Research On Thrust Allocation Algorithm Of Multi-thruster Marine Vehicle

At present,the status of the ocean in the strategic layout of countries around the world is gradually rising,and the development of advanced marine engineering technology and equipment has become a consensus among countries.As a kind of advanced marine engineering equipment,multi-thruster marine vehicle has high use value under the complicated and changing marine environment conditions.The thrust allocation module is an important part of the motion control of the vehicle.The research on the thrust allocation method is of great theoretical significance and engineering application value for the multi-thruster marine vehicle with overdrive propulsion system.In this dissertation,the following research work is carried out mainly on the thrust allocation optimization algorithm and strategy of the multi-thruster marine vehicle:（1）The multi-thruster marine vehicle has high requirements on the accuracy and real-time performance of the thrust allocation module during mobile operations,and it is expected to reduce the power consumption and mechanical wear of the thruster as much as possible.Aiming at the above thrust allocation problem,this dissertation proposes a variable angle thrust optimization allocation algorithm.By linearizing the objective function and constraints,this algorithm establishes a mathematical model of thrust allocation for convex quadratic programming with the main optimization target of power consumption.The quadratic programming Active-Set algorithm is introduced to optimize the model.In a short period of time,a combination of thrust and angle that meets the requirements of the desired control force and torque is obtained,and the power consumption and mechanical wear of the thruster are low.At the same time,in order to solve the problem of hydrodynamic interference between azimuth thrusters,a forbidden angle thrust allocation strategy was designed.This strategy effectively solves the problem of thrust loss caused by hydrodynamic interference between the thrusters and the problem of reduced thrust utilization rate when the thrusters are in the forbidden angle region for a long time.（2）When a multi-thruster marine vehicle is performing positioning operations under a small external environmental force,due to the thrust dead zone of the thruster and the need to avoid frequent start and stop of the thruster motor,the thruster cannot accurately deliver a small thrust.Aiming at the above-mentioned thrust allocation problem,this dissertation proposes a combined bias thrust optimization allocation algorithm.This algorithm biases the thrusters in groups according to the layout form of the thrusters,and adds adaptive biasing to the thrusters in the group,which effectively solves the problem that the thrusters cannot issue corresponding thrusts due to the small allocated thrust.In addition,considering the mechanical wear of the thruster,an angle truncation thrust allocation strategy was designed.This strategy limits the small angle change of the thruster within the allowable range of the allocation deviation and reduces the mechanical wear of the thruster.（3）The thrust allocation problem that multi-thruster marine vehicle need to solve in different operating modes and external environmental forces is different.Aiming at the problem that the single thrust allocation method cannot solve the thrust allocation in various working conditions,a hybrid thrust allocation strategy is proposed.This strategy divides the thrust allocation mode into a mobile allocation mode and a positioning allocation mode.Different allocation modes use different optimization algorithms to solve the thrust allocation.A suitable switching mechanism is designed for switching between the allocation modes,and a smooth switching between allocation modes is realized.