A six-degree-of-freedom hardware-in-the-loop simulator for small spacecraft K. Saulnier a , D. Pérez b , R.C. Huang a , D. Gallardo a , G. Tilton a , R. Bevilacqua b,n a Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute (RPI), Troy, NY 12180, USA b Department of Mechanical and Aerospace Engineering, University of Florida (UF), 308 MAE-A Building, P.O. Box 116250, Gainesville, FL 32611-6250, USA article info Article history: Received 26 December 2013 Received in revised form 25 August 2014 Accepted 17 October 2014 Keywords: Small spacecraft Hardware-in-the-loop verification Guidance, navigation and control abstract This paper presents a novel six degree of freedom, ground-based experimental testbed, designed for testing new guidance, navigation, and control algorithms for the relative motion of nano-satellites. The development of innovative guidance, navigation and control methodologies is a necessary step in the advance of autonomous spacecraft. The testbed allows for testing these algorithms in a one-g laboratory environment. The system stands out among the existing experimental platforms because all degrees of freedom of motion are controlled via real thrusters, as it would occur on orbit, with no use of simulated dynamics and servo actuators. The hardware and software components of the testbed are detailed in the paper, as is the motion tracking system used to perform its navigation. A Lyapunov-based strategy for closed loop control is used in hardware-in-the loop experiments to successfully demonstrate the full six-degree-of-freedom system's capabilities. In particular, the test case shows a two-phase regulation experiment, commanding both position and attitude to reach specified final state vectors. & 2014 IAA. Published by Elsevier Ltd. All rights reserved. 1. Introduction The development of innovative guidance, navigation and control (GNC) strategies for relative spacecraft man- euvering will increase the efficiency and autonomy of future space missions [1]. Air bearing-based spacecraft simulators enable validation of GNC strategies prior to launch with hardware in the loop. Air bearings can provide near frictionless rotational and translational motion which can be utilized to create one-g laboratory conditions that are much closer to those encountered in a micro-gravity environment. Reference [2] provides a thorough review of air bearing based testbeds until the year 2003. The same paper also elaborates on how such testbeds have been developed over the last 50 years with the intention of validating GNC strategies for spacecraft, on the ground. A hardware-in-the-loop facility, enabling rapid prototyp- ing of GNC algorithms for experimental testing, dramati- cally reduces the need for lengthy simulations every time (re-)tuning of the algorithms is performed. Ground test- beds can also support the advancement of the Technology Readiness Level (TRL) of spacecraft subsystems (see [3]). Systems classified as only planar or only rotational are still widely used in on-the-ground testing. Examples of these include a rotational testbed at Georgia Tech, which is used for attitude matching experiments, and a planar testbed at Cornell University called FloatCube, which was created specifically for testing maneuvers of small scale cooperative satellites [4,5]. More complex systems combine Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/actaastro Acta Astronautica http://dx.doi.org/10.1016/j.actaastro.2014.10.027 0094-5765/& 2014 IAA. Published by Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ1 352 392 6230. E-mail addresses: kniazx@gmail.com (K. Saulnier), davidperez777@msn.com (D. Pérez), astrorosemary@aol.com (R.C. Huang), daniele.gallardo@yahoo.it (D. Gallardo), tiltogv@gmail.com (G. Tilton), bevilr@ufl.edu (R. Bevilacqua). Acta Astronautica 105 (2014) 444–462