Research On Tracking Control Algorithm Of Underwater Vehicle Based On Velocity Observer

Autonomous Underwater Vehicle(AUV)is one of the important tools for human to understand and develop the ocean,and target tracking is one of the key technologies for the application of AUV.It can realize the task of the underwater vehicle in the complex Marine environment.Reliable target tracking strategy is not only related to the success of the task of the underwater vehicle,but also affects its safety.Considering the complex and changeable underwater environment,there are uncertain factors such as fluid resistance and load variation in the process of underwater vehicle movement,which make it inevitable to deal with the uncertain parameters and external disturbances of the vehicle model.In addition,in the actual Marine environment,due to the influence of tide and ocean current,the measured speed signal is easily disturbed by environmental noise,which reduces the quality of the speed signal.Moreover,the installation cost of the speed sensor and other practical reasons further lead to the difficulty of the speed measurement of the AUV.Aiming at the above problems,this paper studies the tracking control strategy of the underwater vehicle based on the velocity observer.The main research work is as follows:(1)The model is built for the highly complex AUV nonlinear system.Then,the position information of the AUV was obtained by using the buoy-assisted positioning estimation method,and a finite time velocity observer was designed.The Linear Matrix Inequation(LMI)optimization tool was used to obtain the corresponding performance conditions,and the accurate velocity information of the AUV was obtained in the finite time.The results were verified by simulation.(2)Considering the uncertain parameters and external disturbances in the AUV model,a fast terminal sliding mode velocity observer is obtained by improving the original velocity observer.Based on the observed velocity information,an adaptive non-singular fast terminal sliding mode tracking controller is designed.The lumped uncertainty of the model is dealt with by the adaptive method,and the AUV can reach the target point in finite time.For the proposed control strategy,the influence of the observer is fully considered,and the corresponding Lyapunov function is designed to analyze the stability of the proposed control strategy,and the sufficient conditions for finite time stability are given.(3)Aiming at the cooperative tracking control problem of multi-AUV formation,a distributed formation controller was designed to realize the control of AUV formation under the condition that the speed information was unmeasured and the saturation constraints were fully considered.Then,a new convex hull expression is proposed,based on which a stability criterion based on observed velocity lag is established to ensure the tracking control performance of multi-AUV formation.At the same time,the attraction domain optimization problem is studied for multi-AUV system,and the attraction domain optimization method under velocity observer and actuator saturation is obtained.