Multi-thruster AUV Maneuverability Analysis And Thrust Allocation Research

Since entering the 21st century,with the in-depth development and utilization of ocean resources and the far-reaching layout of Marine homeland security,intelligent marine engineering equipment has developed rapidly.AUV is a kind of intelligent marine equipment that integrates multi-disciplinary technologies such as communication and navigation,image recognition,information fusion,automatic control,etc.It is more and more widely used,and plays an important role in safeguarding national security and safeguarding national sovereignty.Its research and development level are often a reflection of a country’s technical strength of marine equipment.In order to meet the needs of increasingly complex and diverse underwater tasks,the design of AUVs has been proposed with higher intelligence,maneuverability,and stronger robustness requirements.The analysis of AUV’s maneuverability and the research on thrust allocation method provide theoretical basis and technical support for AUV to realize high-precision motion control,high-mobility underwater task operation and multi-mode switching.In this paper,the maneuverability analysis,thrust allocation method and switching strategy of AUV equipped with multiple thrusters are carried out.The main research work includes:(1)Aiming at the problem that multi-thruster AUV must ensure the operation safety operation under different working modes and various thruster arrangement conditions,the evaluation of the maximum maneuverability performance was put forward with the limit speed that AUV can reach at a certain heading angle.Using the advantage of the augmented Lagrange multiplier method to solve multi-constraint optimization problems,a maneuverability analysis algorithm was designed.Finally,the maneuverability of AUV under different thruster layout conditions was simulated and analyzed.It has guiding significance for AUV underwater safe operation and multithruster layout optimization.(2)Aiming at the problem of high accuracy and high real-time thrust allocation in complex mathematical model of multi-thruster AUV.Firstly,a thrust allocation method based on Quadratic Programming(QP)was designed,and then a thrust allocation method based on Extreme Learning Machine(ELM)was proposed.Then,the established ELM network was trained by using the thrust optimization allocation data set generated by QP method,and the trained parameters were brought into the ELM thrust allocator.Finally,the correctness and effectiveness of the two methods were verified by simulation experiments and model experiments.In addition,compared with the traditional iterative QP thrust allocation method,the proposed ELM thrust allocation method has the same accuracy and greatly improved real-time performance,which has high engineering application value.(3)Aiming at the problem that multi-thruster AUV needs to achieve thrust allocation under multi-mode task.Firstly,the tracking allocation mode and positioning allocation mode were proposed,and the switching index and switching strategy between the two modes were also proposed.Then,aiming at the non-convex optimization problem of thrust allocation for propeller combined rudder thruster,the thrust allocation problem was divided into thrust sub-problems and mathematical models of thrust allocation were established respectively.At the same time,the thrust allocation method of pseudo-inverse model switching and the segmentation strategy of thrust feasible region quadrate method were proposed.Finally,the hybrid thrust allocation strategy was designed by combining pseudo-inverse method,QP method and ELM method,and the adaptive switch between AUV tracking allocation mode and AUV positioning allocation mode was realized through simulation experiments,which proved the correctness,effectiveness and certain real-time performance of the designed algorithm.