As spacecraft rendezvous and proximity operations become more complex, there is a growing demand for more capable and increasingly autonomous on-board guidance, navigation, and control (GNC) algorithms. Debugging and testing these algorithms in space is cost-prohibitive, but the alternative—debugging and testing via desktop simulation—may not account for all the factors that affect real-world performance.
To address this challenge, researchers at the Spacecraft Robotics Laboratory (SRL) within the Department of Mechanical and Aerospace Engineering of the Naval Postgraduate School (NPS) have developed a test bed for verifying dynamic models and GNC algorithms with real-time, rapid control prototyping tests. The test bed is called POSEIDYN—Proximity Operation of Spacecraft: Experimental hardware-In-the-loop DYNamic Simulator—and it has been developed and refined by Dr. Romano and his research team members since 2004. The test bed consists of multiple floating spacecraft simulators (FSS), robotic vehicles that float on a cushion of air over a 4×4 meter granite slab. Each FSS is equipped with an onboard processor, sensors, and actuators that enable it to move with three degrees of freedom across the almost frictionless test bed surface.
Researchers and students at SRL use Model-Based Design with MATLAB® and Simulink® to develop and simulate GNC algorithms before verifying them on the test bed. They then use automatic code generation to implement the algorithms.
“The simulation environment we created with MATLAB and Simulink enables our research team and our students to develop and debug algorithms on any desktop PC and then translate the models to C code to run on the vehicles,” says Dr. Marcello Romano, professor of mechanical and aerospace engineering at the NPS and director/PI of the Spacecraft Robotics Lab. “With Simulink Coder we can transition from running simulations of a guidance algorithm to testing it on hardware in minutes.”