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Li B.,Tianjin University | Yu R.,Jibei Electrical Power Company Ltd | Li H.,Tianjin University | Li G.,Tianjin University | Wu T.,University of Central Florida
Journal of Aerospace Engineering | Year: 2015

This paper describes a prototype and analytical studies of a three-degree of freedom (3-DOF) spherical momentum exchange actuator for three-axis attitude control. Its moving part, without any gimbal structures cascaded, can be directly driven by a stator electromagnetic field instead of servomotors, which sets it apart from conventional control moment gyros. First, the motion of equation and torque exchange model are developed. Analysis shows that the proposed actuator possesses a considerable torque amplification effect. Then a two-level torque-sharing strategy tailored for this device is presented to decouple the command torque into reaction flywheel/gimbal torque and further assign them to each of the stator coils. The physical limit of the rotor's tilt range is investigated and an n-step incremental Euler eigenaxis rotation is resorted to as the solution. Numerical simulation results present a desirable dynamic response, revealing that the single device has the potential to provide limited three-axis control for spacecraft. Finally, the pros and cons of this device are analyzed. This study may serve as a reference on the design and research of new future momentum exchange devices for spacecraft attitude maneuvers. © 2015 American Society of Civil Engineers.


Bian X.,North China Electrical Power University | Wang Y.,Tsinghua University | Wang L.,Tsinghua University | Guan Z.,Tsinghua University | And 4 more authors.
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2015

This paper presents a research of the surface roughness effects on corona-generated electromagnetic interference of long-term operating conductors. The detailed surface morphologies and roughness of typical long-term operating conductors were measured and analyzed. The radio noise measurement system based on the corona cage was discussed and the actual radio noise generated by the conductor in the measured cage was obtained, based on the parameters of the corona cage and the measured data. The radio noise tests were carried out under both dry and wet conditions. Under two types of conditions, the corona intensity was higher on the long-term operating conductors contrasted to the new conductors as a result of the anomalistic surfaces of the long-term operating conductors. The rate of decrease of corona inception voltages between the long-term operating conductors and new conductors was discovered to increase with the raise of surface roughness degree Ra in linear relationship. Approximate linear relation was also discovered between the averaged radio noise deviation and Ra. The rate of decrease of corona inception voltages under wet conditions was slightly higher (about 1%) than that under dry conditions. The difference between the radio noise of long-term operating conductors and that of new conductors was larger (1.3 dB) under wet conditions compared to dry conditions. © 1994-2012 IEEE.


Bian X.,North China Electrical Power University | Chen L.,Jibei Electrical Power Company Ltd | Zhao X.,Jibei Electrical Power Company Ltd | Chen F.,Jibei Electrical Power Company Ltd | And 3 more authors.
Journal of Electrostatics | Year: 2015

The corona-generated audible noise (AN) and radio noise (RN) of the long-term operating conductors with two bundle types was investigated and compared based on a corona cage measurement system. The surface morphologies of eight conductors were measured and the average surface roughness (Ra) was calculated. With the raise of conductor bundles, the maximum electric field distortion level (β4), the relative difference of ionization intensity (γ4) between long-term operating conductors and new conductors decreased. Adding the number of sub-conductors turned out to be an effective method to improve AN and RN of long-term operating conductors in the contaminated areas. © 2015 Elsevier B.V..

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