LQR for Free-Floating Robots: Theory and Experiments
In 17th Symposium on Advanced Space Technologies in Robotics and Automation, (ASTRA-2023), 18.10.-20.10.2023, Leiden, ESA, 2023. ESA.
Space robots have been suggested as a prime candidate for On-Orbit Servicing (OOS) and Active Debris Removal (ADR) missions. In this paper, we present the results of employing LQR-based controllers for various free-floating robotic systems. LQR-based controllers have been used frequently as they provide an optimal controller for linear systems. Previous work has shown that the LQR controller for the linearized equations of motion for free-floating robots without gravity is globally asymptotically stable and locally optimal. The linearized equations of motion for 3 different systems are presented along with results from experiments for fixed-point stabilization and trajectory tracking. These systems vary between having continuous actuation using propellers, and binary-pulsed thrusters, along with either a single floating rigid body or a multi-body floating system. LQR controllers allow for trajectory tracking during different phases of OOS or ADR missions. Along with trajectory stabilization, recent works have demonstrated the estimation of the Region of Attraction (RoA) of such controllers for trajectory stabilization. This can be used in the future for sequential controller composition of controllers to guarantee stability through phase transitions. Furthermore, the estimated RoA allows for quick go/no-go decision-making during operations when unaccounted/unmodelled disturbances are observed.
Free-Floating Robotics; Space Robotics; Orbital Robotics; Free-Floating Control; LQR; Experimental Validation