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Satellite Attitude Determination and Control in Presence of Time Delay

Bahrami, Somayeh | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49274 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Namvar, Mehrzad
  7. Abstract:
  8. Attitude determination and control system (ADCS) design is usually based on using measurements provided by rate gyros or attitude sensors such as Sun, Earth-magnetic, Earthhorizon and star trackers. In many practical scenarios, vector measurements provided by attitude sensors and the corresponding reference vectors are available with time delay while the angular velocity is measured by Gyro without significant delay. Time delay can cause ADCS performance degradation and even instability of the closed-loop system. Due to the nonlinearity of satellite dynamics and kinematics, controller and observer design in presence of measurement delays has its own complexity. Hence, despite its performance-degrading effect, time delay has been widely neglected in the existing attitude control methods.The main objective of this dissertation is to compensate for measurement delays for the attitude tracking problem. Two approaches are presented. In the both, design is based on the Lyapunov–Krasovskii method. In the first approach, a continuous state feedback controller is proposed by assuming that the angular velocity and the delayed attitude measurements are available. In the second one, a continuous estimator is proposed to estimate the attitude and the unknown gyro bias by assuming that measurement of a single vector measurement and the corresponding reference vector are available with time delay. Then the estimates can be used in an appropriate output feedback controller. In the second approach, it is assumed that only one attitude sensor is available. This assumption is motivated by operational limitations of some sensors and limitations in mass and power budget of small satellites. In both methods, convergence is shown to be in global sense. We present realistic simulations to illustrate the performance of the proposed algorithms in the presence of sensors noise
  9. Keywords:
  10. Attitude Estimation ; Attitude Control ; Time Delay ; Lyapunov-Krasovskii Function ; Satellite Control

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