Research On Motion Control Strategy Of Unmanned Surface Vehicle Based On Trajectory Linearization

Unmanned surface vehicle(USV)is a miniaturized,multi-purpose and intelligent platform,which not only has the advantages of high speed,small volume and low cost,but also is an important tool for human to develop and protect the ocean.USV has been successfully applied in military and civil fields.Course control,path following and trajectory tracking control of USV are the core contents of USV motion control.Taking trajectory linearization control(TLC)theory as the basic idea,and combining the adaptive control,the radial basis function neural network control technology,observer control technology,finite-time stability theory,this dissertation studies the motion control strategy of USV.The main research works are as follows:(1)For the course control problem of USV subject to unknown time-varying disturbance,TLC method is used in the design of the course controller.Combining with the auxiliary dynamic system and neural network technology,an adaptive course control strategy based on TLC is proposed for USV,which improves the accuracy and stability of course keeping.Further,taking into account the dynamic characteristics of the thruster,a fast and slow loop control system is designed by TLC method,and a practical compound course control strategy is proposed,where a smooth switching function is incorporated into the auxiliary dynamic system to improve its performance,and a finite-time uncertain observer(FUO)is used to compensate the influence of disturbance.The proposed control strategy are not only simple in structure and easy to implement,but also have a strong inhibitory effect on environmental disturbances.(2)For the path following control problem of USV in the presence of unknown ocean currents,considering the unknown sideslip angle,combining fuzzy algorithm and predictor,an improved integral line-of-sight(ILOS)method is designed to realize the simultaneous estimations of sideslip angle and ocean current;Then,combining the minimum learning parameter method with less calculation and improved TLC method,a concise yaw rate controller and a surge speed controller based on TLC are designed to track the desired speed and guidance heading angle,and the controller has strong robustness and practicability.Further considering the cooperative path following problem of USV under input saturation,combining LOS guidance,cooperative control algorithm and TLC method,a cooperative path following control strategy based on TLC is proposed to realize the queue formation on a single curve.This strategy can not only overcome the influence of unknown ocean current and sideslip angle,but also deal with the problem caused by input saturation.(3)For the trajectory tracking control problem of USV with unknown model parameter uncertainties and time-varying disturbances,a trajectory tracking control strategy based on finite-time TLC is proposed by combining finite-time theory,adaptive sliding mode observer finite-time differentiator and TLC method,in which the finite-time differentiator and the adaptive sliding mode observer realize the differentiation of command signal and handle the unknown disturbances,respectively.Further considering the cooperative trajectory tracking control of USV under input saturation,a fast convergent cooperative trajectory control method based on finite-time TLC is proposed,in which a novel finite-time observer and a finite-time auxiliary dynamic system are designed to deal with the problems of compound disturbance and the input saturation,respectively,and all signals converge in finite-time.Finally,a number of USVs can reach the desired path in a finite-time and sail in a fixed formation.