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ABSTRACT: Robust control design for complex flexible structures involves many consecutive essential steps. Additionally, many design parameters arise, which turn design optimization into a cumbersome and difficult task. This paper presents a comprehensive robust H-infinity-optimal control design methodology for this class of systems. It relies on a pragmatic approach: The control engineer produces an initial design and reuses it in subsequent design iterations and parameter optimization. The methodology is illustrated by a large transport aircraft model and shows high potential to obtain and tune robust high-performance controllers. Expert knowledge and design decisions are introduced in a natural, clearly structured way, while control engineers are relieved from repetitive design tasks which are safely automated.
Control and Automation, 2010. MED '10. 18th Mediterranean Conference on; 01/2010
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ABSTRACT: Two LQ-based MIMO controllers (LQG and LQIpar architectures) for lateral inner loop flight control for a largepar BlendedWing Body (BWB) passenger aircraft pre-design modelpar are presented. The main control goals are Dutch roll modepar damping, coordinated turn, and roll response shaping. An openpar loop analysis shows that traditional SISO design faces fundamentalpar limitations, so both controller variants are designed aspar MIMO controllers. Their performance is tuned and evaluated,par and their specific properties are discussed and compared. Thepar controllers are validated on various fuel and payload mass casespar and fulfill all demanded goals. Ongoing and future researchpar seeks to reduce structural loads and increase passenger comfortpar using robust control design methods.
2010 IEEE International Conference on Control Applications; Part of 2010 IEEE Multi-Conference on Systems and Control, CFP10CCA-CDR; 01/2010
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ABSTRACT: In this paper a linear parameter-varying (LPV) controller design approach is appliedpar to the longitudinal dynamics of a large blended wing body aircraft. The method is based onpar parameter-dependent Lyapunov functions utilizing the information given by bounds for thepar maximum parameter rate of variation. The entire parameter space is approximated by a setpar of linearized models in trimmed operating points which leads to a finite-dimensional convexpar optimization problem. Typical design goals for flexible aircraft control such as handling qualities,par loads and vibration reduction were considered with the Mach number as scheduling parameter.par The obtained LPV controller is extensively tested, and the obtained results demonstrate thepar high potential of the methodology for flexible aircraft control.
Proceedings of the 18th IFAC Symposium on Automatic Control in Aerospace; 01/2010
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ABSTRACT: The selection of optimal inputs and outputs from larger candidate sets is an important prerequisite for an effective robust control application. This is especially true for active damping of complex and high-dimensional multi-input multi-output systems (MIMO) with flexible modes. Existing optimal selection strategies are based on a single nominal system model and cannot explicitly consider parameterpar variations in the system. Consequently, an optimal selection for the nominal plant may perform poor for a different parameter setting or even render the closed-loop system unstable. The proposed integrated input-output (I/O) selection strategy overcomes this problem by explicitly considering a set of systems covering the range of parameter variation. It is structured in three consecutive selection steps, where only the subset of accepted candidates is fed into the subsequent selection; thus, it is also computationally efficient. An additional advantage is a quantitative ranking of the final candidates, which enables the control engineer to make an optimal I/O choice. The method is illustrated by a flexible beam example as well as a blended wing-body large passenger aircraft model.
Proceedings of the 10th International Conference on Motion and Vibration Control, No. 10-203, Tokyo, Japan; 01/2010
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ABSTRACT: In this paper a robust integrated flight mechanics par and aeroelastics H∞ feedback controller using μ-synthesis for par the longitudinal motion of a large flexible aircraft is presented. par A multitude of design objectives is considered in control design, par with emphasis laid on fulfilling predefined rigid body responses par and manoeuvre demands and achieving gust load alleviation. par A trade-off between these conflicting design goals is obtained par using a two degree of freedom concept. Moreover, an increase par in passenger comfort is achieved by damping of the most par significant aeroelastic modes. For these goals symmetrically par actuated inner ailerons and direct lift control flaps are utilized. par The encountered strong changes of system behavior due to par the considered variations in fuel mass and center of gravity par position is accounted for by an appropriate choice of the par uncertainty model. A possible selection of suitable performance par outputs and their corresponding weighting functions are proposed. par It is shown that the chosen control design structure par allows for a balanced tuning of all design goals of interest. par The obtained controller is numerically validated on several par models, yielding promising performance results especially for par rigid body response and manoeuvre and gust load alleviation.
2009 CACS International Automatic Control Conference; 01/2009
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ABSTRACT: One essential task in control system design is the optimal selection of inputs and outputs (I/O). In this paper a new concept for solving the I/O selection problem is proposed. It is based on normalized comparison of LQG closed loops, which are designed for each potential actuator/sensor separately. The LQG controller is iteratively tuned to obtain a prescribed and fixed value of a suitable system norm quantity. The proposed placement criterion is applied to flexible structures and demonstrated for an academic example and for a largescale blended-wing-body (BWB) passenger aircraft pre-designpar model. Comparison to a state-of-the-art open-loop I/O selectionpar method from literature verifies the proposed approach, but alsopar shows that the closed-loop approach provides additional systempar insight and highly flexible applicability.
Proceedings of the 17th IEEE Mediterranean Conference on Control & Automation; 01/2009
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ABSTRACT: In a comprehensive control design approach for flexible mechanic structures, such as lightweight vehicles or aircraft, a vital decision is the positioning and design of actuators and sensors for the control tasks. This paper proposes an optimal placement approach that exploits the special structure of flexible mechanical systems and incorporates controllability/observability based measures as well as further knowledge on actuator and sensor properties. It combines the advantages of state of the art positioning criteria such that apar balance between low and high frequency modes is assured and at the same time applicability to complex systems in arbitrary system coordinates is guaranteed. These essential properties are illustrated on a clamped beam. The controlled system is studied in terms of the generalized plant description, as it is common in robust control design. Thus it serves as natural extension to the controller design process later on and enables comprehensive control design optimizationpar at an early stage.
IFAC-PapersOnLine; 01/2009
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ABSTRACT: This paper is concerned with the optimal placement of sensors (OSP) on flexible dynamical structures. In order to get as much information as possible about the system state at any given time - also in terms of robustness with respect to numerical issues and modeling errors or sensor noise - the optimal placement of the sensors is an important system design task. Two different approaches for OSP are considered: The first one maximizes the output information using an iterative elimination algorithm, while the second one evaluates the signal output energy that can be received by the sensors. The contribution of this paper is to emphasize the basic mathematical consistency of these two approaches as well as their application on a simple theoretical example.
Proceedings of the 6th Mathmod Vienna 09, No. 35; 01/2009
