Study Of Spatial Target Tracking Nonlinear Control Of Underactuated Uuv Based On Backstepping

Regarding the human’s demands for the resources gradually increasing, countries aroundthe world have attached importance to the exploration and application of the marine resourcesin recent years. As the special equipment for resource exploration, environmental monitoring,ocean investigation, UUV is a mobile carrier which is small in size and convenient incontrollability, owning the ability for long-time navigating and great-weight carrying, whichcould satisfy the different demands of the fields of the military science and economic.However, UUV is the integration of high-tech. Besides, the operational environment iscomplex and unknown. Both the two factors ask for qualified safe-navigation and theimplementation of the mission tasks. Therefore, aiming to make the application of the UUVfeasible and credible, the theory should be applied in the dynamics characteristics and controlrequirements of the carrier, studying its dynamic model which would make sense forimproving the technical support of UUV and accelerating the process of engineeringapplications. In this respect, basing on the nonlinear backstepping control theory, the essaywill discuss the tracking control problem of UUV motion system, the purpose of which is toimprove the dynamic quality of UUV motion system.1. According to the distribution of the geometric shape and the implementing agenciesattached to UUV, space six degrees of freedom dynamic model is constructed after analyzingthe motion characteristics of the vehicle dynamic model. Not only does the dynamic modelcontain the hull hydrodynamic nonlinear and coupling, but also it takes the saturationcharacteristics of the implementing agencies and the equilibrium point features under thecurrent disturbance into account. Thus the accuracy of the digital simulation mode isimproved. Maneuverability simulation verifies the correctness of the underactuated UUVdynamic model.2. The way point tracking control problem of the underactuated UUV dynamic modeland the nonholonomic constraint features into account, the adaptive backstepping controller isdesigned, basing on the line of sight method. This method changes the tracking control of theunderactuated UUV into the steady control of the speed error, the heading angle error and thevertical inclination error, realizing the transformation from the stabilization control ofnonholonomic systems to the stabilization control of the holonomic systems. By this way wecan avoid the constraint of the necessary conditions of the Brockett theorem, which couldprovide the design method for the application of traditional control method in the underactuated UUV way point tracking control of three-dimensional path. 3. Taking the three-dimensional path following control problems of the underactuatedUUV dynamic model into account, we can apply the Lyapunov direct method andbackstepping design technique, which based on the five degrees of freedom nonlinear spatialpath tracking error equation. This method will finish the UUV path tracking controller designin the dynamics stage, securing the asymptotically stable of the closed-loop system. Myessay conclude that basing on the way the virtual guidanced approach planning proceeds, thetracking curve emerging from the continuous motion of the virtual UUV is smooth. Thus,when the straight-line path tracking proceeds, the inflection point can be easily tracked. Byintroducing the concept “approach angle”, we can adjust the instantaneous behavior of thevehicle when approaching and converging the expectational path movement process. Thesimulation results show that the designed controller can realize the accurate tracking ofthree-dimensional path, and then avoid saturation problem of the driving equipments.4. According to the problem of trajectory tracking control of underactuated UUV in3D,it faces the disadvantage of a tedious process of derivation to virtual control input signal, acontrol method based on filter backstepping is proposed. The method can significantlysimplify the process of design of backstepping controller through filter rather than analyticderivation directly to virtual control variable. Furthermore, the influence of measurementnoise can be decreased obviously because of derivative is got by integral but notdifferentiation. The stability of system of underactuated UUV has been proved based onLyapunov stability theory. Simulation results illustrate that the designed controller can trackthree-dimensional trajectory on place and time accurately.The study of nonlinear control method of UUV target tracking is deeply developed inthis paper. The results have important practical engineering value for the safe UUV andcomplete underwater mission credibly.