%0 Conference Proceedings
%4 dpi.inpe.br/plutao/2011/11.23.16.21.32
%2 dpi.inpe.br/plutao/2011/11.23.16.21.33
%F lattes: 0288494962313241 1 CarraraSiquOliv:2011:SpCuMo
%T Speed and current mode strategy comparison in satellite attitude control with reaction wheels
%D 2011
%A Carrara, Valdemir,
%A Siqueira, Rafael Henrique,
%A Oliveira, Danilo Anderson de,
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@electronicmailaddress val@dem.inpe.br
%@electronicmailaddress rafael_controle_automacao@yahoo.com.br
%@electronicmailaddress danilo_dasors@yahoo.com.br
%B Brazilian Congress of Mechanical Engineering, 21 (COBEM).
%C Natal
%8 24-28 Oct. 2011
%S Proceedings
%K attitude control, reaction wheel, dynamic model compensation control.
%X Within the motto smaller, cheaper and better, several nations can have now easy access to space, both buying or developing their own satellites. In fact, the number of small companies and even universities that make business selling space platforms weighting less than 100 kg, including payload, increases each day. If in the past small satellites mean also low power, low pointing accuracy, low price and therefore low reliability, today it is no longer valid. Some low cost satellites have 3 axis attitude control systems with high degree of pointing accuracy, like FedSat, CHIPSat and MOST. The pointing requirements for MOST (Canadas space telescope) are 25 arc-seconds in the telescope focal plane. The once expensive 3 axis attitude control system, based on gyros, star tracker and reactions wheels is now affordable for micro-satellites, giving both reliability and pointing accuracy for scientific and technological satellites. The attitude and control subsystem (ACS) acts on the reaction wheels in response to attitude errors provided by star tracker and gyros. Reactions wheels are simple brushless DC motor, coupled to a high inertia wheel. They provide torques over wide magnitude range, from micro Newton-meter up to hundreds of mili-Newtonmeter. Normally they are operated in speed control mode in which an internal closed loop control adjusts the motor current in order to achieve a commanded angular rate. Although reaction wheels can also operate in current mode, the non-linear bearing friction, mainly in low speed rates, causes attitude deviation whenever the wheel changes its rotation sense. By the other hand, speed control mode introduces some time lack due to the internal control loop. This work aims to model the non-linear friction of the wheel, and to compensate it in the attitude control loop based in current mode. The reaction wheel and gyro are assembled in a one-axis air-bearing table, which provides micro friction similar to those encountered in space. Furthermore, both control modes, speed and current, shall be compared. The results proved to be helpful in deciding which strategy shall be used in future micro-satellite missions.
%@language en
%3 Carrara_COBEM2011.pdf
%U http://www2.dem.inpe.br/val/publicacoes/Carrara_COBEM2011.pdf
%O Setores de Atividade: Atividades profissionais, científicas e técnicas.