Study On Motion Control Of Underactuated USV Based On Asymmetrical Model

As unmanned surface vessel(USV)shows broad application prospect and great commercial value in the naval,commercial and scientific sectors,it is attracting more and more concern and attention from researchers all over the world.Motion control system design is one of the core research contents of USV,while good motion control performance is the basic premise for the completion of USV's different tasks and missions.USV system is a typical underactuated system and second-order nonholonomic constraint system due to unequipped with side thrusters.Research on motion control technology of underactuated USV,would not only provide a technical reference for USV's motion control system design,but also promote the development of the underactuated system theory and nonholonomic constraint system theory.For USV model's underactuated and fore/aft asymmetrical characteristics,based on standard ship's six degree-of-freedom(DOF)motion model,the asymmetrical motion model of an underactuated USV is established.Considering damping coefficients changing greatly with USV's high speed,the asymmetrical motion model of an underactuated high speed USV is established.Replacing the random disturbance force model with current relative velocity model,an asymmetrical motion model of an underactuated high speed USV sailing in the presence of ocean current is also established.In the study of speed/heading control system,the design and implementation of the speed/heading control algorithms are mainly researched.Taking advantage of the pioneering S-plane motion control algorithm proposed by our research group in 2003,a novel adaptive expert S-plane motion control algorithm is presented for USV's speed and heading control.A large number of tank experiments and outdoor pool tests are done to demonstrate the reliability and surpriority of the control algorithm designed.In terms of underactuated USV's stabilization control problem,based on cascade systems theory,nonlinear backstepping approach and Lyapunov stability theory,a novel asymmetrical underactuated USV's stabilization control algorithm is proposed.A drift angle polar coordinate frame is designed as the body-fixed moving coordinate frame.By combining the drift angle,yaw angle and polar angle,another novel asymmetrical underactuated USV's block backstepping stabilization control algorithm is presented in the polar coordinate frame.By introducing the homogeneous theory and average system theory which are used for high-speed aircraft's control system design,into the high-speed USV's stabilization control problem,another novel asymmetrical underactuated high-speed USV's robust exponential stabilization control algorithm is designed.Replacing the random disturbance force model with current relative velocity model,another novel asymmetrical underactuated USV's stabilization controller is presented in the presence of ocean currents.Restriction condition of ocean current direction angle and desired yaw angle is firstly proposed in the paper.Detailed descriptions of distinct stabilization control performances in the presence of different ocean current velocities and direction angles are presented.Necessities of considering the USV model's fore/aft asymmetry and the ocean current disturbance in the stabilization control design are studied.In terms of underactuated USV's path following control problem,based on nonlinear backstepping approach,line of sight guidance algorithm and LaSalle invariance principle,a novel asymmetrical underactuated USV's path following control method is proposed,and importance of considering the USV model's fore/aft asymmetry in the path following control is analyzed.Taking into consideration high-speed USV's system damping coefficients is complicated coupled with USV's velocity,based on improved line of sight algorithm,another novel asymmetrical underactuated high-speed USV's path following controller is designed in the Serret-Frenet coordinate frame.The influence of damping coefficient changing with the high speed on USV's path following control performance is studied.Replacing the random disturbance force model with current relative velocity model,another novel asymmetrical underactuated USV's path following control algorithm is presented in the presence of ocean currents.Necessity of considering the ocean current disturbance in the USV's path following control design is studied.In terms of underactuated USV's trajectory tracking problem,considering the non-diagonal elements of damping coefficient matrix and inertia coefficient matrix are non-zero in asymmetrical USV's model,and the damping coefficients is complicated coupled with USV's high speed.By carrying out two global diffeomorphism transformations,the USV's trajectory tracking system is simplified,and then a novel asymmetrical underactuated high-speed USV's trajectory tracking control algorithm is proposed based on cascade systems theory and Lyapunov direct method.Arbitrary reference trajectory's tracking is achieved,including stabilization control of origin,and the well know angular velocity persistent exciting condition in the trajectory tracking control design is released.Replacing the random disturbance force model with current relative velocity model,another novel asymmetrical underactuated USV's trajectory tracking control method is presented in the presence of ocean current.Distinct trajectory tracking control performances in the presence of different ocean current velocities and direction angles are studied,and necessity of considering the ocean current disturbance in the USV's trajectory tracking control design is studied.In terms of asymmetrical underactuated USV's motion model,considering USV's high speed characteristics and the ocean current disturbances,problems of asymmetrical underactuated USV's stabilization control,path following control and trajectory tracking control are studied systematically and thoroughly.Achievements obtained in this paper could provide important technical reference for USV's motion control system design.