Path Following Control For Underactuated AUV In Complex Marine Enviroment

The path following control of Autonomous Underwater Vehicle(AUV)means that the underactuated AUV can be forced by the control law to track a desired reference path under the condition without time constraint.In this paper,the following research works are carried out on the motion control of underactuated AUV with the constraints of unknown time-varying environment disturbance,model parameter perturbation,dynamic uncertainty and input saturation.(1)For the bottom following problem of underactuated AUV with model uncertainty,unknown external environmental disturbances and input saturation,an adaptive neural network control method based on recursive sliding mode is proposed.Firstly,the vertical bottom following error model is established based on "virtual vehicle" method.Secondly,the approach angle path following guidance strategy is introduced to adjust the instantaneous behavior of the vehicle when approaching 'and converging the' expectational path movement process.Then,the nonlinear function is embedded into the virtual control law and the actual control law based on the recursive sliding mode control method,which can improve the contradiction between the control precision and dynamic quality of the system and improve the stability of system.Furthermore,the neural networks are introduced to approximate model uncertainty,and adaptive laws are designed to estimate the boundary between the neural network approximation errors and the sum of the external environmental disturbances.Finally,the auxiliary dynamic system is presented to compensate the effect of input saturation.The underactuated AUV effectively track the expected path with expected speed.(2)For the problem of spatial linear path following control of underactuated AUV with parameter perturbation,a non-singular fast terminal sliding mode control method with fixed-time convergence is designed.Firstly,the path following guidance law is established by"line of sight(LOS)" and the "virtual vehicle" method,which converts the position error stabilization control into the stabilization control of surge velocity error,pitch angular error and yaw angle error.Secondly,the surge velocity controller,steering controller and diving controller,which can realize path following with parameter perturbation,are designed by the integral sliding mode control(ISMC)method and fixed-time nonsingular fast terminal sliding mode control(NFTSMC).Finally,compared the proposed controller with adaptive sliding mode controller in the same simulation conditions,the simulation results show that the proposed control law can effectively realize the spatial linear path following of underactuated AUV with parameter perturbation,and has a shorter convergence time.(3)For the spatial curvilinear path following problem of underactuated AUV with multiple uncertainties and input saturation,a backstepping integral sliding mode control method based on reduced order ESO is proposed.Firstly,the kinematic error model of spatial path following is established based on "virtual vehicle" method.Secondly,the path following guidance law is established by using "line of sight(LOS)" method.The derivative of the virtual control signal is obtained by dynamic surface control technique,which avoid"explosion of complexity" caused by the direct analytical derivative of the virtual control quantity.Thirdly,the reduced-order ESOs are introduced to estimate and compensate all humped uncertainties due to the model parameters perturbations,unmodeled dynamics,environmental disturbances and nonlinear hydrodynamic damping terms.Furthermore,the auxiliary dynamic compensator is presented to analyze the effect of input saturation.Finally,compared the proposed controller with sliding mode controller and backstepping controller in the same simulation conditions,numerical simulation demonstrates the effectiveness and robustness of the designed controller.