The purpose of this work is to present the results of a theoretical and experimental study of a metallic platform designed to support solar cell panels. The main feature of this platform is that it rotates around two orthogonal axis,in order to mantain the panels always normal to the sun rays. A electric motor is used to totate the platform. The electric power cames from the solar cells this implies that the consumption would be as lower as possible. Therefore, the weight would be the most important design criterion. The final result was a very flexible structure in which the dynamic behavior due to the actions of the wind forces for the different positions of the platform were not known and would require a complex analitical treatment to be determined. A modal analysis was carried out to determine the dynamic properties of the structure, i.e. natural frequencies, mode shapes and damping values. For the numerical analysis, the finite element method(FEM) was employed. The experimental analysis was carried out by means of a Free-Vibration Decay Test using a technique called step relaxation, in which a weight is attached to the structure by a wire or rope and then suddenly removed by cutting.
In this work, acceleration measurements were taken by using piezoresistive accelerometers. A total of 700 files of data were acquired by means of two channels. Throughout the tests, one of the accelerometers was kept at the same position and the other was placed in different points depending on the type of the test. The fundamental frequencies were obtained by means of the acceleration spectrums given by FFT (Fast Fourier Transform) analysis. Experimental and theoretical results showed good agreement.
