Ground and Space Testing of Multiple Spacecraft Control During Close-Proximity Operations

Abstract

A multiple spacecraft close-proximity control algorithm was implemented and tested with the Synchronized Position Hold Engage and Reorient Experimental Satellites (SPHERES) facility onboard the International Space Station (ISS). During flight testing, a chaser satellite successfully approached a virtual target satellite, while avoiding collision with a virtual obstacle satellite. This research contributes to the control of multiple spacecraft for emerging missions, which may require simultaneous gathering, rendezvous, and docking. The unique control algorithm was developed at NPS and integrated onto the MIT SPHERES facility. The control algorithm implemented combines the efficiency of the Linear Quadratic Regulator (LQR), and the robust collision avoidance capability of the Artificial Potential Function method (APF). The LQR control effort serves as the attractive force toward goal positions, while the APF-based repulsive functions provide collision avoidance for both fixed and moving obstacles. The amalgamation of these two control methods into a multiple spacecraft close-proximity control algorithm yielded promising results as demonstrated by simulations performed at NPS. Comprehensive simulation evaluation enabled implementation and testing of the spacecraft control algorithm on the SPHERES facility at MIT. Finally, successful ground testing enabled execution of flight testing onboard the ISS. The NPS's Spacecraft Robotics Laboratory (SRL) and MIT's Space Systems Laboratory (SSL) simulations, the MIT's SSL SPHERES ground testing, and the SPHERES flight testing results are all presented in this paper.

Autonomous Distributed Control of Simultaneous Multiple Spacecraft Proximity Maneuvers

“…In particular, the proposed APF-based collision avoidance relies on both the relative positions and velocities of spacecraft. The merged LQR/APF control algorithm utilizes simple goal commands and obstacle sensory data [20].…”

Flight Testing of Multiple-Spacecraft Control on SPHERES During Close-Proximity Operations

“…A, B, C = state-space matrices a = acceleration due to linear-quadratic-regulator-and artificial-potential-field-determined control effort a APF = acceleration due to artificial-potential-fielddetermined control effort a LQR = acceleration due to linear-quadratic-regulatordetermined control effort a m = maximum acceleration a obs = acceleration of chaser spacecraft toward an obstacle a x;y;z = acceleration due to the control effort T HIS paper presents the simulation, ground verification, and flight-test results of a unique control algorithm for a multiple-spacecraft close-proximity docking experiment [1]. An autonomous distributed spacecraft control algorithm was implemented for a three-satellite test configuration.…”

“…The APF attractive potential development V g is not presented in this paper, because its function is to be replaced by an LQR controller. References [1][2][3] provide a discussion of earlier versions of the algorithm in which APF attractive potential was used.…”

“…The simplicity of the APF-based control algorithms is a good match for spacecraft applications with limited proximity sensors and processing capability. Our research proposed and evaluated a control algorithm that combines the efficiency of a linear quadratic regulator (LQR) with an APF-based collision-avoidance capability [1][2][3][4][5]. The APF-based collision avoidance relies on relative positions and velocities.…”

“…The APF-based collision avoidance relies on relative positions and velocities. The merged LQR/APF control algorithm uses simple goal commands and obstacle sensory data to achieve robust close-proximity performance and establishes a baseline for fuel efficiency while maintaining collision-free maneuvers [1][2][3][4].…”