@InProceedings{CarraraSiquOliv:2011:SpCuMo,
               author = "Carrara, Valdemir and Siqueira, Rafael Henrique and Oliveira, 
                         Danilo Anderson de",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)}",
                title = "Speed and current mode strategy comparison in satellite attitude 
                         control with reaction wheels",
            booktitle = "Proceedings...",
                 year = "2011",
         organization = "Brazilian Congress of Mechanical Engineering, 21. (COBEM).",
                 note = "Setores de Atividade: Atividades profissionais, 
                         cient{\'{\i}}ficas e t{\'e}cnicas.",
             keywords = "attitude control, reaction wheel, dynamic model compensation 
                         control.",
             abstract = "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                         low price and therefore low reliability, today it is no longer 
                         valid.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.",
  conference-location = "Natal",
      conference-year = "24-28 Oct. 2011",
                label = "lattes: 0288494962313241 1 CarraraSiquOliv:2011:SpCuMo",
             language = "en",
           targetfile = "Carrara_COBEM2011.pdf",
                  url = "http://www2.dem.inpe.br/val/publicacoes/Carrara_COBEM2011.pdf",
        urlaccessdate = "10 maio 2024"
}