Kamal Jahani; Hossein Farajollahi
Volume 7, Issue 4 , January 2015, , Pages 81-91
Abstract
During launching and deploying to orbit, satellites experience vibration loads from launch vehicle especially in longitudinal direction. Even though the aim of the adapter between satellite and launcher is to isolate the satellite from the launcher's dynamic loads, however, still enough harsh vibration ...
Read More
During launching and deploying to orbit, satellites experience vibration loads from launch vehicle especially in longitudinal direction. Even though the aim of the adapter between satellite and launcher is to isolate the satellite from the launcher's dynamic loads, however, still enough harsh vibration loads that can affect the operation of satellite's delicate systems transmit to the structure of the satellite. Therefore, there is need to isolate the delicate systems from vibrations of the satellite's structure. In this paper, the performance of a new material namely Silicone Gel in isolating delicate equipments (such as electronic board and its components) of satellite from longitudinal vibrations is investigated using finite element method. The results of modeling of an isolator containing Silicone Gel are verified by the available experimental results from the literature. Besides having frequency dependent behavior and dissipation characteristic, Silicone Gel shows hyper-elastic behavior that these characteristic are considered in modeling and analysis. Also an electronic board that overlays on Silicon Gel type mounts is modeled and the amount of transmitted vibration to lead wire of a resistor on it is investigated. The obtained results show that the Silicone Gel has good performance in isolating of delicate equipments of satellite from incoming longitudinal vibrations.Â
M. H. Korayem; M. Nazemizadeh; H. N. Rahimi
Volume 5, Issue 2 , July 2012, , Pages 25-34
Abstract
Flexible manipulators have plentiful applications in Aero-Space fields, due to their less weight and maneuverability. In fact, the ratio of their load carrying capacity to their weight, make them more excellent over their rigid ones. Moreover, these manipulators are known as good candidates in Aero-Space ...
Read More
Flexible manipulators have plentiful applications in Aero-Space fields, due to their less weight and maneuverability. In fact, the ratio of their load carrying capacity to their weight, make them more excellent over their rigid ones. Moreover, these manipulators are known as good candidates in Aero-Space applications because of their less energy consumption, and smaller actuators. In this paper, the dynamic modeling of the flexible manipulators are performed using Finite Element Method (FEM), and optimal control of point-to-point motion of robot is done via optimal control method. To dynamic modeling of flexible manipulator, each link of the robot is divided into sufficient elements, and total displacement of the element is presumed as summation of a rigid displacement and a displacement because of flexibility. By means of Lagrange’s principle, dynamic equations of the flexible robot are derived, and the effect of number of the on dynamic motion of the robot is considered. Also, for the optimal point-to-point motion planning of the elastic manipulator, the nonlinear dynamic equations of the robot is assumed as constraints of optimal control problem, and a proper cost function is defined including torque and speed terms. Then, variation of calculus and Pontryagin’s minimum principle are employed and optimality conditions are resulted in a set of nonlinear differential equations, which is solved numerically. The priority of the optimal control method on the optimal motion planning of the flexible manipulator is discussed, and simulations for a single-link elastic robot illustrate the applicability of the method.
