Abstract
Cooperative tracking control problem of multiple water–land amphibious robots is discussed in this article with consideration of unknown nonlinear dynamics. Firstly, the amphibious robot dynamic model is formulated as an uncoupled nonlinear one in horizontal plane through eliminating relatively small sway velocity of the platform. Then cooperative tracking control algorithm is proposed with a two-stage strategy including dynamic control stage and kinematic control stage. In dynamic control stage, adaptive consensus control algorithm is obtained with estimating nonlinear properties of amphibious robots and velocities of the leader by neural network with unreliable communication links which is always the case in underwater applications. After that, kinematic cooperative controller is presented to guarantee formation stability of multiple water–land amphibious robots system in kinematic control stage. As a result, with the implementation of graph theory and Lyapunov theory, the stability of the formation tracking of multiple water–land amphibious robots system is proved with consideration of jointly connected communication graph. At last, simulations are carried out to prove the effectiveness of the proposed approaches.
Highlights
We propose a two-stage control strategy to further decouple the system by dividing the whole process into two sub-processes concerning about dynamics and kinematics individually
Even though change of dynamics introduce disturbances of estimations, but results converge to true values asymptotically
Simulations have been carried out to verify all algorithms obtained in this article, results have shown that with dynamic stage control and kinematic stage control, formation tracking of multi-ARs system with nonlinear dynamics and unreliable communication links can be reached with complex trajectories of the leader
Summary
Multi-agent system (MAS) control has attracted attentions from various fields in recent years for its broad application aspects.[1,2] Especially for multi-robots system, massive studies have been carried out for consensus, formation, flocking, and rendezvous problems.[3,4,5,6] Multiple underwater vehicles are widely discussed for its potential applications in marine environment such as seafloor mapping, target searching, and ocean monitoring.[7,8] In addition, water–land amphibious robots have attracted much more attention recently as a special form of underwater vehicles with abilities such as autonomous charging and data uploading.[9,10,11] Among all problems in cooperative control of MAS in previous studies, the dynamics of agents and communication graph are mostly discussed.At the beginning, studies about cooperative control of MAS mainly concentrate on agents with integral high orders.[12]. Keywords Formation tracking, jointly connected, multi-agent, nonlinear dynamics Through proving the stability of the multi-ARs system with time-varying surge velocity and yaw angular rate of the leader, consensus of velocities and angular rates among amphibious robots is guaranteed in dynamic stage.
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