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Xu B.,Nanjing University | Wang Y.,Shanghai Aerospace System Engineering | Yang X.,National Time Service Center
Neural Processing Letters | Year: 2013

The high precision prediction of atomic clocks on board is a key technology for the long-term autonomous operation of a navigation satellite system. Some researches show that the performance of traditional prediction models of atomic clocks can not meet the requirements of practical applications. In order to improve the atomic clock error prediction accuracy, we propose a model based on functional network in this paper. According to the data characteristics of atomic clocks, the clock error series is firstly fit by polynomial and then the residuals is modeled by functional network. Finally, by using the data of GPS satellites, five independent prediction tests have been done to verify the model. The simulation results show that, compared with the traditional models, the proposed model can fit and predict clock error more effectively. © 2012 Springer Science+Business Media New York.

Xiaotao L.,Shanghai Aerospace System Engineering | Lingbin Z.,Aerospace System Engineering Shanghai | Jie X.,Aerospace System Engineering Shanghai | Zong W.,Aerospace System Engineering Shanghai | And 2 more authors.
Proceedings of the International Astronautical Congress, IAC | Year: 2015

The Chinese government is planning to send a rover to investigate the Mars surface in the near future, and we have been developing and proposing a three-rocker locomotion system with automotive suspension, namely the Tri-Rocker MR-I, which has the predominant characteristics of high packing efficiency, mobility and stability. Tri-Rocker MR-I has three rockers composed of parallel four-bar linkages, which are assembled on the left, right and back sides of the rover body respectively through by elevating screws, and they have both functions of deployment and uplifting. Tri-Rocker MR-I's mechanical design is described, and its suspension and elevating screws' parameters are optimized by considering geometry traffic ability, terrain adaptability, anti-overturn ability et al. A digital model of the location system was created and optimized by numerical simulations of statics, kinetics in the unfolding and locomotion processes. A 300kg, 1.4m∗l.4m∗0.6m prototype was fabricated and tested in the simulated Mars surface field of Shanghai Aerospace System Engineering Institution, and it exhibited fine performances of locomotion system as follows: The ratio of burden to tare is 6.67, packing efficiency is 0.414, the maximum height of surmounting obstacles is 0.5 m, the maximum depth of crossing groove is 0.5 m, the maximum degree of climbing slopes is 30°, the maximum degree of keeping stable on slopes is 45°, the maximum height of uplifting base is 0.55m, et al. © Copyright 2015 by International Astronautical Federation. All rights reserved.

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