Modeling and Control of Antennas and Telescopes

Mechanical engineering, and engineering discipline born of the needs of the industrial revolution, is once again asked to do its substantial share in the call for industrial renewal. The general call is urgent as we face profound issues of productivity and competitiveness that require engineering solutions, among others. The Mechanical Engineering Series is a series featuring graduate texts and research monographs intended to address the need for information in contemporary areas of mechanical engineering. The series is conceived as a comprehensive one that covers a broad range of c- centrations important to mechanical engineering graduate education and research. We are fortunate to have a distinguished roster of series editors, each an expert in one of the areas of concentration. The names of the series editors are listed on page vi of this volume. The areas of concentration are applied mechanics, biomechanics, computational mechanics, dynamic systems and control, energetics, mechanics of materials, processing, thermal science, and tribology. Preface This book is based on my experience with the control systems of antennas and radiotelescopes. Overwhelmingly, it is based on experience with the NASA Deep Space Network (DSN) antennas. It includes modeling the antennas, developing control algorithms, eld testing, system identi cation, performance evaluation, and 1 troubleshooting. My previous book emphasized the theoretical aspects of antenna control engineering, while this one describes the application part of the antenna control engineering.

Presents design and implementation of the modern modeling and control theories in the antenna and telescope industrial application (e.g., system identification, model reduction, LQG and H_infinity controllers) Shows not only the analysis but the implementation results (all the presented methods have been implemented and are in use at the NASA Deep Space Network antennas) Includes wide use of Matlab and Simulink Shows the improvement of pointing precision of the antennas and telescopes by factor 10, when the presented techniques are applied Presents how to deal with the nonlinear phenomena Covers techniques for the RF beam control (monopulse and conscan) Includes supplementary material: sn.pub/extras

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Modeling and Control of Antennas and Telescopes presents the author's research and field experience in the area of antenna modeling, dynamics, and control. The required spacecraft tracking accuracy of 1 mdeg was the impetus for the new approaches to the antenna controls that use model based controllers (LQG and H¥ ). Consequently, modeling also required a new approach using system identification techniques. Most of the material presented is new in the telescope industry. The methods have been not only analyzed and tested, but actually implemented, giving confidence in the final result, which is significantly increased antenna pointing accuracy.

The author explains two different approaches to telescope modeling: analytical and experimental. The analytical approach combines the structural and drive model, using Matlab and Simulink. The experimental, uses the test data to obtain the equations of the antenna model. Both models are excessively large and the model reduction techniques included make the model size small enough for the controller design purposes. The book also covers the wind models based on the wind tunnel data (steady-state), and on the field data (gusts) since wind gusts are the main antenna disturbance.

The book shows the PI and feedforward controller tuning and their performance as a benchmark for measuring the pointing improvement when the LQG and H¥ are implemented. The properties, performance, and tuning of the LQG and H¥ are also presented. The material explains the nonlinear control issues such as velocity and acceleration limits, friction, and backlash. It also covers RF beam control techniques (scanning and monopulse), and the open loop control of the track level unevenness.

Modeling and Control of Antennas and Telescopes serves as a useful reference for students and engineers in the area of antenna modeling, dynamics, and control.

Inhalt
Modeling.- Analytical Models.- Models from Identification.- Model Reduction.- Wind Disturbance Models.- Control.- Preliminaries to Control.- PI and Feedforward Controllers.- LQG Controller.- H ? Controller.- Single Loop Control.- Non-Linear Control.- RF Beam Control.- Track-Level Compensation.