Research On Initial Alignment Of Unmanned Ships Under Servere Sea Conditions

As an important premise of navigation and guidance technology,the alignment technology of unmanned boat under severe sea conditions is the key to ensure autonomous navigation and normal operation of unmanned boat under severe sea conditions.In order to solve the problem that autonomous and intelligent unmanned boat systems require robust adaptive adjustment capability in the face of uncertain interference in alignment,this paper studies the alignment technology of unmanned boat under severe sea conditions based on the kinematics characteristics of unmanned boat under severe sea conditions and the motion background of large misalignment angle.In this paper,the initial alignment technology scheme under different sea conditions and complex wave interference is determined to ensure the alignment performance of unmanned boat under severe sea conditions.The main research contents of this paper include the following aspects:1.The kinematics model of unmanned boat under severe sea conditions is studied.The severe sea condition is refined into the influence of severe waves,and multiple simple harmonic waves are superposed to model the severe waves movement.According to the action characteristics of the waves on the unmanned boat and the kinematic characteristics of the unmanned boat,the six-degree-of-freedom motion model of the unmanned boat in the harsh sea waves is simplified,and an intuitive uncoupled four-degree-of-freedom model is established to realize the kinematic modeling of the unmanned boat in harsh sea conditions.2.The nonlinear filtering technology of unmanned boat under pure sway is studied.Considering the compensation of lever arm error,the nonlinear error model of unmanned boat system under large misalignment angle is established.The control variable method is used to determine the effect of misalignment angle and sea state level on the nonlinearity of the unmanned ship system.By comparing the alignment results of EKF and UKF under different misalignment angles and different levels of sea conditions,the range of misalignment angle and the level of sea conditions are quantified.3.The nonlinear filtering technology of unmanned boat under complex disturbance is studied.In order to solve the problem that the variance matrix of measurement noise is not constant with non-Gauss characteristic under the single and short-term strong interference in severe sea conditions,an AdaptiveRobust-UKF(ARUKF)algorithm is established.Aiming at the complex interference including periodic instantaneous impact and paroxysmal short-term strong interference under severe sea conditions,a GeneticUKF(GUKF)algorithm is established to improve the alignment accuracy by using powerful multi-channel adjustment ability.However,the defect of long alignment time caused by slow evaluation speed of genetic algorithm is still unavoidable.In order to balance the relationship between alignment speed and alignment accuracy,an improved UKF algorithm(SUKF)based on SQP optimization is established based on the application of sliding window in ARUKF algorithm and the advantage of multi-channel adjustment in GUKF algorithm.The algorithm improves the alignment speed on the premise of ensuring the alignment accuracy.The effectiveness of the initial alignment scheme and filtering method under different motion backgrounds in this paper are verified by the turntable experiment,unmanned boat lake test and ground start experiment.