Using Capaciflectors for ORU Docking

Abstract

On-orbit servicing of spacecraft‘ will require the changeout of their components in space. These components are usually configured into Orbital Replacement Units (ORUs) so that they can be handled by astronauts performing Extra-Vehicular Activity (EVA). Current research in robotics concerning supplementing or replacing EVA use vision and force feedback. Unfortunately, these sensor modalities do not offer a simple way of sensing proximity and avoiding collisions between the ORU and the environment. We propose to use a capacitive sensor for the detection of proximity of the ORU to objects. This sensor provides position and orientation feedback, which can be useful in the positioning and alignment of the ORU with respect to the docking fixture. In this paper we describe an algorithm that has successfully docked and undocked an ORU in a space allowing less than 1” clearance without touching. The resulting algorithm is simple to implement, has modest computational requirements, and is able to continuously prevent collisions of the ORU with the environment.