Research On The Time Keeping Method For Motive Application

The mobile time and frequency system is necessary backup and supplement of the ground time and frequency system in the navigation system. It takes on main tasks of providing high precision time and frequency signals replacing the motive ground station in wartime or under special cases so as to meet all kinds of navigation business demands. It has the similar functions to the ground time and frequency system. However, its adverse work environment and small quantities set high demands to time-keeping methods.There are main several aspects need solving as follows: 1. An integrated timescale is the basis to establish the system time for motive application. While the number of clock is small. So study on an integrated timescale algorithm is the first problem need to be settled. 2. The problems of clock's noise, signal frequency or phase jumped and frequency shift are caused by outside the temperature change, vibration and so on. 3. In order to ensure the time-frequency system providing high precision time and frequency signals for motive ground station in the disadvantage conditions of the worse working environment and limited system size. The monitor means of system time for mobile application need to be researched.For the above questions, this paper researches several core technologies of an integrated timescale algorithm, de-noising and singularity detecting measures based on HHT, frequency predicting and main clock monitoring techniques and configuration of time and frequency standard in motive condition. Based on atomic clocks and related time-frequency equipments at the Key Laboratory of Time and Frequency Primary Standards, Chinese Academy of Sciences, a time keeping simulation system of the experiment is established. And methods for producing and keeping the motive time-frequency system time is fufilled. The major contents include:An integrated timescale algorithm for motive time-frequency system is studied. For feature of clock small size in motive time-frequency system, the measures of weight calculation and clock abnormal detection in ALGOS algorithm are improved. The improve ALGOS algorithm which raisesτ≥5d stability of integrated timescale is put forward. In order to remedy a defect of poor short-term stability, a combinative algorithm between improved ALGOS and Kalman is brought upward.Research on the de-noise methods. The space-time filter in HHT is firstly used to solve clock noise caused by bad working conditions.Research on monitoring measures of the system time in motive time and frequency system. A new clock frequency predicting means based on EMD extracting signal tendency is raised. It is more efficient and more accurate than traditional one. The frequency prediction problem is solved. According to characteristics of mobile time-frequency system, the configurationplan of the time-frequency standard is proposed by analyzing clock performance, main and stand-by master clock switching scheme, data acquisition and demands for environment.The time keeping simulation system of the experiment is established. And the automatic monitor software of system is developed. They are used to do automatic monitoring experiments of the system time in different time keeping models. And the results achieve the desired targets.Innovations:In the light of features of motive time-frequency system time, an integrated timescale TAs is calculated with the combinative algorithm between improved ALGOS and Kalman, in which the former restrains the latter's diverge while the latter improves the short-term stability of the former.The time-space filter is based on local character timescale parameter, and don't need specify the centre frequency, bandwidth such parameters. So some artificial factors are avoided. It is firstly used to filter and reduce atomic clock noises. And in terms of the time comparison result's feature, a de-noise means of time-space filter + Vondrak is presented which raises precision of comparison result.The frequency predicting method depends on atomic clock statistical property and valid forecast interval. Whenτ≤10d, the main clock noise is white FM. The function of EMD extracting trend of the signal is used to predict clock frequency. This measure is more accurate than present use.