Affiliations: National Institute for Space Research- INPE, Brazilian
Aeronautical Company-Embraer, São Jose dos Campos, SP, Brasil
Note: [] Correcponding author: L.C.G. Souza, National Institute for Space
Research-INPE, Brazilian Aeronautical Company-Embraer, São Jose dos
Campos, SP, Brasil. E-mail: gadelha@dem.inpe.br
Abstract: Design of Satellite Attitude Control System (ACS) that involves
plant uncertainties and large angle manoeuvres following a stringent pointing
control, may require new non-linear control techniques in order to have
adequate stability, good performance and robustness. In that context,
experimental validation of new non-linear control techniques through prototypes
is the way to increase confidence in the controller designed. The Space
Mechanics and Control Division (DMC) of INPE is constructing a 3-D simulator to
supply the conditions for implementing and testing satellite ACS hardware and
software. The 3-D simulator can accommodate various satellites components; like
sensors, actuators, computers and its respective interface and electronic.
Depending on the manoeuvre the 3-D simulator plant can be highly non-linear and
if the simulator inertia parameters are not well determined the plant also can
present some kind of uncertainty. As a result, controller designed by linear
control technique can have its performance and robustness degraded, therefore
controllers designed by new non-linear approach must be considered. This paper
presents the application of the State-Dependent Riccati Equation (SDRE) method
in conjunction with Kalman filter technique to design a controller for the DMC
3-D satellite simulator. The SDRE can be considered as the non-linear
counterpart of Linear Quadratic Regulator (LQR) control technique. Initially, a
simple comparison between the LQR and SDRE controller is performed. After that,
practical applications are presented to address problems like presence of noise
in process and measurements and incomplete state information. Kalman filter is
considered as state observer to address these issues. The effects of the plant
non-linearities and noises (uncertainties) are considered in the performance
and robustness of the controller designed by the SDRE and Kalman filter. The
3-D simulator simulink-based model has been developed to perform the
simulations examples to investigate the SDRE controller performance using the
states estimated by the Kalman filter. Simulations have demonstrated the
validity of the proposed approach, once the SDRE controller has presented good
stability margin, great performance and robustness.
Keywords: Satellite simulator, SDRE methodology, robust control
