Sharif Digital Repository

Reference trajectory management is a method to modify reference trajectories for the faulty system. The modified reference trajectories define new maneuvers for the system to retain its pre-fault dynamic performance. Controller reconfiguration is another method to handle faults in the system, for instance by adjusting the controller parameters (coefficients). Both of these two methods have been considered in the literature and are proven to be capable of handling various faults. However, the comparison of these two methods has not been considered sufficiently. In this paper, a controller reconfiguration mechanism and a reference trajectory management are proposed for the spacecraft attitude... 

Attitude Determination (AD) is one of the key requirements of many current and emerging remote sensing missions. As such AD has been traditionally accomplished through a variety of algorithms and measurement models pertinent to sensing mechanisms. The current paper addresses conceptual validation and utility of a novel radiation based heat (measurement) model for space application. The proposed new Heat Attitude (HA) model utilizes temperature data to relate the Satellite Surfaces’ (SS) Net Heat Flux (NHF) to attitude assuming that the satellite navigational data are available. As Sun and the Earth are considered the main external sources of radiation, their effects are modeled for the SS... 

Reducing the burden of the remaining actuators through decreasing the performance gracefully is an important field in active fault tolerant control. According to the literature, two important points have been identified in the works considering graceful performance degradation: 1) using single-objective optimization, 2) assuming an engineering insight into the performance of the faulty system. This paper has two contributions: First, it is shown that in some cases, single-objective optimization may not be able to provide a satisfactory solution for the problem. Second, a new systematic and general method is proposed to remove the need for the engineering insight. The proposed method is based... 

This paper presents a novel heat based measurement model for attitude determination (AD) using temperature data via two filtering techniques. Within the space environment, the Sun and Earth are considered as the major sources of external radiation that affect satellite surface temperature. In order to perform the required AD task, the satellite surface temperatures are related to its attitude via a proposed heat model (HM), assuming that the satellite navigational data is available. The proposed HM relates the net heat flux of three satellite orthogonal surfaces to its attitude. Filtering implementation of the proposed HM using the Unscented Kalman Filter (UKF) for AD is the key contribution... 

This paper presents a method to control a manipulator system grasping a rigid-body payload so that the motion of the combined system as a consequence of external applied forces is the same as any other free-floating rigid-body (with different inertial properties). This allows 0-g emulation of a scaled spacecraft prototype under the test in a 1-g laboratory environment. The controller consisting of motion feedback and force/moment feedback adjusts the motion of the test spacecraft so as to match that of the flight spacecraft, even if the latter has flexible appendages (such as solar panels) and the former is rigid. The stability of the overall system is analytically investigated, and the...