dynamics
Masoud Dehnad; Morteza Farhid; Samira Mazhari Anvar
Abstract
In this article, a fault tolerant control based on a virtual actuator is used for the maneuvering of low earth orbit satellites that are subject to the loss of the effectiveness and additive actuator faults as well as natural disturbances such as atmospheric drag, earth's gravity, solar radiation and ...
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In this article, a fault tolerant control based on a virtual actuator is used for the maneuvering of low earth orbit satellites that are subject to the loss of the effectiveness and additive actuator faults as well as natural disturbances such as atmospheric drag, earth's gravity, solar radiation and third body. In the approach used, there is no need for a separate unit to detect, isolate and identify the error. The main feature of this approach is to provide the same performance for the nominal system and the faulty system since the actuator faults and disturbances are hide from the nominal controller due to placing a virtual actuator between the faulty plant and the nominal controller.For the purpose of satellite maneuvering, using Kepler's orbital dynamics, which is affected only by the Earth's gravity, the desired second orbit parameters are calculated. In addition, orbital dynamics based on six modified orbital elements have been used, which avoids singularities. Then, using the desired orbit parameters, the relative motion elements are calculated and used in the control laws. To demonstrate the effectiveness of the control method, a maneuvering scenario of a satellite with Kepler's orbital dynamics that affected by natural disturbances and the actuator faults, is simulated for 42 days. The satellite has an effective cross-sectional area of 0.56 m2, and an actuator fault is occurred since the 32nd day. The results show higher performances the proposed method compared with conventional controllers like LQR.
dynamics
Hossein Maghsoudi Dehaghani; Amirreza Kosari; Mahdi Fakoor; Masoud Khoshsima
Abstract
Due to the unique characteristics of the geostationary orbit and the importance of establishing a satellite in this flying corridor، it is necessary to investigate the effect of environmental disturbances on the orbital elements and to maintain the satellite orbital elements in order to increase the ...
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Due to the unique characteristics of the geostationary orbit and the importance of establishing a satellite in this flying corridor، it is necessary to investigate the effect of environmental disturbances on the orbital elements and to maintain the satellite orbital elements in order to increase the longevity and operation of a satellite in this orbit. A satellite in earth orbit is always exposed to various environmental disturbances such as earth gravity gradient force، gravity of the moon and sun، solar radiation pressure، and so on. For this reason، it is constantly deviating from its original path and needs to study the effect of environmental disturbances on the orbital elements in order to properly correct the disturbed orbital parameters. To achieve the above goals، in this paper، we try to investigate the effect of the environmental perturbations on the orbital characteristics by simulating the satellite translational dynamic behavior in the presence of environmental disturbances. Then، utilizing the genetic algorithm and fuzzy logic approach، an attempt was made to modify the compensation logic of the orbital elements correction، so that، the satellite may be forced to remain in its limited operational orbital window during the mission lifetime. The proposed method could improve the problem-solving operational effectiveness to maintain the position of the satellite with the criterion of minimizing fuel consumption. The case study simulation results may indicate the capability of the proposed approach in satisfying the performance requirements of the satellite station-keeping maneuver
