Fault Tolerant Control of Satellite Orbital Maneuvering Based on Virtual Actuator

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.