The attitude control systems of satellites with rigid and flexible components are demanding more and more better performance resulting in the development of several methods control. For that reason, control design methods presently available, including parameters and states estimation, robust and adaptive control, as well as linear and nonlinear theory, need more investigation to know their capability and limitations. In this paper the investigated technique is H-Infinity method in the performance of the Attitude Control System of a Rigid-Flexible Satellite.

The rapidly complexity increase of systems and processes to be controlled has stimulated the development of sophisticated analysis and design methods called advanced techniques. The H-Infinity

The employment of flexible structures in the spatial area is another problem of control system which has been growing up too. Flexible systems offer several advantages compared with the rigid system. Some advantages are relatively smaller actuators, lower overall mass, faster response, lower energy consumption, in general, and lower cost. With the study of the Attitude Control System (ACS) of space structures with flexible antennas and/or panel and robotic manipulators, one becomes more complex when the dimensions of such structures increase due to necessity to consider a bigger number of vibration modes in its model in order to improve the model fidelity [

In Rigid-Flexible Satellite (RFS) the function of the ACS is to stabilize and orient the satellite during its mission, counteracting external disturbances torques and forces. In this paper is investigated multivariable control method

Figure

Satellite Model.

In the Lagrang approach are considered the equation of motion of the satellite around in

The beam deflection variable

For the complete system, the total kinetic energy

In (

Finally, two equations are obtained. These equations represent the dynamics of rotation motion of the satellite and the elastic displacement of the panels, respectively,

Throughout the decades of 1980 and 1990, H-Infinity control methodhad a significant impact in the development of control systems; nowadays the technique has become fully grown and it is applied on industrial problems [

The

This problem is defined by the configuration of Figure

Generalized Plant.

The project of control system is based given by

(_{2}_{2}, A

_{12}_{21}

[_{2}; C_{1}D_{12}_{12}

[_{1}; C_{2}D_{21}_{21}

The augmented plant is formed by accounting for the weighting functions _{1}, W_{2}_{3},

Plant with weighting functions for

The function cost of mixed sensibility is given for_{1}

The simulations were carried out by computational implementation of the software MatLab. The initials conditions used here are

Parameters.

Parameter | Description | Value |
---|---|---|

_{0} | Moments of inertia of the rigid body of the satellite | 720 Kg^{2} |

_{p} | Moment of inertia of the panel | 40 Kg^{2} |

Constant elastic of the panels | 320 Kg^{2}/s^{2} | |

_{d} | Dissipation constant | 0,48 Kg^{2}/s |

Length of the panel | 2 m | |

Mass of the satellite | 200 kg |

The procedure of the project of _{1}, W_{2}_{3}_{3}

First we analyze the open loop of the system through transmission zeros (TZs) and the close-loop with

Transmission Zeros.

Transmission Zeros | |
---|---|

Open Loop | |

Following, the performances of

Angle and Angular Speed.

Vibration of the Panels.

Both graphs, in Figure

In Figure ^{-7}, in other words, very small. The time of stabilization in the first graph is about 0.5 seconds and for the second one is about 0.45 seconds. This demonstrates that the control H∞ possesses a good performance for angle and angular velocity, as well as to control the vibration of the panels.

The problem of attitude control of satellites is not new and has been addressed by several researchers using many different approaches. The

The authors would like to thank CAPES and INPE/DMC. This work was supported by CAPES thought the Brasil—Portugal Cooperation Project PCT no. 241/09.