Motion Control And Path Planning Research For Underactuated Autonomous Underwater Vehicle

Since underwater vehicles can undertake various tasks such as underwater scientific research,underwater salvage and lifesaving,submarine structures and pipelines maintenance,underwater anti-submarine and intelligence investigation,they have become an important research direction for many maritime powers in the world.Autonomous underwater vehicle(AUV)has become an important tool for underwater missions due to its advantages of wide range of motion,good maneuverability,small size,and light weight.In order to reduce weight,reduce manufacturing costs,reduce the incidence of mechanical failure,and reduce energy consumption,some of the AUVs are designed to be underactuated,with fewer control inputs to achieve control of their motion.The six-degree-of-freedom motion of underactuated AUV in underwater three-dimensional(3D)space is coupled and nonlinear,which makes it difficult to obtain its precise motion model and hydrodynamic coefficient,and its motion is subject to second-order non-integrity constraint,so the traditional linear control method cannot solve its motion control problem well.In addition,AUV is often disturbed by waves,currents and other environments during navigation,which makes the motion control of underactuated AUV very challenging.Almost all AUVs are powered by electricity.Because underactuated AUVs are generally small in size and carry limited energy,the underwater voyage time is relatively short.In order to extend the underwater operation time,it is very important to study the navigation mode for energy saving.According to the control requirements of underactuated AUV in actual work,this paper conducts the study on its motion control and path planning.Facing the problems of low efficiency and high cost in field test,in order to realize the simulation of underactuated AUV with six-degree-of-freedom,a detailed force analysis is carried out and a nonlinear dynamic simulation model is established.In order to add the environment disturbance and reduce the computational burden of simulation,the current and wave disturbance models are simplified appropriately.The motion simulation system is built,which lays a foundation for the design of AUV motion controller.In order to facilitate the design of the controller,the simulation model of underactuated AUV is simplified and its control model is established.When underactuated AUV tracks the straight-line path,the tracking quality near the waypoints is poor and the rudder angle is prone to saturation.In order to solve this problem,the constraint of angular velocity of underactuated AUV is considered and the expected angular velocity of AUV is optimized by designing a kinematic controller based on model predictive control(MPC).In order to overcome the uncertainty of dynamic model,a dynamic controller is designed based on adaptive sliding mode control(SMC)technology.The control system not only improves the straight-line tracking quality and the rudder angle saturation phenomenon of underactuated AUV,but also reduces the rudder steering energy consumption and realizes real-time obstacle avoidance.In order to improve the control quality of 3D curve path following,the constraint of angular velocity of underactuated AUV is considered,and MPC is applied to design a 3D curve path following kinematics controller so as to optimize the velocity of virtual target and expected angular velocity of AUV.Compared with the traditional control method,this control system not only reduces the adjustment time of tracking error,but also improves the overshoot of tracking error and the saturation of rudder angle.In order to improve the control quality of underactuated AUV in path following using traditional ILOS guidance law in ocean current environment,an improved ILOS guidance law and integrated vector field(IVF)guidance law are designed to effectively reduce the overshoot and adjustment time of tracking error.An adaptive dynamic sliding mode dynamic controller is designed based on the relative velocity,which can achieve a more stable control effect for the rotation speed of the propeller and effectively reduce energy consumption.Because the relative velocity between AUV and fluid is easier to measure than the absolute velocity of AUV in the current environment,this controller is more convenient for practical application.Aiming at the problem that the rudder angle is prone to high-frequency fluctuations due to wave interference when underactuated AUV is sailing near the surface,the gradient descent method(GD)and MPC are used to design regional tracking controllers,which realizes the regional tracking control of expected path under wave disturbance.Compared with the traditional control method,this control system makes the rudder angle more stable and the energy consumption less.Aiming at the 3D trajectory tracking control of underactuated AUV,the velocity constraint of underactuated AUV is considered and MPC is applied to design 3D trajectory tracking kinematics controller,therefore the expected longitudinal velocity and angular velocity of AUV are optimized.Compared with the traditional control method,this control system not only reduces the adjustment time of tracking error,but also improves the overshoot of tracking error and the saturation of rudder angle.Aiming at the problem of 3D stabilization control when the underactuated AUV lacks lateral and vertical driving forces and has no ability of backward(astern),a trajectory between AUV and the target position is planned and tracked to achieve the stabilization control of its position and attitude in the still water environment.Aiming at the problem of 3D stabilization control when the underactuated AUV works in the horizontal plane with constant current disturbance,a kinematic controller is designed by backstepping method,which realizes the position stabilization control of the AUV with its final attitude as countercurrent in the ocean current environment.Aiming at the problem of AUV has the constraint of minimum turning radius,in order to obtain the shortest smooth path that meets the constraint,the parameter calculation of four Dubins curves is simplified by coordinating transformation of the starting point position and attitude relative to the end point,the end point is uniformly transformed into the origin.By classifying the position and attitude of the starting point relative to the ending point in four quadrants,the selection of Dubins curve type is simplified.In 3D stabilization and path following,the method can plan the shortest smooth path from the starting point to the end point by arc and straight-line in real time.When there are currents or obstacles in the operating environment of the underactuated AUV,in order to obtain a smooth path with continuous curvature that meets the constraints of obstacle avoidance and minimum turning radius,a path planning method based on cubic spline interpolation and improved particle swarm optimization algorithm(IPSO)is proposed.The method can be used to find the path with the shortest distance that meets the requirements of obstacle avoidance and AUV minimum turning radius in the obstacle environment,and to find the path with the shortest sailing time that meets the requirements of AUV minimum turning radius in the ocean current environment,so as to improve the quality of path following and reduce energy consumption.