Analytical and Experimental Stability Investigation of a Hardware-in-the-Loop Satellite Docking Simulator

The European Proximity Operations Simulator of the DLR-German Aerospace Center is a robotics-based simulator that aims at validating and verifying a satellite docking phase. The generic concept features a robotics tracking system working in closed loop with a force/torque feedback signal. Inherent delays in the tracking system combined with typical high stiffness at contact challenge the stability of the closed-loop system. The proposed concept of operations is hybrid: the feedback signal is a superposition of a measured value and of a virtual value that can be tuned in order to guarantee a desired behavior. This paper is concerned with an analytical study of the system’s closed-loop stability, and with an experimental validation of the hybrid concept of operations in one dimension. The robotics simulator is modeled as a second-order loop-delay system and closed-form expressions for the critical delay and associated frequency are derived as a function of the satellites’ mass and the contact dynamics stiff...