Dynamics and control of lattice beams using simplified finite element models
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Simple beam finite element analysis models for a flexible lattice beam with repetitive geometry are developed using the strain and kinetic energies formed by replacing the lattice with an equivalent continuum. This beam element has six degrees of freedom at each of its two nodes. The performance of the simple finite element formulation in free vibration analysis is evaluated by comparison with free vibration results of a full or complex finite element model of the lattice formed by using truss bar elements. Modal Cost Analysis is performed on the modes obtained using both the simple analysis and complex models and the results are compared. Based on this information, model reduction decisions are influenced by the control objectives. A set of reduced order controllers are designed based upon the resulting reduced order models. These controllers are used to control an evaluation model based on the full complex model. For low control energies, these controllers perform well when compared with the optimal controller based on the evaluation model itself. The example analysis shows that the simple finite element analysis models can be used with accuracy in the control law design process for lattice beams with low bandwidth controllers. 1985 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.
