Lss Vibrational/rotational Control By Using Sensors And Actuator Models In The Computer Simulations
- Paper number
IAC-07-C2.3.03
- Author
Dr. Ijar M. Da Fonseca, Instituto Nacional de Pesquisas Espaciais (INPE), Brazil
- Coauthor
Dr. Peter Bainum, Howard University, United States
- Coauthor
Dr. Adenilson da Silva, Brazil
- Year
2007
- Abstract
This paper presents the active control of a LSS vibrational/rotational motion in a low earth orbit (LEO), subjected to the gravity-gradient and the aerodynamics effects. The LSS dynamics is characterized by rigid and flexible motion interaction under the active control and zero-g environment allowing for the control structure interaction (CSI) analysis in addition the attitude and vibrational control performance study. The main features considered for the space environment are the gravity-gradient torque and the aerodynamics effect. Both of those aspects are consistent with the low Earth orbit and the large flight area of the solar arrays assumed for the LSS model. The LSS attitude control system (ACS) includes three reaction wheels and jet gas as actuators. The structural and the control interaction under analysis refers to the solar array vibration excitations when the actuators are turned on (mainly the firing of thrusters) to maneuver and/or to control the LSS station attitude close to the nominal specifications. The assumed mode discretization technique is used for the sake of mathematical modeling of the solar arrays elastic displacement. This technique uses the space dependent functions that must satisfy at least the geometric boundary conditions associated with the on-orbit solar arrays like clamped-free-free-free plates on the main body of the LSS. By the assumed modes technique those functions do not have necessarily to satisfy the differential equation nor the natural boundary conditions. Another modeling aspect of this approach is that the plates are better represented when two functions are chosen to model the elastic displacement. Both functions are associated with free-free and clamped-free beam configurations, respectively. The mathematical model was derived by the Lagrangian formulation for both quasi-coordinates and for generalized coordinates. Mathematical models of the sensors and the actuators are used in control loop simulations to give the study some sense for realistic applications. The attitude dynamics and control has been implemented by using the MatLab®/Simulink software package. The results confirm the active vibrational rotational control strategy assumed for the LSS attitude motion works well, even in the presence of the vibrational motion associated with the solar panels.
- Abstract document
- Manuscript document
IAC-07-C2.3.03.pdf (🔒 authorized access only).
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