Research On The Control Design Approach For A CMGs-actuated Underwater Vehicle Saturated Tracking

With the development of marine exploration,marine equipment is tending to become more detailed division,higher degree of specialization and diversification.As a special kind of the hybrid-actuated autonomous underwater vehicle(AUV),the AUV with internal control moment gyros(CMGs)possesses three-axis attitude control ability,and can maneuver its attitude when the vehicle is moving at a low speed or even in a stationary condition.Meanwhile,this vehicle doesn't rely on relative fluid motion to maneuver its attitude and preserve the hydrodynamic integrity of its hull,which is suitable to fulfill the task in a narrow space.Yet,since CMGs have been introduced in the AUV,most of its researches are concentrated on the dynamic modeling and simple attitude stabilization control without involving the challenging problem of this type of vehicle,namely the tracking control problem.Specially,from a practical perspective,it's necessary to start the research of the position and attitude tracking control for this kind of AUV subject to the lumped nonlinearities,including the input saturation,parameter uncertainty,coupling dynamics and time-vary ocean currents.This dissertation firstly investigated the state of art of motion control on hybrid-actuated AUVs,especially for the CMGs-based AUV motion control with the existing problems analysed.Then,it has been reviewed that state of art of the position and attitude tracking control of traditional AUVs,and trajectory control with input saturation constraint;attitude and position tracking control of the CMGs-based AUV are selected as the core research content of this thesis,where the main research work is summarized as follows:Firstly,mathematical model of the CMG system is introduced,mechanism of its singular configuration is elaborated in detail and several classical steering logics for the system are timely recommended.Kinematic equations of the AUV are presented on the basis of Euler angles and quaternions,respectively;kinetic equations of the AUV coupled with the dynamical behavior of CMGs are shown with its particularity,compared with the traditional AUVs.Then,the input saturation characteristic of this kind of AUV is analysed.Secondly,based on the integrated attitude kinematics and dynamics of the AUV with CMGs,the AUV with distributed CMGs can realize large-angle and fault-tolerant attitude control in a stationary condition by virtue of the adaptive fault-tolerant control approach;the problem of redesigning a CMG steering law is avoided.On this basis,an adaptive non-singular terminal sliding mode control(SMC)approach is proposed,which can accomplish the finite-time attitude control of the CMGs-based AUV subject to double constraints of actuator faults and input saturation;numerical simulations are performed in different cases to validate the performance of the proposed controller.In addition,considering the general situation with hydrodynamic parameter uncertainty,external ocean current,actuator fault and input saturation,finite-time attitude stabilization control of the underwater vehicle is realized based on the adaptive method and SMC strategy.Thirdly,considering the attitude tracking control problem of a CMGs-actuated AUV with a constant propulsion in the presence of input saturation constraint,modeling parameter uncertainty and external environmental disturbance,two finite-time tracking controllers are formulated.Scenario one is based on the finite-time convergent extended state observer(FTCESO)and backstepping SMC approach,which utilizes a switch function to realize the switching between the robust control law and constant reaching law;the anti-windup compensator is designed to relieve the burden of the observer.Moreover,non-singular terminal sliding mode in conjunction with the radial basis function neural network(RBFNN)control method is introduced to improve the scenario one,and the designed scenario two releaves the bounds of the differentiable hypothesis of disturbances.Meanwhile,numerical simulations are conducted in different cases,which can support the superiority of scenario two whether in the convergent time and steady-state error,compared with the scenario one.Fourthly,to address the planar trajectory tracking problem of the CMGs-based AUV,the CMG output torque is decoupled from the AUV dynamics based on a global homeomorphism transformation.The shunting neural dynamic model and backstepping method are proposed to formulate the controller,which solves the tracking problem in the idea scenario without ocean currents.Then,considering the effects of modeling parameter uncertainty and environmental disturbance,an adaptive dynamical SMC method is proposed to design the controller,which guarantees that the tracking errors are uniformly ultimately bounded(UUB);and parameterized trajectories of a straight line and a sinusoidal line are conducted to validate the designed controller.Further,utilizing the backstepping method and improved adaptive dynamical SMC approach,which realizes the asymptotic convergence of the tracking errors.Thus,the reduced virtual control variables have optimized the design of above control strategy,and improved the system control performance.Finally,the author studies three-dimensional(3D)trajectory tracking problem of the CMGs-based AUV.Based on the velocity control scheme derived from the error kinematics of the position,backstepping method and anti-windup compensator are applied to design the controller,which guarantees that the tracking errors are UUB with input saturation.Also,based on the designed velocity controller,the dynamic control law is developed on the backstepping method and RBFNN control approach,which solves 3D trajectory tracking control problem of the traditional AUV with the existence of input saturation,modeling parameter uncertainty and external disturbances.Besides,with the aid of a physical translation of the motion equations,control inputs of the AUV system in combination with the actuator's dynamics are decoupled.Then,with the aid of the above control shcme added with a roll dynamic controller,position and attitude tracking errors are made UUB in the presence of input saturation,partial parameter uncertainty and external disturbance;besides,effectiveness of the control strategy is validated by the numerical simulations in different cases.