Dynamic modelling and computed torque control of flexible-joint thrust vector control system

Abstract

Thrust Vector Control (TVC) is one means of controlling air vehicles and spacecraft to follow a desired flight path. Of the currently available systems, the Flexible-Joint Thrust Vector Control (FJTVC) is currently the most feasible, especially for space applications. Reasons for this include its longer lifespan, increased energy efficiency, less thrust loss and lower maintanance costs. Often, the dynamics of these systems are modeled using an universal gimbal joint mechanism that neglects uncertainties such as the displacement of the pivot point of the nozzle in the vertical motion. The research reported in this thesis first gives a new approach to the dynamic modelling of FJ-TVC systems that includes one more degree of freedom compared to the conventional models and hence enables the flexible joint structure to move in the vertical direction in addition to the rotational motion of the nozzle in the yaw and pitch-axes. Then the classical control structure is designed and also an alternative that includes Computed Torque Control Law (CTCL) action. It is confirmed, however, that these designs lack robustness even though such a control law gives better performance than the classical control law arrangement. This motivates the last major control law development in this thesis in the form of an H-infinity law with norm bounded model uncertainty where the Monte-Carlo based simulations are used to construct the numerical representation of the uncertainties. Finally, an experimental system is designed, built and used to verify the predicted performance of the designs

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Identifiers

ORCID for Eric Rogers: orcid.org/0000-0003-0179-9398

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