Research On UAV Time Synchronization Method Based On Dual One-Way Ranging Measurement

In recent years,with the development of UAV technology,UAVs have gradually appeared in all aspects of military and civil.When UAVs carry out collaborative operations,electronic reconnaissance,emergency rescue and other tasks,it is necessary to ensure the high-precision time synchronization between UAV terminals,so as to realize the synchronization of position and attitude information Therefore,more accurate time synchronization is of great significance to improve the operational efficiency and stability of the entire UAV swarm network.At present,the main time synchronization method of UAV swarms relies on the installation of satellite chips to directly time UAVs through navigation satellites,but if the UAV cannot receive satellite timing signals in time in case of complex terrain environmental impact or damage to the timing module,the UAV swarm may not be able to complete the set task.This thesis proposes an improved time synchronization method based on DOWR(Dual OneWay Ranging)in view of the high precision requirements of time synchronization in the UAV swarm network,and considering the characteristics of low crystal oscillator stability of slave nodes,and gives the maneuvering situation.And the clock error compensation method under the influence of multipath delay:1.The basic principle and algorithm process of dual one-way ranging measurement time synchronization algorithm to achieve inter-node synchronization are studied,the influence of various error sources that may exist in the synchronization process is analyzed,and the corresponding improvement methods are given.2.The influence of the frequency offset of the crystal oscillator on the accuracy of the synchronization algorithm and the tracking loop is analyzed.Starting from the basic principle and frequency characteristics of crystal oscillator,the influence of temperature and aging factors on the output frequency of crystal oscillator is analyzed,and the influence of crystal oscillator aging on synchronization accuracy under the corresponding exponential aging model is given.At the same time,the effects of crystal frequency offset on receiver acquisition and three common crystal noises on the measurement accuracy of tracking loop are analyzed.3.Aiming at the clock error caused by the frequency offset of the crystal oscillator,an improved time synchronization method is proposed.By sending the tracking message after a fixed period of time when the two nodes send the synchronization message,and by comparing the time difference between the two messages received by the other node with the fixed time,the skew rate of the slave clock oscillator is obtained and the result is Correction is made from the clock count value,and the final clock difference result is smoothed by Kalman smoothing to achieve higher synchronization accuracy.4.Aiming at the synchronization problem in the maneuvering scene of the UAV,the influence of the speed of the two nodes on the synchronization results in four relatively simple motion modes is analyzed,and the analysis equation of the clock error correction is given.Aiming at the problem that there may be strong multipath interference in the application environment,the clock error error under strong multipath interference is compensated by combining the third-party satellite timing data.