Path Tracking Control Based On Line-of-Sight Law For An Underwater Snake Robot And Optimization Method

As autonomous underwater vehicles are applied more in marine environmental exploration tasks,underwater snake robots,a class of bionic robots,have received more research attention.Underwater snake robots have a narrow form and a flexible motion posture,and are therefore better suited for situations such as underwater pipeline inspection and confined space search,which will have more applications in ocean engineering in the future.Compared to a ground snake robot,underwater snake robot works in variable fluid environments,which poses challenges for accurate modeling and designing stable control methods.This dissertation focuses on the path tracking controllers,which enhances robot robustness,and the strategy to improved energy efficiency.The main research content is as follows:1.Research on the establishment of mathematical models for underwater snake robot.The underwater snake robot has a modular structure,and the dynamics model is derived through the moment balance equation after analyzing the hydrodynamic forces of robot links.A strategy that converts the rotational motion of links into translational motion is adopted to derive a control-oriented simple model,as the robot characteristics are given.2.Research on the curve path tracking control method based on improved line-of-sight(ILOS)rules.In order to generate a smooth curve path with derivative information,PCSI(parametric cubic spline interpolation)method is employed to complete the path planning for robot.Subsequently,path information is combined with ILOS to calculate the reference heading,In addition,a point matching strategy based on the Newton-Raphson method is proposed to improve the tracking accuracy.Simulation with multiple paths and robot parameters validate the effectiveness of the proposed control method.3.Research on the locomotion efficiency optimization based on improved pigeon-inspired algorithm.Firstly,according to the analysis of the robot gait parameters based on averaging theory,it is verified by simulation that there is a correspondence between gait parameters and robot speed.Then,a rule to evaluate the energy efficiency is proposed,along with a method that selects the gait parameters dynamically with improved pigeon-inspired algorithm(QPIO)to improved efficiency value.Finally,the improved robot system is implemented on a previous curve path simulation and the comparison illustrates that this strategy performance well.4.Research on heading optimization method based on backstepping control.In order to make the underwater snake robot track the large curvature path more accurately,the backstepping control methodology is adopted to design the controller.In particular,the heading error is calculated with a sliding function and the calculation method of reference joint angle is chosen so that the system satisfies the Lyapunov condition.Simulations under more complex paths demonstrate that the controller can reduce the tracking error,compared to previous methods.