LSS Vibration Damping by Using Active Control Strategy
- Paper number
IAC-06-C2.3.06
- Author
Dr. Ijar M. Da Fonseca, Instituto Nacional de Pesquisas Espaciais (INPE), Brazil
- Year
2006
- Abstract
This work provides an active strategy for damping vibrations resulting from control structure interaction (CSI). It is assumed that the attitude control subsystem (ACS) takes into account hardware such as thrusters and reaction wheels and operates in low Earth orbit (LEO) for large space structure (LSS) like space stations. Such systems, for example the International Space Station, comprise large and flexible solar arrays as well as long and flexible robotic manipulators. These components are very sensitive to any kind of control actuation on the whole system, mainly those involving pulses. As the thrusters actuate in a short time interval the applied forces are typically impulsive and excite the solar array elastic modes. The damping of the elastic vibration is not a simple problem since interaction between vibration and the station rigid and flexible motions may excite the attitude motion as well as give birth to other phenomena as spillover, for instance. An appropriate strategy to fire the jet gas and to turn it off is necessary any time the thrusters are fired to damp the vibrational motion. In this work the LSS physical model is assumed as a rigid long tubular beam as the main bus with two attached long flexible solar panels. The Lagrange’s formulations for generalized and quasi-coordinates were used to derive the equations of motion. The gravity-gradient, the solar pressure and the drag were included in the mathematical model as external perturbations. The assumed modes discretization method has been used to model the solar array elastic displacements so as to obtain a set of ordinary differential equations to describe the LSS motion. A set of thrusters, providing 3 axis attitude control, is used for large amplitude maneuvers and to damp induced vibration of the elastic components of the LSS and the large reaction wheels are used for fine control. The control strategy is implemented in such a way that automatic switching between actuators is engaged. The torque of the thruster and reaction wheels are combined to deliver a control torque as close as possible to the ideal torque. The thruster control law is a modified bang-bang that takes into account a damping factor. The wheels are commanded by using a typical PID control scheme. In addition, the typical actuator characteristics are taken into account. The MatLab/Simulink platform has been used for the computational simulations. The results show that the approach to damp the LSS vibration caused by the CSI works well. Co-authors: Adenilson R. da Silva National Institute for Space Research - INPE,Brazil E-mail: adsilva@dss.inpe.br Peter M. Bainum Department of Mechanical Engineering Washington, D.C. 20059, USA E-mail: pbainum@fac.howard.edu
- Abstract document
- Manuscript document
IAC-06-C2.3.06.pdf (🔒 authorized access only).
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