Abstract
This work introduces a real time suboptimal control algorithm for six-degree-of-freedom spacecraft maneuvering based on a State-Dependent-Algebraic-Riccati-Equation (SDARE) approach and real-time linearization of the equations of motion. The control strategy is sub-optimal since the gains of the linear quadratic regulator (LQR) are re-computed at each sample time. The cost function of the proposed controller has been compared with the one obtained via a general purpose optimal control software, showing, on average, an increase in control effort of approximately 15%, compensated by real-time implementability. Lastly, the paper presents experimental tests on a hardware-in-the-loop six-degree-of-freedom spacecraft simulator, designed for testing new guidance, navigation, and control algorithms for nano-satellites in a one-g laboratory environment. The tests show the real-time feasibility of the proposed approach.
Highlights
This work introduces a real time suboptimal control algorithm for six-degree-of-freedom spacecraft maneuvering based on a State-Dependent-Algebraic-Riccati-Equation (SDARE) approach and real-time linearization of the equations of motion
The Simulink theoretical controller represents the best alternative: in particular the feedback nature and the higher level of flexibility of the controller allow the use of the sub-optimal solution for real-time implementation; the previous cost analysis ensures that the same sub-optimal controller maintains a high optimization level, since the costs discrepancy is 15%, compensated by implementability with a real spacecraft
Previous works proved the effectiveness and reliability of linear quadratic optimal control, while this research has illustrated a way to quantify the trade-off between realtime feasibility and optimality
Summary
His work consisted of a comparison of spacecraft attitude control methodologies that use reaction wheels for torque actuation and star trackers to infer spacecraft orientation and angular rate Another proof of LQR reliability and effectiveness was given by Walker and Spencer [12]: this work focused on a system for relative navigation and automated proximity operations for a microsatellite using continuous thrust propulsion and low-cost visible and infrared imagers. The previous results obtained in [13] were implemented and verified in [14], where both theoretical developments and experimental validation of the hybrid LQR/ APF were presented In this case propellant consumption was sub-optimized in real-time through re-computation of the LQR at each sample time, while the APF performed collision avoidance and a high level decisional logic.
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