Event-Triggered Formation Control For Multi-USV Via The Leader-Follower Structure

With the continuous progress of shipping technology,the control tasks of underactuated surface vehicles(USVs)tend to be complicated and diversified.That leads to a higher demand for the cooperation between each vehicles.For example,resource exploration,fleet escort and vehicle replenishment,they all need to coordinate and cooperate with multiple vehicles.That makes the formation control of multi-USV gradually become one of the hot research issues in the field of the ship motion control.Compared with a single underactuated vehicle,the collective operation of underactuated vehicles under the formation framework can improve the efficiency and safety of the maritime work,and it has a huge application potential in both civil and military fields.Therefore,it is of great significance to research the formation control of USVs.In this paper,the formation control of multi-USV is researched in the ocean environment via the leader-follower structure.The fleet control model of the leader-follower structure is established in the Cartesian coordinate frame.Meanwhile,based on the related model,a practical event-triggered robust neural control is developed by utilizing the event triggering mechanism.Furthermore,for merits of the Lyapunov theory,considerable efforts have been made to illustrate that all signals in the closed-loop system are the semi-global uniformly ultimately bounded.In addition,numerical simulations are conducted to demonstrate the validity of the proposed scheme.The outstanding contributions of this research can be summarized as follows:(1)For the leader-follower structure,in order to avoid the singularity in polar coordinates,the kinematics model of the formation control is constructed by using the Cartesian coordinate representation.Furthermore,through coordinate transformation,the corresponding control system is further optimized.The advantage of this design is that the control system is developed into a simple form,which contributes to settle the issue of the fleet states continuous acquisition intuitively.(2)In order to meet the requirements of the practical communication and time-varying formation,an event-triggered robust neural control algorithm is developed to perform the fleet control task.By employing the input event-triggered mechanism and robust neural damping technology,the related constraints generated by the neural networks can be effective avoid.When the event trigger threshold is met,state variables and control inputs can be reset or updated aperiodically.Hence,the triggering process can ultimately reduce the occupancy of the communication network between the controller and the actuator,and facilitate its application in practical engineering.(3)For the unknown items of the model,the actuator’s gain uncertainty and the disturbance of the marine environment in the multi-USV formation control,the radial basis function neural networks(RBF NNS),dynamic surface control(DSC)and adaptive backstepping technology are utilized to construct four adaptive parameters.They are contributed to compensate for the actuator’s gain uncertainty and the external disturbance by online updating of adaptive parameters.Finally,the control algorithm has the advantages of small computing load and simple structure of multi-ship formation control in practical engineering.