ehsan maani miandoab

In all types of satellites, communication systems are utilized for data transmission between satellite and ground stations. pointing the communication antennas to the ground is necessary for the correct mission transmission information. The vibration of the satellite antenna leads to the deform antenna pattern, creating noise and reduction of connection quality. Moreover, working the attitude control actuators near the antenna's natural frequency leads to its resonance and large amplitude vibration in the antenna and satellite structure. Thus it is necessary to identify the satellite antenna dynamic behavior as natural frequency and damping ratio. In this paper the satellite antenna is intended as a smart beam, based on the free vibration of clamped-free beam shape of satellite antenna and sensing its vibration by the piezoelectric sensor, its dynamic characteristic as damping and frequency is identified and verified by comparing the results with experimental ones. The considered mathematical model has very accurate and this model can be used to determine the dynamic behavior of the antenna in different satellite secondary structures.

Vibration control of satellite antenna is the main concern to good quality data transmission and reduction of mechanical disturbance in attitude maneuvers. This paper is devoted to mathematical modeling and vibration control of cube-sat antenna. To do this aim, piezoelectric sensor and actuator are utilized and mathematical model of antenna by considering piezoelectric actuator as input parameter and antenna tip deflection as the output parameter. By performing experimental tests, system unknown parameters as damping ratio and natural frequency are obtained based on FFT analysis and the least square method. To control the antenna vibration, its mathematical model is obtained by considering piezoelectric voltage as an input and antenna tip deflection as an output. Herein, due to limitation on the power subsystem, it is not possible to apply continuous voltages and only 100V voltage is available which complicates the control task. Three different control algorithms are proposed for antenna control and compared together. The results show that the proposed control strategies are efficient and can reduce the control time from 10 to about 1 second. The appearing parameters in the selected control algorithm are optimized using genetic algorithm. The presented results in this paper are useful for the design and control of antenna and also for the accurate design of satellite control subsystem.

In this paper, the dynamic response of resonating nano-beams is investigated using a strain gradient elasticity theory. A nonlinear model is obtained based on the Galerkin decomposition method to find the dynamic response of the investigated beam around its statically deflected position. The mid-plane stretching, axial residual stress and nonlinear interaction due to the electrostatic force on the deflected beam are included in the proposed nonlinear beam model. Comparing the beam natural frequency using strain gradient theory with experimental data shows an excellent agreement among both approaches. The normalized natural frequency is shown to be increasing nonlinearly with the decrease of the applied DC voltage as well as beam thickness. The results also reveal that increasing the tension axial stress increases the natural frequency; however its influence decreases when decreasing the beam thickness. To investigate the effect of AC actuation voltage on the beam resonant frequency, a Lindstedt-Poincare based perturbation method is utilized and validated by comparison with experimental data. The results show that increasing the AC actuation voltage makes the beam stiffer by increasing its resonant frequency.