Master of Science in Electrical Engineering (MSEE)
Electrical and Computer Engineering
First Committee Member
Second Committee Member
Third Committee Member
Fourth Committee Member
Number of Pages
This thesis presents the derivation of both a linear and nonlinear adaptive control law for the attitude states of a spacecraft in orbit around rotating asteroids. The asteroid is assumed to be irregularly shaped and in an elliptical orbit around the sun. The linearized, time-varying spacecraft model will assume to include unknown parameters and will have external disturbances present. The objective is to control the roll, pitch, and yaw angle trajectories of the spacecraft such that they track desired reference trajectories. To achieve this, the control law will be composed of (1) a feedback controller, sufficiently robust to disturbance such that the system is stable, and (2) an adaptation law to estimate unknown parameters. The design of the linear control law will assume that only the angle measurements of the attitude states will be available for feedback. A high-gain observer will then be designed to estimate the higher-order states necessary to synthesis the control law. It will be shown that the tracking error, as well as the observation error, approach zero in finite time within the closed-loop system. The controller is able to accomplish this while being bounded to a saturation limit to reflect genuine thruster constraints. When the nonlinear, time-varying model is considered, unknown parameters are again assumed to be present. To govern the nonlinearities, and uncertainties present in the model, an adaptive control law is designed using the backstepping method. The control law also incorporates an adaption law, derived from an appropriate Lyapunov function. Using state feedback, it can be seen that the tracking error approaches zero while managing the nonlinearities of the model. For the both the linear and nonlinear systems, simulation results present full attitude control of the spacecraft, despite unknown parameters within the model.
adaptive; control; feedback; linear; nonlinear; spacecraft
Aerospace Engineering | Electrical and Computer Engineering
Moya, Nicholas, "Linear and Nonlinear Adaptive Attitude Control of Asteroid-Orbiting Spacecraft Using State Feedback and Output Feedback" (2018). UNLV Theses, Dissertations, Professional Papers, and Capstones. 3296.