4798 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 56, NO. 12, DECEMBER 2009 Remote Experiments With Mobile-Robot Hardware via Internet at Limited Link Capacity Florian Zeiger, Marco Schmidt, and Klaus Schilling, Member, IEEE Abstract—Mobile robots provide a motivating basis for hard- ware experiments in kinematics, dynamics, and control topics. A suitable infrastructure is to be established in order to offer a worldwide user community of students’ access to the mobile robots via Internet. Functionalities in the area safety, user-management, hardware interfaces, and constraints related to the available link quality must be taken into account. In this paper, in particular, aspects related to efficient teleoperation of mobile robots despite communication-link constraints are analyzed. Details of the tech- nical implementation of the system architecture are described as well as characteristic performance measurements. Index Terms—Communication constraints, distance learning, hardware experiments, mobile robots, remote laboratory, tele- education, tele-experiments. I. I NTRODUCTION L ABORATORIES are a key aspect in engineering educa- tion, in order to practice theoretical knowledge acquired in lectures also with hardware equipment. In the initial stage of tele-education via TV in the 1960s, there was no way to implement experiments remotely. Therefore, presence phases in specific laboratories had to be organized for the students. The situation only changed during the 1990s when increased capabilities of the Internet enabled access to equipment via the Internet. Nevertheless, challenging implementation problems in the tele-education context had to be solved before com- plete educational units consisting of lectures and experimental components could be realized [1]. While mainly techniques to teleoperate hardware via Internet were investigated in the beginning [2]–[5], as late as after 2000, whole educational units have been developed [6]–[20]. Currently, several systems are operated successfully. Hercog et al. [21] proposed a framework using MATLAB/Simulink and LabVIEW to implement exper- iments in the area of automation and control. In [22], a system for programming robots remotely is presented. Hardware can be programmed to participate in games in order to accomplish an objective in a remote environment. Since the mid-1990s, the authors placed its research focus on tele-experiments with real hardware, addressing particularly mobile robots [23]–[28]. Mobile robots offer a motivating interdisciplinary field, where Manuscript received March 26, 2007; revised July 7, 2009. First published July 28, 2009; current version published November 6, 2009. This work was supported in part by the European Union (EU) under the European Cross Cultural Program with India, by the EU under the EU–U.S. Project IECAT and the EU–Canada Project TEAM, and by the Virtual University of Bavaria. The authors are with the Department of Computer Science VII: Robotics and Telematics, Julius-Maximilians-University Würzburg, 97074 Würzburg, Germany (e-mail: zeiger@informatik.uni-wuerzburg.de). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIE.2009.2027898 theoretical background can be directly transferred to experi- ments with interesting industrial applications [24]. During the last years, several e-learning systems were developed. Usually, these systems use their own content- management system which decreases the level of interoperabil- ity between these systems. The recent research focus in this area is set on using service-oriented architectures in tele-education systems. Several approaches are discussed, like the implemen- tation of architectures based on web services [29], [30] or mul- tiagent approaches in service-oriented architectures [31]. Using service-oriented architectures allows a modularized large-scale interoperability for different kinds of e-learning systems. In addition, incorporating the spirit of the Semantic Web into tele- education systems is investigated, which aims on a seamless semantic understanding of the learning content. Besides these research topics, the presented remote laboratory is focused on providing a manageable number of remote experiments worldwide using real robotics hardware in learning units for en- gineering education. Thus, the communication link must fulfill minimum requirements in order to allow the controlling of the hardware (cf. Section II). Therefore, a classical Server–Client architecture was appropriate to link the robot hardware and the control-client program from the user’s computer. Of course, central services for authentication and hardware reservation are implemented as infrastructure for tele-education. Within the European Cross Cultural Program Project “Inter- national Virtual Laboratory in Mechatronics” in 2005, a world- wide access to hardware-related remote experiments located in Germany, Spain, and India was established and used in classes. The main contribution of this publication is a design for implementing remote experiments for engineering students dealing with real hardware experiments which are accessible from all over the world via the Internet. To allow for a seamless teleoperation of real hardware via the Internet, the effects of technical aspects like bandwidth constraints, end-to-end delays, or round-trip times, as well as aspects of operational security like securing access on the hardware, data management, and hardware security mechanisms have to be considered. This paper presents the design, architecture, and infrastructure of a remote laboratory which provides tele-experiments related to topics of control and kinematics of mobile robots. The focus of this paper is set on the technical implementation aspects of the remotely accessible experiments with respect to the con- straints of the telecommunication link caused by long-distance teleoperations via Internet. Solutions for providing distance- learning units worldwide, as well as results from the operation of the telelaboratory, are presented. This paper is structured as follows. In Section II, the requirements for a worldwide 0278-0046/$26.00 © 2009 IEEE