Research On Attitude Control Technologies Of UUV

Unmanned Underwater Vehicle (UUV) is an indispensable tool which has widelyused in civil and military fields. In recent years, studies of UUV have attracted universalattentions and become hot topics of military technology and marine technology, thedesign of attitude controller which can response rapidly and robustly is one of the keytechnologies for UUV. The movements of UUV are presented by highly nonlinear andcomplex mathematical equations, the ballistic parameters of UUV would change underthe circumstance of deep submergence and high maneuver, various unknown forcesbrought by the complex ocean environment bring uncertain interferences to UUVmovement, so it is difficult for classic control methods to obtain precise control effects,the research object is a kind of light UUV like torpedo and the research purpose is todesign attitude controllers for UUV which can perform good control qualities, so aseries of research work was made in this paper.The main contributions are as follows:Firstly, a smooth mode-switch adaptive fuzzy PID controller is proposed to solveparadox between rapidity and overshoot when adopts conventional PID to UUV attitudecontrol. Simulation results demonstrate the excellent effects of the controller. Thiscontroller is composed of an improved PID controller in the bottom and an adaptivefuzzy PID controller in the upper and this controller adopts the idea of switch control tofully present the abilities of the various parts of the controller. Given the output ofconventional PID controller decreases with the error decreases, the proportionalcoefficient and the differential coefficient of the bottom PID are improved respectivelyto increase the rapidity of the system response; meanwhile the upper adaptive fuzzy PIDcontroller is designed to overcome the problem that bottom PID controller output maybe too large. When the bottom and upper controller switch, the process may buffet, asmooth switching function is proposed to reduce or eliminate the buffeting phenomenon.This function will perform different switching characteristics by adjusting thesmoothing factor. Considering the bottom and the upper controller, a complete and clearcontroller design method is formed.Secondly, for the highly nonlinear and complex characteristics of the UUV’s mathematical equations and the uncertainties of UUV model affected by parameterschange and external interferences, this paper proposes an adaptive backsteppingcontroller which does not need to know the upper bound of the unknown model andexternal interference. Simulation results illustrate the high performance of the proposedcontroller. Do zero dynamic analysis of the longitudinal motion and lateral movementaccording to the theory of nonlinear control, the equivalent equations of motion arederived, control law based on the basic backstepping control theory is given, considerthe shortcut of the basic law, this paper designs an adaptive backstepping controller tomake up for these deficiencies. the unknown model and external interference can beapproached by simple adaptive law which is easy to calculate and offsets the impactbrought by model inaccuracy.This paper gives two methods on how to design attitude controller for UUV,simulations demonstrate the excellent effects of the two controllers. Applications ofthese controllers are not limited to the UUV’s attitude, as it can be seen from the designprocess, the methods are general.