International Scholarly Research Network ISRN Mechanical Engineering Volume 2011, Article ID 213582, 8 pages doi:10.5402/2011/213582 Research Article Neural Networks-Based Identification and Control of a Large Flexible Antenna Minoru Sasaki, 1 Takuya Murase, 1 Yoshihiro Inoue, 2 and Nobuharu Ukita 3 1 Department of Human and Information Systems Engineering, Gifu University, Gifu 501-1193, Japan 2 Department of Mechanical Systems Engineering, Gifu University, Gifu 501-1193, Japan 3 National Astronomical Observatory of Japan, Tokyo 181-0015, Japan Correspondence should be addressed to Takuya Murase, h3132040@guedu.cc.gifu-u.ac.jp Received 21 June 2011; Accepted 8 August 2011 Academic Editor: S. Marchesiello Copyright © 2011 Minoru Sasaki et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper presents identification and control of a 10-m antenna via accelerometers and angle encoder data. Artificial neural networks can be used effectively for the identification and control of nonlinear dynamical system such as a large flexible antenna with a friction drive system. Some identification results are shown and compared with the results of conventional prediction error method. And we use a neural network inverse model to control the large flexible antenna. In the neural network inverse model, a neural network is trained, using supervised learning, to develop an inverse model of the antenna. The network input is the process output, and the network output is the corresponding process input. The control results show the validation of the ANN approach for identification and control of the 10-m flexible antenna. 1. Introduction This paper presents identification and control of a 10-m antenna dynamics using accelerometers and angle encoders data. ALMA—the Atacama large millimeter array—will be a single instrument composed of 64 high-precision antennas located on the Chajnantor plain of the Chilean Andes in the District of San Pedro de Atacama, 16,500 feet (5,000 meters) above sea level (shown in Figure 1). ALMA’s primary function will be to observe and image with unprecedented clarity the enigmatic cold regions of the universe, which are optically dark yet shine brightly in the millimeter portion of the electromagnetic spectrum. The ALMA is an international collaboration between Europe and the North America to build a synthesis radio telescope that will operate at millimeter and submillimeter wavelengths. Japan also becomes a partner, making this a truly global collaboration. Its main targets include planetary system formation and galaxy formation/evolution. The technical challenges to key instruments for such arrays are now performed, that is, developments of high precision antenna, low-noise submilli- meter mixers, high-power submillimeter LO sources, and very high-speed samplers and wideband spectrocorrelators. The specifications imposed for recent submillimeter anten- nas of a 10/12-m size in the open air are demanding and challenging. For example, 12-m antennas for Atacama large millimeter/submillimeter Array (ALMA) have a surface accuracy of better than 25 μm and pointing/tracking accu- racy of better than 0.6” under a wind velocity of 9 m s-1. They must also be able to slew to new position 1.5 degrees away and settle to within 3 arcsec in less than 1.5 sec to cope with phase errors caused by fluctuations in the atmosphere. Loads on antenna structure due to wind cause elastic deformations, which deteriorate antenna’s pointing and surfaces accuracies. The structural behavior of the telescope is typically measured at the encoders of azimuth and elevation axes, while the critical performance is the actual pointing on the sky. We need to make direct measurements of vibration motion of the main-dish and subreflector with a resolution of typically 3–5 μm. Seismic accelerometers serve this purpose for a frequency range from 0.1 to 100 Hz. A laser metrology system can also serve for a frequency range <1 Hz.