Study On A Method Of Estimating Maritime Target Trajectory Based On Maritime Satellite Delay And Frequency Offset

When an accident occurs to a ship or an aircraft in the open sea,quickly obtaining the target trajectory can effectively narrow the scope of search and rescue,and then improve the success rate of maritime rescue and reduce the human and material resources in the rescue process.However,due to the inability to set up signal base stations and corresponding positioning equipment on the open sea,it is difficult to obtain the target trajectory information of the accident target.In order to realize the estimation of the trajectory of the sea navigation target,this paper takes the aircraft as an example to study the estimation method of the maritime target trajectory based on the maritime satellite delay and frequency deviation.According to the target tracking theory method,the target motion model is used to predict the position of the target at the next moment,and then the measurement frequency data is used to correct the prediction.In the target trajectory estimation method based on radar and other equipment,due to the uncertainty of the target motion pattern,the Interacting Multiple Model(IMM)is generally used to increase the coverage of target motion mode by combining multiple motion models into a model set.However,unlike traditional angle measurement and ranging methods,maritime satellites are not dedicated monitoring devices.They only have the ability to measure delay and frequency offset.In the case of measurement data with frequency offset and delay,traditional interactive multiple model algorithm is no longer applicable,so the key is to establish a target motion model suitable for measuring data as frequency offset and time delay.To this end,this paper carries out the following research:1)The existing methods of maritime search and rescue trajectory estimation are studied,and the purpose,principle,implementation method,advantages and disadvantages of each method are compared and analyzed.According to the target tracking theory and method,several related target motion models are expounded,the motion characteristics of the distant-sea vehicle are analyzed,and the motorized turning model is determined as the main model of the marine vehicle motion.Then the interactive multi-model algorithm is described.The simulation experiment is carried out in a two-dimensional scene,and the simulation results of the interactive multi-model algorithm under the traditional ranging angle measurement and the range measurement frequency measurement are compared.The simulation results show that the estimated trajectory of the traditional interactive multi-model algorithm is far from the actual trajectory when the measured data is time delay and frequency offset.Therefore,the focus of this paper is to study the target dynamic model for scenarios where the measured values are time delay and frequency offset.2)The maritime satellite frequency offset is the basis for correcting the estimation error.Therefore,the data source and calculation method of the maritime satellite frequency offset are studied firstly.Based on this,the sensitivity of motion parameters of the maritime satellite frequency offset data and the frequency offset data are analyzed.Subsequently,the calculation method of maritime satellite delay is introduced.According to the characteristics that the maritime satellite frequency offset is sensitive to the target velocity direction,a target motion model based on time delay constraint is studied and proposed.The model improves the accuracy of the estimation,and at the same time there will be a mirror position,and then combines the motorized turning model to estimate the turning rate of the target at the estimated approximate position and the mirror position.Since the speed direction of the mirror position and the estimated position are different,the frequency offset can be used to effectively filter out the mirror position.Based on this,the position estimation error of the motion model is analyzed.The innovation of this dynamic model is to combine the existing aircraft motion model and the delay positioning method.By increasing the delay constraint in the motion model,the accuracy of the model estimation is improved,and the target turning rate can be estimated,then the model adaptively match the actual motion pattern of the target.3)Considering that the established model is nonlinear,the principle and method of nonlinear filtering are studied and this paper focus on particle filter theory and resampling principle.On this basis,firstly,in the two-dimensional scene,multiple simulation scenarios are set,and the tracking effect of the interactive multi-model algorithm under the condition of frequency measurement and angle measurement is compared.The feasibility of the model is studied through simulation experiments.4)Using actual marine aircraft flight data and corresponding maritime satellite delay and frequency offset data to verify the feasibility of the model.The results show that the model can estimate the motion trajectory of the flying target,the estimated trajectory is close to the actual trajectory,and it can recognize the turning behavior of the target,but the accuracy of the estimation is limited by the accuracy of the delay measurement data.On this basis,this paper continues to use the satellite simulation software STK developed by US company-AGI to verify the model.This paper uses STK to set up the simulation scene of the distant sea vehicle flying across the ocean,and reads the generated distance and frequency offset data.Then the flight trajectory is estimated by the model.The simulation results show that the estimated trajectory is close to the actual estimate.The maximum latitude and longitude error is close to 1°,and the average latitude and longitude error is 0.2°.Taking the search and rescue of the aircraft in the open sea as an example,this paper studies the target trajectory estimation method based on maritime satellite delay and frequency offset.Through this research,technical support was provided for rescuers to search and rescue targets.In the search and rescue of distant targets,rescuers can estimate the trajectory of the accident target through this method by using delay and frequency offset data of Inmasat,so as to infer the location of the crash,narrow the search and rescue area,reduce the blindness of search and rescue,and reduce the cost of search and rescue.