چكيده به لاتين
Since human access to space in the 1970s, satellites have been expanded with great expense and precision. From the first satellite, Sputnik 1 to the International Space Station, the need for spacecraft and satellites has increased dramatically. In order to meet the multifunctional needs, large satellites have been designed and manufactured with a variety of tools installed. As a result, the use of a large satellite in remote sensing missions, weather surveys, navigation, and communications is common. On the other hand, the cost of designing and developing a large satellite is a critical issue for space agencies and engineers. The construction of large satellites, in addition to the complexity, increases the satellite's instability. A small mistake in designing or constructing may result in a failure of the entire mission. Also, increasing the size of the satellite and the closeness of its orbits will enhance the likelihood of their collisions.
In recent decades, one of the ideas for solving these problems is the replacement of several smaller satellites instead of a large satellite, and because the use of several smaller satellites brings benefits such as higher performance and greater flexibility, most countries have used this idea. On the other hand, this idea reduces the cost of design, construction, and launching significantly.
To fully utilize the benefits of satellite-based technology, a precise control system with reliable performance is needed. In a satellite formation flying, due to the effects of various factors such as parametric uncertainties, orbit disturbances, delay in the system model, and input saturation, they can not maintain their configuration, and the configuration of the space missions change over time.
In this thesis, a robust H∞ state feedback algorithm is developed based on Lyapunov stability theory and Linear Matrix Inequality (LMI) approach for the relative position tracking problem in an elliptical reference orbit by considering input saturation and also input delay. Proposed control law guarantees H∞ performance of the relative motion dynamics in the presence of parameter uncertainties including nonzero eccentricity and varying semi-major axis, input saturation, and disturbances resulted from atmospheric drag and non-spherical mass distribution of the earth. Finally, the results of the numerical simulations demonstrate that proposed controller ensure, global asymptotic in tracking the desired trajectory problem.
