This paper focuses on the attitude control prob- lem of small agile satellites using single-gimbal control mo- ment gyros （CMG） and magnetic torquers （MTQ）. CMGs are regarded as effective torque generators for agi...This paper focuses on the attitude control prob- lem of small agile satellites using single-gimbal control mo- ment gyros （CMG） and magnetic torquers （MTQ）. CMGs are regarded as effective torque generators for agile satel- lites because of their torque amplification capability. How- ever, they are vulnerable to failure due to their complex inner mechanism. In this paper, different failure cases of CMGs are analyzed. A flexible failure-tolerant control strategy is developed by automatically redistributing the required con- trol torque among the operating CMGs and MTQs, with a variable limiter to accommodate the actuator dynamics changes introduced by CMG failures. The performances of maneuvers about different directions under different failure cases are also discussed and examined. Numerical simula- tions demonstrate that the proposed strategy maintains cer- tain agility in the cases of one or two CMGs failing. More- over, a survival strategy with only one CMG left is also ver- ified. Both sun-pointing stabilization and earth-pointing sta- bilization can be achieved in this case, which fulfill some basic mission requirements.展开更多
In this paper, the control design problem for linear systems subject to actuator saturations is considered. A fuzzy gain-scheduling output feedback controller is proposed to guarantee the stability of the closed-loop ...In this paper, the control design problem for linear systems subject to actuator saturations is considered. A fuzzy gain-scheduling output feedback controller is proposed to guarantee the stability of the closed-loop system as well as providing disturbance/error attenuation measured in L2 norm. The synthesis condition is cast as a convex optimization problem in terms of linear matrix inequalities (LMIs) and can be solved efficiently. The ball-beam system is used to demonstrate the proposed saturation control approach.展开更多
Theoretical and experimental investigations of heat transfer in flat curvilinear channel have been carried out. Linear and non-linear effects of Dean vortexes on intensity of heat transfer were taken into account. The...Theoretical and experimental investigations of heat transfer in flat curvilinear channel have been carried out. Linear and non-linear effects of Dean vortexes on intensity of heat transfer were taken into account. The linear effect, which describe harmonic (sinuous) variation of the heat transfer coefficient near the concave surface of the channel and the non-linear effect causes the general increase of the heat transfer coefficient due to augmentation of heat transfer engendered by the Dean vortexes. For both effects, mathematical relations were obtained in the form of quadratures. These numerical results were modified to the form convenient in engineering calculations. The investigations have shown that both linear and nonlinear components grow up with the Dean number. Nonlinear component Q0T increases more abruptly, while the linear one Q1T is more conservative. This is a confirmation of stability of vortex structures.展开更多
文摘This paper focuses on the attitude control prob- lem of small agile satellites using single-gimbal control mo- ment gyros （CMG） and magnetic torquers （MTQ）. CMGs are regarded as effective torque generators for agile satel- lites because of their torque amplification capability. How- ever, they are vulnerable to failure due to their complex inner mechanism. In this paper, different failure cases of CMGs are analyzed. A flexible failure-tolerant control strategy is developed by automatically redistributing the required con- trol torque among the operating CMGs and MTQs, with a variable limiter to accommodate the actuator dynamics changes introduced by CMG failures. The performances of maneuvers about different directions under different failure cases are also discussed and examined. Numerical simula- tions demonstrate that the proposed strategy maintains cer- tain agility in the cases of one or two CMGs failing. More- over, a survival strategy with only one CMG left is also ver- ified. Both sun-pointing stabilization and earth-pointing sta- bilization can be achieved in this case, which fulfill some basic mission requirements.
基金Sponsored by the China Postdoctoral Science Foundation (Grant No. 20090460903)Heilongjiang Postdoctoral Science Foundation (Grant No. LRB 08-585)+2 种基金the Fundamental Research Funds for the Central Universities (Grant No. HIT. NSRIF. 2013036)the Innovative Team Program of the NSFC(Grant No. 61021002)the NSF Grant (Grant No. CMMI-0800044)
文摘In this paper, the control design problem for linear systems subject to actuator saturations is considered. A fuzzy gain-scheduling output feedback controller is proposed to guarantee the stability of the closed-loop system as well as providing disturbance/error attenuation measured in L2 norm. The synthesis condition is cast as a convex optimization problem in terms of linear matrix inequalities (LMIs) and can be solved efficiently. The ball-beam system is used to demonstrate the proposed saturation control approach.
文摘Theoretical and experimental investigations of heat transfer in flat curvilinear channel have been carried out. Linear and non-linear effects of Dean vortexes on intensity of heat transfer were taken into account. The linear effect, which describe harmonic (sinuous) variation of the heat transfer coefficient near the concave surface of the channel and the non-linear effect causes the general increase of the heat transfer coefficient due to augmentation of heat transfer engendered by the Dean vortexes. For both effects, mathematical relations were obtained in the form of quadratures. These numerical results were modified to the form convenient in engineering calculations. The investigations have shown that both linear and nonlinear components grow up with the Dean number. Nonlinear component Q0T increases more abruptly, while the linear one Q1T is more conservative. This is a confirmation of stability of vortex structures.
