3,352 research outputs found
Balanced Truncation of Linear Time-Invariant Systems over Finite-frequency Ranges
This paper discusses model order reduction of LTI systems over limited
frequency intervals within the framework of balanced truncation. Two new
\emph{frequency-dependent balanced truncation} methods were developed, one is
\emph{SF-type frequency-dependent balanced truncation} to copy with the cases
that only a single dominating point of the operating frequency interval is
pre-known, the other is \emph{interval-type frequency-dependent balanced
truncation} to deal with the cases that both of the upper and lower bound of
frequency interval are known \emph{a priori}. SF-type error bound and
interval-type error bound are derived for the first time to estimate the
desired approximation error over pre-specified frequency interval. We show that
the new methods generally lead to good in-band approximation performance, at
the same time, provide accurate error bounds under certain conditions. Examples
are included for illustration.Comment: prepared to submit for International Journal of Contro
Optimal Linear Parameter-Varying Control Design for a Pressurized Water Reactors
The applicability of employing parameter-dependent control to a nuclear pressurized water reactor is investigated. The synthesis techque produces a controller which achieves specified performance against the worst-case time variation of a measurable parameter which enters the plant in a linear fractional manner. The plant can thus have widely varying dynamics over the operating range. The results indicate this control technique is comparable to linear control when small operating ranges are considered
Reduced-Order Reference Models for Adaptive Control of Space Structures
In addition to serving as a brief overview of aspects relevant to reduced-order modeling (in particular balanced-state and modal techniques) as applied to structural finite element models, this work produced tools for visualizing the relationship between the modes of a model and the states of its balanced representation.
Specifically, error contour and mean error plots were developed that provide a designer with frequency response information absent from a typical analysis of a balanced model via its Hankel singular values. The plots were then used to analyze the controllability and observability aspects of finite element models of an illustrative system from a modal perspective -- this aided in the identification of computational artifacts in the models and helped predict points at which to halt the truncation of balanced states.
Balanced reduced-order reference models of the illustrative system were implemented as part of a direct adaptive control algorithm to observe the effectiveness of the models. It was learned that the truncation point selected by observing the mean error plot produced the most satisfactory results overall -- the model closely approximated the dominant modes of the system and eliminated the computational artifacts.
The problem of improving the performance of the system was also considered. The truncated balanced model was recast in modal form so that its damping could be increased, and the settling time decreased by about eighty percent
Linear Parameter-Varying Versus Linear Time-Invariant Reduced-Order Controller Design for Turboprop Aircraft Dynamics
The applicability of parameter-varying reduced-order controllers to aircraft models is proposed. A generalization of the balanced singular perturbation method of the linear time-invariant (LTI) system was used to reduce the order of the linear parameter-varying (LPV) system. Based on the reducedorder model, a low-order LPV controller was designed using the H∞ synthesis technique. The performance of the reduced-order controller was examined by applying it to the lateral-directional control of a 20th-order aircraft model. Furthermore, the time responses of the closed-loop system with several reducedorder LPV controllers and a reduced-order LTI controller were compared. The simulation results show that an , 8th -order LPV controller can maintain stability and provide the same level of closed-loop system performance as a full-order LPV controller. This was not the case with the reduced-order LTI controller, which cannot maintain stability and performance for all allowable parameter trajectories
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