linear fractional transformations (LFT) for LPV systems with the objective of minimizing the closed-loop induced £2 gain. Simulation results with a formation of non-holonomic discs illustrate the proposed approach.

Novel potential-function-based control scheme for non-holonomic multi-agent systems to prevent the local minimum problem

In this paper, we consider a control problem of a non-holonomic multi-agent system. We assume that agents and obstacles are in a circular shaped work area. We propose a novel potential-function-based control scheme that drives agents from the initial to the goal configuration while avoiding collision with other agents, obstacles, and the boundary of the work area. The control scheme enables agents to avoid being trapped at local minima by forcing them to exit from the regions that may contain local minima. A numerical simulation is presented to demonstrate the validity of the proposed control scheme.

Connectivity Preservation in Nonholonomic Multi-Agent Systems: A Bounded Distributed Control Strategy

This technical note is concerned with the connectivity preservation of a group of unicycles using a novel distributed control scheme. The proposed local controllers are bounded, and are capable of maintaining the connectivity of those pairs of agents which are initially within the connectivity range. This means that if the network of agents is initially connected, it will remain connected at all times under this control law. Each local controller is designed in such a way that when an agent is about to lose connectivity with a neighbor, the lowest-order derivative of the agent's position that is neither zero nor perpendicular to the edge connecting the agent to the corresponding neighbor, makes an acute angle with this edge, which is shown to result in shrinking the edge. The proposed methodology is then used to develop bounded connectivity preserving control strategies for the consensus problem as one of the unprecedented contributions of this work. The theoretical results are validated by simulation.