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.
Highlights
There are several methodologies to investigate the satellite Attitude Control System (ACS) performance and robustness, when the investigation objectives are to validate hardware in the loop equipments experimental procedure can be more appropriate, some applications can be found in [1−3]
This paper presents the DMC 3-D satellite simulator mathematical model and the design of its ACS based on the State-Dependent Riccati Equation (SDRE) method associated with Kalman filter technique
Simulation has shown that the SDRE controller has superior performance than the Linear Quadratic Regulator (LQR) controller for large angle maneuvers when the plant non-linear terns are relevant
Summary
There are several methodologies to investigate the satellite Attitude Control System (ACS) performance and robustness, when the investigation objectives are to validate hardware in the loop equipments experimental procedure can be more appropriate, some applications can be found in [1−3]. A good survey of the SDRE method can be found in [13] and its application to deal with non-liner plant [14], it is considered as the non-linear counterpart of LQR control. It linearizes the plant around the instantaneous point of operation and produces a constant state-space model of the system where a similar LQR control technique can be applied to design a specific controller. In this paper the standard LQR linear controller and the SDRE controller associated with Kalman filter are applied to design a non linear controller for a non-linear plant of the DMC 3-D satellite simulator in the presence of noise. Results have proven the reliability of SDRE method to design control algorithm to be implemented in an on board satellite computer
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