Robust control of flexible structures: theory and experiments

摘要

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.Stringent requirements envisioned for the pointing and shape accuracy of future space missions necessitate advances in the control of large flexible structures. These structures will be extremely flexible, with little natural damping and modes densely packed throughout the frequency domain. Due to their size and complexity, testing of these structures will lead to system models that are inaccurate for control purposes. Therefore, control design methods must be developed to account for model inaccuracies or uncertainties. Such methods should optimize the robustness and performance characteristics of control laws based on the accuracy of the design model.This thesis focuses on incorporating knowledge of the mismatch between the physical system and its mathematical models into the control design process. Control design models are developed to fit into the structured singular value [mu] framework that is used in the analysis and synthesis of control laws. To validate and verify theoretical developments, a flexible structure experiment is developed to investigate large flexible control problems in a laboratory environment. The Caltech experiment has a number of their attributes: closely spaced, lightly damped modes, collocated and noncollocated sensors and actuators combined with numerous modes in the controller crossover (roll off) region.The experimental structure is used to investigate several important issues related to control of flexible structures: tradeoffs between robustness and performance associated with uncertainty modeling for flexible structures, robust control of flexible modes in the controller crossover region and benefits and limitations of collocated versus noncollocated control design. A consistent trend in the results indicates that an accurate description of the flexible structure and model errors is required to synthesize high performance, robust control laws for flexible structures.