This paper is concerned with the coordinated formation control problem of multiple autonomous underwater vehicles (AUVs) under alterable communication topology and time-varying delay in discrete time domain. Firstly, the multi-AUV system is divided into one leader and multiple followers, and the communication topology is divided into two parts. The coupled nonlinear AUV model is linearized into a second-order integral model using state feedback. Secondly, two types of coordinated controllers in discrete time are proposed: the controller for multi-AUV system without delay, the controller for multi-AUV system with time-varying delay. Then, the formation control issue for multiple AUVs with alterable topology is treated as the asymptotic stability of an error system. The stability analysis of the error system consisting of the state errors between each follower and the leader is performed, to obtain some novel sufficient conditions for achieving the formation control objective. Finally, some simulation results are presented to demonstrate the effectiveness of the theoretical results, and the comparisons describe the effects of communication topology and delay on the performance of the control system.
This article considers the issue of event-based coordinated formation control for multiple autonomous underwater vehicles subject to time-varying communication delay and alterable topology under discretized time. First, to derive the dynamics model in the discrete-time domain, the state feedback technique and the forward difference approach are employed for the continuous-time nonlinear model of autonomous underwater vehicle. For each follower, the event-triggering function and the coordinated controller are designed, using only discrete-time state information of the leader or other followers. Under this control strategy, the controller will not be updated at each discrete-time instant. Then, the coordinated control problem is turned into the asymptotic stability problem of the multi-autonomous underwater vehicle system. According to the stability analysis, sufficient conditions are presented for successfully completing the formation assignment without and with time-varying delay, respectively. Finally, by performing some numerical simulation experiments, the efficacity of our proposed event-based controller and the correctness of the main theoretical results are demonstrated. The impact of different communication conditions on the control system is revealed by the comparison of several scenarios.
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