Vibration control of mechanical systems divided into two types active and passive, this case study illustrates other approach of passive control of the cantilever plate by using double layers of the viscoelastic material (Dyad 606) one in the upper face of the Al substrate (5051) and the second one in the lower face. This layers are affected by axial uniform distributed force by applying tension load, the damping level depend on the value of this axial force where the vertical component of this force consistently the other way of the vibrating element that reduce vibration amplitude in this direction by about (95%) of the original amplitude without damping layers. Computational analysis using ANSYS program are used firstly to verify that the results from the software are compatible with that obtained from analytical and experimental evaluation by comparing the values of natural frequencies. Then using ANSYS model to calculate the reduction occurs in the lateral vibration with changing of the axial loads on the viscoelastic plates. The benefits of this model are enhancing the reliability and reducing the cost.
A new class of structural damping treatments is introduced. This class is the Electromagnetic Compressional Damping Treatment (ECDT) which relies in its operation on a viscoelastic damping layer sandwiched between an electromagnet and a permanent magnet. Interaction between the magnets generates magnetic forces that enhance the compressional damping mechanism of the viscoelastic layer. With proper tuning of the magnetic forces, in response to the structural vibration, undesirable resonances and catastrophic failures can be avoided. The fundamentals and the underlying phenomena associated with the ECDT are investigated theoretically and experimentally.A finite element model is developed to describe the interaction between the dynamics of flexible plates, the visco-elastic damping layer and the electro-magnetic actuators. The validity of the developed finite element model is checked experimentally using aluminum plates treated with single and multi-ECDT patches. The plate/ECDT system is subjected to sinusoidal excitations and its multi-mode response is monitored when the electro-magnetic actuator is activated or not. Several control strategies are considered to activate the electro-magnetic actuator including simple PD controllers. The performance of the uncontrolled and controlled system is determined at various operating conditions. Comparisons with conventional Passive Constrained Layer Damping (PCLD) treatments emphasize the potential of the ECDT treatment as an effective means for controlling structural vibrations.
Today’s Earth Observation Satellites (EOSs) have complicated missions with an agility capability. For this reason, a great importance for satellite mission optimization problem has been arisen. In this paper, a multi-objective equation has been formulated which contains three selected objectives (Gain, image quality and time execution). There are three constraints (Target exclusiveness, due date and transition time) which have been selected and presented by three equations. Satellite Tool Kit (STK) has been used to simulate the relation between satellites and customers’ targets. The output opportunities from STK have been saved in an excel sheet and they will be used as inputs for our problem. Genetic Algorithm (GA) has been used as one of the optimization techniques to solve this problem and it has been applied by using Matlab program and its graphical user interface. The result from solving our problem is a plan which contains selected targets numbers, satellite numbers, target’s gain, shooting time, combined angle, target’s objective function value and the total objective function value. In this paper, a case study has been presented assuming there is a constellation of four (4) satellites (Superview constellation), thirteen (13) random targets and the required output is an optimum daily plan for shooting.
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