Speed Stability Analysis And Control Study Of Underwater Gliders

As a mobile platform for underwater exploration,the underwater glider has a broad prospect in the field of marine environment exploration,submarine reconnaissance and other fields with its advantages of low motion noise,long range and easy deployment.It is of great significance to the study of theories and applications related to underwater gliders to improve their performance.Complex ocean surveys and engineering tasks require a stable state of motion during operation of underwater gliders,but changes in ocean density,seawater pressure and other factors can affect the stability of the vehicle’s motion.Therefore,this paper investigates the effects of net buoyancy and glide angle changes on glide speed(vector)stability,looks for net buoyancy and glide angle intervals that make glide speed more stable,and achieves the goal of stabilizing the glide speed of underwater gliders by designing a feed-forward/feedback controller to compensate for external interference in real time.The main contents and results are as follows.In order to fully understand the dynamics of the underwater glider,this paper refines the force analysis of the conventional underwater glider dynamics model according to the specific case of "Petrel-II",and carries out the simulation experiment,which proves that the dynamics model can accurately describe the motion of the underwater glider.The factors affecting the net buoyancy during the working process of the underwater glider were analyzed and a net buoyancy variation model of the underwater glider was established.Analysis of the effects of net buoyancy and gliding angle changes on gliding speed stability showed that the gliding speed was relatively stable when the net buoyancy was greater than 4 N and the gliding angle was between 40° and60°.The buoyancy adjustment system model and the longitudinal inclination adjustment system model of the underwater glider are established;In view of the nonlinear and strong coupling characteristics of the underwater glider system,a feedforward/feedback control method based on the inverse model is proposed for the longitudinal dip surface motion control of the underwater glider.The simulation results show that the feed-forward/feedback control method based on the inverse model has good control performance and has certain robustness to external perturbations.The Petrel-II underwater glider was used to carry out a water test and simulation study and to preliminarily validate the theoretical research methods.The accuracy of the net buoyancy variation model as well as the steady-state motion model was verified,thus justifying the discussion of velocity stability for underwater gliders.