Heterogeneous cooperative trajectory tracking control between surface and underwater unmanned vehicles

This paper introduces a decentralized control strategy for a heterogeneous team consisting of an unmanned surface vessel serving as the leader vehicle and two unmanned underwater vessels acting as follower vehicles. The team is designed to work together to accomplish underwater exploration missions. The communication network of the team is a fixed, directed topology and only the follower unmanned underwater vessels can read the states of the leader unmanned surface vessel. The proposed system consists of a guidance loop and a control loop. In the guidance loop, a novel cooperative guidance method between a surface and two underwater unmanned vessels is introduced by constructing a path deviation based on vertical line constructs. In the control loop, an iterative sliding mode controller is designed to mitigate chattering issues caused by switching system structures. Meanwhile, an optimization function is employed to optimize control inputs, addressing control input constraints, and reducing control input chattering. The external disturbances and unmodeled dynamics are estimated using a linear extended state observer, and the results are used for the controller design. Finally, simulation tests are carried out to validate the effectiveness of the proposed control system.