Research On Control Algorithm Of Trajectory Tracking For Unmanned Surface Vehicle

The unmanned surface vehicle is a robotics boat, which may also be called ship. It canrespond to environmental changes, and complete the task in a minimum of humanintervention. USV can be widely used in intelligent surveillance reconnaissance missions, forthe measurement, research, search and rescue work is very helpful, can also be used forcommercial fishing. It is similar with some civil advanced system. The technology about USValso began in the aspects of the military application, because USV has these characteristics, ithas become research in many countries. This article mainly research work is to designnonlinear control law for USV trajectory tracking control problem.Firstly, the paper describes the unmanned surface vehicle in some specific place in the worldtoday, and made a brief introduction to the development of domestic and internationalunmanned surface vehicle technology. Also show that domestic unmanned surface vehicletechnology is still in the blank stage, and the urgent need to expand the relevant aspects of thetechnology exploration. Trajectory tracking control is the unmanned surface vehicle keytechnology. Based on some reasonable assumptions, a3-DOF maneuvering motionmathematic model of underactuated surface vessel has been established. Then we analyze thecontrol characters of underactuated surface ships by the mathematic model. In order toguarantee correctness during designing controller, the simulation of straight and turningmovement in the still water were accomplished.Sencondly, consider the three-degree-of-freedom mathematical model of USV. Reviewof the nonlinear control and nonholonomic system, in addition, introduced the sliding modecontrol method and designed trajectory tracking sliding mode controller. The advantage ofthese controllers is that they require very little amount of calculation, and can be used insmall-scale USV system. Sliding mode control can provide robust control law, however, thedisadvantage of these controllers is the adjustment of control parameters is very intuitive. Andunder the conditions of the different initialization, the optimization parameters which weredesigned in an initial condition are often underperforming.Thirdly, designing tracking controller. A new model predictive control method wereapplied to the trajectory tracking control. Model predictive control is to solve one of the openloop optimal control problem at each sampling time. As a result, under any constraints orinterference of the initial conditions, all can realize open loop optimal performance. However,its shortcoming is the controller needs a lot of computing time. This makes it morechallenging to use this method in small scale and rapid dynamic performance USV. Finally, considering the cascade characteristics of the trajectory tracking mathematicalmodel. In the design of trajectory tracking controller, introduced the cascade system theory.Combine with the advantages of the sliding mode control and model predictive control,designed a kind of Multi-rate cascade control structure. It use of model predictive controllerfor adjustment of sliding mode controller parameters, can effectively hold fast calculationperformance of Sliding mode tracking controller and optimization performance of modelpredictive controller combination. In order to further compare the control performance andcharacteristics, in the same simulation cases, do the simulation experiment for the threeunmanned ship trajectory tracking controller respectively. Through the analysis of simulationresults that this cascade structure considered optimal performance, and could provide not onlyreal-time computation but also meet the input saturation constraint control law.