Julian Scharnagl

FORROST: Advances in on-orbit robotic technologies

Orbital robotics is receiving growing attention worldwide for applications in servicing and repositioning of partially or fully defective satellites. In this paper, we present the scope and main results of a four-year research project, which aimed at developing necessary robotic technologies for such applications. The scope is two-fold, since we address both the human-operated robotic operational mode, referred to in robotics as force-feedback teleoperation, as well as the alternative autonomous mode, for the specific task of approaching and grasping a free-tumbling target satellite. We present methodological developments and experimental as well as numerical validations in the fields of tele-communications, computer vision, robot and spacecraft control and system identification. The results of this work constitute important advances in the fundamental building blocks necessary for the orbital applications of interest.

On-line Collision Detection in Space Using Photonic Mixer Devices

Abstract This paper presents a collision detection system especially designed for Rendezvous and Docking (RvD) maneuvers to passive objects in space. It is based on 3D images provided by a Photonic Mixer Device (PMD) and makes use of the output of a pose estimation algorithm developed particularly for this 3D information. The algorithm on-line predicts the trajectory of the observed object and detects possible collisions along this trajectory. The intersection tests performed for that purpose consist of examining multiple oriented bounding boxes that surround target and observer spacecraft. Different scenarios including approaching, departing, rotating and by-passing were conducted in a laboratory setup with two robot manipulators holding a client mockup model and a PMD camera. By the help of these scenarios the functionality of the developed algorithm in common RvD maneuvers was evaluated and confirmed.

Design and Development of a Robotic Teleoperation System using Duplex WebSockets suitable for Variable Bandwidth Networks

Abstract This paper addresses the development of a new teleoperation framework for remote robotics. The status of existing robotic teleoperation systems is introduced, with emphasis on several technological drawbacks and is followed by a description of the design, development and implementation of a new framework based on bleeding edge technologies in internet protocols and software engineering related to robotics. As a first implementation, an update of an existing tele-robotics laboratory is in progress aiming round-the-clock networked access, suited for even the most demanding online learning platforms. A comparison between the current and previous teleoperation system is also published verifying the implemented framework.

Analysis of WebSockets as the New Age Protocol for Remote Robot Tele-operation

Abstract This paper addresses the replacement of acknowledgement based protocols for teleoperation. The initial sections compare the currently used protocols like HTTP and TCP to WebSockets and examine the structural difference of using one over the other, for a real-time teleoperation scenario. A detailed analysis of HTTP and WebSockets is performed using live teleoperation by multiple users performing temporally seperated tests under variably delayed network conditions. The existing teleoperation laboratory at the University of Wuerzburg was used as the test bed to compare these protocols and final teleoperation results in terms of bandwidth, frame-rate, navigation efficiency and situational awareness are presented and discussed.