Research On Thermocline Tracking Based On Multi-AUVs Formation

Ocean thermocline has very important meaning for ocean research,and the autonomous underwater vehicle(AUV)is the better choice to tracking the thermocline.Relative single AUV,ocean thermocline and tracking by using multi-AUVs formation,has incomparable advantages.About the multi-AUVs formation thermocline tracking problem,this paper studies the methods of thermocline tracking,AUV's motion control problems in the process of tracking thermocline,and more than two methods of multi-AUVs formation thermocline tracking is proposed.This paper studied the previous methods of AUV thermocline tracking,and improved the past thermocline tracking methods.By introducing a Kalman filter estimation algorithm,using the temperature data obtained from the previous estimate to get the temperature value of the next moment,thus could get the next temperature gradient value.And,when thermocline tracking,by comparing the three-probe point temperature gradient value,to determine whether the AUV in thermocline.The thermocline AUV motion control in the process of tracking,in order to overcome the unknown disturbance,in the process of thermocline tracking robust hinfinity control method,this paper mainly use the AUV motion based on state feedback controller is designed.Under the simulation environment,by joining process unknown disturbance and measurement noise uncertainty and random disturbance to test the robustness of the controller.Then,in this paper,based on the virtual leader and the combination of artificial potential field formation control method(VBAP)for effective control of the multi-AUVs formation.By simulation experiments,under the formation control method,multiple AUV formation to a curve for plane and three-dimensional space of a surface to achieve effective tracking.Finally,because the form of multi-AUVs formation will be according to the differences between the different tasks,such as the vertical distribution of AUV formation more tend to be more suitable for detection and the thermocline boundary;and transverse distribution of AUV formation tend to be more suitable for real-time tracking of thermocline.Based on the above two kinds of situations,the AUV formation forms are designed respectively.For vertical distribution of the multi-AUVs formation,each AUV in different depth.Each AUV has constant speed in level,in the vertical direction,AUV's vertical motion controller to control each AUV to achieve "yo-yo" movement.In the process of formation movement,each AUV use the thermocline tracking strategy determine whether in thermocline,in turn,it is concluded that the boundary of the thermocline.Finally,through the comprehensive detection result of each AUV,get the thermocline boundary position up and down.Through simulation experiments,the thermocline tracking method can better identify the thermocline boundary position up and down.For lateral distribution of the AUV formation,each AUV in the same depth,and interval distribution.In order to track the ocean thermocline,in this paper,the movement of multi-AUVs formation is decomposed to the horizontal plane and vertical plane.In the horizontal plane,using the VBAP formation control method for control of AUV's formation as a whole,in the vertical direction,through the thermocline tracking strategy update each AUV's speed in vertical direction.Through simulation experiments,the method can achieve good real-time tracking of thermocline.